Size-dependent geochemical signatures of Holocene loess deposits from the Hexi Corridor (China)

Journal of Asian Earth Sciences 35 (2009) 103–136

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Size-dependent geochemical signatures of Holocene loess deposits from the Hexi Corridor (China) Georg Schettler a,*, Rolf L. Romer a, Mingrui Qiang b, Birgit Plessen a, Peter Dulski a a b

GeoForschungsZentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany Key Laboratory of Western China’s Environmental System (Ministry of Education), Lanzhou University, Lanzhou 730000, PR China

a r t i c l e

i n f o

Article history: Received 26 May 2008 Received in revised form 23 December 2008 Accepted 5 January 2009

Keywords: Loess Holocene Hexi Corridor Chemical and isotopic composition

a b s t r a c t Well dated Holocene loess sequences from uplifted river terraces at the northern margin of the Tibetan Plateau are characterised by their chemical, grain size, Sr isotope, and their oxygen and carbon isotope composition of the carbonate fractions. Prevailing wind directions suggest the source areas of the loess to be largely restricted to dry lands in Northwest China and the deserts north to the Hexi Corridor (e.g. Badain Jaran and Tengger Desert) which receive fluvial input by rivers draining the Qilian Shan. The dry lands of Northwest China are one of the most important dust source areas globally. Local arid conditions make the investigated loess sequences insensitive to element leaching. The loess is characterised by a relatively narrow variation of 87Sr/86Sr (0.7139–0.7164). The 87Sr/86Sr ratios of surface- and carbonate-bound Sr are similar (0.7114 and 0.7111) and lower than those of silicate-bound Sr (63–2 lm fractions: 0.7196, <2 lm fractions: 0.7247). Since the clay fractions have higher CaCO3 contents than the silt fractions, the isotopic contrast between the silicate debris of clay and silt size is camouflaged in the bulk compositions of these grain size fractions. Oxygen isotope and chemical compositions of clayand silt-sized carbonate particles differ significantly. Silt-sized loess carbonates formed authigenically and they are largely present as coatings of silicate grains, whereas clay-sized carbonate particles are of remote provenance and precipitated under evaporative conditions. In line with further implications from the multi-proxy study, upward trends in the composition of the pedogenic carbonate document climate change to drier conditions after the mid Holocene. Ó 2009 Elsevier Ltd. All rights reserved.

1. Introduction Geological, geomorphic and climatic conditions in central Asia have led, closely correlated with palaeoclimate change, to substantial long range transport of dust for at least the last 2.5 Ma. Loess sequences of more than 100 m accumulated by aeolian deposition (e.g. Kukla, 1987). Since mineral aerosols in the atmosphere and dust deposition on snow and ice affect the radiation balance of the earth, dust production in the arid and semi-arid regions of Asia represents an important climate factor itself. Palaeochanges in the deposition of Asian dust in terms of accumulation rates and grain size variations are recorded in ice cores (e.g. Dunde ice core, Qilian Shan, Yang et al., 2006) and in marine (e.g. northwest Pacific, Rea and Leinen, 1988) and lacustrine sediments (e.g. Northeast China, Schettler et al., 2006c). Dust records represent, i.a., archives for palaeoclimatic change in terms of aridity in the source regions of the dust, palaeo-wind strengths, directions of palaeo-wind fields, and precipitation frequency. However, there is no simple correlation between climate and dust transport

* Corresponding author. E-mail address: [email protected] (G. Schettler). 1367-9120/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.jseaes.2009.01.003

(e.g. Grunert and Lehmkuhl, 2004). Silt-sized debris is the major particle fraction of loess. Mechanisms that produce silt particles include the direct release from parent rocks, glacial grinding, fluvial and aeolian abrasion, crushing, and salt, frost and chemical weathering (Pye, 1995 and references therein). The importance of these mechanisms and the importance of various dust source regions to a certain dust accumulation site are likely to have varied in the past. The particle flux from Alpine mountain regions with high relief energy into dry lands is supposed to be the major primary supplier of clay- and silt-sized debris for atmospheric transport. Glacial grinding is the key physical process that produces these materials (Pye, 1987 and references therein). On land surfaces without significant vegetation, which provides shelter, fine particles are highly susceptible to wind erosion. Since fine particles in deserts are almost completely removed by wind erosion from the earth’s surface it is hard to directly sample representative material in arid and hyperarid source areas of dust. Coarse mineral aerosols transported during frequent large dust outbreaks in spring and early summer provide only fragmentary information on aeaolian deposition and do not consider finer loess components that are continuously accumulated throughout the year (e.g. Prins et al., 2007 and references therein).

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Holocene loess deposits from the Qilian Shan (Northern Tibetan plateau, Fig. 1) offer the possibility to characterise aeolian deposits of global significance with sources in Northwest China. The loess records may have received variable inputs of (i) pristine glacial materials transported by the river discharge into arid basins, (ii) lacustrine sediments of dry lake beds, and (iii) remobilized former aeolian deposits. Chemical, mineralogical and isotope signatures of dust in natural monitors carry information about its source region. Initial geochemical signatures of the mineral debris, however, can be modulated by solid/water interaction during fluvial transport, subaquatic diagenetic processes or pedogenesis up to the atmospheric uptake and aeolian transport to loess accumulation sites. The climatic conditions at the investigated sites make loess profiles unique for the purpose of the characterisation of initial geochemical signatures of the dust deposits. Seepage of rainfall is negligible because of the very low rainfall during the rainy season and a high potential evapotranspiration. These conditions do not favour the leaching of elements released by chemical weathering towards deeper horizons. We assume that seasonal wetting affects the upper 10 cm (ca. 1000 years) of the loess only, whereas deeper loess sections are kept permanently dry. The peaks of Qilian Shan (Chinese ‘Shan’ = mountain) rise up to more than 5000 m asl. The mountains channel the atmospheric transport of dust along the Hexi Corridor to the Loess Plateau and farther to the east up to the North Pacific Ocean (see

Derbyshire et al., 1998). The dust is in parts trapped in uplifted river valleys that drain the Qilan Shan to the north. Potential source regions of the aeolian deposits in these valleys are the large arid basins of northwestern China, which receive fluvial influx from Tian Shan, Kunlun Shan, and Altun Shan, and to the deserts and semi-deserts north of Qilian Shan (e.g. Alahan Shamo). The Tian Shan should represent a natural barrier for the dust transport from the arid lands of Kazahstan. The Qilian Shan itself hinders significant aeolian transport of soil particles from the Qaidam Basin towards the Hexi corridor (Fig. 1). This study was carried out to characterise the Holocene aeolian deposits by grain size, chemical and Sr isotope composition, and by the oxygen and carbon isotope compositions of their carbonates. We assess (i) possible changes in the geochemical and isotopic dust characteristics during the last 10,000 years, (ii) the chemical and isotopic contrast between the clay- and silt-sized loess fractions to elucidate possible effects of grain size fractionation during atmospheric transport on the bulk composition of the dust, (iii) the isotope composition of NH4Cl exchangeable, carbonate-bound, and residual Sr for the clay- and silt-sized loess fractions. The latter illustrates how the initial Sr isotope composition of the bulk dust might get altered by grain size fractionation and carbonate dissolution. To ensure representative results, loess profiles from three river valleys along the Hexi Corridor were sampled for analyses.

Fig. 1. Geomorphological map of China with locations referred in the text.

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

2. Study sites and sampling The Hexi Corridor is a Cenozoic foreland basin system to the Qilian Shan that forms a more than 700 km long NW-stretching active fold- and thrust-belt along the northern margin of the Tibetan Plateau (Tapponnier et al., 1990; Meyer et al., 1998). The latest tectonic event at 0.14 Ma is associated with the uplift of alluvial fans along the foreland of the Qilian Shan (Song et al., 2001; Fang et al., 2005). The incision of rivers draining the Qilian Shan to the north and the formation of terraces began (Yang et al., 1998; Li et al., 1999; Meyer et al., 1998). Such river terraces are well-preserved at the sites of Shiyou He (Chinese ‘He’ = river), Baiyong He and Hei He valleys. They are covered by loess of different thickness (from 0.33 to 2.1 m) (Stokes et al., 2003; Küster et al., 2006). The Shiyou He incised in uplifted rather plane river terraces of a valley filled with fast cemented Quaternary conglomerates. The river-facing margin of the lowest (youngest) terraces is formed by vertical cliffs of several ten metres height above the narrow river bed which consists of well-rounded river brash. Fine mineral particles are efficiently flushed away by the fast-flowing Shiyou He. Significant aeolian upward transport from the low-laying narrow modern river on the uplifted river terraces is unlikely for such a geo-morphological setting. The few decimetre thick Holocene loess sequences cover coarse-grained (old) river deposits. There is no evidence for the deposition of material from higher grounds by surface run-off on the uplifted plane river terraces under investigation. The Baiyong He is located ca. 20 km east of the Shiyou He. Three well-preserved terraces covered by loess are not dated. The Hei He is located ca. 200 km southeast of Shiyou valley. The six terraces on the hanging wall were formed via incision of the Hei He and the Red Sand He due to an active thrust fault east to the Hei He (Li et al., 1995; Stokes et al., 2003). On the lower block of the fault, the Hei He has developed four terraces (Li et al., 1995) that are well-preserved and covered by undisturbed loess deposits (Stokes et al., 2003). Modern mean annual precipitation of the IAEA/WMOGNIP1 site Zhangye (38.93° N, 100.43° E, 1483 masl) reaches 135 mm (see Johnson and Ingram, 2004); mean annual precipitation of the nearby Yumen city is 62.2 mm (pers. information local meteorological station). With the exception of limited areas used for irrigation agriculture, vegetation along the piedmont of the Qilian Shan and on the uplifted river terraces is dominated by desert steppe plant associations (e.g., Ephedra, Artemisia, Stipa, Wang, 1988). The terraces of the sampling sites are currently used for pasture farming (sheeps). Restricted terrace areas of Shiyou He and Baiyong He, however, were partially used as farmlands in the 1960s. The fields and a small settlement above the Baiyong He have been abandoned after a short time. Ubiquitous loess cover on the flat river terraces enabled to select sampling sites without signs for farming activities. Loess profiles were continuously sampled at 10-cm slices on uplifted river terraces from the Shiyou He, Baiyong He and Hei He valleys. The profiles were dated by optically stimulated luminescence (OSL) measurements by Küster et al. (2006) and Stokes et al. (2003), respectively. The loess sequences were accumulated during the entire Holocene. Küster et al. (2006) argue that absence of significant vegetation did not sustain loess accumulation under colder climatic conditions before. Profiles represented by samples S1-8 (N 39°45.680 , E 97°31.400 ) and S9-15 (N 39°46.110 , E 97°31.900 ) were taken from terrace T3 and T2a, respectively, at the right downstream river side of Shiyou He (see Küster et al., 2006 for location). Further profiles were taken from loess covered river terraces in the Baiyong He valley (samples S16-26: N

1

GNIP: Global Network of Isotopes in Precipitation.

105

39°39.530 , E 97°40.200 ) and in the Hei He valley (samples S27– 40: N 38°47.930 , E 100°11.030 ).

3. Analytical methods Quantification of grain size composition into particle size classes >250 lm, 250–125 lm, and 125–63 lm was gravimetrically performed by wet sieving of large sample aliquots (20 g) using deionized water (Millipore, 18.2 MX). Further discrimination of the <63 lm particle fraction into silt (63–2 lm) and clay (<2 lm) was done by repeated centrifugation (1 min, 1000 rpm) and re-suspension until clear supernatants were obtained. Grain size distributions of the silt fractions were determined using a Laser particle analyser (Malvern, Series 2600). Large sample aliquots were used to obtain representative data for the coarse particle fractions and sufficient amounts of fine materials for chemical analyses. Separation of the <2 lm particles from several litres of collected suspensions was done by high pressure filtration (cellulose acetate membrane filter, 1 lm, 142 mm, Macherey-Nagel). The obtained silt and clay fractions were dried at 60 °C before chemical analyses. The preparation of the <2 lm and 63–2 lm grain size fractions for chemical analyses involved wet sieving through metal sieves. Beside Fe as the major alloy constituent, the used metal sieves (alloy 316L) contained 16.7% Cr, 13.0% Ni and 2.3% Mo (pers. communication, Fa. Retsch). Particles <2 lm easily passed the applied minimum mesh size of 63 lm and had only brief contact with the metal fibres. Significant sample contaminations by metal abrasion during wet sieving would affect at most coarse silt particles preferentially and would be most sensitively recorded by analytical data for Mo which has the lowest abundance of the three trace elements in the silt fractions (ca. 0.1 lg/g). After a HNO3/HClO4/HF/HCl-decomposition of 0.25 g solid sample, the determination of major and minor elements, including phosphorus and sulphur, was carried out by ICP-AES (Iris, Thermo Elemental) and external calibration (Schettler et al., 2006a,b). Selected trace elements were measured by ICP-MS (ELAN 5000, Perkin Elmer). Conditions for ICP-MS measurements closely followed Dulski (2001). Inorganic carbon was coulometrically determined after decomposition with hot phosphorus acid (Coulomat 702, Ströhlein). Preparation of silt- and clay-sized sample fractions on the basis of the above described wet procedures is likely associated with the release of weakly bound elements at the surface of mineral grains. The amounts of weakly bound major cations (Ca, Na, Mg, K) and Sr were therefore determined by ICP-AES after sequential leaching of bulk loess samples with 1 M NH4Cl solution. We performed leaching of 0.2–0.25 g weight aliquots of the silt and clay fractions with 30 ml 8 M acetic acid (HAc) to determine carbonate-bound Ca and Sr by ICP-AES. In order to get a defined sample status, the individual grain size fractions were subjected to NH4Cl-leaching before treating with HAc. The HAc leachates were evaporated in teflon tubes after addition of 0.5 ml HClO4. ICP-AES and ICP-MS analyses were performed in hydrochloric acid solution afterwards. Strontium isotope mass balances are applied considering the distribution of NH4Cl and HAc leachable Sr between clay and silt. We determined the Sr isotopic composition of three kinds of samples by thermal ionization mass spectrometry: (i) NH4Cl leachates of bulk loess samples, (ii) HAc leachates of the silt and clay fractions, which predominantly contain carbonate-bound Sr, and (iii) the solid residues of the clay and silt fractions after sequential dissolution with HAc. The residues were dissolved in concentrated HF for 4 days on a hot plate. After evaporation of HF, the sample was dissolved in 6 M HCl and dried again. Strontium was separated using a Sr specific resin (Horwitz et al., 1992), which is available in

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a ready to use form from Eichrom Technologies, following the procedure described by Pin and Basso (1992). The sample is loaded onto the resin in 3 M HNO3 and Sr is eluted with 0.05 M HNO3. The eluates contained minor amounts of organic molecules that had been released from the resin. These organic substances enhanced the formation of crusts on the Ta-filaments, which hampered the release and ionization of Sr from the filament and, thus, typically resulted in very high run temperatures. Therefore, these organic components were destroyed by wet oxidation before loading the Sr on the filaments. Samples were dissolved in 0.5 ml 6 N HCl and evaporated to dryness at 70 °C after addition of 2 ml H2O2 (35%, Merck Suprapur). The Sr was loaded with H3PO4 on degassed Ta single-filaments and ionized at 1200 to 1260 °C. The isotopic compositions of the three Sr fractions were analysed on a Micromass VG54 Sector and a Finnigan MAT 262 multi-collector mass spectrometer operated in a dynamic multi-collection and in a static multi-collection mode, respectively. The data were normalized using 86Sr/88Sr = 0.1194. Analytical uncertainties for the 87 Sr/86Sr ratios are reported at the 2rm level. The repeated measurement of the Sr reference material SRM NBS 987 gave 87 Sr/86Sr = 0.710256 ± 10 (2r, n = 14 analyses) for the triple-jump

experiment and 87Sr/86Sr = 0.710281 ± 10 (2r, n = 12 analyses) for the static experiment. All measurements were adjusted to 87 Sr/86Sr = 0.710256 for SRM 987. The stable isotope compositions (oxygen and carbon) of carbonates were analysed using a Finnigan GasBench II connected with a DELTAplusXL mass spectrometer. Between 0.2 and 1 mg sample were loaded into 10 ml vials depending on the pre-analysed carbonate contents. After flushing with He, CO2 was released by reaction with H3PO4 (100%) at 75 °C for 60 min. The entire analytical procedure closely follows Spoetl and Vennemann (2003). Calibration is based on the reference samples NBS19 and NBS18. Isotope compositions are given relative to the VPDB standard in delta notation (d13Ccarb, d18Ocarb). The achieved external precision was better than 0.06‰ for d13Ccarb and <0.08‰ for d18Ocarb. 4. Data presentation Analytical data on the bulk geochemical composition and the chemical composition of HAc leachates are presented in table form as Appendices. The variation of major and trace element concentrations within the individual loess sequences is quantified by nor-

Table 1 Grain size compositions. (lm) Smpl.

