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The Baiyun gold deposit is a medium-sized deposit in northeastern Hubei around the southern margin of the Tongbai-Dabie metallogenic belt. However, its genesis has not been determined. The metallogenic process of the Baiyun gold deposit can be divided into three stages: quartz + feldspar, quartz + native gold + electrum + polymetallic sulfides, and quartz + pyrite + calcite + iron dolomite + illite. In this study, LA-ICP-MS was used for in situ trace element and isotope analyses in the main and late ore stage hydrothermal sulfides to evaluate the genesis and evolution of ore-forming fluids. Gold is positively correlated with Ag, Cu, Pb, Zn, and Te and the Co/Ni ratio is greater than 1. The S isotope values of Py1 and Py2 are −0.23–3.04‰ and 1.27–6.09‰, respectively. As mineralization progressed, S isotope values increased. In situ S isotope values of the two types of galena symbiotic with pyrite in the main metallogenic stage are 2.97–3.47‰. In situ Fe isotopic values of pyrite are −0.05–0.82‰; values in the two stages are similar without significant fractionation. We inferred that the Baiyun gold deposit formed via magmatic mineralization related to the subduction of the Pacific Plate during the Yanshanian. [ABSTRACT FROM AUTHOR]

The Fang'an gold deposit in the Wuhe area, Anhui Province, is located in the area adjacent to the Bengbu Uplift and Wuhe Platform Depression in the southeastern part of North China. This study aimed to determine the deposit's mineralization age and the source of its metallogenic materials and mineralization processes through investigations into its geological characteristics, Rb–Sr isotopes, and S–Pb isotopes. The orebodies of the Fang'an gold deposit in the Neoarchean Xigudui Formation primarily exhibit a vein-type structure. The ore-forming process can be divided into four stages: (i) the quartz stage (Py1); (ii) the quartz–pyrite stage (Py2); (iii) the polymetallic sulfide stage (Py3); and (iv) the carbonate stage. Of these, the main mineralization stage is also the main period in which gold mineralization occurs. In situ sulfur isotope results of pyrite (Py1 to Py3) in the first three mineralization stages, suggesting a contribution of sulfur from crust–mantle magmatic fluids. The δ34S values for Py2 (average 5.51‰) are higher than Py1 (average 4.45‰) and showed that the magmatic fluids mixed with meteoric waters. The δ34S values for Py3 (average 5.18‰) are lower than Py2 (average 5.51‰), revealing that it related fluid immiscibility. The lead isotopic compositions of sulfides within the ores possessed 206Pb/204Pb ratios ranging from 16.759 to 16.93, 207Pb/204Pb ratios ranging from 15.311 to 15.402, and 208Pb/204Pb ratios ranging from 37.158 to 37.548. These lead data were plotted close to the Xigudui Formation, relatively distant from the Mesozoic granites, indicating that the Xigudui Formation was the source of lead for the Late Mesozoic ores of the deposit. Taken together, due to the degassing of mantle-derived magma in the shallow parts of the crust, it can be determined that the sources of ore-forming sulfur and lead were crust–mantle magmatic activities in the Wuhe area. Rb–Sr dating of pyrite from Fang'an gold deposit reveals that the mineralization occurred at 126.89 ± 0.58 Ma. Considering the previous research into the dating of magmatic rocks in the Wuhe area, we propose that the genesis of the Fang'an gold deposit is closely associated with magmatic activities in the area at around 130 Ma. [ABSTRACT FROM AUTHOR]

