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Skarn Au deposits exist in the circum-pacific metallogenic belt. Interestingly, the Da'anhe Au deposit is the only independent skarn gold deposit in the Lesser Xing'an Range. To determine the metallogenic mechanism and prospecting potential of the Da'anhe deposit, we performed skarn mineralogy, fluid inclusion (FI) and H-O isotope analyses. The results show the following: (1) The Da'anhe deposit is a calcareous reduced skarn Au deposit that formed between an Early Jurassic gabbroic diorite and the Permian Tumenling Formation marble. Its metallogenic process includes five stages: the early skarn stage (Stage I1), late skarn stage (Stage I2), early quartz-sulfide stage (Stage II1), late quartz-sulfide stage (Stage II2) and quartz-carbonate stage (Stage II3). Gold precipitated in Stage II1 and Stage II2. (2) The initial ore-forming fluid was derived from magmatic water and featured a high temperature and intermediate to high salinity. After boiling and mixing, the fluid eventually changed to a low-temperature and low-salinity reducing fluid dominated by meteoric water. (3) The formation depth of the Au orebodies was 2.27–3.11 km, and the orebodies were later lifted to the surface (<500 m). The potential for finding skarn Au deposits in the study area is limited. (4) The distinctive nature of the ore-related magma (i.e., source, reducing conditions and high water content) was key to the formation of the Da'anhe skarn gold deposit. [ABSTRACT FROM AUTHOR]

The Early Cretaceous Weideshan granites are associated with large-scale Au and polymetallic Cu-Mo-Pb-Zn mineralization. To investigate the petrogenesis of the Weideshan granite and constrain its tectonic setting during the Early Cretaceous, we conducted a zircon U-Pb-Hf isotope and whole-rock geochemical and Sr-Nd isotopic study of the granite. In situ zircon U-Pb dating of three granite samples yielded Early Cretaceous ages of 112.83 ± 0.80, 112.64 ± 0.91, and 111.82 ± 0.78 Ma. The samples had high-K calc-alkaline compositions and were enriched in the light rare earth and large-ion lithophile elements (e.g., K, Rb, Ba, Th, and U) and depleted in high-field-strength elements (e.g., Nb, Ti, and P). The samples had small negative Eu anomalies and initial 87Sr/86Sr and εNd(t) values of 0.70853–0.71029 and –18 to –14, respectively. The zircon εHf(t) values varied between −16 and −12, with corresponding two-stage model ages (tDM2) of 2180–2000 Ma. These characteristics indicated that the Weideshan pluton was formed in a back-arc extensional environment caused by subduction of the Paleo-Pacific Plate toward the Asian continent during the early Cretaceous. The magma was generated by crust–mantle interaction during lithospheric thinning. The diagenetic age of the Weideshan granites was the same as the formation age of gold and polymetallic ores in the Jiaodong area. The extensive fluid circulation induced by the magma emplacement may be the main source of ore-forming materials for the gold and polymetallic Cu-Mo-Pb-Zn deposits. [ABSTRACT FROM AUTHOR]

The Luxi district presents an exceptional research area for the investigation of the significant role played by magma exsolution fluids in the mineralization process of Au–Cu deposits. A particularly noteworthy occurrence within this region is the Yi'nan Tongjing Au–Cu skarn deposit, situated in the central-southern part of the Luxi district. This deposit primarily occurs in the contact zone between the early Cretaceous Tongjing complex and the Proterozoic to Cambrian sequences. The ore formation process observed in this deposit can be categorized into three distinct stages: (I) thermal metamorphism, (II) prograde alteration, and (III) retrograde alteration. The retrograde alteration stage is further divided into four sub-stages: late skarn (III-1), oxide (III-2), sulfide (III-3), and late quartz-calcite (III-4). It is primarily during the III-3 sub-stage that gold mineralization occurs. Petrographic analysis has identified three types of fluid inclusions (FIs) within garnet, quartz, and calcite grains. These include liquid-rich two-phase aqueous FIs, vapor-rich two-phase aqueous FIs, and halite-bearing multi-phase FIs. The homogenization temperatures of fluid inclusions from stages II, III-3, and III-4 range between 430–457 °C, 341–406 °C, and 166–215 °C (first to third quartiles), respectively. The garnet samples from stage II exhibit hydrogen and oxygen isotope compositions (δ18OH2O = 6.8‰ and δD = −73‰) that are indicative of a typical