(cm)

Shiyou He S1 S2 S3 S4 S5 S6 S7 S8

N 39° 45.680 0–10 20-Oct 20–30 30–40 40–50 50–60 60–70 70–80 Average N 39° 46.110 0–10 20-Oct 20–30 30–40 40–50 50–60 60–70 Average N 39° 39.530 0–10 20-Oct 20–30 30–40 40–50 50–60 60–70 70–80 80–90 90–100 Average N 38° 47.930 0–10 20-Oct 20–30 30–40 40–50 50–60 60–70 70–80 80–90 90–100 100–110 110–120 120–130 130–140 Average

Shiyou He S9 S10 S11 S12 S13 S14 S15 Baiyong He S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 Hei He S27 S28 S29 S30 S31 S32 S33 S34 S35 S36 S37 S38 S39 S40

>250 (%) E 97° 31.400 2 0.5 0.4 1 0.7 0.8 1.3 3.2 1.2 E 97° 31.900 2.8 1 0.9 0.4 0.8 4 8.1 2.6 E 97° 40.200 3.8 3.4 0.6 0.1 0.3 0.1 0.2 0.4 1.5 3.1 1.4 E 100° 11.030 0.1 0.8 0 4.8 0.4 0.1 0.2 0.5 0.1 0.3 0 0.1 0.2 1.6 0.3

250–125 (%)

125–63 (%)

63–2 (%)

<2 (%)

Silt/clay

1.7 1.3 0.7 1.2 1.5 1.1 1.6 2.1 1.4

8.4 9.2 7.9 6.8 8.4 8 10.5 12 8.9

70.9 70.5 71.6 72.1 71.6 73.5 72.2 66.9 71.2

16.9 18.6 19.5 18.9 17.8 16.7 14.5 15.8 17.3

4.2 3.8 3.7 3.8 4 4.4 5 4.2 4.1

1.7 1.3 1 0.9 1 2.3 2.1 1.5

10.3 9.3 7 7.5 7.2 9.7 6.6 8.2

71.5 72.5 72.5 73.6 72.2 69.6 67.4 71.3

13.7 15.8 18.6 17.7 18.8 14.5 15.9 16.4

5.2 4.6 3.9 4.2 3.8 4.8 4.2 4.4

3.2 5 1.4 0.4 0.4 0.3 0.5 0.8 2.1 3.8 1.8

11.3 13.3 9.8 5.9 5.1 4.2 4.1 5.3 7.4 10.5 7.7

64.1 61.4 67.4 72.2 74.2 71.9 70.5 67.6 68.2 64.7 68.2

17.6 16.9 20.7 21.3 20 23.5 24.7 25.8 20.7 17.9 20.9

3.6 3.6 3.2 3.4 3.7 3.1 2.9 2.6 3.3 3.6 3.3

0.8 1.2 1.1 5.2 2.4 3 4.1 5.1 6.1 2.7 2.2 3.3 5 8 4.4

8.5 8 7.9 11.9 15.9 18.7 22.9 21.7 29.2 17.6 19.3 21.3 29.3 32.8 23.6

71.4 72.5 68.1 61.9 60.5 64.4 62.6 61.8 55.8 65.6 66.7 64.1 55.7 46.7 60.4

19.2 17.6 22.9 16.3 20.9 13.9 10.2 10.9 8.8 13.9 11.8 11.2 9.8 10.9 11.3

3.7 4.1 3 3.8 2.9 4.6 6.1 5.7 6.4 4.7 5.7 5.7 5.7 4.3 5.4

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10

Vol-%

8

HAc-residues bulk silt

6 4 2 0 1

10

100

grain size classes (µm) Fig. 2. Loess profile S9-15 (Shiyou He), average grain size distribution of bulk silt samples and of the silicate residues after leaching with HAc.

from Shiyou valley (samples: S1-15) are characterised by a polymodal grain size distribution which is maintained in the silicate residue after the sequential dissolution of carbonate with acetic acid (Fig. 2). The contents of the major elements Al, Ti, Fe, Mg, Na, K in the silt fractions of the individual loess profiles are relatively homogeneous and show relative standard deviations (RSDs) that typically fall below 5% (Appendix Tables A.1–A.4-2). The contents of these elements show slightly higher variability in the clay fractions (7%). In particular, the scatter of Mn is much higher in the clay fractions than in the silt fractions. The relatively high variability of Mn, Ca, CO3, Sr, P2O5 in the clay and silt fractions most likely reflects element re-distribution in the source regions of the aeolian deposits, such as carbonate precipitation/dissolution, apatite dissolution and precipitation of phosphates, sulphide oxidation and precipitation/dissolution of gypsum. Variable aeolian deposition of chemical sediments and variations in the provenance of the pre-

0.3

(a) Na 2O/Al2O3

malization versus their average concentration values in the corresponding loess sequences. Appendix Table A.2 includes data for the composition of the Upper Continental Crust (UCC) and a Post-Archean Australian Shale average (PAAS) that were used for normalizations (Rudnick and Gao, 2004; Taylor and McLennan, 1985). Graphical data presentation largely comprises average concentration values for the individual loess sequences. In few cases, selected parameters showing depth trends are also presented in diagrams. Analytical data include the complete profiles from the top to the base of the Holocene loess sequences at 10 cm resolution. We assume that the loess accumulation roughly started at the same time (Küster et al., 2006) and continued until recently at all study sites, though at various accumulation rates. For comparison of individual depth profiles, geochemical data are plotted versus normalized depths (depth/depthmax). Graphical data presentation is based on several approaches that seemed appropriate to point out specific geochemical signatures of the investigated Holocene loess sequences from Qilian Shan, (i) to demonstrate differences in the geochemical signatures of the loess sections from the Shiyou He, Baiyong He and the Hei He valley, (ii) to show the variation range of the chemical loess composition related to variable mix between silt- and clay-sized particles, and (iii) to identify possible coinciding changes in the composition of the loess sequences S1-8, S9-15, S16-26, and S27-40 versus depth (age) that might be related to climate change. The use of the conservative major element Al for normalization enables to characterise the siliciclastic loess components independently from variable dilutions by CaCO3 and quartz. Assuming in a first approach that the loess carbonate is largely authigenic in character, chemical analyses were recalculated on a H2O- and CO2-free basis for comparison with loess of other provenances and data for continental crust composition. Clay/silt concentration ratios were calculated to estimate variations in the composition of the Qilian Shan loess related to a variable mix of the grain size end members silt and clay. Rare earth element concentration data are normalized to PAAS on a CaCO3-free base. The relative enrichment of middle rare earth elements (MREEs) is quantified by a modified Eu-index (Eu/Eu** = EuN/(0.5  NdN + 0.5  TbN). A full analytical data set is not available for all samples. Mean bulk concentration data of the loess sequence S9-26 are therefore based on the samples S9–S25 and no stable isotope data of the silt-sized carbonate fraction of profile S27-40 are presented. ICPAES and ICP-MS measurements were validated by analysing three independent digestions of six international reference materials (Appendix Table A.6). Furthermore, a detailed Ca budget, including a comparison of analysed total Ca contents and calculated normative carbonate-bound Ca contents, is graphically presented for the loess samples S9-26 (Appendix Fig. A.1).

0.2 silt x clay

0.1

Upper Continental Crust (UCC) composition after (Rudnick and Gao, 2004) UCC (Taylor and McLennan, 1985) Mean Continental Crust (MCC) composition (Taylor, 1964) MCC composition (Ronov and Yaroshevskiy, 1976) Loess Central Loess Plateau (Ding et al., 2001)

5. Results 5.1. Grain size and chemical composition In all four loess profiles, silt (63–2 lm) is the dominant particle component. Coarser particles (>125 lm) account for a few weight percent only (Table 1). The loess profile from Hei He shows overall higher sand contents (mean: 23.6 wt-%) than the other profiles (means: 7.7–8.9 wt-%). Clay (<2 lm) represents the second major component in the loess from Shiyou He and Baiyong He. The silt/ clay ratios of all profiles vary within a narrow range (means: 3.3–5.4). There are no systematic depth (age) trends in the grain size compositions with the exception of the Hei He profile which shows increased sand contents and an increase in the silt/clay ratio below 0.5 normalized depth. The silt fractions of loess samples

MgO/Al2O3

(b) R2(silt)= 0.44

0.4

x R2(clay)= 0.04

0.2

0.1

0.2 K 2O/Al2O3

0.3

Fig. 3. (a,b) Clay and silt fractions of samples S1-40. Plots of Na2O/Al2O3 and MgO/ Al2O3 versus K2O/Al2O3 (mass ratios), reference data shown inside the diagrams. (see above-mentioned reference for further information.)

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2

Average last glacial loess L1-(1-5), Xifeng section (CLP) (Jahn et al., 2001) Average last glacial loess L1-5 (CLP) (Ding et al., 2001) Loess Luochuan L1-L7 (CLP) (Gallet et al., 1996)

(a)

1

Siltavs (S1-8, S9-15, S16-25) Siltavs (S27-40) Na2O Zr SiO2 Ba Sr Al2O3 Cr TiO2 Co Ho K2O Sc Y Tb F eO Ce P2O5 Pr La Er Be Nd V Lu Ni Dy Tm Eu Yb Sm Gd MnO Th U Zn Rb M gO Pb Mo Cu Li Cs C aO

0

ME sam ple/ME UC C

3

2

(b) Loess Xifeng (CLP) L1-(1-5) (Jahn et al., 2001)

Clayavs (S1-8, S9-15, S16-25) Clayavs (S27-40)

1 3

(d )

Na2O Zr SiO2 Ba Sr Al2O3 Cr TiO2 Co Ho K2O Sc Y Tb F eO Ce P2O5 Pr La Er Be Nd Loess Changchun (clay/UCC) V Lu Ni Dy Tm Eu Yb Sm Gd MnO Th U Zn Rb M gO Pb Mo Cu Li Cs C aO

0

2

Average of non-calcareous loess from Changchun silt clay Average silt fraction of sand dunes from Horqin Shadi Global average loess ( McLennan, 2001) Average loess L1-5 (CLP) (Ding et al., 2001)

1

Co K2O P 2O 5

Zn

MnO

Na2O

0

(c)

0

Pb Mo MgO

1 2 S1-S25 (clay/UCC)

2

Cu

3

1

Zn Rb M gO Pb Mo Cu Li Cs C aO

Th U

Gd MnO

Yb Sm

Tm Eu

Dy

Ni

V Lu

Be Nd

Na2O Zr SiO2 Ba Sr Al2O3 Cr TiO2 Co Ho K2O Sc Y Tb F eO Ce P2O5 Pr La Er

0

Fig. 4. (a,b) UCC-normalized mean chemical compositions of silt and clay for the loess sequences S1-8, S9-15, S16-25 and S27-40 on a CO2- and H2O-free basis, H2O = 2% and 4% considered for the silt and clay fractions, respectively, SiO2 calculated as difference to 100%, UCC composition after Rudnick and Gao (2004). Horizontal dashed line: MEsample/MEUCC = 1.5. Normalized reference data from other Chinese sites given inside the diagrams (a–c), data for Horquin Shadi and Changchun, this study. (d) Correlation between UCC-normalized element concentrations of clay fractions from the Qilian Shan loess and clay fractions of non-calcareous loess from Changchun.

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

cursor rocks also may contribute to this heterogeneity. Normalization of element concentrations versus their average in the individual grain size fractions does not show systematic variations with depth. The clay fractions are more calcareous (means clay: 9.2– 16.7 wt-%, means silt: 7.8–11.3 wt-% CO3) and show 3 to 4 times higher Stotal contents than the silt fractions. Clay- and silt-sized samples define separate data clusters at similar MgO/Al2O3 ranges in the MgO/Al2O3–K2O/Al2O3 diagram (Fig. 3b). The silt-sized samples document an inverse correlation between K2O/Al2O3 and MgO/Al2O3 (R2 = 0.44) reflecting variable contributions by a Mg-rich (chlorite) and a K2O-rich component (orthoclase) (cf. mineral composition of HAc residues, Section 5.3.). The obtained MgO/Al2O3 ratios (Fig. 3b) fall in the MgO/ Al2O3 variation range of loess samples from the Loess Plateau (Ding et al., 2001). The Na contents of the clay fractions are strongly depleted relative to UCC (Figs. 3a and 4b). Recalculated Ca concentra-

tions on a CO2- and H2O-free basis exceed Ca estimates for the UCC composition 2–3.2 times for the silt, and 2.2–5.3 times for the clay averages (Siltavs, Clayavs) of the loess profiles as also documented for bulk loess from the CLP by Jahn et al. (2001). This distinct CaO excess of the loess does not reflect authigenic formation of pedogenic carbonate alone. The UCC-normalized major and trace element compositions of the silt fractions (data after Rudnick and Gao, 2004) roughly fall in the variation range of loess samples from the CLP (data from Jahn et al., 2001, Fig. 4a). However, our data (2– 63 lm fractions) show lower values for Zr, Y and the HREEs. Trace elements that are enriched relative to UCC by factors >1.5 in the clay fractions include (i) U and Mo, which are forming soluble oxy-anions, (ii) the transition elements Zn, Pb and Cu, which show enhanced solubility of their divalent cations, and (iii) the alkali elements Li, Rb, Cs, which occur as mono-valent cations in natural waters.

(c)

0.2 0.4 1.6 1.4

(a)

--+-- Average last glacial loess L1-(1-5), Xifeng section (CLP) (Jahn et al., 2001)

0.6

- - Average silt fractions non-calcareous loess Changchun (this study)

0.8

silt fractions

normalzide depth

silt fractions 1.2

REE sample/REE PAAS

1 0.8

(b) 1.4

+ S1-8, Shiyou He S9-15, Shiyou He S16-25, Baiyong He S27-40, Hei He

1 0.9

1

(d)

0.2 0.4

clay fractions

0.6 0.8 1

1.2

0.9 1

-

Ce/Ce* 1

Average last glacial loess L1-5 (Ding, et al., 2001)

--- Average paleosol S1 (Ding, et al., 2001) - - Average clay fractions non-calcareous loess Changchun (this study)

0.8 0.6

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

REE HAc/REE bulk

clay fractions 0.4 0.3

(e) clay fractions

0.2 0.1

silt fractions

0 La Pr Eu Tb Ho Tm Lu Ce Nd Sm Gd Dy Er Yb Fig. 5. PAAS-normalized averaged REE concentrations of the silt (a) and clay fractions, (b) calculated on a CaCO3-free basis, REE concentration data used for normalization after Taylor and McLennan (1985), reference data shown inside the diagrams. (c,d) Depth profiles of Ce/Ce*, note that the Ce/Ce* decrease of the Hei He profile at 0.5 normalized depth documents changes in the provenance of the clay-sized aeolian influx and (e) Diagram demonstrating the average enrichment of MREEs and the decrease of Ce/Ce* in HAc leachates relative to the mean bulk compositions of the clay and silt fractions (loess profiles S9-15 and S16-25), same sample marks are used throughout all diagrams.

110

Table 2 Relative standard deviations (RSD) and depth trends (Pearson corr. coefficient R) of ME/Al2O3 mass ratios. ME

S1-8 Shiyou He

S9-15 Shiyou He

S16-25 Baiyong He

S27-40 Hei He

S1-8 Shiyou He

S9-15 Shiyou He

S16-25 Baiyong He

S27-40 Hei He

RSD (%)

RSD (%)

RSD (%)

RSD (%)

RSD (%)

RSD (%)

R

RSD (%)

R

RSD (%)

R

1.0 8.5 3.6 26.0 7.4 1.8 2.5 12.1 23.0 1.3 1.2 1.7 1.7 6.6 2.2 4.4 8.2 2.0 1.0 5.9 1.5 8.8 2.5 3.9 4.8 3.7 5.5 5.6 6.8 6.5 6.2 6.7 5.2 5.3 4.7 5.8 4.1 4.4 3.4 3.2 8.6

0.54 0.83 0.41 0.68 0.17 0.48 0.40 0.03 0.50 0.47 0.44 0.74 0.36 0.20 0.60 0.71 0.69 0.44 0.67 0.80 0.55 0.48 0.37 0.22 0.89 0.89 0.83 0.82 0.83 0.80 0.81 0.86 0.84 0.92 0.87 0.84 0.84 0.93 0.27 0.84 0.36

1.3 8.2 7.1 19.1 7.6 1.2 3.3 10.8 24.7 1.4 1.5 0.9 1.4 4.9 3.0 3.9 7.8 3.9 1.6 3.7 2.4 14.3 5.0 4.3 2.0 1.5 2.1 2.6 3.5 2.6 4.1 4.5 4.1 4.2 3.6 3.7 2.9 2.9 4.8 3.0 7.4

0.76 0.43 0.46 0.55 0.24 0.02 0.32 0.43 0.76 0.40 0.09 0.12 0.55 0.15 0.12 0.38 0.43 0.76 0.18 0.65 0.73 0.79 0.89 0.10 0.12 0.48 0.41 0.52 0.57 0.54 0.63 0.61 0.61 0.49 0.63 0.67 0.65 0.43 0.06 0.13 0.58

2.6 9.6 9.9 20.9 9.4 2.4 7.0 11.5 35.4 5.0 2.0 3.0 1.5 5.5 6.6 7.4 8.5 4.1 7.7 7.7 7.1 11.7 7.6 8.8 7.3 7.8 7.6 8.0 8.0 7.8 8.3 8.9 8.2 7.7 7.2 6.9 6.8 7.0 9.5 6.5 11.8

0.24 0.15 0.85 0.54 0.11 0.60 0.06 0.95 0.68 0.78 0.32 0.58 0.18 0.60 0.51 0.69 0.76 0.29 0.78 0.41 0.31 0.55 0.76 0.12 0.08 0.20 0.14 0.15 0.23 0.24 0.32 0.26 0.23 0.24 0.17 0.22 0.16 0.22 0.49 0.48 0.01

R

R

R

R

63–2 lm fractions

*

5.4 1.4 4.4 5.8 8.5 7.9 1.1 6.1 19.8 8.2 2.3 1.1 1.9 4.3 5.4 4.3 4.1 6.2 4.2 5.8 8.9 7.2 11.8 3.2 6.8 7.3 7.1 6.9 7.1 6.8 6.3 7.7 6.1 6.4 5.8 7.7 5.9 5.2 2.7 6.2 5.4

Measured by ICP-MS.

