Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–CO2-mixed hydrothermal solutions

COGEL-02400; No of Pages 28 International Journal of Coal Geology xxx (2014) xxx–xxx

Contents lists available at ScienceDirect

International Journal of Coal Geology journal homepage: www.elsevier.com/locate/ijcoalgeo

Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–CO2-mixed hydrothermal solutions Shifeng Dai a,⁎, Peipei Wang a, Colin R. Ward b, Yuegang Tang a, Xiaolin Song c, Jianhua Jiang d, James C. Hower e, Tian Li a, Vladimir V. Seredin f,1, Nicola J. Wagner g, Yaofa Jiang h, Xibo Wang a, Jingjing Liu a a

State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, Beijing 100083, China School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia c Yunnan Institute of Coal Geology Prospection, Kunming 650218, China d The 198 Coal Geology Exploration Group, Kunming 650208, China e University of Kentucky Center for Applied Energy Research, 2540 Research Park Drive, Lexington, KY 40511, United States f Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Staromonetnyi per. 35, Moscow 119017, Russia g Faculty of Science, University of Johannesburg, South Africa h Jiangsu Institute of Architectural Technology, Xuzhou 221116, China b

a r t i c l e

i n f o

Article history: Received 16 October 2014 Received in revised form 13 November 2014 Accepted 14 November 2014 Available online xxxx Keywords: Coal petrology Coal mineralogy Trace elements Lincang Ge ore deposit

a b s t r a c t The Lincang Neogene high-Ge coal deposit in Yunnan, southwestern China, is one of the major coal-hosted Ge deposits in the world. This study reports new data on the petrological, mineralogical, and geochemical compositions of 57 samples (including coal bench samples, roofs, floors, partings, and batholith granite) of three high-Ge coal seams (S3, Z2, and X1) from the Dazhai Mine, Lincang Ge ore deposit, and provides new insights into the origin and modes of occurrence of the minerals and elements present. The coals have huminite random reflectances in the 0.33–0.48% range. On a mineral-free basis, the coal samples are dominated by huminite-group macerals, all having more than 88.5% total huminite. Ulminite and attrinite generally dominate the huminite macerals. Structured inertinite is rare, with funginite being the most abundant inertinite form. The minerals in the coals are mainly composed of quartz, and, to a lesser extent, kaolinite, illite, and mica. A hydrous beryllium sulfate phase (BeSO4·4H2O) is present in the low temperature ashes of several coal samples. Compared to average values for world low-rank coals, beryllium (up to 2000 μg/g and 343 μg/g on average), Ge (up to 2176 μg/g and 1590 μg/g on average), and W (up to 339 μg/g and 170 μg/g on average) are unusually enriched in the Lincang coals, with a concentration coefficient N 100 (CC = ratio of element concentration in investigated coals vs. world low-rank coals); elements As (156 μg/g on average), Sb (38 μg/g), Cs (25.2 μg/g), and U (52.5 μg/g) are significantly enriched (10 b CC b 100); niobium (28.2 μg/g) is enriched (CC = 8.55); zinc, Rb, Y, Cd, Sn, Er, Yb, Lu, Hg, Tl, and Pb are slightly enriched (2 b CC b 5). The biotite- and two-mica granites, which served as both the basement for the coal-bearing sequence and as a source of sediment input, were also either hydrothermally-altered or -argillized. The alteration appears to have taken place during or shortly after deposition of the coal-bearing sequence. Two types of metasomatites of hydrothermal origin, including quartz–carbonate and carbonate, were identified, which occur as partings and as roof and floor strata. These metasomatites were formed at the syngenetic or early diagenetic stages of coal deposition. The rare earth elements in these hydrothermal rocks are characterized by a heavy REE enrichment type and by distinct positive Eu anomalies, compared to the upper continental crust. Hydrothermal solutions have played a significant role in producing the elemental and mineralogical anomalies in the Lincang Ge ore deposit. The hydrothermal solutions leaching the batholith granite were a mixture of alkaline N2-bearing and volcanogenic CO2-bearing fluids, which led to the enrichment of trace elements, not only including assemblages of Ge–W and Be–Nb–U (both leached from granite and the deposited in the peat), but also As–Sb (from volcanogenic solution), as well as the alteration and argillization of the batholith granites, and the formation of carbonate and quartz–carbonate metasomatites. © 2014 Elsevier B.V. All rights reserved.

⁎ Corresponding author at: State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology, D11, Xueyuan Road, Haidian District, Beijing 100083, China. Tel./fax: +86 10 62341868. E-mail address: [email protected] (S. Dai). 1 Deceased.

http://dx.doi.org/10.1016/j.coal.2014.11.006 0166-5162/© 2014 Elsevier B.V. All rights reserved.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

2

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

1. Introduction Germanium can be significantly enriched in coal under specific geological conditions, sometimes reaching concentrations suitable for industrial use (Seredin and Finkelman, 2008). For example, Ge in coals at Lincang, Yunnan, southwestern China (Fig. 1A); Wulantuga, Inner Mongolia, northern China (Fig. 1A); and Spetzugli, Russian Far East, is currently mined and used industrially (Dai et al., 2012a, 2014a; Du et al., 2009; Hu et al., 2006, 2009; Huang et al., 2008; Li et al., 2011; Qi et al., 2004, 2007a,b; Qing, 2001; Seredin, 2003a,b; Seredin and Finkelman, 2008; Wang, 1999; Zhuang et al., 1998a,b, 2006). Studies on Ge in Chinese coals can be traced back to the late 1950s (Dai et al., 2012a). The Lincang Ge ore deposit was discovered during prospecting for coal-hosted uranium at the end of the 1950s. The Wulantuga Ge ore deposit was first reported much later, in 1998, by the Inner Mongolia Institute of Coal Geology Prospection (Wang, 1999). In addition, the Yimin (Inner Mongolia) Ge ore deposit, with an estimated resource of 4000 t Ge, is probably the largest Ge ore deposit in the world (Wu et al., 2002). The Neogene Lincang high-Ge coal deposit, located in the Miocene Bangmai Basin of western Yunnan, southwestern China (Fig. 1B), is worked by the Dazhai Mine, the Meiziqing Mine, and the Chaoxiang pit of the Zhongzhai Mine. The ensured Ge reserves in the Dazhai, Meiziqing, and Zhongzhai Mines are 613 t, 76 t (both as of 31 December, 2009), and 39 t (as of 31 October, 2010), respectively (Dai et al., 2014a). Production at the Lincang Ge recovery plant ranged from 39 to 47.6 t Ge per year (Dai et al., 2014a). Previously reported data show that the concentration of Ge in the deposit is from a few tens of μg/g to ~2500 μg/g, with an average of about 847 and 833 μg/g in the Dazhai and Zhongzhai Mines, respectively (Hu et al., 2009; Qi et al., 2004). The origin and modes of occurrence of Ge in the Lincang coal have been previously described by Zhang et al. (1987a,b), Zhuang et al. (1998a,b), Hu et al. (1996, 1999, 2006), Li et al. (2011), and Qi et al. (2002, 2004, 2011), and it is generally concluded that: (1) The Ge is mainly associated with the organic matter in the coal, and is concentrated at the top and bottom of the Ge-rich coal beds; (2) The Ge-rich coals are also rich in Nb, Li, Sb, W, Bi, and U, and show substantial enrichment of heavy rare earth elements (HREE), which increase together with the Ge; (3) Hydrothermal fluids leached abundant Ge and other elements from Ge-rich granites in the basement; the fluids were then

(A)

discharged into the basin, mainly along fault intersections, depositing Si and Ca to form layer-like siliceous rocks (cherts) and siliceous limestones; and (4) Elevated concentrations of accompanying toxic elements, including As and Sb, were also derived from the granites. However, a number of issues have not been addressed and some points of view concerning trace element origin in the previous studies need further discussion: (1) The petrological and mineralogical compositions in the Lincang Ge-rich coals have not been described in great detail; such information, however, is helpful in understanding the Ge mineralization, and also in providing a better understanding of the Ge behavior during coal combustion and the mode of Ge occurrence in the resulting fly ash (Dai et al., 2014a); (2) Data on the origin and the modes of occurrence of some other trace elements, including Be, B, As, Sb, Cs, and Hg, are not available. These elements may be useful in understanding the sedimentary environment of the Ge-rich coals (e.g., B), while others may have potential economic significance in their own right (e.g., W and Cs). Some elements that are highly enriched in the Ge-rich coals (e.g., Be, As, Hg, Sb) and highly concentrated in the associated fly ash (Dai et al., 2014a) may represent a potential danger to human health (Dai et al., 2012a; Seredin, 2003a); (3) Although the fact that elevated concentrations of Ge were leached from the granite by hydrothermal solutions has been established, the sources and characteristics of those hydrothermal solutions have not been successfully identified. In this paper, we report new data on the maceral composition, and on the abundance and origin of the minerals and elements in the coals; we also discuss the source and characteristics of the hydrothermal solutions that have significantly influenced the mineralogical and geochemical compositions of the Lincang Ge ore deposit. 2. Geological setting The Bangmai Basin, with a surface area of about 16 km2 and filled by the Miocene coal-bearing Bangmai Formation, is an asymmetric halfgraben controlled by NW and EW-trending faults (Fig. 1B). The Bangmai

(B)

Fig. 1. (A) Location of the Lincang (Yunnan, southwestern China), Wulantuga, and Yimin (both Inner Mongolia, northern China) Ge ore deposits; (B) geological setting of the Bangmai Basin. IM, Inner Mongolia; YN, Yunnan province. Modified after Hu et al. (1996).

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Fig. 2. Cross section of the Lincang Ge ore deposit. Data from the Yunnan Nuclear 209 Team, Ren et al. (2006), and Qi et al. (2011).

Formation was deposited on a basement made up of granitic batholiths and can be divided into six zones from bottom to top (N11b to N61b; Fig. 2). 6 The coals are located in zones N21b, N4–5 1b , and N1b. The batholith underlying the Bangmai Basin is of middle Triassic age and is mainly composed of biotite- and two-mica granites. The granitic batholiths have been dated at ~ 212 to 254 Ma using zircon U–Pb geochronology (Zhong, 1998). The batholith, about 350-km long and 15- to 45-km wide, intruded pre-Triassic sedimentary–volcanic rocks. It served as the basement for the coal-bearing sequence (Fig. 2) and is unconformably overlain by the Bangmai Formation (Fig. 2). The upper part of the biotite–granite, distributed to the west of the coal basin (Fig. 1A), also served as a source for sediment input to the basin during coal seam accumulation (Lu et al., 2000; Ren et al., 2006). The lowermost zone N11b was deposited in a range of alluvial environments and is mainly composed of granite-derived clastic rocks (coarse-grained conglomerate, conglomeratic coarse sandstone, and coarse sandstone) interbedded with layers of fine sandstone and siltstone. The overlying sequence, which is divided into five zones, is made up of sandstones, siltstones, conglomerates, coal beds, and diatomites of 6 peat swamp–lacustrine–fluvial origin. Three zones, N21b, N4–5 1b , and N1b, 2 contain lignite. The coal beds in the lowermost zone, N1b, at the Zhongzhai Mine, are interlayered with siliceous rocks (cherts) and limestones (Hu et al., 2009; Qi et al., 2004). The coals of the other two 6 coal-bearing zones (N4–5 1b and N1b) are interlayered with clastic rocks, but siliceous rocks are absent (Hu et al., 2009). A Quaternary sequence with a thickness of 0–10 m, consisting of eluvium, conglomerate, and alluvial materials, disconformably overlies the Bangmai Formation. More geological information on the Bangmai coal basin is provided by Qi et al. (2004), Ren et al. (2006), and Hu et al. (2009). 3. Samples and analytical procedures A total of 57 samples from the Lincang Ge ore deposit were taken at the Dazhai Mine, including 50 bench samples (28 coal bench samples, seven roofs, eight floors, four partings) from the face of the three mined coal seams (lower seam, X1; middle seam, Z2; and upper seam, S3). The bench samples were collected following Chinese Standard

3

Method GB482-1985. Each coal bench sample was cut over an area about 10-cm wide and 10-cm deep. From top to bottom, the bench samples (including coal, roof, partings, and floors) of the three coal seams are identified as S3-1 to S3-11 for S1 seam, Z2-1 to Z2-16 for Z2 seam, and X1-1 to X1-18 for X1 seam. The sample numbers for the partings, roof, and floor materials are identified by suffixes of P, R, and F, respectively. The sample numbers and thicknesses of the coal benches are shown in Table 1. In addition to the coal bench samples, four lump coal samples from the X1 coal seam (Sample nos. 1418-1, -2, -3, and -4) and two granite samples (WG-1, argillized granite and FG-1, unargillized and relatively fresh granite) were collected at the coal mine mouth. One greisenized granite (1104/1), one lump coal sample (Lin-1), and two carbonaceous sandstone samples (CS-1 and Lin-1a) were taken from the outcrop of an abandoned surface mine at the same location. All collected samples were immediately stored in plastic bags to minimize contamination and oxidation. Proximate analysis of the coal samples was conducted following ASTM Standard D3173-11 (2011), ASTM Standard D3175-11 (2011), and ASTM Standard D3174-11 (2011). The total sulfur and forms of sulfur in each coal was determined following ASTM Standard D3177-02 (2002) and ASTM Standard D2492-02 (2002), respectively. An elemental analyzer (Vario MACRO) was used to determine the percentages of C, H, and N in each coal sample. Coal samples were prepared for microscopic analysis in reflected light following ASTM Standard D2797/ D2797M-11a (2011). The classification of macerals used for the study was based on the ICCP System 1994 (ICCP, 2001; Sýkorová et al., 2005) and Taylor et al. (1998). Mean random reflectance of huminite (percent Rr) in coal was determined according to ASTM Standard D2798-11a (2011), using a Leica DM 4500P microscope (at a magnification of 500×) equipped with a Craic QDI 302™ spectrophotometer. The mineralogy was determined by optical microscopic observation and powder X-ray diffraction (XRD). Low-temperature ashing of the coal bench samples, and of some partings with a high loss on ignition (LOI), was performed on an EMITECH K1050X plasma asher. The temperature for low-temperature ashing is lower than 120 °C. XRD analysis of the low-temperature ashes and other non-coal samples was performed on a D/max-2500/PC powder diffractometer with Ni-filtered Cu-Kα radiation and a scintillation detector. The XRD pattern was recorded over a 2θ interval of 2.6−70°, with a step size of 0.01°. X-ray diffractograms of all the samples were subjected to quantitative mineralogical analysis using Siroquant™, commercial interpretation software developed by Taylor (1991) based on the principles for diffractogram profiling set out by Rietveld (1969). Further details describing the use of this technique for coal-related materials are given by Ward et al. (2001), and for high-Ge coals and their combustion products by Dai et al. (2012b, 2014a). Because the XRD analysis identified a hydrous beryllium sulfate (BeSO4·4H2O) in a number of the coal LTA samples, a special .hkl file was prepared using SiPhase™ software and incorporated into the Siroquant database to allow its quantification. A scanning electron microscope (SEM, Hitachi S-3400N) and a field emission-SEM (FEI Quanta™ 650 FEG), both in conjunction with energy dispersive X-ray spectrometers (EDS), were used to study morphology and microstructure, and also to determine the distribution of some elements in the coal and rock samples. Samples were made into pellets, polished, coated with carbon using a Quorum Q150T ES sputtering coater, and then mounted on standard aluminum SEM stubs using sticky electron-conductive carbon tabs. The working distance of the FE-SEM-EDS was 10 mm, beam voltage 20.0 kV, aperture 6, and spot size 5. Images were captured via a backscattered electron detector. Samples were crushed and ground to pass 200 mesh (75 μm) for geochemical analysis. Each coal and non-coal sample was ashed at 815 °C and loss on ignition was calculated. X-ray fluorescence spectrometry (ARL ADVANT'XP +) was used to determine the major element oxides, including SiO2, Al2O3, CaO, K2O, Na2O, Fe2O3, MnO, MgO, TiO2, and P2O5, in each ashed sample. Uniquant (Version 5.46), a “standard-

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

4

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Table 1 Proximate and ultimate analysis (%), forms of sulfur (%), gross calorific values (Q, MJ/kg), and random huminite reflectance (%) of the coals from the Dazhai, Lincang Ge ore deposit. Coal

Sample

Thickness (cm)

Mad

Ad

Vdaf

Hdaf

Cdaf

Ndaf

St,d

Ss,d

Sp,d

So,d

Qgr,ad

Rr

S3

S3-4 S3-5 S3-6 S3-7 S3-8 WA-S3 Z2-2 Z2-3 Z2-7 Z2-8 Z2-9 Z2-10 Z2-12 Z2-13 Z2-14 WA-Z2 X1-4 X1-5 X1-6 X1-7 X1-8 X1-9 X1-10 X1-11 X1-12 X1-13 X1-14 X1-15 WA-X1 1418-1b 1418-2b 1418-4b

15 15 29 4 14 77a 25 10 20 22 17 8.5 13.5 20 20 156a 10 15 3 19 11 28 30 16 22 17 13 1 185a n.d. n.d. n.d.

10.16 11.79 10.55 6.12 9.37 10.27 10.49 7.75 9.20 9.89 11.11 8.53 8.66 8.82 7.89 9.32 10.76 11.56 8.58 15.05 8.35 7.63 11.72 11.50 11.69 8.92 11.22 7.69 10.79 13.70 13.64 14.33

15.35 19.41 25.62 47.96 44.28 26.96 23.76 35.11 20.67 19.03 12.49 36.18 42.20 34.30 42.16 28.18 15.15 20.12 27.85 13.01 31.90 43.98 16.19 15.78 15.08 22.85 11.51 29.4 21.64 7.31 9.77 16.73

42.45 40.61 40.58 48.11 46.43 42.40 42.95 42.53 41.41 41.97 41.66 45.31 42.51 42.19 46.49 42.89 42.61 42.93 44.05 41.96 43.24 42.19 40.56 38.66 39.44 43.29 40.42 42.72 41.42 40.44 41.57 41.78

3.45 4.72 5.91 4.10 4.46 4.84 3.59 4.71 3.66 4.05 4.38 5.31 4.31 4.74 4.50 4.24 3.94 7.70 3.11 4.64 4.19 4.51 7.02 2.91 5.26 4.36 5.46 4.23 5.12 8.26 5.86 3.20

74.01 73.22 70.19 67.63 69.91 71.34 68.62 69.38 72.95 73.72 72.46 72.87 72.86 74.19 72.70 72.20 72.19 70.72 71.04 73.04 70.03 71.88 75.33 73.77 74.13 74.21 74.59 73.03 73.20 79.31 76.12 74.56

2.01 2.16 1.97 2.09 1.51 1.94 2.04 2.24 1.94 2.02 1.87 2.03 1.96 2.00 1.59 1.95 2.09 1.95 2.14 2.02 2.32 1.93 1.52 1.67 1.64 1.80 1.70 2.04 1.83 2.08 1.97 2.17

1.16 1.54 3.89 1.65 1.37 2.33 2.37 2.65 1.39 0.76 2.82 0.62 1.00 0.70 0.59 1.42 3.46 5.44 1.71 2.65 3.00 1.35 0.94 1.22 1.18 0.83 0.91 1.17 1.86 0.93 2.31 1.62

0.05 0.09 0.75 0.28 0.08 0.34 1.25 0.79 0.19 bdl 0.26 bdl 0.10 0.00 bdl 0.31 0.27 0.69 0.20 0.28 0.68 0.24 0.00 0.06 0.04 0.01 bdl 0.03 0.19 bdl 0.30 0.12

0.41 0.82 2.41 0.86 0.75 1.33 0.09 1.06 0.43 0.10 1.94 0.03 0.30 0.13 0.17 0.43 2.43 4.02 0.74 1.42 1.68 0.56 0.11 0.14 0.22 0.02 0.01 0.31 0.86 0.12 0.89 0.50

0.69 0.64 0.73 0.51 0.54 0.66 1.02 0.80 0.78 0.66 0.61 0.60 0.60 0.57 0.41 0.68 0.76 0.74 0.77 0.95 0.65 0.55 0.83 1.02 0.92 0.80 0.90 0.83 0.81 0.81 1.12 1.00

23.38 21.51 19.11 13.79 14.74 19.34 19.08 16.96 21.92 22.32 23.55 17.65 15.97 18.28 15.93 19.40 22.70 20.51 19.50 22.28 18.16 15.59 22.36 22.12 22.56 21.57 24.02 19.74 20.93 nd nd nd

0.33 0.39 0.32 0.33 0.33 0.34 0.35 0.39 0.40 0.36 0.42 0.33 0.39 0.39 0.41 0.38 0.40 0.43 0.43 0.42 0.45 0.48 0.46 0.52 0.49 0.47 0.48 0.45 0.46 nd nd nd

Z2

X1

M, moisture; A, ash yield; V, volatile matter; H, hydrogen; C, carbon; N, nitrogen; St, total sulfur; Ss, sulfate sulfur; Sp, pyritic sulfur; So, organic sulfur; Qgr, gross calorific value (air dry basis); ad, as-air dry basis; d, dry basis; daf, dry and ash-free basis; Rr, random reflectance of huminite; WA, weighted average (weighted by thickness of sample interval); nd, not detected; n.d., no data; bdl; below detection limit. a The total thickness of the coal seam. b Bulk samples from X1 seam.

less” methodology based on a set of fundamental parameters and unique algorithms, was used for matrix correction and calibration of the XRF data. Although Uniquant allows analysis of unknown materials without the need for matching standards or reference materials, data from reference samples (NIST 2689, 2690, and 2691) were also used in the Uniquant data processing. Mercury was determined using a Milestone DMA-80 Hg analyzer. Fluorine was determined by pyrohydrolysis with an ion-selective electrode, following ASTM Standard D5987-96 (2002). Inductively coupled plasma mass spectrometry (X series II ICP-MS), in a pulse counting mode (three points per peak), was used to determine the trace elements, except for Hg and F, in the raw (unashed) samples. For ICP-MS analysis, samples were digested using an UltraClave Microwave High Pressure Reactor (Milestone). Multi-element standards (Inorganic Ventures: CCS-1, CCS-4, CCS-5, and CCS-6) were used for calibration of trace element concentrations. Arsenic and Se were determined by ICP-MS using collision cell technology (CCT) in order to diminish the disturbance of polyatomic ions (Li et al., 2014). For boron determination by ICP-MS, addition of H3PO4 to the HNO3 and HF was used to reduce boron volatilization during the acid-drying process after sample digestion, and 2% ammonia was used as a rinse solution to eliminate the memory effect of boron (Dai et al., 2014c). It should be noted that the digestion procedure for rare earth elements and Y (REY, or REE if Y is not included) was different than that for the other trace elements. The reagents for sample digestion were completely dried on electronic hot plates after microwave digestion, and then the residues were re-digested in 5-ml 65% (v/v) hot HNO3. A three-fold geochemical classification of REY was used in the present study: light (LREY: La, Ce, Pr, Nd, and Sm), medium (MREY: Eu, Gd, Tb, Dy, and Y), and heavy (HREY: Ho, Er, Tm, Yb, and Lu) REY (Seredin

and Dai, 2012). Accordingly, three enrichment types were identified: L-type (light-REY; LaN/LuN N 1), M-type (medium-REY; LaN/SmN b 1, GdN/LuN N 1), and H-type (heavy REY; LaN/LuN b 1) (Seredin and Dai, 2012), in comparison with the upper continental crust (UCC; Taylor and McLennan, 1985).

