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A large amount of distal skarn Pb–Zn deposits without any causative intrusions exposed have been discovered along the eastern Nyainqêntanglha metallogenic belt (NMB) in the Gangdese region, Tibet, China. As a typical distal skarn Pb–Zn deposit in the east of NMB, the Mengya'a deposit is adjacent to the Longmala Pb–Zn ± Cu ± Fe deposit. However, the linkage between these two deposits is not unclear due to the chaotic dating results. In situ Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA‐ICP‐MS) U–Pb dating of reddish‐brown and yellow‐green garnet from Mengya'a yielded lower intersect ages of 53.6 ± 3.1 and 52.4 ± 4.4 Ma, respectively, indicating that Pb–Zn mineralization took place during the main collision stage of the India–Asia plates. The δDSMOW values of garnet, quartz and calcite vary from −148.4‰ to −140.4‰, −123.5‰ to −115.3‰ and −127.9‰ to −121.3‰, with the δ18OH2O values ranging from 5.8‰ to 6.6‰, 0.4‰ to 3.7‰ and 1.0‰ to 1.7‰, respectively. The δ13CV‐PDB and δ18OSMOW values of calcite range from −8.2‰ to −4.7‰ and 9.8‰ to 18.6‰, respectively. These C–H–O isotopic compositions of hydrothermal minerals indicate that the ore‐forming fluids were initially derived from the magmatic water with progressive input of meteoric water from the prograde stage to the retrograde stage. The 87Sr/86Sr(53 Ma) ratios of sphalerite (0.72321–0.73474) are consistent with those of Ando gneiss in the Lhasa‐Golmud area, indicating that the basement gneiss makes a great contribution for the source of ore‐forming materials. The newly obtained garnet U–Pb ages at Mengya'a are consistent with those of mineralization and causative intrusion in the Longmala Pb–Zn ± Fe ± Cu deposit, suggesting that the Mengya'a and Longmala deposits constitute an integrated distal skarn‐type system. This proposed hypothesis suggests that the Fe–Cu ± Pb ± Zn mineralization within the contact zone should focus on the locations beneath the identified Pb–Zn orebodies at Longmala and Pb‐21 orebody at Mengya'a. [ABSTRACT FROM AUTHOR]

The Tabei Pb–Zn deposit is located adjacent to the well‐known Axi low‐sulphidation epithermal Au deposit in the Tulasu Basin, Chinese Western Tianshan. The homogenization temperatures and salinities of H2O‐rich biphase inclusions in ore‐stage sphalerite and calcite from Tabei range from 100 to 170°C and 0.4 to 6.2 wt% NaCleq, respectively. The δ13CV‐PDB and δ18OV‐SMOW values of calcite range from 0.9‰ to 1.5‰ and 5.6‰ to 6.7‰, respectively. The δ18OH2O and δDH2O values of hydrothermal fluids vary from −7.0‰ to −5.9‰ and −120.8‰ to −111.1‰, respectively. The in‐situ δ34SV‐CDT values of sulphides range from 7.5‰ to 8.0‰ (average 7.7‰). The in‐situ Pb isotopic compositions of galena and (87Sr/86Sr)0 ratios of sphalerite resemble those of Au‐bearing pyrite and quartz of Axi deposit, respectively, as well as the ore‐hosting volcanic rocks. These isotopic compositions indicate that the ore metals were derived from the ore‐hosting volcanic rocks, with the ore‐forming fluids consisting predominantly of circulating meteoric water. The absence of coexisting two‐phase vapour and liquid fluid inclusions and the presence of abundant banded coarse‐grained quartz crystals with dog tooth and comb textures at Tabei, suggest that the sulphides precipitated slowly due to conductive cooling. The high sulphide abundance, sulphide assemblage (pyrite + Fe‐poor sphalerite + galena + chalcopyrite), ore textures and isotopic compositions suggest that Tabei represents an intermediate‐sulphidation epithermal deposit. The Axi‐Tabei Au–Pb–Zn epithermal system constitutes a hybrid consisting of Au veins at shallow level and Pb–Zn veins at depth, suggesting that the base metals remain highly prospective beneath the identified Au orebodies at Axi. [ABSTRACT FROM AUTHOR]