magma source. However, the hydrogen and oxygen isotopes of sub-stages III-1, III-2, and III-3 (δ18OH2O = 7.32‰ to 9.74‰; δD = −107‰ to −81.9‰) fall below the magma water box while the hydrogen and oxygen isotope values of III-4 (δ18OH2O = −5.3‰ to −0.9‰ and δD = −103.8‰ to −67‰) tend to move towards the meteoric water line. Furthermore, the ore-forming fluid displays characteristics of a mixture between the crustal and mantle fluids. The Tongjing complex occurred along a weakened fault zone, initiating a process of thermal metamorphism upon contact with the wall rock. This thermal metamorphism resulted in the formation of diverse assemblages, including hornfels, reaction skarns, and skarnoids. Subsequently, the upward movement of ore-forming fluids triggered exsolution which led to the establishment of a high-temperature, medium-salinity NaCl–H2O system with a single phase at depths ranging from 1–3 km. This marked the formation of the prograde alteration stage. Afterward, the ore-forming fluid underwent water–rock interactions and the admixture of meteoric water at a depth of 1–2 km. These processes facilitated phase separation, commonly referred to as boiling, resulting in the transformation of the ore-forming fluid into higher salinity fluids and lower-density gases. This evolutionary transition ultimately induced the precipitation and liberation of gold and copper from the fluid. [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]

The medium-sized Songjianghe Au deposit is located in the southeastern part of the Jiapigou-Haigou gold belt (JHGB) in central eastern Jilin Province, NE China. The gold mineralization is primarily characterized by disseminated-style ores and hosted in the low-/medium-grade metamorphic rocks of the Seluohe Group. The ore bodies are governed by NNW-striking brittle-ductile structures and spatially correlated with silicic and sericitic alterations. Four alteration/mineralization stages have been distinguished: (I) Quartz-pyrrhotite-pyrite, (II) quartz-polymetallic sulfides, (III) quartz-pyrite, and (IV) quartz-calcite. The fluid inclusion (FI) assemblage in quartz from Stage I comprises C1-type, C2-type, C3-type, and VL-type FIs, with total homogenization temperatures (Th-total) of 292.8 to 405.6 °C and salinities of 2.8 to 9.3 wt% NaCl eqv. Quartz from Stage II (main ore stage) developed C2-, C3-, and VL-type FIs, with a Th-total of 278.5 to 338.9 °C and salinities of 2.8 to 8.1 wt% NaCl eqv. Stage III is characterized by coexisting C3- and VL-type FIs in quartz, with a Th-total of 215.9 to 307.3 °C and salinities of 2.4 to 7.2 wt% NaCl eqv. Only VL-type FIs are observed in Stage IV, with a Th-total of 189.5 to 240.4 °C and salinities of 3.7 to 5.7 wt% NaCl eqv. The Laser Raman spectroscopic results demonstrated minor CH4 in the C-type FIs from Stages I and II. The results suggest that ore fluids may have evolved from a medium-high temperature, low-salinity immiscible CO2-NaCl-H2O ± CH4 system to a low temperature, low-salinity homogeneous NaCl-H2O system. Fluid immiscibility caused by the rapid drop in pressure may have been the main trigger for gold-polymetallic sulfide precipitation. The Songjianghe Au deposit may have been formed under 352–448 °C and 850–1380 bar pressure, based on the isochore intersection for Stage II fluid inclusions. The H-O isotopic compositions (Stage I: δ18Ofluid = 5.6 to 5.8‰, δD = −96.2 to −95.7‰; Stage II: δ18Ofluid = 3.7 to 4.2‰, δD = −98.7 to −89.8‰; Stage III: δ18Ofluid = 1.2 to 1.4‰, δD = −103.5 to −101.2‰) indicate that the hydrothermal fluids are dominated by magmatic water in the early stages (Stages I and II) and mixed with meteoric water since Stage III. The pyrite S-Pb isotope data (δ34S: −2.91 to 3.40‰; 206Pb/204Pb: 16.3270 to 16.4874; 207Pb/204Pb: 15.2258 to 15.3489; 208Pb/204Pb: 36.6088 to 36.7174), combined with Pb isotopic compositions of the intrusive rocks and wall rocks (the Seluohe Group) in the ore district, indicate that the ore-forming materials at Songjianghe are predominantly from a magmatic source and may have been affected by the contamination of the Seluohe Group. In accordance with the features of ore geology, ore-forming fluids and metals, and geodynamic setting, the Songjianghe Au deposit belongs to a mesothermal magmatic hydrothermal vein gold deposit, which formed in the intermittent stage of Paleo-Pacific plate subduction during the Late Jurassic. [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 Dongpuzi deposit is an epithermal gold deposit located in the southern margin of the