4. Results 4.1. Coal chemistry and huminite reflectance Table 1 summarizes the proximate and ultimate analyses, forms of sulfur, gross calorific values, and random huminite reflectance data for the coal bench samples of the S3, Z2 and X1 seams from the Dazhai Mine. The S3, Z2, and X1 seams have high moisture contents (averages 10.27%, 9.32%, and 10.79% respectively). The three coals are classed as medium-ash according to Chinese Standard GB 15224.1-2004 (this standard defines coal with ash yield 16.01–29% as medium-ash coal), and are overall medium-sulfur coals (1% b St,d b 3%; Chou, 2012). The sulfur is mainly in organic form in the low-sulfur (St,d b 1%) and some medium-sulfur coal benches (e.g., samples Z2-7, Z2-12, X1-11, X1-12, and X1-15); however, pyritic sulfur is dominant in the high-sulfur (St,d N 3%) and a few medium-sulfur coal benches (e.g., Z2-9 and X1-7). In the other medium-sulfur coal benches, the sulfur is evenly distributed between organic and pyritic sulfur forms. Sulfate sulfur is dominant in sample Z2-2. The data for volatile matter, gross calorific value, and random huminite reflectance indicate that the coals are of lignite/subbituminous rank (with reflectances in the 0.33–0.48% Rr range; Table 1) according to the ASTM classification (ASTM Standard D388-12, 2012).

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

Coal

Sample

Tex

Ulm

TeloH

Att

Den

DetroH

CorpH

Gel

GeloH

T-Hum

Fu

Sf

Mic

Mac

Sec

Fun

Iner

T-Iner

Spor

Cut

Res

Lipde

Sub

Exs

T-Lip

S3

S3-4 S3-5 S3-6 S3-7 S3-8 WA-S3 Z2-2 Z2-3 Z2-7 Z2-8 Z2-9 Z2-10 Z2-12 Z2-13 Z2-14 WA-Z2 X1-4 X1-5 X1-6 X1-7 X1-8 X1-9 X1-10 X1-11 X1-12 X1-13 X1-14 X1-15 WA-X1

21.4 11.5 19.7 14 16.2 17.5 18.9 21.6 2.9 3.3 2.6 2.8 1.8 6 2.3 6.9 8.7 8.9 3.8 5.9 3.7 21 3.8 13.4 15.3 14.6 6 10.7 10.7

55.3 51 53.2 36 57.3 53.0 44.3 25.2 47.4 38.5 67.7 52.8 52 49.7 45 47.1 55.3 39.7 46 49.2 60.2 66 49 46.5 37.7 34.1 52.6 51.4 49.1

76.7 62.5 73 50 73.4 70.6 63.2 46.8 50.3 41.8 70.3 55.7 53.8 55.7 47.4 54 64 48.6 49.8 55.1 63.9 87 52.8 59.9 53 48.8 58.6 62.1 59.8

21.4 34 21.4 32 19.1 24.0 26.2 47.5 36.7 48.4 23.9 34 33.9 23.9 46.2 35.2 15.4 45.7 38.8 23.2 26.4 9 36.9 29.9 36.7 37.6 26.7 29.4 28.9

0 0 0 0 0 0 1 3.2 1.3 0 0.2 0 0.6 0 0.6 0.7 0 0 0 0 0 0 0.3 0 0 0 0 0 0

21.4 34 21.4 32 19.1 24.0 27.1 50.7 38 48.4 24.1 34 34.5 23.9 46.8 35.8 15.4 45.7 38.8 23.2 26.4 9 37.1 29.9 36.7 37.6 26.7 29.4 28.9

0.9 0.5 0.6 8 0 0.9 1.5 0 0.3 1.6 0 1.9 0.6 13.2 0.6 2.4 15.1 2.6 3.8 16.1 1.4 2 4.3 2.7 2.8 4.4 8.2 6.2 5.4

0.5 0 0 2 0.4 0.3 0.5 0 0 0 0 0 0 0 0 0.1 0 0 0 0 0 0 0 0 0 1 0 0.2 0.1

1.4 0.5 0.6 10 0.4 1.2 1.9 0 0.3 1.6 0 1.9 0.6 13.2 0.6 2.5 15.1 2.6 3.8 16.1 1.4 2 4.3 2.7 2.8 5.4 8.2 6.5 5.5

99.5 97 94.9 92 92.9 95.7 92.3 97.5 88.5 91.8 94.4 91.5 88.9 92.8 94.7 92.3 94.5 96.9 92.3 94.3 91.7 98 94.2 92.5 92.6 91.7 93.5 98 94.2

0.5 0 0 0 0 0.1 0.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.5 0 0 0

0 0 0 0 0 0 1.9 0 4.7 0.8 0.6 2.8 7 0.6 1.2 2.1 0.9 1 3 0.7 1.4 0 0 0.5 0 0 0 0 0.4

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.5 0 0 0 0 0 0 0 0

0 0.5 0.3 4 0.4 0.5 0 0 0 0 0.6 0 0 0 1.2 0.2 0 0 0 0 0 0 0.3 0 0.5 1.5 0 0.2 0.2

0 0 0.3 0 0 0.1 0 0 0.3 0 0.2 0.9 0 0 0 0.1 0 0 0 0 0 0 0 0 0 0.5 0 0 0

0 2.5 3.1 4 2.5 2.3 1.2 1.8 3.4 0.8 0.6 3.3 0 2.3 1.8 1.6 2.3 1 3.3 3.8 2.8 0 1.8 6.4 6 3.4 4.3 0.7 3.0

0 0 0.6 0 0 0.2 0 0 0 0 0.2 0 0 0 0 0 0.7 0.2 0 0 0 0 0 0 0 0 0 0 0.1

0.5 3 4.2 8 2.9 3.2 3.4 1.8 8.3 1.6 2.4 7.1 7 2.9 4.1 4.1 3.9 2.2 6.3 4.5 4.6 0 2 7 6.5 5.9 4.3 0.9 3.8

0 0 0.6 Tr 1.2 0.4 0 0 0.8 0 0.2 0 0.6 0 0 0.2 0.2 0.5 0 0 0.9 1 1.3 0 0 0.5 0.4 0 0.5

0 0 0 0 2.1 0.4 0 0 0 0 1.9 0 0 0 0 0.2 0.7 0 0.5 0.7 0.5 0 0.5 0.5 0 0.5 0.4 0.4 0.3

0 0 0.3 0 0.4 0.2 0.2 0 0 0 0.2 0.5 1.2 0.3 1.2 0.4 Tr 0.2 0.5 0.5 0.9 1 0 0 0.5 0.5 0.9 0.7 0.5

0 0 0 0 0.4 0.1 1.7 0.4 2.1 5.7 0.2 0.5 1.8 0 0 1.6 0 0 0.3 0 0.5 0 0.8 0 0 1 0.4 0 0.3

0 0 0 0 0 0 0 0 0 0.8 0 0 0 2.6 0 0.4 0 0 0 0 0 0 1.3 0 0.5 0 0 0 0.3

0 0 0 0 0 0 2.4 0.4 0.3 0 0.6 0.5 0.6 1.4 0 0.8 0.7 0.2 0.3 0 0.9 0 0 0 0 0 0 0 0.1

0 0 0.8 0 4.1 1.0 4.4 0.7 3.1 6.6 3.2 1.4 4.1 4.3 1.2 3.6 1.6 1 1.5 1.2 3.7 2 3.8 0.5 0.9 2.4 2.2 1.1 2.0

Z2

X1

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

Table 2 Maceral contents determined under optical microscope for coals from the Lincang Ge ore deposit (vol.%; on mineral-free basis).

Tex, textinite; Ulm, ulminite; TeloH, telohuminite; Att, attrinite; Den, densinite; DetroH, detrohuminite; CorpH, Corpohuminite; Gel, gelinite; GeloH, gelohuminite; T-Hum, total huminite; Fu, fusinite, Sf, semifusinite; Mic, micrinite; Mac, macrinite; Sec, secretinite; Fun, funginite; Iner, inertodetrinite; T-Iner, total inertinite; Spor, sporinite; Cut, cutinite; Res, resinite; Lipde, liptodetrinite; Sub, suberinite; Exs, exsudatinite; T-Lip, total liptinite; WA, weighted average based on thickness of sample interval; Tr, trace.

5

6

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Fig. 3. Huminite macerals and funginite in the Lincang coal (white-light illumination). (A) Ulminite (u) and textinite (t) in sample S3-6. (B) Cross section through root with ulminite (u) and textinite (t)/corpohuminite (ch) in sample Z2-2. (C) Corpohuminite/corpogelinite (cg) with fungal sclerotia (fs) on left, sample Z2-6. (D) Fungal sclerotia with fungal spore on upper left side of sclerotia, sample X1-12. (E) Fungal sclerotia and hyphae in sample X1-14. (F) Fungal sclerotia and hyphae in sample Z2-13. Scale bar for A, E, and F is 25 μm, and for B, C, and D is 50 μm.

The huminite reflectance increases slightly from the S3 seam (0.34%), through the Z2 seam (0.38%), to the X1 seam (0.46%). All of the three coal-hosted high-Ge ore deposits that are currently being mined have a low rank and low calorific values. For example, Rr = 0.45% for the Wulantuga coal (Dai et al., 2012b) and 0.39% for the Spetzugli coal (Medvedev et al., 1997); calorific values are 21.7 MJ/kg and 27.8 MJ/kg (air-dry basis) for the Wulantuga (Dai et al., 2012b) and Spetzugli coals (Medvedev et al., 1997), respectively. 4.2. Coal petrology A number of studies (Nandi et al., 1977; Shibaoka, 1985; Vleeskens et al., 1993) have shown that inertinite- and vitrinite-group macerals differ in resistance to combustion. Inertinite, primarily the higher reflecting forms, fusinite and secretinite, but also including other inertinite macerals, is more resistant to combustion than the vitrinite-

group macerals, especially in pulverized fuel combustion systems. The inertinite-rich Ge-bearing coal would be expected to yield high unburnt carbon in the Ge-rich fly ash (Dai et al., 2014a). The coals are lignite/subbituminous in rank, with some textural transitions to high volatile A bituminous. Maceral contents determined under the optical microscope are listed in Table 2. On a mineral-free basis, the coal samples are dominated by huminite-group macerals, with no coal benches having less than 88.5% total huminite (sample Z2-7) (Table 2). Ulminite and attrinite generally dominate the huminite macerals; examples of huminite forms are illustrated in Fig. 3A and B. With a few exceptions (Z2-7, Z2-12), structured inertinite is rare. Funginite (Fig. 3C–F) is the most abundant inertinite form, and is present throughout most benches of the three coal seams. Liptinite is absent in some of the coal benches, and where present contains varying proportions of sporinite (Fig. 4A, B), cutinite (Fig. 4C–E), resinite (Fig. 5A, B), exsudatinite (Fig. 5C–E), and suberinite. Liptodetrinite is

Fig. 4. Sporinite and cutinite in the Lincang coal. (A) and (B), Blue-light excitation (upper-left) and white-light illumination of sporinite (s), respectively, sample X1-13. (C), Cutinite (c) with resinite (r) in sample Z2-8, blue-light excitation. (D), Planar view of cutinite (c) in sample Z2-9, blue-light excitation. (E), Cutinite (c) in sample X1-13, white-light illumination. Scale bar for A, B, and E, is 25 μm; and for C and D is 50 μm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

7

Fig. 5. Resinite and exsudatinite in the Lincang coal. (A) and (B), Blue-light excitation and white-light illumination of resinite (r) for the same observation field in sample S3-6. (C) and (D), Blue-light excitation and white-light illumination of exsudatinite (e) in sample Z2-13. (E), White-light illumination of exsudatinite (e) in sample X1-13. Scale bar for A, B, and E, is 25 μm; and for C and D is 50 μm. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

present, particularly in portions of the Z2 series, as a cannel-like groundmass. As with the Lincang coals, huminite is the dominant maceral group in the Ge-rich Spetzugli coals (80–90 vol.%; Dai et al., 2014a); however, the inertinite-group macerals dominate in the Wulantuga coals (52.5 vol.% on average; Dai et al., 2012b). Due to the abundance of huminite-group macerals, the fly ashes derived from the Lincang and Spetzugli coals have lower loss-on-ignition percentages (16.3% and 15.4%, respectively; Dai et al., 2014a) than those from the Wulantuga deposit (57.7%, Dai et al., 2014a).

4.3. Mineralogy and geochemistry Table 3 lists the mineralogical compositions of the coal LTAs, partings, and host rocks (roof and floor strata of the coal seams) as determined by XRD and Siroquant. The partitioning between illite and mica in the XRD patterns is difficult to evaluate in some cases, primarily due to preferred orientation effects, and the percentages of these two phases have therefore been grouped as “illite + mica” in Table 3. Tables 5 and 6 show the concentrations of major-element oxides and trace elements (including rare earth elements) in the samples, as well as comparisons between the coal samples of the present study and averages for Chinese coals or world low-rank coals, respectively reported by Dai et al. (2012a) and Ketris and Yudovich (2009).

4.3.1. Comparison between mineralogical and chemical compositions The chemical composition of the (high-temperature) coal ash expected to be derived from the mineral assemblage indicated by the Siroquant analysis of each LTA, parting, roof and floor sample was calculated (on a SO3-free basis; see Supplementary Electronic File), using methodology described by Ward et al. (1999). This process includes calculations to allow for the loss of hydroxyl water from the clay minerals and CO2 from the carbonates at the temperatures associated with hightemperature (815 °C) ashing and combustion processes. The inferred and observed chemical analysis data (Table 4) for the samples were both recalculated to provide normalized percentages of the major element oxides in the inorganic fraction of each sample (see Supplementary Electronic File). The percentages of SiO2, Al2O3, K2O, CaO, and Fe2O3 indicated by both sets of data were plotted against each other (Fig. 6), to provide a basis for comparing the XRD results to the chemical analysis data for the same coal, parting, and host rock samples. As discussed for other materials by Ward et al. (1999, 2001), the respective data sets are presented as X–Y plots, with a diagonal line on each plot indicating where the points would fall if the estimates from the two different techniques were equal. For each major-element oxide, the points fall very close to the equality line, suggesting that the percentages of the various minerals indicated by the XRD analysis are consistent with the independently-determined chemical data. Peaks identified as a hydrous beryllium sulfate (BeSO4·4H2O) are present in a number of the coal LTA samples. Where it is identified,

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

8

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Table 3 LTA yields of coal samples and mineral compositions (%) of coal LTAs, partings, roofs, floors, and granites determined by XRD and Siroquant. Sample

LTA

Quartz Kaolinite

Illte+Mica

I/S

Sme

Chl

K–Feldspar

S3–1R

67.4

8.5

15.4

S3–2R

35.4

33.4

25.8

Trace

5.4

S3–3R

42.9

23.2

24.4

2.9

6.6

Albite

Pyrite

S3–4

17.21

54.9

16.4

10.6

5.2

3.4

S3–5

19.37

43.1

25.1

15.6

4.2

7.7

S3–6

30.06

30.8

28.0

20.6

S3–7

55.01

36.0

44.2

15

45.3

40.4

10.1

4.2

40.8

36.5

18.4

1.9

S3–10F

62.8

11.6

15.6

S3–11F

51.1

16.2

17.4

Z2–1R

60.0

10.0

16

1.6

a

55.25

96.0

1.3

0.3

Z2–5LP

56.58

93.8

1.5

0.8

48.0

11.8

17.1

0.2

a

16.4

22.18

69.2

7.0

7.9

2.7

5.1

19.34

69.1

11.7

3.2

3.3

5.6

Z2–9

14.20

42.2

14.3

6.4

Z2–10

36.70

40.5

25.1

29.1

29.2

10.5

Z2–12

41.14

83.3

8.6

4.1

Z2–13

32.43

84.7

6.3

1.1

Z2–14

44.19

63.0

12.0

7.7

0.2

3.6

1.0

1.4

1.2

1.0

2.1

23.8 4.5 7.4

3.4 4.6

1.0

2.5

0.2

2.5

3.7

2.2

3.8

0.7

6.1 2.0 6.4

0.5

1.0

0.5 0.7

11.1

5.5

66.2

a

2.2

4.5

53.5

0.3

92.2

1.1

93.2

1.0

83.4

0.5

34.1

19.0

13

4.2

21.7

X1–5

25.31

24.7

19.8

14.9

4.2

32.3

X1–6

32.15

35.0

40.2

13.7

3.2

5.6

0.5

X1–7

12.84

39.4

14.7

11.7

4.0

16.7

1.4

X1–8

34.51

63.6

14.1

6.1

11.8

1.3

88.0

2.7

3.3

16.30

58.9

18.4

10.5

a a

5.2 1.6

1.5

2.7

0.9 1.8 7.8

0.7

1.0

1.7

7.3

2.8 2.4

0.5

1.0

19.17

X1–10

1.9

2.0

X1–4

X1–9

0.6

0.4

a

46.8

7.5

1.3

6.7

Z2–7

1.7

4.2 1.0 3.1

0.7

X1–11

16.06

48.7

19.7

16.8

2.0

2.7

7.4

2.7

X1–12

15.97

42.1

25.4

14.9

4.1

2.2

8.5

2.9

X1–13

23.23

60.0

19.0

16.2

1.5

X1–14

11.80

57.8

12.6

12.2

3.7

0.1

10.0

X1–15

31.57

34.5

33.4

19.6

5.8

2.5

4.3

0.1

X1–16

24.8

38.1

26.7

6.6

X1–17

29.7

32.9

23.5

8.4

X1–18–F

53.7

12.6

12.8

16.9

3.3

4.7

33.5

22.7

8.5

1418–2

9.77

11.6

23.4

13.3

6.2

16.8

1418–3

74.82

19.8

35.1

32.9

7.6

2.8

1418–4

16.73

39.5

18.0

15.3

5.3

1.4

53.2

7.5

5.8

a

32.5

CS–1

b

30.1 56.67

44.3

17.5 30.2

1.7

a

7.31

FG–1

5.8

5.2

10.9

3.7

2.8

2.4

1418–1

WG–1

Alu

0.3

3.9

Z2–8

6.5

Be

27.3

a

Z2–5P

4.1

Cop

1.1

2.3

X1–3R

6.2

8.5

8.1

4.1

X1–2R

Anh

15.3

5.9

20.1

1.0

Gyp

2.5

7.9

50.0

5.6

0.8

a

44.10

46.2

Bas

4.2

1.5

Z2–3

X1–1R

1.4

0.7

1.8

Z2–16F

0.5

6.0

7.9

29.3

Szm

22.7

53.4

Z2–15F

Jar

a

30.14

Z2–11P

Rho

10.0

4.4

Z2–2

Z2–6P

Siderite

4.7

S3–8

70.5

Dol

19.5

S3–9F

Z2–4P

Calcite

8.7

2.5

6.2

21.9

1.0

1.5

4.2

21.0

1.5

1.5

17.4

1.8

1.0 36.3

25.6

Sme, smectite; Chl, Chlorite; Dol, dolomite; Rho, rhodocrosite; Jar, jarosite; Szm, szomolnokite; Bas, bassanite; Gyp, gypsum; Anh, anhydrite; Cop, copiapite; Be, BeSO4·H2O; Alu, alunogen. Rows with blue shading are non-coal benches. Samples 1418-1, -2, -3, and -4 are lump coal samples from the X1 coal seam. WG-1, argillized granite sample. FG-1, unargillized and relatively fresh granite sample. CS-1, carbonaceous sandstone samples. Samples WG-1 and FG-1 were collected at the coal mine mouth. Sample CS-1 was taken from the outcrop of an abandoned surface mine. a Only illite. b Only mica.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

