Multi-stage hydrothermal processes at the Laozuoshan gold deposit in NE China: Insights from textures and compositions of sulfide assemblages

Journal Pre-proofs Multi-stage hydrothermal processes at the Laozuoshan gold deposit in NE China: Insights from textures and compositions of sulfide assemblages Lin Meng, Fei Huang, Wenyuan Gao, Daoheng Wang, Jianxi Zhu, Changming Xing, Wei Tan, Xu Tang PII: DOI: Reference:

S0169-1368(19)30272-0 https://doi.org/10.1016/j.oregeorev.2019.103275 OREGEO 103275

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Ore Geology Reviews

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20 May 2019 2 December 2019 5 December 2019

Please cite this article as: L. Meng, F. Huang, W. Gao, D. Wang, J. Zhu, C. Xing, W. Tan, X. Tang, Multi-stage hydrothermal processes at the Laozuoshan gold deposit in NE China: Insights from textures and compositions of sulfide assemblages, Ore Geology Reviews (2019), doi: https://doi.org/10.1016/j.oregeorev.2019.103275

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Multi-stage hydrothermal processes at the Laozuoshan gold deposit in NE China: Insights from textures and compositions of sulfide assemblages Lin Meng1, 2, Fei Huang1, 2, *, Wenyuan Gao1, 2, Daoheng Wang1, Jianxi Zhu2, Changming Xing2, Wei Tan2, Xu Tang3 1

Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, and School of Resources and Civil Engineering, Northeastern University, Shenyang, 110819, China 2

Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, 510640, China 3

Electron Microscopy Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China

Abstract The Laozuoshan gold deposit is a large gold deposit which experienced Variscan skarn mineralization and Yanshanian hydrothermal mineralization in Jiamusi massif, Northeast China. The Jiamusi massif hosts numerous gold deposits that have the commonly considered as products of the metamorphic hydrothermal process during the twice oceanic subductions. We conduct detailed texture observations, determine the sulfides phases by the laser Raman spectrum, and obtain in situ composition data with electron probe micro analyzer to further understand the formation and metasomatism of multi-stage sulfides in the Laozuoshan gold deposit. The paragenetic relationship between pyrite and marcasite under nanoscale was also clarified by the combination of both focused ion beam scanning electron microscopy and transmission electron microscopy. According to the

observed texture relationships among ore and gangue minerals, we divide the Variscan skarn mineralization period into three stages (Stage I to Stage III), and the Yanshanian hydrothermal mineralization period into four stages (Stage IV to Stage VII). The sulfides are mainly pyrrhotite in Stage I, with minor chalcopyrite, arsenopyrite, and pyrite. The native golds rich in silver (averaging 15.44 wt.%) are distributed in arsenopyrite which is rich in cobalt (averaging 2.69 wt.%). The pyrite is the main sulfide in Stage II, with minor chalcedony and calcite. The compositions of sulfides in both Stage I and Stage II indicate that the fluid was the sulfide-poor and weakly cobalt-rich system. The mineral stability relationships in both Stage I and Stage II confirm that the increase of sulfur fugacity and oxygen fugacity and the decrease of temperature. The sulfides are mainly arsenopyrite in Stage III, with minor native golds and tellurbismuth. The native golds contain averaging 8.02 wt.% silver. Arsenopyrite geothermometers indicate they formed at 420 to 390°C in Stage III. The sulfur fugacity and oxygen fugacity of ore fluids were below the pyrite-pyrrhotite buffer during the Stage III, revealing a reduced fluids system. In the hydrothermal mineralization period, multiple magmatic activities caused multi-stage hydrothermal fluids activities. From Stage V to Stage VII, the pyrrhotite replaced by marcasite and pyrite through the dissolution-reprecipitation mechanism, indicating the increase in pH value and the oxygen fugacity of the fluids, and alteration from the weakly acidic and weakly reduced conditions to neutral and weakly oxidizing condition. The mineralogical and compositional evolution of the sulfides in the Laozuoshan gold deposit constrain the physicochemical conditions of multi-stage ore-forming fluids, which is of considerable significance to understand the metamorphic-hydrothermal superimposed gold deposit fluids evolution in the Jiamusi massif.

Keywords: Skarn gold deposit; hydrothermal; arsenopyrite; pyrrhotite; dissolution-reprecipitation

1. Introduction Skarn gold deposits generally experienced multiple superimposed hydrothermal processes, forming complex ore structures and mineral paragenesis corresponding to non-contemporaneous sub-hydrothermal fluids (Meinert, 2000; Rottier et al., 2016). Therefore, investigating the metasomatic process of sulfide minerals in skarn gold deposits may help us to more deeply understand the metallogenic process of gold (Gammons and Williams-Jones, 1997; Meinert, 2000). Pyrrhotite is a common metal sulfide formed in the early stages of skarn deposit formation and is usually replaced by pyrite or marcasite in the later stages, indicating increase of sulfur fugacity (fS2) and oxygen fugacity (fO2), and decrease of pH in the fluid evolution (Murowchick, 1992; Qian, et al., 2011; Rottier et al., 2016). These condition changes can induce gold precipitation in the fluid (Hayashi and Ohmoto, 1991; Kerrich, 1999; Loucks and Mavrogenes, 1999; Simon et al., 1999; Williams-Jones and Bowell, 2009; Zhu et al., 2011). The formation of skarn gold deposits in Northeast China was mainly affected by the Phanerozoic collisional orogeny. These deposits are generally distributed in the collisional orogenic belt, within the fault-controlled active magmatic belt and the active craton margin (Chen et al., 2007; Deng and Wang, 2016). Affected by the late Paleozoic regional metamorphism, the Variscan magmatism and the Yanshanian magmatism, a series of metamorphic hydrothermal deposits were formed in the Jiamusi massif including the Laozuoshan gold deposit, Jizhuagou gold deposit, Xinli gold deposit, and Dongfengshan iron-gold deposit. (Fig. 1b, He and Zhao, 2002; Li, 2012; Zhang et al., 2016; Nan, 2018). The Laozuoshan gold deposit which experienced a superimposed by late-stage fluids is a representative large skarn gold deposit in the Jiamusi massif (Chen et al., 2007; Deng and Wang, 2016; An et al., 2017). The different models have been proposed in the previous studies to explain the complex geological processes recorded in this deposit, such as the regenerative magmatic hydrothermal superimposed migmatized hydrothermal causing mineralization (Li, 1986; He, 2002), orogenic mineralization (Zhang, 2008), skarn mineralization (Li, 2012) and hydrothermal superimposed

skarn mineralization (An et al., 2017). However, the physicochemical conditions of the fluid evolution processes represented by sulfide are not well understood in this deposit, and the report of the formation and metasomatism for multi-stage sulfides is few. Here, we study the texture and composition of major sulfides and native golds by using different scales of in situ methods in ore samples from the Laozuoshan gold deposit. These results are used to illustrate the evolution of sulfides and the physicochemical conditions of the ore-forming fluids in the Laozuoshan gold deposit, which enhances our understanding of the fluid evolution processes in superimposed metamorphic hydrothermal gold deposit in the Jiamusi massif.

2. Regional and Deposit Geology

2.1 Regional Geology The Laozuoshan gold deposit is located in the north-central part of the Jiamusi massif (Fig. 1b), and belongs to the eastern part of the Central Asian Orogenic Belt (Fig. 1a). This was the site where the North China Craton, Siberia Plate and Pacific Plate collided (Zhao et al., 2014; Hao et al., 2018). The deposit experienced deformation associated with the cratonization of the Jiamusi massif in the early Paleozoic (517–460 Ma), the Central Asian Orogenic Belt activity in the late Paleozoic (252–267 Ma) and the formation and development of the paleo-Pacific tectonic domain (90–110 Ma), and the superimposition of these tectonic movements provided favorable conditions for gold mineralization at the Laozuoshan (Yang et al., 2007; Li, 2012; Xue, 2012; Li et al., 2014; Wu et al., 2018a). NW- and NE-trending fault structures are relatively developed in the mining area, in which the NW-trending faults show the characteristics of compressive torsion and are the main ore-controlling structures in the research area (Fig. 2; Li et al., 2014), and the NE-trending faults have features of a brittle-ductile shear zone.

2.2 Deposit Geology The exposed strata in the Laozuoshan gold deposit mainly consist of the Mashan group of the lower Proterozoic Liumao formation, the Mesozoic Jurassic Chengzihe formation, and Quaternary loose sediments. The Mashan group is the oldest metamorphic rock series in the Jiamusi massif (An et al., 2017). The Liumao formation is distributed in the eastern part of the mining area, and the sequence consists of, from old to young, biotite plagioclase granulite, biotite plagioclase gneiss, marble, and migmatite. The Jurassic Chengzihe formation, which composes of sandstone and carbonaceous shale, is distributed in the northwest of the mining area and unconformably intersected by the underlying the Variscan stage gneissic granite and invaded by diorite bodies of the Yanshanian stage (Fig. 2). The magmatic rocks in the deposit formed in two periods of time, the Variscan and the Yanshanian periods (Li et al., 2014; Wu et al., 2018a). The magmatic rocks of the Variscan period are mainly gneissic granite and gneissic monzonite, which are mostly distributed in the West and Central ore belts in the mining area. The magmatic rock stocks in the East ore belt contact with marble, and form skarn ore bodies (Fig. 2 and Fig. 3a). The magmatic rocks of the Yanshanian period mainly include dioritic porphyrite, granite porphyry, granodiorite and diorite, which are distributed in the Central and West ore belts (Fig. 2). The mineralization-related Variscan granites have the characteristics of volcanic arc granites (Li et al., 2014). All the samples of the Variscan gneissic granodiorite and Yanshanian granodiorite and dioritic porphyrite showed enrichment of light rare earth element (LREE) and large ion lithophilic element, and relative depletion of heavy rare earth elements (HREE) and high field intensity elements such as Nb, Ta and Ti, showing similar properties to island arc or active continental margin magmas (Li et al., 2014). The magmatic hydrothermal activities of the Variscan and Yanshanian periods are intimately related to gold mineralization (Li, 1986; Dai et al., 2003; Xue, 2012; Li et al., 2014). Fluid inclusion homogenization temperature reveals two temperature intervals of 287–472°C and 156–412°C (An et al.,

2017; Wu et al., 2018b). The first fluid was a saline system containing CO2. With changing temperature, pressure and pH, a boiling process characterized by the escape of CO2, H2S and other gases occurred (An et al., 2017). At the later stage of mineralization, meteoric water may have been mixed in, and the fluid may have evolved into an H2O-NaCl system hydrothermal fluid (Li, 2012; An et al., 2017). The Laozuoshan gold deposit includes around 200 ore bodies (veins) and belongs to three belts: the East, Central and West ore belts. The NW- and NWW-trending faults control the placement of ore bodies in the East ore belt, which occurs in the contact zone between migmatitic granite and skarn (Fig. 3a). The ore bodies are large, vein-shaped, lamellar, or lenticular and around 25–300 m long, with a dip angle of 60–80° (Fig. 3b). The ores are mainly disseminated ores with an anhedral granular texture. The metal mineral content accounts for 10–30% (Figs. 4a, d–f). A small amount of massive sulfide ores also occurs (Figs. 4g–i). The Central ore belt is controlled by the NW-trending faults and occurs in migmatitic granite and skarn, with a small amount of contact with dioritic porphyrite. The ore bodies in this belt are large, mainly vein-like with a few lenticular shapes and are distributed nearly vertically. The ores have a euhedral to subhedral texture with a densely disseminated structure (Figs. 4b, c) or massive structure. The NE-trending faults controlled the West ore belt, which experienced hydrothermal mineralization. The ore bodies in this belt are small and lenticular and occur in granite and dioritic porphyrite. The ores are mainly disseminated and contain 5–30% sulfides. The ores at the Laozuoshan gold deposit can be divided into two types: oxidized ores and primary ores. The oxidized ores are brown in color and honeycomb in structure. They are mainly distributed in the upper 15–20 m below the surface. The primary ores can be divided into two sub-types: (1) the altered rock sub-type that is composed of skarn minerals and auriferous sulfides, representing 80% of the total ores, where sulfidation and gold mineralization is closely associated with intensive skarnization (Figs. 4a–f); (2) the hydrothermal veins sub-type that is mainly composed of quartz, and auriferous sulfides, which developed near the NW-trending fault structure (Figs. 4g–i). Ore minerals are pyrrhotite, arsenopyrite, pyrite, chalcopyrite,

marcasite, followed by minor sphalerite, bornite, galena, tellurbismuth, electrum, and native gold. Gangue minerals include garnet, diopside, chlorite, epidote, quartz and calcite.

3. Methods The samples were examined by transmitted and reflected light microscopy to characterize the morphology, textures and paragenesis. Following this, samples were investigated using an Ultra Plus field emission scanning electron microscope (FESEM) equipped with a backscattered electron (BSE) detector and an energy dispersive spectrometer (EDS) in the Analysis and Testing Center, Northeastern University (NEU). Chemical analyses of the sulfides and golds in ore samples were performed on a JEOL JXA-8320 electron probe microanalyzer (EPMA) in the Key Laboratory of Mineralogy and Metallogeny, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (GIGCAS). Both the standards and samples were tested using wavelength dispersive spectrometry with a beam diameter of 1 μm, accelerating voltage of 20 kV and a beam current of 20 nA. Peak and background counting times were 20 s and 10 s for Fe and S, 40 s and 20 s for Co, As, Ni, Cu and Zn, and 60 s and 30 s for Au, Ag, Cd and Se. Standard specimens used for calibration were FeS2 (Fe, S), FeAsS (As), Co (Co), Ni (Ni), Cu (Cu), ZnS (Zn), Cd (Cd), BiSe (Se), metal silver (Ag) and metal gold (Au). Analytical results were using the ZAF correction routines. Chemical analyses of the chlorite in ore samples were performed on a JEOL JXA-8530F electron probe microanalyzer (EPMA) in the same laboratory in NEU. Both the standards and samples were tested using wavelength dispersive spectrometry with a beam diameter of 1 μm, accelerating voltage of 15 kV and a beam current of 10 nA. Peak and background counting times were 10 s on high background and 10 s on low background position and 10 s on high background position for each element. Standard specimens used for calibration were quartz (Si), rutile (Ti), spessartine (Al, Ca, Mn, Mg), magnetite (Fe), albite (Na), anorthoclase (K). Analytical results were using the ZAF correction routines.