The Jiamante Au deposit is one of the important deposits in the Axi ore cluster of the Western Tianshan, Xinjiang. The orebodies occurring mainly as quartz‐sulphide veins are hosted in Late Devonian volcanoclastic rocks and granitic porphyries, and structurally controlled by a group of NNW‐ and NNE‐ trending extensional faults and volcanic breccias. Primary metallic minerals are chalcopyrite, galena, pyrite, sphalerite, and native gold, with minor amounts of bismuthinite and bismuth. Nonmetallic minerals are dominated by quartz, sericite, chlorite, and calcite. Medium to low temperature hydrothermal alterations are well developed and characterized by silicification, beresitization, phyllic alteration, and chloritization. Two hydrothermal stages were identified: (a) the main‐ore quartz‐sulphide stage; and (b) the post‐ore quartz‐calcite stage. Microthermometric measurements indicate that the primary biphase liquid‐rich aqueous fluid inclusions within quartz of the main‐ore stage homogenize at temperatures (Th) of 176 to 251°C and have salinities of 2.1 to 7.4 wt% NaCleqv. A lower range of homogenization temperatures (169 to 212°C) and salinities (1.6 to 5.2 wt% NaCleqv) were obtained in calcite of the post‐ore stage. The fluid characteristics of moderate to low temperatures and salinities imply that the ore‐forming process occurred in an epithermal environment. In addition, there is a positive relationship between Th and salinities consistent with the fluid mixing trend. Together with H–O isotopic data (δDH2O = −118 to −97‰ and δ18OH2O = −5.5 to −1.6‰) and fluid characteristics, it is suggested that the ore‐forming fluids were a mixture of magmatic and meteoric waters. The δ13C values for CO2 in the hydrothermal fluids range from −3.2 to −2.7‰, and the sulphides have δ34S values of −5.2 to 2.9‰ with relatively uniform Pb isotopic compositions (206Pb/204Pb = 18.228 to 18.287, 207Pb/204Pb = 15.574 to 15.617, and 208Pb/204Pb = 38.151 to 38.251), indicating that the ore‐forming materials were magmatic sources that were derived directly from magmatic fluids and/or leached from volcanic‐subvolcanic rocks by hydrothermal fluids. Combined with the evidence from the mineralization and alteration, fluid inclusions, and C–H–O–S–Pb isotopes suggest that the Jiamante deposit is an intermediate‐sulphidation epithermal Au deposit. A combination of fluid mixing and fluid–rock interactions is inferred as the important factors causing ore deposition. According to the close spatial and temporal relationship between intermediate‐epithermal deposits and porphyry deposits, it is further suggested that porphyry‐type mineralization should have a good potential at the deep sites of the Jiamante deposit and its vicinity. [ABSTRACT FROM AUTHOR]

The Tulasu Basin is an important epithermal gold ore cluster situated in the Boluokenu Polymetallic Belt, Western Tianshan, China. The Axi Au, Tabei Pb–Zn, and Tawuerbieke Au deposits in this basin represent different types of epithermal mineralization. These are products of the same tectonic‐magmatic‐hydrothermal event, related to the southward subduction of the North Tianshan Ocean beneath the Yili‐Central Tianshan Plate during the Late Devonian to Early Carboniferous. The spatial relationships, preservation levels, and evolution of the three deposits are still debated. Hence, systematic geological field investigations, ore microscopy, and isotopic analyses were carried out on these three deposits. The S–Pb–C–H–O isotopic compositions indicate that the ore‐forming components were derived from the volcanic‐subvolcanic rocks, as well as from circulating meteoric waters. The occurrence of adularia, silicified platy carbonates, and quartz characterized by crustiform/colloform/colloidal textures at Axi indicate that boiling was the main precipitation mechanism for the Au mineralization. The Pb–Zn ores from Tabei are characterized by abundant banded coarse‐grained quartz crystals with dog tooth and comb textures, suggesting that the sulphides precipitated slowly due to conductive cooling. The Tawuerbieke Au deposit is characterized by pervasive silicification and phyllic alteration accompanying veinlet and disseminated ore, which formed via metasomatic water–rock interaction. According to the ore textures, intrusion sizes, and mineral assemblages, it can be inferred that all three deposits experienced different extents of erosion (Axi < Tabei < Tawuerbieke) and that there is exploration potential for concealed porphyry Cu–Au mineralization. Exploration should focus on deep targets beneath the Tawuerbieke Au deposit. [ABSTRACT FROM AUTHOR]

[Display omitted] • Garnet LA-ICP-MS U Pb dating yielded a lower-intersect age of 268.6 ± 5.9 Ma. • The initial hydrothermal fluids are magmatic water, mixing with meteoric water. • Arqiale is classified as a distal skarn Pb Zn Cu deposit. • Arqiale underwent two stage exhumation events in the Mesozoic and Cenozoic. • The causative intrusions and Cu mineralization may occur at depth in the north. The Arqiale Pb Zn Cu deposit is located in the Wusun Range, Western Tianshan, China. Prograde and retrograde skarn minerals are abundant and associated with the Pb Zn Cu mineralization. Given that the orebodies are stratabound and hosted in limestone and causative intrusions were not identified, the genetic relationship between mineralization and magmatic hydrothermal activity remains controversial. Geology, in-situ garnet LA-ICP-MS U Pb dating and S Pb C H O isotopes were carried out in this study, aiming to constrain the mineralization age, source of ore-forming components, and examine the link between mineralization and magmatism. In-situ garnet LA-ICP-MS U Pb dating yielded a well-defined lower-intercept age of 268.6 ± 5.9 Ma, reflecting that the mineralization occurred much younger than that of ore hosting strata and formed in a post-collisional setting. In-situ δ34S values of sulfides (chalcopyrite, sphalerite and pyrite) range from −5.81‰ to −7.57‰ with an average of −6.37‰. The δ34S values of sulfide separates published previously vary from −7.1‰ to 1.3‰ (average −1.5‰). The in-situ 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of galena vary from 18.262 to 18.269, 15.561 to 15.567 and 38.049 to 38.065, respectively. The aforementioned S-Pb isotopic compositions indicate that the metals and sulfur were sourced partially from causative intrusion and partially from hosing sedimentary rocks. The δ13C (-2.6 – −0.9‰), δ18O V-SMOW (3.2 – 7.7‰), δ18O H2O (-5.2 – −0.7‰) and δD H2O (-128.0 – −109.1‰) values of ore-bearing calcite suggest that the ore-forming fluids were initially sourced from magmatic water exsolved from the hidden causative intrusions, with increasing input of meteoric water in later time. These geological, geochemical and isotopic data confirm that Arqiale is a typical distal skarn Pb Zn Cu deposit. Considering the chalcopyrite-garnet-ilvaite contents increasing and Zn/Pb rations decreasing from the shallow part in the south to the deeper part in the north, it is inferred that the hidden causative intrusions and Cu mineralization within contact zone may occur at depth in the northern part of Arqiale. [ABSTRACT FROM AUTHOR]