the proportion of this phase in the LTA (y-axis of Fig. 7) is consistent with the concentration of BeO in the coal ash (x-axis; Supplementary Electronic File) calculated from the ICP-MS analysis data (Table 4). 4.3.2. Basement granites Previous studies have shown that the granite in the Lincang Ge ore deposit served as the basement on which the Ge-rich coals were deposited (Hu et al., 2009), and also as the source for sediment input to the coal-bearing sequence. The granite batholith was formed during the late Paleozoic and Mesozoic (~ 212 to 254 Ma, based on zircon U–Pb geochronology; Zhong, 1998), and is composed mainly of biotite– granite and, to a lesser extent, two-mica- and muscovite-granites (Hu et al., 2009; Qi et al., 2002, 2004; Zhang et al., 1987a,b). The rocks consist mainly of K-feldspar, quartz, plagioclase (An24–46), biotite, and muscovite, and accessory phases including magnetite, ilmenite, zircon, apatite, monazite and, rarely, allanite, scheelite, and cassiterite (Hu et al., 2009). The granitic rocks show a calc-alkaline character, with SiO2 ranging from 65.5 to 74.0 wt.%, and total alkalis (K2O +Na2O) from 5.9 to 7.7%, with K2O/Na2O N 1 (Zhong, 1998). The granite is enriched in Ge, ranging from 2.7 to 5.0 μg/g with an average of 3.9 μg/g (Hu et al., 1996), and provided the Ge source for formation of the ore deposit by later (Miocene or younger) hydrothermal fluid leaching. The minerals in the granite sample, FG-1, in the present study, identified by XRD and under the microscope are quartz, biotite, chlorite, albite, and microcline (Table 3; Fig. 8). Comparison of observed and inferred chemical analysis data indicates that a lower percentage of Na and a higher percentage of Ca are present in the granite than are inferred from the XRD data (see Supplementary Electronic File), and suggest that a more Ca-rich plagioclase is actually present in the sample. Some minor minerals, below the detection limit for XRD and Siroquant but identified under SEM-EDS (Fig. 9), include fluorapatite; zircon; sphene; chalcopyrite; galena containing Bi; pyrite; bastnaesite; allanite-(Ce) containing Th, U, and REE; and thorite containing La, Ce, Y, Nd, U, and Ca (Fig. 9). The total alkalis (K2O + Na2O = 7.58) and the ratio of K2O/Na2O (1.54) indicate a calc-alkaline character. Together with the presence of chlorite, sulfide, bastnaesite, and epidote, a number of the minerals in sample FG-1 indicate that the rock has been subjected to hydrothermal corrosion and alteration: e.g., hydrothermally-altered biotite (Fig. 8B), hydrothermally-altered polysynthetic-twinned feldspar (Fig. 8E), kaolinized mica and feldspar (Fig. 8F), chloritized and carbonatized mica (Fig. 8G, H), corroded thorite and allanite-(Ce) (Fig. 9B, D), and cavity-filling epidote in the corroded allanite-(Ce) (Fig. 9D). Hu et al. (2009) also found some pyrite, sphalerite, chalcocite, and galena in quartz veins of the basement granites. In comparison with the average values for world granites (Grigoriev, 2009; Fig. 10), the Lincang granite (sample FG-1) is highly enriched in Ge (CC = 4.84), Se (CC = 14.14), Ag (CC = 14.7), and W (CC = 253) (CC, the concentration coefficient is the ratio of element concentration in investigated sample vs. average for world granites). Additionally, sample FG-1 is enriched in some siderophile elements, Co (CC = 44.9) and Ni (CC = 37.0), that are generally not enriched in granites. Another unusual geochemical feature of the granite is the relatively low concentrations of Nb (CC = 0.61) and Hg (CC = 0.02), although these elements are enriched in the Ge-rich coals as described below. Sample WG-1 is an argillized granite, although macroscopically it appears to have been subjected to weathering. The minerals observed by XRD and Siroquant are mainly quartz and microcline, with small proportions of kaolinite, illite, and jarosite (Table 3). Additional minor minerals were identified under SEM-EDS, including Fe-bearing sulfates, monazite, zircon, xenotime, and Al-oxyhydroxides (or Al-oxides) (Fig. 11). The argillized granite has almost no plagioclase, but has a higher proportion of K-feldspar than sample FG-1 (Table 3). This is consistent with selective removal of plagioclase from the granite during hydrothermal alteration. The dominant components, quartz and microcline, have

9

also been subjected to hydrothermal corrosion (Fig. 11A, C, D, F). The proportion of mica (biotite) is less than in the fresh granite, presumably because it has been hydrothermally altered to illite and kaolinite (Fig. 11E), the proportions of which are higher than in sample FG-1. Fracture-filling quartz (Fig. 11D), Fe-bearing sulfate minerals (Fig. 11B), and chlorite were also probably derived from hydrothermal activity. The differences between samples WG-1 and FG-1 are thus consistent with hydrothermal argillization processes. In comparison with sample FG-1 (Fig. 10B), the argillized granite (sample WG-1) is not only enriched in some elements of epithermal origin (Sb, Hg, As, and Tl), but is also enriched in U, Mo, Ge, and K (Fig. 10B; Table 3). The remaining trace elements, however, are lower in concentration than the same elements in sample FG-1, and were probably leached during hydrothermal argillization. The concentrations of REY in sample WG-1 are lower than those in sample FG-1 (Fig. 12A; Table 6). The REY distribution patterns for WG-1 and FG-1 are quite different, and are characterized by H- and M-types, respectively. The REY in sample WG-1 were probably leached during hydrothermal argillization. The granite samples described by Hu et al. (2009) also have lower REY concentrations than sample FG-1 (Fig. 12A), suggesting that the former had also been subjected to hydrothermal leaching. SEM-EDS data show that the zircon in sample WG-1 contains U (2.91%) and, in some cases, Y (3.16%), Hf (2.75%) and other REEs, for example, 0.25% Tb and 1.34% Yb. The xenotime contains U (2.16%), Th (1.37%), and other REEs (e.g., 2.51% Gd, 4.76% Dy, 0.7% Ho, 3.48% Er, 3.28% Yb). The monazite contains Th (8.54%), U (1.44%), Ag (0.86%), and Zr (5.84%). 4.3.3. Sandstone and mudstone Geochemical and mineralogical data have not previously been reported for the sandstone (including pebbly sandstone) and mudstone in the Lincang Ge ore deposit. Pebbly sandstones occur as roof (Z2-1R, S3-1R) and floor (X1-18F, S3-10F) strata of the coal seams. Sample S3-11F is macroscopically identified as sandstone. Mudstones occur as the immediate roof and floor strata of the S3 seam (S3-2R, S3-3R, S3-9F), as partings in the Z2 seam (Z2-6P, Z2-11P, Z2-5P, Z2-5LP), and as the floor strata of the X1 seam (X1-16F, X1-17F). With the exception of minor percentages of chlorite in sample Z2-1R and dolomite and siderite in sample X1-18F, the sandstone samples all have similar mineral compositions, mainly consisting of quartz and, to a lesser extent, kaolinite, illite, mica, and K-feldspar (Table 3). The trace-element data indicate that the sandstones are enriched in W, Ag, Se, Bi, and Be in comparison with the averages for world sandstones (Grigoriev, 2009; Fig. 13A), and have similar characteristics to those of the granite (FG-1). The five sandstone samples can be classified into two groups based on trace-element compositions: (1) samples S3-1R, Z2-1R, and X1-18F have high W (494–900 μg/g) and, to a lesser extent, Ni and Co concentrations; (2) samples S3-10F and S3-11F have lower W (40–70 μg/g) concentrations and do not have elevated concentrations of Ni and Co. REY plots for all the sandstone samples are similar, showing a M-type REY distribution (Fig. 12B), which is probably connected with acid hydrothermal circulation (McLennan, 1989; Michard, 1989; Seredin and Dai, 2012). The mudstones have higher concentrations of Be, Ge, Sb, W, and, to a lesser extent, Ag, Cs, and Bi, in comparison with averages for world clays (Grigoriev, 2009). The significant enrichment of Ge and Sb in sample X1-16F (LOI = 17.41%) may be related to a strong organic affinity for the trace elements. To our best knowledge, the concentration of Cs in sample S3-3R (231 μg/g) is the highest that has ever been observed in coal deposits. The enrichment assemblage of trace elements in the mudstone of the Lincang deposit is very similar to that in the mudstone from the Pavlovka Ge ore deposit, which is enriched in Ge, Sb, W, Be, and Cs (up to 120 μg/g). Two distribution patterns of REY can be observed in the mudstones of the Lincang Ge ore deposit. (1) The REY in the roof (S3-2R and S3-3R)

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

10

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Table 4 Concentrations of major and trace elements in the X1, Z2, and S3 seams from the Dazhai Mine, Lincang Ge ore deposit, as well as their comparison with averages for common Chinese coals and world low-rank coals (Unit for loss-on-ignition and major-element oxides is % and unit for trace elements is μg/g). Sample

LOI

SiO2

TiO2

Al2O3 Fe2O3

MnO

MgO

CaO

Na2O

K2O

P2O5

SiO2/ Al2O3

Li

Be

B

F

Sc

V

Cr

Co

Ni

Cu

S3–1R S3–2R S3–3R S3–4 S3–5 S3–6 S3–7 S3–8 S3–9F S3–10F S3–11F WA–S3 Z2–1R Z2–2 Z2–3 Z2–4P Z2–5P

1.92 8.29 5.77 86.02 82.88 77.08 54.98 59.87 44.26 7.43 3.09 75.67 1.74 78.73 67.61 14.65 45.41

78.28 56.24 60.29 10.33 11.57 13.22 29.56 27.53 37.88 68.17 70.88 15.79 77.73 15.66 23.44 61.08 51.94

0.320 1.160 1.020 0.069 0.036 0.035 0.073 0.067 0.304 0.440 0.450 0.049 0.297 0.031 0.033 0.007 0.019

14.31 27.15 25.55 1.40 3.05 4.78 11.92 9.71 13.92 18.21 18.81 5.05 14.72 1.89 4.81 0.40 0.85

0.70 1.72 1.48 0.72 1.16 3.58 1.73 1.25 1.24 0.73 0.78 2.03 0.60 2.23 2.72 0.55 0.24

0.011 0.027 0.019 0.003 0.003 0.003 0.005 0.005 0.005 0.007 0.014 0.003 0.009 0.005 0.006 0.054 0.006

0.513 0.836 1.020 0.125 0.152 0.155 0.220 0.197 0.329 0.542 0.519 0.160 0.571 0.250 0.177 0.127 0.111

0.141 0.309 0.270 0.386 0.338 0.283 0.291 0.343 0.316 0.215 0.156 0.325 0.206 0.303 0.291 20.01 0.586

0.135 0.117 0.168 0.028 0.027 0.033 0.049 0.046 0.054 0.134 0.176 0.034 0.132 0.029 0.039 0.042 0.052

3.250 3.660 4.000 0.187 0.220 0.280 0.740 0.573 1.250 3.850 4.890 0.327 3.490 0.167 0.276 0.067 0.095

0.100 0.115 0.099 0.008 bdl 0.008 0.017 0.024 0.029 0.062 0.076 0.010 0.079 0.022 0.013 0.033 0.020

5.47 2.07 2.36 7.38 3.79 2.77 2.48 2.84 2.72 3.74 3.77 3.86 5.28 8.29 4.87 154 61.3

18.2 48.4 43.2 4.92 8.34 13.9 25.5 24.8 43.4 21.7 19.0 13.6 17.0 6.27 16.1 15.1 18.9

3.53 19.0 14.4 333 217 199 163 186 143 16.6 8.19 225 11.2 232 201 63.3 158

16.5 57.8 66.8 55.0 70.5 89.2 55.6 58.2 59.8 17.7 14.7 71.5 10.0 68.5 56.6 4.10 27.5

304 860 807 104 229 286 654 572 699 438 364 310 225 330 314 86 71

3.19 8.62 9.17 3.43 5.01 5.80 0.86 2.73 12.1 4.53 5.70 4.37 2.76 5.84 4.52 bdl 2.05

30.2 120 88.5 197 5.41 5.91 9.92 11.8 68.2 32.5 36.3 44.4 20.7 4.27 4.51 1.77 2.73

25.4 82.3 73.1 9.12 3.85 5.30 6.93 7.70 22.5 27.5 30.4 6.28 19.5 3.00 3.86 8.09 3.46

55.8 11.6 9.01 7.44 3.66 3.93 3.74 6.66 16.5 7.98 3.01 5.05 39.9 9.86 10.3 0.44 15.6

177 39.1 27.2 36.4 14.6 15.2 10.6 21.9 40.0 14.1 5.74 20.2 130 21.8 12.6 4.71 53.2

Z2–5LP Z2–6P Z2–7 Z2–8 Z2–9 Z2–10 Z2–11P Z2–12 Z2–13 Z2–14 Z2–15F Z2–16F WA–Z2 X1–1R X1–2R X1–3R X1–4 X1–5 X1–6 X1–7 X1–8 X1–9 X1–10 X1–11 X1–12 X1–13 X1–14 X1–15 X1–16F X1–17F X1–18F WA–X1 1418–1 1418–2 1418–3 1418–4 WG–1 FG–1 CS–1 1104/1 Lin–1a Lin–1 Chinaa Worldb CC (S3) CC (Z2) CC (X1)

44.46 28.21 81.23 82.85 88.75 66.91 35.93 61.45 68.72 61.16 35.05 26.91 74.34 38.09 61.23 44.46 86.48 82.21 74.54 88.95 70.76 59.38 85.71 86.04 86.68 79.19 89.74 72.86 17.41 9.73 2.69 80.50 93.71 91.56 27.94 85.67 2.04 0.50 47.13 2.89 32.80 78.90 nd nd nd nd nd

53.27 55.88 15.98 14.65 6.62 22.89 48.00 35.30 28.79 30.08 21.44 34.89 20.70 5.07 1.76 6.68 6.73 8.54 16.46 6.56 22.89 36.75 10.65 9.89 8.88 15.82 7.76 16.68 48.27 52.24 67.21 14.65 3.90 3.79 39.14 9.54 74.20 65.33 32.91 79.28 41.35 11.15 8.47 nd nd nd nd

0.032 0.264 0.020 0.017 0.018 0.150 0.147 0.030 0.032 0.084 0.009 bdl 0.04 0.006 0.009 0.033 0.061 0.051 0.034 0.023 0.037 0.052 0.036 0.020 0.028 0.035 0.016 0.139 0.841 0.964 0.484 0.036 0.029 0.021 0.522 0.021 0.037 0.645 0.103 0.02 0.23 0.15 0.33 0.12 nd nd 0.30

1.15 11.56 0.94 1.40 1.03 7.26 13.13 1.71 1.20 3.93 0.13 0.07 2.24 0.14 0.19 1.40 2.42 3.27 6.14 1.38 2.59 1.77 1.83 2.14 2.35 3.23 0.86 7.21 26.22 28.40 19.96 2.22 1.29 2.31 23.31 3.04 14.93 15.58 16.27 13.58 21.80 6.27 5.98 nd nd nd nd

0.17 0.73 0.78 0.15 2.26 0.45 0.56 0.54 0.24 0.36 2.35 0.22 1.05 1.28 0.48 0.16 2.82 4.83 1.34 1.78 2.75 0.95 0.29 0.56 0.53 0.26 0.21 0.90 2.51 3.30 2.20 1.26 0.26 1.37 4.82 0.74 1.00 4.18 1.39 0.82 1.31 0.49 4.85 nd nd nd nd

0.003 0.005 0.004 0.004 0.005 0.007 0.008 0.003 0.144 0.014 0.431 0.124 0.024 0.222 0.247 0.199 0.012 0.006 0.009 0.008 0.004 0.005 0.007 0.005 0.005 0.004 0.003 0.006 0.037 0.058 0.028 0.006 0.004 0.003 0.116 0.003 0.003 0.066 0.009 0.035 0.014 0.004 0.015 0.013 nd nd 0.45

0.100 0.652 0.133 0.159 0.107 0.299 0.419 0.146 0.144 0.253 0.795 0.619 0.182 0.715 0.219 0.203 0.157 0.106 0.127 0.109 0.097 0.194 0.134 0.109 0.122 0.141 0.103 0.238 0.675 0.741 0.615 0.133 0.087 0.085 0.582 0.102 0.022 2.160 0.163 0.06 0.29 0.14 0.22 nd nd nd nd

0.243 0.387 0.304 0.256 0.361 0.413 0.383 0.244 0.266 2.860 37.92 35.91 0.626 50.42 33.27 43.61 0.367 0.202 0.343 0.343 0.188 0.233 0.468 0.420 0.449 0.409 0.434 0.415 0.257 0.282 0.597 0.359 0.300 0.225 0.330 0.239 0.036 3.180 0.013 0.07 0.01 0.08 1.23 nd nd nd nd

0.067 0.065 0.034 0.035 0.022 0.039 0.066 0.066 0.049 0.059 0.067 0.040 0.04 0.040 0.016 0.037 0.023 0.024 0.027 0.025 0.037 0.059 0.026 0.023 0.025 0.029 0.023 0.042 0.106 0.102 0.149 0.031 0.014 0.026 0.063 0.027 0.234 2.990 0.072 0.11 0.05 0.01 0.16 nd nd nd nd

0.179 1.850 0.097 0.101 0.101 1.050 1.080 0.127 0.112 0.374 0.017 0.006 0.213 0.017 0.018 0.125 0.235 0.246 0.381 0.124 0.198 0.197 0.211 0.203 0.223 0.300 0.098 0.820 3.090 3.440 4.740 0.210 0.121 0.174 2.670 0.241 7.330 4.590 1.550 3.41 1.92 0.56 0.19 nd nd nd nd

0.019 0.029 0.007 0.006 0.005 0.017 0.018 0.006 0.005 0.024 0.042 0.036 0.012 0.037 0.043 0.034 0.013 0.009 0.013 0.005 0.008 0.008 0.014 0.012 0.015 0.014 0.013 0.020 0.093 0.104 0.092 0.011 0.004 0.005 0.113 0.007 0.034 0.283 0.132 0.04 0.03 0.01 0.092 0.046 nd nd 0.24

46.3 4.83 7.01 10.5 6.43 3.15 3.66 20.6 4.02 7.65 164 472 12.0 35.5 9.07 4.77 2.78 2.61 2.68 4.75 8.84 20.8 5.82 4.62 3.78 4.90 9.05 2.31 1.84 1.84 3.37 7.45 3.02 1.64 1.68 3.14 4.97 4.19 2.02