The aggregates of pyrite and marcasite were analyzed using a HORIBA XploRA Plus Laser Raman micro-spectrometer in the same laboratory in GIGCAS. An Ar ion laser operating at 5 mW was used to produce the excitation wavelength of 532 nm. The scanning range of spectra was set between 100 and 3200 cm–1 with an accumulation time of 8 s for each scan. Focused ion beam scanning electron microscopy (FIB-SEM) enabled the preparation of thin foils for the study using transmission electron microscopy (TEM) (Ciobanu et al., 2011). We prepared a TEM foil of 13 × 5.2 μm in area, following the methods of Li et al., (2017), on a Zeiss Auriga Compact instrument at the Electron Microscopy Laboratory, Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS). The TEM section is ~100 nm in thickness. Composition and crystal structure analyses of micro-pyrite and marcasite were carried out using the JEOL JEM-2100 TEM instrument in the same laboratory in IGGCAS. This TEM instrument was operated at 200 kV with an electron beam generated from a LaB6 gun for conventional bright field TEM observations, selected area electron diffraction (SAED) and high-resolution observation (HRTEM). Elemental analysis was conducted in EDS mode, which was controlled using Oxford Aztec software.

4. Results Based on field observations, as well as petrographic and ore texture relationships, the alteration-mineralization process can be divided into the skarn mineralization period and the superimposed hydrothermal period (He, 2002). The skarn mineralization period can be further divided into three stages: (1) the pyrrhotite-arsenopyrite-calcite stage (Stage-I); (2) the colloidal pyrite-quartz stage (Stage-II); and (3) the coarse-grained arsenopyrite-calcite stages (Stage-III) (Fig. 5). The subsequent hydrothermal mineralization period can be further divided into four stages: (1) the massive quartz stage (Stage-IV); (2) the coarse-grained arsenopyrite-quartz stage (Stage-V); (3) the polymetallic sulfide-arsenopyrite-quartz stage (Stage-VI); and (4) the

quartz-calcite stage (Stage-VII) (Fig. 5).

4.1 Textural features of sulfides from and hydrothermal stages

4.1.1 Skarn mineralization period Pyrrhotite (Po-1) is usually 300 μm to several centimeters in size and coarse-grained subhedral to anhedral which is the main sulfide in Stage I. Po-1 coexisted with other sulfides, such as arsenopyrite (Apy-1), pyrite (Py-1) and chalcopyrite (Cpy-1) (Figs. 6a–d). Chalcopyrite or carbonate veins generally fill micron-scale fractures in Po-1. The fine to medium grains of Apy-1 are subhedral to anhedral and distribute in the margin of pyrrhotite (Po-1) (Figs. 6b, c). Both Po-1 and Apy-1 are the main gold-bearing minerals in Stage I that is the main metallogenic stage of gold. Native gold (Au-1) is mainly distributed in the intergranular spaces of Po-1, Apy-1 and gangue minerals, as well as it contains fissure gold and inclusion gold (Figs. 6b, c). The middle grained Py-1 are subhedral to anhedral distributed in the margin or fractures of Po-1 (Figs. 6a, c, d). All the sulfides are disseminated in gangue minerals such as garnet, diopside, calcite and biotite (Figs. 6e, f). Pyrite (Py-2) is the main sulfide in Stage II, which is rarely developed in the Central and East ore belts. Py-2 is colloidal and composes of nano-micron sized FeS2 grains (Fig. 6g). Py-2 has discussed a lot in Meng et al. (2017). The chalcedony grain or calcite veins occur in the core or the margin of Py-2 (Fig. 6g and Fig. 4 in Meng et al., 2017). The Stage III mainly occurs in the Central and East ore belt, which distribute relatively weaker than the Stage I. The sulfides are relatively simple, dominated by arsenopyrite (Apy-2) with intensively chloritization (Figs. 6g–i). Apy-2 are subhedral to anhedral crystals ranging from 0.1 to several millimeters, with developed cracks (Fig. 6g). The native golds often with tellurbismuth distribute in the arsenopyrite (Apy-2) fissure, or the

intergranular space among arsenopyrite (Apy-2), pyrrhotite (Po-1) and gangue minerals (Fig. 6g). Native golds and tellurbismuth also appear as inclusions in Po-1 and Apy-2. Chlorite develops at the margin of Apy-2 (Fig. 6i). Calcite veinlets or grains fill the gaps between arsenopyrite (Apy-2) and chlorite (Fig. 6i).

4.1.2 Hydrothermal mineralization period The Stage IV and Stage V are mainly developed in the West ore belt, and occasionally in the Central and East ore belt. Quartz with milky white or greyish white is blocky in Stage IV. It is anhedral coarse-grained, veined and cataclastic (Fig. 7a). It almost contains no sulfides. Arsenopyrite (Apy-3) is subhedral to anhedral with 2–3 mm in Stage V (Fig. 7b), which includes minor native gold. The associated mineral is quartz, followed by minor of chalcopyrite, pyrite and calcite. The Stage VI is widely distributed in the West ore belt and constitutes the main ore body in hydrothermal mineralization period, while occasionally in the East and Central ore belt. There are a variety of sulfides, including chalcopyrite (Cpy-2), pyrite (Py-3), pyrrhotite (Po-2), arsenopyrite (Apy-4) and minor sphalerite and galena (Figs. 7c–h). Coarse-grained chalcopyrite is subhedral to anhedral and is the main sulfide in Stage VI (Figs. 7c–e). Medium to fine-grained pyrite (Py-3) is usually euhedral to subhedral (Figs. 7e–f). Medium-grained marcasite coexisted with Py-3 is subhedral to anhedral and distributes at the margin of Py-3 (Fig. 7f). The medium to fine-grained pyrrhotite (Po-2) occurred with chalcopyrite and sphalerite is subhedral to anhedral (Figs. 7c–e). Middle grained arsenopyrite (Apy-4) is euhedral to subhedral (Fig. 7g). Sphalerite and galena mainly distribute in the West ore belt, with only a few scattered in the East and Central ore belts. Anhedral or stellate sphalerite is associated with chalcopyrite (Fig. 7c). Galena is usually subhedral to anhedral in the margin or fractures of arsenopyrite (Apy-4) (Fig. 7g).

The Stage VII distributes widely in the Central and East ore belt, occasionally in the West ore belts. Pyrite (Py-4) and marcasite are the primary sulfides. Medium-grained Py-4 is subhedral to anhedral, while fined grained Py-4 is euhedral to subhedral (Figs. 7i–l). Marcasite and the fine-grained euhedral to subhedral pyrite usually appear in the alternative bands (Fig. 7f). The interstitial bands are filled with carbonate veins (Fig. 7q). The aggregates of nano- to micron-sized pyrite and marcasite grains (<5 μm) are porous (Fig. 7l). . The metasomatic pyrrhotite (Po-1) formed in Stage I has oriented fractures was wrapped by the porous pyrite and marcasite aggregates (Fig. 7k). The directions of fractures are inconsistent in different pyrrhotite particles (Fig. 7i). Metasomatic residua and iron oxide occur at the margin of the pyrrhotite (Figs. 7i, k). In the hydrothermal fluid metasomatic region at the margin of pyrrhotite, the Fe and S contents of pyrrhotite (Po-1) show a negative correlation from the inside to the outside (Figs. 7m–n). The pyrite (Py-4) and marcasite aggregates can be divided into three zones, the external fine porous pyrite + marcasite paragenetic zone (the external zone), the euhedral to subhedral pyrite (the middle zone), and the internal fine porous pyrite + marcasite paragenetic zone (the internal zone) (Fig. 8a). The grain boundaries of pyrite and marcasite cannot be distinguished in the external zone (Fig. 8b). The size of euhedral to subhedral pyrite ranges from 5–20 μm in the middle zone (Figs. 8c–e). The crystals plane of pyrite is well-developed, and the crystal boundary is visible. The nano- to micron-scale pyrite + marcasite grains are subhedral to anhedral, approximately 1–4 μm, and tightly packed in the internal zone. The quantities of pores decrease while the sizes of pores increase. The pores with size range 1–3 μm are pervasive in the external zone, with size range 3–6 μm in the middle zone (Figs. 8d–e), and with size range 1–2 μm in the internal zone (Figs. 8e–f). A few myrmekitic sphalerite distributed in the external zone (Fig. 8b).

The contact boundary between pyrite and marcasite was selected for nanoscale investigation. FIB-SEM was used to obtain thin slices for TEM studies (Figs. 9a–c). The contact boundary is divided into three phase zones in the bright field TEM image (Fig. 9d). HRTEM image shows a transition zone between pyrite and marcasite (Fig. 9e). The pyrite surface spacing is d(220) =1.95 Å, and the marcasite surface spacing is d(101) = 2.68 Å (Fig. 9f). SAED patterns of the [135] and [131] zonal axes of marcasite and [212] zonal axes of pyrite were obtained (Figs. 9g–i), confirming that pyrite and marcasite are recrystallized and their crystalline orientations are independent.

4.2 EPMA data of sulfides and gold Arsenopyrite contains variable Fe, S and As contents between different generations (Fig. 10 and Table. 1). The arsenic concentration of Apy-1 and Apy-3 (46.67 to 49.02 wt.%, 47.63 to 50.71 wt.%, respectively) is more than the standard molecular formula (46.01 wt.%). On the contrary, the S (18.06 to 18.97 wt.%, 16.57 to 17.64 wt.%, respectively) and Fe (30.09 to 33.98 wt.%, 32.90 to 34.57 wt.%, respectively) are less than the standard molecular formula (S: 19.69 wt.%; Fe: 34.30 wt.%). Among them, Apy-1 and Apy-3 are generally deficient in Fe and S and enriched in As and Co compared to the Apy-2 and Apy-4. The Apy-1and Apy-3 show a negative correlation between Co and Fe content, indicating that cobalt was probably incorporated into arsenopyrite by substitution of iron (Fig. 10 and Table. 1). The two generations of native gold have distinct characteristics in the composition (Table. 2 and Fig. 11). The gold content of Au-2 varies from 89.87 to 90.45 wt.% (with an average of 90.23 wt.%), which is significantly greater than that of Au-1 (77.76 to 86.93 wt.%, with an average of 83.25 wt.%) (Fig. 11). The Au-1 is generally variable in Ag (14.57 to 17.45 wt.%, averaging 15.44 wt.%) and enriched in Fe (0.1 to 2.50 wt.%, averaging 0.68 wt.%) compared to the Au-2. According to the calculation formula for Au fineness (Au fineness = Au/(Au + Ag) × 1000) (Fisher, 1945; Zhang and Chen, 1995), the average fineness of Au-1 and Au-2 are 843.567 (828.265–856.706, n=6), 918.403 (909.411–924.588, n=3), respectively. The

primary ore of the Laozuoshan gold deposit has a medium Au fineness and a medium forming temperature (Zhang and Chen, 1995). The compositions of pyrrhotite are variable in different generations (Table. 3). The Fe and S contents of Po-1 and Po-2 overlap with each other. The Fe and S contents in Po-1 are in the range 60.10 to 61.59 wt.% (with an average of 60.76 wt.%), 38.50 to 39.85 wt.% (with an average of 39.36 wt.%), respectively. While in Po-2, the Fe and S values fall into the range of 59.98 to 61.49 wt.% (with an average of 60.84 wt.%), and 37.97 to 40.11 wt.% (with an average of 39.18 wt.%). The compositional characteristic of pyrrhotite (Po-1) is close to Fe7S8 in this period (Fig. 12a). However, the pyrrhotite (Po-2) compositions range from Fe7S8 to Fe10S11. Besides Fe and S, all the pyrrhotite samples analyzed contain considerable amounts of trace elements such as Cu, Co, Ni, arsenic and Au. These elements change slightly among different generations. For instance, the Po-1 with the anomalous concentration of Cu (up to 0.07 wt.%) reflects the contamination by the Cpy-1 replacement (Table. 3). The Co content in Po-1 varies between 0.06 wt.% and 0.09 wt.%, with an average of 0.07 wt.%, while Co in Po-2 changes from 0.05 wt.% to 0.08 wt.%, with an average of 0.07 wt.% (Fig. 12b). The Po-2 is generally enriched in Ni (<0.01 wt.% to 0.18 wt.%, with an average of 0.06 wt.%) compared to the Po-1. The EPMA data for the different generations of pyrite are listed in Table 4. Concentrations of Fe and S contents in the four generations of pyrite grains vary considerably (Fig. 12c). Compared with the standard molecular formula (Fe: 46.55 wt.%; S: 53.45 wt.%), the Py-1 has the slightly higher Fe and S contents, ranging from 46.73 to 47.48 wt.% (averaging 47.08 wt.%), and 51.39 to 54.20 wt.% (averaging 53.17 wt.%), respectively; the Py-2 has the weakly deficient Fe and S contents, ranging from 45.48 to 46.88 wt.% (averaging 46.23 wt.%), and 51.68 to 53.28 wt.% (averaging 52.76 wt.%), respectively. Among them, the Py-3 is weakly poor in Fe (45.45 to 47.12 wt.%, with average of 46.21 wt.%) and enriched in S (52.78 to 54.50 wt.%, with average of 53.76 wt.%). The Fe and S contents in Py-4 show a similar variation with the Py-1. The Fe and S contents in Py-4 range from 45.60 to 47.39 wt.% (with average of 46.93 wt.%), and 52.24 to 54.34 wt.% (with an average of 53.47 wt.%), respectively. In Table 3, nearly all pyrite

samples contain a considerable amount of Co plus a wide range of other trace elements such as Cu, arsenic, Ni and Au. The Co content of Py-1 to Py-4 is in the range 0.05 to 0.09 wt.% (averaging 0.07 wt.%), 0.03 to 0.11 wt.% (averaging 0.06 wt.%), 0.04 to 0.07 wt.% (averaging 0.06 wt.%) and 0.04 to 0.07 wt.% (averaging 0.05 wt.%), respectively (Fig. 12d). The Cu content of Py-1 is usually less than 2.74 wt.%, which is significantly great than that of Py-2 and Py-4. This result suggests that Py-1 is overprinted by the copper-bearing hydrothermal fluids. The Py-2 and Py-3 coexisted with arsenopyrite display a greater As content (Py-2: <0.08 wt.%; Py-3: <0.22 wt.%), which indicates that arsenic was probably incorporated into pyrite by substitution of sulfur (Fig. 12d). The Py-1 and Py-4 barely contain arsenic. The Ni is preferentially concentrated in Py-1 (<0.17 wt.%) and Py-3 (<0.31 wt.%) rather than Py-2 (<0.01 wt.%) and Py-4 (<0.13 wt.%). Based on the EPMA data (Table. 5), the Fe content in marcasite is in the range of 43.27 wt.% to 47.17 wt.% (with average of 46.19 wt.%), which fluctuate around the theoretical value of marcasite (Fe: 46.55 wt.%) (Fig. 12e). While the S content in marcasite is in the range of 52.54 to 54.29 wt.% (with an average of 53.86 wt.%), which are higher than the theoretical value of marcasite (S: 53.45 wt.%) (Fig. 12f). The cobalt content in marcasite varies from 0.04 to 0.07 wt.%, with an average of 0.05 wt.% (Fig. 12f). The As and Ni in marcasite are fluctuant with the detection limit. There are no other discernible systematic changes for other trace elements. The As and Co contents in marcasite, Py-3 and Py-3 are similar.

