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The study of the fluid inclusions of W–Mo deposits in the mineralization area of Ningshan–Zhen'an , Shaanxi Province, China shows that the gas–liquid two-phase inclusions are mainly present in W–Mo deposits, and the ore-forming fluid can be divided into four types: high-temperature type, middle–high-temperature type, middle-temperature type and low-temperature type. The formation depths of the W–Mo mineralization range from 4.2 to 8.4 km. The boiling and mixing of fluid may have been important mechanisms for the formation of W–Mo mineralization. The skarn-type mineralization is dominated by magmatic water, the quartz-vein-type mineralization includes both magmatic water and meteoric water, and the meteoric water is more involved in the quartz-fluorite-vein-type, beryl-quartz-vein-type and pegmatite-type mineralization. Magma is the main source of sulfur; that is, magma is the main source of mineralization. Combined with the metallogenic setting and geological characteristics of typical ore deposits, in the process of structural system transformation in South Qinling, the ore-forming magma fluid in the Late Indosinian–Yanshanian period was uplifted and emplaced along the NW–WNW direction and NE–NNE direction, and eventually, NW–WNW fault-controlled skarn-type W–Mo mineralization and quartz-vein-type W–Mo deposits accompanied by greisenization, albitization and potash feldspathization formed. [ABSTRACT FROM AUTHOR]

Jinchanghe is a Zn-Pb-Fe-Cu skarn deposit in the northern Baoshan block, southwestern China. It is a typical distal skarn deposit with orebodies in the Cambrian Hetaoping Formation limestone and calcareous siltstone. The skarn minerals display a vertical zonation with garnet skarn in the lower part and pyroxene skarn in the upper part. Economic metals are also zoned with Fe at the base, Cu in the middle, and Zn-Pb in the upper part. The skarn formation and Zn-Pb-Fe-Cu mineralization is divided into four paragenetic stages: a pre-ore stage dominated by prograde garnet and pyroxene, an oxide stage represented by Fe mineralization associated with retrograde ilvaite, actinolite and epidote alteration, a sulfide stage characterized with Cu–Zn-Pb sulfides, and a post-ore stage with barren calcite, quartz and chlorite. Fluid inclusion microthermometry indicates that the hydrothermal fluids of the Jinchanghe skarn system evolved from the pre-ore stage (450–480 °C and 11.7–15.5 °C wt% NaCl equiv), through the oxide stage (230–280 °C and 6.5–12.2 wt% NaCl equiv), the sulfide stage (190–230 °C and 1.3–10.3 wt% NaCl equiv), and eventually to the post-ore stage (120–180 °C and 1.6–4.6 wt% NaCl equiv). Correspondingly, the δ18Ofluid values decrease from 1.8–7.1‰ to 1.0–6.4‰, -1.0 to 1.3‰, and -3.6 to -1.4‰. This indicates that the pre-ore fluids comprise a magmatic component but mixed with some meteoric water, and in the later stages meteoric water has become dominant in the hydrothermal system. Zinc and sulfur isotope compositions reveal that the Zn and S forming the sulfides have a dominantly magmatic origin. The coupled decreases of fluid temperature, salinity, and δ18Ofluid values during the mineralization indicate simultaneous mixing with meteoric water and ore precipitation, suggesting that fluid mixing was critical in ore deposition. The gradual increase of δ13CCO2 values in equilibrium with the hydrothermal calcite (-5.2 to -1.6‰) from the sulfide stage to the post-ore is attributed to the reaction between the fluids and the carbonate wallrocks, implying a role that fluid-rock interaction has taken in the sulfide deposition. Fluid mixing and fluid-carbonate reaction are the two major factors controlling the formation of the Jinchanghe deposit. [ABSTRACT FROM AUTHOR]

The Yueguang gold deposit is located in Fengjia, Xinhua County, Hunan Province, South China. It represents a recently discovered small-scale gold deposit situated in the southwestern region of the Jiangnan Orogenic Belt, west of the Baimashan granitic batholith. In order to discern the characteristics of the ore-forming fluids, the underlying mineralization processes, and establish a foundation for the origin of the Yueguang gold deposit fluid inclusion microthermometry, as well as quartz hydrogen and oxygen isotope analysis, have been carried out on samples obtained from various stages of mineralization. The hydrothermal mineralization stages within the Yueguang gold deposit can be categorized into three stages: (i) the barren, pre-ore quartz-pyrite stage (Stage I), the quartz-pyrite-gold stage (Stage II), and the post-ore quartz-carbonate stage (Stage III), with the second stage being the main mineralization stage. The fluid inclusions identified in samples from the main mineralization stage can predominantly be described with the NaCl–H2O and CO2–NaCl–H2O systems. These inclusions display homogenization temperatures ranging from 158.8 to 334.9 °C, and the fluid salinity ranges from 0.3% to 4.0% (wt.% NaCl equiv.). Laser Raman spectroscopy analysis of individual inclusions further reveals the presence of gas-phases such as CO2, CH4, and N2. Isotopic analysis indicates δ18O fluid values ranging from 3.95 to 6.7 ‰ and δDH2O values ranging from − 71.9 to − 55.7 ‰. These results indicate that the ore-forming fluid of the Yueguang gold deposit belongs to metamorphic hydrothermal fluids of middle-low temperature and low salinity. In the process of ore formation, gold is transported in the form of Au (HS)2− complexes, with gold deposition being driven by fluid immiscibility. Therefore, the Yueguang gold deposit is categorized as an orogenic gold deposit dominated by metamorphic hydrothermal fluid. It may become a new target for gold exploration in the Baimashan region, central Hunan Province. [ABSTRACT FROM AUTHOR]

Carlin-type gold deposits are among the most important gold-bearing hydrothermal ore systems and are mainly located in Nevada, USA, and southwestern China. However, the source and evolution of the ore-forming fluids for these deposits remain controversial, especially those found within China. In this study, lithium and oxygen isotopic analyses of quartz-hosted fluid inclusions are used to elucidate the source and evolution of the giant Shuiyindong Carlin-type gold deposit. Fluid inclusions trapped in quartz of three distinct genetic stages have low salinity (0.8–6.3wt% NaCl equiv.) and moderate temperature (154–343 °C), but display variable Li and O isotope signatures. The Li and O isotopes of stage I fluids (δ7Li values from + 5.1 to + 9.1‰; δ18O values from + 6.3 to + 10.0‰) indicate predominantly a magmatic source for the initial ore-forming fluids. The large variations of Li and O isotopes of stage II fluids (δ7Li values from + 9.3 to + 16.0‰; δ18O values from + 0.1 to + 7.7‰) suggest that the fluids are controlled by mixing of magmatic fluids and meteoric water, which in turn triggered the precipitation of gold-bearing sulfides. The isotopic compositions of stage III fluids (δ7Li values from + 15.5 to + 22.8‰; δ18O values from − 5.4 to − 2.8‰) confirm that the final fluids are dominated by meteoric water. Furthermore, this work demonstrates that the combined Li–O isotopic analysis of fluid inclusions is a powerful tracer to decode the source and evolution of ore-forming fluids in hydrothermal mineralizing systems. [ABSTRACT FROM AUTHOR]

The formation of Carlin-type gold deposits is poorly constrained, mainly due to the lack of accurate ages for gold mineralization. The Youjiang basin, SW China, represents the world's second-largest Carlin-type gold province after NV, USA. In this paper, we use hydrothermal apatite U–Th–Pb dating to systemically determine the mineralization ages of five Carlin-type gold deposits, namely, Shuiyindong, Jinfeng, Zimudang, Linwang, and Jinya, in the Youjiang basin. The hydrothermal apatite is characterized by intimate intergrowth with gold-bearing sulfides, presence of primary fluid inclusions, irregular morphology and cathodoluminescence zoning, and MREE-enriched composition patterns, indicating that it is clearly associated and coeval with gold mineralization. The concentrations of lattice-bound U and Th in the apatite are highly variable, making it suitable for in situ secondary ion mass spectrometry (SIMS) U–Th–Pb dating. The dating results of hydrothermal apatite from the five deposits show that they formed at ca. 150–140 Ma, contemporary with the widespread felsic magmatism and associated W–Sn mineralization to the east of the Youjiang basin, probably in response to slab breakup of the Paleo-Pacific oceanic plate beneath the South China continental plate. Our case story suggests that hydrothermal apatite could be a robust chronometer for age dating of sedimentary rock-hosted gold mineralization worldwide. [ABSTRACT FROM AUTHOR]

The Gongguan deposit in southern Qinling district, central China, is characterized by a Hg and Sb metal association, with proven reserves of 7,543 t Hg and 17,100 t Sb. The Hg-Sb mineralized veins are primarily hosted by local Lower Devonian dolomite. Three primary paragenetic stages have been identified, including (I) pyrite-dolomite-quartz, (II) stibnite-cinnabar-quartz-calcite and (III) post-ore calcite. Dominant mercury and antimony mineralization occurred in stage II. Fluid inclusion microthermometry of quartz and calcite reveal that the Hg-Sb mineralization is associated with a low temperature (142° to 240 °C) and low salinity (< 8.6 wt% NaCl equivalent) fluid, belonging to a H2O-NaCl ± CO2 system. The H–O isotope compositions (δDH2O = −84 to −63‰, δ18OH2O = 1.3 to 12.7‰) of the hydrothermal fluid suggest a mixture of metamorphic fluid and meteoric water. In situ sulfur isotope results of cinnabar (δ34S = 3.4 to 14.5‰), stibnite (δ34S = 4.9 to 10.5‰) and pyrite (δ34S = 3.8 to 5.4‰) indicate sulfur sources from decomposition of diagenetic pyrite and/or the thermochemical sulfate reduction in local sedimentary rocks. In situ obtained 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios (18.006 to 18.362, 15.445 to 15.610 and 37.871 to 38.288, respectively) of stibnite and pyrite substantially differ from those for the regional Carlin Au-Sb and SEDEX Pb–Zn ore deposits. The lead isotope results indicate that the underlying Paleozoic (Silurian to Cambrian) strata and Precambrian metamorphic basement supplied substantial metals for the studied Hg-Sb deposit, whereas the host Devonian carbonates did not contribute significant metals. In summary, we propose that fluid mixing between metamorphic fluid and meteoric water was the main cause for carbonate-hosted Hg-Sb deposition at Gongguan, which reduced the stibnite solubility, oxidized mercury (Hg0 to Hg2+), favoring the process of dedolomitization. [ABSTRACT FROM AUTHOR]