21.0 25.7 5.63 5.67 3.02 14.2 31.8 15.5 12.7 17.6 17.5 20.0 9.88 10.4 4.53 9.06 5.45 7.84 18.4 4.05 11.6 12.6 5.37 6.21 5.50 8.86 2.86 14.9 43.5 42.9 16.1 7.40 3.23 5.39 52.5 7.64 11.4 24.7 39.0 26.8 nd nd 31.8 10 1.36 0.99 0.74

469 1364 262 675 289 2000 176 281 269 423 75.2 36.1 432 38.9 123 87.7 344 261 1365 430 497 267 301 314 280 280 261 181 21.6 9.99 2.29 331 337 245 90.8 237 2.31 4.77 10.4 6.7 nd nd 2.11 1.2 187 360 275

27.0 47.5 68.0 64.4 60.8 65.4 32.6 54.3 36.9 33.1 5.42 bdl 56.3 16.6 30.4 22.7 66.3 73.4 78.5 62.7 50.3 40.1 63.4 62.5 57.0 52.6 65.8 53.7 32.5 22.8 3.26 58.52 119 148 65.2 137 bdl bdl 45.0 nd nd nd 53 56 1.28 1.00 1.04

100 946 92 107 45 328 772 115 83 185 205 187 167 387 179 192 93 118 222 51 127 213 90 112 114 175 65 298 857 805 299 123 98 132 1356 202 137 799 762 nd nd nd 130 90 3.45 1.86 1.37

1.80 3.54 2.20 2.32 1.43 3.96 4.29 2.33 2.17 2.23 bdl bdl 2.97 0.60 bdl 1.09 2.12 3.01 3.54 2.99 4.07 3.09 7.84 7.47 8.67 5.62 2.63 5.78 10.3 8.25 6.65 5.11 1.31 3.07 6.44 1.61 1.43 10.5 6.96 2.4 nd nd 4.38 4.1 1.07 0.72 1.25

6.62 19.0 4.12 3.45 2.32 11.1 12.0 5.46 6.22 13.8 2.23 4.42 5.88 4.26 3.52 4.50 7.47 5.43 4.71 2.86 6.53 8.24 5.05 3.37 3.79 4.59 3.19 20.7 123 112 36.1 5.17 8.64 5.99 45.1 4.09 6.74 74.2 15.8 3.0 14.8 26.2 35.1 22 2.02 0.27 0.23

7.46 8.94 4.03 3.32 2.45 7.73 13.6 6.41 6.86 11.5 1.79 3.91 5.31 1.16 1.22 2.68 5.50 4.91 3.51 2.67 7.26 9.45 4.02 6.83 3.89 3.20 2.38 9.01 51.0 54.2 22.0 5.10 5.36 3.69 18.9 2.49 12.7 32.9 18.3 30.0 17.5 12.7 15.4 15 0.42 0.35 0.34

0.36 2.84 0.59 0.45 0.56 0.74 0.44 4.67 3.19 3.69 4.07 0.74 3.77 2.85 2.01 4.48 1.58 6.98 13.6 4.75 4.58 8.17 2.78 2.41 1.20 2.88 1.00 3.37 11.1 14.0 33.2 4.02 1.95 3.32 10.9 3.26 2.44 44.9 3.57 0.8 3.4 1.7 7.08 4.2 1.20 0.90 0.96

1.73 9.37 3.28 1.98 2.37 3.46 2.79 17.5 12.2 13.5 19.7 10.2 10.3 18.8 12.3 18.4 5.26 5.68 8.33 3.81 11.5 24.8 9.29 12.0 3.29 8.20 2.25 7.61 21.8 36.7 99.4 9.59 7.52 7.31 22.4 10.5 2.31 130 6.37 2.0 10.1 11.4 13.7 9 2.24 1.14 1.07

1.42 nd nd nd nd

Zn

Ga

10.3 44.9 40.2 7.42 13.2 16.5 24.8 17.2 24.9 11.4 10.2 14.7 7.19 8.93 11.9 1.84 4.11

29.7 124 99.5 31.7 92.5 168 149 184 256 59.8 44.5 129 24.9 51.6 108 3.54 12.3

9.76 29.5 23.3 8.07 8.06 11.3 17.5 15.6 18.7 11.3 11.8 11.2 7.64 4.94 6.44 0.54 1.51

5.36 16.9 7.10 8.36 5.60 13.7 14.4 8.89 5.29 10.2 1.75 1.69 8.40 2.17 2.62 4.35 9.43 14.0 19.9 9.60 10.7 7.78 8.25 6.73 8.67 8.31 5.15 11.3 29.6 30.0 8.26 8.90 7.74 15.9 22.4 6.81 2.47 17.6 11.3 11.7 16.1 24.1 17.5 15 0.98 0.56 0.59

8.67 67.0 7.81 20.0 8.06 36.9 42.9 11.6 6.44 22.3 4.22 1.32 26.6 6.85 5.29 21.0 18.0 65.3 287 36.8 57.8 19.3 58.4 59.5 44.4 42.0 30.1 60.4 126 111 37.6 47.2 40.3 215 186 25.3 21.6 65.5 88.2 33.8 42.3 94.1 41.4 18 7.14 1.48 2.62

1.79 12.1 2.12 3.31 4.34 9.68 13.53 4.54 3.40 6.30 0.59 0.36 4.58 0.46 2.01 1.92 4.16 4.35 7.43 3.00 3.36 2.06 3.90 5.03 9.35 8.79 22.6 28.1 31.8 30.9 12.3 6.25 2.10 5.36 23.8 4.31 9.74 22.0 20.5 22.3 nd nd 6.55 5.5 2.03 0.83 1.14

LOI, loss-on-ignition; WA, weighted average (weighted by thickness of sample interval); nd, no data; bdl, below detection limit; CC, ratio of concentrations of elements in the Lincang coals to the world low-rank coals. The rows with yellow shading are the weighted average values for the S3, Z2, and X1 seams. a Average concentrations of elements in common Chinese coals (Dai et al., 2012a). b Average concentrations of elements in world low-rank coals (Ketris and Yudovich, 2009).

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

11

Table 4 Concentrations of major and trace elements in the X1, Z2, and S3 seams from the Dazhai Mine, Lincang Ge ore deposit, as well as their comparison with averages for common Chinese coals and world low-rank coals (Unit for loss-on-ignition and major-element oxides is % and unit for trace elements is μg/g). Ge

As

Se

Rb

Sr

Zr

Nb

Mo

Ag

Cd

In

Sn

Sb

Cs

Ba

Hf

Ta

W

Hg

Tl

Pb

Bi

Th

U

1.20 5.25 4.15 1549 1554 1633 782 737 256 9.10 3.65 1394 2.20 2109 1572 37.1 891 603 212 1694 1615 1540 1114 218 1243 1680 801 102 39.9 1538 74.1 939 216 1497 1692 1422 2090 1282 1400 2148 2077 2108 1620 2176 1662 68.1 7.37 1.50 1833 134 639 78.9 681 27.0 13.6 204 nd nd 21.1 2.78 2 697 769 917

2.13 15.4 9.89 138 16.3 212 32.0 30.4 32.5 3.92 2.66 117 6.21 313 237 1.16 6.57 4.56 9.06 149 11.8 401 13.5 4.23 12.4 10.4 11.5 1.68 0.87 134 1.39 5.83 4.30 861 1240 67.6 346 80.0 16.0 21.6 74.8 70.6 9.73 27.1 41.5 28.7 10.2 6.80 212 4.31 47.2 64.8 250 23.9 3.52 54.4 2.4 112 9.1 3.79 7.6 15.4 17.7 27.9

0.73 1.91 1.16 0.36 0.45 0.56 0.29 0.24 0.95 0.39 0.44 0.43 0.58 0.30 0.67 0.01 0.18 0.16 0.39 0.29 0.34 0.50 0.38 0.52 0.17 0.19 0.33 0.01 0.05 0.33 0.05 bdl 0.02 0.72 0.92 0.53 0.88 0.58 0.42 0.35 0.48 0.44 0.31 0.19 0.38 1.68 0.47 0.51 0.51 0.43 1.06 1.33 0.70 0.29 0.99 9.88 nd nd nd 2.47 1 0.43 0.33 0.51

130 185 182 18.7 34.1 55.3 104 113 164 188 198 57.1 133 20.5 52.5 6.90 10.3 20.4 187 11.6 15.3 12.3 112 170 19.8 14.1 50.3 2.28 1.11 27.7 2.69 2.69 15.6 23.8 31.3 63.7 14.9 30.0 24.0 26.8 31.9 32.6 46.7 13.4 116 222 207 196 28.6 14.5 30.7 288 43.4 319 239 240 773 94.1 19.0 9.25 10 5.71 2.77 2.86

34.9 68.0 67.9 38.2 40.2 40.0 40.9 48.9 55.4 53.8 52.0 41.4 39.1 43.2 42.0 252 27.8 31.0 63.5 37.3 38.7 36.5 48.4 64.9 37.9 38.5 107 756 708 48.3 1139 496 569 35.0 27.0 44.7 36.3 27.6 37.7 41.6 41.5 41.7 39.9 34.9 45.0 82.5 74.9 54.7 37.5 22.3 20.0 44.9 25.5 24.0 178 22.7 13.1 24.9 10.1 140 120 0.34 0.40 0.31

105 341 409 95.4 12.5 18.5 19.5 24.1 69.8 139 175 33.4 115 13.73 13.68 3.96 3.20 11.5 107 6.96 9.30 6.47 48.5 53.0 9.96 7.07 21.2 1.05 1.12 13.1 1.83 1.09 10.9 16.1 27.0 15.7 9.26 14.0 12.9 24.4 26.8 16.0 12.2 7.95 42.1 282 301 108 17.1 3.45 4.61 126 5.16 37.5 224 28.7 29.0 77.3 24.3 89.5 35 0.95 0.37 0.49

5.45 25.5 19.8 15.7 19.4 28.3 20.0 36.8 27.1 7.94 8.17 25.2 4.27 28.3 32.9 2.02 7.07 6.61 10.7 14.4 12.5 10.8 21.5 14.4 24.4 13.6 15.9 1.17 1.03 18.5 0.66 6.15 3.83 16.5 26.3 27.8 16.1 29.4 20.0 67.6 56.2 76.3 44.2 25.3 39.1 26.5 24.4 4.39 40.8 0.99 4.38 21.4 3.23 3.74 12.8 61.1 27.0 135 29.3 9.44 3.3 7.64 5.61 12.4

0.24 0.63 0.50 2.70 2.91 4.89 3.50 3.22 2.73 0.82 0.44 3.70 0.64 3.68 4.27 0.31 1.60 1.30 0.65 3.41 3.21 6.60 2.45 0.98 2.18 1.81 1.69 0.25 0.19 3.24 0.19 1.44 0.68 4.53 7.86 3.80 5.14 4.59 2.76 4.76 5.39 5.55 5.12 4.80 3.98 4.97 2.54 4.53 4.89 4.81 23.6 9.28 8.77 3.08 1.47 840 0.2 75.3 35.2 3.08 2.2 1.68 1.47 2.22

0.66 2.09 2.33 0.48 0.10 0.14 0.20 0.20 0.50 0.78 0.98 0.21 0.71 0.05 0.07 0.06 bdl 0.02 0.80 0.01 0.02 0.03 0.31 0.41 0.03 0.01 0.10 0.05 0.07 0.05 0.08 bdl 0.07 0.15 0.26 0.21 0.09 0.14 0.11 0.20 0.22 0.15 0.10 0.10 0.36 1.58 1.69 0.66 0.16 0.08 0.16 0.80 0.08 0.24 1.26 0.33 0.3 nd nd nd 0.09 2.36 0.60 1.73

0.22 0.97 0.95 0.31 1.08 2.43 3.04 2.17 2.47 0.54 0.31 1.74 0.24 0.68 2.04 0.04 0.12 0.10 0.76 0.20 0.48 0.13 0.85 3.49 0.62 0.13 0.32 0.02 0.01 0.51 0.03 0.05 0.24 0.40 0.97 3.32 0.56 0.85 0.26 0.66 0.65 0.78 0.70 0.40 1.13 0.94 0.72 0.23 0.66 0.38 3.96 5.85 0.33 0.33 0.42 3.86 0.05 nd nd 0.25 0.24 7.25 2.11 2.74

0.034 0.136 0.108 0.016 0.030 0.052 0.134 0.116 0.136 0.050 0.044 0.056 0.024 0.016 0.058 0.002 0.006 0.008 0.065 0.006 0.008 0.006 0.040 0.121 0.012 0.008 0.026 bdl bdl 0.016 bdl bdl 0.008 0.014 0.020 0.048 0.008 0.018 0.008 0.016 0.018 0.020 0.030 0.008 0.062 0.132 0.128 0.043 0.016 0.010 0.024 0.155 0.032 0.036 0.089 0.280 nd nd nd 0.047 0.021 2.687 0.78 0.778

2.65 11.4 7.35 2.73 4.33 7.86 21.9 18.3 20.5 5.37 4.22 8.81 1.89 2.42 8.43 0.24 0.54 0.89 8.57 0.53 0.96 0.69 5.33 18.9 1.34 0.35 3.18 bdl bdl 2.07 0.17 0.19 1.32 1.63 2.91 7.53 1.03 2.56 0.77 2.05 2.82 2.90 4.48 1.08 9.07 15.1 13.4 4.76 2.28 1.24 2.86 22.9 4.13 4.21 9.32 37.1 70.4 nd nd 2.11 0.79 11.1 2.61 2.88

2.33 6.49 4.75 361 67.2 38.0 26.6 36.7 25.1 2.77 1.58 106 1.94 38.5 16.3 0.78 3.82 1.70 1.63 3.81 3.50 3.67 3.73 1.56 3.49 3.10 1.63 0.31 0.22 9.70 0.38 1.51 0.70 4.48 8.57 6.29 6.49 2.57 1.83 8.62 6.99 7.71 18.9 409 604 114 23.3 4.89 38.8 2.17 14.4 6.30 4.07 15.8 0.39 163 nd nd nd 0.84 0.84 126 11.6 46.2

18.3 134 231 21.3 23.0 24.5 50.3 45.5 75.5 36.8 33.6 28.8 40.2 22.5 25.7 8.94 14.9 22.8 86.6 35.8 15.0 11.2 96.8 136 28.8 23.4 41.4 2.19 1.21 29.3 2.21 3.08 11.1 24.5 25.2 33.9 12.9 21.2 31.3 19.4 13.7 18.0 26.4 8.99 143 158 92.2 14.0 21.5 20.7 18.1 127 32.7 7.89 12.2 34.7 43.5 nd nd 1.13 0.98 29.4 29.8 22.0

434 315 484 81.3 87.3 85.9 93.0 113 213 536 561 90.6 466 103 111 448 94.6 156 285 101 97.0 79.4 171 213 126 107 226 1398 1305 122 1818 739 843 84.2 77.7 86.1 67.8 99.3 146 87.0 82.5 75.7 86.9 70.6 143 276 247 582 91 58 54 148 73 176 621 68 50.6 88.7 71.3 159 150 0.60 0.81 0.61

3.04 9.69 11.3 1.45 0.26 0.51 0.63 0.62 1.99 3.91 5.13 0.67 3.22 0.24 0.25 0.10 0.10 0.32 3.23 0.20 0.25 0.19 1.45 1.63 0.20 0.22 0.63 0.03 0.04 0.34 0.06 0.03 0.34 0.49 0.71 0.43 0.29 0.26 0.35 0.51 0.30 0.30 0.32 0.24 1.50 8.54 9.34 3.25 0.39 0.13 0.18 4.11 0.23 1.63 6.85 1.81 1.4 nd nd 3.71 1.2 0.56 0.28 0.32

0.69 2.98 2.24 0.05 0.07 0.67 1.17 2.26 3.34 1.00 0.99 0.75 0.53 0.11 0.64 0.02 0.03 0.04 1.12 0.03 0.01 0.06 0.40 2.50 0.08 0.02 0.34 0.01 0.03 0.15 0.05 0.02 0.31 0.15 0.32 0.61 0.004 0.06 0.02 0.02 0.03 0.06 0.05 0.02 0.46 3.55 3.47 0.26 0.07 0.01 0.04 4.44 0.15 0.61 2.14 5.53 18.9 nd nd 0.62 0.26 2.87 0.57 0.28

900 116 148 213 336 339 165 89.6 79.1 40.5 70.3 259 659 167 174 20.3 234 102 69.8 157 185 192 105 45.7 166 156 57.7 57.3 15.2 153 51.2 144 70.9 210 194 186 177 144 154 116 77.4 101 132 175 137 80 155 494 143 332 676 203 701 21.7 557 284 11.0 874 317 1.08 1.2 216 127 119

0.018 0.061 0.038 0.215 0.144 0.712 0.379 0.307 0.319 0.042 0.023 0.414 0.026 0.291 0.716 0.008 0.027 0.016 0.165 0.350 0.042 0.462 0.148 0.147 0.078 0.039 0.072 0.005 0.002 0.22 0.005 0.009 0.035 0.857 1.443 0.245 0.370 0.338 0.117 0.343 0.410 0.312 0.162 0.237 0.290 0.126 0.092 0.030 0.404 0.037 0.132 0.179 0.481 0.019 0.001 9.242 nd nd nd 0.163 0.100 4.140 1.93 4.040

0.71 1.29 1.06 2.31 2.27 9.53 4.17 2.28 2.23 1.08 1.03 5.11 0.84 3.54 5.38 0.05 0.11 0.09 0.87 1.70 0.11 3.51 0.58 1.10 1.33 0.25 0.62 0.01 0.06 1.79 0.06 0.04 0.38 6.64 11.83 4.86 4.47 4.56 2.65 0.64 1.23 1.46 0.45 0.79 1.82 1.78 1.42 0.90 3.02 0.03 0.59 3.75 3.85 4.40 1.32 6.34 3.4 nd nd 0.47 0.68 7.52 2.63 4.44

16.3 64.6 46.0 14.8 27.1 57.9 86.9 63.7 69.4 32.9 28.7 46.1 17.4 13.6 48.3 0.68 2.32 3.31 25.2 8.06 3.92 5.21 13.4 46.2 12.3 3.47 13.5 0.31 0.19 11.4 0.67 0.88 5.99 9.87 25.2 42.4 11.7 25.3 6.64 46.2 72.1 81.9 89.6 16.2 34.1 63.8 60.1 32.2 40.0 5.58 84.9 31.7 14.8 55.6 47.7 34.5 71.2 88.0 31.4 15.1 6.6 6.98 1.73 6.06

0.28 1.62 1.09 0.43 1.76 3.11 6.91 5.92 6.26 1.06 0.43 3.03 0.30 0.77 3.31 0.04 0.20 0.37 3.33 0.31 0.54 0.35 2.16 4.49 1.01 0.27 1.32 bdl 0.004 0.90 0.04 0.05 0.42 0.53 1.53 4.27 0.51 1.26 0.43 0.80 1.15 1.18 1.57 0.32 2.41 2.69 1.97 0.55 0.96 0.95 3.39 6.33 2.92 0.31 1.02 16.9 nd nd nd 0.79 0.84 3.61 1.07 1.15

7.82 40.8 26.7 2.02 1.85 3.67 3.98 4.08 14.7 11.5 12.7 3.08 8.42 0.81 3.15 0.42 0.60 2.51 13.7 1.15 1.09 1.30 7.01 8.35 1.34 0.86 3.63 0.13 0.08 1.85 0.55 0.16 2.09 3.60 3.42 4.60 1.62 2.36 1.50 2.57 2.59 2.80 2.25 1.10 8.39 48.7 44.3 11.7 2.38 3.34 6.68 24.8 2.73 4.27 25.6 11.0 7.6 19.5 10.3 5.84 3.3 0.93 0.56 0.72

2.16 11.3 8.02 9.56 48.3 95.8 60.0 37.4 22.9 5.32 3.98 57.3 3.14 44.2 51.8 1.95 8.40 6.80 7.00 27.8 32.8 24.2 35.5 26.1 46.3 16.7 11.1 0.65 0.26 30.8 0.74 3.97 6.33 24.2 54.9 73.0 60.9 78.2 45.3 110 104 130 67.5 32.1 43.4 30.5 19.5 4.06 75.7 27.3 195 365 124 21.9 8.41 918 4.0 214 72.0 2.43 2.9 19.7 10.6 26.1

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

12

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Table 5 Rare earth elements in the samples from the Lincang Ge ore deposit (μg/g). Sample