5. Discussion

5.1 Textural and compositional evolution of sulfides in metallogenic evolution The evolution of the metallogenic system can be described depending on the texture, paragenetic, and mineral chemistry of sulfides and coexisting native golds in this study. The hydrothermal mineralization process of the Laozuoshan gold deposit is summarized into two periods, skarn

mineralization period (Stage I to Stage III) and hydrothermal mineralization period (Stage IV to Stage VII). The disseminated coarse-grained Po-1 which formed in the early Stage I was subsequently replaced by anhedral fine-grained Apy-1 and chalcopyrite coexisted with native gold (Au-1, Figs. 6b–c). The porous subhedral to anhedral Py-1 distributed in the cracks of Po-1 (Figs. 6c–d), formed later than Po-1. The EPMA data show that the sulfides which formed in Stage I, such as Po-1, Apy-1 and Py-1, are slight S deficiency and Fe enrichment (Fig. 10b and Figs. 12a, c). The Apy-1 contained high arsenic and cobalt (<4.19 wt.%, with average of 2.69 wt.%), the cobalt was negatively correlated with the Fe (R2=0.9743) in Apy-1 (Fig. 10a). The composition of the sulfides formed in Stage I indicated that the fluid is a sulfur-poor and relatively cobalt-rich system. All subhedral colloidal Py-2 was formed in the Po-1 margin, and part of Py-2 was metasomatic by late Apy-3 or calcite veins (Fig. 6g). In Stage II, the Py-2 was deficient in sulfur (average less than 0.69 wt.%) and contained relatively high arsenic (<0.11 wt.%), compared with other generations of pyrite (Fig. 12c; Table. 4). The results of texture and composition show that Py-2 was formed earlier than Apy-2. The mineral assemblages of Py-2, chalcedony and calcite in Stage II of the Laozuoshan gold deposit (Fig. 6g and Fig. 4 in Meng et al., 2017) suggest that Py-2 formed by rapid crystallization and aggregation in a weakly acid and weakly reducing at low temperature (Ohfuji and Rickard, 2005; Gao et al., 2017; Meng et al., 2017), which indicated that the end of the fluid activity. Arsenopyrite (Apy-2) coexisted with native gold (Au-2) in Stage III. The Au-2 and tellurbismuth are distributed in the grains or fracture of Apy-2 (Fig. 6g). Compared with Apy-1, the Apy-2 is relatively concentrated in Fe and S. The S contents in Apy-2 was 0.6 wt.% higher on average than Apy-1, while the Co and As contents in Apy-2 decreased significantly. According to Heinrich and Eadington (1986), the precipitation of Apy-2 mainly occurs between pyrrhotite and pyrite buffer (Fig. 13). The arsenic is precipitated in a weakly acidic and neutral fluid with H2S in the form of H3AsO30 to form

arsenopyrite (Heinrich and Eadington, 1986). With the Apy-2 precipitated, the fO2 of the fluid increases (Eq. 1). (1) Under the influence of hydrothermal fluids in the Yanshanian period, the typical hydrothermal vein type ore bodies dominated by polymetallic sulfides were formed in the Laozuoshan gold deposit (Stage IV to Stage VII). The medium grained euhedral arsenopyrite (Apy-3) was formed in Stage V, the Apy-3 has a serious deficit of S, and the content of As in Apy-3 is the highest in four generations of arsenopyrite. The Co content in Apy-3 concentrated in the range of 0.21 to 0.35 wt.%, except for some point (Co up to 1.74wt.%) (Table. 1; Fig. 10a), which represents the ore-forming fluid was relatively poor sulfur, with relatively higher fO2 and high temperature during Stage V. A large amount of coarse-grained chalcopyrite, euhedral to subhedral coarse-grained pyrite (Py-3), subhedral medium-grained arsenopyrite (Apy-4) and pyrrhotite (Po-2) were formed in Stage VI, with minor anhedral sphalerite, subhedral galena and marcasite (Figs. 7c–g). These paragenesis features of the sulfides indicate the ore-forming fluid was reduced near the pyrite-pyrrhotite buffer during Stage VI. The Po-2 and Apy-4 decreased obviously compared the Po-1 and Apy-2 (Figs. 7c, e, g). The Po-2 and Po-1 were replaced by coarse-grained chalcopyrite (Figs. 7c–d). The S content in Apy-4, Po-2, Py-3 and marcasite increase, compared to previous generations of sulfides (Fig. 10 and Fig. 12), indicate that the ore-forming fluid was relatively enriched sulfur and reduced near the pyrite-pyrrhotite buffer. The phase transition of pyrrhotite (Po-1), pyrite (Py-4) and marcasite occurred in Stage VII (Figs. 7i–l). Py-4 and marcasite with porous morphology surrounded Po-1 (Fig. 7k). The transition among the pyrrhotite, pyrite and marcasite were closely related to the solution’s Fe 2+/S2-, pH value and redox conditions (Schoonen and Barns, 1991a, b, c). In weakly acidic fluid with rich H2S, pyrite replaced the pyrrhotite through a dissolution-reprecipitation mechanism (Rottier et al., 2016). When the pH value below 5, pyrrhotite transformed into the intermediate marcasite with random or preferred crystal

orientation, indicating a low concentration of S2- in the ore-forming fluid (Murowchich, 1992; Qian et al., 2011). When the pyrrhotite was metasomatized by magmatic fluids, the pyrrhotite rapidly dissolved in the acidic and unsaturated fluids. The fluids which surrounded the dissolved pyrrhotite contain relatively higher concentrations of iron ions and sulfur ions (Eq. 2; Fig. 14a; Qian et al., 2011; Putnis, 2002). Generally, marcasite crystallized in the lower supersaturation of fluid, compared to pyrite needs the higher degree supersaturation to crystallize and precipitate (Harmandas et al., 1998; Richard and Luther, 2007; Qian et al., 2011; Kitchaev and Ceder, 2016). Consequently, the concentration of iron ions and sulfur ions in the fluids was low at first and gradually increased with the dissolution of pyrrhotite. A large number of marcasite nanocrystals precipitated when the concentration of iron and sulfur in the fluids firstly reached the supersaturation for marcasite (Eq. 3; Fig. 14b). Due to the nucleation rate controls the growth of marcasite, marcasite is fine grain (<2 μm) with the high porosity (Murowchick, 1992; Qian et al., 2011). (2) (Fe-loss pathway) (3) ( (oxic and acidic conditions)

pathway)

(4)

(5)

With the further dissolution of pyrrhotite and the crystallization of marcasite, the potential energy of crystal crystallization decreased significantly. When the concentrations of iron ions and sulfur ions in fluids reached the supersaturation of pyrite, the pyrite precipitated dominantly (Eq. 4 and 5; Fig. 14c). The nucleation rate of pyrite is very slow due to it is limited by the degree of supersaturation of fluids (Murowchick, 1992; Rickard and Luther, 2007). Thus, pyrite with few pores is relatively subhedral. Due to the nucleation primary occurs at the margin of marcasite (Fig, 7i-k), there formed several micron-range gaps between pyrrhotite and marcasite + pyrite (Murowchick, 1992).

The fine grain marcasite transformed into fine grain euhedral pyrite when the pH value increase (4-6) or temperature fluctuations in the fluids (Schoonen and Barns, 1991a; Rottier et al., 2016). With the pyrite growth, the pH increased in the fluids, lead to the transformation of marcasite to pyrite (Figs. 7l, p and Fig. 8). The euhedral to anhedral pyrite and anhedral marcasite polycrystalline are randomly oriented crystals from the pyrrhotite (Figs. 9f–i), the same results were recorded by Murowchick (1992). When fO2 increases in fluids, the oxygen in the fluids increased and could react with the Fe2+aq released by dissolved pyrrhotite to form iron oxides (Fig. 7i and Fig. 14d; Qian et al., 2011). Both pyrite and marcasite formed by the dissolution and reprecipitation of pyrite have significant decrease in volume, while pyrite formed by replaced marcasite has slight volume decrease (Murowchick, 1992; Qian et al., 2011). The euhedral pyrite has the relatively large pores with the pseudomorphs of pyrrhotite compared the porous fine-grained pyrite + marcasite have the numerous small pores along grain-twin boundaries or clouds of small pores with grains (Figs. 7i–l). The porous texture (Figs. 7i–l and Fig. 9), which is the channel for further material exchange between crystalline grains and hydrothermal fluids, can be observed in the specimen and under the microscope (Fig. 4i and Fig. 8; Putnis, 2002).

5.2 Physical-chemical conditions of multi-stage fluids inferred by sulfides assemblages The coarse-grained pyrrhotite coexisting with minor arsenopyrite (Apy-1) and chalcopyrite indicates that ore-forming fluids remained to moderately low fS2 and fO2 in Stage I (Figs. 6b–d; Sui et al., 2017). The assemblage of arsenopyrite and pyrite suggests that the fS2 and fO2 of ore-forming fluids significantly increased above the pyrite-pyrrhotite buffer in the late stage of mineralization (Figs. 6c–d and Fig. 13; Sui et al., 2017). The homogenization temperature of the ore-forming fluid ranges from 287 to 472°C (An et al., 2017; Wu et al., 2018b). The colloidal pyrite + calcite + chalcedony assemblages, which formed in the low temperature indicated the end of the fluid activity (Meng et al., 2017). The compositions of all sulfides in Stage I and Stage II indicate that the fluid is a sulfide-poor and weakly cobalt enriched system (Fig. 10a and Fig. 12). Overall, the fS2 and

fO2 of the ore-bearing fluids were increased with the pyrrhotite, arsenopyrite, chalcopyrite and pyrite were formed successively. Two main arsenic minerals in worldwide gold skarns are arsenopyrite and lollingite, with arsenopyrite more common than lollingite in the reduced gold skarn subtype (Meinert, 1998; Fuertes-Fuente et al., 2000). Formation of these paragenesis indicates relatively high temperature, low fS2 and low fO2 during the metasomatic process (Meinert, 2000). Arsenopyrite is the only arsenic minerals in the Laozuoshan gold deposit (Fig. 6). The temperature and fS2 can be estimated using the arsenopyrite geothermometer proposed by Kretschmar and Scott (1976) and subsequently modified by Sharp et al., (1985). The atomic contents of As (32.92 to 33.47 at.%) in arsenopyrite (Apy-2) associated with chlorite and from arsenopyrite yield calculated temperatures between 390 and 420℃, with fS2 values ranging from –10.9 to –8.8 log units (Fig. 15; Table 1). This view is confirmed by the composition of coexisting chlorite. Chlorite formed under the reducing and oxidizing condition is typically Fe- and Mg-rich, respectively (Inoue, 1995; Sui et al., 2017). Chlorite coexisting with arsenopyrite at the Laozuoshan contains 29.26–29.83 wt.% FeO, 12.42–12.70 wt.% MgO, and 24.00–24.85 wt.% SiO2, with Fe/(Fe+Mg) ratio of 0.565 to 0.580 (Table 6). The analyses fall at the left edge of the ripidolite field in the classification diagram of chlorite (Fig. 16; Foster, 1962; Wang and Zhu, 2015; Sui et al., 2017), confirming a reduced condition for its formation. In summary, the gold is the unique economic concentrations in the skarn mineralization period of the Laozuoshan gold deposit. The Bismuth and telluride minerals coexisted with arsenopyrite - pyrrhotite are common in the hydrosilica alteration or retrograde and are associated with gold, which is a typical Au-Bi-Te-As geochemical association (Ciobanu et al., 2005). Arsenopyrite is the unique arsenic-bearing minerals in skarn. Arsenopyrite typically coexisted with pyrrhotite and formed relatively late in the paragenesis at relatively low temperature compared to early anhydrous skarn stage. The above features are identical to those of typically reduced gold skarn described by Meinert (2000; 2005). We conclude that the Laozuoshan gold deposit might belongs to the reduced gold skarn subtype.

In hydrothermal mineralization period, there are multi-stage hydrothermal fluids activities due to multiple stages of magmatic activity (Li et al., 2014; An et al., 2017). According to the features of sulfides, the early ore-forming fluid was relatively sulfur-poor, with relatively above the pyrrhotite-pyrite buffer and high temperature during Stage V. The sulfides paragenesis suggests that the ore-forming fluid were relatively enriched in sulfur with reduced condition near the pyrite-pyrrhotite buffer. During the replacement of pyrrhotite by marcasite, the fluids probably became more acidic (pH <2.5) and relatively reduced; and during the pyrrhotite replaced by the pyrite, the fluids probably were moderately acidic (pH >2.5) and relatively reduced to moderately oxidized. Replacement of marcasite by pyrite suggests a pH increase of the fluids. The iron-oxide often occur between the pyrrhotite and the pyrite (Fig. 7i). Their presence indicates that the more oxidized conditions toward the end, after the reduced conditions during the early stage of formation of the marcasite and pyrite.