<2 lm fractions 0.27 0.72 0.88 0.41 0.66 0.86 0.55 0.93 0.03 0.53 0.59 0.61 0.75 0.10 0.79 0.88 0.09 0.59 0.65 0.52 0.58 0.92 0.47 0.25 0.49 0.48 0.44 0.47 0.51 0.52 0.57 0.53 0.31 0.37 0.53 0.49 0.42 0.47 0.01 0.24 0.13

1.6 4.7 3.1 4.6 1.9 1.4 3.8 11.9 11.1 4.6 2.9 1.3 1.7 5.5 5.0 3.5 4.4 3.6 2.5 3.6 6.2 5.4 3.7 2.7 5.9 6.2 6.1 5.8 5.1 5.1 5.0 5.4 5.3 4.3 4.9 4.0 4.1 4.5 3.0 6.7 8.7

0.51 0.80 0.54 0.25 0.45 0.70 0.26 0.80 0.23 0.70 0.61 0.05 0.47 0.55 0.29 0.47 0.26 0.05 0.39 0.48 0.07 0.23 0.33 0.91 0.34 0.32 0.32 0.26 0.24 0.35 0.26 0.23 0.20 0.35 0.20 0.21 0.32 0.48 0.23 0.31 0.47

2.9 6.5 4.3 14.3 4.7 2.1 7.2 13.6 29.0 5.7 1.1 2.6 3.3 9.0 5.6 4.0 5.7 2.5 3.1 7.3 13.6 7.6 8.6 3.0 8.3 8.3 8.4 8.4 7.7 6.8 7.8 7.4 7.4 7.7 6.9 7.9 7.8 7.4 4.2 8.6 7.1

0.18 0.44 0.45 0.38 0.21 0.68 0.15 0.93 0.46 0.06 0.58 0.16 0.32 0.36 0.04 0.48 0.21 0.44 0.41 0.03 0.31 0.56 0.01 0.11 0.12 0.09 0.02 0.00 0.02 0.16 0.03 0.16 0.01 0.08 0.03 0.03 0.01 0.01 0.24 0.10 0.10

2.3 3.9 4.0 6.1 2.8 1.2 3.8 5.9 23.3 5.7 2.1 2.2 3.3 10.1 11.2 6.6 5.5 3.6 2.5 3.7 9.0 9.3 8.5 3.9 5.9 6.1 5.8 5.8 5.6 3.9 5.5 4.9 4.2 4.9 4.3 3.6 4.4 4.6 4.0 6.2 5.2

0.65 0.59 0.70 0.10 0.04 0.09 0.04 0.21 0.56 0.45 0.74 0.69 0.80 0.76 0.66 0.77 0.04 0.09 0.47 0.28 0.04 0.45 0.43 0.42 0.07 0.12 0.15 0.13 0.14 0.35 0.14 0.18 0.09 0.18 0.13 0.35 0.11 0.04 0.48 0.28 0.04

1.9 7.3 9.6 32.1 3.0 2.3 1.7 18.1 40.5 2.8 1.9 1.8 2.0 4.6 4.3 2.7 8.2 3.1 7.8 3.3 2.1 12.4 3.1 6.6 5.0 4.1 5.2 5.6 5.7 6.2 4.8 5.9 5.2 5.4 5.1 4.7 3.6 4.8 2.5 5.3 17.0

0.31 0.54 0.33 0.36 0.53 0.46 0.32 0.53 0.18 0.28 0.19 0.69 0.54 0.50 0.46 0.64 0.04 0.21 0.55 0.06 0.42 0.54 0.57 0.80 0.72 0.44 0.31 0.39 0.31 0.24 0.23 0.14 0.13 0.21 0.09 0.09 0.01 0.20 0.07 0.22 0.23

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Fe2O3 MnO MgO CaO Na2O K2O TiO2 P2O5 Stotal Li Be Sc V Cr Co Ni Cu Zn * Rb Y Zr * Mo * Cs Ba * La * Ce * Pr * Nd * Sm * Eu * Gd * Tb * Dy * Ho * Er * Tm * Yb * Lu * Pb * Th * U

R

111

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

associated with the separation of grain size fraction are not indicated by unusually enhanced Ni/Al2O3 variance. The Al-normalized concentrations of Mo und U show enhanced variability in the clay fractions. Mo and U are forming oxy-anions which behave mobile in oxic environments. Co-precipitation and scavenging of these oxy-anions in the course of solid/water interaction in the dust source areas is preferentially reflected in the clay fractions of the loess. The scattering of individual ME/Al2O3 averages around their S1-25 averages is generally low for the loess profiles from Shiyou He and Baiyong He (<5% for the silt fractions, Fig. 6a,b). The ME/ Al2O3 ratios of the Hei He profile distinctly differ from the ME/ Al2O3 averages of S1-25 for numerous trace elements (Li, Cs, Cr, Ni, Y, Zn, Zr, Th, U). In particular, REEs, Th, and U are relatively enriched in the silt fractions and depleted in the clay fractions. Since profile S27-40 is of coarser grain size composition, the weatheringresistant accessory minerals zircon, xenotime and monazite may be more abundant in the silt of this loess sequence, which may explain the enrichments of Y, Zr, REEs, Th and U. Only few ME/Al2O3 values show correlations with depth (Table 2). In the silt fractions of profile S1-8, the ME/Al2O3 ratios of V, Co, Ni and Mo show a

The Clayavs of PAAS-normalized REE concentrations fall slightly above one. The silt fractions of the S27-40 profile from the Hei He valley, which has an overall coarser grain size composition, shows significantly higher normalized REE contents than the silt of the other profiles (Fig. 5a,b). All silt and clay fractions show a relative enrichment of Sm, Eu and Gd and a weakly developed Ce/Ce* decrease compared to PAAS. Normalization of trace element contents using the conservative major element Al is applied to identify changes in the chemical composition of the siliciclastic loess fraction along the loess profiles independently from the variable dilution by quartz and carbonate. Such changes with depth may indicate variations in the provenance of the dust, e.g. changing contributions of pristine material from glacial grinding and lake sediments. In particular, trace element scavenging in the course of solid/water interaction at any time before the deflation of siliciclastic materials towards the study sites might be reflected in the ME/Al2O3 ratios. The great majority of trace elements show RSDs of their ME/Al2O3 ratios falling within the analytical uncertainty (5%) or only slightly exceeding 5% (Table 2). Ni contaminations from the used metal sieves

1.3

(a)

1.1

ME / Al2O3

0.9

silt fractions S 1-8, Shiyou He S 9-15, Shiyou He S 16-25, Baiyong He S 27-40, Hei He

0.7 1.3

(b) clay fractions

1.1

0.7

Li Be Sc V Cr Co Ni Cu Zn Rb Y Zr Mo Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pb Th U

0.9

Fig. 6. (a,b) Average chemical compositions of the silt and clay fractions of the loess sequences. Mean ME/Al2O3 ratios normalized versus corresponding averages of samples S1-25.

------------------------------------ S1-8(silt) ------------------------------------Shiyou He

S9-15(silt) Shiyou He

0

(a)

(c)

(b)

(d)

(e)

normalized depth

0.2

2

R = 0.57 R2= 0.86

0.4

0.6 R2= 0.62

0.8 R2= 0.78 R2= 0.83

1 0. 0 5

0 .1

Mo/Al2O 3

2

4

Ni/Al2O3

1

1 .5

Co/Al2O 3

7

8

9

V/Al2O3

40

50

Ba/Al2O 3

Fig. 7. (a–e) Depth trends of selected ME/Al2O3 mass ratios (ppm/wt-%) various normalized depths (depth/depthmax), analytical uncertainty marked by error bars.

112

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

slight increase with depth (Fig. 7a–d). ME/Al2O3 decrease is particularly obtained above 0.5 normalized depth. These trends do not occur in the clay fractions of profile S1-8, instead, Cs and Ba are slightly enriched versus Al in the upper profile section. In the silt fractions of profile S9-15, Ba/Al2O3 increases with depth (Fig. 7e). The clay fractions of profile S9-15 show positive correlative ME/ Al2O3 trends with depth for Sc, Ni, Y, all REEs and Th (Table 2). In the context of a mean analytical uncertainty of ±5%, however, all derived correlative trends for the loess profiles from Shiyou and

(b)

(a)

Baiyong He valley are statistically little significant. The clay fractions of the Hei He profile show distinctly higher variations with depth (Fig. 8a–r). 5.2. Oxygen and carbon isotope composition of the carbonates Corresponding silt- and clay-sized carbonate fractions differ in their oxygen isotope compositions (Fig. 9a,b). The clay-sized carbonates have a ca. 5‰ heavier oxygen isotope composition (1.9

(c)

(e)

(d)

(f)

0.2 0.4 0.6 0.8

4

8

Li/Al2O3

10

0.6

0.8

Rb/Al2O 3

1

0.

3

00 2 0. 00 4 0. 00 6

1

Cs/Al2O 3

0.2

0.24

K2O/Al2O3

0.008 0.012 P2O5/Al2O3

S total/Al2O3

(h)

(g)

(i)

(j)

(l)

(k)

0.2 0.4 0.6 0.8 1 0.03

0.04

1.2

TiO2/Al2O 3

1.4

1.6

5

Co/Al2O 3

(n)

(m)

6

7

Zr/Al2O3

(o)

2

2.5

La/Al2O 3

(p)

0.14 0.16

1.5

Yb/Al2O 3

Y/Al2O3

2

(r)

(q)

0.2 0.4 0.6 0.8

Pb/Al2O 3

0.5

Fe 2O3/Al2O 3

00

2.6 0.4

0.

1.8

6 0. 00 9 0. 01 2

1 0.9

1.1

Th/Al2O 3

0.4

0.7

CaO/Al2O3

5

10

CO3 (wt-%)

MnO/Al2O3 Fig. 8. (a–r) Typical pattern of ME/Al2O3 for the clay fractions of profile S27-40 (Hei He valley). Note the inverse correlations between CO3 and ME/Al2O3 ratios for trace elements with low water solubility (e.g. Zr/Al2O3, La/Al2O3).

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

5

5 0

δ18Ocarb (‰)

(a) 63 - 2 µm fractions

δ18Ocarb (‰)

-5

(c)

< 2 µm fractions

0

-5

-10 5

(b)

< 2 µm fractions

+ S1-8, Shiyou He S9-15, Shiyou He S16-26, Baiyong He S27-40, Hei He

-10

0

-10

-5 0 δ13Ccarb (‰)

-5

5

-10 0

0.2

0.4 0.6 0.8 normalized depth

1

Fig. 9. (a,b) Isotope compositions of carbonate-bound oxygen of the silt and clay fractions versus normalized depths, solid horizontal line: d18O(CaCO3) for assumed equilibrium isotope fractionation between H2O (d18O = 5.91‰, mean isotopic composition of local precipitation) and CaCO3 at 7.5 °C (local mean annual temperature), GNIP data base, Zhangye 1483 masl, data from Johnson and Ingram (2004), calculation of a after O’Neil et al. (1969), (c) positive correlative trends between d18Ocarb and d13Ccarb demonstrating genesis of clay-sized CaCO3 under an evaporative regime.

versus 6.8‰, averages for the entire data set). Clay-sized carbonate samples of the individual loess profiles define positive linear trend lines in the d18Ocarb–d13Ccarb diagram (Fig. 9c), which are not obtained for the silt-sized carbonates. In the lower part of the profiles S1-8, S16-26 and S27-40, clay-sized carbonates show a clear upward trend towards heavier oxygen isotope composition. Such a trend is not recorded in the d18Ocarb profiles of the silt fractions. Except for the loess sequence S9-15, the oxygen isotope compositions of clay-sized carbonates change towards lighter values in the upper profile sections. The oxygen isotope compositions of the silt-sized carbonates (Fig. 9a) roughly fit the d18Ocarb value that could be expected for pedogenic carbonate, assuming equilibrium isotope fractionation between CaCO3 and mean local precipitation (Fig. 9a). The silt- and clay-sized carbonates show similar variation ranges of d13C (5–1‰). Between 0.8 and 0.4 normalized depth, the d13Ccarb profiles of the silt fractions plot close together and show an upward increase in d13Ccarb. In contrast, the d13Ccarb depth

profiles of the clay-sized fractions distinctly differ among each other (Fig. 10a,b). The d13Ccarb values of the clay fractions, however, also show clear upward trends to heavier isotope compositions in the middle sections of the profiles. 5.3. Sequential leaching Loess profile S9-15 from Shiyou valley and samples S16-26 from Baiyong He valley were selected for Sr isotope analyses. Strontium isotope compositions were determined for NH4Cl exchangeable (weakly surface-bound) Sr, HAc leachable (carbonate-bound) Sr, and residual (silicate-bound) Sr. As the separation of grain size fractions included wet processing, leaching with 1 M NH4Cl was performed at the bulk freeze-dried samples. The >63 lm fractions of the samples S9-26 typically account for 10% of the bulk samples (Table 1). The specific surface of particles decreases with increasing particle size. Therefore, the determined amounts of NH4Cl leachable cations slightly underestimate the real amounts of NH4Cl

0

normalized depth

(b)

(a)

0.2

< 2 µm fractions

0.4

63 - 2 µm fractions + S1-8, Shiyou He

0.6

S9-15, Shiyou He

0.8

S1-8 S9-15 S16-26 S27-40

clay - 0.87 - 0.68 - 0.79 - 0.65

silt - 0.86 - 0.64 - 0.18 no data

S16-26, Baiyong He S27-40, Hei He

1 -10

-5 0 δ13carb (‰)

5 -10

-5 0 δ13Ccarb (‰)

5

Fig. 10. (a,b) Isotope compositions of carbonate-bound carbon of the clay and silt fractions versus normalized depths. The inset Table gives Pearson correlation coefficients for the correlations of d13Ccarb with depth, grey line in (b) d13C of CaCO3 calculated for equilibrium isotope fractionation between soil-CO2 without contributions from 6  6:13 ¼ 12:1 for a mean local temperature of 7.5 °C (see Table 5-1 in atmospheric CO2 (d13C  8‰), d13CC4-plants = d13Csoil-CO2 = 15‰, d13 Ccarb ¼ d13 CCO2 ðgasÞ þ e; e ¼ 1:43510 T 2 ðKÞ Turi, 1986).

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Table 3 NH4Cl exchangeable cations. Ca (leq/g)

Na (leq/g)

Mg (leq/g)

K (leq/g)

Sr (leq/g)

Total

He 427 435 434 462 397 530 703

8.9 65.6 90.0 90.6 81.6 79.5 83.4

38.0 47.1 55.4 53.7 54.1 59.0 49.1

2.54 1.83 1.85 1.71 1.63 1.21 2.35

0.769 0.798 0.907 1.01 0.878 1.17 1.37

477 550 582 609 535 671 839

Baiyong He S16 508 S17 582 S18 762 S19 538 S20 536 S21 573 S22 569 S23 532 S24 538 S25 499 S26 489

22.1 56.6 74.3 100 98.2 112 117 111 96.4 87.8 79.1

42.7 76.2 80.4 93.0 95.2 120 111 95.3 80.8 70.3 59.0

1.24 0.88 1.35 2.20 2.61 3.42 3.28 3.32 3.23 2.95 2.59

0.673 0.874 1.23 1.20 1.22 1.68 1.67 1.69 1.51 1.39 1.37

574 717 920 734 734 809 801 744 720 661 631

Shiyou S9 S10 S11 S12 S13 S14 S15

leachable cations in the fine grain size fractions and NH4Cl leachable Sr of the clay fractions may be slightly underestimated relative to that of the silt fractions. In the profiles S9-15 and S16-26, the total of NH4Cl exchangeable Ca, Na, Mg, K and Sr varies between 477 and 920 leq/g with an average of 684 leq/g (Table 3). The dominant cation in all NH4Cl leachates is Ca. Strontium contributes between 0.67 to 1.7 leq/g to the total cation-exchange capacity of the samples (mean: 1.2 leq/ g). NH4Cl exchangeable Ca and Sr reach substantial percentages of the total Ca and Sr contents (maximum Ca: 23%, maximum Sr: 35%, Table 4). The NH4Cl leachable portions of Sr exceed consistently those of Ca. Consequently, the NH4Cl leachates are characterised by lower Ca/Sr ratios than the bulk compositions of the silt and clay fractions (Table 4). The HAc leachates (Appendix Table A.5) largely comprise carbonate-bound elements with Ca as major and Mg, Sr, Fe, Mn and Ba as minor constituents. Mineral phases in the residues after

HAc leaching were illite, quartz, chlorite, orthoclase and Na-rich plagioclase. No siderite or dolomite could be detected in the residues. Normative CaCO3 values derived from directly analysed Ca and CO3 contents closely correspond, which implies a low-Mg composition of the loess carbonates (see Fig. A.1, Appendix for Ca budgets). Magnesium in the HAc leachates dominantly originates from the dissolution of chlorite. The cumulated contents of NH4Cl and HAc leachable Ca slightly fall below the total Ca concentrations. The Ca/Sr ratios of the HAc leachates (carbonates) distinctly exceed those of the NH4Cl leachates (Table 4). Silt-sized carbonates show consistently higher Ca/Sr ratios than carbonates from the clay fractions (ca. 1.3 times). The Ca/Mg ratios show the opposite variation. On average, Ca/Mg ratios in the HAc leachates of the clay fractions exceed those of the silt fractions ca. 1.5 times (Appendix Table A.5). Minor amounts of Al were leached from non-calcareous phases (mean silt (S9-26): 0.048% Al2O3, mean clay (S9-26): 0.14% Al2O3). Particularly, the chemical composition of HAc leachates of the <2 lm grain size fraction appears influenced by element release from silicates and/or non-calcareous amorphous materials (Appendix Table A.5). Variations of geochemical signatures in the HAc leachates versus bulk composition of the <2 lm and silt-sized fractions comprises hydrogenetic geochemical signatures associated with element release during chemical weathering and element immobilization in carbonates and/or in relatively weekly bound form, e.g. scavenging of UO2 4 and REEs by Fe-oxidhydroxids (cf. increase in U/Th and enhanced Eu/Eu** and negative Ce/Ce* anomalies of HAc leachates versus corresponding bulk compositions, Table 5). The REE contents of the HAc leachates reach substantial portions of their bulk contents with higher portions for the MREEs (Fig. 5e). 5.4. Strontium isotope composition The NH4Cl leachates of the bulk loess samples and HAc leachates of the clay and silt fractions have very similar Sr isotope compositions (Table 6, mean NH4Cl leachates: 0.7114, mean HAc leachates (silt, clay): 0.7111). The residuals of the silt fractions

Table 4 Ca, Sr mass budget and Ca/Sr ratios of various loess fractions. Sample

Ca (%)

Sr (%)

Ca (%)

NH4Cl

HAc

Bulk

63–2 lm

Sr (%)

Ca (%)

Sr (%)

<2 lm

Ca/Sr (atom ratios) NH4Cl

HAc

Bulk

Bulk

63–2 lm

<2 lm

63–2 lm

<2 lm

Shiyou He S9 S10 S11 S12 S13 S14 S15 m

12 12 13 13 11 15 19 14

16 16 18 20 17 23 25 19

73 76 64 64 69 85 72 72

36 33 27 27 32 45 38 34

88 92 87 89 90 87 86 88

47 56 56 51 55 65 60 56

555 545 479 460 452 453 513 494

1523 1686 1709 1678 1531 1370 1365 1552

1277 1375 1020 1255 1228 1211 1031 1199

747 728 709 715 704 729 722 722

699 868 687 744 791 931 778 785

Baiyong He S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26 m

17 17 22 19 17 23 20 19 16 14 11 15

16 18 26 26 27 35 33 31 29 26 20 26

60 67 60 51 59 61 58 59 69 78 77 64

24 34 27 15 24 18 19 17 23 33 38 25

76 88 89 83 83 82 87 88 81 76 89 84

36 63 60 51 51 52 50 54 54 58 70 55

755 666 621 450 441 340 340 314 357 358 357 454

1657 1502 1759 2254 1790 2112 1955 2080 1912 1623 1223 1806

1783 1433 1433 1602 1464 1284 1369 1195 1152 1216 847 1343

680 751 777 679 743 621 648 599 636 681 595 674

854 1036 972 986 900 818 796 740 770 933 670 862

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Bulk

0 Baiyong He S16-25

HAc leachates

Bulk

m

s

m

s

m

s

m

s

63–2 lm LaN/YbN Ce/Ce* Eu/Eu** U/Th

1.26 0.972 1.18 0.241

0.041 0.005 0.018 0.009

1.13 0.800 1.24 1.07

0.061 0.019 0.029 0.697

1.26 0.971 1.19 0.234

0.025 0.006 0.023 0.006

1.16 0.811 1.30 0.96

0.060 0.024 0.043 0.303

<2 lm LaN/YbN Ce/Ce* Eu/Eu** U/Th

1.06 0.964 1.17 0.279

0.023 0.017 0.020 0.025

1.23 0.746 1.29 1.77

0.065 0.026 0.040 0.394

1.06 1.046 1.04 0.239

0.028 0.036 0.049 0.021

1.32 0.759 1.29 1.65

0.091 0.027 0.040 0.413

1

Ac

Shiyou He S9-15

Sr H

Table 5 Compilation of REE signatures and U/Th ratios.