The Jiajika granitic- and pegmatite-type lithium deposit, which is in the Songpan-Garze Orogenic Belt in western Sichuan Province, China, is the largest in Asia. Previous studies have examined the geochemistry and mineralogy of pegmatites and their parental source rocks to determine the genesis of the deposit. However, the evolution of magmatic-hydrothermal fluids has received limited attention. We analyzed He–Ar–H–O isotopes to decipher the ore-fluid nature and identify the contribution of fluids to mineralization in the late stage of crystallization differentiation. In the Jiajika ore field, two-mica granites, pegmatites (including common pegmatites and spodumene pegmatites), metasandstones, and schists are the dominant rock types exposed. Common pegmatites derived from early differentiation of the two-mica granitic magmas before they evolved into spodumene pegmatites during the late stage of the magmatic evolution. Common pegmatites have 3He/4He ratios that vary from 0.18 to 4.68 Ra (mean 1.62 Ra), and their 40Ar/36Ar ratios range from 426.70 to 1408.06 (mean 761.81); spodumene pegmatites have 3He/4He ratios that vary from 0.18 to 2.66 Ra (mean 0.87 Ra) and their 40Ar/36Ar ratios range from 402.13 to 1907.34 (mean 801.65). These data indicate that the hydrothermal fluids were shown a mixture of crust- and mantle-derived materials, and the proportion of crust-derived materials in spodumene pegmatites increases significantly in the late stage of the magmatic evolution. The δ18OH2O–VSMOW values of common pegmatites range from 6.2‰ to 10.9‰, with a mean value of 8.6‰, and δDV–SMOW values vary from − 110‰ to − 72‰, with a mean of − 85‰. The δ18OH2O–VSMOW values of spodumene pegmatites range from 5.3‰ to 13.2‰, with a mean of 9.1‰, and δDV–SMOW values vary from − 115‰ to − 77‰, with a mean of − 91‰. These data suggest that the ore-forming fluids came from primary magmatic water gradually mixing with more meteoric water in the late stage of the magmatic evolution. Based on the He–Ar–H–O and other existing data, we propose that the ore-forming metals are mainly derived from the upper continental crust with a minor contribution from the mantle, and the fluid exsolution and addition of meteoric water during the formation of pegmatite contributed to the formation of the Jiajika superlarge lithium deposit. [ABSTRACT FROM AUTHOR]

Tungsten-tin-(rare-metal) deposits are most commonly granite-related and an important source of critical metals. This study describes the fluid evolution in the Tiantangshan Rb-Sn-W deposit, Nanling Range, China, and discusses the implications for mineralizing processes. Mineralization at Tiantangshan is spatially zoned. The greisen roof hosts wolframite-cassiterite quartz veins. The surrounding volcanic rocks host biotite quartz veins (Rb mineralization) crosscut by cassiterite quartz veins and sphalerite-galena quartz veins. The earliest intermediate-density fluids are responsible for the early W-(Sn)-Rb mineralization and evolve towards decreasing homogenization temperature (Th) and ratios of W, Sn, Rb, Cs, Fe, and Mn to Na + K as the fluid migrated from the greisen to the volcanic rocks hosted veins (Th: 420 to 350 °C; salinity: 13 to 4 wt% NaCleq). The spatial distribution of mineralization and fluid paragenesis indicates that precipitation of wolframite, early cassiterite, and Rb-rich biotite was associated with a pH increase during fluid-rock interaction. Late cassiterite and intergrown quartz precipitated from a degassing fluid with lower Th (mainly 360 to 340 °C) and salinity (10 to 2 wt% NaCleq) and with distinctly lower Sn concentrations. Late cassiterite precipitation is therefore likely related with depressurization by brittle failure of the rock leading to simultaneous boiling and meteoric water input. Late Pb–Zn mineralization precipitated from low Th (< 320 °C) and salinity (0 to 2 wt% NaCleq) fluids through extensive mixing with meteoric water. The tempo-spatial development of Rb-Sn-W-Pb–Zn mineralization at Tiantangshan was controlled by a mixing fluid regime, where input of meteoric water gradually increased with time. [ABSTRACT FROM AUTHOR]

Orogenic gold deposits, though construed to focused fluid flow during orogenesis, commonly post-date the main accretionary events. Several lines of evidence indicate that orogenic gold formation in the Arabian–Nubian Shield continued through the orogen collapse stage and associated rapid exhumation and thermal re-equilibration. The Gidami gold deposit in the Eastern Desert of Egypt is associated with post-foliation, brittle-ductile shear zones that deformed a weakly foliated tonalite-trondhjemite massif dated as ~ 704 Ma (U–Pb zircon age). Gold-sulfide quartz veins exhibit textural features indicative of repeated mylonitization, recrystallization, and muscovite crystallization. New 40Ar/39Ar ages of muscovite flakes from the auriferous quartz veins and from the altered wallrock overlap within analytical uncertainty at ~ 583 Ma, which corresponds to the climax of extension-related wrenching and rapid exhumation in the region (~ 596 to 582 Ma). Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data coupled with microtextural characteristics suggest that early formed pyrite generations experienced substantial fluid-mediated recrystallization, and that a set of metals was remobilized by later fluids. A late generation of fibrous pyrite, ubiquitous in microfractures, deposited while the veins re-opened and deformed. The occurrence of free gold particles along with a late-paragenetic assemblage of galena-sphalerite-chalcopyrite(± hessite ± cervelleite) was related to influx of low salinity, metalliferous H2O-NaCl-CO2-CH4 fluids as indicated by the fluid inclusion laser Raman spectroscopy and microthermometry results. Au-mobilization and redeposition at T ≤ 350 °C and P ~ 1 to 1.7 kbar, triggered by intermittent fluid pluses and thermal re-equilibration, were most likely stimulated by extensional structures and within-plate magmatism. Coincident province- and deposit-scale pressure–temperature-time data highlight the pivotal role of the orogenic collapse tectonics in gold endowment in the Central Eastern Desert's crust. [ABSTRACT FROM AUTHOR]

The Maogongdong deposit is located in the giant Dahutang W-Cu-(Mo) ore field, northern Jiangxi Province, South China. It is mainly a vein-type deposit, characterized by early W and late Cu-Mo mineralization, and temporally and spatially associated with Late Mesozoic S-type muscovite granites emplaced into a Neoproterozoic granodiorite batholith and the Shuangqiaoshan Group metasedimentary rocks. Fluid inclusions and H–O isotopes suggest that the early ore-forming fluids of the Maogongdong deposit are mainly magmatic water with relatively high temperature (270–410 °C) and moderate-to-low salinity, while the late ore-forming fluids are mixed with meteoric water, with medium-to-low temperature (160–270 °C) and low salinity. Infrared and conventional microthermometric studies of fluid inclusions of the main tungsten mineralization stage show that the homogenization temperatures of primary fluid inclusion assemblages in wolframite (325 to 355 °C) are about 20 °C higher than those of coexisting scheelite and generally 40 °C higher than those in quartz. The δ34S values of sulfides (− 5.2 to − 1.3 ‰) in the sulfide stage are slightly lower than the magmatic sulfur (− 1.7 to 0.6 ‰) in the pre-ore stage, most likely due to an increase in oxygen fugacity. The low carbon isotope values (− 26.2 to − 15.5 ‰) of fluid inclusions in the tungsten mineralization stage show that a large amount of organic carbon was added before mineralization. Fluid cooling and pressure decrease are the main factors of tungsten ore precipitation, while local boiling may also make a contribution. Mixing of the different fluids led to the formation of copper and molybdenum ores. [ABSTRACT FROM AUTHOR]

Although China is well-endowed with tungsten deposits, while the tungsten resources in the Central Asian Orogen Belt (CAOB) are rarely reported. Recently, many W-skarn deposits have been discovered in the East Tianshan, but the source and evolution of the mineralising fluids are poorly understood. The Xiaobaishitou W(–Mo) deposits are hosted by carbonaceous limestone or banded crystalline limestone in the Mesoproterozoic Jianshanzi Formation, which is intruded by Triassic biotite monzogranite. The deposit comprises garnet-dominated prograde skarn and retrograde skarns followed by oxides (scheelite–cassiterite–magnetite), sulphides (quartz–molybdenite–bismuthinite–pyrite–chalcopyrite–sphalerite–galena), and carbonate stages. The types of fluid inclusions are composed of liquid-rich aqueous, vapour-rich aqueous, aqueous carbon-dioxide, and daughter mineral-bearing inclusions. The homogenization temperatures of fluid inclusions change from > 400 °C in garnet, through > 380 °C in epidote and 310–280 °C in scheelite, to 280 °C in quartz and 220 °C in calcite indicating a complex magmatic-hydrothermal process. The δ18Owater values varied from + 6.1 to + 8.4‰ in garnet, + 5.2 to + 7.4‰ in epidote, + 2.0 to + 3.0‰ in quartz, to − 0.7 to − 0.1‰ in calcite. The corresponding δD values are − 95 to − 71‰ in garnet, − 84 to − 80‰ in epidote, − 115 to − 90‰ in quartz and − 101 to − 89‰ in calcite. Both O and H isotopic compositions show the mineralisation fluids are originated from deep-sourced magmatic fluids. The δ13CCO2 values in the calcite range from − 7.8 to − 7.7‰, which is characteristic of magmatic fluids interacting with reduced carbon from metamorphic rocks. The δ34S values of hydrothermal fluids range from + 4.5 to + 5.1‰, and 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of sulphide are 18.072–18.664, 15.566–15.708, and 38.245–38.658, respectively, representing a mixed characteristic of magmatic and sedimentary sulphur. Considering the coexisting of L-type and V-type inclusions in the scheelite, we proposed that pH increase caused by fluid boiling may be the major cause for the precipitation of scheelite at the Xiaobaishitou deposit. [ABSTRACT FROM AUTHOR]

The Huangtan (including Jinling) Au–Cu–Zn deposit is an auriferous volcanogenic massive sulfide (VMS) deposit discovered in East Tianshan, Central Asian Orogenic Belt. The deposit is hosted in volcanic breccia and tuff of the Silurian Hongliuxia Formation. The ore bodies consist of concordant massive sulfide lenses and discordant sulfide veins. Chalcopyrite Re–Os dating constrained the age of mineralization in the Huangtan deposit at 432 Ma. Quartz and barite host abundant liquid-rich, liquid-only and minor vapor-rich aqueous fluid inclusions. The fluid inclusions in barite from the exhalative–sedimentary units mainly have homogenization temperatures at 140–260 °C, and calculated salinities of 3–9 wt% NaCl equiv.; Those values are at 120–300 °C, and 1–9 wt% NaCl equiv. for varieties in quartz from the vein ores and alteration assemblages. Fluid inclusions extract from pyrite have 3He/4He ratios of 0.929–1.374 Ra, 40Ar/36Ar of 388–520, and 40Ar/4He of 0.355–0.836. The quartz and barite yielded δ18O values of 7.4‰ to 10.1‰ and the δDV-SMOW values of the fluid inclusions in the quartz and barite range from − 69 to − 42‰. The He–Ar and H–O isotopes imply that the ore-forming fluids were derived from a magmatic source with the addition of deeply circulating seawater. The δ34SV-CDT values of pyrite and chalcopyrite range from − 2.0 to 1.5‰, and those of barite samples range from 24.1 to 24.8‰, which indicates that sulfur was derived from magmatic sulfur, and was subjected to fractionation between sulfide and sulfate. Linked to the ore geology, geochronology data, isotope compositions and fluid inclusions obtained in this study with those of previously published adjacent VMS deposits in the Kalatag area suggest that the Huangtan deposit and adjacent VMS deposits formed in the same metallogenic system. [ABSTRACT FROM AUTHOR]