5.3 Metallogenesis of different hydrothermal fluids In the Hercynian, the Laozuoshan gold deposit was affected by the end of the subduction period of the ancient Asian ocean and the Jiamusi massif (Wu et al., 2018). The high-temperature magma with enriched in volatiles was formed from the enriched mantle, which ascends along the NW-trending and NWW-trend faults (An et al., 2017). The hydrothermal fluid leached and extracted from the surrounding rocks and formed the ore-bearing fluids with enriched Fe and Au and deficient in S when the silica-rich magmatic-hydrothermal fluid and the surrounding rocks take the intensively water-rock reaction. With the pyrrhotite, arsenopyrite, minor pyrite, chalcopyrite and other sulfides precipitated from the weakly reduced and acidic ore-bearing fluid (Stage I, Stage III), the fS2, fO2 and pH value of fluid increased, lead to the gold-complex decomposed and precipitated in the hydrothermal fluid. The ore bodies were surrounded by the skarn and contact zone. The Laozuoshan deposit was affected by the intensively tectonic-magmatic activity by subduction of the littoral-Pacific plate in the middle and late

Yanshanian (Li et al., 2014). The hydrothermal fluids leached and extracted economic components from the surrounding rock when multi-stage middle-acidic magma invasion and migration (Li et al., 2014; An et al., 2017). The ore-forming fluids superimposed the skarn type ore body which formed in the Hercynian, eventually make gold-bearing hydrothermal along with the NW-trending and NE-trending faults penetration (An et al., 2017). With chalcopyrite, pyrite, arsenopyrite, pyrrhotite and other sulfides precipitated, the Cu-Au ore bodies were formed (Stage V to Stage VII). With the mix of meteoric water, the quartz and calcite precipitated from the medium to low temperature and low-salinity hydrothermal fluid, and the mineralization ends. The Jiamusi massif is one of the important gold deposit concentrated production areas in northeast China (Table. 7; Xue, 2012; Wang, 2014). The ancient basement is composed of upper Archean Mashan group, lower Proterozoic Xingdong group, Dongfengshan group, Heilongjiang group and Proterozoic migmatitic granite (Tan, 2009). During the Xingdong movement, the Jiamusi massif was folded and accompanied by intense magmatic activity, and ductile shear zones were formed locally. A large number of hydrothermal fluids generated by frequent magmatic activity captured some gold in the surrounding rocks during its continuous migration and usually formed an ancient basement with high gold abundance anomaly (Cheng, 2004). During the subduction of the Paleo-Asian Ocean and the Jiamusi massif in the late Variscan period, with the intrusion of migmatitic granite, the Laozuoshan skarn deposit, the Dongfengshan gold and Xinli gold deposit were formed in the Jiamusi massif (Li et al., 2014; Zhang et al., 2016; Nan, 2018). In the middle and late Yanshanian period, due to the subduction of the littoral Pacific plate, a new round of intense tectonic-magmatic activity began (Li et al., 2014). The hydrothermal superimposed ore body in the Laozuoshan gold deposit and Jizhuagou gold deposit were formed by the multi-stage intruded of intermediate-acid magma (He and Zhao, 2002; Li et al., 2014). The study of the sulfides textural and compositional evolution in

the Laozuoshan gold deposit indicate the physicochemical conditions of multi-stage ore-forming fluids, which is of considerable significance to understand the metamorphic hydrothermal superimposed gold deposit fluids evolution in Jiamusi massif.

6. Conclusions The Laozuoshan gold experienced the skarn mineralization, which belongs to the reduced gold skarn deposit. This deposit also experienced the superimposition of multiple stages of fluids activity in the Yanshanian. By studying the texture and compositional characteristics of major sulfides and native golds in ore samples, this paper provides important information on sulfides and fluids evolution, which reflects the changes of fS2, fO2 and pH in the hydrothermal fluids. (1) In the Variscan skarn mineralization period, from the Stage I to Stage II, the fS2 and fO2 of the ore-bearing fluids were increased with successively forming of pyrrhotite, chalcopyrite, arsenopyrite and pyrite. The ore-bearing fluid is a sulfur-poor and relatively cobalt-rich system. The colloidal pyrite indicates the end of the fluid activity. In Stage III, the arsenopyrite geothermometer gets the temperature range from 390 to 420°C. The mineral stability relationships and chemical composition of arsenopyrite indicate the fluids under relatively high temperature, low fS2 and low fO2 during the Stage III. (2) In the Yanshanian hydrothermal mineralization period, there are multi-stage hydrothermal fluids activities due to multiple magmatic activities. The sulfides paragenesis indicates that the fS2 and fO2 of the ore-forming fluids increased from Stage V to Stage VII. The pyrrhotite replaced by the marcasite and pyrite through the dissolution-reprecipitation mechanism, which indicates the pH value and the fO2 of the fluids increased and the fluids changes from the weakly acidic and weakly reduced conditions to the neutral and weakly oxidizing conditions.

Conflict of interest statement We declared that we have no conflicts of interest to this manuscript entitled “Multi-stage hydrothermal processes at the Laozuoshan gold deposit in NE China: Insights from textures and compositions of sulfide assemblages”.

Acknowledgments This study was supported by National Science Foundation of China (No. 41272062), Key Laboratory of Mineralogy and Metallogeny (GIGCAS, KLMM20170103), MLR Key Laboratory of Mineral Resources Evaluation in Northeast Asia (DBY–KF–18–04), Key Laboratory of Earth and Planetary Physics (IGGCAS, DQXX201706), Fundamental Research Funds for the Central Universities (N170106001) and China Postdoctoral Science Foundation (2019M651136). Additional microanalytical assistance was kindly provided by Yiran Zhou (Northeastern University). Thanks to Ansheng Zhao for providing the basic research data, and Yandong Peng and Yufeng Shao for their help in the field survey. Thanks to ELSEVIER Webshop for Language Editing Services.

References An, R., Wang, K.Y., Ma, X.L., Liang, Y.H., Wang, Y.C., Wang, Z.G., 2017. Evolution mode for the ore-forming fluid system of the Laozuoshan skarn-magmatic hydrothermal vein gold deposit, Heilongjiang Province, China. NORTHWESTERN GEOLOGY 50, 122-135 (in Chinese with English abstract). doi: http://doi.org/10.19751/j.cnki.61-1149/p.2017.02.014.

Chen, Y.J., Chen, H.Y., Zaw, K., Pirajno, F., Zhang, Z.J., 2007. Geodynamic settings and tectonic model of skarn gold deposits in China: An overview. Ore Geology Reviews 31, 139-169. doi: https://doi.org/10.1016/j.oregeorev.2005.01.001. Cheng, F., 2004. The metallotect and Metallogenic Model of Gold in Jiamusi Massif. Changchun: Jilin University (in Chinese with English abstract). Ciobanu, C.L., Cook, N.J., Pring, A., 2005. Bismuth tellurides as gold scavengers. In: Mao J. W, Bierlein F. P., eds. Mineral Deposit Research: Meeting the Global Challenge Springer, Berlin Heidelberg, Berlin, Heidelberg, pp. 1383-1386. doi: http://doi.org/10.1007/3-540-27946-6_352. Ciobanu, C.L., Cook, N.J., Utsunomiya, S., Pring, A., Green, L., 2011. Focussed ion beam–transmission electron microscopy applications in ore mineralogy: Bridging micro- and nanoscale observations. Ore Geology Reviews 42, 6-31. doi: https://doi.org/10.1016/j.oregeorev.2011.06.012. Dai, L.D., Li, H.P., Wang, S.Y., Wei, J.H., 2003. Geochemical characteristics of gold polymetallic deposits as exemplified by the Laozuoshan deposit, Heilongjiang, China. Chinese Journal of Geochemistry 22, 89-96. doi: http://doi.org/10.1007/BF02831549. Deng, J., Wang, Q.F., 2016. Gold mineralization in China: Metallogenic provinces, deposit types and tectonic framework. Gondwana Research 36, 219-274. doi: https://doi.org/10.1016/j.gr.2015.10.003. Foster, M. D., 1962. Interpretation of the composition and a classification of the chlorites. USGS Prefessional Paper 414-A, p. 33. Fisher, N.H., 1945. The fineness of gold, with special reference to the Morobe Goldfield, New Guinea. Econimic Geology 40, 449-495.

Fuertes-Fuente, M., Martin-Izard, A., Nieto, J.G., Maldonado, C., Varela, A., 2000. Preliminary mineralogical and petrological study of the Ortosa Au-Bi-Te ore deposit: a reduced gold skarn in the northern part of the Rio Narcea Gold Belt, Asturias, Spain. Journal of Geochemical Exploration 71, 177-190. doi: http://doi.org/10.1016/S0375-6742(00)00151-5. Gammons, C.H., Williams-Jones, A.E., 1997. Chemical mobility of gold in the porphyry-epithermal environment. Economic Geology and the Bulletin of the Society of Economic Geologists 92, 45-59. doi: https://doi.org/10.2113/gsecongeo.92.1.45. Gao, S., Huang, F., Gu, X.P., Chen, Z.Y., Xing, M.M., Li, Y.L., 2017. Research on the growth orientation of pyrite grains in the colloform textures in Baiyunpu Pb-Zn polymetallic deposit, Hunan, China. Mineral and Petrology 111, 69-79. doi: http://doi.org/10.1007/s00710-016-0465-z. Hao, Y.J., Ren, Y.S., Zhao, H.L., Lai, K., Zhao, X., Ma, Y.P., 2018. Metallogenic mechanism and tectonic setting of tungsten mineralization in the Yangbishan deposit in Northeastern China. Acta Geologica Sinica(English Edition) 92, 241-267. doi: http://doi.org/10.1111/1755-6724.13504. Harmandas, N.G., Fernandez, E.N., Koutsoukos, P.G., 1998. Crystal growth of pyrite in aqueous solutions. Inhibition by organophosphorus compounds. Langmuir 14, 1250-1255. doi: http://doi.org/10.1021/la970354c. Hayashi, K.I., Ohmoto, H., 1991. Solubility of gold in NaCl- and H2S-bearing aqueous solutions at 250-350°C. Geochimica et Cosmochimica Acta 55, 2111-2126. doi: http://doi.org/10.1016/0016-7037(91)90091-I. He, B.L., 2002. Discussion on the origin of gold ore deposit at the eastern section of Laozuoshan gold ore field. GOLD 23, 7-12 (in Chinese with English abstract).

He, B.L., Zhao, H.P., 2002. Discussion on Geological Characteristics and Origin of Jizhuagou Gold Deposit in Laozuoshan Gold Field. MINERAL RESOURCES AND GEOLOGY 16, 165-167 (in Chinese with English abstract). Heinrich, C.A., Eadington, P.J., 1986. Thermodynamic predictions of the hydrothermal chemistry of arsenic, and their significance for the paragenetic sequence of some cassiterite-arsenopyrite-base metal sulfide deposits. Economic Geology 81, 511-529. doi: https://doi.org/10.2113/gsecongeo.81.3.511. Inoue, A., 1995. Formation of clay minerals in hydrothermal environments. Veide. Origin and Mineralogy of Clay. Springer, Berlin, pp. 268-330. doi: https://doi.org/10.1007/978-3-662-12648-6_7. Kerrich, R., 1999. Geochemistry - Nature's gold factory. Science 284, 2101-2102. doi: http://doi.org/10.1126/science.284.5423.2101. Kitchaev, D. A., Ceder, G., 2016. Evaluating structure selection in the hydrothermal growth of FeS2 pyrite and marcasite. Nature Communications 7, 1-7. doi: http://doi.org/10.1038/ncomms13799. Kretschmar, V., Scott, S.D., 1976. Phase relations involving arsenopyrite in the system Fe-As-S and their application. Canadian Mineralogist 14, 364-386. Li, M.F., Ye, S.Q., Yang, Y.C., Zhang, G.B., Hou, X.G., Ming, T.X., Tang, Z., 2014. Geological and geochemical characteristics of Laozuoshan gold deposit in Heilongjiang and its metallotectonic setting. Global Geology 33, 543-555 (in Chinese with English abstract). Li, W.S., 1986. The characteristics and metallogenic model of Laozuoshan gold deposit. Geology and Prospecting 22, 2-10 (in Chinese). Li, Y., Zhang, A.C., Chen, J.N., Gu, L.X., Wang, R.C., 2017. Formation of phosphorus-rich olivine in Dar al Gani 978 carbonaceous chondrite through fluid-assisted metamorphism. American Mineralogist 102, 98-107. doi: https://doi.org/10.2138/am-2017-5881.

Li, Y.X., 2012. The study on ore genesis and metallogenic geological model of Laozuoshan gold deposit in Heilongjiang province. Changchun: Jilin University (in Chinese with English abstract). Loucks, R.R., Mavrogenes, J.A., 1999. Gold solubility in supercritical hydrothermal brines measured in synthetic fluid inclusions. Science. 284, 2159-2163. doi: http://doi.org/10.1126/science.284.5423.2159. Meinert, L.D., 1998. A Review of skarns than contain gold. In: Lentz, D.R. (Ed.). Mineralized Intrusion-related Skarn Systems, Mineralogical Association of Canada Short Course series, 26 Mineralogical Association of Canada, Quebec city, Que., Canada, pp. 359-414. Meinert, L.D., 2000. Gold in skarns related to epizonal intrusions. In: Hagemann, S.G., Brown, p.e. (Eds.), Gold in 2000 Reviews in Economic Geology vol. 13. Society of Economic Geologists, Inc., Denver, pp 347-375. Meinert, L.D., Dipple, G.M., Nicolescu, S., 2005. World skarn deposits. Economic Geology 100th Anniversary Volume. pp. 299-336. Meng, L., Huang, F., Liu, J., Xing, M.M., Wan, Q., Ling, J.Q., Gao, S., Gao, W.Y., 2017. The genesis of nano-micron-sized spheroidal aggregates of FeS2 in the Laozuoshan

gold

deposit,

Heilongjiang

Province,

NE

China.

Journal

of

nanoscience

and

nanotechnology

17,

6539-6548.

doi:

http://doi.org/10.1166/jnn.2017.14448. Murowchick, J.B., 1992. Marcasite inversion and the petrographic determination of pyrite ancestry. Economic Geology 87, 1141-1152. doi: https://doi.org/10.2113/gsecongeo.87.4.1141.

Nan, H.F., 2018. Investigation of geologic features and genesis in Dongfengshan gold deposits. Nonferrous Metals Engineering 8, 93-97 (in Chinese with English abstract). Ohfuji,

H.,

Rickard,

D.,

2005.

Experimental

synthesis

of

framboids-a

review.

Earth-Science

Reviews

71,

147-170.

doi:

http://doi.org/10.1016/j.earscirev.2005.02.001. Putnis, A., 2002. Mineral replacement reactions: from macroscopic observations to microscopic mechanisms. Mineralogical Magazine 66, 689-708. doi: http://doi.org10.1180/0026461026650056. Qian, G.J., Xia, F., Brugger, J., Skinner, W.M., Bei, J.F., Chen, G.R., Pring, A., 2011. Replacement of pyrrhotite by pyrite and marcasite under hydrothermal conditions

up

to

220°C:

An

experimental

study

of

reaction

textures

and

mechanisms.