HAc leachates

0.2

0.8

0.4

0.6

$ 63 - 2 µm 0.4 fractions + < 2 µm fractions

0.6

0.8

1

0

Sr

r es

idu al

REE ratios calculated for PAAS-normalized REE concentration data. m = mean, s = standard deviation.

0.2

0

Table 6 Sr isotope compositions.

0.2

0.4

0.6

0.8

1 SrNH 4Cl

87

Sr/86Sr

Sample

NH4Cl-exchangeable

HAc leachable

Silicate-residue

Shiyou He S9 S10 S11 S12 S13 S14 S15

63–2 lm fractions 0.711547 ±7 0.711447 ±7 0.711785 ±7 0.711469 ±11 0.711488 ±8 0.711463 ±7 0.711469 ±13

0.710999 0.711006 0.710880 0.711063 0.711195 0.711284 0.711216

±7 ±11 ±7 ±7 ±9 ±7 ±7

0.719865 0.719486 0.719585 0.719867 0.719405 0.719809 0.720104

±7 ±7 ±7 ±7 ±9 ±11 ±7

Baiyong He S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26

0.711427 0.711410 0.711301 0.711277 0.711245 0.711180 0.711172 0.711199 0.711151 0.711161 0.711126

±8 ±7 ±11 ±7 ±7 ±7 ±8 ±7 ±7 ±7 ±7

0.710895 0.710807 0.710743 0.710986 0.711132 0.711158 0.711025 0.711201 0.711091 0.710997 0.710779

±7 ±8 ±7 ±7 ±14 ±7 ±7 ±7 ±9 ±8 ±7

0.719329 0.718771 0.719276 0.719664 0.720423 0.720287 0.720509 0.720015 0.719715 0.719377 0.717897

±15 ±7 ±9 ±9 ±10 ±7 ±8 ±7 ±7 ±6 ±8

Baiyong He S9 S10 S11 S12 S13 S14 S15

<2 lm fractions 0.711547 ±7 0.711447 ±7 0.711785 ±7 0.711469 ±11 0.711488 ±8 0.711463 ±7 0.711469 ±13

0.711327 0.711310 0.711322 0.711454 0.711415 0.711366 0.711421

±7 ±11 ±7 ±7 ±7 ±7 ±9

0.725513 0.725229 0.724282 0.724276 0.725592 0.724599 0.724825

±7 ±8 ±7 ±8 ±7 ±12 ±7

Baiyong He S16 S17 S18 S19 S20 S21 S22 S23 S24 S25 S26

0.711427 0.711410 0.711301 0.711277 0.711245 0.711180 0.711172 0.711199 0.711151 0.711161 0.711126

0.711127 0.711197 0.711147 0.711187 0.711157 0.711130 0.711152 0.711139 0.711158 0.711183 0.711049

±7 ±7 ±7 ±6 ±7 ±7 ±7 ±7 ±8 ±7 ±7

0.725183 0.723441 0.725729 0.724999 0.724950 0.724709 0.724574 0.723737 0.724844 0.723251 0.724178

±14 ±7 ±8 ±9 ±7 ±9 ±8 ±7 ±7 ±8 ±7

±8 ±7 ±11 ±7 ±7 ±7 ±8 ±7 ±7 ±7 ±7

Errors are reported as 2rm and refer to the last digits.

show a mean 87Sr/86Sr value of 0.7196 and the residuals of the clay fractions are characterised by a mean 87Sr/86Sr ratio of 0.7247. Loess profile S9-15 from Shiyou He and loess samples S16-26 from Baiyong He valley show nearly identical Sr isotope characteristics. Fig. 11 shows the relative contributions of each component to the

Fig. 11. Strontium budget of loess samples S9-26, silicate-bound Sr (Srresidual) calculated as difference of total Sr and cumulative Sr contents of NH4Cl leachable (SrNH4 Cl ) and HAc leachable Sr (SrHAc).

clay and silt fractions, as derived by mass balance. The bulk clay and silt fractions of samples S9-26 define separate data clusters in the Rb–87Sr/86Sr and 1/Sr–87Sr/86Sr diagrams. The bulk clay fractions show positive correlative trends (Fig. 12a,b). The positive correlations between 87Sr/86Sr and Rb are not obtained for the HAc leachates and 87Sr/86Sr values of the silicate residuals do not show any correlation with 1/Sr (Fig. 12c,d). The trend in the Rb–87Sr/86Sr and 1/Sr–87Sr/86Sr diagrams for the bulk clay may reflect the variable contributions of low-Rb (e.g. calcite, apatite) and old high Rb (sheet silicates) phases. Strontium with the most radiogenic compositions (87Sr/86Sr: 0.716, 0.718) is obtained in the two clay-sized samples with the highest Rb contents (S9 and S16: Rb = 149, 150 ppm, Rbav S9-25 = 133 ppm), which reflects that the Rb–87Sr/86Sr relation of at least these two samples is affected by an old high Rb phase. Apart from samples S9 and S16, the variation ranges of 87Sr/86Sr in the bulk clay and silt fractions are similar (0.714–0.716, Fig. 12a), although the Rb contents of the clay fractions distinctly exceed those of the silt-sized loess component. The similar variation ranges for the bulk silt and clay fractions, that host by 0.005 87Sr/86Sr units more radiogenic silicate-bound Sr than the silt, are obtained, since the clay has higher calcite contents (unradiogenic Sr) than the silt. 6. Discussion 6.1. Average geochemical signatures of the non-calcareous loess fractions About 10% of the present land surface is covered with Pleistocene loess (Pecsi, 1968). A predominant portion of its particle inventory originates from glacial grinding. Such materials have been little affected by chemical alteration between abrasion and fluvial deposition in the arid basins. A number of studies showed that Pleistocene loess shows a similar composition as Post-Archean shales, particularly, for conservative trace elements as the REEs (e.g. Taylor et al., 1983; Gallet et al., 1998). The continental crust forms about 0.35 wt-% of the earth. About 60% of the crust is assumed to have been in place 2.6 billion years ago (Taylor and McLennan, 1995). The composition of the present upper continental crust, which is characterised by a strong enrich-

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

0.720

0.720

(a)

bulk samples Sr/86Sr

0.716 0.714

0.716 0.714 0.712

0.710

0.710 60

80

100

120

140 63160 - 2 µm,

0.714

0 < 2 µm

0.0025

0.005

0.0075

0.01

0.730

(d)

(c) 0.713

0.725 Sr/86Sr

HAc leachates

HAc residuals 0.720

87

0.712

87

Sr/86Sr

bulk samples

R²= 0.65

R²= 0.57

0.712

(b)

0.718

87

87

Sr/86Sr

0.718

0.711

0.715

0.71

0.710 1

2

3

4

5

0

0.005

0.01

0.015

0.02

0.025

1/Sr (µg/g)-1

Rb (µg/g)

Fig. 12. (a,b) Diagrams demonstrating separate positive correlations between total Rb(1/Sr) and 87Sr/86Sr for clay and silt fractions of samples S9-26. Calculation of bulk Sr isotope composition based on analytically determined silt/clay ratios, Sr speciation, and Sr isotope compositions of NH4Cl, HAc leachable and silicate-bound Sr. (c,d) the positive correlations are not valid for Sr of the HAc lechates and silicate-bound (residual) Sr.

ment of Large ionic litophile elements and the heat producing elements K, U and Th, is the result of repeated cannibalistic recycling of sedimentary rocks (Veizer and Jansen, 1985). There is a broad consensus that mixing and homogenization by sedimentary processes on global scale produce relatively uniform concentration values in fine-grained clastic sedimentary rocks for trace elements with a low water solubility and, therefore, average concentrations of these elements (e.g. Th, REEs) in shales and loess provide robust estimates of the upper continental crust composition (Taylor and McLennan, 1985). The average concentrations of SiO2, TiO2, K2O, FeO, P2O5 in the silt and clay fractions of the Holocene loess profiles S1-8, S9-15, and S16-25 recalculated on CO2 and H2O-free basis and normalized using UCC data of Rudnick and Gao (2004) fall into a variation range of 1 ± 0.25 (Fig. 4a,b). Consistently low normalized Al2O3,

2

S 1-8, Shiyou He S 9-15, Shiyou He S 16-25, Baiyong He S 27-40, Hei He mean (S1-25)

1

0

Na2O SiO2 TiO2 Nd Pr La Ce Sm Eu Zr Ba Gd Tb Cr Dy Ho Lu Yb Tm Er Y Th Al2O3 MgO FeO V K2O Be Sc U Ni Rb MnO P2O5 Co Zn Li Pb Cu Cs Mo

MEclay / MEsilt

3

K2O, P2O5 values close to 0.75 in the silt fractions reflect dilution by quartz. The dilution of Mg is counterbalanced by Mg-rich chlorite and carbonate-bound Mg. The Na2O contents of clay fractions (S1-40: 0.84) show a distinct deficit (Fig. 3a). Such a Na2O deficit also occurs in the silt fractions and in loess samples from the Central Loess Plateau (Fig. 4a) and reflects leaching of Na in the course of chemical silicate weathering (Nesbitt et al., 1996). Because of the dry local conditions, the depletion of Na is most likely an original signature of the dust. In the clay fractions of the Qilian Shan loess, Co, Sc, Be, V, Ni, REEs are enriched against UCC by a factor of about 1.25. Fig. 13 shows the enrichment of major and trace elements in the clay fractions relative to the corresponding silt fractions for the Qilian Shan loess. Fine fractions rich in clay minerals and thus characterised by large specific particle surfaces have a high scavenging capacity for

Fig. 13. Enrichment/depletion of major and trace elements in the <2 lm fractions compared to their mean concentrations in the corresponding silt fractions. Analytical data on CO2 and H2O-free basis considered for calculations, grey horizontal lines mark MEclay/MEsilt ratios of 1.3 and 1.7.

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

dissolved trace elements. A general enrichment of trace elements is therefore typically for the clay-sized particle fractions of sediments (cf. clay fractions, loess Changchun, Fig. 4c). Zn, Cu, Pb, U, Mo, and the alkali elements Li, Rb, and Cs show distinct enrichment factors above 1.5 in the clay fractions of the four investigated loess profiles compared to UCC and average global loess composition (McLennan, 2001). Enhanced UCC-normalized concentrations for Cu, Li and Cs, however, were also obtained for the Siltavs of the Qilian Shan loess (Fig. 4a). Sun et al. (2007) report unusually high Ni, Li, and Cs contents compared to UCC composition for loess samples from the southern Tibetan Plateau. The Clayavs of the non-calcareous loess from Changchun represent a strongly leached material (Na2Osample/Na2OUCC = 0.14). The majority of UCC-normalized element averages of the clay fractions S1-25 (cf. Fig. 4b) are highly correlated (R2 = 0.9) with the UCC-normalized Clayavs of the Changchun loess (e.g. REEs, Y, Sc, U, Th, Li, Rb, Cs, Li, Fig. 4d). The ME/UCC data furthermore reflect strong leaching of mobile components like Na2O, K2O, P2O5, MnO, MgO and of the trace elements Zn, Pb, Mo, Cu for the clay fractions of the Changchun loess and/or a relative enrichment of these elements in the fine fractions of the Qilian Shan loess (Fig. 4d). 6.1.1. The rare earth element record The Clayavs and Siltavs of the loess sequences S1-8, S9-15, S1626, and S27-40 show similar PAAS-normalized REE distribution pattern with an enrichment of MREEs and significant negative Ce/Ce* anomalies for all Siltavs (Fig. 6a–d). A similar enrichment of Sm, Eu, and Gd relative to PAAS composition is also present in loess and paleosols from the Central Loess Plateau (Ding et al., 2001; Xifeng loess: Jahn et al., 2001). The relative depletion of HREEs in the silt fractions of the Qilian Shan loess may reflect incomplete dissolution of zircon crystals, which favour incorporation of HREEs. This analytical uncertainty, however, does not affect the quantification of the weak negative Ce/Ce* anomaly and distorts the Eu/Eu** parameter only little. Leaching experiments document that the negative Ce anomaly and the enrichment of MREEs represent hydrogenetic signatures of the loess (Table 5) which is also known from loess from the Luochan section (CLP, Chen et al., 1996). Leaching with HAc detects scavenged and co-precipitated REEs from weathering solutions. Under oxic weathering conditions, Ce is less mobile than the other REEs as it can occur in a valency of IV. Substantial chemical weathering of siliciclastics hosting REEs at the study sites should be detectable by positive Ce/Ce* ratios if dissolved REEs are removed, whereas chemical weathering without leaching should not change the initial Ce/Ce* value of the aeolian deposits. The source regions of the dust may have been sinks for REEs dissolved in natural waters or received siliciclastic input that already carried this signature. This detrital input may have acquired Ce/Ce* values <1 during fluvial transport or an older sedimentation cycle. Europium is the only REE occurring in a divalent state and is preferentially incorporated in plagioclase for structural reasons. Chemical weathering of siliciclastics containing plagioclase as a major mineral component therefore will release REEs with a positive Eu/Eu** anomaly. Aquatic re-distribution and scavenging of these REEs eventually produces HAc leachable material with enhanced Eu/Eu** values. Since arid conditions do not favour chemical weathering at the sampling sites, the above hydrogenetic signatures, therefore, may largely represent an initial characteristic of the dust. The bell-shaped enrichment of MREEs in the loess versus PAAS (Fig. 5a,b) is not fully understood. We obtained the similar pattern in sediments from numerous European lakes. Apatite favours the incorporation of Sm, Eu and Gd (e.g. Pan and Fleet, 2002). It is easily weatherable and is a relevant carrier of REEs. The relative

117

enhancement of Eu/Eu** in the HAc leachates may reflect REE release by dissolution of apatite during the HAc treatment and contributions from weakly bound REEs originating from the chemical weathering of apatite. The North Pacific Ocean is a major sink of Asian dust (e.g. Rea and Leinen, 1988). The release of substantial amounts of leachable REEs from dust settling into the deep ocean water changes the chemical composition of the remaining residues and affects the dissolved REE seawater composition. The preferential leaching of MREEs in dust of NW Chinese provenance (Fig. 5e, Table 5) explains the excess of MREE in loess of NW Chinese provenance relative to aeolian dust records in marine sediment of the North Pacific (Weber II et al., 1998 and references therein). 6.1.2. Comparison of the loess profiles Presumed similar loess accumulation periods for each loess profile, the dust accumulation rate of the total Hei He profile (140 cm) has to be higher than those of the other sites. The overall lower carbonate contents of the Hei He profile (Fig. 14a,b) should be related to a higher influx of siliciclastics, presumably reflects different dust sources. The MEclay/MEsilt curve for the average loess from the Hei He valley significantly differs from those of the Shiyou He and Baiyong He valley (Fig. 13). The latter implies that dust of a different provenance contributed to the aeolian deposition in the Hei He valley. The clay fractions of the loess sequence from Hei He valley show much higher MEclay/MEsilt ratios for Al, Mg, Fe, K and much higher enrichments of V, Be, Sc, Ni, Co, Zn, Cu, Li, Rb, and Cs compared to the loess profiles from Shiyou He and Baiyong He (Fig. 7). The MEclay/MEsilt pattern of the Hei He loess may reflect a different clay mineral assemblage and/or a stronger trace element scavenging by clay-sized particles in the source area of the Hei He loess. The difference to the other sites largely results from higher trace element contents of the Clayav (cf. Fig. 4b), which implies a higher extent of trace element scavenging by solid/water interaction. The latter indicates substantial solid/water interaction for the source materials of the loess, as it might be the case for river bed sediments, sediments of temporal lakes and bedrocks affected by hydrothermal alteration (see Wünnemann et al., 1998 for the extent of large palaeolakes located to the north of the study sites and fed by river discharge from the Qilian Shan). Normalization of trace element concentrations using the conservative major element Al indicates trace element leaching or scavenging. In particular, the clay fractions with their large specific particle surface record such hydrogenetic signatures sensitively. The ME/Al2O3 of Siltav and Clayav of the loess profiles from Shiyou He and Baiyong He valley are similar. Average ME/Al2O3 ratios of the loess sequence S27-40 clearly discriminate the Hei He loess against the other profiles (Fig. 6a,b). The Siltav of the Hei He loess is characterised by distinctly higher ME/Al2O3 ratios for Cr, Ni, Y, Zr, Th, U and lower Li/Al2O3, Rb/ Al2O3, and Cs/Al2O3 ratios than the silt from the other sites. The Cr/Al2O3 and Ni/Al2O3 values of the average clay fraction of the samples S27-40 exceed these ratios from the Shiyou He and Baiyong He valley. Aluminium normalized concentration data of Li, Mo, Cs, U, Zr, Y, and the REEs fall distinctly below the corresponding ME/Al2O3 averages of the loess samples S1-25. The provenance of the silt-sized siliciclastics from the Hei He loess is different from that of the Shiyou and Baiyong He valley. 6.1.3. Depth trends and inter-element correlations – palaeoenvironmental interpretations Geochemical signatures of the loess fractions are characterised by their ME/Al2O3 ratios (see Section 5.1.). Only a restricted number of elements show ME/Al2O3 variations high enough to reliably identify depth trends and inter-element correlations (RSD > 5% and

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Fig. 14. (a,b) Loess sections S1-8, S9-15, S16-26, S27-40, depth profiles of the CO3 contents for the silt and clay fractions. (c,d) Clay and silt fractions of samples S9-26, correlations between carbonate contents and Ca/Sr ratios of HAc leachates.