The Nanpanjiang basin hosts the world's second-largest concentration of Carlin-type gold deposits. To decipher the origin and evolution of hydrothermal fluid, this study conducted Sm–Nd dating, in-situ trace element, and C-O-Sr isotopic analyses on three types of calcite samples from the giant Lannigou gold deposit in the Nanpanjiang basin, SW China. The type-I calcite, intergrown with Au-bearing arsenian pyrite, has an Sm–Nd isochron age of 213 ± 7 Ma (MSWD = 0.81), indicating that gold mineralization occurred in Late Triassic. The type-II calcite, which coexists with high-maturity bitumens and cut through the main-stage gold orebodies, yields an Sm–Nd age of 188 ± 14 Ma (MSWD = 0.34), representing a post-ore hydrocarbon accumulation event. The type-I and type-II calcite samples have low REE contents (5.28–51.6 ppm) and exhibit MREE-enriched and LREE-/HREE-depleted patterns. Combined with their identical C-O-Sr isotopes, we suggest that hydrothermal fluids responsible for the precipitation of type-I and type-II calcite samples were derived from a mixed metamorphic fluid and meteoric water source. In contrast, the type-III calcite samples, associated with realgar and orpiment, have distinct Mn, Sr, and As contents, REE patterns, and C-O-Sr isotopic composition from the type-I and II calcites, suggestive of different fluid sources. Based on our and previously published data, we propose that the fluid evolution, gold mineralization, and hydrocarbon accumulation in the Nanpanjiang basin are closely related to the Indosinian and Yanshanian orogenies in South China. [ABSTRACT FROM AUTHOR]

The Daliuhang gold deposit in the Qipengfu (Qixia–Penglai–Fushan) ore concentration area is a typical gold deposit of medium-low temperature hydrothermal veins. Uncertainties regarding the primary sources of ore-forming fluids, as well as whether host rocks contribute materials to the mineralization of the gold deposits in the Jiaodong Peninsula, are still subject to intense debate. Hydrogen–oxygen isotope results show that atmospheric water is involved in ore-forming fluids. According to the results of the helium–argon isotopes of pyrite, it is hypothesized that the initial fluid source was located in the oceanic crust or upper mantle lithosphere above the Early Cretaceous Paleo-Pacific Plate, as it was subducted into the eastern part of the eastern North China Craton. In situ sulfur isotope results show that high δ34S values characterize the pyrite in the main mineralization period. It is inferred that during the thinning and melting process of the lithospheric mantle, the volatile components enriched in pyrite contributed to the release of δ34S. At the same time, when the fluids ascended to the weak zones, such as fissures of ore-endowed peripheral rocks, the δ34S in the peripheral rocks were extracted, and the two processes acted together to cause high δ34S values to occur. Similarly, the lead and strontium isotopic compositions indicate a crust–mantle mixing attribute of the mineralized material source. The zircon U–Pb age of the ore-hosting granodiorite was 130.35 ± 0.55 Ma, and the Rb–Sr isochron age of the pyrite from the main mineralization period was 117.60 ± 0.10 Ma, which represents the timing of felsic magmatism and gold mineralization, respectively, with at least 10 Ma between the magmatism and mineralization. The magma gradually cooled over time after its formation, and when the granodiorite cooled down to 300 ± 50 °C, the temperature and pressure conditions were most conducive to the precipitation of gold. It is inferred that gold-rich initial mantle fluids with volatile components, rising along tectonically weak zones, such as fractures, underwent fluid phase separation in the fractured position of the granite and extracted the gold from the granodiorite, forming gold deposits. [ABSTRACT FROM AUTHOR]

The Tuwaishan gold deposit is located at the northeastern end of the Gezhen shear zone in the western part of Hainan Island, South China. It is one of a series of similar gold deposits hosted in the Mesoproterozoic basement rocks and structurally controlled by the Gezhen shear zone. The hydrothermal ore-forming period can be divided into quartz-pyrite-arsenopyrite stage, quartz-pyrite-base metal sulfides stage and quartz-carbonate stage. Eleven gold-bearing quartz vein samples yield δDV-SMOW and δ18OV-SMOW values of −75.9‰ to −54.4‰ and +8.1‰ to +13.7‰, respectively, and the corresponding δ18Owater values range from +3.1‰ to +8.7‰. In addition, the pyrite separates from 14 ore samples yield δ34S values of +4.5‰ to +7.9‰. The H-O-S isotopic data, along with fluid properties of the Tuwaishan and other gold deposits along the Gezhen shear zone, suggest that the ore-forming fluid and materials are of metamorphic rather than magmatic origin. Hence, we propose that the Tuwaishan gold deposit is best classified as orogenic gold deposit that resulted from regional metamorphism. Considering that the Mesoproterozoic basement rocks have experienced amphibolite facies metamorphism prior to the gold mineralization, the metamorphic devolatilization of the Ordovician-Silurian rocks at depth would provide a realistic source of fluid, gold and sulfur for the Tuwaishan and other gold deposits of the Gezhen gold belt. [ABSTRACT FROM AUTHOR]