American

Mineralogist

96,

1878-1893.

doi:

https://doi.org/10.2138/am.2011.3691. Rickard, D., Luther, G.W., 2007. Chemistry of iron sulfides. Chemical Reviews 107, 514-562. doi: http://doi.org/10.1021/cr0503658. Rottier, B., Kouzmanov, K., Wälle, M., Bendezu, R., Fontbote, L., 2016. Sulfide replacement processes revealed by textural and LA-ICP-MS trace element analyses: Example from the early mineralization stages at Cerro de Pasco, Peru. Economic Geology 111, 1347-1367. doi: https://doi.org/10.2113/econgeo.111.6.1347. Schoonen, M.A.A., Barnes, H.L., 1991a. Reactions forming pyrite and marcasite from solution: I. Nucleation of FeS2 below 100°C. Geochimica et Cosmochimica Acta 55, 1495-1504. doi: https://doi.org/10.1016/0016-7037(91)90122-L.

Schoonen, M.A.A., Barnes, H.L., 1991b. Reactions forming pyrite and marcasite from solution: II. Via FeS precusors below 100°C. Geochimica et Cosmochimica Acta. 55, 1505-1514. doi: https://doi.org/10.1016/0016-7037(91)90123-M. Schoonen, M.A.A., Barnes, H.L., 1991c. Mechanisms of pyrite and marcasite formation from solution: III. Hydrothermal processes. Geochimica et Cosmochimica Acta. 55, 3491-3504. doi: https://doi.org/10.1016/0016-7037(91)90050-F. Sharp, Z.D., Essene, E.J., Kelly, W.C., 1985. A re-examination of the arsenopyrite geothermometer; pressure considerations and applications to natural assemblages. Canadian Mineraloigst 23, 517-534. Simon, G., Huang, H., Penner-Hahn, J.E., Kesler, S.E., Kao, L.S., 1999. Oxidation state of gold and arsenic in gold-bearing arsenian pyrite. American Mineralogist 84, 1071-1079. doi: https://doi.org/10.2138/am-1999-7-809. Sui, J.X., Li, J.W., Wen, G., Jin, X.Y., 2017. The Dewulu reduced Au-Cu skarn deposit in the Xiahe-Hezuo district, West Qinling orogen, China: Implications for an intrusion-related gold system. Ore Geology Reviews 80, 1230-1244. doi: https://doi.org/10.1016/j.oregeorev.2016.09.018 Tan, C.Y., 2009. General Characteristics of the Tectonic-Metallogenic Systems of Main Ore Deposits in Heilongjiang Province, Northeast China. Beijing: China University of Geosciences(Beijing) (in Chinese with English abstract). Wang, L., Zhu, Y.F., 2015. Multi-stage pyrite and hydrothermal mineral assemblage of the Hatu gold district (west Junggar, Xinjiang, NW China): Implications for metallogenic evolution. Ore Geology Reviews 69, 243-267. doi: http://doi.org/10.1016/j.oregeorev2015.02.021.

Wang, S., 2014. Study on Phanerozoic magmatic evolution and metallogenesis in the eastern Jilin-Heilongjiang Provinces. Changchun: Jilin University (in Chinese with English abstract). Wilde, S. A., Zhang, X.Z., Wu, F.Y., 2000. Extension of a newly identified 500Ma metamorphic terrane in North East China: further U–Pb SHRIMP dating of the Mashan Complex, Heilongjiang Province, China. Tectonophysics 328, 115-130. doi: http://doi.org/10.1016/S0040-1951(00)00180-3. Williams-Jones, A.E., Bowell, R.J., Migdisov, A.A., 2009. Gold in solution. Elements 5, 281-287. doi: http://doi.org/10.2113/gselements.5.5.281. Wu, M., Li, L., Sun, J.G., Yang, R., 2018a. Geology, geochemistry, and geochronology of the Laozuoshan gold deposit, Heilongjiang Province, Northeast China: Implications

for

multiple

gold

mineralization

events

and

geodynamic

setting.

Canadian

Journal

of

Earth

Sciences

55,

604-619.

doi:

http://doi.org/10.1139/cjes-2018-0038. Wu, M., Li, Y.X., Liu, G.X., 2018b. Characteristics of ore-forming fluid and genesis of Laozuoshan gold deposit, Heilongjiang Province. Journal of Jilin University(Earth Science Edition) 48, 1353-1364 (in Chinese with English abstract). doi: http://doi.org/10.13278/j.cnki.jjuese.20180074. Xue, M.X., 2012. Metalogenesis of endogenic gold deposits in Heilongjiang Province. Changchun: Jilin University (in Chinese with English abstract). Yang, J.Q., Wang, X.Q., Liu, D. S., Kong, H.Q., Liu, H.P., 2007. Division and characters of geotectonic unit of Heilongjiang Province. Global Geology. 26, 426-434+452 (in Chinese with English abstract). Zhang, L., Yang, Y.C., Han, S.J., Bao, J.W., Wang, F.B., Nie, S.J., 2016. Zircon U-Pb Dating and Geological Significance of Gneissic Granite in Xinli Gold Deposit of Heilongjiang. Journal of Earth Sciences and Environment 38, 638-648 (in Chinese with English abstract).

Zhang, L.Y., 2008. Study on geological characteristics and enrichment regularities of gold mineralization in Laozuoshan gold deposit, Heilongjiang Province. Changchun: Jilin University (in Chinese with English abstract). Zhang, Z.R., Chen, M.X., 1995. The application of the gold fineness research in geology. GOLD SCIENCE AND TECHNOLOGY 3, 21-24 (in Chinese). Zhao, A.S., Wang, Y., Lu, W.G., 2004. Study on ore-forming condition and prospecting potential of Laozuoshan gold deposit. GOLD 25, 20-23 (in Chinese with English abstract). Zhao, L.L., Wang, Z.Q., Zhang, X.Z., 2014. Detrital zircon U-Pb dating of Majiajie Group and its tectonic implications. Acta Petrologica Sinica 30, 1769-1779. Zhu,

Y.F.,

An,

F.,

Tan,

J.J.,

2011.

Geochemistry

of

hydrothermal

gold

deposits:

A

review.

Geoscience

Frontiers

2,

367-374.

doi:

https://doi.org/10.1016/j.gsf.2011.05.006.

Figure captions

Figure 1. (a) Sketch tectonic map (after Hao, 2018) and (b) simplified geological map of the Jiamusi massif (after Wilde, 2000). Figure 2. Geological map of the Laozuoshan gold deposit (after Zhao, 2004). Figure 3. (a) Geological map and (b) cross section of the A–A’ prospecting line of the NW section of the East ore belt in the Laozuoshan gold deposit. Figure 4. Photographs showing typical ore samples from the Laozoushan gold deposit. (a) Pyrrhotite and other sulfide aggregates sparsely disseminated in ore sample; (b) Aggregates consisting mainly of pyrrhotite, densely disseminated in ore; (c) Disseminated ore, and coarse-grained pyrrhotite densely disseminated in quartz and calcite; (d) Coarse-grained pyrrhotite and arsenopyrite sparsely disseminated in chlorite and calcite; (e) Coarse-grained pyrite and arsenopyrite

distributed in massive ore; (f) Medium- to coarse-grained pyrite distributed in actinolite and epidote; (g) Coarse-grained pyrite and chalcopyrite cemented by quartz and calcite; (h) Pyrite and quartz in sulfide ore; (i) Dense sulfide ore with a massive structure. Abbreviations: Po – pyrrhotite; Apy – arsenopyrite; Py – pyrite; Cpy – chalcopyrite; Grt – garnet; Di – diopside; Ep – epidote; Cal – calcite; Qtz – quartz; Chl – chlorite; Act – actinolite; Cb – carbonate. The black bar represents 3 cm. Figure 5. The paragenetic sequence of minerals in the Laozuoshan gold deposit. The shadow bar stands for the main ore-forming process (modified after He, 2002). Figure 6. Photomicrographs showing mineralogical and textural features of different mineral assemblages from Variscan skarn mineralization period in the Laozuoshan gold deposit. (a) Pyrite (Py-1) inclusions in coarse-grained pyrrhotite (Po-1) coexisting with chalcopyrite (Cpy-1). (b) Native gold (Au-1) as fracture infillings in the gangue mineral. The pyrrhotite (Po-1) particles are cemented by arsenopyrite (Apy-1). (c) Native gold as interstitial infillings between arsenopyrite (Apy-1) and pyrrhotite (Po-1). (d) Reflected-light photomicrograph showing textural relationships between pyrrhotite (Po-1) and pyrite (Py-1), arsenopyrite (Apy-1) or chalcopyrite (Cpy-1). (e) Biotite, chlorite and calcite occur as fracture infillings in garnet and diopside. (f). Backscattered electron images showing the core-rim texture of garnet coexisting with pyrrhotite, diopside and chlorite. (g) Native gold (Au-2) and tellurbismuth in arsenopyrite (Apy-2), coexisting with pyrrhotite (Po-1) and pyrite (Py-2). (h) The close textural relations between calcite, chlorite and Feldspar. (i) Chlorite and calcite occurring as fracture infillings in arsenopyrite. Abbreviations: Po – pyrrhotite; Apy – arsenopyrite; Cpy – chalcopyrite; Py – pyrite; Au – native gold; BiTe – Tellurbismuth; Grt – garnet; Di – diopside; Bt – biotite; Chl – chlorite; Cal – calcite; Fsp – Feldspar

Figure 7. Photomicrographs and backscattered electron images showing the mineralogical and textural features of sulfides and gangue minerals from the Yanshanian hydrothermal mineralization period in the Laozuoshan gold deposit. (a) The textural relationships between quartz and carbonate after the hydrothermal action. (b) Reflected-light photomicrograph showing the euhedral to subhedral arsenopyrite (Apy-3). (c) The textural relationships between chalcopyrite (Cpy-2) and pyrrhotite (Po-2) or sphalerite. (d) Pyrrhotite (Po-1) with oriented fracture inclusions replaced by chalcopyrite (Cpy-2). (e) Pyrrhotite (Po-2) and sphalerite inclusions in coarse-grained chalcopyrite coexisting with euhedral pyrite (Py-3). (f) The textural relationships between euhedral to subhedral pyrite (Py-3) and subhedral to anhedral marcasite. (g) Arsenopyrite (Apy-4) coexisting with galena disseminated in gangue mineral. (h) Transmitted light photomicrograph showing euhedral-subhedral quartz coexisted with sericite and calcite. (i) Fe-Oxide occurring as inclusions in pyrrhotite (Po-1) with oriented fracture and subhedral pyrite (Py-4). (j) The anhedral pyrite (Py-4) inclusion in subhedral pyrrhotite (Po-1) with oriented fracture. (k) Pyrrhotite (Po-1) is retained as a pseudomorph with Fe-Oxide. (l) Reflected-light photomicrograph showing the textural relationships between subhedral pyrite and fine-grained porous marcasite (Mc) + pyrite (Py-4). (m) Backscattered electron image showing the pyrrhotite affected by hydrothermal metasomatism. (n) The textural and compositional features of pyrrhotite from inside to outside (data from EDS for Fig. 7m). (p) Raman of the fine-grained porous marcasite + pyrite. (q) Calcite coexisted with fine- to intermediate-grained quartz occurring as inclusions in the pyrite + marcasite aggregates. Abbreviations: Apy – arsenopyrite; Cpy – chalcopyrite; Py – pyrite; Po – pyrrhotite; Sp – sphalerite; Mc – marcasite; Gn – galena; Fe-Oxide – iron oxide; Q – quartz; Cal – calcite; Cb – carbonate; Ser – sericite.

Figure 8. Backscattered electron images showing the textural features of pyrite and marcasite assemblages in the hydrothermal mineralization period. The dashed line is the boundary between the fine–grained porous marcasite + pyrite and euhedral pyrite. Figure 9. (a) Reflected light images of pyrite and marcasite; (b) SEM images of pyrite and marcasite; (c) Focused ion beam incision; (d) Focused ion beam-cut TEM chips; (e) Preparation of TEM images of fine-grained porous pyrite and marcasite flakes using the FIB-TEM system; (f) High-resolution images of the boundary between pyrite and marcasite; (g-i) Electron diffraction images of fine-grained porous pyrite and marcasite. Figure 10. (a) The distribution characteristics of Fe and Co in the Arsenopyrite component and (b) the Fe–S–As distribution characteristics of the Arsenopyrite component. All data based on the results of arsenopyrite analyses by EPMA given in Table 1. Figure 11. The distribution characteristics of Au and Ag in the gold component. All data based on the results of gold analyses by EPMA given in Table 2. Figure 12. Scatter diagram of major elements and trace elements of pyrrhotite, pyrite and marcasite. All data based on the results of pyrrhotite, pyrite and marcasite analyses by EPMA given in Table 3 to Table 5. Abbreviations: Po – Pyrrhotite; Py – Pyrite. Figure 13. pH vs. log fO2 diagrams (modified from Heinrich and Eadington, 1986) showing calculated predominance fields for arsenic species in equilibrium with a sulfur–bearing aqueous fluid. The blue field stands for the formation conditions of arsenopyrite during the skarn mineralization period in the Laozuoshan gold deposit. Figure 14. Schematic diagram of textural relationships between pyrite and marcasite during the replacement processes affecting pyrrhotite. Abbreviations: Po – pyrrhotite; Mc – marcasite; Py – pyrite; Py+Mc – pyrite+marcasite; Cal – calcite; Cb – carbonate; Fe-oxide – iron oxide.

Figure 15. Log fS2-T diagram with isopleths of arsenopyrite composition from Kretschmar and Scott (1976) and modified by Sharp et al., (1985). Shaded areas show the formation temperature of arsenopyrite (Apy-2) from the Stage III of the Laozuoshan gold deposits based on the As atomic percent of arsenopyrite by EPMA. Figure 16. Nomenclature and classification of chlorite from the Laozuoshan gold deposit (base map after Foster, 1962). All data based on the results of chlorites analyses by EPMA given in Table 6.

Table 1. Compositions of the different generations of arsenopyrite in Laozuoshan gold deposit (Data from EPMA, wt.%) S tage

N o.

C o

L

L7D-2

.08

.19 L-

7B-5 A py1

L7B-6

2 .96

L7B-11

.82

M ax

4 .19

M in A ve.