R > 0.5, Table 2). In the clay fractions of all loess profiles, the relative standard deviations of ME/Al2O3 exceed 5% for Mn, Mg, Ca, P, Stotal, U, Mo and Cu. The enhanced ME/Al2O3 variability of these elements is related to their relatively high mobility in natural oxic environments and/or reflects variable CaCO3 contents of the loess (Ca, Mg). In the clay fractions of the Hei He profile, more elements show ME/Al2O3 ratios with RSDs > 5% (Table 2, Fig. 8a–r). The ME/ Al2O3 depth profiles of these fractions show characteristic pattern. Depth pattern 1 is obtained for the elements Li, Rb, Cs, and Stotal (Fig. 8a,d). It shows a general upward increase with a superim-

posed minimum in the middle section. There are relative maxima around 0.2 and between 0.8 and 0.7 normalized depth. Potassium has a similar pattern, though at a low scattering along the profile (RSD = 2.4%). The depth profile of P2O5/Al2O3 shows an overall increase upward without any superimposed maxima (Fig. 8e,f). Profile pattern 2 is prominently represented by Zr/Al2O3 and by the Al2O3 ratios of REEs, Y, Pb, Th, Mn, Ti, and possibly Fe (Fig. 8, Table 7). Pattern 2 is characterised by enhanced values in the middle section, relative minima around 0.7 and between 0.4 and 0.3 without a significant upward trend. Minima and maxima are inver-

Table 7 Depth profile pattern of S27-40 defined by selected ME/Al2O3 ratios, correlation with other ME/Al2O3 ratios quantified by Pearson correlation coefficients (R). Cs/Al2O3

Zr/Al2O3 R

63 – 2 lm fractions * Cs 1.00 Li 0.98 * Rb 0.86 0.73 Stotal MgO 0.70 Zn 0.68 Cu 0.49 CaO 0.49 * Pb 0.29 Ba 0.18 * U 0.18 0.18 K2O MnO 0.13 0.07 P2O5 * Eu 0.11 Co 0.18 Be 0.21 Sr 0.26 0.26 Fe2O3 * La 0.27 * Mo 0.29 Ni 0.29 * Yb 0.31 * Th 0.35 Zr 0.38 V 0.46 Y 0.49 Cr 0.53 0.55 Na2O 0.57 TiO2 Sc 0.61

Ca/Al2O3 R

Zr * Yb * La Y TiO2 * Eu * Th * U Cr Na2O Fe2O3 Sc * Pb V P2O5 Cu * Mo MgO MnO Stotal Be Ni Ba Co Zn * Rb K2O Li * Cs CaO Sr

1.00 0.94 0.90 0.86 0.83 0.81 0.75 0.65 0.47 0.42 0.39 0.37 0.35 0.26 0.25 0.09 0.01 0.10 0.12 0.15 0.17 0.22 0.24 0.26 0.35 0.35 0.37 0.38 0.38 0.41 0.46

Fe/Al2O3 R

CaO Li Zn MnO * Cs K2O * Rb Stotal Co MgO P2O5 Cu Ni * Mo Be Ba Sr * Pb V * Th Na2O * U Cr Fe2O3 Sc Y * La * Eu * Yb TiO2 Zr

1.00 0.53 0.49 0.49 0.49 0.46 0.46 0.43 0.38 0.36 0.35 0.26 0.22 0.17 0.13 0.09 0.02 0.01 0.01 0.02 0.08 0.09 0.10 0.10 0.12 0.16 0.18 0.22 0.27 0.38 0.41

Cs/Al2O3 R

Fe2O3 V Sc Cr Ni MnO Ba Y Co * U Cu TiO2 * Th Be Zr * Yb * La * Eu * Mo Sr Zn Na2O P2O5 * Pb CaO * Cs Stotal Li K2O MgO * Rb

1.00 0.92 0.84 0.84 0.69 0.69 0.64 0.63 0.61 0.60 0.52 0.50 0.46 0.42 0.39 0.38 0.35 0.25 0.16 0.16 0.13 0.04 0.03 0.09 0.10 0.26 0.28 0.33 0.34 0.41 0.45

Zr/Al2O3 R

<2 lm fractions * Cs 1.00 Li 0.95 * Rb 0.89 P2O5 0.69 MgO 0.67 Stotal 0.64 K2O 0.64 CaO 0.49 Zn 0.26 * U 0.25 V 0.10 Sr 0.11 Be 0.17 Na2O 0.18 * Yb 0.20 Fe2O3 0.25 TiO2 0.26 * La 0.26 Zr 0.28 * Eu 0.38 Sc 0.42 Ba 0.43 MnO 0.43 Y 0.50 * Pb 0.54 Co 0.58 * Th 0.61 Cu 0.62 * Mo 0.70 Ni 0.76 Cr 0.79

Ca/Al2O3 R

Zr * Yb Y * Pb * Eu * Th Fe2O3 * La MnO TiO2 Sc Co V Cr * Mo Na2O Ni Ba * U Zn Cu * Rb P2O5 Li * Cs Be Sr MgO Stotal K2O CaO

1.00 0.91 0.89 0.88 0.86 0.85 0.82 0.82 0.78 0.68 0.63 0.63 0.53 0.48 0.42 0.40 0.40 0.38 0.26 0.10 0.11 0.11 0.14 0.26 0.28 0.34 0.54 0.62 0.76 0.81 0.83

Fe/Al2O3 R

CaO CO3 (conc.) Stotal K2O MgO Sr Li * Cs P2O5 * Rb Be Zn Cu * U Na2O Ba V * Mo TiO2 Ni * La Co MnO Fe2O3 Sc Cr * Eu * Yb * Th Y * Pb

1.00 0.99 0.95 0.72 0.69 0.54 0.49 0.49 0.44 0.37 0.25 0.01 0.05 0.26 0.28 0.37 0.38 0.41 0.44 0.48 0.55 0.57 0.59 0.60 0.62 0.63 0.65 0.70 0.71 0.75 0.79

R Fe2O3 * Yb * Eu * Th * La MnO V Y * Pb Zr Co TiO2 Sc Ni Cr * U Na2O Zn Ba * Mo Cu * Rb P2O5 Li * Cs Be MgO Sr Stotal CaO CO3 (conc.)

1.00 0.90 0.89 0.88 0.87 0.86 0.86 0.83 0.82 0.82 0.80 0.75 0.59 0.58 0.47 0.39 0.38 0.36 0.36 0.35 0.10 0.02 0.07 0.16 0.25 0.38 0.41 0.50 0.52 0.60 0.65

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

sely correlated to the ME/Al2O3 profiles of pattern 1. Except for Mn, Fe and Pb, the above elements show immobile behaviour in natural environments. The Fe2O3/Al2O3 ratios may reflect changes in the contributions by Fe-oxidhydroxids. ME/Al2O3 correlations with Fe/Al2O3 significantly improve the positive correlations with Mn, Co, V, Ni, Zn, and U (Table 7). These elements are relatively mobile in natural environments and get scavenged by Fe-precipitates. Similar to the ME/Al2O3 pattern 1, carbonate contents in the clay fractions of profile S27-40 also show a maximum around 0.7 normalized depth and a decrease in the middle section. As CO3, Stotal/Al2O3 and Ca/Al2O3 show pronounced double peaks between 0.5 and 0.2 normalized depth (Fig. 8d,q,r). The increase of ME/Al2O3 for Li, Rb, Cs as well as of Ca/Al2O3 and Stotal/Al2O3 above 0.5 normalized depth, which coincides with an increase in the carbonate contents, indicates influx of mineral particles originating from lacustrine sediments of dried out lake basins. These particles comprise chemical precipitates (gypsum (Ca, Stotal), carbonates (Ca, Mg, Sr)) and clay minerals enriched in Rb, Cs and Li. Thus, the variation with depth may document regional climate change during the Holocene towards drier conditions after the mid Holocene, when, loess with lower contents of silt and sand were accumulated (cf. 4.1). The Ce/Ce* profile supports that another clay-sized dust fraction became important for aeolian deposition at the Hei He site (Fig. 5c,d). The decrease of Ca/Al2O3 and Stotal/Al2O3 above 0.3 normalized depth reflects an increase of siliciclastic input at the study site and/or decreased aeolian deposition of CaCO3 and gypsum. The latter indicates long-term exhaustion of chemical sediments in the source areas of the Hei He loess due to continued deflation or a general decline of chemical precipitation in seasonal lakes due to decreased inflow. Analogously, the carbonate and Me/Al2O3 maxima of group 1 elements in the lower profile section of the Hei He loess (0.7 cm) may reflect a dry episode in Northwest China during the early Holocene (cf. Chen et al., 2008). The opposite trend of ME/Al2O3 between pattern 1 and pattern 2 elements in the clay fractions of the Hei He profile largely documents variable contributions from two sources of different hydrological settings, i.e., (i) sediments deposited under evaporative conditions in arid basins including the foreland of Qilian Shan and (ii) river-suspended siliciclastics from the discharge of high mountain areas. The availability of pristine mineral debris for aeolian uptake was high shortly after the Late Glacial Holocene transition, when the melting of glaciers resulted in high fluvial transport of siliciclastics towards the source regions of the dust. The ME/ Al2O3 reincrease of pattern 2 elements (Zr, REEs, Th, etc.) above 0.7 normalized depth reflects wetter climate conditions during the mid Holocene (Chen et al., 2008) that favoured the fluvial transport of siliciclastics from high mountain areas to the arid basins. 6.2. The carbonate fractions 6.2.1. Chemical and stable isotope composition implications for carbonate genesis Carbonate represents a major component in all loess samples. It is present as low-Mg calcite and accounts for 15.4–32.7 wt-% CaCO3 in the clay fractions and ranges between 11.4 and 21.5 wt% CaCO3 in the silt fractions. The carbonate contents of the Qilian Shan loess fall in the variation range of CaCO3 in the Luochuan loess section (3.6 – 20.9%, Liu, 1985). Calcite of the silt fractions, as inferred from the compositions of the HAc leachates, shows consistently higher Ca/Sr ratios and lower Ca/Mg ratios than calcite of the clay fractions (Table 4; Appendix Table A.5: Ca/Mg Siltav: 7.5, Clayav: 8.9). The Ca/Sr ratios of the HAc leachates closely document the calcite compositions, whereas Ca/Mg is lowered compared to calcite composition due to partial dissolution of Mg-rich chlorite.

119

The Mg contents of the HAc leachates, comprise on average 27.1% of total Mg for the silt and 28.9% of total Mg for the clay fractions (samples S9-26). The silt fractions of profile S16-26 shows a positive linear correlation between the Ca/Mg of their HAc leachates and their carbonate contents (R2 = 0.97, samples S18, S19 not considered, Appendix Fig. A.2c), which confirms the existence of a two component mix between a high-Mg silicate component (chlorite) and a relatively low-Mg calcareous component. Since Ca is by far the dominant exchangeable cation, the composition of soil waters should be strongly determined by the dissolution of calcite. The NH4Cl leachates, which may reflect the coexisting soil water composition, have much lower Ca/Sr ratios than the HAc leachates (Table 4). The different Ca/Sr ratios for calcite and the NH4Cl leachates, suggests that calcite dissolution proceeded incongruently (McGillen and Fairchild, 2005 and references therein). There is no in situ pedogenic process that produces clayand silt-sized calcite crystals with distinctly different Ca/Sr ratios by dissolution/precipitation from the same coexisting solution. Therefore, silt- and clay-sized carbonate have to be of different provenances, which is in line with the clear isotopic contrast between both calcite fractions (Fig. 9a,b). Silt-sized carbonate represents in situ produced pedogenic carbonate, as its oxygen isotope composition matches the d18Ocarb value that would be obtained for equilibrium calibration between precipitating carbonate and local precipitation for a mean local annual temperature of 7.5 °C (cf. Rowley et al., 2001; Li et al., 2007). The clay-sized carbonates did not precipitate in equilibrium with local meteoric water, thus, they must represent an external component. The heavier oxygen isotope composition of the clay-sized CaCO3 suggests that these calcite crystals precipitated under evaporative conditions, for instance, in shallow lakes that have fallen dry seasonally. The positive correlation between d18Ocarb and d13Ccarb of the clay-sized carbonates (Fig. 9c) is characteristic for carbonates of evaporative systems (e.g. Leng and Marshall, 2004). In closed lakes under an evaporative regime, Mg and Sr become enriched relative to Ca in (Reeves, 1968). Therefore, autochthonous calcite of such lakes would be characterised by lowered Ca/Sr and Ca/Mg values, which is in line with the lower Ca/Sr ratios of the clay-sized carbonates compared to silt-sized CaCO3 (Table 4). The carbon isotope composition of pedogenic CaCO3 correlates with the isotopic composition of the local vegetation but is stronger enriched in 13C due to the carbon isotope fractionation between CO2(gas) and CaCO3(solid) (Cerling, 1984; Cerling et al., 1989). The d13C record of carbonates is used to detect shifts from a C3 to a C4 plant dominated vegetation cover in the past (C3 plants centered around 26 to 28 ‰; C4 plants centered around 12 to 14‰; Craig, 1954; Cerling et al., 1997 and references therein). The relative enrichment of 13C depends mainly on the balance between the two major CO2 components (i) atmospheric CO2 (8‰) and (ii) soil-CO2 produced by plant root respiration and microbial mediated decay of plant remnants (close to biogenic matter composition). The d13C values of the silt-sized carbonates of the Qilian loess correspond with the local C4 plant vegetation cover and dominance of soil-CO2 for authigenic carbonate formation (Fig. 10b). 6.2.2. Temporal trends in carbonate composition The striking positive linear correlations between CO3 of the bulk grain size fractions and Ca in the corresponding HAc leachates (CaHAc) demonstrates that CaHAc predominantly originates from the dissolution of carbonate (clay: S9-15 (R2 = 0.97), S16-26 (R2 = 0.99), silt: S9-15 (R2 = 0.85), S16-26 R2 = 0.85), Appendix Fig. A.2a,b). The Ca/Sr ratios of the silt-sized carbonates of samples S9-26 (HAc leachates) - both elements predominantly originate from

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

CaCO3 dissolution - show a clear inverse correlative trend with the CO3 contents of the bulk silt fractions (R2 = 0.68), whereas the Ca/Sr ratios of the clay-sized carbonates scatter between 1000 and 1500 without showing any correlation with the CO3 contents of the bulk clay (Fig. 14c,d). This also suggests different provenances for the silt- and clay-sized carbonates. The inverse correlation between Ca/Sr and CO3 reflects a systematic variation in the pedogenic formation of calcite related to palaeoenvironmental change. The alternative interpretation of variable contributions of two components, CaCO3 with low Ca/Sr and a HAc leachable non-calcareous component with high Ca/Sr, is not applicable because of the following reason: apatite of high Ca/Sr may contribute to the Ca and Sr contents of the HAc leachates. For a maximum content of 0.026% P2O5 in the HAc leachates of the silt fractions (Appendix Table A.5), the contribution of apatite to the Ca budget (0.019% CaO) is sub-ordinate (e.g. mean silt S9-26: 6.13 wt-% CaO). The slope of the trend line

in the Ca/Sr–CO3 plot, however, demands Ca contributions from both components in a similar order of magnitude, which is in conflict with the balanced CaHAc–CO3 budget of the loess samples (Appendix Fig. A.1). The profile pattern of Sr/Cacarb and carbonate (profile S16-26, Fig. 15a,b). reflect the Holocene climate development in arid central Asia outside of the modern East-Asian summer monsoon front where the effective moisture was low in the early Holocene and relatively enhanced in the mid Holocene (Chen et al., 2008 and references therein). The carbonate minimum around 0.5 normalized depth reflects an increase in aeolian deposition of siliciclastics due to enhanced fluvial transport of river-suspended debris from the high mountain regions to source areas of the dust. Higher wetness additionally may have favoured irreversible in situ dissolution of clay-sized carbonate particles in equilibrium with incongruent crystallization of low-Sr pedogenic carbonates.

0

normalized depth

(c)

(b)

(a)

0.2

bulk S16-26 (silt fractions)

- S19

0.4

HAc leachates S16-26 (silt fractions)

0.6

residual Sr S16 - 26 (silt fractions)

0.8

Sr/Ca (a.r.) x 1000

10

15

CO3 (wt-%)

0.722

5

0.720

0.8

0.718

0.4

0.716

1

87Sr/ 86Sr

0

(f)

(e)

(d)

0.4 HAc-leachates S16 - 26 (silt fractions)

0.6 HAc leachates S16 - 26 (silt fractions)

0.8

0.2

0.4

Mg/Ca (atom ratio)

0.4

0.5

0.6

Mg (wt-%)

87Sr/ 86Sr Fig. 15. (a–f) Depth profiles of selected parameters for the silt fractions of samples S16-26 from Baiyong He valley.

0.7115

0

0.7110

1

0.7105

HAc leachates S16-26 (silt fractions)

0.7100

normalized depth

0.2

121

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

0.724 87Sr/ 86Sr

Carbon isotope compositions of soil organic matter and loess carbonates have been analysed in many Chinese loess profiles from the CLP without discriminating between clay- and silt-sized carbonates. The d13Corg data, which are assumed to reflect closely the vegetation cover, support the common view that the abundance of C4 plants increased from glacials to interglacials on the CLP (increase of d13Corg, e.g. Liu et al., 2005). Rao et al. (2006) summarily state that d13Ccarb shows an opposite trend, i.e., climate change to warmer and wetter conditions typically correlates with a trend to more negative d13Ccarb composition in Chinese loess profiles. In the Qilian Shan loess, corresponding increase in d13Ccarb of silt-sized (pedogenic) carbonates above 0.7 normalized depth documents a development to drier conditions. The d13Ccarb profiles of silt-sized carbonates plot closely together since climate change affects pedogenic carbonate formation at the loess sampling sites in a similar manner. The clay-sized carbonates show a distinctly higher variation range of their d13Ccarb values since they represent a mix of distal components from various provenances. The coinciding increase in Stotal in the clay fractions (Appendix Tables A.1–A.4-2) may reflect enhanced deflation of evaporites in the source regions of the dust.