The southern Great Xing'an Range (SGXR), located in the eastern segment of the Central Asian Orogenic Belt (CAOB), is one of the most economically important Cu–Mo–Fe–Sn–Pb–Zn–Ag metallogenic provinces in China. The newly discovered Panjiaduan Cu–Pb–Zn deposit (9.3 Mt; at 1.36% Cu, 2.90% Pb, 3.80% Zn and 38.12 g/t Ag), located in the SE segment of the SGXR, is primarily hosted in fracture zones in volcanic rocks and granodiorite of the Manitu Formation. Four paragenetic stages of metallic mineralization are identified: (I) quartz-pyrite-arsenopyrite; (II) quartz-polymetallic sulphide; (III) quartz-galena-sphalerite-argentite; and (IV) quartz-calcite-minor sulphide. The hydrothermal quartz contains three types of primary fluid inclusion (FIs): vapour-rich two-phase liquid-vapour (LV-type), liquid-rich two-phase liquid-vapour (VL-type) and three-phase liquid-vapour-solid FIs (SL-type). Stages I and II contain all types with homogenization temperatures (Th) of 324–386 °C and 276–334 °C as well as salinities of 0.7–38.0 wt% and 0.9–34.7 wt%, respectively, whereas stage III is composed of VL- and LV-type FIs with Th of 210–269 °C and salinities of 0.5–7.2 wt%. Only VL-type FIs occur in stage IV, with Th of 139–185 °C and salinities of 1.6–4.2 wt%. The δ18OH2O and δD values vary from −15.7 to 2.6‰ and −132.7 to −110.2‰, respectively, indicating predominant meteoric water with an initial magmatic source. The He–Ar isotopic compositions of the pyrite inclusions from the Panjiaduan Cu–Pb–Zn veins suggest that fluids were derived from the crust. [ABSTRACT FROM AUTHOR]

Carlin-type gold deposits are among the largest hydrothermal gold deposits in the world. However, direct dating the metallogenic age of these deposits is difficult, because not all deposits provide material suitable for conventional radiometric methods. Syn-mineralization stage quartz veins from these deposits usually contain abundant fluid inclusions, which allow fluid inclusion 40Ar/39Ar dating. In this study, progressive crushing 40Ar/39Ar dating has been performed on a gold-bearing quartz vein from the Liaotun Carlin-type gold deposit in northwestern Guangxi, China. Argon isotopes liberated from the later steps yielded an isochron age of 200.7 ± 2.1 Ma. We infer that Ar-bearing gas was extracted from the primary fluid inclusions, and that the age of ca. 200.7 Ma reflects the timing of gold mineralization. The initial 40Ar/36Ar ratio corresponding to the isochron is 298.0 ± 4.3, which is statistically indistinguishable from the value for air, indicating that the ore-forming fluids probably mainly derived from gravitational pressure flow in the basin of air-saturated water. Our preliminary study shows the feasibility and great potential of 40Ar/39Ar dating of gases from fluid inclusions by progressive crushing of quartz veins to date the mineralization age and decipher the fluid origins of Carlin-type gold deposits. [ABSTRACT FROM AUTHOR]

The textures and compositions of hydrothermal apatite grains have been reported in many iron oxide-apatite (IOA), porphyry, and rare-earth elements (REE) polymetallic deposits. However, such information for apatite in hydrothermal gold deposit is not available. In this study, we present integrated textural, elemental, and in situ oxygen isotopic data of hydrothermal apatite grains from the Hatu gold deposit (56t Au, average grade: 5 g/t) in the West Junggar, Northwest China, to investigate the detailed mineralization processes and nature of ore-forming fluids. Hydrothermal apatite is present within the quartz-sulfide ores at the Hatu gold deposit. Apatite grains of the Hatu gold ores contain abundant fluid inclusions and fine sulfide crystals, indicating that they are closely related to gold mineralization. Three types of hydrothermal fluorapatite (Ap1, Ap2, and Ap3) were revealed by Cathodoluminescence (CL) imaging. The Ap1 and Ap2 formed in the auriferous ore-forming stage, whereas the Ap3 formed in the post-ore stage. The three types of apatite have distinct total REE concentrations (216–751 ppm for Ap1, 14–120 ppm for Ap2, and 914–1422 ppm for Ap3) as well as chondrite-normalized REE distribution patterns. The textures and compositions of different apatites are inconsistent with dissolution–re-precipitation processes but instead point to three episodes of apatite formation in the Hatu hydrothermal system. The Ap3 has different REE and lower Eu/Eu* values (0.97–1.72) than Ap1 (1.34–4.50) and Ap2 (1.69–4.95), indicating a change of fluid compositions and a decrease of oxygen fugacity from the auriferous ore-forming stage to post-ore stage. All three types of apatite (Ap1, Ap2, and Ap3) show relatively high and consistent oxygen isotope compositions ranging from 14.2 ± 0.3‰ to 15.2 ± 0.2‰, from 14.5 ± 0.2‰ to 15.0 ± 0.3‰, and from 13.8 ± 0.3‰ to 15.4 ± 0.2‰, respectively. Their calculated δ18Ofluid values are higher than magmatic–hydrothermal fluids but consistent with those from metamorphic fluids derived from meta-basalts. The near-zero δ34S values of hydrothermal pyrite grains in the gold ores are much higher than those of pyrite framboid grains in the ore-hosted sedimentary rocks (− 41.1 to − 24.3‰), suggesting the sulfur may be derived from meta-basalts rather than sedimentary rocks in the mining area. Taken together, we suggest that Hatu is an orogenic gold deposit formed by fluids and metals derived from metamorphic de-volatilization of meta-basalts at depth. Our study highlights that a combination of CL imaging, in situ trace elements, and oxygen isotope compositions of hydrothermal apatite can be a novel and powerful tool to trace the nature of ore-forming fluids in the hydrothermal gold deposits. [ABSTRACT FROM AUTHOR]

The large Hebaoshan gold deposit (41.5 t Au, average grade: 3.5 g/t) is located in a hitherto poorly documented gold province in the northeastern part of the South China Block. It is hosted by Precambrian metasedimentary rocks that experienced Triassic greenschist- to amphibolite-facies metamorphism. Three hydrothermal stages can be distinguished: quartz + sericite + pyrite + pyrrhotite (stage I), quartz + magnetite + sulfide (stage II), and quartz + carbonate + pyrite + hematite (stage III). Auriferous pyrite samples yielded a Rb-Sr isochron age of 234 ± 3 Ma (2σ, MSWD = 0.24), and ore-related hydrothermal sericite yielded a 40Ar-39Ar plateau age of 226.4 ± 2.0 Ma (2σ, MSWD = 1.01), which are distinctly younger than ca. 430 Ma granitic rocks in the mining district and older than 170–130 Ma granites in the region, ruling out any genetic link between granite emplacement and gold mineralization. The mineralizing fluid system can be described as carbonic-aqueous with low to moderate salinity (2.2–10.1 wt% NaCl equiv.) and medium temperature of 290 to 350 °C (stage I) and 230 to 280 °C (stage II). The δ18O quartz ranges from 13.3 to 15.4 ‰, and the δD values for fluid inclusions in quartz range from − 97 to − 60 ‰. The calcite has C-isotopes ranging from − 6.1 to − 3.8 ‰ and O-isotopes from 2.8 to 13.6 ‰. H-O-C isotope data are consistent with a metamorphic fluid derived from devolatilization of Neoproterozoic basement rocks during regional metamorphism in the Late Triassic Indosinian period. The δ34S values of sulfides for stages I, II, and III are 0.1 to 7.8 ‰, − 10.6 to 5.1 ‰, and − 18.9 to − 14.1 ‰, respectively, indicating an increase in oxygen fugacity during fluid ascent which resulted in more negative sulfur isotope values of sulfides and precipitation of gold. Pyrite separates have 206Pb/204Pb ratios of 17.340 to 17.687, 207Pb/204Pb ratios of 15.539 to 15.604, and 208Pb/204Pb ratios of 37.749 to 38.094. The S-Pb isotope data suggest derivation of S and Pb from the Precambrian metasedimentary country rocks. Auriferous pyrite yielded elevated 3He/4He ratios (0.78–1.46 Ra), which suggest a mantle component as can be expected from fluids derived from a subduction setting. It is concluded that Hebaoshan is an orogenic gold deposit that formed during Triassic flat-slab subduction of the paleo-Pacific plate beneath the South China Block and thus constitutes the first Triassic deposit of this type recognized in the coastal area of Southeast China. [ABSTRACT FROM AUTHOR]

The Lianhuashan Au deposit, located in the northern margin of North China Craton, is hosted in the metamorphic rocks of Neoarchean Wulashanyan Group along NNW- to N-trending faults, with pyrite as the predominant ore mineral. The mineralization process can be divided into four stages, involving stage I quartz-pyrite, stage II quartz-magnetite-chalcopyrite, stage III quartz-marcasite-pyrite, and stage IV quartz-calcite. Three types of fluid inclusions (FIs) have been identified, namely, pure carbonic inclusions (PC-type), aqueous-carbonic inclusions (AC-type), and aqueous inclusions (A-type). Stage I auriferous quartz veins host all three types of FIs, inclusions from stage II quartz are AC- and A-type, and only A-type FIs are recognized in stage III quartz and stage IV calcite veins. The FIs of stages I to IV were homogenized at temperatures of 300–360 °C, 275–326 °C, 252–289 °C, and 220–264 °C, with salinities of 4.0–11.7 wt%, 3.4–9.3 wt%, 2.1–7.0 wt%, and 1.4–3.1 wt% NaCl eqv., respectively. The ore-forming fluids belong to a medium-temperature, low-salinity H2O–NaCl–CO2 system. Gold deposition was likely caused by fluid immiscibility. The δDH2O and δ18OH2O values of ore fluids vary from −121.1 to −112.4‰ and from 2.8 to 6.2‰, respectively, within the range of enriched mantle-derived fluids in the North China Craton. The carbon isotope compositions of calcite (δ13CPDB = −2.87 to −2.38‰) show the features of mantle carbon. S-Pb isotope compositions of pyrite (δ34S = 2.58-3.96, 206Pb/204Pb = 16.077-16.119, 207Pb/204Pb = 15.329-15.332, and 208Pb/204Pb = 37.305-37.338) reveal that the ore-forming materials may have originated from crustal rocks. Based on the geological and geochemical observations, we suggest that the Lianhuashan deposit can be classified as an orogenic gold deposit. [ABSTRACT FROM AUTHOR]