A Paleoproterozoic 40Ar/39Ar age, interpreted as the gold metallogenic epoch of the Lijiapuzi deposit in NE China, is reported in this paper. The ore body of this deposit is hosted in the marbles and schists of the Paleoproterozoic Dashiqiao Formation and exhibits parallel development to the foliation of the country rocks. Coexisting auriferous pyrite and tremolite can be observed both in the field and under a microscope, revealing the presence of hydrothermal activity in the deposit. The δ34S composition of the auriferous pyrite varies from +8‰ to +12.3‰, indicating a sedimentary origin. The auriferous pyrite and host marble have similar Pb isotopic ratios, indicating the contribution of Paleoproterozoic sediments to gold mineralization. Furthermore, in situ S and trace element analyses of the auriferous pyrite reveal that the main gold mineralization stage was Py2, which coexists with radial tremolite. 40Ar/39Ar dating of these tremolite samples yields a plateau age of ~1851.23 Ma, with similar isochronal and inverse isochronal ages. The Paleoproterozoic gold metallogenesis, together with the contemporary Pb-Zn, boron, graphite, and magnetite mineralization, constitute an important mineralogenetic series during the evolution of the Jiao-Liao-Ji orogeny in the Liaodong Peninsula. [ABSTRACT FROM AUTHOR]

The Toudaochuan gold deposit is a recently discovered lode gold deposit in Central Jilin Province. Gold ore bodies are dominantly controlled by NE-trending fault. The major hydrothermal period can be further divided into the quartz–pyrite stage (stage I), quartz–gold–polymetallic sulfides stage (stage II, major gold mineralization stage), and quartz–carbonate stage (stage III). Primary fluid inclusions (FIs) identified in quartz at different hydrothermal stages include liquid-rich aqueous FIs (L-type), CO2 FIs (C-type, including CO2-bearing C1-type FIs and CO2-rich C2-type FIs), and minor vapor-rich aqueous FIs (V-type). Microthermometry studies on different fluid inclusions indicate that the original ore-forming fluids belonged to the CO2–H2O–NaCl system characterized by a moderate–low temperature and low salinity in stages I and II, and they finally evolved into a H2O–NaCl system characterized by low temperature and low salinity in stage III. Fluid immiscibility is considered to be the key ore-forming mechanism. The initial ore-forming fluid was originated from magmatic water and was mixed with meteoric water in the later stage. The S and Pb isotope data suggest that the ore metal materials were derived from the mixed source of mantle and crust. Based on all the above data, therefore, it can be proposed that the Toudaochuan gold deposit is a mesothermal magmatic–hydrothermal gold deposit. [ABSTRACT FROM AUTHOR]