0.720 0.716 0.712

0

0.2

0.4

0.6

0.8

1

portion residual Sr + bulk model compositions of samples S9-26 + Sr isotope compositions of samples S9-26 for complete release of NH4Cl and HAc leachable Sr average of the bulk clay fractions average of the bulk silt fractions average silicate-bound Sr, clay fractions average silicate-bound Sr, silt fractions average HAc leachable Sr, silt fractions average HAc leachable Sr, clay fractions average NH4Cl leachable Sr, clay and silt fractions

6.3. Sr isotopes 6.3.1. The Sr isotope budget The positive correlations between 1/Sr and 87Sr/86Sr of the bulk silt and clay fractions (Fig. 12b) reflect a two component mixing between a radiogenic component (old silicate-bound Sr) showing relatively low contributions to the total Sr budget (Fig. 11) and a relatively unradiogenic Sr-rich component (sum of NH4Cl and HAc leachable Sr). 87 Sr/86Sr values of the unradiogenic component vary in a rather narrow range (0.71105–0.71179, Table 6) even though the chemical compositions of NH4Cl and HAc leachates differ significantly. The isotope composition of carbonate-bound Sr of the silt and clay fractions from Shiyou He and the Baiyong He valley does not show major systematic variations over a loess accumulation period of 10,000 years. Independently, whether the loess carbonate represents allochthonous components or autochthonous pedogenic CaCO3, the relatively unradiogenic and homogeneous isotopic composition of calcareous-bound Sr implies that both carbonate components precipitated from fluids that received predominantly Sr from weathering of low-Rb/Sr phases. The Rb contents of residual silicates differ for the silt- and claysized samples. Silicate-bound Sr of the Rb-rich clay fractions (average: 0.72466) is by ca. 0.005 87Sr/86Sr units more radiogenic than the residual Sr of the silt-sized debris (average: 0.71963, Table 6). The bulk Sr isotope compositions of the silt and clay fractions, however, are similar (Fig. 12a), as higher contributions of unradiogenic carbonate-bound Sr in the clay fractions camouflage the isotopic contrast between the silicate-bound Sr of the clay and silt fractions. Residues after HAc leaching host the most radiogenic Sr of the Qilian Shan loess. The major carriers of radiogenic Sr in the HAc residues are illite, plagioclase and orthoclase. On average, surface-bound (NH4Cl leachable) Sr accounts for 19% and carbonate-bound (HAc leachable) Sr represents 55% of total Sr in the loess samples from Shiyou He and Baiyong He valley. Since calcareous aeolian deposits in humid areas are strongly affected by carbonate dissolution and element leaching, carbonate dissolution and leaching of weakly bound Sr may significantly modify the initial 87Sr/86Sr value of aeolian deposits under wet climatic conditions (Fig. 16). Post-depositional in situ processes make the tracing of dust sources using bulk 87Sr/86Sr ratios difficult therefore, tracing of dust sources using the Sr isotope composition should base on the silicate fractions of aeolian deposits. Particular

Fig. 16. Strontium isotope compositions of samples S9-26, dependence on the balance between NH4Cl, HAc leachable and silicate-bound Sr components, data plotted against the portions of silicate-bound (residual) Sr, bulk model compositions considering determined silt/clay ratios and contributions from individual Sr components, (dashed line) bulk composition of the clay fractions - development for proportional release of NH4Cl and HAc leachable Sr, (solid line) bulk composition of the silt fractions - development for proportional release of NH4Cl and HAc leachable Sr.

attention should be given to the dependence of grain size composition.

87

Sr/86Sr on the

6.3.2. Temporal trends The isotope composition of carbonate-bound Sr varies only little (e.g. clay fractions S9-15: 0.7113–0.7114, Table 6), except for the silt-sized pedogenic carbonates that show weak upward trends towards lower 87Sr/86Sr values in the order of 0.0004 87Sr/86Sr units (profile S16-26, Fig. 15f). The weak upward decrease in 87Sr/86Sr of the HAc leachates and the inverse correlation between 87Sr/86Sr in HAc leachates and bulk silt carbonate contents may simply reflect smaller contributions of radiogenic Sr from non-calcareous phases in the upper profile section (Fig. 15b,f). The increase in carbonate, d13C and Sr/Ca in the upper section of profile S16-26, which reflect the shift to drier climate, has its correspondence in the Sr isotope record (Figs. 10a and 15a,b). In profile S16-26, the silt-sized silicate fractions show larger changes in the 87Sr/86Sr ratios that are inversely correlated with the contents of silt-sized (pedogenic) carbonate (Fig. 15b,c). Decrease in river discharge lowered the fluvial transport of mineral debris to the large arid basins of Northwest China. At the same time, the decrease of chemical weathering and element leaching would reduce the release of Sr into the dissolved river discharge from high mountain regions including Qilian Shan. In particular, the availability of (fresh) easily weatherable high-Rb/Sr phases (e.g. biotite), which upon aging had developed radiogenic Sr isotope compositions, for aeolian transport may have decreased as a consequence of climate change. 6.3.3. Comparison with loess and sand records from various Chinese sites In Fig. 17, the Sr isotope composition of loess samples from the Shiyou He and Baiyong He valley is compared with a compilation of 87Sr/86Sr data of loess and sand samples from arid and semi-arid

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Fig. 17. Compilation of Sr isotope data of loess and loess-like deposits from Asia, references given inside the diagram, same references marked by colours, analysed loess fractions marked by contours. (see above-mentioned references for further information.

areas in China. The isotopic compositions of NH4Cl, HAc leachable and silicate-bound Sr of the Holocene loess samples from Qilian Shan define two relatively narrow variation ranges. The 87Sr/86Sr isotope ratios of the HAc leachate and the HAc residue of a single loess sample from a nearby sampling site (Jiquan, Nakano et al., 2004) fall into the corresponding variation fields of samples S926. Consistently with our results, Gallet et al. (1996) and Nakano

et al. (2004) document a distinct isotopic contrast between carbonate- and silicate-bound Sr in Chinese loess samples with higher radiogenic compositions for Sr in the silicate fractions. A narrow variation range of carbonate-bound Sr, which closely fits the 87 Sr/86Sr variation field of the HAc and NH4Cl leachates of the samples S9-26, is documented by Yang et al. (2000) for a loess/paleosol sequence of 140 ka from the central Loess Plateau (Luochuan pro-

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

file, Fig. 1). Nakano et al. (2004) document generally unradiogenic compositions of HAc leachable Sr for loess and sand from different provenances in China. The Tarim basin is a potential source area for the atmospheric dust transport through the Hexi Corridor, whereas Tian Shan and Qilian Shan represent natural barriers for the potential transport of mineral aerosols from the Junggar and Qaidam Basin towards the Hexi Corridor (Fig. 1). Actually, the Sr isotope composition of bulk loess (<20 lm fractions, Sun, 2002) from the Tarim basin most closely fits the bulk composition of the samples S9–26 (weighted Siltavs and Clayavs). The 87Sr/86Sr ratios of bulk loess and paleosol samples from the Central Loess Plateau (CLP), which may receive aeolian deposition from a larger source area than Shiyou He and Baiyong He valley, overlap with the variation field of bulk loess from Qilian Shan but show a broader variation range (Jahn et al., 2001). The Sr isotope signatures of the aeolian deposits are more reliably characterised by their silicate fractions, since the 87Sr/86Sr of bulk loess can be changed by pedogenic leaching of weakly- and carbonate-bound Sr (cf. Sections 5.3., 5.4.). The isotopic compositions of silicate-bound Sr (HAc residues) of a long loess profile from Lingtai on the Central Loess Plateau (Wang et al., 2007) and 87 Sr/86Sr data for the silicate fractions of loess samples from a wide range of locations on the CLP and the southern Gobi (Nakano et al., 2004) cover the variation field of silicate-bound Sr of samples S9–26. Silicate-bound Sr in a 2.5 Ma loess/paleosol sequence from Jingchuan, ca. 130 km east off the Lingtai profile (Sun, 2005), analysed in the loess residues after leaching with 2.5 N hydrochloric acid shows distinctly higher 87Sr/86Sr ratios than the Lingtai profile. Leaching with hydrochloric acid obviously increases the contents of mineral components hosting radiogenic Sr in the insoluble residue (see Yokoo et al., 2004 for comparison of leaching experiments with HAc and HCl and resulting changes in the 87Sr/86Sr ratios of the insoluble residues). Shiyou He and Baiyong He valley may receive dust influx from the Badain Jaran or the Tengger desert for meteorological conditions with north-easterly and easterly winds. According to isotope data of silicate-bound Sr in loess and sand from the Tengger desert (Yokoo et al., 2004), substantial material contributions to the Holocene loess sequences from Shiyou He and Baiyong He valley are possible. Sand and silt samples from the Gurbantunggut desert (Jungar Basin, north of Tien Shan, Chen et al., 2007) fall off the 87 Sr/86Sr variation field of silicate-bound Sr defined for the Qilian Shan loess. The latter is also the case for loess and sand samples from North China (Nakano et al., 2004) and the clay and silt fractions of non-calcareous loess samples from NE China.

7. Summary The loess sequences from the Shiyou and Baiyong He valley (S125) are very similar in their grain size and chemical compositions. The provenance of the silt and clay fractions of the Hei He profile (S27-40) is different from these sites. A different geochemical composition of the Hei He loess is manifested by the Al-normalized trace element contents (ME/Al2O3), by the element distribution between the clay and silt fractions (MEclay/MEsilt) and a higher enrichment of Li, Rb, Cs, U and Zn versus UCC composition. The concentrations of conservative elements in the clay fractions of the Qilian Shan loess (e.g. Th, Zr, REE) closely correspond with those of the fine fractions of strongly leached non-calcareous loess (Changchun), whereas chemical elements with relatively higher solubility, e.g. P, Mo, Mn, Cu, Zn, are enriched in the Qilian Shan loess. Carbonate contents of the Quilian Shan loess fall into the variation range of loess from the Central Loess Plateau. In the clay fractions of the Qilian Shan loess, which account from 10%

123

to 25% of the bulk loess, U, Zn, Rb, Pb, Mo, Cu, Li and Cs are strongly enriched compared to the bulk loess from the CLP. This trace element excess is lowered by contributions from coarser materials for the bulk loess. The geochemical composition of the loess profile from Hei He valley, which shows a distinctly higher variability with depth than the other sites, reflects changing contributions from calcareous lake sediments that varied with Holocene climate change. Sediments deposited under an evaporative regime are seen as the major carriers of the trace element excess (e.g. Li, Rb, Cs, Mo, Zn) in the clay fractions of the Qilian Shan loess. Calcite of the silt fractions is identified as an authigenic component that encrusts larger particles, whereas clay-sized calcite particles are allochthonous of remote provenance. Clay and silt-sized carbonates differ in their chemical and in their oxygen and carbon isotope compositions but show similar unradiogenic 87Sr/86Sr values. The oxygen isotope compositions of the silt-sized carbonates closely match the d18Ocarb value that would be obtained for in situ CaCO3 formation in equilibrium with local precipitation. Clay-sized carbonates are characterised by a higher scattering and heavier oxygen isotope compositions which reflects their genesis under evaporative conditions at various remote sites. Loess samples from two Holocene loess sequences from Shiyou He and Baiyong He valley define a rather narrow variation field for the silicate-bound Sr fraction (87Sr/86Sr = 0.720–0.722) for an important global dust source region in northwestern China. Silicate-bound (residual) Sr shows a narrow range of 87Sr/86Sr and depends on grain size composition, which is important when tracing dust of northwestern Chinese provenance in remote natural monitors. Surface- and carbonate-bound Sr show nearly identical Sr isotope compositions that are distinctly less radiogenic than those of the silicate fractions. The mean 87Sr/86Sr value of the bulk loess can be shifted from 0.714 to 0.720 by leaching of weakly bound Sr and chemical dissolution of the loess carbonate. The isotopic contrast of silicate-bound Sr in silt-sized loess (average: 0.7196) and in the clay fractions (average: 0.7247) is camouflaged in the bulk compositions, since CaCO3, which hosts unradiogenic Sr, occurs at significantly higher contents in the clay fractions than in the silt fractions. Silicate-bound Sr of Holocene loess from Shiyou and Bayong He valley falls within the 87Sr/86Sr variation range of HAc leached Pleistocene loess from the Central Loess Plateau. The loess sequences from Qilian Shan show depth (age) trends which are in line with climate change to drier conditions after the mid Holocene. (i) Clay fractions S27-40 show a distinct increase in allochthonous carbonate, Stotal/Al2O3, in the Al-normalized Li, Rb and Cs contents and decrease of Ce/Ce*, which reflects relatively enhanced contributions by sediments from dry lake basins; (ii) corresponding increase of Stotal in the clay fractions of the profiles S1-8 and S16-26; (iii) d13Ccarb increase of the silt- and clay-sized carbonates; and (iv) coinciding decrease of 87Sr/86Sr in the silt-sized silicate fraction of profile S16-26 and decrease in sand contents (S27-40) reflecting reduced fluvial delivery of fresh mineral debris, hosting radiogenic Sr, to the source areas of the dust. Acknowledgements We acknowledge technical support by Andreas Hendrich (Figures), Ursula Kegel, Birgit Zander, Robert Herrendörfer (analytical assistance). We thank R. Naumann for XRD analyses of selected HAc residues, Prof. Ralf Hetzel (University of Münster) for making sample material available and Prof. Fahu Chen (Lanzhou University) for organizing our field expedition to Qilian Shan. We highly appreciate constructive reviews by Prof. S. Gallet and an anonymous reviewer and thoughtful editorial comments by Prof. Borming Jahn. This study was partially supported by the National Science Foundation of China (No. 40671192).

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Appendix A See Appendix Figures and Tables.

(a) 20

silt fractions

CaO (wt-%)

10

0

CaO, NH4Cl leachates CaO, NH4Cl + HAc leachates bulk CaO analysed normative carbonate-bound CaO

(b) 20

clay fractions 10

S 16 S 17 S 18 S 19 S 20 S 21 S 22 S 23 S 24 S 25 S 26

S9 S 10 S 11 S 12 S 13 S 14 S 15

0

Fig. A.1. Loess sequences S9-15 and S16-26. The CaO budgets of the clay and silt fractions.

10

(a)

Ca/Mg (atom ratio)

CaHAc (wt-%)

15

clay fractions

10

R²= 0.97 R²= 0.99

5

0 12

16

(b)

R²= 0.97 4

HAc leachates silt fractions (without S18,19)

6

R²= 0.82

2

R²=

10

12

14

(d)

6 4

8

S16-26

silt fractions Mg/Sr (a.r)

(wt-%)

6

20 S9-15,

8

HAc

calcite

chlorite

2 8

Ca

(c) 8

400

200

0.85

R²= 0.89 HAc leachates silt fractions (without S19)

calcite

chlorite 0

6

8 10 bulk CO3 (wt-%)

12

14

6

8 10 bulk CO 3 (wt-%)

12

14

Fig. A.2. (a–d) Chemical compositions of HAc leachates – correlations with carbonate contents. The Ca and Sr contents of the HAc leachates originate mainly from dissolution of low-Mg calcite, Mg is dominantly contributed by dissolution of Mg-rich chlorite, the correlative trends of Ca/Mg and Mg/Sr with CO3 reflect variable contributions of both phases in the HAc leachates.

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

125

Table A.1 Chemical composition profile Shiyou He (samples S1-8).

*

Measured by ICP-MS, normalized concentration data SX/Smean are plotted in bold numbers if their scattering around their average values significantly exceed the analytical uncertainty range, significant negative and positive deviations are highlighted by red and green, respectively, in the web version of the article.

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G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Table A.2 Chemical composition profile Shiyou He (samples S9-15), Upper Continental Crust (UCC) composition after Rudnick and Gao (2004) and average rare earth element contents of 27 Post-Archean Australian Shales (PAAS, Taylor and McLennan, 1985).

*

Measured by ICP-MS, normalized concentration data SX/Smean are plotted in bold numbers if their scattering around their average values significantly exceed the analytical uncertainty range, significant negative and positive deviations are highlighted by red and green, respectively, in the web version of the article.

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

127

Table A.3 Chemical composition profile Baiyong He (samples S16-25).

*Measured by ICP-MS, normalized concentration data SX/Smean are plotted in bold numbers if their scattering around their average values significantly exceed the analytical uncertainty range, significant negative and positive deviations are highlighted by red and green, respectively, in the web version of the article.

128

Table A.4-1 Chemical composition profile Hei He (samples S27-40). S27

S28

S29

S30

S31

S32

S33

S34

S35

S36

S37

S38

S39

S40

mean

RSD (%)

9.32 4.00 0.079 2.88 6.65 1.80 1.93 0.670 0.153 0.019 8.47

9.57 4.14 0.082 2.94 6.89 1.79 1.98 0.695 0.159 0.022 8.37

9.73 4.23 0.082 2.81 6.81 1.74 2.06 0.683 0.151 0.028 7.73

9.79 4.27 0.087 2.82 6.63 1.80 2.01 0.728 0.160 0.023 6.85

9.72 4.27 0.087 2.77 7.36 1.75 2.03 0.691 0.171 0.027 8.18

9.51 4.19 0.083 2.69 6.53 1.80 1.97 0.711 0.165 0.015 7.17

9.74 4.21 0.082 2.69 6.58 1.79 2.02 0.685 0.148 0.016 7.40

9.83 4.34 0.083 2.70 6.24 1.80 2.04 0.696 0.139 0.016 7.38

9.79 4.10 0.087 2.85 7.87 1.79 2.10 0.631 0.152 0.021 9.01

9.28 4.14 0.082 2.66 6.71 1.84 1.97 0.682 0.139 0.014 7.74

9.78 4.34 0.086 2.70 6.87 1.84 2.02 0.720 0.160 0.015 7.79

9.72 4.31 0.085 2.66 6.32 1.81 2.03 0.690 0.151 0.014 7.26

10.1 4.68 0.099 2.94 7.57 1.82 2.10 0.710 0.157 0.021 7.53

9.69 4.24 0.085 2.79 6.83 1.80 2.02 0.689 0.153 0.019 7.80

2.1 3.6 5.4 3.9 6.6 1.5 2.3 3.7 5.9 23.7 7.4

25.3 1.42 9.6 71.5 74.9 9.1 35.1 28.5 48.7 75.1 184 19.6 97.3 0.72 4.24 468 35.7 72.3 8.33 31.7 6.10 1.19 5.21 0.71 4.07 0.78 2.22 0.31 2.15 0.31 16.6 11.8 2.69

26.9 1.48 9.8 73.3 77.0 9.6 35.2 29.4 50.3 78.5 195 20.8 107 0.84 4.60 463 40.8 82.5 9.43 35.4 6.78 1.25 5.67 0.79 4.43 0.85 2.39 0.32 2.28 0.33 17.6 13.3 3.05

27.9 1.51 10.0 74.8 85.4 9.2 36.5 31.9 53.9 81.8 201 20.8 110 1.02 4.74 470 39.9 80.5 9.22 34.7 6.80 1.22 5.66 0.78 4.50 0.85 2.45 0.33 2.31 0.34 18.5 13.5 3.15

24.8 1.54 10.4 78.6 87.2 11.9 41.0 31.8 54.5 78.3 203 21.0 105 0.96 4.17 496 36.8 74.7 8.51 32.2 6.29 1.20 5.17 0.75 4.34 0.80 2.38 0.32 2.22 0.33 19.0 12.6 2.90

26.2 1.52 10.3 77.5 83.2 12.2 41.2 30.2 54.0 78.3 221 20.6 95.2 1.03 4.38 488 38.3 76.5 8.75 33.3 6.27 1.19 5.16 0.74 4.27 0.79 2.31 0.32 2.18 0.31 17.1 13.2 2.81