The Huangshui'an deposit located in East Qinling (China) is an unusual case of a Si-rich carbonatite hosting economic Mo and minor Pb and REE mineralization. The role of mantle-sourced carbonatite melts and fluids in the formation of the Mo mineralization remains poorly understood. Our integrated study based on field geology, petrography, microthermometry, and LA-ICP-MS analysis of single fluid inclusions, and noble gas isotopes of pyrite permits to reconstruct the source characteristics, the magmatic-hydrothermal evolution of the carbonatitic fluids, and their controls on Mo mineralization. Fluid inclusions hosted in calcite in the carbonatite dikes have the highest concentrations of Mo (9.9–62 ppm), Ce (820–9700 ppm), Pb (1800–19500 ppm), and Zn (570–5800 ppm) and represent the least modified hydrothermal fluid derived from the carbonatite melt. Fluid inclusions hosted in calcite (Cal) and quartz (Qz2 and Qz3) of the stage I carbonatite dikes have different metal concentrations, suggesting that they formed from two distinct end member fluids. The FIA in calcite represent fluid A evolved from carbonatite melt with relatively high-ore metal concentrations, and those in quartz characterize fluid B having a crustal signature due to metasomatic reactions with the wall rocks. The FIA in quartz (Qz1) within the altered wall rock have overlapping elemental concentrations with those of massive quartz (Qz2) and vuggy quartz (Qz3) in carbonatite. This suggests that the volumetrically significant quartz in the Huangshui'an carbonatite has been formed by the introduction of Si by fluid B. The positive correlations between Rb, B, Al, Cl, and Sr in stage II fluid inclusions in late fluorite + quartz + calcite veins indicate that this late mineralization formed from the mixing of primary hydrothermal fluid B with meteoric water. The He–Ar isotope data, in combination with available C–O–Sr–Nd–Pb isotope data, constrain the carbonatite source as an enriched mantle source modified by contributions from crustal material which was probably the fertile lower crust in the region. This distinct source facilitated the enrichment in Mo, REE, and Pb in the primary carbonatite magma. The carbonatite magmatism and Mo mineralization at 209.5–207 Ma occurred in the regional-scale extensional setting at the postcollision stage of the Qinling Orogenic Belt. [ABSTRACT FROM AUTHOR]

The newly discovered large-scale skarn deposit of Youmapo tungsten-molybdenum deposit is located in the Bobai-Cenxi metallogenic belt of the southeastern Guangxi, south China. The stratiform, lentoid, and vein ore-bodies occur along the contact zone between the Devonian calcareous-argillaceous siltstone and Youmapo granitic complex pluton. The Youmapo granitic complex pluton consists of main granodiorite (109.7 ± 1.1 Ma) and complementary muscovite granite (100.7 ± 0.5 Ma). Up to now, WO3 reserves were estimated at more than 80 thousand tons, with grades 0.191~1.284% WO3 and 0.001~0.019% Mo. Among them, No. I ore-body accounts for 84% of the total reserve. Four types of fluid inclusions are recorded in the Youmapo deposit (NaCl-H2O, NaCl-CO2-H2O, pure CO2, and monophase H2O) and characterized by medium-high temperature (190~340 °C) and low salinity (3~10 wt%NaCleq). According to the S, H, and O isotopic characteristics, the ore-forming fluid is mainly post-magmatic fluid. The complementary muscovite granite geochemically represents high evolution granite that derived the ore-forming fluid. Six molybdenite samples from No. I ore-body yield an 187Re-187Os isochron age of 100.1 ± 3.3 Ma and a consistent weighted average model age of 100.37 ± 0.62 Ma, suggesting the Cretaceous period for the tungsten-molybdenum mineralization and their spatio-temporal relation to the muscovite granite. [ABSTRACT FROM AUTHOR]

The Daqingshan gold deposit, located in the Beishan orogenic belt, northwestern China, is hosted in a Carboniferous greenschist facies metavolcanic-sedimentary sequence. Three periods of metamorphic and deformational events were recognized, corresponding with the three types of quartz veins in the deposit area. Quartz veins formed in the second period (D2) are the main auriferous ones that are strictly controlled by the subsidiary structures of the Kuluke shear zone. Gold mineralization occurs both as quartz veins and as enveloping altered wall rocks. Native gold, pyrite, and arsenopyrite are the primary ore minerals, while quartz and sericite are the main gangue minerals. Wall-rock alteration predominantly consists of silicification, sericitization, arsenopyritization, and pyritization. Systematic fluid inclusion investigation shows that CO2-H2O three-phase inclusions are the dominant type of fluid inclusions in the auriferous quartz veins, suggesting that the ore-forming fluids belong to a CO2-H2O ± CH4 ± N2 system that is particularly rich in CO2. The ore fluids are characterized by medium to high temperature (230~380 °C), low salinity (2~8% NaCleqv.), and medium density (0.8~0.9 g/cm3). Oxygen isotopes (δ18Ofluid = 11.3‰ to 13.9‰) indicate that the ore-forming fluids were most likely derived from metamorphic water. Fluid immiscibility might be the critical mechanism leading to the deposition of gold. The U-Pb dating results of hydrothermal zircons from auriferous quartz veins indicated that the maximum timing of the gold mineralization at Daqingshan was 295 Ma, the Early Permian. Comprehensive studies suggest that the Daqingshan deposit is a typical orogenic gold deposit formed during the subduction-accretionary phase of the Beishan orogenic belt. Significantly, recognizing the ore genesis of the Daqingshan gold deposit has an important implication for deep and regional mining exploration of southern Beishan. [ABSTRACT FROM AUTHOR]

This study investigates apatite and anhydrite inclusions in zircon from ore-forming intrusions in the Duolong porphyry Cu-Au deposit, central Tibet (Fig. 2 Geological characteristics (a) and cross sections (b, c) of the Duolong porphyry Cu-Au deposit, central Tibet, showing sample locations (Li et al. [21], [25]) The Duolong magmatic complex evolved from diorite to granodiorite porphyry and quartz diorite porphyry, the hosts of Cu-Au mineralization (Fig. Apatite inclusions ( I n i = 98) in zircon from the granodiorite porphyry and quartz diorite porphyry have F contents of 1.14-2.99 wt%, Cl of 0.16-2.51 wt%, and SO SB 3 sb of 0.04-1.38 wt%, with minor SiO SB 2 sb (0.05-1.39 wt%), MnO (0.12-0.93 wt%), Na SB 2 sb O (0-0.28 wt%), and FeO (0.01-0.64 wt%; Supplementary Table 1). Apatite and anhydrite were randomly enclosed by zircon crystals, which were later hosted in ore-forming porphyries One apatite inclusion coexisting with an anhydrite inclusion in a single zircon grain contains 0.69 wt% SO SB 3 sb with a low I X i SB F sb / I X i SB Cl sb ratio of ~ 1.2 (Fig. [Extracted from the article]

Most skarns are found near the pluton or in lithologies containing at least some limestone. However, recent research has shown that neither a pluton nor limestone is necessarily required to form a skarn deposit. The newly discovered Bagenheigeqier Pb–Zn skarn deposit is located in NE China. The skarn and Pb–Zn orebodies occur in volcanic lithologies of the Baiyin'gaolao Formation and are controlled by NE–SW-trending faults. The nearest pluton is a granite porphyry, at a distance of 20–250 m from the orebodies. Five paragenetic stages at Bagenheigeqier are recognized: (I) skarn; (II) oxide; (III) early sulphide; (IV) late sulphide; and (V) late quartz–calcite. The fluid inclusions from stages II to V homogenized at temperatures of 402–452, 360–408, 274–319 and 167–212°C, respectively. The hydrogen and oxygen isotope compositions (δ18OH2O, –12.4‰ to +9.3‰; δDH2O, –156.5‰ to –99.1‰) indicate that the ore-fluids were primarily of magmatic origin, with the proportion of meteoric water increasing during the progression of ore formation. Sulphur isotope values (δ34SVCDT, 1.4–5.5‰), lead isotope values (206Pb/204Pb, 18.184–18.717; 207Pb/204Pb, 15.520–15.875; 208Pb/204Pb, 37.991–38.379) and the initial 187Os/188Os ratios of the pyrite (0.307 ± 0.06) suggest that the ore metals were derived from the granite porphyry and Baiyin'gaolao Formation. Re–Os dating of pyrite intergrown with galena and sphalerite yielded a well-constrained isochron age of 151.2 ± 4.7 Ma, which is coeval with the laser ablation – inductively coupled plasma – mass spectrometry zircon U–Pb age of 154 ± 1 Ma for the granite porphyry. The deposit was therefore formed during Late Jurassic time. [ABSTRACT FROM AUTHOR]

The Zhilingtou polymetallic deposit, South China, provides an excellent opportunity to investigate the magmatic-hydrothermal evolution of the porphyry Mo to epithermal Au–Ag–Pb–Zn ore spectrum. New zircon U–Pb, sphalerite 40Ar/39Ar, and pyrite Rb–Sr ages, together with previous molybdenite Re–Os ages, indicate that the granitic magmatism and Mo–Au–Ag–Pb–Zn mineralization were coeval and cogenetic in the Early Cretaceous (~ 113 Ma). Fluid inclusions and H–O isotope results have established the evolution from an early high-temperature H2O–NaCl magmatic fluid system (Mo mineralization), to a medium-temperature mixed fluid system of magmatic and meteoric water (Au–Ag mineralization), to a peripheral late-stage low-temperature H2O–NaCl meteoric water fluid system (epithermal Au–Ag–Pb–Zn mineralization). Moreover, the sulfur isotopic compositions (δ34S = 2.1–7.8‰) of the sulfide minerals confirm a genetic link to the granitic magma. Lead isotope data from pyrite and the granite–rhyolite porphyries are similar, indicating that they share a common Pb source. The geochronological, geochemical, and isotopic lines of evidences consistently suggest that the porphyry Mo and epithermal Au–Ag–Pb–Zn mineralization formed in one magmatic–hydrothermal system. The porphyry-epithermal mineralization model for Zhilingtou has significant importance for prospecting work in South China, where Mo and associated Pb–Zn–Ag resources are abundant. [ABSTRACT FROM AUTHOR]