[Display omitted] • The initial ore-forming fluids were magmatic water, mixing with meteoric water. • The metals were derived from the hosing volcanic rocks and hidden causative pluton. • Fluid phase separation caused the formation of liquid bismuth and invisible gold. • The liquid bismuth collector model is responsible for the Au-Bi association. • Kuruer is a subepithermal Cu-Au mineralization related with the hidden porphyries. The Kuruer Cu-Au deposit is located in the Wusun Range of Yili Block, Chinese Western Tianshan, where numerous epithermal Au, skarn Fe-Cu and porphyry Mo-Cu deposits have been recognized. Petrography, fluid inclusions, S-Pb-H-O isotopes, field emission-scanning electron microscopy (FE-SEM) plus energy dispersive spectrometer (EDS) and electron microprobe analysis (EMPA) have been carried out to constrain the genesis of the Kuruer deposit and its implication for further exploration. The minerlization is hosted by volcanic rocks and occur as veins and veinlets structurally controlled by NW-trending faults. Three ore-forming stages were recognized, including quartz-sulfides-bismuth-gold stage (I), quartz-chalcopyrite stage (II) and calcite-chlorite-chalcopyrite stage (III). Six types of fluid inclusions were identified in stage I quartz, including monophase vapor inclusions (type 1), liquid-rich biphase inclusions (type 2), vapor-rich biphase inclusions (type 3), H 2 O-rich CO 2 -H 2 O triphase inclusions (type 4), CO 2 -rich CO 2 -H 2 O triphase inclusions (type 5) and solid halite-bearing triphase inclusions (type 6), whereas only type 2 inclusions were recognized in stage II quartz and stage III calcite. Types 2, 3, 4 and 6 inclusions in stage I have homogenization temperature (T h) ranges of 184–359 °C, 209–252 °C, 250–319 °C and 229–263 °C, with salinity ranges of 4.1–8.5 wt% NaCleq, 5.9–6.9 wt% NaCleq, 1.0–6.0 wt% NaCleq and 32.7–33.9 wt% NaCleq, respectively. Type 2 inclusions in stages II and III have T h varying from 144 to 212 °C and 114 to 163 °C, with salinities of 0.2–6.7 wt% NaCleq and 0.1–3.1 wt% NaCleq, respectively. The in-situ δ34S values of sulfides in stage I range from −4.66 to 0.34‰. The 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of stage I chalcopyrite vary from 18.295 to 18.954, 15.568 to 15.673 and 38.109 to 38.817, respectively, which are consistent with those of Early Carboniferous Dahalajunshan Formation volcanic rocks and granitoids from the Wusun Range. The values of δ18O H2O-VSMOW calculated from δ18O quartz and δD H2O-VSMOW of stage I quartz range from 0.0 to 2.4‰ and −118.6 to −109.3‰, respectively. These isotopic compositions indicate that both metals and sulfur were sourced from the hosting volcanic rocks and hidden causative pluton, while the initial ore-forming fluids were magmatic in origin, with increasing involvement of meteoric water with time. Evidence from mineralogy, mineral geochemistry and fluid inclusions indicates that the initial fluid phase separation triggered the precipitation of "invisible" gold within pyrite and chalcopyrite during stage I. Subsequently, the decrease of f S2 due to the escape of H 2 S (g) and sulfide precipitation and cooling caused the formation of liquid bismuth from solutions. The bismuth melts have scavenged Au in situ from the residual solutions, resulting in the formation of Bi-Au inclusions within the fractures and intergranular spaces of earlier pyrite. For stages II and III, dilution and cooling due to input of meteoric water facilitated the chalcopyrite precipitation. The Kuruer Cu-Au deposit is classified as a subepithermal mineralization associated with porphyries. Porphyry Cu-Au mineralization could have developed beneath the Kuruer and its vicinity. [ABSTRACT FROM AUTHOR]