Shaozihe volcanic fault basin in the Liaodong Peninsula. On the basis of fluid inclusion and C–H–O–S–Pb isotope data, a metallogenic model is established for the Dongpuzi deposit. The mineralization at the Dongpuzi deposit has experienced quartz–pyrite (I), quartz–sulfide (II), and quartz–calcite (III) stages. The quartz from ore stage II has liquid-dominated aqueous inclusions, which have homogenization temperatures ranging from 113 to 162 °C and salinities varying from 3.2 to 9.6 wt% NaCl equiv. The quartz from the quartz–calcite stage has decreasing homogenization temperatures (106~143 °C) and salinities (2.7~6.9 wt% NaCl equiv.). The fluid inclusion data indicate that the gold ores were precipitated from low-temperature and low-salinity solutions, with an obvious decrease in temperature and salinity from ore stages II to III. The calculated δ18Owater values for the quartz of ore stage II range from −14.71‰ to −13.31‰, and the corresponding δDwater values range from −103.3‰ to −96.1‰, indicating that the ore-forming fluids could be of a meteoric origin. The calcite from ore stage III has δ13CV-PDB values of −4.5‰ to −4.2‰ and δ18OV-SMOW values of +7.0‰ to +7.4‰, indicating a mantle source for the carbon. The pyrite yielded δ34S values of +4.1‰ to +6.6‰ and Pb isotopes consistent with those of the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, which suggests that the S and Pb in gold ores were dominantly derived from the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, with some combination of Paleoproterozoic metamorphic rocks of the Gaixian Formation. These results, together with the ore geology, indicate that the Dongpuzi deposit is a typical low-sulfidation epithermal gold deposit with important ore-forming materials input from the host trachyte porphyry, volcanic rocks of the Xiaoling Formation, and Paleoproterozoic metamorphic rocks of the Gaixian Formation. The Dongpuzi deposit was formed under an extensional setting related to the Early Cretaceous lithospheric extension and thinning of the eastern North China Craton. [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 Changkeng–Fuwan Au-Ag deposit is representative in South China, which is located in the southwest of the Qin–Hang metallogenic belt (QHMB). The Au and Ag orebodies are located in the same altered fracture zone, forming independent gold and silver orebodies respectively, with the characteristics of "upper gold and lower silver" in space. Three metallogenic stages have been identified: the pyrite–quartz–sericite stage, the polymetallic sulfide stage, and the quartz–calcite stage. The fluid inclusions (FIs) from the deposit are the two-phase liquid-rich (type I) and the pure liquid FIs (type II). The microthermometric measurements of type I FIs are characterized by temperatures of 158–282 °C and 146–289 °C and salinities of 0.35–9.88 wt.% NaCl equiv. and 0.18–11.70 wt.% NaCl equiv. The H, O, He, and Ar isotopic data show that the ore-forming fluids of the deposit were derived from a mixture of magmatic and meteoric fluids. The C and O isotopic data suggest that the carbon of the fluid may derive from a magmatic source. The S and Pb isotopic data indicate that the primary source of the metals in the Changkeng–Fuwan deposit may be a magma source. Based on the geological characteristics, FI microthermometry, and isotope data (C, H, O, He, Ar, S, and Pb), we propose that the Changkeng–Fuwan deposit should be classified as a far-source low-temperature magmatic–hydrothermal deposit. [ABSTRACT FROM AUTHOR]

Ti-isotope fractionation on the most Ti-rich minerals on Earth has not been reported. Therefore, we present a chemical preparation and separation technique for Ti-rich minerals for mineralogic, petrologic, and economic geologic studies. A two-stage ion-exchange column procedure modified from the previous literature is used in the current study to separate Ti from Fe-rich samples, while α-TiO2 does not require chemical separation. Purified solutions in conjunction with solution standards were measured on two different instruments with dry plasma and medium-resolution mode providing mass-dependent results with the lowest errors. 49/47TiOL-Ti for the solution and solids analyzed here demonstrate a range of >5 ‰ far greater than the whole procedural 1 error of 0.10 ‰ for a synthetic compound and 0.07 ‰ for the mineral magnetite; thus, the procedure produces results is resolvable within the current range of measured Ti-isotope fractionation in these minerals. [ABSTRACT FROM AUTHOR]