La

Ce

Pr

Nd

Sm

Eu

Gd

Tb

Dy

Y

Ho

Er

Tm

Yb

Lu

Type

S3-1R S3-2R S3-3R S3-4 S3-5 S3-6 S3-7 S3-8 S3-9F S3-10F S3-11F WA-S3 Z2-1R Z2-2 Z2-3 Z2-4P Z2-5P Z2-5LP Z2-6P Z2-7 Z2-8 Z2-9 Z2-10 Z2-11P Z2-12 Z2-13 Z2-14 Z2-15F Z2-16F WA-Z2 X1-1R X1-2R X1-3R X1-4 X1-5 X1-6 X1-7 X1-8 X1-9 X1-10 X1-11 X1-12 X1-13 X1-14 X1-15 X1-16F X1-17F X1-18F WA-X1 1418-1 1418-2 1418-3 1418-4 WG-1 FG-1 CS-1 1104/1 Lin-1a Lin-1 Worlda CC-S3 CC-Z2 CC-X1

15.93 66.65 46.93 2.21 3.23 3.82 2.50 2.03 18.15 21.10 18.77 3.00 15.95 2.08 2.86 1.50 1.25 2.81 24.09 1.56 2.12 2.92 12.64 8.97 1.89 1.87 5.36 0.82 0.25 3.11 0.63 0.65 3.03 3.12 3.33 4.62 2.18 2.70 3.18 2.43 2.18 3.12 2.82 1.83 10.05 58.95 48.88 18.92 2.77 2.64 3.10 25.27 2.51 6.75 58.98 18.04 7.3 33.6 10.6 10 0.30 0.31 0.28

32.95 201.92 117.77 4.73 7.66 9.22 9.62 9.54 39.10 45.27 38.49 8.12 32.40 5.01 5.54 3.51 2.94 6.17 51.45 3.55 4.84 6.44 27.48 18.72 4.13 3.96 10.94 1.38 0.39 6.76 1.19 1.38 6.81 7.38 7.54 9.80 5.84 6.26 6.99 6.59 5.92 8.29 8.38 5.08 22.05 177.71 166.27 35.24 7.01 7.89 10.23 86.09 6.76 10.45 132.96 28.04 11.6 45.0 29.5 22 0.37 0.31 0.32

3.80 16.46 11.33 0.57 0.84 1.04 0.77 0.51 4.71 5.11 4.76 0.80 3.82 0.54 0.65 0.42 0.32 0.70 5.58 0.40 0.55 0.82 3.04 2.17 0.47 0.49 1.31 0.18 0.06 0.78 0.16 0.13 0.78 0.93 0.97 1.15 0.71 0.72 0.80 0.75 0.64 0.90 0.78 0.49 2.54 15.86 12.69 4.70 0.79 0.97 1.27 5.89 0.71 1.45 14.89 2.88 1.8 nd nd 3.5 0.23 0.22 0.22

14.11 60.65 41.94 2.26 3.36 4.03 2.82 1.89 16.72 18.95 16.91 3.10 13.91 2.12 2.24 1.70 1.28 2.65 19.68 1.59 2.17 3.08 10.99 7.46 1.83 1.81 4.76 0.69 0.20 2.93 0.53 0.44 2.77 3.46 3.57 3.98 2.84 2.61 2.88 3.14 2.59 3.53 2.87 1.88 9.02 55.16 44.23 16.52 3.02 4.14 4.93 20.96 2.56 5.22 54.36 9.73 7.0 nd nd 11 0.28 0.27 0.27

2.82 11.92 8.16 0.62 1.04 1.27 0.83 0.55 3.89 3.92 3.35 0.95 2.63 0.74 0.72 0.43 0.39 0.61 3.78 0.44 0.58 0.74 2.25 1.85 0.48 0.49 1.04 0.17 0.05 0.74 0.13 0.11 0.63 0.93 1.04 1.17 0.90 0.75 0.68 1.22 1.12 1.50 1.00 0.61 2.08 10.75 8.92 3.30 1.01 1.18 1.49 4.24 0.72 1.40 10.80 2.52 2.3 nd nd 1.9 0.50 0.39 0.53

0.61 1.63 1.28 0.12 0.14 0.16 0.10 0.09 0.59 0.79 0.79 0.13 0.60 0.14 0.10 0.17 0.07 0.12 0.51 0.09 0.09 0.11 0.31 0.26 0.09 0.13 0.21 0.43 0.41 0.13 0.55 0.25 0.34 0.13 0.12 0.12 0.12 0.11 0.14 0.16 0.14 0.22 0.13 0.10 0.28 1.39 1.16 0.80 0.14 0.18 0.13 0.39 0.08 0.21 1.33 0.16 0.1 nd nd 0.50 0.27 0.27 0.29

3.03 12.40 8.30 0.91 1.54 1.82 0.96 0.64 4.22 4.08 3.47 1.33 2.80 1.26 1.10 0.63 0.65 0.75 3.74 0.61 0.75 0.88 2.26 1.87 0.60 0.60 1.11 0.25 0.07 0.95 0.14 0.21 0.76 1.20 1.34 1.48 1.38 1.12 1.03 2.67 2.37 3.29 1.72 1.11 2.43 11.30 9.45 3.44 1.84 1.25 1.53 4.43 0.83 1.61 11.20 2.22 1.4 nd nd 2.6 0.51 0.36 0.71

0.43 1.65 1.11 0.20 0.37 0.44 0.21 0.14 0.81 0.59 0.54 0.31 0.39 0.33 0.29 0.12 0.16 0.14 0.49 0.14 0.15 0.17 0.34 0.36 0.12 0.16 0.18 0.05 0.01 0.20 0.02 0.05 0.14 0.28 0.33 0.36 0.38 0.29 0.25 0.83 0.75 1.03 0.50 0.30 0.50 1.67 1.42 0.54 0.53 0.24 0.32 0.64 0.18 0.33 1.66 0.34 0.2 nd nd 0.32 0.97 0.63 1.67

2.41 8.82 6.17 1.53 2.75 3.15 1.30 0.96 4.76 3.32 2.84 2.26 2.24 2.56 2.20 0.83 1.14 0.97 2.77 1.07 1.16 1.20 2.03 2.04 0.87 0.89 1.11 0.29 0.07 1.42 0.12 0.38 0.77 1.97 2.26 2.47 2.74 2.12 1.92 6.63 5.95 8.05 3.87 2.29 3.34 8.45 7.41 2.92 4.11 1.38 1.90 3.68 1.13 2.30 9.69 1.80 1.1 nd nd 2.0 1.13 0.71 2.05

13.48 41.50 33.17 10.38 17.48 19.58 6.04 4.30 26.92 18.36 15.11 13.90 12.56 17.44 15.08 5.69 8.71 7.64 18.61 9.16 9.56 9.58 13.84 13.16 6.59 7.08 7.96 3.08 1.06 10.58 1.47 4.51 5.68 13.60 16.40 17.88 21.29 17.94 17.99 67.53 56.52 84.61 35.35 26.00 27.55 42.99 37.55 15.62 39.46 7.57 11.53 20.82 9.38 13.79 48.45 9.06 5.3 14.1 5.5 8.6 1.62 1.23 4.59

0.48 1.60 1.20 0.33 0.55 0.64 0.27 0.19 1.01 0.62 0.59 0.46 0.43 0.58 0.46 0.15 0.25 0.20 0.54 0.23 0.24 0.24 0.40 0.42 0.18 0.22 0.23 0.06 0.02 0.31 0.03 0.10 0.16 0.46 0.52 0.56 0.65 0.51 0.48 1.68 1.49 2.03 0.97 0.57 0.78 1.73 1.53 0.61 1.02 0.29 0.41 0.71 0.25 0.49 1.90 0.33 0.2 nd nd 0.50 0.92 0.62 2.04

1.39 4.40 3.51 1.04 1.76 2.06 0.75 0.59 2.90 1.82 1.64 1.47 1.29 1.93 1.50 0.46 0.74 0.62 1.68 0.76 0.81 0.79 1.23 1.25 0.59 0.64 0.71 0.19 0.06 1.00 0.09 0.29 0.44 1.40 1.59 1.71 2.02 1.61 1.51 5.38 4.80 6.42 3.12 1.80 2.42 4.58 4.09 1.66 3.24 0.79 1.20 2.18 0.74 1.56 5.52 0.96 0.4 nd nd 0.85 1.73 1.17 3.81

0.19 0.60 0.51 0.17 0.31 0.35 0.14 0.10 0.51 0.27 0.26 0.25 0.19 0.31 0.27 0.07 0.13 0.10 0.25 0.13 0.14 0.13 0.20 0.23 0.10 0.13 0.12 0.03 0.01 0.17 0.02 0.05 0.08 0.27 0.31 0.33 0.39 0.32 0.29 1.03 0.91 1.24 0.60 0.35 0.44 0.72 0.64 0.26 0.62 0.13 0.21 0.35 0.13 0.24 0.80 0.16 0.1 nd nd 0.31 0.81 0.55 2.01

1.30 3.94 3.46 1.27 2.62 2.96 0.96 0.84 3.60 1.94 1.63 2.08 1.30 2.66 2.29 0.54 1.08 0.80 1.88 1.12 1.14 1.02 1.53 1.62 0.85 0.88 0.91 0.22 0.07 1.38 0.12 0.38 0.53 2.02 2.28 2.45 2.89 2.40 2.19 7.89 6.98 9.37 4.70 2.64 3.16 4.42 3.90 1.62 4.74 0.82 1.50 2.52 0.94 1.70 5.25 1.27 0.6 nd nd 1.0 2.08 1.38 4.74

0.19 0.55 0.50 0.19 0.40 0.44 0.15 0.12 0.57 0.28 0.26 0.31 0.19 0.42 0.34 0.07 0.16 0.12 0.28 0.17 0.18 0.15 0.23 0.26 0.13 0.15 0.14 0.04 0.01 0.21 0.02 0.06 0.08 0.34 0.38 0.41 0.49 0.41 0.37 1.36 1.20 1.60 0.80 0.44 0.53 0.68 0.59 0.25 0.81 0.13 0.25 0.37 0.15 0.25 0.74 0.20 0.1 nd nd 0.19 1.64 1.13 4.26

H-M L-M H-M H H H H H H H-M H-M H H-M H H H H H H-M H H H H H H H H H H H H H H H H H H H H H H H H H H H-M H-M H-M H H H H-M H H H-M H

nd, no data. WA, weighted average (weighted by thickness of sample interval). CC, ratio of concentrations of elements in the Lincang coals to the world low-rank coals. a World low-rank coals, from Ketris and Yudovich (2009).

and floor (X1-16F, X1-17F) strata are characterized by distinct negative Eu and slightly positive Ce anomalies, and by the depletion of HREY relative to the granite (e.g., sample FG-1) (Fig. 12C). This shows the key role of terrigenous REY input from the weathered granite of the sediment-source region. (2) The partings (Z2-5P, Z2-5LP, Z2-6P, and Z2-11P) and one of the floor samples (S3-9F) are characterized by a

H-type enrichment (Fig. 12D), which is probably due to hydrothermal influence (Seredin and Dai, 2012). XRD data show that the pebbly sandstones and sandstones consist mainly of quartz, and, to a lesser extent, kaolinite, illite, mica, and Kfeldspar. Minor proportions of chlorite (4.4%) and carbonate minerals (2.4% dolomite and 1.7% siderite) occur in samples Z2-1R and X1-18F,

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

13

Table 6 Elevated concentrations of trace elements in Dazhai of the Lincang, Wulantuga, and Spetzugli Ge ore deposits (μg/g). Element

Ge Be As Nb Mo Sb Cs W Hg Tl U

Dazhai, Lincanga (N = 52; T = 4.0 m)

Dazhai, Lincang (N = 26; T = 4.18 m)

Wulantugab (N = 13; T = 8.2 m)

Spetzugli (N = 18; Tc = 6.1 m)

Min

Max

WA

Min

Max

WA

Min

Max

WA

Min

Max

WA

737 163 9.73 10.8 1.69 1.63 8.99 57.7 0.04 0.11 9.56

2176 2000 1240 76.3 7.86 604 143 339 1.44 11.8 130

1642 349 166 29.6 4.06 40.3 25.8 168 0.34 2.94 55.5

25.5 nd 0.81 0.35 0.93 0.81 3.73 109 nd 0.04 1.05

2523 nd 410 315 15.1 347 75.1 975 nd 16.23 640

852 nd 47.6 46.8 5.46 32.8 22.7 378 nd 1.62 56

45 14.9 145 0.17 0.28 6.03 2.67 21.1 0.64 0.26 0.22

1170 45.6 878 3.52 1.36 692 23.5 514 6.64 5.91 1.02

273 25.7 498 1.35 0.82 240 5.29 115 3.17 3.15 0.36

63.1 16.6 0.4 1.4 nd 14.5 1.9 120 0.0 0.0 0.8

2012.8 152.6 113.3 11.0 nd 1175 57.2 750 0.8 0.8 10.9

1165 81.2 46.7 5.6 17.0d 369 14.8 326 0.4 0.2 2.6

N, sample number; T, common total thickness of Ge-rich coals; Min, minimum; Max, maximum; nd, no data; WA; weighted averages by thickness of sample interval. a From Qi et al. (2004) and Hu et al. (2009). b From Dai et al. (2012). c Common total thickness of 18 bench samples from 4 coal seams of 2 drill holes. d From Seredin et al. (2006).

respectively. The mudstones are composed mainly of quartz, kaolinite, illite + mica, and, to a lesser extent, feldspar. Small proportions of chlorite, pyrite, and siderite occur in various mudstone samples (Table 3). Smectite occurs only in mudstone samples Z2-6P (16.4%) and Z2-11P (7.4%). The modes of occurrence of the minerals (e.g., quartz, K-feldspar, kaolinite, zircon, and monazite; Fig. 14) suggest that they were derived from detrital materials of terrigenous origin. The particles of these minerals vary considerably in size and are poorlysorted, indicating that the sediment-source region was not far from the coal basin, and are consistent with the basement granites also serving as the source of sediment input. Minor barite is distributed in the illite and is probably of epigenetic origin. Minor proportions of other minerals were observed in sample X1-16F by SEM-EDS techniques, including lanthanite ((La,Ce)2[CO3]3·8H2O), silicorhabdophane containing Th and U, chalcopyrite, and Fe-bearing sulfate minerals with a size less than 1 μm that are probably products of pyrite oxidation. The existence of these secondary minerals in the sample suggests a slight influence of hydrothermal solutions. 4.3.4. Quartz–carbonate and carbonate metasomatites Qi et al. (2004) and Hu et al. (2009) reported siliceous rocks and siliceous limestones of hydrothermal origin in the Zhongzhai Mine rather than in the Dazhai Mine. Two types of metasomatites of hydrothermal origin have been identified in the present study: quartz–carbonate metasomatites (Z2-4P, Z2-15F, and Z2-16F) and carbonate metasomatites (X1-1R, X1-2R, and X1-3R). The carbonate metasomatites are dominantly composed of calcite (92.2% for X1-1R, 93.2% for X1-2R, and 83.4% for X1-3R), with minor amounts of quartz, kaolinite and rhodocrosite (Table 3). The quartz–carbonate metasomatites consist mainly of quartz and calcite (Table 3). In addition to sample Z2-4P, both the quartzcarbonate and carbonate metasomatites have a minor proportion of rhodocrosite, which is consistent with the high concentrations of Mn (up to 0.7% MnO) in the chemical analysis data for these samples (Table 4). Rhodocrosite has been found in a few other coal deposits, and is thought to be a product of hydrothermal alteration (Querol et al., 1997). The occurrence of rhodocrosite in the metasomatites rather than in the other coal benches, partings, and host rock samples of the present study (Table 3), further indicates a hydrothermal origin. The U/Th ratios for the quartz–carbonate and carbonate metasomatites are much greater than 1 (Table 4), which is also evidence for a hydrothermal origin. The normal sedimentary partings, roof and floor strata in the present study have U/Th values less than 1, with the exception of samples S3-9F and Z2-11p which had been influenced by

hydrothermal solutions (with evidence of H-type REY enrichment). Samples S3-9F and Z2-11P have high LOI values, high Ge concentrations, and U/Th values N 1 (Table 4). Three factors that may cause the enrichment of U relative to Th in coal include marine influence (Gayer et al., 1999), euxinic environment (Dai et al., 2014b), and infiltrational and exfiltrational hydrothermal solutions (Bostrom, 1983; Bostrom et al., 1973; Dai et al., 2014a,b,c; Seredin and Finkelman, 2008). The coal seams of the present study were deposited in a continental rather than a euxinic environment or an environment influenced by seawater (Hu et al., 2009; Qi et al., 2004, 2007a). All the coal benches have U/Th values N 1, also suggesting hydrothermal influences. Compared to the upper continental crust (Taylor and McLennan, 1985), the REY concentrations in the metasomatites are very low (Fig. 12E, F). This may be related to low REY concentrations in the hydrothermal sources, although a number of cases have shown that hydrothermal solutions may lead to M- and H-REY enrichment in coal deposits (Seredin and Dai, 2012). The metasomatites at Lincang do not display Ce anomalies, probably due to the continental environment of their formation. Murray et al. (1990) found that Ce anomalies in interbedded cherts and shales are connected to their depositional regimes; cherts and shales influenced by continental input show no or only slight Ce anomalies. The low REY concentration and absence of Ce anomalies in the metasomatites of the present study are consistent with the data reported by Hu et al. (2009). However, the REY in the metasomatites are characterized by H-type enrichment and distinctive positive Eu anomalies (Fig. 12E, F). An enrichment of HREY in coal deposits caused by hydrothermal solutions is generally observed (Dai et al., 2012b; Seredin and Dai, 2012). The distinctive positive Eu anomalies in the metasomatites of the present study were probably due to two factors: (1) the ionic radii of Eu2+ and Ca2+ are similar, and thus Eu2+ could be easily incorporated into calcite, leading to fractionation between Eu and other REY (Qi et al., 2002). (2) Eu is generally concentrated in the K-feldspar of the granite; therefore, intense leaching of this abundant mineral by hydrothermal solutions passing through the alkaline basement granites would lead to Eu enrichment in those solutions (Seredin et al., 2006). Such Eu enrichment has also been observed in hydrothermal water vapors in Yellowstone National Park (Lewis et al., 1995). The low concentrations of REY, the absence of Ce but the presence of distinctive positive Eu anomalies, and the presence of a H-REY enrichment type further indicate a hydrothermal origin for the metasomatites. Hu et al. (2009) indicate that Ge appears to be concentrated not only at the top and bottom of coal seams, but also in the coal benches where they are mainly in contact with siliceous rocks or siliceous limestones.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

14

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

SiO2

100

Al2O3

(B) 40

Al2O3 from XRD Analysis (%)

SiO2 from XRD Analysis (%)

(A) 80

30

60

20

40

10

20 0 0

20

40

60

80

0

100

0

SiO2 from Chemical Analysis (%)

(C)

CaO from XRD Analysis (%)

Fe2O3 from XRD Analysis (%)

20 15 10 5 0 5

10

15

20

25

100

20 0 0

CaO from XRD Analysis (%)

K2O from XRD Analysis (%)

4 2 0 4

6

8

35

40

20

40

60

80

100

CaO

(F)

6

2

30

CaO from Chemical Analysis (%)

8

0

25

60

30

K2O

10

20

80

Fe2O3 from Chemical Analysis (%)

(E)

15

CaO

(D)

25

0

10

Al2O3 from Chemical Analysis (%)

Fe2O3

30

5

10

10 8 6 4 2 0 0

K2O from Chemical Analysis (%)

2

4

6

8

10

CaO from Chemical Analysis (%)

Fig. 6. Comparison of observed normalized oxide percentages from chemical analysis (x-axis) to oxide percentages for sample ash inferred from XRD data (y-axis). The diagonal line in each plot indicates equality. (F) is the enlargement of the red rectangle area in (D). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

However, it appears from the present study that the elevated concentrations of Ge through the coal-seam sections are not closely related to contacts with hydrothermal metasomatites (Fig. 18B, C). The coal

benches in immediate contact with metasomatites, for example, do not have higher Ge concentrations than those in indirect contact with metasomatite layers (Fig. 18B, C). 4.3.5. Coal

Fig. 7. Comparison of observed normalized BeO percentage in coal ash from chemical analysis (x-axis) to oxide percentages for sample ash inferred from XRD data (y-axis). The diagonal line in the plot indicates equality.