.69

4

7.79

0

3

4

3 2.17

4

<

3

4

4

mdl

.02

mdl

.04

.24

mdl <

mdl 0

< 8.97 < mdl

–

8.06 –

1 8.60

mdl

0

<

< mdl

< mdl

–

< mdl

.01

mdl

<

<

<

1

mdl

mdl

mdl

<

0

<

1

mdl

.01

mdl

<

0

<

1 8.06

<

.01

mdl

< mdl

mdl

mdl

8.53

mdl

mdl

<

1

<

<

0

0

mdl

mdl

.75

8.97 <

<

0

<

3 2.24

0

0

3

< mdl

.10

.02

0.09

0

mdl

mdl

mdl 0

.01

s*

e+Co *

S *

3

3

3

02.18

4.529

3.794

1.677

1

3

3

3

01.70

4.427

4.033

1.540

1

3

3

3

01.29

4.949

3.442

1.608

1

3

3

3

00.84

3.896

3.908

2.196

1

3

3

3

01.25

4.562

3.983

1.455

1

3

3

3

02.18

5.531

3.878

0.591

1

3

3

3

5.53

1 00.84

–

F

1

02.18 <

A

T otal

<

<

<

1

e

mdl

mdl

S

<

<

1

<

d

mdl

8.48

C

<

1

<

<

g

mdl

8.70

mdl

mdl

.09

mdl

3.98

0

0

<

<

A

1 8.84

mdl

mdl

.21

.01

<

0

S

< mdl

mdl

.75

.01

2.07

6.67 2

3

<

0

0

Z n

mdl

.04

.02

1.97

9.02 1

.09

4

0

<

3

C u

.26

mdl

0.09

9.02

0

3

4

N i

.02

3.18

7.58 2

3

4

6.67

A u

3.98

7.75 2

.99

4

7.70 4

F e

7.99 2

L7B-2

s 1

DK-4-2 .09

A

4.03 3

3.90

2.20 3

3.44

3 0.59

1

3

3

3

01.57

4.649

3.840

1.511

S. D.

1 .04

L ZS-2-4 L ZS-3-1

.29

.07

L ZS-3-4 L A ZS-3-3 py-2

3

0 .19

L ZS-3-3 6

.29

L ZS-3-3 8

0 .04

M ax

0 .29

M

3

4

3 4.75

4

mdl

3 5.53

4

<

3

<

0

0

<

<

0

0

0

< mdl

0 .02

<

< mdl

.02

.03 1

0

0

1

< mdl

.02

.03

9.66 <

<

1

<

0

< mdl

<

.549

.212

0 .521

3

3

02.41

3.453

3.916

2.631

1

3

3

3

00.47

3.297

4.094

2.609

9

3

3

3

3.080

4.290

2.630

1

3

3

3

00.95

2.919

4.301

2.780

1

3

3

3

01.80

3.465

3.782

2.753

1

3

3

3

00.35

3.266

4.015

2.719

1

3

3

3

01.16

3.149

4.279

2.571

1

3

3

3

02.41 <

0

3

9.90

mdl

.02

mdl

9.40

.01

<

1

<

<

0

1

< mdl

mdl

mdl

9.34

mdl

.01

1

<

<

<

.54

< mdl

mdl

mdl

9.63

mdl

mdl

.01 <

<

<

0

mdl

mdl

mdl

.03 3

<

1

<

<

<

0

< mdl

mdl

mdl

9.52

0 .01

mdl

–

.01

<

1

0

<

mdl

9.21

0

<

1

<

.01

mdl

mdl

mdl

5.56 4

mdl

1

9.29

mdl

–

.32

9.66

mdl

.01

0

<

0

<

<

mdl

mdl

mdl

.01

<

<

<

0

<

<

<

0

–

mdl

mdl

.01

5.09

7.10 0

3

4

0

0

–

mdl

.01

.02

5.46

6.14

<

3

4

< mdl

mdl

5.10

5.95

0

3

4

0 .26

.03

4.86

6.87

0

3

4

5.81

0 .01

5.56

5.51 0

.13

4

6.03 0

1 .31

7.10 0

L ZS-3-3

.76 0

.04

0

9

3.47

4.30 3

2.78 3

3

in

.04 A

ve.

0 .15

S. D.

5.51 4

6.20 0

.11

4.75

mdl 3

5.19 0

.57

mdl

mdl –

0

mdl –

9.21 –

.01 0

.33

mdl 1

–

9.44 0

.01

–

–

–

0

<

<

0 .17

mdl 0

9.90 –

.01

0 .01

mdl

0

–

.01

2.92

3.78

2.57

1

3

3

3

01.01

3.233

4.097

2.670

0

0

0

0

.87

.198

.204

.080

Table 1 (Continued) L DK-1-9 .35 L DK-1-8 .74 L DK-1-7 .34 A py-3

L DK-1-5 .23 L DK-1-6 .21 L DK-1-3 .08 M

0

4

9.24 1

4.28 4

8.36 0

0

4

1

3

4

3 4.43

5

0

0 .03

3

0

0 .09

0

<

< mdl

0

<

< mdl

<

0

0

<

< mdl

< mdl

0

< mdl

.03

mdl 1

<

<

1

< mdl

mdl

mdl

7.49

<

<

1

< mdl

mdl

mdl

7.56

<

<

1

< mdl

mdl

mdl

6.93

mdl

0

1

<

< mdl

.01

6.57

mdl

mdl

1

0

<

< mdl

7.25

.01

mdl

.04

0

<

0

1 7.64

.01

mdl

.06

.02

<

0

0

mdl

mdl

.09

.04

4.57

0

0

3

mdl

.02

.02

4.08

8.05

<

3

4

.09

mdl

3.81

7.63 0

3

5

9.21

0 .02

2.90

0.71 0

3

< mdl

0

<

1

3

3

3

01.62

5.970

3.917

0.113

1

3

3

2

00.28

5.818

4.326

9.856

1

3

3

2

01.55

7.502

3.861

8.637

1

3

3

2

00.55

6.511

4.136

9.353

1

3

3

3

00.06

5.202

4.471

0.328

1

3

3

3

00.18

5.537

4.234

0.228

1

3

3

3

ax

.74 M

in

0 .08

A ve. S.

L8B-3 L8B-5

.08 L-

8A1-3

.18

LA

8A1-6

0 .04

4

4

4

4

5.79

.56

mdl

3.69

6.57

mdl

mdl

9.59

mdl

mdl

mdl

0.09 1

< mdl

<

<

<

0

0 .01

3.86

2 8.64 2

00.71

6.090

4.157

9.753

0

0

0

0

.70

.819

.236

.649

1

3

3

3

01.75

3.463

3.678

2.859

1

3

3

3

02.36

3.078

3.655

3.267

1

3

3

3

00.58

3.903

3.174

2.923

9

3

3

3

3.330

3.450

3.220

1

3

3

3

00.55

3.296

3.208

3.496

1

3

3

3

< mdl

5.20

3

3

< mdl

3

0.33

3

< mdl

4.47

1

< mdl

mdl

.01

–

.01

<

1 9.53

0

7.50

1 00.06

–

.01

mdl

mdl

<

0

<

01.62

mdl

mdl

mdl

9.29

<

<

2

<

<

–

1

<

<

0 .29

<

mdl

mdl

0

mdl

mdl –

.42

mdl

mdl

.98

.01

.03 <

1

0

<

0

<

1

–

0 .01

.18

.02

4.22

–

0

0

3

mdl

.01

7.24

0

<

3

7.64 <

–

.03

mdl

5.33

mdl

0

<

3

<

0

0

3

.01

.07

.01

4.93

0

0

0

mdl

.02

.02

.61

6.42

0

3

1

.09

.02

4.01

6.68 0

3

4

6.62 0

.04

2.90

.11 0

.05

4

8.87 0

.62

4.57

7.63 0

.49

D.

0.71

9.89

py-4 L8A1-9

0 .31

M ax M in

4

3

4

0

3

0

<

0

0

<

<

2

<

0

1

0

<

< mdl

< mdl

–

< mdl

.01

mdl 1

< mdl

.01

9.29 –

< mdl

0.09

mdl –

1 9.88

mdl

mdl 0

< mdl

.01

.09 0

< mdl

.98

mdl 3

0 .09

.05

3.69 4

0 .05

5.33

5.79 0

3 4.04

6.68 0

.04 A

6.18 0

.31

4

02.36 <

mdl –

9 9.89

–

3.90

3.68 3

3.08 1

3.50 3

3.17 3

3 2.86

3

3

ve.

.13 S.

D.

6.34 0

.11

.36

4.44 0

.01 0

.67

.42 0

.02

9.68 0

.36

–

–

0 .31

–

–

–

01.03

3.414

3.433

3.153

1

0

0

0

.00

.306

.239

.262

Notes: As* = As atom percent (at.%) in Apy; Fe + Co*= (Fe + Co) at.% in Apy; S*= S at.% in Apy;
Table 2. Compositions of the different generations of gold in Laozuoshan gold deposit (Data from EPMA, wt.%) S tage

Sa mple

A s

L-7 D-1

<

L-7

D-3

.04

B-1

u-1

mdl L-7

B-2

.50

mdl

B-3

.76

.01

x

.04

n

mdl

.10

.01

7.76

.68

3.25

<

–

0

<

<

0 .09

7.45

.05

.04

4.54

mdl

5.44

.01

85 6.71

9 3.19

0 .01

84

1

<

0

84

5.444

04.78

mdl

8.497

5.484

7.85

.03

84

9

0

<

1

7.44

.01

83

9

0

0

1

0 .15

mdl

8.265

6.579

04.78

.03

82

1

0

<

1

0

0 .01

1

0

<

<

6.706

9 3.19

mdl

mdl

5.08

.27

mdl

1

0

<

0

85

1 01.99

mdl

.04

4.90

.16

.02

mdl

0

<

0

5.47

.23

mdl

.55

mdl 8

mdl

mdl

mdl

.10 <

<

<

7

0

mdl

mdl

6.93

mdl

1

02.64

mdl

.01

1

<

0

‰

otal

mdl

.02

T

<

0

1

0

e

.01

5.19

S

0

1

0

<

<

<

8

0

0

mdl

2.49

.50

mdl

1

7.45

.05

C d

4.54

.07

.02

g

0

0

<

<

8

2

<

Av

1.53

.10

mdl

mdl

.27

.01

A

0

0

<

<

8

0

0

Mi

6.64

mdl

mdl

mdl 8

0

0

Ma

7.76

<

<

<

S

n

.55

mdl

Z

0

<

7

2

<

L-7

e.

.14

u

mdl

4.16

C

<

8

0

<

i

6.93

.25

N

8

0

0

L-7

u

.34

.01

A

0

0

L-7

A

e

mdl

D-2

F

8.26 9

9.65

82

84 3.567

S. D.

0 .02

LZ S-3-1

mdl

A u-2

Ma x

n

.19

mdl

e.

0 .03

0 .05

S. .05

8 9.87

0 .11

0

mdl <

mdl 9

< mdl

–

–

< mdl

–

–

0

< mdl

0

.33

.14

.01

.02

.02 0

.88

0 .01

9

<

–

92 4.59

9 7.68

–

92 4.588

9.83

mdl 0

9.411

7.68

mdl

90

9

<

0

8

0 .18

.03

1.211

9.83

mdl

92

9

<

0

7

0

0 .01

9

9

<

0

9.8 70

8.21

mdl

.01

.01

<

0

7

4. 26

mdl

.03

.33

.34

.01 0

.32

0

0

9

0

0 .01

.01

.01

.34

.01

0.23 0

.08

mdl

.01

.02

.73

.09

0

7

0

0

<

.03

mdl

.01

1

<

0

<

<

.09

mdl

mdl

0

<

<

<

9 0.45

<

mdl

mdl

0 .01

mdl

mdl

9.87

.22

<

8

0

<

Av

D.

.03

.10

mdl

0.45

0

<

9

0

0

Mi

0.38

.19

.10

9

0

0

–

.45

.10

.05

3

0

0

LZ S-3-3

.92 <

LZ S-3-2

0

90 9.41

9 8.57

91 8.403

1. 12

Note:
7.9 69

Table 3. Compositions of the different generations of pyrrhotite in Laozuoshan gold deposit (Data from EPMA, wt.%) St age

Sa mple

C o

L ZS-2-8

.07

.06

ZS-3-2 Po -1

8

.07

L ZS-3-3 2

.02

mdl

0 .06

L

L

<

0

0

<

0

<

0

0 .18

0

<

3

<

<

<

0

< mdl

0

2

87

1.23 4

1.0

1.20 1

1.0 79

1.24 2

1.0 93

1

1

1.21

1.0

1

00.38 <

1.0

1

00.56

1.23 8

96

00.19

mdl

.01 0

< mdl

mdl

mdl 3

<

91

9 9.82

1.20

1.0

1

0

(at.%)

8

90

00.34

.01

mdl

mdl

9.02 <

<

3

0

<

03

9 9.93

.01

mdl

mdl

9.41

<

0

3

0

S

1.1

1 00.73

.01

mdl

.01

9.83

mdl

.07 0

<

<

0

3

<

0

<

1 00.40

mdl

.01

mdl

8.50

mdl

mdl

.03

<

0

<

9.55

mdl

.01

mdl

mdl 6

<

<

6

0 .01

mdl

mdl

1.01 <

0

6

<

<

mdl

mdl

(at.%)

otal

mdl

Fe

T

<

<

<

3

e

mdl

mdl

S

<

<

3

<

d

mdl

8.86

C

<

3

0

<

g

mdl

9.68

.06

mdl

mdl

.02

1.06

mdl 0

6

0

<

<

0

0

A

3 8.72

.01

.05

mdl

mdl

0.27

.01

<

6

0

<

S

0 .01

.01

mdl

mdl

1.23

mdl

DK-4-7 .07 L

<

0

DK-4-6 .08

6

<

<

<

Z n

mdl

mdl

mdl

0.71

mdl

DK-4-4 .07 L

0.86

u

mdl

.03

C

<

0

6

<

i

.01

0.93

N

0

6

0

0

u

1.59

mdl

A

6

<

0

L

e

mdl

.07

F

<

0

L ZS-3-7

s 0

L ZS-2-6

A

1.22 9

1.0 92

1.21 7

1.0

1.23

Fe/S (at.%) 0.913

0.881

0.899

0.881

0.913

0.869

0.889

0.898 0.879

DK-4-1 .09

mdl

0.49

.01

.02

.03

mdl

9.50

.01

.02

mdl

00.17

83

2

1 L DK-4-1 4

0 .08

L7D-4

.08

.07

ax

.09 M

in

D.