The Xiling Sn deposit in eastern Guangdong Province comprises the Fengdishan Sn and the Saozhoudi Sn–Pb–Zn ore blocks and has long been regarded as a volcanic–subvolcanic system related to Sn polymetallic mineralization. Here, we present fluid inclusion microthermometric data from different ore stages and H–O–S isotope data of hydrothermal minerals to constrain the genesis of the Xiling deposit. Fluid inclusions from stage I have Th values from ~ 340 to 420 °C and salinities from ~ 15 to 17 wt% NaCl equivalent, while homogenization temperatures of fluid inclusions from stages II to V range from ~ 150 to 320 °C, and salinities range between ~ 1 and 6 wt% equivalent. The oxygen and hydrogen isotopic composition of quartz and cassiterite (δDfluid − 65‰; δ18Ofluid 3.6 to 6.3‰) suggest that the ore-forming fluids from stage I have a distinct magmatic signature, whereas those from stage II through stage IV (δDfluid from − 80 to − 49‰; δ18Ofluid from − 3.7 to 2.5‰) show characteristics of mixing between meteoric and magmatic fluids. Moreover, δ34S values for sulfides from the Fengdishan ore block have a narrow range of 0.6 to 2.5‰ with a mean close to 0‰, consistent with a magmatic sulfur source. By contrast, δ34S values for ore minerals from the Saozhoudi ore block range from 3.4 to 11.5‰, suggesting involvement of a sedimentary sulfur source. In addition, a previous geochronological study has shown that the volcanic–subvolcanic host rocks have an age of 160–170 Ma, while the Sn polymetallic mineralization has an age of about 145 Ma. Our data support a model of mixing of magmatic brine from a hidden granitic intrusion with meteoric water. The S isotope data and the observed temperature gradient of the fluid system suggest that the Sn mineralization is developed in the central part of the ore system, while the Sn–Pb–Zn and Pb–Zn mineralization occurs in the distal part. This finding might have important implications for exploration in the region. [ABSTRACT FROM AUTHOR]

We studied the fluid inclusions of the Jiguanshan Mo deposit in China, which is a large porphyry deposit located in the southern Xilamulun Metallogenic Belt. The irregular Mo ore body with various types of hydrothermal veinlets is hosted by Late Jurassic granite porphyry. Intense hydrothermal alterations in the deposit from the core to margin are silicification–potassium feldspar alteration, pyrite–quartz–sericite–fluorite alteration, and propylitic alteration. Based on the mineral assemblages and crosscutting relationships of ore veins, the ore-forming process were divided into three stages and two substages: quartz–pyrite veins (stage I) associated with potassic alteration; quartz–molybdenite–chalcopyrite–pyrite veins (substage II-1) and quartz–molybdenite–fluorite veins (substage II-2) associated with phyllic alteration; and fluorite–quartz–carbonate veins (stage III) with carbonation. Five major fluid inclusions (FIs) types were distinguished in the quartz associated with oxide and sulfide minerals, i.e. polyphase brine (Pb-type), opaque-bearing brine (Ob-type), solid halite (S-type), two-phase aqueous (A-type), and vapor (V-type) inclusions. The FIs of stage I were composed of liquid-rich S-, A-, and V-type FIs with homogenization temperatures and salinities of 490 to 511 °C and 8.9 to 56.0 wt% NaCl equiv., respectively. The FIs of substage II-1 are composed of Pb-, Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 352 to 460 °C and 3.7 to 46.1 wt% NaCl equiv, respectively. The FIs of substage II-2 are Ob-, S-, A-, and V-type FIs with homogenization temperatures and salinities of 234 to 309 °C and 3.7 to 39.2 wt% NaCl equiv, respectively. The FIs of stage III are A-type FIs with homogenization temperatures and salinities of 136 to 172 °C and 1.1 to 8.9 wt% NaCl equiv, respectively. Fluid boiling, which resulted in the precipitation of sulfides, occurred in stages I and II. The initial ore-forming fluids of the Jiguanshan deposit had high temperature, high salinity, and belonged to an F-rich NaCl ± KCl–H2O system. The fluids gradually evolved to low temperature, low salinity, and belonged to a NaCl–H2O system. Studies of the hydrogen and oxygen isotope compositions of quartz (δ18OH2O = − 7.3 to 6.3‰, δDH2O = − 104.3 to − 83.3‰) show that the ore-forming fluids gradually evolved from magmatic water to meteoric water. [ABSTRACT FROM AUTHOR]

The Middle Triassic Laojiagou porphyry Mo deposit is located in the Xilamulun metallogenic belt, along the northern margin of the North China Craton (NCC). Molybdenum mineralization is associated with a monzogranite porphyry and occurs primarily in quartz veins and veinlets hosted in wall rocks affected by potassic, silicic, sericitic, and propylitic alteration. The ore-forming process is divided into three stages, characterized by veinlets comprising molybdenite + pyrite + quartz (stage I), pyrite + chalcopyrite + molybdenite + quartz (stage II), and pyrite + quartz (sulfide-poor) (stage III). We identify three fluid inclusion types in quartz grains: carbonic (C-type), liquid-rich two-phase (L-type), and rare vapor-rich two-phase (V-type) inclusions. Microthermometric results indicate that an initial high-temperature (> 350 °C) and low-salinity (< 10 wt% NaCl equiv.) CO2-rich fluid evolved to a low-temperature (< 280 °C) and CO2-poor fluid, comprising dominantly of meteoric water. Hydrogen and oxygen isotopes indicate that initial ore-forming fluids were magmatic and became progressively mixed with meteoric water (stage I δ18OH2O = 4.4–4.8‰ and δDH2O = − 105.8 to − 101.5‰). Zircon U–Pb dating indicates that the monzogranite porphyry formed at 232.2 ± 3.6 Ma (MSWD = 0.88). The porphyry has high SiO2, K2O, and Al2O3 and low MgO and CaO concentrations and is classified as high-K calc-alkaline and weakly peraluminous. All samples are enriched in light rare earth and large-ion lithophile elements and depleted in high-field-strength elements. Our results indicate that the Laojiagou porphyry Mo deposit formed in the Middle Triassic, associated with post-orogenic extension following closure of the Palaeo-Asian Ocean. [ABSTRACT FROM AUTHOR]

Vein-type deposits, including the Xiangdong W–Sn and Dalong Pb–Zn deposits, occur in or near the Dengfuxian composite granite pluton, comprising predominantly Triassic and minor Jurassic intrusions. Liquid-rich NaCl-aqueous inclusions, vapor-rich NaCl-aqueous inclusions, liquid-rich CaCl2-NaCl-aqueous inclusions, two-phase CH4-rich inclusions, three-phase CO2-H2O inclusions, and three-phase calcite-bearing inclusions occur in the quartz veins at Xiangdong, whereas only liquid-rich NaCl-aqueous inclusions occur at Dalong. The Xiangdong veins formed at temperatures near 241 °C, from NaCl-CaCl2-H2O-CH4-CO2 fluids averaging 11.4 wt% NaCl eq. The Dalong deposit formed at temperatures near 186 °C from NaCl-H2O(-CH4) fluids averaging 6.2 wt% NaCl eq. The ore-forming mechanisms at Xiangdong include fluid immiscibility during stage I, fluid mixing during stage II, and mixing with meteoric water accompanied by cooling during stage III. The ore-forming mechanisms at Dalong include cooling and mixing with meteoric water. Oxygen and hydrogen isotopes suggest that the ore-forming fluids from both deposits originated as mixtures of magmatic water with various amounts of meteoric water. Sulfur and strontium isotopes suggest an igneous origin for both deposits and possibly mixing with S and Sr from sedimentary rock for Dalong. Lead isotopes indicate that ore metals originated mainly from the upper crust with minor mantle contributions. Sphalerite from Dalong gives a Rb-Sr isochron age of 151.6 ± 7.1 Ma, consistent with the mineralization age of Xiangdong. Both the W–Sn and Pb–Zn ore-forming events are closely related to Late Jurassic magmatism, which occurred in an environment of lithospheric extension and thinning. [ABSTRACT FROM AUTHOR]

The Tuwu porphyry Cu deposit, located in Eastern Tianshan, NW China, is hosted by a plagiogranite porphyry and Carboniferous Qi'eshan Group volcanic rocks. Based on crosscutting relationships and mineral assemblages, hydrothermal alteration and mineralization processes at Tuwu can be divided into four stages: early propylitic alteration (stage I), porphyry mineralization (stage II), overprinting mineralization (stage III), and post-mineralization (stage IV). The porphyry mineralization stage (stage II) contributed to the majority of the Cu–Mo resource, with Cu mineralization occurring mainly as quartz-chalcopyrite veins. Stage III also produced minor Cu mineralization, characterized by chalcopyrite–anhydrite–chlorite–calcite assemblages. Fluid inclusion (FI) study reveals that stage II is characterized by a high-temperature, high-salinity, highly oxidized, and K-rich H2O–NaCl–CaCl2 fluid. Fluid boiling and mixing likely occurred during the porphyry mineralization stage, leading to the precipitation of chalcopyrite and pyrite. Alteration and mineralization in stage III were derived from a S-rich H2O–NaCl–CaCl fluid, with fluid boiling leading to the precipitation of chalcopyrite. The δ34S values of chalcopyrite from stages II and III are − 0.8–0.6 ‰ and 1.1–1.3 ‰, respectively, suggesting magmatic sources for the ore-forming components of both stages. 40Ar/39Ar dating indicates that stage II likely occurred at 328.1 ± 1.4 Ma, around the age emplacement of the causative plagiogranite porphyry (ca. 337.7–330.3 Ma). We suggest the overprinting mineralization event occurred at ca. 323 Ma, spatially and genetically related to the emplacement of the quartz albite porphyry at 323.6 ± 2.5 Ma. [ABSTRACT FROM AUTHOR]

The Huize Zn–Pb–Ag deposit in SW China has an ore reserve in excess of 5 Mt. with an ore grade of ≥25 wt% Zn + Pb and 46–100 g/t Ag. This deposit is hosted in Carboniferous dolostone and limestone. Sulfide mineralization is dominated by sphalerite, galena, and pyrite. Four types of pyrite (Py1 to Py4) are temporally and spatially related to mineralization distinguished on the basis of textural features and mineral associations. Pyrite 1 to 3 corresponds to the pyrite-sphalerite sub-stage, whereas Py4 corresponds to sphalerite-galena-pyrite sub-stage. Pyrite 1 shows zoned texture composed of an inclusion-rich core and an inclusion-free rim, whereas Py2, Py3, and Py4 show replacement relic or overgrowth textures. The zoned texture in Py1 was formed by multiple stages of ore fluids, whereas replacement relic texture in Py2 to Py4 was formed by replacement of pyrite by late Pb-Zn-rich fluids. Trace element variation in pyrite results from a combination of mineral inclusions, co-precipitating minerals, and various fluid compositions. Sphalerite, pyrite, and galena have δ34S values of 10.4–23.5‰, suggesting that sulfur was probably derived from the thermochemical reduction of marine sulfates. The Huize pyrite has Co and Ni concentrations (0.02–9.5 ppm and 0.08–143 ppm, respectively) and Co/Ni ratios (~0.01–2.63) similar to pyrite from sedimentary exhalative deposits, submarine hydrothermal vents, and sedimentary pyrite, which may be due to pyrite precipitation from low-temperature (<~250 °C), basin brines or seawater. The Co/Ni ratios of the Huize pyrite are lower than those (~0.2–7.2) of pyrite from Mississippi Valley-type Zn-Pb deposits. The Huize pyrite has Co and Ni contents lower than those associated with volcanogenic massive sulfide, iron oxide copper gold, and porphyry Cu deposits, arguing against the involvement of a magmatic/volcanic component and a direct genetic link between Permian Emeishan basalts and Pb-Zn mineralization. Combining with fluid inclusion temperatures and silver grade, we define the Huize deposit as a transitional type between Mississippi Valley-type and high-temperature carbonate-replacement Zn-Pb deposits. [ABSTRACT FROM AUTHOR]