The Shanmen Ag deposit, located in the southeastern part of the Siping area, Jilin Province, is one of the large-scale Ag deposits in Northeastern (NE) China. Almost all Ag orebodies, Ag-bearing quartz-sulfide veins are strictly controlled by NE-trending faults or brittle fractures and are hosted in the Yanshanian monzonite and quartz diorite. In terms of deposit geology, three mineralization stages are recognized: the pyrite-quartz stage (I), the quartz-Ag-polymetallic sulfide stage (II), and the carbonate-quartz stage (III). The research results of the fluid inclusions in the different stages indicate that the early stage (Stage I) mainly contains three types of fluid inclusions: liquid-rich two-phase (L-type), vapor-rich two-phase (V-type), and CO2 aqueous multi-phase (C-type). The fluid belongs to a medium–high temperature and medium–low salinity H2O-NaCl-CO2 system and has boiling characteristics. The middle stage (Stage II) is mainly characterized by liquid-rich two-phase (L-type) and vapor-rich two-phase (V-type) inclusions, in which the mixing of fluids of different nature leads to the escape of CO2. Only liquid-rich two-phase (L-type) inclusions are distinguished in the late stage (Stage III). The fluids of two later stages belong to the medium-low-temperature and low-salinity H2O-NaCl system. Homogenization temperatures from the early to late stages range from 272.2 to 412.5 °C, 124.1 to 313.3 °C, and 128.6 to 224 °C, respectively. Fluid salinities in the early to late stages range from 1.6 to 12.1, 1.4 to 8.9, and 0.4 to 5.8 wt.% NaCl equivalent, respectively. The gradually decreasing trends of homogenization temperatures and salinities and the reduction in the CO2 content indicate that the release of CO2 and the low-temperature environment are important causes of the precipitation of Ag-bearing minerals. The δ18OH2O values of the ore-bearing quartz veins in the different stages range from −3.7 to +8.1‰, and the δD values of fluid inclusions in the quartz range from −113 to −103‰, indicating that the initial ore-forming fluid was mainly derived from magma and that the input of meteoric water gradually increased during the mineralization process. The δ34S values (ranging from −11.4‰ to +1.8‰) and Pb isotope compositions (206Pb/204Pb = 18.143–18.189, 207Pb/204Pb = 15.543–15.599, 208Pb/204Pb = 38.062–38.251) of sulfides suggest that the ore-forming materials have mixed mantle and crustal sources. Therefore, we propose that the release of CO2 and the low-temperature environment are important conditions for silver minerals precipitation, and the mixing of fluids of different nature is the dominant mechanism causing precipitation. The Shanmen Ag deposit can be classified as an intrusion-related medium–low temperature hydrothermal vein-type deposit. [ABSTRACT FROM AUTHOR]

The Liyuan gold deposit, located in the central Taihang Mountains, North China Craton, forms an important part of the Taihang polymetallogenic belt. The origin of ore-forming fluids and the genesis of this deposit remains controversial. In this paper, fluid inclusions (FIs) microthermometry and H-O-S isotopes analysis are conducted to constrain the origin of ore-forming fluids and genesis. The main findings are as follows: (1) Three hydrothermal metallogenic stages are identified: Quartz–pyrite, quartz–polymetallic sulfide, and quartz–carbonate stages; (2) three types of primary FIs are recognized: CO2-aqueous (type I), pure CO2 (type II), and aqueous FIs (type III); (3) ore-forming fluids are characterized by medium–low temperatures, medium–low salinity, and H2O-CO2-NaCl ± CH4 system; (4) H-O isotopes indicate that the ore-forming fluids mainly have a magmatic origin and late-stage ore fluids mixed with meteoric water; (5) S isotopes further confirm that the sulfides most likely have a deep magma source with variation caused by changes in oxygen fugacity; and (6) fluid immiscibility and water–rock interactions are considered to be the two main mechanisms of gold deposition. Due to the lack of large granite bodies exposed in this ore district, we infer that the fluids of gold deposit and quartz porphyry may have both been exsolved from a concealed granite pluton at deeper locations, and we further propose that Liyuan gold deposit is typical magmatic–hydrothermal gold deposits. [ABSTRACT FROM AUTHOR]