4.3.5.1. Minerals in the coal. The minerals in the coals are mainly represented by quartz, and, to a lesser extent, kaolinite, illite, and mica (Table 3, Figs. 15, 16). Minor proportions of K-feldspar, pyrite, jarosite, szomolnokite, bassanite, anhydrite, copiapite, a hydrous beryllium sulfate phase (BeSO4·4H2O), and alunogen are also present in the coal LTA samples (Table 3). Mixed-layer illite/smectite (I/S) is present in some benches of the Z2 coal (Table 3). The modes of occurrence as irregular colloidal forms (Fig. 15A–E), as aggregates composed of fine-grained particles (Fig. 16B), and as cellfillings (Fig. 16C), indicate that the quartz in the coals was deposited from multi-stage hydrothermal solutions. Quartz occurring as discrete particles (Fig. 15F) in the collodetrinite may, however, be derived from detrital material of terrigenous origin.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

15

Fig. 8. Minerals in the granite sample, FG-1, observed under the microscope with transmitted light. (A), Quartz and mica, granitic texture. (B), Quartz and mica; the upper left mica has a hexagon shape and its inner part has been hydrothermally altered. (C), Plagioclase with zonal texture and sericitization in the inner part. (D), Quartz (lower yellow part), perthite formed by alteration of albite replacement for K-feldspar. (E), Hydrothermally-altered polysynthetic-twinned feldspar. (F), Kaolinitization of mica and feldspar; (G), Chloritization of mica. (H), Carbonation of mica. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Kaolinite occurs as fine aggregates (Fig. 16C, D), as massive forms in collodetrinite (Fig. 16F), as cell-fillings and, in some cases, as coatings on framboidal pyrite (Fig. 16E). The latter two forms indicate an authigenic origin and the former two forms suggest derivation from the sedimentsource region. Illite occurs as long strips in collodetrinite (Fig. 16A, C, D, F) and was probably a detrital material input from the sediment-source region. K-feldspar and mica, typically reported as detrital materials of terrigenous origin (Ward, 2002), were also derived from the sediment-source region, which is mainly composed of granite in the present study.

Pyrite occurs as dispersed fine-grained crystals in collodetrinite (Fig. 16A, D), and as framboidal (Fig. 16E), massive (Fig. 15B), and cavity-filling forms (e.g., cavities between different illite particles; Fig. 16F). The relation between pyrite and illite (Fig. 16F) suggests that formation of the illite was earlier than that of the pyrite, consistent with a detrital origin for the illite and an authigenic origin for the pyrite. A number of sulfate minerals, including gypsum, bassanite, anhydrite, jarosite, szomolnokite, copiapite, and alunogen, were observed by XRD and Siroquant techniques. Anhydrite, bassanite, and alunogen may represent artifacts produced in the plasma ashing process, formed

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

16

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Fig. 9. SEM backscattered images of minerals in the granite sample, FG-1. (A), Fluorapatite, galena, pyrite, chalcopyrite, quartz, and epidote. (B), Fluorapatite and thorite. (C), Albite, K-feldspar, pyrite, and REY-bearing Ca(CO3)F. (D), Biotite, albite, calcite, zircon, quartz, corroded allanite-(Ce), and cavity-filling epidote.

by interaction between the organic sulfur in the coal, and Ca and Al occurring as inorganic components in the organic matter (Carmona-López and Ward, 2008; Ward et al., 2001; Zhao et al., 2012). However, the bassanite and anhydrite may also have been derived from dehydration

of gypsum present in the raw coal samples (cf. Dai et al., 2012b). Gypsum in coal may be formed by reactions between calcite and sulfuric acid, with the acid being produced by oxidation of pyrite in the coal (cf. Pearson and Kwong, 1979; Rao and Gluskoter, 1973). It may,

(A)

(B)

Fig. 10. Concentration coefficients for sample FG-1 (CC, ratio of sample FG-1/average world granite) and concentration ratios for argillized granite sample WG-1 vs. sample FG-1.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

17

Fig. 11. SEM backscattered images of minerals in the argillized granite, WG-1. (A), Monazite, microcline, zircon, xenotime, and quartz in the sample. (B), Quartz and Fe-bearing sulfate mineral. (C), Microcline, monazite, quartz, and Al-oxyhydroxides or Al-oxide. (D), Corroded microcline and cavity-filling quartz. (E), Illite and kaolinite. (F), Microcline, xenotime, and corroded zircon. Al, Al-oxyhydroxides or Al-oxide; I, illite; K, kaolinite.

however, also be formed by precipitation from pore waters containing dissolved Ca and SO4 components (Ward, 1991). Jarosite (cf. Rao and Gluskoter, 1973), szomolnokite (Chou, 2012; Kruszewski, 2013; Riley et al., 2012; Zhao et al., 2013), and copiapite (Huggins et al., 1983; Kruszewski, 2013; Zodrow, 2005) are common secondary minerals derived from the oxidation of iron sulfide phases. 4.3.5.2. Elements in the coal. Compared to the average for Chinese coals, the coals from the Lincang Ge ore deposit are higher in SiO2 and, to a lesser extent, K2O, but are depleted in Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O, and P2O5. They also have a higher SiO2/Al2O3 ratio. Trace elements in the three different coal seams show similar abundances (Table 4; Fig. 17), with the exception of some medium- (Tb, Dy, and Y) and heavy-REY (Ho, Er, Tm, Yb, and Lu) that are enriched in the X1 seam. Compared to average values for world low-rank coals (Ketris and Yudovich, 2009), and based on the enrichment classification of

trace elements in coal (Dai et al., 2014b), elements Be, Ge, and W are unusually enriched in the Lincang coals, with a concentration coefficient N100 (CC = ratio of element concentration in investigated coals vs. average for world low-rank coals); elements As, Sb, Cs, and U are significantly enriched (10 b CC b 100); niobium is enriched (CC = 8.55); zinc, Rb, Y, Cd, Sn, Er, Yb, Lu, Hg, Tl, and Pb are slightly enriched (2 b CC b 5). The remaining elements are either close to (0.5 b CC b 2) or lower than (CC b 0.5) the average values for world low-rank coals (Ketris and Yudovich, 2009). The assemblage of elevated trace element concentrations in the Dazhai coals is similar to those of the Wulantuga coals, Inner Mongolia, China (Dai et al., 2012b; Du et al., 2009; Zhuang et al., 2007), and the Spetzugli coals of the Russian Far East (Seredin, 2003a,b; Seredin and Finkelman, 2008). These three Ge ore deposits are all enriched in Be, As, Ge, Sb, Cs, W, Hg, and Tl (Table 6). However, relative to the Wulantuga and Spetzugli deposits, the coals from Lincang are highly

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

18

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

(A)

(B)

(C)

(D)

(E)

(F)

Fig. 12. REY distribution patterns for granites, roofs, floors, and partings of the Lincang Ge ore deposit. (A), Samples FG-1 and WG-1, and the average for three granite samples from Hu et al. (2009). (B), Pebbly sandstone and sandstone samples. (C) and (D), Mudstone samples. (E), Quartz – carbonate metasomatites, (F), Carbonate metasomatites. REY are normalized to Upper Continental Crust (UCC) (Taylor and McLennan, 1985).

(A)

(B)

Fig. 13. Concentration coefficients (CC) for sandstone (A) and mudstone (B) samples in the Lincang Ge ore deposit. CC, ratio of investigated samples vs. average world sandstone/ mudstone.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

19

Fig. 14. SEM backscattered images of detrital minerals of terrigenous origin in sample X1-16F. (A), Quartz, K-feldspar and kaolinite. (B), Zircon, K-feldspar and kaolinite. (C), Monazite. (D), Monazite, quartz, K-feldspar and kaolinite.

enriched in Be, Nb, and U (Table 6). The Lincang coals are characterized by an enriched-element assemblage of Ge–W–Cs, Be–Nb–U, and As– Sb–Hg; the Wulantuga and Spetzugli coals are composed of Ge–W and As–Sb–Hg. Based on their abundance, sources, and modes of occurrence, the elements in the Dazhai coals can be classified into four groups. Group 1 includes elements Li, F, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, In, Sn, Ba, Hf, Ta, Th Bi, the LREE, Eu, and the major elements (with the exception of Si); Group 2 includes Ge, Be, W, U, Nb, Cs, and Si; Elements in Group 3 include As, Sb, Hg, Tl, Pb, and Cd; and Group 4 consists of the HREE, some MREE (Gd, Tb, and Dy), and Y. The elements in Group 1 have concentrations close to the averages for world low-rank coals (Ketris and Yudovich, 2009; Fig. 17). Among a number of geological factors that may influence the element abundance in coal (Dai et al., 2012a), the sediment-source region seems to have played a dominant role in determining the concentrations of these elements. The elements in Group 2 are highly enriched in the Lincang coals (Fig. 17) and were derived from the granite after it had been significantly leached by hydrothermal solutions. Germanium, W, and U mainly occur in the organic matter, and elements such as Be, Nb, and Cs have a mixed organic–inorganic affinity. These are discussed more fully below. (1) Germanium. The concentration of Ge in the coals of the present study is from 603 to 2176 μg/g, with a weighted average of 1590 μg/g. Qi et al. (2004) and Hu et al. (2009) showed that Ge in the Ge-rich coal of the Dazhai Mine varies from 25.5 to 2523 μg/g, with an average of 852 μg/g (52 samples), approximately half of the Ge concentration found in the present study, indicating a significant variation of Ge concentration in the ore deposit. The Ge concentration decreases from the lower X1 seam (X1, 1833 μg/g on average)

through the middle Z2 seam (1427 μg/g on average) to the upper S3 seam (1394 μg/g on average) (Table 3). The correlation coefficient for Ash-Ge (− 0.40) in the sample suite indicates that the Ge occurs mainly in the organic matter, consistent with several previous studies of coal-hosted Ge ore deposits (Dai et al., 2012b; Du et al., 2009; Hu, et al., 2009; Qi et al., 2007a; Seredin and Finkelman, 2008; Zhuang et al., 2006). The vertical distribution of Ge concentration varies slightly through each single coal seam in the present study, but has a distinct inverse relationship with ash yield (Fig. 18A, B, C). The Ge concentration varies considerably through the coal seam section in the Wulantuga Ge ore deposit (Dai et al., 2012b; Du et al., 2009; Zhuang et al., 2006). The variation of Ge enrichment through the three vertical sections (Fig. 18A, B, C) shows that Ge can be concentrated in any portion of the coal seams, although “Zilbermints Law” (Yudovich, 2003; Zilbermints et al., 1936) suggests that Ge enrichment occurs near the bottom, roof, and partings of the host coal seam. Germanium enrichment in different portions of the seam (upper, middle and lower) in the Wulantuga Ge ore deposit has also been observed by Zhuang et al. (2006), Du et al. (2009), Qi et al. (2007a), and Dai et al. (2012b). In the present study, coal bench Z2-14 (immediately overlying the floor sample Z2-15-F) has a lower Ge concentration than most of the other benches further from the bottom, roof, and partings. The Ge-rich coal portions underlying partings Z2-6P and Z2-11P are thick (Fig. 18B), 33.5 cm (thickness of Z2-12 and Z2-13) and 59 cm (total thickness of Z2-7, Z2-8, and Z2-9) respectively. However, Yudovich (2003) noted that the Ge-rich zones underlying or overlying an intraseam parting are, “as a general rule, not thicker than 5–10 cm”. (2) Tungsten. Compared to the average for world low-rank coals (1.2 μg/g;

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

20

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Fig. 15. SEM backscattered images of minerals in coal bench samples. (A), Authigenic quartz formed at different stages in sample Z2-9. (B), Authigenic quartz and pyrite in sample Z2-9. (C), Authigenic quartz formed at different stages and detrital illite of terrigenous origin in sample Z2-9. (D), Authigenic quartz in organic matter of sample Z2-13. (E), Authigenic quartz formed at different stages in Z2-13. (F), Detrital quartz of terrigenous origin in sample X1-5.

Ketris and Yudovich, 2009), the Dazhai coals are significantly enriched in W (average 170 μg/g). The weighted W concentration in the S3 seam (259 μg/g) is much higher than that in the Z2 and X1 seams (159 and 143 μg/g, respectively). The negative correlation coefficient between W and ash yield (r = −0.36) indicates that the W has an organic affinity. Based on the W concentrations in different density fractions of Ge-rich coals, Seredin et al. (2006) also showed that W mainly occurs in the organic matter. Like Ge, the W in the Wulantuga and Spetzugli Ge ore deposits is mainly associated with the organic matter (Dai et al., 2012b; Seredin and Finkelman, 2008; Seredin et al., 2006). Studies by Eskenazy (1982) and Finkelman (1995) have shown that W in coal may occur both in the organic matter and as oxide minerals. The concentrations of W in the fly ash and slag derived from the Dazhai coals are 3918 and 499 μg/g, respectively (Dai et al., 2014a). Such a differentiation is consistent with a large proportion of the W in the coal being organically-associated, allowing it to be volatized and then concentrated in the fly ash during coal combustion. The W concentration is also higher in the fine-grained than the coarse-grained fly ash derived from the Wulantuga and Spetzugli Ge-rich coals. For example, the W concentration is 1002 and 2378 μg/g in the fly ashes collected respectively from the baghouse filter and electrostatic precipitator at Wulantuga;

and it is 2860, 518, and 320 μg/g in cyclone fly ash, baghouse filter fly ash, and slag, respectively, at Spetzugli (Dai et al., 2014a). This indicates that the volatized organically-associated W is apt to be concentrated in the fly ash particles with larger surface area. Some studies have found that the highest W concentrations are confined to the lower parts of coal beds. For example, in the Pirin deposit, the lower 10 m in the bed (with total thickness of 16.8 m) is enriched in W, and W and Ge show similar variations through the seam section (Eskenazy, 1982). However, in the present study, tungsten appears to be concentrated in the top and bottom portions of the X1 seam (Fig. 18C) and the middle portion of the Z2 seam (Fig. 18B). In most cases, the variation of W through the coal seam sections is similar to that of Ge, with the exception of the upper portion of the X1 coal (Fig. 18A, B, C). (3) Beryllium. The Be concentration varies from 158 to 2000 μg/g through the seam sections of the three coal beds. The weighted average Be concentration of 343 μg/g is much higher than the average value for world low-rank coals (1.2 μg/g; Ketris and Yudovich, 2009). Indeed, to the best of our knowledge, such high a concentration of Be in coal has not previously been reported. The Be is concentrated in the upper portions of the S3 and X1 seams, and in the middle portion of the Z2 seam (Fig. 18). Owing to its low abundance in coal and its low atomic number,

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

21

Fig. 16. SEM backscattered images of minerals in sample S3-6. (A), Authigenic quartz and detrital illite and kaolinite. (B), Quartz aggregates of authigenic origin. (C), Framboidal pyrite, detrital illite, authigenic quartz as cell-fillings (lower right). (D), Dispersed pyrite crystals, detrital illite, and kaolinite in the collodetrinite. (E), Framboidal pyrite coated by authigenic kaolinite. (F), Kaolinite of terrigenous origin, detrital illite and cavity-filling pyrite.

there is no direct evidence (e.g., SEM-EDS, EPMA, or laser-ablation ICP-MS) for the mode of occurrence of Be in coals, and in many coal deposits it has only been deduced by indirect methods (e.g., statistical analysis and density fractions; Eskenazy, 2006; Eskenazy and Valceva, 2003; Kolker and Finkelman, 1998; Kortenski and Sotirov, 2002). Beryllium in coal is generally thought to be either organically bound if it is elevated or claymineral associated when the Be concentration approximates Clarke values (Eskenazy, 2006; Kolker and Finkelman, 1998). However, a study by Dai et al. (2012b) showed that the elevated concentration of Be (25.7 μg/g) in the Wulantuga Ge ore deposit is mainly associated with minerals. The correlation coefficient for Be-ash (r = 0.07) in the present study indicates that the Be mainly has a mixed inorganic–organic affinity. However, it appears from the Be-ash relations (r =

−0.76) of the individual seams that Be in the S3 coal is mainly organic associated and has an inorganic–organic mixed affinity in the Z2 (r = 0.18) and X1 (r = 0.17) seams (Fig. 19). Significant proportions of a hydrous beryllium sulfate (BeSO4·4H2O), as discussed above, are present in some benches of the Z2 and X1 seams. However, this phase was not detected in any benches of the S3 seam (Table 3). (4) Niobium. Niobium is enriched in the Lincang coals (6.61–76.3 μg/g, mean 28.2 μg/g) compared to the average for world low-rank coals (3.3 μg/g; Ketris and Yudovich, 2009). The lower X1 seam has a higher Nb concentration (40.8 μg/g) than the upper S3 (25.2 μg/g) and middle Z2 (16.7 μg/g) seams. Qi et al. (2004) also showed that Nb is enriched in the Dazhai coals (mean 46.8 μg/g, 52 samples). However, Dai et al. (2014a) showed that Nb is

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

22

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

(A)

(B)

(C)

(D)

Fig. 17. Concentration coefficients (CC, ratio of element concentration in investigated coals vs. average for world low-rank coals) for high-Ge coals from the Dazhai mine, Lincang Ge ore deposit. (A), CC for S3 coal; (B), CC for Z2 coal; (C), CC for Z1 coal; and (D), for all the Dazhai coals.

depleted in the Wulantuga coals (mean 1.35 μg/g) and is not significantly enriched in the Spetzugli Ge-rich coals (7.4 μg/g on average based on 12 samples of three seams: II-low, II-up, and III-low) in the Luzanovka Graben deposit of Primorye. Seredin et al. (2006) also reported around 2.2–3.7 μg/g Nb in the Luzanovka Graben Ge deposit. The concentration of Nb in the coals of the present study varies significantly, with highest values occurring in the lower (e.g., S3-8 bench of S3 seam), middle (e.g., X1-10, X1-11, and X112 benches of X1 seam), and upper (e.g., Z2-2 and Z2-3 benches of Z2 seam) portions of different seam sections (Fig. 18). The mode of occurrence of Nb in coal has not been studied in great detail. It is generally considered that Nb in coal is mainly present in oxide minerals (e.g., rutile; Finkelman, 1993), or is organically associated (based on observations from density fractions; Seredin, 1994). However, studies of density fractions of a Ge-bearing coal with a concentration of 3.4 μg/g Nb from the Luzanovka Graben, southern Primorye, showed that the Nb is inorganically associated (Seredin et al., 2006). The negative correlation coefficient for AshNb (r = −0.13) in the present study suggests that the Nb has an

organic–inorganic mixed affinity. Separate studies (Dai et al., 2014a) show that Nb is highly enriched in the slag (67.9 μg/g) but depleted in fly ash (6 μg/g) derived from the Dazhai coals. This is probably due to its high boiling point (4742 °C) and suggests a mineral association, although a proportion of Nb also appears to be organically bound. (5) Uranium. Among the three currently-mined Ge ore deposits, uranium is only enriched in the Lincang Ge ore deposit. Uranium has an average concentration of 56 μg/g in the Lincang deposit, which is much higher than that in the Wulantuga (0.36 μg/g) and Spetzguli (2.6 μg/g) Ge ore deposits and also higher than the average value for world low-rank coals (2.9 μg/g; Ketris and Yudovich, 2009). The correlation coefficient of Ash-U is −0.4, suggesting that the U is mainly associated with coal's organic matter. Seredin and Finkelman (2008) and Dai et al. (2014b) also showed that U in U-bearing coal deposits worldwide is mainly associated with the organic matter, and that only a small proportion of the U occurs in U-bearing minerals (e.g., coffinite and brannerite). Seredin and

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

(A)

Thickness Sample Secon Ad (%) (cm) 10 30

Ge (μg/g) 50 1

Be (μg/g)

100 10000 0

200

As (μg/g) 400 0

Rb (μg/g) 200 10

110

Nb (μg/g) 0

20

Sb ( (μg/g) 40 0

23

Cs (μg/g)

200

400 0

W (μg/g) 200 0

500

Hg (ng/g) 1000 0

U (μg/g) 0

500

50

100

0

S3-1R 20

S3-2R 40

60

S3-3R S3-4 S3-5

80

S3-6 100

S3-7 120

S3-8 S3-9F

140

S3-10F S3-11F

160

Gravel sandstone

(B)

Thickness Sample Secon Ad (%) (cm)

10 30 50

Siliceous limestone

Ge (μg/g)

Be (μg/g)

0 1000 2000

0

As (μg/g)

1000 2000 0

200

Coal

Rb (μg/g) 400 0

100

Sandstone

Nb (μg/g) 200

0

Sb ( (μg/g)

20

40 0

20

40

Cs (μg/g)

W (μg/g)

0

0

50 100

Hg (ng/g) 0

500 1,000

U (μg/g) 0

300 600

20 40 60

0

Z2-1R Z2-2 50

Z2-3 Z2-4P Z2-5P

100

Z2-5LP Z2-6P Z2-7 Z2-8

150

200

Z2-9 Z2-10 Z2-11P Z2-12 Z2-13 Z2-14 Z2-15F

250

Z2-16F

Gravel sandstone

(C) Thickness Sample Secon

Ad (%) 10

(cm)

Ge (μg/g) 30

0

2000 0

Siliceous limestone

Be (μg/g) 1000

As (μg/g) 0

Coaly clay

Rb (μg/g)

500 1000 0

Nb (μg/g)

Clay

Sb ( (μg/g)

200 0 20 40 60 80 1

100

Coal

Cs (μg/g) 0

100

W (μg/g) 200

0

250

Hg (ng/g) 500 0

1000

U (μg/g) 0

100

200

0

X1-1R X1-2R X1-3R 50

X1-4 X1-5 X1-6 X1-7

100

X1-8 X1-9

150

X1-10

X1-11 X1-12 200

X1-13 X1-14 X1-15 X1-16F 250

X1-17F X1-18F

Gravel sandstone

Carbonate

e

Clay

Coal

Fig. 18. Variations in ash yield and concentrations of Ge, Be, As, Rb, Nb, Sb, Cs, W, Hg, and U through the sections of the S3, Z2, and X1 seams of the Lincang Ge ore deposit. (A), S3 coal seam; (B), Z2 coal seam; (C), X1 coal seam.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

24

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

(A)

(B)

(C)

Fig. 19. Relation of Be concentration to ash yield. (A), S3 seam. (B), Z2 seam. (C), X1 seam.