24.1 1.52 10.3 76.6 85.6 11.5 40.6 27.5 51.2 75.5 212 21.1 106 0.91 3.87 454 38.7 76.6 8.73 33.3 6.32 1.21 5.21 0.76 4.30 0.81 2.34 0.32 2.24 0.33 16.8 12.6 2.78

25.0 1.56 10.2 76.6 77.6 10.8 39.8 28.1 51.2 77.2 274 20.0 90.1 0.90 4.11 481 35.3 71.1 8.19 31.3 6.06 1.13 4.91 0.71 4.16 0.76 2.25 0.32 2.13 0.31 16.3 12.8 2.70

24.7 1.57 10.5 78.8 88.9 11.2 41.1 29.8 50.7 77.1 260 20.6 101 1.02 3.96 496 37.9 75.8 8.59 32.6 6.21 1.20 5.04 0.71 4.19 0.78 2.24 0.33 2.20 0.33 17.5 12.6 2.88

27.7 1.58 10.0 75.2 77.9 11.9 41.1 28.9 53.8 81.8 242 19.3 80.0 1.04 4.65 478 33.5 66.5 7.66 28.9 5.62 1.10 4.80 0.67 3.89 0.72 2.14 0.29 1.99 0.30 17.2 11.7 2.68

23.0 1.46 9.9 76.2 90.9 11.3 39.9 28.0 47.8 74.4 204 20.3 104 0.92 3.56 472 38.6 77.0 8.72 33.0 6.36 1.15 5.19 0.74 4.15 0.79 2.28 0.32 2.18 0.31 16.3 13.4 2.90

24.9 1.61 10.5 80.0 89.5 10.9 39.6 29.0 51.3 76.9 216 21.6 112 0.95 4.06 484 40.0 80.1 9.15 34.7 6.70 1.19 5.62 0.77 4.44 0.83 2.41 0.33 2.29 0.34 16.7 14.6 3.04

23.9 1.53 10.3 78.2 96.3 10.7 40.5 28.2 49.7 76.7 202 20.8 103 0.94 3.87 493 37.8 75.6 8.71 32.7 6.44 1.18 5.28 0.73 4.36 0.80 2.34 0.32 2.19 0.33 16.5 12.5 2.99

28.5 1.65 10.9 85.8 99.9 14.4 47.6 35.3 58.4 82.7 243 21.5 98 0.92 4.99 567 37.6 75.2 8.59 32.5 6.24 1.22 5.36 0.76 4.29 0.82 2.30 0.32 2.23 0.33 17.8 13.1 3.28

25.8 1.53 10.2 76.8 84.2 11.0 39.7 29.7 52.1 78.3 217 20.5 100 0.92 4.29 486 37.6 75.3 8.62 32.6 6.29 1.18 5.23 0.74 4.24 0.80 2.30 0.32 2.19 0.32 17.2 12.8 2.91

6.6 3.7 3.3 4.5 10.6 12.3 7.8 6.8 5.1 3.4 12.2 3.7 8.5 10.0 9.4 5.3 5.3 5.5 5.2 5.1 5.0 3.3 5.1 4.4 4.0 4.4 3.9 3.1 3.9 4.5 4.5 6.0 5.9

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

63–2 lm fractions (Wt-%) 9.73 Al2O3 4.12 Fe2O3T MnO 0.081 MgO 2.97 CaO 6.60 1.79 Na2O 2.05 K2O 0.650 TiO2 0.144 P2O5 0.021 Stotal CO3 8.32 (lg/g) Li 28.0 Be 1.52 Sc 9.8 V 72.6 Cr 64.5 Co 9.6 Ni 36.6 Cu 28.6 Zn 53.3 * Rb 82.6 Sr 186 Y 18.9 Zr 91.3 * Mo 0.77 * Cs 4.80 Ba 498 * La 35.2 * Ce 70.5 * Pr 8.10 * Nd 30.3 * Sm 5.94 * Eu 1.14 * Gd 4.92 * Tb 0.70 * Dy 4.01 * Ho 0.75 * Er 2.16 * Tm 0.32 * Yb 2.04 * Lu 0.29 * Pb 16.9 * Th 11.7 * U 2.89

*

14.6 7.10 0.134 4.80 8.41 0.75 3.25 0.627 0.168 0.072 9.68

14.3 6.90 0.119 5.13 9.45 0.68 3.27 0.553 0.162 0.089 10.5

13.9 6.65 0.125 4.95 10.81 0.71 3.15 0.586 0.158 0.103 12.2

14.9 6.72 0.111 5.39 9.23 0.64 3.49 0.516 0.150 0.076 10.49

14.4 6.75 0.117 4.54 10.4 0.66 3.31 0.528 0.151 0.092 11.9

15.5 7.56 0.161 4.57 7.44 0.77 3.37 0.661 0.155 0.044 8.15

15.8 7.77 0.158 4.58 7.29 0.69 3.46 0.634 0.158 0.050 7.88

15.5 7.68 0.152 4.57 7.20 0.74 3.45 0.615 0.157 0.053 7.70

15.1 7.01 0.112 4.40 9.55 0.66 3.45 0.529 0.137 0.083 10.5

14.9 7.12 0.131 4.19 8.41 0.82 3.31 0.617 0.136 0.054 9.26

15.9 7.65 0.139 4.47 6.46 0.75 3.50 0.642 0.140 0.044 6.97

15.2 7.47 0.143 4.19 5.98 0.92 3.28 0.671 0.142 0.033 6.74

15.7 7.89 0.150 4.42 7.11 0.74 3.45 0.646 0.125 0.047 7.71

15.0 7.24 0.135 4.65 8.21 0.74 3.36 0.603 0.151 0.065 9.15

4.0 5.6 11.9 7.2 17.5 9.6 3.0 8.3 9.1 31.8 18.7

62.6 2.60 16.5 122 87.0 19.9 63.9 65.7 112 161 180 22.1 92.9 1.85 14.4 500 36.7 74.3 8.18 31.5 5.97 1.18 5.11 0.77 4.55 0.88 2.63 0.36 2.47 0.355 31.5 15.4 3.93

63.4 2.59 16.4 118 81.6 18.9 64.2 68.6 119 160 213 19.6 85.9 1.84 14.6 517 32.3 65.8 7.34 27.4 5.29 1.07 4.60 0.67 4.02 0.77 2.31 0.33 2.23 0.331 28.2 14.0 4.49

56.9 2.55 15.4 115 85.8 19.1 68.0 77.3 115 138 238 19.3 76.2 2.12 12.1 467 32.1 65.6 7.20 26.7 5.14 1.06 4.42 0.64 3.79 0.76 2.18 0.31 2.09 0.312 27.4 14.2 3.81

59.1 2.74 16.6 119 93.2 18.5 67.4 76.2 116 142 228 18.8 77.4 1.88 13.2 564 29.2 59.0 6.60 24.7 4.89 0.97 4.23 0.61 3.69 0.72 2.11 0.30 2.03 0.298 26.1 13.5 3.71

56.6 2.74 16.9 116 93.1 19.2 68.8 80.3 114 137 295 20.2 83.7 2.08 12.9 572 31.1 62.1 6.98 26.2 5.12 1.04 4.35 0.64 3.89 0.75 2.21 0.32 2.10 0.314 28.3 14.4 3.42

59.2 2.85 18.2 128 107 24.3 82.2 79.8 128 140 237 25.0 99.7 2.71 12.8 651 38.8 79.9 8.81 33.1 6.61 1.30 5.52 0.81 4.86 0.94 2.73 0.38 2.60 0.386 38.1 17.4 3.71

60.3 2.90 18.8 130 109 22.9 83.4 78.5 127 143 256 25.2 104 2.84 12.9 670 38.4 79.2 8.72 33.2 6.43 1.31 5.57 0.84 5.01 0.96 2.80 0.39 2.64 0.403 38.6 17.7 3.98

60.7 2.96 19.4 129 106 23.4 82.9 88.2 134 150 249 25.5 100 2.64 13.8 647 37.2 77.2 8.62 32.5 6.35 1.31 5.68 0.86 4.99 0.95 2.81 0.40 2.64 0.389 37.4 17.2 4.22

60.7 2.87 17.3 124 94.9 20.1 74.8 81.3 117 146 311 20.0 85.0 2.46 13.9 502 30.5 63.1 6.83 26.1 4.98 1.01 4.33 0.64 3.82 0.75 2.26 0.32 2.14 0.317 30.7 14.5 4.30

58.2 2.78 17.1 122 97.5 21.0 75.5 81.9 116 141 246 23.0 90.0 2.49 12.7 501 35.4 73.5 8.07 30.7 6.04 1.21 5.20 0.76 4.58 0.88 2.59 0.36 2.44 0.353 33.0 15.8 4.36

63.0 2.92 18.7 130 103 22.1 75.4 88.2 129 143 224 23.9 103.6 2.30 13.7 526 35.9 74.8 8.13 31.1 6.01 1.23 5.30 0.75 4.54 0.90 2.63 0.37 2.55 0.374 35.8 16.8 4.65

56.7 2.77 17.9 127 100 21.7 78.5 81.5 112 141 217 24.6 101.6 2.63 11.9 598 38.6 79.9 8.78 33.2 6.46 1.31 5.67 0.82 4.83 0.95 2.74 0.39 2.56 0.382 35.7 17.4 4.57

59.6 2.85 18.9 134 110 24.9 89.6 96.1 128 144 237 24.4 99.5 2.33 12.6 615 38.2 79.4 8.66 33.0 6.41 1.29 5.68 0.82 4.88 0.94 2.72 0.38 2.60 0.394 37.1 17.8 5.04

59.9 2.77 17.5 124. 97 21.1 74.6 79.2 121 146 237 22.4 92.4 2.30 13.3 562 35.0 71.9 7.92 30.0 5.82 1.18 5.05 0.74 4.42 0.86 2.52 0.35 2.40 0.35 32.8 15.8 4.25

3.7 4.6 6.5 4.5 8.8 9.6 10.3 10.4 5.8 5.7 14.3 10.5 10.0 14.1 6.0 11.2 9.1 9.8 9.6 10.0 10.2 10.0 10.7 11.2 10.5 10.0 9.5 9.2 9.1 9.5 12.7 9.4 12.1

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

<2 lm fractions (Wt-%) 14.6 Al2O3 Fe2O3T 7.14 MnO 0.134 MgO 4.92 CaO 7.20 0.77 Na2O 3.36 K2O 0.614 TiO2 P2O5 0.180 0.071 Stotal 8.37 CO3 (lg/g) Li 62.0 Be 2.64 Sc 16.7 V 122 Cr 95.0 Co 19.9 Ni 68.9 Cu 65.7 Zn 124 * Rb 162 Sr 191 Y 21.8 Zr 93.8 * Mo 2.06 * Cs 14.1 Ba 535 * La 35.6 * Ce 72.2 * Pr 7.96 * Nd 30.7 * Sm 5.78 * Eu 1.19 * Gd 5.02 * Tb 0.71 * Dy 4.43 * Ho 0.86 * Er 2.56 * Tm 0.35 * Yb 2.45 * Lu 0.361 * Pb 31.7 * Th 15.2 * U 5.29 Measured by ICP-MS.

129

130

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

Table A.4-2 Chemical composition profile Hei He (samples S27-40), normalized versus mean values.

*Measured by ICP-MS, normalized concentration data SX/Smean are plotted in bold numbers if their scattering around their average values significantly exceed the analytical uncertainty range, significant negative and positive deviations are highlighted by red and green, respectively, in the web version of the article.

Table A.5 Chemical composition HAc leachates S9-26. S9

S10

S11

S12

S13

S14

S15

S16

S17

Shiyou He

S19

S20

S21

S22

S23

S24

S25

S26

Baiyong He

0.049 0.316 0.039 1.238 7.49 0.010

0.056 0.272 0.039 1.161 6.02 0.010

0.047 0.252 0.036 0.916 6.20 0.010

0.057 0.284 0.040 1.042 6.78 0.012

0.071 0.341 0.040 1.089 8.55 0.019

0.048 0.311 0.032 1.005 7.57 0.009

0.037 0.218 0.033 0.689 4.94 0.007

0.038 0.255 0.035 0.747 6.64 0.009

0.043 0.286 0.034 0.880 5.87 0.009

0.036 0.238 0.032 0.826 4.12 0.008

0.058 0.251 0.040 0.813 5.12 0.012

0.051 0.228 0.029 0.762 4.32 0.012

0.049 0.220 0.028 0.750 4.55 0.010

0.046 0.214 0.028 0.725 4.51 0.010

0.043 0.217 0.030 0.744 5.52 0.009

0.046 0.297 0.031 0.786 7.08 0.011

0.039 0.297 0.030 0.775 7.73 0.009

0.021 0.007 31.8 4.35

0.018 0.005 26.0 3.72

0.014 0.005 24.6 4.86

0.014 0.006 23.2 4.68

0.017 0.010 19.4 5.64

0.012 0.007 26.3 5.42

0.019 0.003 23.6 5.15

0.010 0.010 24.6 6.39

0.022 0.006 26.0 4.80

0.026 0.004 29.3 3.58

0.025 0.005 17.7 4.52

0.019 0.004 19.0 4.07

0.018 0.005 19.4 4.36

0.020 0.004 19.7 4.47

0.009 0.003 22.0 5.33

0.015 0.006 21.6 6.47

0.006 0.007 25..3 7.16

1.11

1.24

1.08

1.50

1.84

1.41

0.81

1.13

0.97

0.80

1.21

1.04

1.03

1.13

0.93

1.15

1.10

1.79

1.68

1.64

1.94

1.98

1.92

1.33

1.60

1.42

1.29

1.59

1.54

1.28

1.38

1.56

1.99

1.94

3.14 69.4 4.05

3.00 55.0 4.03

2.70 57.7 4.17

3.28 69.2 4.09

3.67 97.5 3.66

3.31 86.7 3.81

3.01 46.6 2.81

2.46 69.1 2.52

3.71 52.2 2.97

3.06 28.5 2.57

3.14 44.7 3.22

3.27 31.9 2.96

2.83 36.3 3.00

3.02 33.9 2.65

3.69 45.1 3.23

3.38 68.1 3.78

2.51

0.011 30.1 4.18 7.48 1.07 4.28 0.95 0.20 0.92 0.14 0.75 0.15 0.35 0.05 0.30 0.04 4.13 0.61 0.51

0.009 23.8 4.23 7.40 1.06 4.29 0.92 0.21 0.92 0.13 0.76 0.14 0.38 0.04 0.28 0.04 3.83 0.68 0.48

0.007 26.6 4.27 7.12 1.11 4.47 1.01 0.21 0.98 0.14 0.81 0.15 0.38 0.05 0.28 0.04 3.46 0.62 0.36

0.011 26.1 4.18 7.39 1.07 4.34 0.99 0.21 0.97 0.15 0.78 0.14 0.38 0.05 0.27 0.04 3.69 0.48 0.35

0.013 41.1 3.55 6.31 0.91 3.76 0.83 0.18 0.87 0.12 0.65 0.12 0.31 0.04 0.21 0.03 3.92 0.19 0.53

0.012 39.0 3.78 6.70 1.00 3.96 0.91 0.20 0.91 0.13 0.73 0.13 0.33 0.05 0.24 0.04 3.70 0.39 0.34

0.019 20.5 2.91 5.21 0.75 3.09 0.68 0.16 0.68 0.10 0.55 0.10 0.26 0.03 0.19 0.02 3.37 0.32 0.20

0.016 18.0 2.69 4.53 0.66 2.65 0.58 0.13 0.60 0.08 0.46 0.08 0.19 0.03 0.16 0.02 3.70 0.20 0.33

0.020 24.5 3.16 5.65 0.79 3.22 0.71 0.16 0.73 0.10 0.57 0.11 0.26 0.04 0.21 0.03 3.62 0.37 0.33

0.016 20.3 2.68 5.14 0.69 2.82 0.64 0.13 0.64 0.09 0.49 0.09 0.24 0.03 0.18 0.03 3.04 0.31 0.29

0.012 28.8 3.41 5.88 0.87 3.62 0.81 0.18 0.81 0.11 0.60 0.11 0.25 0.03 0.19 0.03 3.74 0.28 0.36

0.016 24.4 3.04 5.42 0.78 3.17 0.75 0.15 0.73 0.10 0.56 0.11 0.26 0.03 0.19 0.03 3.26 0.28 0.26

0.010 19.0 3.08 5.36 0.79 3.30 0.74 0.15 0.72 0.10 0.53 0.10 0.26 0.03 0.20 0.03 3.13 0.30 0.27

0.013 24.8 2.68 4.72 0.70 2.88 0.63 0.14 0.63 0.10 0.50 0.10 0.22 0.03 0.17 0.02 3.06 0.28 0.28

0.016 24.1 3.48 6.23 0.89 3.55 0.76 0.18 0.80 0.11 0.62 0.11 0.30 0.04 0.23 0.03 3.33 0.49 0.26

0.012 28.2 3.94 7.12 1.00 4.08 0.91 0.21 0.90 0.13 0.72 0.13 0.33 0.04 0.26 0.03 3.85 0.39 0.34

0.008 34.7 4.05 7.29 1.03 4.22 0.88 0.20 0.91 0.13 0.70 0.14 0.33 0.04 0.26 0.04 3,76 0,58 0,34

3.79

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

63–2 lm fractions (Wt-%) 0.055 Al2O3 0.269 Fe2O3T MnO 0.041 MgO 1.091 CaO 7.26 0.009 Na2O K2O TiO2 P2O5 0.022 0.007 Stotal Mg/Al 25.2 Ca/Mg 4.78 (lg/g) * Li 1.25 Be Sc V Cr * Co 1.77 Ni Cu Zn * Rb 3.20 Sr 74.5 * Y 4.48 Zr * Mo * Cs 0.008 * Ba 30.3 * La 4.65 * Ce 7.88 * Pr 1.16 * Nd 4.80 * Sm 1.10 * Eu 0.23 * Gd 1.07 * Tb 0.15 * Dy 0.86 * Ho 0.16 * Er 0.41 * Tm 0.05 * Yb 0.31 * Lu 0.04 * Pb 4.42 * Th 0.57 * U 0.57