The Reshui porphyry Mo deposit is located in the East Kunlun orogenic belt (EKOB). Molybdenum mineralization is distributed in monzogranite and porphyritic monzogranite rocks, mainly presenting as various types of hydrothermal veinlets in altered wall rocks, and the orebodies are controlled by three groups of fractures. In this paper, we present the results of fluid-inclusion and isotopic (S and Pb) investigations of the Reshui Mo deposit. The ore-forming process of the deposit can be divided into three stages: an early disseminated molybdenite stage (stage 1), a middle quartz–molybdenite stage (stage 2) and a late quartz–polymetallic sulfide stage (stage 3). The alteration was mainly potassic and silicic in stage 1, silicic in stage 2, and sericitic and silicic in stage 3. Five types of fluid inclusions (FIs) can be distinguished in quartz phenocrysts and quartz veins, namely W, PL (pure liquid inclusions), PV (pure gas inclusions), C (CO2 three-phase inclusions), and S (daughter mineral-bearing inclusions). The homogenization temperatures of fluid inclusions belonging to stages 1 to 3 are 282.3–378 °C, 238.7–312.6 °C and 198.3–228 °C, respectively. The fluid salinities at stages 1 to 3 are 4.65–8.14% NaCl eq., 4.34–42.64% NaCl eq., and 3.55–4.65% NaCl eq., respectively. The fluids of this deposit were generally moderate–high temperature and moderate–low salinity and belong to the H2O–NaCl–CO2 ± CH4 system. The temperature and pressure changed considerably between stage 2 (high–medium-temperature) and stage 3 (low-temperature). The evidence for ore-forming fluids containing different types of coexisting inclusions in stage 2 and a decrease in the fluid temperature from stage 2 to stage 3 indicate that fluid boiling and fluid mixing were the main mechanisms of ore precipitation. The sulfide 34SV-CDT values range from 4.90‰ to 5.80‰, which is characteristic of magmatic sulfur. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb values of the ore minerals are 18.210–18.786, 15.589–15.723, and 38.298–39.126, respectively. These lead isotopic compositions suggest that the ores were mainly sourced from crustally derived magmas, with minor input from the mantle. The fluid inclusions and S–Pb isotopes provide important information on the genesis of the Reshui porphyry Mo deposit and indicate that the Triassic has high metallogenic porphyry potential in the EKOB. [ABSTRACT FROM AUTHOR]

The Chuduoqu Pb-Zn-Cu deposit is located in the Tuotuohe area in the northern part of the Sanjiang Metallogenic Belt, central Tibet. The Pb-Zn-Cu ore bodies in this deposit are hosted mainly by Middle Jurassic Xiali Formation limestone and sandstone, and are structurally controlled by a series of NWW trending faults. In this paper, we present the results of fluid inclusions and isotope (C, H, O, S, and Pb) investigations of the Chuduoqu deposit. Four stages of hydrothermal ore mineralization are identified: quartz–specularite (stage I), quartz–barite–chalcopyrite (stage II), quartz–polymetallic sulfide (stage III), and quartz–carbonate (stage IV). Two types of fluid inclusions are identified in the Chuduoqu Pb-Zn-Cu deposit: liquid-rich and vapor-rich. The homogenization temperatures of fluid inclusions for stages I–IV are 318–370 °C, 250–308 °C, 230–294 °C, and 144–233 °C, respectively. Fluid salinities range from 2.07 wt. % to 11.81 wt. % NaCl equivalent. The microthermometric data indicate that the fluid mixing and cooling are two important mechanisms for ore precipitation. The H and O isotopic compositions of quartz indicate a primarily magmatic origin for the ore-forming fluids, with the proportion of meteoric water increasing over time. The C and O isotopic compositions of carbonate samples indicate that a large amount of magmatic water was still involved in the final stage of mineralization. The S and Pb isotopic compositions of sulfides, demonstrate that the ore minerals have a magmatic source. On a regional basis, the most likely source of the metallogenic material was regional potassium-enriched magmatic hydrothermal fluid. Specifically for the Chuduoqu Pb-Zn-Cu deposit, the magmatic activity of a syenite porphyry was the likely heat source, and this porphyry also provided the main metallogenic material for the deposit. Mineralization took place between 40 and 24 Ma. The Chuduoqu deposit is a mesothermal hydrothermal vein deposit and was formed in an extensional environment related to the late stage of intracontinental orogenesis resulting from India–Asia collision. The determination of the deposit type and genesis of Chuduoqu is important because it will inform and guide further exploration for hydrothermal-type Pb and Zn deposits in the Tuotuohe area and in the wider Sanjiang Metallogenic Belt. [ABSTRACT FROM AUTHOR]