The Dalingshang W-Cu deposit is located in the North section of the Dahutang ore field, northern Jiangxi Province, South China. Vein- and breccia-style tungsten-copper mineralization is genetically associated with Mesozoic S-type granitic rocks. Infrared and conventional microthermometric studies of both gangue and ore minerals show that the homogenization temperatures for primary fluid inclusions in wolframite (~ 340 °C) are similar to those in scheelite (~ 330 °C), but about 40 °C higher than those of apatite (~ 300 °C) and generally 70 °C higher than those in coexisting quartz (~ 270 °C). Laser Raman analysis identifies CH4 and N2 without CO2 in fluid inclusions in scheelite and coexisting quartz, while fluid inclusions in quartz of the sulfide stage have variable CO2 content. The ore-forming fluids overall are characterized by high- to medium-temperature, low-salinity, CH4, N2, and/or CO2-bearing aqueous fluids. Chalcopyrite, muscovite, and sphalerite are the most abundant solids recognized in fluid inclusions from different ores. The H-O-S-Pb isotope compositions favor a dominantly magmatic origin for ores and fluids, while some depleted δ34S values (− 14.4 to − 0.9‰) of sulfides from the sulfide stage are most likely produced by an increase of oxygen fugacity, possibly caused by inflow of oxidized meteoric waters. The microthermometric data also indicate that a simple cooling process formed early scheelite and wolframite. However, increasing involvement of meteoric waters and fluid mixing may trigger a successive deposition of base metal sulfides. Fluid-rock interaction was critical for scheelite mineralization as indicated by in-situ LA-ICP-MS analysis of trace elements in scheelite. [ABSTRACT FROM AUTHOR]

The Yamansu Fe deposit (32 Mt at 51% Fe) in the Eastern Tianshan Orogenic Belt of NW China is hosted in early Carboniferous volcano-sedimentary rocks and spatially associated with skarn. The paragenetic sequence includes garnet-diopside (I), magnetite (II), hydrous silicate-sulfide (III), and calcite-quartz (IV) stages. Pyrite associated with magnetite has a Re-Os isochron age of 322 ± 7 Ma, which represents the timing of pyrite and, by inference, magnetite mineralization. Pyrite has δ34SVCDT values of − 2.2 to + 2.9‰, yielding δ34SH2S values of − 3.1 to 2‰, indicating the derivation of sulfur from a magmatic source. Calcite from stages II and IV has δ13CVPDB values from − 2.5 to − 1.2‰, and − 1.1 to 1.1‰, and δ18OVSMOW values from 11.8 to 12.0‰ and − 7.7 to − 5.2‰, respectively. Calculated δ13C values of fluid CO2 and water δ18O values indicate that stage II hydrothermal fluids were derived from magmatic rocks and that meteoric water mixed with the hydrothermal fluids in stage IV. Some ores contain magnetite with obvious chemical zoning composed of dark and light domains in BSE images. Dark domains have higher Mg, Al, Ca, Mn, and Ti but lower Fe and Cr contents than light domains. The chemical zoning resulted from a fluctuating fluid composition and/or physicochemical conditions (oscillatory zoning), or dissolution-precipitation (irregular zoning) via infiltration of magmatic-hydrothermal fluids diluted by late meteoric water. Iron was mainly derived from fluids similar to that in skarn deposits. [ABSTRACT FROM AUTHOR]

The Nanyangtian skarn-type scheelite deposit is an important part of the Laojunshan W-Sn polymetallic metallogenic region in southeastern Yunnan Province, China. The deposit comprises multiple scheelite ore bodies; multilayer skarn-type scheelite ore bodies are dominant, with a small amount of quartz vein-type ore bodies. Skarn minerals include diopside, hedenbergite, grossular, and epidote. Three mineralization stages exist: skarn, quartz-scheelite, and calcite. The homogenization temperatures of fluid inclusions in hydrothermal minerals that formed in different paragenetic phases were measured as follows: 221-423 °C (early skarn stage), 177-260 °C (quartz-scheelite stage), and 173-227 °C (late calcite stage). The measured salinity of fluid inclusions ranged from 0.18% to 16.34% NaCleqv (skarn stage), 0.35%-7.17% NaCleqv (quartz-scheelite stage), and 0.35%-2.24% NaCleqv (late calcite vein stage). Laser Raman spectroscopic studies on fluid inclusions in the three stages showed H2O as the main component, with N2 present in minor amounts. Minor amounts of CH4 were found in the quartz-scheelite stage. It was observed that the homogenization temperature gradually reduced from the early to the late mineralization stages; moreover, δ13CPDB values for ore-bearing skarn in the mineralization period ranged from − 5.7‰ to − 6.9‰ and the corresponding δ18OSMOW values ranged from 5.8‰ to 9.1‰, implying that the ore-forming fluid was mainly sourced from magmatic water with a minor amount of meteoric water. Collectively, the evidence indicates that the formation of the Nanyangtian deposit is related to Laojunshan granitic magmatism. [ABSTRACT FROM AUTHOR]

The Badi copper deposit is located in Shangjiang town, Shangri-La County, Yunnan Province. Tectonically, it belongs to the Sanjiang Block. Vapor-liquid two-phase fluid inclusions, CO2-bearing fluid inclusions, and daughter-bearing inclusions were identified in sulfide-rich quartz veins. Microthermometric and Raman spectroscopy studies revealed their types of ore-forming fluids: (1) low-temperature, low-salinity fluid; (2) medium-temperature, low salinity CO2-bearing; and (3) high-temperature, Fe-rich, high sulfur fugacity. The δ18O values of chalcopyrite-bearing quartz ranged from 4.96‰ to 5.86‰, with an average of 5.40‰. The δD values of ore-forming fluid in equilibrium with the sulfide-bearing quartz were from − 87‰ to − 107‰, with an average of − 97.86‰. These isotopic features indicate that the ore-forming fluid is a mixing fluid between magmatic fluid and meteoric water. The δ34S values of chalcopyrite ranged from 13.3‰ to 15.5‰, with an average of 14.3‰. Sulfur isotope values suggest that the sulfur in the deposit most likely derived from seawater. Various fluid inclusions coexisted in the samples; similar homogenization temperature to different phases suggests that the Badi fluid inclusions might have been captured under a boiling system. Fluid boiling caused by fault activity could be the main reason for the mineral precipitation in the Badi deposit. [ABSTRACT FROM AUTHOR]

The Hashitu porphyry molybdenum deposit is located in the Great Hinggan Range Cu-Mo-Pb-Zn-Ag polymetallic metallogenic province of NE China, in which the Mo-bearing quartz veins are hosted in approximately coeval granites and porphyries. The deposit contains more than 100 Mt of ore with an average grade of 0.13 wt.% Mo. This well-preserved magmatic-hydrothermal system provides an excellent opportunity to determine the source of the molybdenum, the evolution of the hydrothermal fluids and the controls on molybdenite precipitation in a potentially important but poorly understood metallogenic province. Studies of fluid inclusions hosted in quartz veins demonstrate that the Hashitu hydrothermal system evolved to progressively lower pressure and temperature. Mineralogical and fluid inclusion analyses and physicochemical calculations suggest that molybdenite deposition occurred at a temperature of 285 to 325 °C, a pressure from 80 to 230 bars, a pH from 3.5 to 5.6, and a ∆log fO2 (HM) of −3.0, respectively. Results of multiple isotope (O, H, S, Mo, and Pb) analyses are consistent in indicating a genetic relationship between the ore-forming fluids, metals, and the Mesozoic granitic magmatism (i.e., δ18OH2O from +1.9 to +9.7‰, δDH2O from −106 to −87‰, δ34SH2S from +0.3 to +3.9‰, δ98/95Mo from 0 to +0.37‰, 206Pb/204Pb from 18.2579 to 18.8958, 207Pb/204Pb from 15.5384 to 15.5783, and 208Pb/204Pb from 38.0984 to 42.9744). Molybdenite deposition is interpreted to have occurred from a low-density magmatic-hydrothermal fluid in response to decreases in temperature, pressure, and fO2. [ABSTRACT FROM AUTHOR]

The Shizhuyuan polymetallic deposit is located in the central part of the Nanling region, southeastern China, and consists of proximal W-Sn-Mo-Bi skarns and greisens and distal Pb-Zn-Ag veins. The sulfides and sulfosalts in the distal veins formed in three distinct stages: (1) an early stage of pyrite and arsenopyrite, (2) a middle stage of sphalerite and chalcopyrite, and (3) a late stage of galena, Ag-, Sn-, and Bi-bearing sulfides and sulfosalts, and pyrrhotite. Combined sulfide and sulfosalt geothermometry and fluid inclusion analyses indicate that the early stage of mineralization occurred at a temperature of ~400 °C and involved boiling under hydrostatic pressure (~200 bar), with the temperature of the system dropping during the late stage to ~200 °C. Laser Raman analysis indicates that the fluid inclusions within the studied minerals are dominated by HO, although some contain carbonate solids and CH gas. Vein-hosted sulfides have δS values of 3.8-6.3‰ that are interpreted as indicative of a magmatic source of sulfur. The mineralization process can be summarized as follows: an aqueous fluid exsolved on final crystallization of the Qianlishan pluton, ascended along fracture zones, cooled to <400 °C, and boiled under hydrostatic conditions, and with decreasing temperature and sulfur fugacity, sulfide and sulfosalt minerals precipitated successively from the Ag-Cu-Zn-Fe-Pb-Sb-As-S-bearing fluid system. [ABSTRACT FROM AUTHOR]