Finkelman (2008) described two types of U enrichment in coal: (1) epigenetic infiltration type and (2) syngenetic or early diagenetic infiltration and exfiltration types. The enrichment of U in the Lincang coals is of the second U enrichment type, as discussed more fully below. (6) Cesium. The concentration of Cs in Ge-rich coals of the Dazhai Mine, Lincang Ge ore deposit, varies from 8.99 to 143 μg/g and averages 25.2 μg/g. This is higher than the average for world low-rank coals (0.98 μg/g; Ketris and Yudovich, 2009). The mode of Cs occurrence in coal has not been investigated in great detail. Cesium can isomorphously substitute for K, so it is thought to generally occur in K-bearing minerals in coal (Swaine, 1990; Tang and Huang, 2004). The Ge-rich coal of the Spetzugli deposit is enriched in Cs (up to 57.2 μg/g), which is adsorbed on to both clay and organic matter (Seredin, 2003b). A study by Dai et al. (2012b) showed that Cs in the Wulantuga coals is also largely associated with illite. The positive correlation coefficients for Csash (0.26), Cs–K2O (0.85), and Cs–Al2O3(0.61), indicate that illite is also the major carrier of Cs in the Lincang coals. (7) Other elements. The elements As, Hg, and Tl have high correlation coefficients with pyritic sulfur (0.84, 0.85, and 0.90 respectively), indicating a pyrite association. Lead and Cd may occur in minor sulfides

(e.g., sphalerite; correlation coefficients of Pb–Zn = 0.61, Cd–Zn = 0.95). The elevated concentrations of elements in Group 3 (As, Sb, Hg, Tl, Pb, and Cd) also appear to have a dominant sulfide affinity. (i) Arsenic. The weighted average concentration of As in the Lincang bench samples varies from 4.56 to 1240 μg/g and averages 156 μg/g, much higher than the average for world low-rank coals (7.6 μg/g; Ketris and Yudovich, 2009). Arsenic is more concentrated in the X1 seam (212 μg/g) than in the Z2 and S3 seams (117 and 115 μg/g, respectively). Arsenic is especially enriched in the middle portion of the S3 and Z2 seams, but is also significantly concentrated in the upper portion of the X1 seam (Fig. 18). Arsenic in coal is generally associated with pyrite, commonly as As-rich inclusions in the pyrite lattice (Coleman and Bragg, 1990; Eskenazy, 1995; Hower et al., 1997; Huggins and Huffman, 1996; Minkin et al., 1984; Ruppert et al., 1992; Ward et al., 1999; Yudovich and Ketris, 2005). Occurrences of organically-associated As have also been reported in some other coals (Belkin et al., 1997; Zhao et al., 1998). Arsenic in the Lincang coals has a mixed organic and pyrite affinity, indicated by the negative correlation coefficient of As–Ash (−0.29) and the high correlation coefficients of As–Sp,d (r = 0.84) and As–Fe2O3 (r = 0.78). Similar mixed modes of pyrite and organic occurrence for As have been reported in the Wulantuga coals by Dai et al. (2012b). (ii) Antimony. The concentration of Sb in the coals varies considerably, from 1.63 to 604 μg/g, with a weighted average of 38.0 μg/g. It is much higher than the average for world low-rank coals (0.84 μg/g; Ketris and Yudovich, 2009). Antimony is especially enriched in the S3 seam (106 μg/g) compared to the Z2 (8.71 μg/g) and X1 seams (38.8 μg/g). Antimony in coal is generally thought to occur in sulfides (Dai et al., 2012b; Swaine, 1990), although some studies have shown that Sb can also be associated with the organic matter (Eskenazy, 1995; Finkelman, 1995). The latter is typical for the high-Ge coal of the Spetzugli deposit, where the Sb concentration is up to 1175 μg/g and the correlation coefficient of Ge–Sb (0.90) is also very high (Seredin, 2003a). Antimony in the Wulantuga coals mainly occurs in pyrite of hydrothermal origin (Dai et al., 2012b). The correlation coefficient of Sb-ash (−0.15) in the present study indicates an organic–inorganic mixed affinity. (iii) Rare earths and yttrium. Elements in Group 4, including the HREE, some MREE (Gd, Tb, Dy), and Y, are negatively correlated with ash yield (Fig. 20), suggesting an organic affinity. The REY in the coal benches of the Lincang Ge ore deposit are characterized by a distinct H-type enrichment (Fig. 21), further indicating the input of hydrothermal solutions (Seredin and Dai, 2012). A number of such solutions may lead to enrichment of heavy rare earth elements in coal, including alkaline terrestrial water (Johanneson and

Fig. 20. Correlation coefficients between ash yield and individual REY.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Zhou, 1997), high pCO2 cold mineral water (Shand et al., 2005), low-temperature (130 °C) alkaline hydrothermal solutions (Michard and Albarède, 1986), and high-temperature (N500 °C) volcanogenic fluids (Rybin et al., 2003). The REY distribution patterns for the Lincang Ge-rich coals are quite different to those of the Wulantuga coals, which are mostly characterized by slight enrichment of LREE (Dai et al., 2012b) and were mainly derived from detrital materials of terrigenous origin, although a small proportion of REY in the upper portion of the coal seam was from hydrothermal solution (Dai et al., 2012b). Additionally, the concentrations of Y and Tb–Lu in the Lincang Ge-rich coals are higher, but those of all REY are lower than their averages for world low-rank coals as reported by Ketris and Yudovich (2009). (See Fig. 21.)

5. Discussion: key role of N2–CO2-mixed hydrothermal solutions A number of studies have shown that the Ge in the Lincang deposit was leached from the associated granite batholith by hydrothermal solutions which then discharged into the peat bogs (Hu et al., 2009; Qi et al., 2004, 2007b). As indicated by Hu et al. (2009), the fluids were probably generated in association with the Miocene Himalayan Orogeny, which also produced the Bangmai Basin itself. Hu et al. (2009) suggest that meteoric waters possibly penetrated downwards through the granite along the NW and E–W trending faults that also formed the basin, and were heated by regional tectonism under an elevated geothermal gradient. The study by Lu et al. (2000), on the other hand, suggested that the Ge was derived from the products of granite weathering in the sediment-source region. If the latter is the case, however, it is difficult to explain the fact that the Ge-rich coal seams occur only in the bottom and not in the middle and upper portions of the coal-bearing sequence, because the entire coal-bearing succession had the same sediment source. For example, the Ge-rich coal seams occur in the lower N21b but not in the middle N31b to upper N61b zones of the Bangmai Formation (Fig. 2). The mineralogical and elemental data of the coals, partings, and roof and floor strata in the present study also show that the formation of the coal-hosted Ge ore deposit was due to leaching of the granite by hydrothermal solutions. Particular observations include: the presence of hydrothermally altered and argillized granite; the quartz–carbonate and carbonate metasomatites in the sedimentary sequence of the Ge ore deposit; the occurrence of minerals (e.g., chalcopyrite, pyrite, galena, epidote, authigenic quartz, and REY-bearing CaCO3(F)) of

(A) 1.6

1.2

0.8

S3-6 S3-7

Z2-2

0.9

Z2-3 Z2-7

0.6

Z2-8

S3-8

Sample / UCC

S3-5

Sample / UCC

0.3

La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu 5

X1-5 X1-6 X1-7

Sample / UCC

X1-4

2

5

Z2-13 Z2-14

5 4

X1-8

3

X1-9 X1-10

2

X1-11

3

X1-13 X1-14

2

X1-15

X1-12

1

1

0

0 La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

Z2-12

0.4

La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

(F)

4

4 3

Z2-10

0.6

La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

(E)

Z2-9

0

0

0

1 0.8

0.2

Sample / UCC

Sample / UCC

(C) 1.4

1.2 S3-4

0.4

Sample / UCC

hydrothermal origin in the deposits; the H-type REY patterns in the Ge-rich coals, in contrast to the M- and H-type REY patterns that characterize a number of host rocks and partings; and the enrichment of Ge– W, Be–Cs–Nb–U, and As–Sb assemblages in the coals. Although the Ge-rich coal seams only occur in the lower N21b and not in the N31b–N61b parts of the sedimentary succession, Ge is significantly enriched in all three coal seams (the X1, Z2, and S3 seams) in the N21b sequence. This reflects a relatively high pressure in the ascending circulation solutions. In view of the enrichment of Ge in the entire section of each individual coal seam, it is deduced that the metalliferous solutions had penetrated the entire peat bog, owing to the relatively high pressure of the solution caused by high gas saturation. Studies of mineralogical and geochemical compositions for the Wulantuga and Spetzugli deposits (Du et al., 2009; Dai et al., 2012b; Seredin and Finkelman, 2008; Zhuang et al. 2009) have also shown that the Ge enrichment for those two ore deposits was caused by ascending circulation hydrothermal solutions that had leached adjacent granite batholiths. Although the Ge source and its enrichment mechanism for all three Ge ore deposits are similar, there are some differences in the enriched-element assemblages that were leached from the granites and then deposited in the organic matter. For example, the enriched-element assemblages for the Lincang, Wulantuga, and Spetzugli deposits, and the Luzanovka Graben of southern Primory are Ge–Be–Nb–W–U, Ge–W, Ge–W, and Ge–W–Mo, respectively. Although Be is also enriched in the Ge-rich coals at both Wulantuga and Spetzugli (25.7 and 67.3 μg/g on average, respectively), the concentration is much lower than that in the Lincang deposit (up to 2000 μg/g and 343 μg/g on average). The different enriched-element assemblages suggest not only different hydrothermal solutions but also different leaching intensity by those solutions from the granite. Although the enriched-element assemblages vary among the different Ge ore deposits, all of the Ge ore deposits are enriched in Ge and W, indicating that an alkaline (pH, ~9.4–9.5) N2-bearing hydrothermal solution of amagmatic origin played at least some role in the enrichment of Ge and W (cf. Krainov, 1973; Seredin et al., 2006). N2-bearing hydrothermal solutions with elevated concentrations of Ge are generated by deep (up to several kilometers) and long-term (up to several million years) circulation of meteoric waters in tectonically active regions, including zones of continental rifting (Seredin et al., 2006). The high concentrations of Ge and W, and in some cases Mo (e.g., Luzanovka Graben), in the circulating hydrothermal solutions are attributed to repeated selective-leaching from the relevant granites. Apart from the high concentrations of Ge and W, and in some cases Mo, such N2-bearing amagmatic hydrothermal solutions contain high Si, but are characterized by low gas contents and low concentrations of U, Be,

(B) 1.5

1.2

(D)

25

1 0 La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

La Ce Pr Nd Sm Eu Gd Tb Dy Y Ho Er Tm Yb Lu

Fig. 21. REY distribution patterns for coal bench samples from Lincang Ge ore deposit. REY are normalized to Upper Continental Crust (UCC) (Taylor and McLennan, 1985).

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

26

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

As, and Sb (Chudaeva et al., 1999; Krainov, 1973; Krainov and Shvets, 1992; Pentcheva et al., 1995, 1997). Thus, it appears that a single alkaline N2-bearing hydrothermal solution derived from circulation of meteoric waters cannot explain the highly enriched elements, such as U, Be, As, and Sb, in the coal-hosted Ge ore deposits. Studies by Pentcheva et al. (1995, 1997) have shown that input of volcanogenic fluid into an alkaline N2-bearing solution can lead to CO2 saturation of the mixed solution and can sharply enhance the reaction between the mixed solution and the host rocks. Compared to the N2-bearing solution, the N2–CO2 mixed solution has a significantly higher content of gas and halogenides, and lower (often near-neutral) pH values. The authigenic minerals, including sulfides, halogenides, and carbonates in coals and host rocks, as well as the carbonate metasomatites in the Lincang Ge ore deposit, indicate a contribution from CO2-bearing chloride–sulfide solutions to mineral development during lignite formation (Seredin, 1997). Intense reactivity between the N2–CO2 thermal waters and the batholith granites is also supported by: the high percentage of authigenic-quartz in the coals; the argrillized and greisenized granites; the quartz–carbonate and carbonate metasomatites in the sedimentary sequence, and their distinctly positive Eu anomalies as well. Consequently, the mixed solution was not only highly enriched in Ge, W, and in some cases Mo, together with some trace elements presumably derived from the magma chamber (e.g., As, Sb, Hg); it also had high concentrations of elements (including Be, Nb, Cs, and U) leached from the host granites. The geochemical and mineralogical data presented above all confirm that Ge was leached from the granite by the mixed N2–CO2 hydrothermal solution and then discharged to the peat bog. Compared to the Lincang coals, the Wulantuga and Spetzugli coals are not significantly enriched in U, Nb, and Be, but they are enriched in As, Hg, Sb, and Tl. The enrichment of Ge–W and As–Hg–Sb–Tl, and the relative depletion of Be–U–Nb, indicate an additional epithermal input for the As–Hg–Sb–Tl enrichment that was independent of the solution for the Ge–W assemblage. In other words, the element associations Ge–W and As–Hg–Sb might have been derived from different hydrothermal sources at different stages of ore formation. 6. Conclusions The coals in the Lincang Ge ore deposit have low random huminite reflectances (0.33–0.48%) and are dominated by huminite-group macerals (N88.5% total huminite), mainly composed of ulminite and attrinite. Funginite is the most abundant inertinite form, and structured inertinite, including fusinite, semifusinite, macrinite, and secretinite, are sometimes also observed. The mineralogical and geochemical anomalies in the Lincang Ge ore deposit are due to the intense leaching of the associated granite by mixed alkaline N2-bearing and volcanogenic CO2-bearing hydrothermal fluids. These mineralogical and geochemical anomalies include: (1) The Ge-rich coals are highly enriched in quartz, and, to a lesser extent, kaolinite, illite, and mica. A hydrous beryllium sulfate phase (BeSO4·4H2O) is present in a number of the coal LTA samples. (2) Several elements, including Be (343 μg/g on average), Ge (1590 μg/g), and W (170 μg/g), are unusually enriched in the Lincang coals, with a concentration coefficient N100; arsenic (156 μg/g on average), Sb (38 μg/g), Cs (25.2 μg/g), and U (52.5 μg/g) are significantly enriched (10 b CC b 100); niobium (28.2 μg/g) is enriched (CC = 8.55); zinc, Rb, Y, Cd, Sn, Er, Yb, Lu, Hg, Tl, and Pb are slightly enriched (2 b CC b 5). (3) The enriched-element assemblages in the Lincang Ge ore deposit are Ge–W–Be–Nb–U and As–Sb. These are different to those in the Wulantuga and Spetugli deposits (both Ge–W and As–Hg– Sb–Tl), which were formed by independent non-mixed hydrothermal fluids at different stages of development. (4) The batholith granites, which served as both the basement for

the coal-bearing sequence and as a source of sediment input, were either altered or argillized by hydrothermal solutions during the period of (Miocene) coal formation. Two types of metasomatites of hydrothermal origin, including quartz– carbonate and carbonate, occur as partings and as host rocks (roof and floor strata) for the coal seams. Acknowledgments This research was supported by the National Key Basic Research Program of China (No. 2014CB238902), the National Natural Science Foundation of China (Nos. 41420104001 and 41272182), and the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT13099). Many thanks are given to Dr. David French and Dr. Mihaela Grigore of CSIRO Energy Technology for help in arranging the addition of the BeSO4·4H2O phase to the Siroquant database. Dr. Ian Graham is thanked for identification of some minerals observed in the granite sample under SEM-EDS. Cody Patrick is thanked for the support of the petrological study. Appendix A. Supplementary data Supplementary data to this article can be found online at http://dx. doi.org/10.1016/j.coal.2014.11.006. References ASTM Standard D2492-02, 2002. Standard Test Method for Forms of Sulfur in Coal. (Reapproved 2007)., ASTM International, West Conshohocken, PA (2007). ASTM Standard D2797/D2797M-11a, 2011. Standard Practice for Preparing Coal Samples for Microscopical Analysis by Reflected Light. ASTM International, West Conshohocken, PA (2011). ASTM Standard D2798-11a, 2011. Standard Test Method for Microscopical Determination of the Vitrinite Reflectance of Coal. ASTM International, West Conshohocken, PA (2011). ASTM Standard D3173-11, 2011. Test Method for Moisture in the Analysis Sample of Coal and Coke. ASTM International, West Conshohocken, PA (2011). ASTM Standard D3174-11, 2011. Annual Book of ASTM Standards. Test Method for Ash in the Analysis Sample of Coal and Coke. ASTM International, West Conshohocken, PA (2011). ASTM Standard D3175-11, 2011. Test Method for Volatile Matter in the Analysis Sample of Coal and Coke. ASTM International, West Conshohocken, PA (2011). ASTM Standard D3177-02, 2002. Test Methods for Total Sulfur in the Analysis Sample of Coal and Coke. (Reapproved 2007), ASTM International, West Conshohocken, PA (2011). ASTM Standard D388-12, 2012. Standard Classification of Coals by Rank. ASTM International, West Conshohocken, PA (2012). ASTM Standard D5987-96, 2002. Standard Test Method for Total Fluorine in Coal and Coke by Pyrohydrolytic Extraction and Ion Selective Electrode or Ion Chromatograph Methods. (Reapproved 2007), ASTM International, West Conshohocken, PA (2011). Belkin, H.E., Zheng, B.S., Zhou, D.X., 1997. Preliminary results on the geochemistry and mineralogy of arsenic in mineralized coals from endemic arsenosis area in Guizhou Province, PR China. 14th Internat. Ann. Pittsburgh Coal Conf. and Workshop Proceedings, pp. 1–20 (CD-ROM). Bostrom, K., 1983. Genesis of ferromanganese deposits — diagnostic criteria for recent and old deposits. In: Rona, P.A., Bostrom, K., Laubier, L., Smith Jr., K.L. (Eds.), Hydrothermal Processes at Seafloor Spreading Centers. Plenum Press, New York, pp. 473–489. Bostrom, K., Kramemer, T., Gantner, S., 1973. Provenace and accumulation rates of opaline silica, Al, Fe, Ti, Mn, Ni and Co in Pacific pelagic sediment. Chem. Geol. 11, 123–148. Carmona-López, I., Ward, C.R., 2008. Composition and mode of occurrence of mineral matter in some Colombian coals. Int. J. Coal Geol. 73, 3–18. Chou, C.-L., 2012. Sulfur in coals: a review of geochemistry and origins. Int. J. Coal Geol. 100, 1–13. Chudaeva, V.A., Chudaev, O.V., Chelnokov, A.N., Edmunds, U.M., Shand, P., 1999. Mineral'nye vody Primor'ya (Mineral Waters of Primorye). Dal'nauka, Vladivostok. Coleman, S.L., Bragg, L.J., 1990. Distribution and mode of occurrence of arsenic in coal. In: Chyi, L.L., Chou, C.-L. (Eds.), Recent Advances in Coal Geochemistry. Geol. Soc. Am. Spec. Pap. vol. 248, pp. 13–26. Dai, S., Ren, D., Chou, C.-L., Finkelman, R.B., Seredin, V.V., Zhou, Y., 2012a. Geochemistry of trace elements in Chinese coals: a review of abundances, genetic types, impacts on human health, and industrial utilization. Int. J. Coal Geol. 94, 3–21. Dai, S., Wang, X., Seredin, V.V., Hower, J.C., Ward, C.R., O'Keefe, J.M.K., Huang, W., Li, T., Li, X., Liu, H., Xue, W., Zhao, L., 2012b. Petrology, mineralogy, and geochemistry of the Ge-rich coal from the Wulantuga Ge ore deposit, Inner Mongolia. China: new data and genetic implications. Int. J. Coal Geol. 90–91, 72–99. Dai, S., Seredin, V.V., Ward, C.R., Hower, J.C., Xing, Y., Zhang, W., Song, W., Wang, P., 2014a. Enrichment of U–Se–Mo–Re–V in coals preserved within marine carbonate successions: geochemical and mineralogical data from the Late Permian