.01

ZS-5-1 0

0 .06

6

.41

.02

.01

1.05

.01

mdl

.02

mdl

mdl

0 .01

< mdl

–

< mdl

–

–

.44 0

3 9.67

0 .01

< mdl

–

0 .02

< mdl

4 1.0

87

1.24 3

1.1 0 1.0

1

4 –

1.23

8

00.26

0

9

85

9 9.72

1.23

1.0

1 00.73

2

81

1 00.68

9.36

.05

.02

mdl

.02

mdl

00.28

1.23

1.0

1

<

0

<

3

0

<

.01

8.50

.02

mdl

76

00.23

mdl

1.0

1

<

<

0

3

0

0

<

9.85

mdl

.02

.01

9.72

mdl

mdl

9

<

<

0

3

<

0

0

<

.18

mdl

.01

9.85

mdl

mdl

mdl

<

<

<

3

0

<

0

0

6

.07

mdl

.01

mdl

.01

mdl

9.56

0

<

3

<

0

<

0

0

0

.03

mdl

0.76

mdl

mdl

9.73

.01

<

3

0

<

0

<

6

0 .01

0

<

0

0

3 9.51

mdl

.01

.03

.03

0.10 –

0

L

1.59

mdl

.07

.03

mdl

.01

.02

<

0

0

0

6

<

0

S.

-2

.02

.06

ve.

0.69

.01

.01

.02

0

0

0

6

0

0

A

Po

.01

md

.01

0.59

<

0

6

0

0

.02

0.40

mdl

0

6

<

0

M

0.10

mdl

.08

6

<

0

L7B-14

mdl 0

L7D-15

<

1.0 88

0 .308 1 00.83

93

0.87

4 1.23 7

0.874

1.20

0.01

1.0

0.879

0.91

8

07

0.873

1.24

1.22

0.0

0.873

0.886

0.015

0.883

L8C-1

0 .07

L8C-2

0

L-

4B-4

.06

4B-18

.05

L4B-19

mdl

.07

in

.05

ve.

mdl

.07 S.

0 .01

6

0 .01

0

0 .57

0

0 .01

.08

mdl

.01 0 .01

0 .93

0

<

< mdl

–

–

0

< mdl

1 0

.01

0 .01

1.25 0

1.1 0 1.0 7

– 00.18

.01

0

80

1

0

1.25

1.0

9 9.23

0

80

1 00.83

1.24

1.0

1 00.83

.02

1.0

1

0

1.18 0

70

00.64

.01

.02

mdl

9.18

0 .01

0

3

3

0

1.0

9

<

1.20 0

90

9.97

mdl

.02

.01

7.97 –

mdl

.01

0.11

mdl

0

00

9.23

1.19

1.1

9

<

<

0

4

<

0

0

4

0

<

<

9

<

<

1.1 00

9.86

mdl

mdl

mdl

0.11

.02

mdl

.06

0

0

<

4

<

0

<

9 9.91

mdl

.01

mdl

0.09

.01

.01

mdl

.01

<

0

<

<

0

<

3

0 .02

.01

mdl

9.76

mdl

mdl

.18

mdl

0.84

0

0

5

0

<

3

<

< mdl

mdl

7.97

mdl

.01

.10

.02

9.98 –

.13

.02

1.49

mdl

mdl

8.37

mdl

<

3

<

<

0

0

6

<

0

mdl

0.50

.02

.18

8.30

mdl

.01

3

<

0

0

<

6

0

0

A

0.36

mdl

.08

mdl

mdl

.01

mdl

<

0

<

<

6

<

0

M

9.98

.01

mdl

.02

0

<

0

5

<

0

M ax

mdl

mdl

mdl

1.15

<

<

6

<

0

.01

1.38

mdl

0

6

<

0

L-

1.49

mdl

.08

6

<

0

L-

D.

mdl

.08

8C-11

<

1.0 88

0 .603

Notes:
11

0.920

0.870

0.860

0.870

0.92

1.18

0.86

1 0.03 0

0.920

1.25

1.22

0.0

0.920

0.892

0.027

Table 4. Compositions of the different generations of pyrite in Laozuoshan gold deposit (Data from EPMA, wt.%) S tage

Samp le

C o

L-7D -5

0

LDK-

4-13

.06

P 4-15

.06 Max

Min

Ave.

S.D.

P 2-1

2-2

mdl

.09

7.48

mdl

0

–

.02 0 .06

4

0

6.53 <

mdl

.02

mdl 4

6.57

mdl

.37

mdl

<

< mdl

.01

mdl

.23

mdl

mdl

1.68

< mdl

5 2.04

–

.01

.01

01.09

.01 <

0 .01

8.68

3 0.53

.69

84

1

0.49

.60 0.

843

1 .658

0.

9

.038

833

0.50

0

0.

0.01 5

1 .612

0. 834

0.50

1

0.

9

5

.671

006

8.28

0.49

1

0.

9

0.53

1

0.

85

0.50

0

.691

841

(at.%)

6

.603

837

Fe/S

1

0.

0. 557

mdl

850

1

0

< mdl

00.62

.669 0.

1

0

0

< mdl

<

.01

844

1 01.85

mdl –

0

5

<

mdl

.01

00.62

.02

1

1

0

<

0

1

<

0 .01

5

0

mdl

mdl

01.15

mdl

0.

1

<

<

<

01.85

mdl

(at.%)

1

<

<

0

5

3.17

<

mdl

.02

1.39 –

1

<

<

mdl

.69

.08

4.20

0

S

(at.%) 1

00.73

.02

mdl

mdl 5

<

0

0

<

.01

mdl

.06

3.58 0

<

0

0

4

.74

mdl

.02

2

<

0

0

< mdl

<

4

.32

0

mdl

mdl

<

otal

.01

Fe

T

0

<

<

5

e

mdl

mdl

S

<

0

5

<

d

.02

4.20

C

<

5

<

<

g

mdl

1.39

mdl

mdl

.17

mdl

7.08

<

0

0

<

A

5 3.51

.01

mdl

mdl

.04

6.73 –

.07

.01

mdl

.74

.17 0

4

<

0

.04

6.96

mdl

.05

mdl

<

2

0

S

n

mdl

.05

Z

<

0

<

4

<

0

LZS-

6.73

u

.01

.04

C

0

0

4

<

0

LZS-

y-2

mdl

i

.01

7.48

N

0

4

<

0

u

7.14

mdl

A

4

<

0

LDK-

e

mdl

.09

F

<

0

LDK-

y-1

s

.05

4-9

A

0.51 7

1 .623

0.51 4

LZS2-3

0 .07

LZS3-9

mdl 0

.05 LZS-

3-11

LZS-

0

LZS3-37

0 .05

lzs-32-4

lzs-3-

0

lzs-32-7

0 .05

lzs-32-8

0

0

4

0

<

4

<

0

0

<

0

0

< mdl

0

0

0

<

<

<

< mdl

<

<

1

0.

0.49 4

1 .662

0.

0.50 6

.659

827 9

1

0.

9

0.50 6

.650

820

9.67

1

0.

9

0.49 2

.629

835

9.18

1

0.

9

0.50 3

.657

824

9.79

mdl

mdl 0

<

1

0.

9

0.51 4

.650

814

8.33

mdl

.02

mdl 5

0

<

5

<

1

0.

9

0.50 9

.631

831

8.73

mdl

.02

mdl

3.28

<

0

5

<

1

0.

9

0.50 3

.647

838

9.40

mdl

mdl

.01

3.19

0

<

5

<

1

0.

9

0.50 8

.654

839

9.15

mdl

.02

mdl

2.90

.08

.06 <

0

<

<

5

<

1

0.

9

0.51 2

.628

833

9.71

mdl

mdl

mdl

2.23

.07

.01

mdl 0

<

<

5

0

<

0.

9

0

1 .638

827

9.64

.01

mdl

mdl

3.11

.01

mdl

mdl

.03 4

<

5

<

<

<

9

<

<

0. 839

8.49

mdl

mdl

mdl

2.90

mdl

mdl

mdl

mdl

6.20 0

0

0

0

<

5

0

0

<

9 9.49

.01

.01

mdl

2.28

.01

.01

mdl

.01

5.80

.04 0

4

<

<

<

<

<

<

5

< mdl

mdl

mdl

2.81

mdl

mdl

mdl

mdl

6.65

.04

.07 lzs-3-

0

<

<

4

<

<

5

<

< mdl

mdl

3.04

mdl

mdl

mdl

mdl

6.03

.04

0

4

0

<

5

<

<

0 .01

2.20

mdl

mdl

mdl

.03

5.48

.02

.09

4

<

0

<

<

0

<

5 2.51

mdl

.02

mdl

mdl

6.39

mdl

.03

2-6

<

0

lzs-3-

4

<

<

<

< mdl

mdl

mdl

mdl

6.82

mdl

.11

2-5

<

<

0

4

< mdl

mdl

.02

6.85

mdl

0

4

0

< mdl

.01

6.51

.01

.04

4

<

0

0 .02

6.21

mdl

.05

3-13

<

0

LZS-

4 6.88

mdl

.04

3-12

<

0.49 8

1

0.50

2-9

.04 lzs-3-

2-10

0 .09

lzs-32-11

2-13

.08

2-15

.08

.07 Max

Min

Ave.

S.D.

P 7

.02 0

.11

.06

.02

.02

.03 0

.06

.43

mdl

5.88

< mdl

4 5.91

–

.02 4

< mdl

0

mdl

.01

.04

.01

.46 0

.03 0

.01

0

5 4.43

< mdl

0

–

< mdl

< mdl

0 .02

< mdl

.646

005

00.40

0.00 8

1 .698

0. 822

3

.011

821

0.50

0

0.

1 00.60

1

0.

1

0.49

.61

828

465

0.52

1

0.

0.

6 1

0.

9

0.49

.66

81

9.14

1

0.

9

0.50 3

.656

84

8.28 –

.01

< mdl

mdl

.01

mdl

9.79

5

.648

821

0.49

1

0.

9

<

0

<

5 4.50

<

0 .01

0

1

0.

9

0.49 4

.660

828

9.23

.01

mdl –

2.76

mdl

.04

mdl

9.36

4

.660

822

0.49

1

0.

9

<

0

<

5

0

0

0 .10

.02

.02

.02

1.68

mdl

.652

819

9.30

0 1

0.

9

<

0

0

5

0

0

<

0 .01

0

<

5

<

0

0.

9

<

.652

816

9.15

mdl

.04

mdl

3.28

mdl

.01

5

0

<

<

9

<

0

826

8.77

mdl

.03

mdl

3.09

.14

mdl –

.01

.14

.06

mdl

2.82

mdl

mdl

.01

9.23 <

<

0

5

0

0

<

0

0

<

0 .05

6.23

.02

.02

md

.05

mdl

.01

3.21

mdl <

0

5

0

0

0

<

4

0

mdl

.05

5.48

.01

.02

3.21

mdl

mdl 0

5

<

0

<

0

4

0

0

.01

6.88

mdl

mdl

2.95

.03

.02

.01 5

0

0

<

0

4

<

0

L-4B-

5.86

.08

.03

.05

.02

.01

mdl

2.95 0

0

<

0

4

0

0

L-4B-

6.24

.03

.02

mdl

.03 0

0

<

4

0

mdl

mdl

5.92

.01 <

<

4

0

0

.03

5.75

.04

mdl 0

4

0

0

lzs-3-

5.55

.06

.07

.04 4

0

0

lzs-3-

12

.08

.06

2-12

6.14 0

0

lzs-3-

y-3

.02

0.48 4

1 .700

0.48 4

L-4B13

0 .06

L-4B14

mdl 0

.06 L-4B-

15

L-4B-

0

L-4B23

0 .05

L-4B24

L-4B-

0

Max

Min Ave.

0

0 .07

0 .22

0 .04

4

<

4

0

<

0

0

<

<

<

–

–

0

<

0 .02

< mdl

–

00.17

00.60 <

mdl 0

8.71 –

1

6

.653 1

0.

1

0.

0.49 3

.70 1 .65 0.

0.50 9

.676

81

0.50

1

0.

9

9

.650

84

0.50

1

0.

1

8

.657

826

0.48

1

0.

1

4

.689

842

0.49

1

0.

1

<

1

0.

844

0.48 6

.646

834

00.26

mdl

.03

mdl 5

0

0

5

<

9

.695

823

0.48

1

0.

9 9.75

mdl

.01

.01

2.78

0

<

5

<

7

.689

824

0.48

1

0.

1 00.38

mdl

.01

mdl

4.50

mdl

<

5

0

<

826

1

0

.692

814

00.21

.02

mdl

mdl

3.72

.03

mdl 0

<

<

<

5

<

1

0.

9 8.71

mdl

mdl

mdl

3.01

mdl

.01

mdl

<

<

<

5

0

<

824

1 00.43

.01

mdl

mdl

2.89

mdl

mdl

.31

mdl 4

<

0

<

<

<

5

<

<

0.

1 00.40

mdl

mdl

mdl

3.12

mdl

mdl

mdl

.04

5.45 0

0

<

<

0

5

<

<

<

1 00.40

mdl

mdl

mdl

4.14

mdl

mdl

.14

.01

7.12

mdl 0

4

<

0

<

<

<

<

5

< mdl

mdl

mdl

2.78

mdl

mdl

.21

mdl

6.15

0

<

4

<

0

5

<

0 .03

.01

4.34

mdl

mdl

.01

mdl

7.01

.22

<

4

0

<

5

<

<

< mdl

4.15

mdl

mdl

mdl

mdl

6.58

.02

.05

4

0

0

0

0

<

0

5 4.26

.01

mdl

.31

.01

7.12

.03

.06

26

0

0

L-4B-

4

<

<

0

< mdl

mdl

mdl

.03

5.98

.06

.04

25

<

<

<

4

0 .01

mdl

mdl

5.45

mdl

0

4

0

< mdl

.04

6.02

.07

.07

4

<

0

0 .02

6.14

mdl

.05

21

<

0

L-4B-

4 6.02

mdl

.06

16

<

1

0.51

0.48 0.49

.06 S.D.

0 .01

LZS5-1

5-8

.07

5-9

mdl

.05 LZS-

5-11

mdl 0

.05 LZS-

5-14

0

L-8A

1-7

0

L-8A .06 L-8B-

<

4

<

4

<

<

0

<

0 .01

<

<

< mdl

<

<

0

<

0

<

00.40 <

mdl <

9.20 <

1

0. 845

0.50 5

1 .656

0.