The Harla gold deposit is located on the eastern segment of the Kanggur-Huangshan ductile shear belt in Eastern Tianshan, on the southern margin of the Central Asian Orogenic Belt. The orebodies show close spatial association with NEE-trending faults and are hosted in volcanic rocks of the Lower Carboniferous Xiaorequanzi Formation. Three mineralization stages were recognized: an early stage characterized by specularite–pyrite–quartz mineralization, an intermediate stage with pyrite–chalcopyrite–gold–quartz genesis, and a late stage defined by sulfide-poor calcite and quartz veins. Three types of fluid inclusions (FIs) were recognized: daughter mineral-bearing triphase FIs (S-type), liquid-dominated biphase FIs (LV-type), and liquid-only monophase FIs (L-type). S- and LV-type FIs entrapped in the early stage show similar homogenization temperatures (Th) at 216–229 °C and 199–222 °C. However, they display contrasting salinities of 32.2–33.4 and 6.7–8.9 wt.% NaCl eqv., respectively. LV-type FIs entrapped in the intermediate stage display Th of 163–191 °C, with salinities of 5.6–7.4 wt.% NaCl eqv. LV-type FIs occur in the late stage display Th of 135–258 °C and salinities of 3.7–5.6 wt.% NaCl eqv. Insights from hydrogen, oxygen, and carbon isotope analyses (δ18OH2O = −10.7 to 3.3‰, δDH2O = −88.1 to −61.4‰, δ13CH2O = −8.9 to −6.2‰), combined with FI characteristics, indicate that the ore-forming fluids were derived from a hybrid source of magmatic and meteoric water, with the latter becoming dominant in the later stage. Sulfide and lead isotopic compositions (δ34Spyrite = 0.2 to 2.5‰, 206Pb/204Pb = 17.709–18.273, 207Pb/204Pb = 15.483–15.569, 208Pb/204Pb = 37.533–37.754) suggest that ore-forming materials were mainly derived from wall rocks (Xiaorequanzi Formation rocks and plagiogranite). By integrating geological background work and fluid inclusion analyses, as well as isotope data, we conclude that the Harla gold deposit is an epithermal-type deposit. [ABSTRACT FROM AUTHOR]

The Koka gold deposit is located in the Elababu shear zone between the Nakfa terrane and the Adobha Abiy terrane, NW Eritrea. Based on a paragenetic study, two main stages of gold mineralization were identified in the Koka gold deposit: (1) an early stage of pyrite–chalcopyrite–sphalerite–galena–gold–quartz vein; and (2) a second stage of pyrite–quartz veins. NaCl-aqueous inclusions, CO2-rich inclusions, and three-phase CO2–H2O inclusions occur in the quartz veins at Koka. The ore-bearing quartz veins formed at 268 °C from NaCl–CO2–H2O(–CH4) fluids averaging 5 wt% NaCl eq. The ore-forming mechanisms include fluid immiscibility during stage I, and mixing with meteoric water during stage II. Oxygen, hydrogen, and carbon isotopes suggest that the ore-forming fluids originated as mixtures of metamorphic water and magmatic water, whereas the sulfur isotope suggests an igneous origin. The features of geology and ore-forming fluid at the Koka deposit are similar to those of orogenic gold deposits, suggesting that the Koka deposit might be an orogenic gold deposit related to granite. [ABSTRACT FROM AUTHOR]

The Jinchang gold deposit is located in the eastern Yanji–Dongning Metallogenic Belt in Northeast China. The orebodies of the deposit are hosted within granite, diorite, and granodiorite, and are associated with gold-mineralized breccia pipes, disseminated gold in ores, and fault-controlled gold-bearing veins. Three paragenetic stages were identified: (1) early quartz–pyrite–arsenopyrite (stage 1); (2) quartz–pyrite–chalcopyrite (stage 2); and (3) late quartz–pyrite–galena–sphalerite (stage 3). Gold is hosted predominantly within pyrite. Pyrite separated from quartz–pyrite–arsenopyrite cement within the breccia-hosted ores (Py1) yield a Re–Os isochron age of 102.9 ± 2.7 Ma (MSWD = 0.17). Pyrite crystals from the quartz–pyrite–chalcopyrite veinlets (Py2) yield a Re–Os isochron age of 102.0 ± 3.4 Ma (MSWD = 0.2). Pyrite separated from quartz–pyrite–galena–sphalerite veins (Py3) yield a Re–Os isochron age of 100.9 ± 3.1 Ma (MSWD = 0.019). Re–Os isotopic analyses of the three types of auriferous pyrite suggest that gold mineralization in the Jinchang Deposit occurred at 105.6–97.8 Ma (includes uncertainty). The initial 187Os/188Os values of the pyrites range between 0.04 and 0.60, suggesting that Os in the pyrite crystals was derived from both crust and mantle sources. [ABSTRACT FROM AUTHOR]