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx Guiding Coalfield, Guizhou, China. Miner. Deposita http://dx.doi.org/10.1007/ s00126-014-0528-1. Dai, S., Song, W., Zhao, L., Li, X., Hower, J.C., Ward, C.R., Wang, P., Li, T., Zheng, X., Seredin, V.V., Xie, P., Li, Q., 2014b. Determination of boron in coal using closed vessel microwave digestion and inductively coupled plasma mass spectrometry (ICP-MS). Energy Fuel 28, 4517–4522. Dai, S., Seredin, V.V., Ward, C.R., Jiang, J., Hower, J.C., Song, X., Jiang, Y., Wang, X., Gornostaeva, T., Li, X., Liu, H., Zhao, L., Zhao, C., 2014c. Composition and modes of occurrence of minerals and elements in coal combustion products derived from high-Ge coals. Int. J. Coal Geol. 121, 79–97. Du, G., Zhuang, X., Querol, X., Izquierdo, M., Alastuey, A., Moreno, T., Font, O., 2009. Ge distribution in the Wulantuga high-germanium coal deposit in the Shengli coalfield, Inner Mongolia, northeastern China. Int. J. Coal Geol. 78, 16–26. Eskenazy, G.M., 1982. The geochemistry of tungsten in Bulgarian coals. Int. J. Coal Geol. 2, 99–111. Eskenazy, G.M., 1995. Geochemistry of arsenic and antimony in Bulgarian coals. Chem. Geol. 119, 239–254. Eskenazy, G.M., 2006. Geochemistry of beryllium in Bulgarian coals. Int. J. Coal Geol. 66, 305–315. Eskenazy, G.M., Valceva, S.P., 2003. Geochemistry of beryllium in the Mariza-east lignite deposit (Bulgaria). Int. J. Coal Geol. 55, 47–58. Finkelman, R.B., 1993. Trace and minor elements in coal. In: Engel, M.H., Masko, S.A. (Eds.), Organic Geochemistry. Plenum Press, New York, pp. 593–607. Finkelman, R.B., 1995. Modes of occurrence of environmentally sensitive trace elements in coal. In: Swaine, D.J., Goodarzi, F. (Eds.), Environmental Aspects of Trace Elements in Coal. Kluwer Academic Publishing, Dordrecht, pp. 24–50. Gayer, R.A., Rose, M., Dehmer, J., Shao, L.-Y., 1999. Impact of sulphur and trace element geochemistry on the utilization of a marine-influenced coal—case study from the South Wales Variscan foreland basin. Int. J. Coal Geol. 40, 151–174. Grigoriev, N.A., 2009. Chemical Element Distribution in the Upper Continental Crust. UB RAS, Ekaterinburg (382 pp. in Russian). Hower, J.C., Robertson, J.D., Wong, A.S., Eble, C.F., Ruppert, L.F., 1997. Arsenic and lead concentrations in the pond creek and fire clay coal beds, eastern Kentucky coal field. Appl. Geochem. 12, 281–289. Hu, R.Z., Bi, X.W., Ye, Z.J., Su, W.C., 1996. The genesis of Lincang germanium deposit: a preliminary investigation. Chin. J. Geochem. 15, 44–50. Hu, R.Z., Bi, X.W., Su, W.C., Qi, H.W., 1999. Ge-rich hydrothermal solution and abnormal enrichment of Ge in coal. Chin. Sci. Bull. 44 (Suppl. 2), 257–258. Hu, R., Qi, H., Bi, X., Su, W., Peng, J., 2006. Geology and geochemistry of the Lincang superlarge Germanium deposit hosted in coal seams, Yunnan, China. Geochim. Cosmochim. Acta 70, A269 (Suppl.). Hu, R., Qi, H., Zhou, M., Su, W., Bi, X., Peng, J., Zhong, H., 2009. Geological and geochemical constraints on the origin of the giant Lincang coal seam-hosted germanium deposit, Yunnan, SW China: a review. Ore Geol. Rev. 36, 221–234. Huang, W., Wan, H., Du, G., Sun, L., Ma, Y., Tang, X., Wu, W., Qin, S., 2008. Research on element geochemical characteristics of coal-Ge deposit in Shengli Coalfield, Inner Mongolia, China. Earth Sci. Front. 15, 56–64. Huggins, F.E., Huffman, G., 1996. Modes of occurrence of trace elements in coal from XAFS spectroscopy. Int. J. Coal Geol. 32, 31–53. Huggins, F.E., Huffman, G.P., Lin, M.C., 1983. Observations on low-temperature oxidation of minerals in bituminous coals. Int. J. Coal Geol. 3, 157–182. International Committee for Coal and Organic Petrology (ICCP), 2001. The new inertinite classification (ICCP System 1994). Fuel 80, 459–471. Johanneson, K.H., Zhou, X., 1997. Geochemistry of the rare earth element in natural terrestrial waters: a review of what is currently known. Chin. J. Geochem. 16, 20–42. Ketris, M.P., Yudovich, Ya.E, 2009. Estimations of Clarkes for Carbonaceous biolithes: world average for trace element contents in black shales and coals. Int. J. Coal Geol. 78, 135–148. Kolker, A., Finkelman, R.B., 1998. Potentially hazardous elements in coal: modes of occurrence and summary of concentration data for coal components. Coal Prep. 19, 133–157. Kortenski, J., Sotirov, A., 2002. Trace and major element content and distribution in Neogene lignite from the Sofia basin. Int. J. Coal Geol. 52, 63–82. Krainov, S.R., 1973. Geokhimiya redkikh elementov v podzemnykh vodakh (Geochemistry of Rare Earth Elements in Groundwaters). Nedra, Moscow. Krainov, S.R., Shvets, V.M., 1992. Gidrogeokhimiya (Hydrogeochemistry). Nedra, Moscow. Kruszewski, Ł., 2013. Supergene sulphate minerals from the burning coal mining dumps in the Upper Silesian Coal Basin, South Poland. Int. J. Coal Geol. 105, 91–109. Lewis, A.J., Palmer, M.R., Kemp, A.J., Sturchio, N.C., 1995. REE behaviour in the Yellowstone geothermal system. 8th International symposium, Water Rock Interaction. Balkema, Rotterdam, pp. 91–94. Li, J., Zhuang, X., Querol, X., 2011. Trace element affinities in two high-Ge coals from China. Fuel 90, 240–247. Li, X., Dai, S., Zhang, W., Li, T., Zheng, X., Chen, W., 2014. Determination of As and Se in coal and coal combustion products using closed vessel microwave digestion and collision/ reaction cell technology (CCT) of inductively coupled plasma mass spectrometry (ICP-MS). Int. J. Coal Geol. 124, 1–4. Lu, J.L., Zhuang, H.P., Fu, J.M., Liu, J.Z., 2000. Sedimentation, diagenesis, hydrothermal process and mineralization of germanium in the Lincang superlarge germanium deposit in Yunnan Province, China. Geochimica 29 (1), 36–43 (in Chinese with English abstract). McLennan, S.M., 1989. Rare earth elements in sedimentary rocks; influence of provenance and sedimentary processes. Rev. Mineral. Geochem. 21, 169–200. Medvedev, Ya.V., Sedykh, A.K., Chelpanov, V.A., 1997. Pavlovsk deposit. Coal Resources of Russia, V-I. Geoinformmark, Moscow, pp. 175–194 (in Russian).

27

Michard, A., 1989. Rare earth element systematics in hydrothermal fluids. Geochim. Cosmochim. Acta 53, 745–750. Michard, A., Albarède, F., 1986. The REE content of some hydrothermal fluids. Chem. Geol. 55, 51–60. Minkin, J.A., Finkelman, R.B., Thompson, C.L., Chao, E.C.T., Ruppert, L.F., Blank, H., Cecil, C.B., 1984. Microcharacterization of arsenic- and selenium-bearing pyrite in Upper Freeport coal, Indiana County, Pennsylvania. Scan. Electron Microsc. 4, 1515–1524. Murray, R.W., Brink, M.R., Jones, D.L., Geriach, D.C., Russ, G.P., 1990. Rare earth elements as indicators of different marine depositional environments in chert and shale. Geology 18, 268–271. Nandi, B.N., Brown, T.D., Lee, G.K., 1977. Inert coal macerals in combustion. Fuel 56, 125–130. Pearson, D.E., Kwong, J., 1979. Mineral matter as a measure of oxidation of a coking coal. Fuel 58, 63–66. Pentcheva, E.N., Van't dack, L., Gijbels, R., 1995. Influence of recent volcanism of the geochemical behaviour of trace elements and gases in deep granitic hydrothermal systems, south Bulgaria. 8th International symposium, Water Rock Interaction. Balkema, Rotterdam, pp. 383–387. Pentcheva, E.N., Van't dack, L., Veldeman, E., Hristov, V., Gijbels, R., 1997. Hydrogeochemical Characteristics of Geothermal Systems of South Bulgaria. Univ. Antwerpen (UIA). Qi, H., Hu, R., Su, W., Qi, L., 2002. Genesis of carboniferous siliceous limestone in the Lincang germanium deposit and its relation with germanium mineralization. Geochimica 31, 161–168 (in Chinese with English abstract). Qi, H., Hu, R., Su, W., Qi, L., Feng, J., 2004. Continental hydrothermal sedimentary siliceous rock and genesis of superlarge germanium (Ge) deposit hosted in coal: a study from the Lincang Ge deposit, Yunnan, China. Sci. China D 47, 973–984. Qi, H., Hu, R., Zhang, Q., 2007a. Concentration and distribution of trace elements in lignite from the Shengli Coalfield, Inner Mongolia, China: implications on origin of the associated Wulantuga Germanium Deposit. Int. J. Coal Geol. 71, 129–152. Qi, H., Hu, R., Zhang, Q., 2007b. REE geochemistry of the Cretaceous lignite from Wulantuga germanium deposit, Inner Mongolia, northeastern China. Int. J. Coal Geol. 71, 329–344. Qi, H., Rouxel, O., Hu, R., Bi, X., Wen, H., 2011. Germanium isotopic systematics in Ge-rich coal from the Lincang Ge deposit, Yunnan, Southwestern China. Chem. Geol. 286, 252–265. Qing, S., 2001. Preservative principals of germanium deposit in Shengli Coal-field of Inner Mongolia and prospecting direction. Coal Geol. China 13 (3), 18–19 (in Chinese with English abstract). Querol, X., Alastuey, A., Lopez-Soler, A., Plana, F., Fernandez-Turiel, J.L., Zeng, R., Xu, W., Zhuang, X., Spiro, B., 1997. Geological controls on the mineral matter and trace elements of coals from the Fuxin basin, Liaoning Province, northeast China. Int. J. Coal Geol. 34, 89–109. Rao, C.P., Gluskoter, H.J., 1973. Occurrence and distribution of minerals in Illinois coals. Ill. State Geol. Surv. Circ. 476 (56 pp.). Ren, D., Zhao, F., Dai, S., Zhang, J., Luo, K., 2006. Geochemistry of Trace Elements in Coal. Science Press, Beijing (556 pp., (in Chinese with English abstract)). Rietveld, H.M., 1969. A profile refinement method for nuclear and magnetic structures. J. Appl. Crystallogr. 2, 65–71. Riley, K.W., French, D.H., Farrell, O.P., Wood, R.A., Huggins, F.E., 2012. Modes of occurrence of trace and minor elements in some Australian coals. Int. J. Coal Geol. 94, 214–224. Ruppert, L.F., Minkin, J.A., McGee, J.J., Cecil, C.B., 1992. An unusual occurrence of arsenicbearing pyrite in the Upper Freeport coal bed, west-central Pennsylvania. Energy Fuel 6, 120–125. Rybin, A.V., Gur'yanov, V.B., Chibisova, M.V., Zharkov, R.V., 2003. Rhenium exploration prospects on Sakhalin and the Kuril Islands. Geodynamics, Magmatism, and Minerageny of the North Pacific Ocean vol. 3, pp. 180–183 (Magadan, in Russian). Seredin, V.V., 1994. The first data on abnormal niobium content in Russian coals. Dokl. Russ. Akad. Nauk 335, 634–636. Seredin, V.V., 1997. Elemental metals in metalliferous coal-bearing strata. Proceedings ICCS'97. DGMK, Essen, pp. 405–408. Seredin, V.V., 2003a. Anomalous trace elements contents in the Spetsugli germanium deposit (Pavlovka brown coal deposit) southern Primorye: communication 1. Antimony. Lithol. Miner. Resour. 38, 154–161. Seredin, V.V., 2003b. Anomalous concentrations of trace elements in the Spetsugli germanium deposits (Pavlovka Brown Coal Deposit, Southern Primorye): communication 2. Rubidium and Cesium. Lithol. Miner. Resour. 38, 233–241. Seredin, V.V., Dai, S., 2012. Coal deposits as a potential alternative source for lanthanides and yttrium. Int. J. Coal Geol. 94, 67–93. Seredin, V.V., Finkelman, R.B., 2008. Metalliferous coals: a review of the main genetic and geochemical types. Int. J. Coal Geol. 76, 253–289. Seredin, V.V., Danilcheva, Yu.A., Magazina, L.O., Sharova, I.G., 2006. Ge-bearing coals of the Luzanovka Graben, Pavlovka brown coal deposit, Southern Primorye. Lithol. Miner. Resour. 41, 280–301. Shand, P., Johannesson, K.H., Chudaev, O., Chudaeva, V., Edmunds, W.M., 2005. Rare earth element contents of high pCO2 groundwaters of Primorye, Russia: mineral stability and complexation controls. In: Johannesson, K.H. (Ed.), Rare Earth Elements in Groundwater Flow System. Springer, The Netherlands, pp. 161–186. Shibaoka, M., 1985. Microscopic investigation of unburnt char in fly ash. Fuel 64, 263–269. Swaine, D.J., 1990. Trace Elements in Coal. Butterworths, London (278 pp.). Sýkorová, I., Pickel, W., Christanis, K., Wolf, M., Taylor, G.H., Flores, D., 2005. Classification of huminite—ICCP System 1994. Int. J. Coal Geol. 62, 85–106. Tang, X., Huang, W., 2004. Trace Elements in Chinese Coals. The Commercial Press, Beijing, pp. 6–11 (24–25 (in Chinese)).

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006

28

S. Dai et al. / International Journal of Coal Geology xxx (2014) xxx–xxx

Taylor, J.C., 1991. Computer programs for standardless quantitative analysis of minerals using the full powder diffraction profile. Powder Diffract. 6, 2–9. Taylor, S.R., McLennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell, London (312 pp.). Taylor, G.H., Teichmüller, M., Davis, A., Diessel, C.F.K., Littke, R., Robert, P., 1998. Organic Petrology. Gebrüder Borntraeger, Berlin (704 pp.). Vleeskens, J.M., Menendez, R.M., Roos, C.M., Thomas, C.G., 1993. Combustion in the burnout stage: the fate of inertinite. Fuel Process. Technol. 36, 91–99. Wang, L.M., 1999. Introduction of the geological feature and explorating of Wulantuga germanium deposit in Xilinguole League. Inner Mongolia. Geol. Inn. Mong. 3, 15–20 (in Chinese with English abstract). Ward, C.R., 1991. Mineral matter in low-rank coals and associated strata of the Mae Moh basin, northern Thailand. Int. J. Coal Geol. 17, 69–93. Ward, C.R., 2002. Analysis and significance of mineral matter in coal seams. Int. J. Coal Geol. 50, 135–168. Ward, C.R., Spears, D.A., Booth, C.A., Staton, I., Gurba, L.W., 1999. Mineral matter and trace elements in coals of the Gunnedah Basin, New South Wales, Australia. Int. J. Coal Geol. 40, 281–308. Ward, C.R., Matulis, C.E., Taylor, J.C., Dale, L.S., 2001. Quantification of mineral matter in the Argonne Premium coals using interactive Rietveld-based X-ray diffraction. Int. J. Coal Geol. 46, 67–82. Wu, W., Mo, R., Wang, Z., 2002. Occurrence features and geological work of germanium resource in Yimin coal field, Inner Mongolia. Inn. Mong. Geol. 1, 27–30 (in Chinese). Yudovich, Ya.E., 2003. Notes on the marginal enrichment of germanium in coal beds. Int. J. Coal Geol. 56, 223–232. Yudovich, Ya.E, Ketris, M.P., 2005. Arsenic in coal: a review. Int. J. Coal Geol. 61, 141–196. Zhang, S.L., Wang, S.Y., Yin, J.S., 1987a. The study of germanium ore in uranium-bearing coal of the Bangmai Basin, Lincang Region, Yunnan province. Uranium Geol. 3 (5), 267–275 (in Chinese with English abstract). Zhang, S.L., Yin, J.S., Wang, S.Y., 1987b. Study on existent forms of germanium in coal, Bangmai Basin, Yunnan. Acta Sedimentol. Sin. 6, 29–41 (in Chinese with English abstract).

Zhao, F., Ren, D., Zheng, B., Hu, T., Liu, T., 1998. Modes of occurrence of arsenic in high-arsenic coal by extended X-ray absorption fine structure spectroscopy. Chin. Sci. Bull. 43, 1660–1663. Zhao, L., Ward, C.R., French, D., Graham, I.T., 2012. Mineralogy of the volcanic-influenced Great Northern coal seam in the Sydney Basin, Australia. Int. J. Coal Geol. 94, 94–110. Zhao, L., Ward, C.R., French, D., Graham, I.T., 2013. Mineralogical composition of Late Permian coal seams in the Songzao Coalfield, southwestern China. Int. J. Coal Geol. 116–117, 208–226. Zhong, D.L., 1998. Paleo-Tethys Orogenic Belt in Western Sichuan and Yunnan. Science Press, Beijing (331 pp., (in Chinese)). Zhuang, H., Lu, J., Fu, J., Liu, J., 1998a. Lincang superlarge germanium deposit in Yunnan province, China: sedimentation, diagenesis, hydrothermal process and mineralization. J. China Univ. Geosci. 9, 129–136. Zhuang, H.P., Lu, J.L., Fu, J.M., Liu, J.Z., Ren, C.G., Zou, D.G., 1998b. Germanium occurrence in Lincang superlarge deposit in Yunnan, China. Sci. China D 41, 21–27 (supplement). Zhuang, X., Querol, X., Alastuey, A., Juan, R., Plana, F., Lopez-Soler, A., Du, G., Martynov, V.V., 2006. Geochemistry and mineralogy of the Cretaceous Wulantuga high-germanium coal deposit in Shengli coal field, Inner Mongolia, Northeastern China. Int. J. Coal Geol. 66, 119–136. Zhuang, X., Querol, X., Alastuey, A., Plana, F., Moreno, N., Andrés, J.M., Wang, J., 2007. Mineralogy and geochemistry of the coals from the Chongqing and Southeast Hubei coal mining districts, South China. Int. J. Coal Geol. 71, 263–275. Zilbermints, V.A., Rusanov, A.K., Kosrykin, V.M., 1936. On the question of Ge-presence in fossil coals. Acad. V.I. Vernadsky—k 50-letiyu nauchnoi deyatel'nosti [Up to 50Anniversary of His Science Activity]. vol. 1. AN SSSR [Acad. Sci. USSR], Moscow, pp. 169–190. Zodrow, E.L., 2005. Colliery and surface hazards through coal-pyrite oxidation (Pennsylvanian Sydney Coalfield, Nova Scotia, Canada). Int. J. Coal Geol. 64, 145–155.

Please cite this article as: Dai, S., et al., Elemental and mineralogical anomalies in the coal-hosted Ge ore deposit of Lincang, Yunnan, southwestern China: Key role of N2–C..., Int. J. Coal Geol. (2014), http://dx.doi.org/10.1016/j.coal.2014.11.006