0.51 0

1 .660

0.

0.49 2

.674

822 1

7

.690

845

0.50

1

0.

9

6

.672

831

0.49

1

0.

1

1

.686

848

0.50

1

0.

1 00.95

.01

mdl 0

<

4

.695

837

0.50

1

0.

1 00.68

mdl

.01

mdl 5

0

<

5

<

8

.684

848

0.49

1

0.

1 01.03

mdl

.01

mdl

3.23

0

<

5

<

0

.685

848

0.01

1

0.

1 01.00

mdl

.01

mdl

3.09

<

<

5

<

.021

840

1 01.82

mdl

mdl

mdl

3.68

mdl

mdl <

<

<

<

5

<

3 0

0.

1 01.40

mdl

mdl

mdl

4.18

mdl

mdl

5

<

<

mdl

3.60

mdl

mdl

mdl

mdl

<

<

0

< mdl

mdl

mdl

.02

5.91

<

<

4

0

4.05

.01

009

01.00

mdl

.677 0.

1

<

0

<

526

mdl

827

0.

<

<

<

5

.01

mdl

mdl

0

<

<

5

<

.01

mdl

mdl

4.34

mdl

.01

mdl

mdl

7.21

mdl 0

4

<

0

0

<

0

<

5

00.16 0

< mdl

3.98

mdl

.01

mdl

.01

7.21

mdl

<

4

<

.13

mdl

6.42

mdl

.06

1-10

<

0

L-8A

4

0

5 4.03

mdl

mdl

–

.68

<

<

.01 0

0

<

<

0

.01

.01

mdl

mdl

.02

7.37

mdl

.04

4

<

<

0

0

< mdl

mdl

.03

6.74

mdl

.06

1-4

<

mdl

.01

7.38

<

0

4

–

.11

.02

7.35

3.76 0

0

4

<

0

.01

6.89

.01

.07 0

4

0

0

LZS-

.50

mdl

.05

.01 0

<

0

LZS-

y-4

.07

.06

5-6

6.21 0

0

LZS-

P

.04

0.49 5

1

0.50

2

.06 L-8B-

6

mdl 0

.05 L-8B-

7

mdl

.06

4 L-8C-

0

LZK6-1-1 Max

Min

Ave.

S.D.

<

0 .05

< mdl

0 .07

.05 0 .01

–

4

0

0 .55

0

0 .01

.01 0 .01

<

– –

0

5

5

0

<

01.82 <

mdl –

8.52 –

3.47 0 .64

–

–

–

915

1

0.52

1

0.49

.63

840

1 .668

0.

0.50 4

0 .020

Notes:
5

.69

0.

010

0.49

1

0.

0.

0.52 0

.648

82

00.49

4

.629

0.

1

0.51

1

0.

9

8

.634

85

0.50

1

0.

1

5

.662

816

0.50

1

0.

9

0

<

845

848

8.52

.01

mdl –

0

1

0.

9

8

.681

841

9.66

.01

.01

mdl

<

<

849

9 9.47

mdl

mdl

.01

2.24

<

<

5

<

.658 0.

1 00.56

mdl

mdl

mdl

4.34

mdl 0

0 .03

0

<

<

5

<

<

842

1 01.34

mdl

mdl

mdl

2.85

.01

mdl

.01

<

0

<

5

<

0

<

00.28

mdl

.01

mdl

2.24

mdl

.02

mdl

.01

0

0

<

<

<

<

5

mdl

mdl

mdl

2.40

mdl

.01

.13

mdl

6.93

<

0

4

0

<

5

0

mdl

mdl

3.29

.01

.02

mdl

.03

5.60 –

<

4

<

<

5

<

0

.01

3.89

mdl

.02

mdl

mdl

7.39

mdl 0

4

0

0

<

<

0

<

3.14

mdl

.01

mdl

mdl

5.60

.01

.04

4

<

<

0

mdl

mdl

mdl

.03

7.36

<

0

4

mdl

mdl

.02

6.96

mdl

0

4

<

mdl

.01

7.17

mdl

.04

4

<

0

.03

7.39

mdl

.05

10

<

0

L-8C-

7.05

0.00 8

lzs–3–2–4 to

Table 5. Compositions of the marcasite in Laozuoshan gold deposit (Data from EPMA, wt.%) S tage

Sam ple

C o

L-7 D-7

0

L-4

B-22

.05

B-5

mdl

.07 LZS

M -5-2

.01 0

.05 LZS

-5-3

-5-12

-5-13

A1-2

.01

.05

mdl 0

.04

6.17

6.60 <

mdl

.02

.02 4

6.06

mdl

0 .01

.01

4.14

mdl

2.54 <

mdl

4.18

.02

mdl

00.43

mdl

9.23 <

mdl

1

0.49 9

1

0.8

0.49 0

1 .689

0.8

0.49 0

1 .639

0.8 25

0

.693

27

0.50

1

0.8 30

0.49 0

.687

34

00.39

8

.690

42

0.48

1

0.8

1

9

.684

45

0.45

1

0.8

9

5

.679

25

0.49

1

0.8

1

<

< mdl

00.74

1

.689

19

1

0

<

0 .02

.01

.01

.01

01.18

S (at.%)

0.8

1

0

0

0

5

mdl

mdl

mdl

01.49

(at.%)

.680

75

1

<

<

<

5

mdl

mdl

.01

00.76

Fe/

0.7

1

<

<

0

5

<

< mdl

4.29

mdl

mdl

mdl

00.19

mdl

32

1

<

<

<

5

<

0

0 .08

mdl

.01

.01

4.07

.01

mdl

mdl

01.08

S

0.8

1

0

<

<

5

<

0

0

4.18

mdl

mdl

.01

00.79

mdl

.01

1

<

0

0

5

<

<

<

0

mdl

mdl

mdl

4.00 <

<

<

0

4

mdl

mdl

.02

mdl

.02

(at.%)

otal

mdl

Fe

T

<

0

<

5

e

mdl

mdl

S

<

0

5

<

<

<

0

4

<

.08

mdl

6.38

.07

<

.02

3.83

C d

mdl

4.15

mdl

g

5

<

0

0

<

4

0

0

L-8 A1-11

mdl

.07

mdl

7.04

.31

.57

3.86

mdl

A

5

<

0

0

<

4

<

0

L-8

7.17

mdl

.05

mdl

mdl

mdl

.25 <

4

<

0

LZS

6.05

mdl

.06

mdl

<

<

0

S

n

.06

.58

Z

0

3

<

4

<

0

LZS

5.74

u

.31

mdl

C

0

<

4

0

i

.04

3.27

N

0

4

<

0

u

6.46

mdl

A

4

<

0

L-4

e

mdl

.04

F

<

0

L-4

c

s

.06

B-20

A

0.50 9

1 .690

0.48 8

L-8 B-8

0 .04

Max

Min

Ave.

S.D.

< mdl

0 .07

0

0

.05 0

4

<

–

0

4

.01

.44

.01

.04

.06

0 .09

5

<

–

0

5

00.48

.02

mdl

< mdl

–

9.23 –

0 .01

.661

4

Notes:
0.51

1

0.46

.64 0.8

27

1 .680

0.0 19

8 1

0.7

0.

0.50

.69

7

598

1

0.8

1

0 .01

44

9

00.61 0

0.8

1 01.49

.01

.01

1

0

<

0

0 .52

0

<

5

< mdl

.02

mdl

3.86

< mdl

.02

2.54 –

< mdl

4.29

mdl 0

1

3.26

mdl

mdl

5

<

<

0

0

mdl

.31

mdl

<

0

<

0

1 .08

3

<

4

0 .01

.58

mdl

6.19

< mdl

.04

3.27 –

0 .02

7.17

mdl 0

.01

7.13

.01

.04

4

0.49 2

0 .016

0.01 4

Table 6. Compositions of the chlorite in the Laozuoshan gold deposit, the Dewulu skarn deposit and the Hatu gold district (Data from EPMA, wt.%) Sta ge

N

LZ

LZ

LZ

LZ

LZ

S-3-Chl

S-3-Chl

S-3-Chl

S-3-Chl

S-3-Chl

S-3-Chl

3

9

2

3

l1

l2

3

2

3

4

5

6

7

8

2

2 4.79

0

1.97

.11 9

.82 Ca

.01

mdl

mdl

.03

mdl

.03

mdl

02

mdl

21

06

13

08

mdl

02

1

mdl

mdl

mdl

mdl

1 0.0

1

mdl

< mdl

< mdl

< mdl

04

mdl

1

12.

<

0.0

<

7

35

mdl

0.2

14.

<

0.0

59

5

66

28.

0.3

12.

<

<

0.0 1

31

05

07

6

20.

26.

0.2

14.

<

<

< mdl

47

mdl

1

1

6

93

04

0.0

19.

28.

0.3

14.

<

0.0

0.0

3

45

mdl

73

60

1

89

25.

0.0

19.

26.

0.3

14.

<

<

0.

3

70

1

45

73

5

53

25.

0.0

19.

27.

0.3

12.

0.0

0.

0.

9

42

07

16

34

3

55

25.

0.0

19.

27.

0.2

12.

0.

0.

0.

7

02

06

26

80

7

54

24.

0.0

19.

29.

0.2

5.

0.

0.

<

mdl

96

33

83

56

7

43

25.

0.0

19.

29.

<

6.

0.

0

<

02

48

mdl

.54

56

6

77

25.

0.0

18.

35

0.

6.

<

0

<

05

.62

.05

5.09

85

6

.87

24.

0.0

22

3

0.

9

0

<

<

.06

.59

.02

6.61

00

07

9.72

24.

0.

1

3

0

9

0

0

K2

.09

.22

.02

0.86

.21

mdl

7.58

1 26

<

1

3

0

9

0

Na

1.80

4.56

07

0.88

2

0.

2

3

0

5.84

mdl

1.04

2

<

2

3

0

4.56

.05

0.33

2

0

2

3

M

4.67

.04

.10

2

0

2

M

O

LZ

S-3-Chl

1.29

2O

LZ

-III-Chl S-3-Chl

Fe

O

LZ

atu-Ch

0.44

gO

Qi

atu-Ch

Al

nO

H

B27-

.04

O

H

B27-

Ti

2O3

N

B14-

4.98

O2

N

B14-

Si O2

N

< mdl

< mdl

< mdl

To tal

8 6.70

8 6.48

8 7.32

8 6.01

8 7.04

8 6.70

89 .93

85. 38

86. 60

87. 12

87. 43

85. 72

86. 25

86. 45

86. 61

Number of ion on the basis of 28 atoms of cations Si

Ti

Al

Fe

5 .488

.485 0

.007

.749

.916

.019

g

.021 3

.216 Ca

Na

K

.009

.000

.000

.025

.000 0

.000 0

.660

.026

.000 0

.650

017

035 0

.643

183

046 0.

760

107

011 0.

739

00

05 0.

799

80

00

04

04

04

00 0.5

18

15

0.0 00

0.0 00

0.5 54

00

00

02

0.0

0.0

0.0

0.5

86

00

08

3.8

0.0

0.0

0.0

50

79

00

0.0

4.5

0.0

0.0

0.0

0.5 14

01

78

64

07

5.1

0.0

4.1

0.0

0.0

0.0

0.5 66

01

00

02

52

35

66

48

5.1

4.6

0.0

4.6

0.0

0.0

0.0

0.5

18

01

05

57

09

43

02

0.0

5.0

5.1

0.0

4.6

0.0

0.0

0.0

59

25

00

35

45

02

11

5.5

0.0

5.1

4.9

0.0

4.6

0.0

0.0

0.

60

41

01

54

07

07

31

5.5

0.0

5.0

4.9

0.0

4.1

0.0

0.

0.

54

27

016

01

13

05

39

5.5

0.0

4.9

4.9

0.0

4.1

0.

0.

0.

51

591

014

92

06

10

47

5.4

0.0

4.9

5.3

0.0

1.

0.

0.

0

000

333

008

97

73

10

18

5.4

0.0

5.0

5.6

0.

2.

0.

0

0

004

180

.000

319

88

10

57

5.4

0.0

4.9

6.

0.

2.

0

0

0

010

.170

.012

598

37

10

789

5.4

0.0

5.

6.

0.

3

0

0

0

.011

.127

.005

908

51

011

247

5.3

0.

5.

6.

0

3

0

0

(Fe+Mg .641

.017

.041

.005

.705

573

000

694

5.

0.

4.

5

0

3

0

Fe/

.818

522

012

.458

5.

0.

5

5

0

830

.000

.439

5.

0

5

5

0

.429

.008

.317

5

0

5

5

M

.397

.007

.308

5

0

5

M n

5

0.0 00

0.5 05

0.5 71

) Notes:
Table 7. The gold deposits in Jiamusi massif. O Name of deposit

Eco

re

Or

nomic

deposi

mineral

t

Genetic type

ebody shape

Mineralo genetic epoch

Ref erence

Scale Laozuo shan

gold

Au

deposit

L arge

Irr Hydrothermal type

egular shape

Dongfe Au，

M iddle

Fe

Sedimentary-Meta morphic

deposit

gold deposit

Au

S mall

Jizhuag

deposit

0 1

et

al.,

2014

dded

Variscan

ore

Nan , 2018

body

Xinli

ou

+ Yanshanian

Li

Be

ngshan Fe-Au

Variscan

gold

Au

Hydrothermal type

Zha

ined

Variscan

shape

S mall

Ve

2016 He

Irr Hydrothermal type

egular shape

ng et al,.

Yanshani an

and Zhao, 2002

2 3 4

5 6 7

8 9

10 11

12 13

14 15 16

17 18

19

20 21

22 23

24 25

26

27 28

29 30

31

32 33

34 35

36 37

38

39 40

Highlights

41 42

1. The Laozuoshan gold deposit is a reduced gold skarn deposit.

43 44

2. The mineralogical and compositional evolution of the sulfides in the Laozuoshan gold deposit

45

constrain the physicochemical conditions of multi-stage ore-forming fluids.

46 47

3. Assemblage and chemical composition of sulfides reveal the gold mineralization occurred under

48

low fO2 and low fS2 conditions.

49 50

4. The pyrrhotite replaced by marcasite and pyrite through dissolution-reprecipitation indicates the

51

fluids changed from the weakly acidic and weakly reducing to more neutral and weakly oxidizing.

52

53