The Meishan deposit (338 Mt at 39 % Fe) comprises massive ores in the main orebody and stockwork and disseminated ores along the main orebody. Four stages of mineralization and related alteration have been identified. The second stage of mineralization, which was the main stage of iron mineralization, formed stringer, disseminated iron ores, as well as the main Meishan orebody. The fourth stage formed small pyrite and/or gold orebodies above or alongside the main magnetite orebody. Stage 2 apatites have homogenization temperatures of 257-485 °C and salinities of 7.3-11 wt% NaCl. Calculated δO values of magnetite and apatite from the disseminated ores vary between 7.7 and 14.9 ‰, which is similar to values observed in the massive ores (8.1-12.9 ‰). The high-O fluids at Meishan have been interpreted as being of magmatic-hydrothermal origin. These fluids are indicative of the boiling of ore-forming fluids. Quartz, occurring as cavity fillings, gives homogenization temperatures from 202 to 344 °C, with most values lying between 250 and 330 °C. Corresponding salinities are ∼5 wt% NaCl. Calculated δO values are +6.4 to +6.8 ‰. These values indicate that the lower-temperature (250-330 °C) quartz was deposited from a cooling magmatic-hydrothermal fluid. Stage 3 siderites contain fluid inclusions that homogenized between 190 and 310 °C, mainly between 210 and 290 °C. Corresponding salinities are 4-8 wt% NaCl. Stage 4 quartz-carbonate veinlets contain fluid inclusions that homogenized at moderate to low temperatures (150-230 °C) and exhibit low salinities (2-10 wt% NaCl eq). δO values of the mineralizing fluids for the quartz and calcite can be calculated to vary from −0.7 to +5.6 ‰ and +6.3 to +10.2 ‰, respectively. While there is some overlap, the δO values of the fluids are generally lower than those observed in the massive and disseminated magnetite ores. δD values for the quartz and calcite vary between −154 and −123 ‰ and −123 and −111 ‰, respectively. These values suggest late-stage input of a shallow-sourced, isotopically light meteoric fluid at the temperature of pyrite and gold deposition. The fluid inclusion and stable isotope data indicate a cooling magmatic-hydrothermal system that progressed from isotopically heavy to isotopically depleted fluids as it cooled. Such fluid evolution is comparable with those of other Kiruna-type deposits worldwide. [ABSTRACT FROM AUTHOR]

Stable carbon (and when present, nitrogen) isotope ratios of fluid inclusions in quartz from selected gold deposits in Ghana and Zimbabwe have been analyzed using a crushing device interfaced to an isotopic ratio mass spectrometer (IRMS) in order to constrain possible sources of the auriferous fluids. The study revealed a striking difference in stable carbon isotopic compositions of CO in quartz-hosted fluid inclusions from Archean and Paleoproterozoic orogenic gold deposits and points to diverse sources of CO in the studied deposits. Whether this finding can be generalized for other Archean and Proterozoic orogenic gold deposits worldwide remains open. However, a significant CO contribution by mantle degassing can be ruled out for every deposit studied. Devolatilization of greenstone belt rocks is the most likely source for CO in some Archean Au deposits in Zimbabwe, whereas CO in Proterozoic vein-type Au deposits in the West African Craton is most likely derived from C-bearing metasedimentary rocks. The δC values of high-density CO-rich, water-poor inclusions hosted in quartz pebbles from the world-class Au-bearing conglomerate deposits at Tarkwa (Ghana) differ considerably from the δC values of similar high-density CO-rich inclusions in vein quartz from the giant Ashanti deposit (Ghana) and disprove the idea of derivation of the Tarkwaian quartz (and gold?) from an older equivalent to the Ashanti vein-type gold deposit. [ABSTRACT FROM AUTHOR]

The Yaochong porphyry Mo deposit in Xinxian County, Henan Province, China, is located in the Hong'an terrane, that is, the western part of the Dabie orogen. The Dabie orogen is part of a >1,500 km long, Triassic continental collision belt between the North China Block and the South China Block. Four types of vein are present. Paragenetically, from early to late, they are as follows: stage 1 quartz + K-feldspar ± pyrite ± magnetite vein; stage 2 quartz + K-feldspar + molybdenite ± pyrite vein; stage 3 quartz + polymetallic sulfides ± K-feldspar vein; and stage 4 quartz ± carbonate ± fluorite vein. Four compositional types of fluid inclusion, pure CO, CO bearing, aqueous, and solid bearing, are present in quartz from the first three stages; only low-salinity aqueous fluid inclusions occur in quartz from the last stage. All the estimated salinities are ≤13.1 wt% NaCl eq., and no halite crystals were identified. Homogenization temperatures for the fluid inclusions from stages 1 to 4 are in the ranges of 262-501, 202-380, 168-345, and 128-286 °C, respectively, and estimated depths decrease from 6.9 to 8.9 km, through 6.2-7.2, to ~4.7 km. Quartz separates from the veins yielded a δO value of 7.7-11.2 ‰, corresponding to δO values of −1.3 to 6.9 ‰ using temperature estimates from fluid inclusion data; δD values of fluid inclusion vary from −80 to −55 ‰, and δC from −2.3 to 2.7 ‰, suggesting that the ore-fluids evolved from magmatic to meteoric sources. We conclude that the ore-forming fluid system at Yaochong was initially high temperature, high salinity, and CO-rich and then progressively evolved to CO-poor, lower salinity, and lower temperature, by mixing with meteoric water, which results in ore precipitation. [ABSTRACT FROM AUTHOR]

The Yangla copper deposit, with Cu reserves of 1.2 Mt, is located between a series of thrust faults in the Jinshajiang-Lancangjiang-Nujiang region, Yunnan, China, and has been mined since 2007. Fluid inclusion trapping conditions ranged from 1.32 to 2.10 kbar at 373-409 °C. Laser Raman spectroscopy confirms that the vapour phase in these inclusions consists of CO, CH, N and HO. The gas phases in the inclusions are HO and CO, with minor amounts of N, O, CO, CH, CH, CH, and CH. Within the liquid phase, the main cations are Ca and Na while the main anions are SO and Cl. The oxygen and hydrogen isotope compositions of the ore-forming fluids (−3.05‰ ≤ δO ≤ 2.5‰; −100‰ ≤ δD ≤ −120‰) indicate that they were derived from magma and evolved by mixing with local meteoric water. The δS values of sulfides range from −4.20‰ to 1.85‰(average on −0.85‰), supporting a magmatic origin. Five molybdenite samples taken from the copper deposit yield a well-constrained Re-Os isochron age of 232.8 ± 2.4 Ma. Given that the Yangla granodiorite formed between 235.6 ± 1.2 Ma and 234.1 ± 1.2 Ma, the Cu metallogenesis is slightly younger than the crystallization age of the parent magma. A tectonic model that combines hydrothermal fluid flow and isotope compositions is proposed to explain the formation of the Yangla copper deposit. At first, westward subduction of the Jinshajiang Oceanic Plate in the Early Permian resulted in the development of a series of thrust faults. This was accompanied by fractional melting beneath the overriding plate, triggering magma ascent and extensive volcanism. The thrust faults, which were then placed under tension during a change in tectonic mode from compression to extension in the Late Triassic, formed favorable pathways for the magmatic ore-forming fluids. These fluids precipitated copper-sulfides to form the Yangla deposit. [ABSTRACT FROM AUTHOR]

The Sanshandao gold deposit, located at northwestern edge of the Jiaodong Peninsula, eastern North China Craton, is one of the largest gold deposits in the Jiaodong gold province. In the deposit, disseminated- and stockwork-style ores are hosted in Mesozoic granitoids. Mineralization and alteration are largely controlled by the regional Sanshandao- Cangshang fault. Sericite separated from alteration rocks in the mineralized zone yields an Rb-Sr isochron age of 117.6 ± 3.0 Ma. The ore-forming fluids in the Sanshandao gold deposit contain CO2-H2O-NaCl±CH4 with low to intermediate temperatures and low salinities. Microthermometric analysis shows that homogenization temperatures gradually decrease from the early mineralizing stage (258-416°C) to main mineralizing stage (180-321°C) and to late mineralizing stage (112-231°C). Homogenization temperatures from the same mineralizing stage are nearly same and do not show an increase with depth. The nature of the ore-forming fluids remains nearly the same over a 2000 m vertical depth interval. [ABSTRACT FROM AUTHOR]

The Jinshan gold deposit is located in the Neoproterozoic Jiangnan orogen between the Yangtze and Cathaysia blocks. Gold-bearing disseminated ores are associated with the earlier stage of NWW-trending ductile zone, and auriferous quartz vein-type ores show an intimate relationship with the later stage of NE-trending brittle-ductile zones. Fluid-inclusion studies were conducted on the quartz veins. Three types of fluid inclusions can be identified: H2O- CO2 inclusions (type I), CO2-rich inclusions (type II), and aqueous inclusions (type III). The pre-ore stage, quartz-pyrite veins primarily contain type I inclusions with constant CO2 bubble volumetric proportions. The main gold mineralization-stage veins have all three types of inclusions with variable gas-phase ratios and CO2 contents. The post-ore stage carbonate±chlorite veinlets only contain type III inclusions. Type I inclusions in the pre-ore stage display homogenization temperatures (Th) of 285-340°C, with salinities of 1.4-6.1 wt.% NaCl equivalent. In the main gold mineralization stage, type II and III inclusions show similar Th at 208-277°C, but contrasting salinity values with 0.6-3.6 and 3.5-8.9 wt.% NaCl equivalent, and type I inclusions show variable CO2-phase proportions and have Th of 241-292°C and salinities of 1.0-7.0 wt.% NaCl equivalent. In the post-ore stage, type III inclusions yield Th of 109-201°C and salinities of 1.1-6.4 wt.% NaCl equivalent. Petrological observations and microthermometric results show that fluid immiscibility primarily occurred during the gold mineralization stages. The oxygen and hydrogen isotope compositions (δ18 O = +6.9‰ to +11.2‰, δD = −71‰ to −46‰) of inclusion water in quartz grains imply that ore fluids were principally metamorphic in origin. The sulfur and lead values of sulfide from the ores are analogous to those from the basement strata, suggesting a predominantly crustal source of the ore sulfides. The Jinshan deposit is a typical orogenic gold deposit. [ABSTRACT FROM AUTHOR]

The Xihuashan tungsten deposit, Jiangxi province, China, is a world-class vein-type ore deposit hosted in Cambrian strata and Mesozoic granitic intrusions. There are two major sets of subparallel ore-bearing quartz veins. The ore mineral assemblage includes wolframite and molybdenite, with minor amounts of arsenopyrite, chalcopyrite, and pyrite. There are only two-phase aqueous-rich inclusions in wolframite but at least three major types of inclusions in quartz: two- or three-phase CO-rich inclusions, two-phase pure CO inclusions and two-phase aqueous inclusions, indicating boiling. Fluid inclusions in wolframite have relatively higher homogenization temperatures and salinities (239-380°C, 3.8-13.7 wt.% NaCl equiv) compared with those in quartz (177-329°C, 0.9-8.1 wt.% NaCl equiv). These distinct differences suggest that those conventional microthermometric data from quartz are not adequate to explain the ore formation process. Enthalpy-salinity plot shows a linear relationship, implying mixing of different sources of fluids. Although boiling occurred during vein-type mineralization, it seems negligible for wolframite deposition. Mixing is the dominant mechanism of wolframite precipitation in Xihuashan. δS values of the sulfides range from −1.6 to +0.1‰, indicative of a magmatic source of sulfur. δO values of wolframite are relatively homogeneous, ranging from +4.8‰ to +6.3‰. Oxygen isotope modeling of boiling and mixing processes also indicates that mixing of two different fluids was an important mechanism in the precipitation of wolframite. [ABSTRACT FROM AUTHOR]