S18

(continued on next page) 131

132

Table A.5 (continued) S9

*

S10

S11

S12

S13

S14

S15

S16

S17

S18

S19

S20

S21

S22

S23

S24

S25

S26

0.158 0.542 0.069 1.316 11.5 0.022

0.186 0.591 0.075 1.467 8.9 0.024

0.185 0.627 0.071 1.250 10.0 0.022

0.115 0.445 0.059 1.164 11.1 0.022

0.144 0.527 0.050 1.379 14.4 0.028

0.153 0.635 0.056 1.235 11.0 0.017

0.162 0.564 0.085 0.901 7.01 0.012

0.126 0.466 0.068 1.136 15.0 0.025

0.136 0.560 0.082 1.217 14.0 0.026

0.114 0.453 0.073 1.161 13.7 0.025

0.130 0.479 0.070 1.153 12.7 0.025

0.130 0.467 0.066 1.364 13.5 0.029

0.118 0.434 0.063 1.248 13.9 0.028

0.117 0.436 0.063 1.170 14.1 0.029

0.143 0.505 0.054 1.202 12.9 0.027

0.125 0.478 0.054 1.178 15.0 0.027

0.126 0.436 0.045 1.273 14.9 0.026

0.045 0.026 10.6 6.27

0.046 0.027 10.0 4.38

0.039 0.027 8.6 5.74

0.026 0.018 12.8 6.87

0.037 0.029 12.1 7.48

0.016 0.019 10.2 6.41

0.023 0.016 7.0 5.59

0.024 0.065 11.4 9.50

0.027 0.044 11.3 8.24

0.037 0.029 12.9 8.49

0.025 0.026 11.2 7.91

0.022 0.036 13.3 7.11

0.024 0.040 13.4 7.98

0.023 0.045 12.7 8.66

0.024 0.033 10.6 7.72

0.018 0.027 11.9 9.13

0.018 0.039 12.7 8.40

3.54

3.97

3.96

3.29

3.59

3.58

2.58

3.18

3.15

3.25

3.33

3.53

3.47

3.30

3.65

3.41

3.41

3.13

3.03

3.30

2.66

2.61

2.75

3.47

3.30

3.26

2.76

2.91

2.98

2.20

2.33

2.79

3.58

3.53

2.83 131 8.95

3.08 137 8.82

3.52 124 8.33

2.91 141 7.12

3.09 185 6.05

2.68 167 6.57

3.08 61.4 6.12

3.38 164 6.08

3.35 152 7.72

3.82 134 7.68

3.83 136 7.53

3.21 164 8.60

3.07 158 7.78

3.28 184 6.47

3.36 175 8.58

3.41 192 8.70

3.03

0.009 44.4 8.86 14.3 2.29 9.46 2.14 0.45 2.19 0.31 1.68 0.30 0.77 0.10 0.55 0.08 6.51 0.85 1.60

0.009 42.8 8.89 14.1 2.29 9.59 2.16 0.47 2.18 0.30 1.67 0.30 0.75 0.10 0.57 0.09 6.08 0.90 1.43

0.009 39.3 8.28 13.6 2.15 8.88 2.02 0.44 2.14 0.28 1.58 0.29 0.72 0.09 0.50 0.08 6.56 0.81 1.02

0.009 42.1 7.23 11.4 1.86 7.64 1.76 0.38 1.78 0.25 1.35 0.24 0.60 0.07 0.43 0.06 5.25 0.53 0.84

0.012 64.8 6.00 10.4 1.57 6.38 1.51 0.32 1.53 0.20 1.09 0.20 0.49 0.06 0.34 0.05 5.91 0.38 0.99

0.008 53.7 6.47 10.8 1.67 7.10 1.66 0.35 1.63 0.22 1.20 0.21 0.53 0.06 0.36 0.06 5.21 0.46 0.86

0.021 54.0 7.27 12.2 1.78 7.34 1.63 0.37 1.66 0.23 1.20 0.22 0.53 0.06 0.37 0.05 8.29 0.64 0.49

0.026 39.6 6.99 11.7 1.69 6.76 1.44 0.32 1.51 0.21 1.13 0.21 0.53 0.06 0.35 0.05 8.36 0.44 0.69

0.024 53.3 8.62 14.1 2.10 8.63 1.92 0.43 1.86 0.27 1.46 0.26 0.67 0.09 0.47 0.07 8.66 0.67 0.96

0.023 52.5 8.93 13.2 2.15 8.90 1.94 0.44 1.92 0.27 1.48 0.27 0.69 0.08 0.48 0.07 6.36 0.47 1.04

0.016 55.4 8.49 13.3 2.11 8.78 1.89 0.42 1.89 0.26 1.42 0.26 0.68 0.08 0.47 0.07 6.93 0.52 0.90

0.015 61.6 9.08 15.3 2.28 9.42 2.10 0.44 2.08 0.29 1.60 0.30 0.76 0.09 0.54 0.08 7.19 0.54 0.89

0.013 40.6 8.41 13.7 2.05 8.61 1.87 0.41 1.94 0.26 1.51 0.27 0.66 0.09 0.50 0.07 6.33 0.48 0.88

0.014 57.8 6.77 11.1 1.68 6.89 1.58 0.33 1.52 0.21 1.19 0.22 0.54 0.07 0.39 0.06 6.12 0.40 0.85

0.013 59.1 8.82 14.5 2.22 9.30 2.04 0.44 2.08 0.30 1.62 0.29 0.76 0.09 0.54 0.09 6.98 0.71 0.87

0.014 68.6 8.65 14.9 2.23 9.44 2.12 0.44 2.17 0.30 1.67 0.32 0.78 0.09 0.53 0.08 7.22 0.51 0.98

0.010 66.0 7.76 13.4 2.01 8.26 1.86 0.40 1.86 0.26 1.46 0.27 0.66 0.08 0.46 0.07 6.61 0.64 0.99

Analysed by ICP-MS, Mg/Al and Ca/Mg given as atom ratios.

7.30

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

<2 lm fractions (Wt-%) Al2O3 0.158 0.493 Fe2O3T MnO 0.083 MgO 1.259 CaO 8.27 0.016 Na2O K2O TiO2 P2O5 0.044 0.017 Stotal Mg/Al 10.1 Ca/Mg 4.72 (lg/g) * Li 2.98 Be Sc V Cr * Co 3.24 Ni Cu Zn * Rb 3.15 Sr 101 * Y 8.92 Zr * Mo * Cs 0.011 * Ba 42.2 * La 7.92 * Ce 13.7 * Pr 2.05 * Nd 8.52 * Sm 2.01 * Eu 0.42 * Gd 1.98 * Tb 0.28 * Dy 1.51 * Ho 0.28 * Er 0.71 * Tm 0.08 * Yb 0.50 * Lu 0.07 * Pb 6.99 * Th 0.79 * U 1.26

Table A.6 Analytical results of reference materials, comparison with recommended values. JLk-1 (GSJ), fresh water sediment, Lake Biwa ICP-AES

(lg/g) Li Be Sc V Cr Co Ni Cu Zn Rb Sr Y Zr Mo Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pb Th U

m

s

16.8 6.7 0.264 1.70 0.653 1.065 2.76 0.681 0.213 0.0861

0.2 0.1 0.004 0.02 0.005 0.01 0.03 0.009 0.002 0.0006

52.3 2.93 14.8 114 56 17.3 36.3 61.4 143

0.7 0.04 0.2 1 1 0.2 0.4 0.4 2

67.1 34.9 89

0.6 0.2 3

574 40.4

7 0.5

m

JSd-2 (GSJ), stream sediment, composite sample Reference

s

1.63 0.682

0.01 0.006

0.68

0.01

53.0

0.5

17.8 37 64 163 143 67 36.7 87 1.7 12.6 562 41.1 88 9.7 37.0 7.7 1.264 7.23 1.14 6.87 1.36 3.96 0.561 3.77 0.55 45.2 18.6 3.80

0.2 1 1 2 2 1 0.6 1 0.1 0.1 8 0.8 1 0.1 0.4 0.1 0.005 0.09 0.01 0.02 0.01 0.06 0.023 0.06 0.01 0.4 0.1 0.05

ICP-AES

ICP-MS

m

s

m

s

16.73 6.929 0.266 1.736 0.686 1.051 2.805 0.668 0.208 0.1052

0.18 0.219 0.0174 0.0548 0.0324 0.0482 0.0544 0.0301 0.00622 0.0090

12.1 11.34 0.1198 2.59 3.49 2.397 1.099 0.579 0.102 1.2679

0.08 0.09 0.0009 0.01 0.017 0.005 0.007 0.004 0.001 0.0067

51.5 3.31 15.9 117 69 18.0 35.0 62.9 152 147 67.5 40.0 137 2.19 10.9 574 40.6 87.9 8.53 35.7 7.87 1.27 6.02 1.230 6.57 1.06 3.59 0.531 3.99 0.571 43.7 19.5 3.83

2.79 0.48 0.44 7.55 3.4 0.72 3.12 4.92 10 10.8 4.56 5.52 8.7 0.41 1.89 43.8 1.33 9.49 1.64 5.24 0.45 0.069 0.82 0.12 0.79 0.420 0.42 0.097 0.34 0.079 3.69 0.92 0.4

20.6 0.97 16.4 125.8 95.6 45.9 89.2 1077 1940

0.2 0.01 0.1 0.5 0.1 0.2 0.4 9 18

194.7 14.4 50

1.1 0.5 27

1186 10.5

10 0.2

m

GSMS-2 (IRMA), mix marine sedim., Eastern Pacific Ocean

Reference s

2.51 3.44

0.03 0.05

0.576

0.006

20.0

0.3

47.2 92 1049 2100 26.7 197 14.9 31 15.2 1.019 1174 10.9 21.9 2.88 12.0 2.78 0.83 2.78 0.45 2.86 0.60 1.682 0.230 1.43 0.20 153.4 2.27 0.97

0.7 2 5 24 0.3 1 0.1 1 0.2 0.009 17 0.2 0.5 0.04 0.2 0.05 0.03 0.05 0.01 0.04 0.02 0.008 0.002 0.05 0.01 4.0 0.09 0.02

ICP-AES

ICP-MS

m

s

m

s

12.31 11.65 0.120 2.731 3.658 2.438 1.145 0.614 0.105 1.3100

0.164 0.386 0.00815 0.0717 0.0534 0.0841 0.0275 0.0466 0.0222 0.0640

11.09 5.79 0.585 2.85 5.53 4.48 2.24 0.571 0.469 0.2828

0.08 0.06 0.004 0.01 0.02 0.01 0.01 0.004 0.003 0.0021

19.2 1.04 17.5 125 108 48.4 92.8 1117 2056 26.9 202 17.4 111 11.5 1.07 1199 11.3 23.4 2.40 13.2 2.68 0.81 2.67 0.440 2.86 0.678 1.48 0.23 1.67 0.252 146 2.33 1.10

3.53 0.25 0.95 4.17 4.54 2.27 3.33 76.8 190 1.46 6.12 1.65 20.0 2.24 0.24 53.7 0.90 2.02 1.02 2.81 0.22 0.049 0.57 0.036 0.35 0.240 0.27

51.7 1.86 22.6 92.0 50.1 79.4 165.8 355.4 131.6

0.2 0.01 0.1 0.2 0.9 0.4 0.4 0.9 5.8

293.5 91.0 127

0.9 0.1 3

3117 59.8

18 0.8

0.31 0.054 9.11 0.16 0.065

m

Reference s

2.76 5.37

0.05 0.07

0.569

0.008

50.6

0.3

82 172 348 174 76 300 96 123 15 6.86 3128 61 81 17.5 74 17.6 4.36 18.4 2.83 17.3 3.48 9.7 1.37 8.9 1.35 38 11.1 1.62

1 2 6 4 1 4 1 3 2 0.02 47 1 1 0.4 2 0.3 0.04 0.3 0.05 0.2 0.07 0.2 0.02 0.2 0.02 1 0.2 0.05

m

s

11.41 5.93 0.590 3.02 5.74 4.43 2.32 0.61 0.48 0.2600

0.22 0.16 0.03 0.10 0.22 0.20 0.11 0.03 0.03 0.0360

51 1.9 23 101 59 81.0 167.0 357 137 73 298 98.0 140 14 6.8 3100 62 82 17.00 75 18 4.5 18 3.100 17 3.6 9.8 1.4 8.9 1.3 37 11 1.90

3 0.3 3 8 6 6 12 20 15 5 23 4 8.0 1 1.2 300 4.00 6 1 4 1 0.3 1 0.3 1 0.200 0.7 0.1 0.5 0.1 4 1 0.5

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

(Wt-%) Al2O3 Fe2O3T MnO MgO CaO Na2O K2O TiO2 P2O5 Stotal

ICP-MS

(continued on next page)

133

134

Table A.6 (continued) GSMS-3 (IRMA), mix marine sedim., Central Pacific Ocean

(lg/g) Li Be Sc V Cr Co Ni Cu Zn Rb Sr Y Zr Mo Cs Ba La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Pb Th U

s

7.43 3.66 0.379 1.84 21.7 3.64 1.53 0.348 0.309 0.236

0.1 0.06 0.006 0.03 0.5 0.06 0.02 0.005 0.005 0.004

35 1.18 13.8 60.3 29.6 50.6 101 229 125

1 0.01 0.2 0.9 0.5 0.8 2 3 2

640 60.6 69 3.6

9 0.9 4 0.3

2342 39.5

38 0.5

m

s

1.85 21.2

0.03 0.3

0.359

0.004

33.5

0.8

54.6 113.8 222 166.9 50.6 676 65 69 5.2 4.42 2413 42.6 53.5 11.8 49.8 11.6 2.86 12.0 1.84 11.3 2.29 6.32 0.887 5.63 0.864 20.1 6.68 0.99

0.4 0.6 2 0.8 0.4 5 1 10 0.3 0.05 19 0.7 0.5 0.2 0.8 0.1 0.05 0.2 0.02 0.2 0.04 0.08 0.003 0.05 0.007 0.5 0.05 0.02

JSl-1 (GSJ), slate, Permian

m

s

m

s

7.7 3.81 0.40 2.04 22.6 3.75 1.61 0.39 0.33 0.204

0.3 0.14 0.02 0.07 0.6 0.14 0.12 0.02 0.01 0.036

17,3 6.53 0.0603 2.31 1.42 2.18 2.79 0.71 0.190 0.1603

0,2 0.08 0.0008 0.04 0.02 0.04 0.04 0.01 0.002 0.0023

35 1.5 15 69 38 53 108 231 142 50 667 69 94 5.7 4.5 2500 44 55 12 51 12 3.0 12 2.0 11 2.4 6.3 0.96 5.8 0.89 22 7.0 1.1

2 0.2 2 6 5 4 9 10 22 5 68 6 8 0.8 0.7 200 4 4 1 2 1 0.2 1 0.2 1 0.2 0.2 0.09 0.4 0.07 5 0.6 0.3

52.1 2.15 15.5 131 51 14.2 37.4 40 102

0.7 0.04 0.2 2 1 0.3 0.2 1 2

184 24.8 140

3 0.4 4

293 27.3

5 0.5

m

JSL-2 (GSJ), slate, Permian s

2.19 1.40

0.02 0.02

0.694

0.006

52.0

0.5

14.9 37.4 41.5 117 111.5 181.8 25.7 138.1 0.75 8.00 285 28.2 59.2 7.0 27.1 5.50 1.24 5.0 0.77 4.82 0.98 2.87 0.420 2.81 0.424 18.3 9.5 2.48

0.2 0.5 0.2 2 0.6 1.6 0.2 0.8 0.01 0.09 2 0.4 0.7 0.1 0.5 0.02 0.04 0.1 0.01 0.09 0.01 0.06 0.005 0.01 0.007 0.3 0.2 0.04

m

s

m

s

17.69 6.81 0.060 2.39 1.51 2.21 2.87 0.726 0.194 0.1467

0.08 0.044 0.0012 0.021 0.013 0.025 0.021 0.0071 0.0025

17.6 6.28 0.0834 2.26 1.894 1.304 2.84 0.722 0.1642 0.0604

0.1 0.05 0.0005 0.01 0.008 0.006 0.01 0.003 0.0008 0.0003

51.75 2.14 16.49 135.18 60.00 15.77 37.12 39.95 108.54 113.59 189.48 28.92 169.44

1.94 0.12 1.18 5.74 3.77 1.11 2.26 2.90 5.47 4.14 6.28 1.47 5.15

52.0 2.499 15.72 121.0 54.6 15.5 42.1 41.0 92.7

0.4 0.005 0.08 0.9 0.7 0.1 0.2 0.4 0.2

221 25.10 155.2

1 0.08 0.5

8.05 307.20 28.24 58.57 6.68 27.26 5.61 1.24 5.04 0.80 4.83 1.00 2.84 0.44 2.90 0.44 18.59 9.91 2.59

0.34 12.00 0.81 2.45 0.40 1.57 0.30 0.10 0.30 0.04 0.20 0.07 0.18 0.04 0.16 0.02 1.11 0.58 0.15

290 30.4

2 0.2

m

s

2.14 1.83

0.02 0.02

0.700

0.007

51.6

0.4

15.7 41.6 42.3 105 111.4 217 25.6 151 1.3 8.71 280 31.6 68.0 7.8 29.6 5.90 1.177 5.1 0.81 4.93 1.02 2.92 0.43 2.88 0.440 20.69 11.1 2.48

0.1 0.5 0.3 1 0.6 1 0.1 1 0.1 0.02 1 0.2 0.5 0.1 0.4 0.03 0.005 0.1 0.01 0.08 0.02 0.04 0.02 0.06 0.008 0.08 0.2 0.05

m

s

18.17 6.65 0.0818 2.385 1.885 1.344 3.008 0.754 0.164 0.0579

0.319 0.238 0.00591 0.0614 0.0588 0.0600 0.136 0.0145 0.0210 0.0026

52.6 2.68 16.8 122 64.7 15.7 40.6 44.5 101 118 230 31.3 191 0.74 8.24 302 32.7 69.6 6.44 32.0 5.95 1.14 4.90 0.727 4.71 0.671 2.24

2.84 0.39 0.749 9.47 4.63 1.24 2.45 2.61 7.12 3.96 3.57 1.62 5.12

3.15 0.404 19.7 11.5 2.92

0.44 0.139 3.14 0.83 0.15

1.59 17.2 1.54 3.75 0.91 2.05 0.546 0.10 1.15 0.086 0.89 0.223 0.55

GSJ Geological Survey of Japan; IRMA Institute of Rock and Mineral Analysis, Chinese Academy of Geological Sciences, Beijing; m = mean results for 3 independent digestions, s = standard deviation, Reference values: JLk-1, JSd-2, JSl-2 (Imai et al., 1996); JSl-1 (Kane, 2004); GSMS-2, GSMS-3 (Wang et al., 1998).

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

(wt-%) Al2O3 Fe2O3T MnO MgO CaO Na2O K2O TiO2 P2O5 Stotal

m

G. Schettler et al. / Journal of Asian Earth Sciences 35 (2009) 103–136

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