Abstract  The Samgwang mine is located in the Cheongyang gold district (Cheonan Metallogenic Province) of the Republic of Korea. It consists of eight massive, gold-bearing quartz veins that filled NE- and NW-striking fractures along fault zones in Precambrian granitic gneiss of the Gyeonggi massif. Their mineralogy and paragenesis allow two separate vein-forming episodes to be recognized, temporally separated by a major faulting event. The ore minerals occur in quartz and calcite of stage I, associated with fracturing and healing of veins. Hydrothermal wall-rock alteration minerals of stage I include Fe-rich chlorite (Fe/(Fe) ratios 0.74-0.81), muscovite, illite, K-feldspar, and minor arsenopyrite, pyrite, and carbonates. Sulfide minerals deposited along with electrum during this stage include arsenopyrite, pyrite, pyrrhotite, sphalerite, marcasite, chalcopyrite, galena, argentite, pyrargyrite, and argentian tetrahedrite. Only calcite was deposited during stage II. Fluid inclusions in quartz contain three main types of C–O–H fluids: CO2-rich, CO2–H2O, and aqueous inclusions. Quartz veins related to early sulfides in stage I were deposited from H2O–NaCl–CO2 fluids (1,500–5,000 bar, average 3,200) with T htotal values of 200°C to 383°C and salinities less than about 7 wt.% NaCl equiv. Late sulfide deposition was related to H2O–NaCl fluids (140–1,300 bar, average 700) with T htotal values of 110°C to 385°C and salinities less than about 11 wt.% NaCl equiv. These fluids either evolved through immiscibility of H2O–NaCl–CO2 fluids as a result of a decrease in fluid pressure, or through mixing with deeply circulated meteoric waters as a result of uplift or unloading during mineralization, or both. Measured and calculated sulfur isotope compositions (δ34SH2S = 1.5 to 4.8‰) of hydrothermal fluids from the stage I quartz veins indicate that ore sulfur was derived mainly from a magmatic source. The calculated and measured oxygen and hydrogen isotope compositions (δ18OH2O = −5.9‰ to 10.9‰, δD = −102‰ to −87‰) of the ore-forming fluids indicate that the fluids were derived from magmatic sources and evolved by mixing with local meteoric water by limited water–rock exchange and by partly degassing in uplift zones during mineralization. While most features of the Samgwang mine are consistent with classification as an orogenic gold deposit, isotopic and fluid chemistry indicate that the veins were genetically related to intrusions emplaced during the Jurassic to Cretaceous Daebo orogeny. [ABSTRACT FROM AUTHOR]

The Linghu Au deposit is located within the northeastern part of the Xiaoqinling region in the southern margin of the North China Craton. Field investigations, cross-cutting relationships, and mineral paragenetic associations have identified three stages of hydrothermal activity. To determine the origin and evolution of ore-forming fluids, and better understand genesis of the Linghu Au deposit, we have undertaken a series of studies including fluid inclusion and He–Ar–H–O–S–Pb isotope systematics. Fluid inclusion study indicates that the early stage of gold mineralization was characterized by a high-temperature and low-salinity H2O–CO2–NaCl hydrothermal fluids that have δD values of – 82.0 to – 78.6‰ and δ18OH2O values of 5.3 to 6.4‰. The intermediate stage of gold mineralization involved moderate temperature H2O–CO2–NaCl hydrothermal fluids with δD and δ18OH2O values of – 92.7‰ to – 87.9‰ and – 1.4‰ to 0‰, respectively. Pyrite samples from this mineralization stage have 3He/4He and 40Ar/36Ar ratios of 0.26–0.31 Ra and 2834.7–4300.6, respectively. The last mineralization stage involved (low-temperature and low-salinity NaCl–H2O system of hydrothermal fluids with relatively lower δD values of – 93.1 to – 92.3‰ and δ18OH2O values of – 5.7 to – 5.2‰. Moreover, sulfides in ores yielded δ34S values of – 3.6 to 5.9‰, with an average of 2.65‰. The sulfides have 206Pb/204Pb ratios of 17.101–17.804, 207Pb/204Pb ratios of 15.438–15.554, and 208Pb/204Pb ratios of 37.438–38.654. The results of fluid inclusions and H–O, S–Pb, and He–Ar isotopes indicate that hydrothermal fluids associated with the early stage of mineralization originated from magmatic fluids, with sulfur and lead being derived from both units of the Taihua Group and a Late Triassic magmatic–hydrothermal system. All of these data indicate that the Linghu gold deposit formed as a result of magmatic–hydrothermal mineralizing processes. [ABSTRACT FROM AUTHOR]

The Pingshun skarn iron deposit is located in the southern Handan–Xingtai iron district of the southern Taihang Mountains, North China Craton. Skarns and ore bodies occur as lamina, lenses, and veins along the contact between a dioritic pluton and carbonates of the Middle Ordovician Majiagou Formation. The paragenetic sequence is albite followed by diopside, then garnet, magnetite, and finally calcite. Diorite and olivine-bearing hornblende gabbro in the Pingshun area contain zircon grains with SHRIMP U–Pb ages of 123.4 ± 1.7 and 125.5 ± 2.3 Ma, respectively. Based on the close spatial association between diorite and mineralization, we suggest that both magma activities and iron mineralization in the Pingshun area took place at 125–123 Ma. Three types of fluid inclusions identified in minerals from the Pingshun deposit include three-phase (type 1), two-phase (type 2), and pure liquid (type 3) inclusions. The ore-forming fluid evolved from high temperature (515–679 °C) with high salinity (39.8–77.6 wt% NaCl equiv.) in diopside, to medium–high temperature (365–496 °C) with moderate–low salinity (11.8–17.6 wt% NaCl equiv.) in garnet, and to low temperature (162–295 °C) with moderate–low salinity (6.7–35.5 wt% NaCl equiv.) in calcite. The presence of hematite, halite, and gypsum daughter minerals in type 1 fluid inclusions and the occurrence of andradite in skarns indicate that the pre-ore–forming fluid was oxidized. The δ34S values of pyrite separated from ores vary from 12.5 to 17.4‰, with 206Pb/204Pb = 17.26–19.03, 207Pb/204Pb = 15.42–15.69, and 208Pb/204Pb = 37.29–39.76, suggesting the ore-forming fluid was originated from a magmatic source and with additional crustal material during the mineralization process. This is consistent with H–O isotope data (δ18Odiopside-H2O = 10.8‰, δ18Ogarnet-H2O = 9.5–10.8‰, δ18Omagnetite-H2O = 9.8–13.4 ‰, δDgarnet varying from − 106 to − 86‰, δDdiopside = − 90‰). The microthermometry of fluid inclusions and isotope data reveal that the addition of gypsolyte and salt-bearing marlstone into the ore-forming fluid increases Na, Ca, and Cl and that it significantly increases the ability to transport Fe and enhances the capacity of Fe in the ore-forming fluid. Fluid boiling and additional meteoric water involved are two major key factors controlling the ore precipitation. Mantle materials involved in magma and high oxygen fugacity are considered to be crucial roles in the formation of numerous iron deposits in the Handan–Xingtai iron district. [ABSTRACT FROM AUTHOR]

The Angeer Yinwula Pb-Zn deposit of Inner Mongolia, China, is located in the Erlianhot-Dongwuqi metallogenic belt, which is considered to be the eastern part of the Central Asian Orogenic Belt. We used the ore geology, fluid inclusion, isotopes, and zircon U-Pb geochronology to elucidate the genesis and tectonic setting of the deposit. The deposit belongs to the moderate-temperature hydrothermal-vein type, and most of the ore bodies occurred in the quartz diorite intrusions and silty slate country rocks of the Devonian Angeer Yinwula Group. Fluid inclusion petrography and microthermometry results show that the inclusions that developed in the different mineralization stages changed from the LV type (vapor-rich two-phase) + S type (daughter-mineral-bearing three-phase) + VL type (liquid-rich two-phase) to the VL type + LV type and eventually evolved into the VL type, and the ore-forming fluids changed from a moderate-temperature and moderate- to high-salinity, boiling fluid system to a low-temperature and low-salinity H2O-NaCl system. The isotope (C, H, O, S) characteristics suggest that the ore-forming fluids were derived from a magmatic source, and the lead was derived from a deep-seated mantle-derived magma and also included some crustal material. The LA-ICP-MS zircon U-Pb age of the quartz diorite is 152.0 ± 1.5 Ma, which is the best estimate for the age of mineralization of the deposit. Overall, we suggest that the deposit formed in a Late Jurassic Paleo-Pacific Plate subduction setting, although this hypothesis needs to be further tested by conducting computational simulations in the field of emerging computational geosciences. [ABSTRACT FROM AUTHOR]

The Zhuangzi Au deposit in the world-class Jiaodong gold province hosts visible natural gold, and pyrite as the main ore mineral, making it an excellent subject for deciphering the complex hydrothermal processes and mechanisms of gold precipitation. Three types of zoned pyrite crystals were distinguished based on textural and geochemical results from EPMA, SIMS sulfur isotopic analyses and NanoSIMS mapping. Py0 has irregular shapes and abundant silicate inclusions and was contemporaneous with the earliest pyrite-sericite-quartz alteration. It has low concentrations of As (0-0.3 wt.%), Au and Cu. Py1 precipitated with stage I mineralization shows oscillatory zoning with the bright bands having high As (0.4-3.9 wt.%), Au and Cu contents, whereas the dark bands have low contents of As (0-0.4 wt.%), Au and Cu. The oscillatory zoning represents pressure fluctuations and repeated local fluid phase separation around the pyrite crystal. The concentration of invisible gold in Py1 is directly proportional to the arsenic concentration. Py1 is partially replaced by Py2 which occurs with arsenopyrite, chalcopyrite and native gold in stage II. The replacement was likely the result of pseudomorphic dissolution-reprecipitation triggered by a new pulse of Au-rich hydrothermal fluids. The δ34S values for the three types of pyrite are broadly similar ranging from + 7.1 to + 8.8‰, suggesting a common sulfur source. Fluid inclusion microthermometry suggests that extensive phase separation was responsible for the gold deposition during stage II mineralization. Uranium-Pb dating of monazite constrains the age of mineralization to ca. 119 Ma coincident with a short compressional event around 120 Ma linked to an abrupt change in the drift direction of the subducting Pacific plate. [ABSTRACT FROM AUTHOR]

The article discusses a study on gold mineralization in the Tiemurte Volcanogenic massive sulfide (VMS) ore deposits and its evidences from fluid inclusions and geology. Topics discussed include occurrence of copper and gold in the Volcano-sedimentary Basin of the southern Altaides, characterization of fluid inclusions in vein quartz from gold ore bodies by carbon dioxide rich inclusions, and contribution of orogenic metamorphic in modified VMS deposit.