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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 Tawuerbieke deposit is one of the important mining gold deposits in the Tulasu basin, which is known as an epithermal gold ore cluster in the Boluokenu Polymetallic Belt (BPB), western Tianshan, China. The orebodies of this deposit are hosted by late Palaeozoic volcanic rocks and granitic porphyries. LA-ICP-MS U–Pb dating on zircons from a hosting andesite gave a weighted average age of 367.1 ± 3.2 Ma. Geochemical characteristics of the Late Devonian volcanic rocks are similar to those of arc-type magma, which could be formed in a continental arc due to the North Tianshan oceanic plate southward subduction under the Yili-Central Tianshan plate. Diorite aplite dike crosscutting orebody has a late Carboniferous crystallization age (315.2 ± 3.5 Ma), constraining the mineralization age within the range of 367 ~ 315 Ma. Considering that all the other deposits with various types of mineralization in the BPB are products of the Late Devonian–early Carboniferous magmatism, we further suggest that the Tawuerbieke deposit formed during Late Devonian to early Carboniferous. Isotopic geochemistry data of S, Pb, C, and O suggest that the ore-forming materials were mainly derived from the host volcanic-subvolcanic rocks. The ore-hosting rock types, hydrothermal alteration, and ore mineral assemblage and textures of the Tawuerbieke distinctly differ from those of the low- and high-sulphidation epithermal Au deposits in the Tulasu basin, indicating that it could experience the telescoping/juxtaposing between porphyry- and epithermal-style mineralization. The epithermal- and porphyry-type Au mineralization in the Tawuerbieke deposit, together with the low- and high-sulphidation epithermal Au, porphyry Cu, and skarn-type Fe–Cu mineralization in the Tulasu basin, constitutes an epithermal–porphyry–skarn polymetallic mineralization system. The development of such mineralization system and magmatic-arc setting in the Tulasu basin suggests that porphyry-type Cu–Au mineralization should have a high potential at the deep sites of the Tawuerbieke district. [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]

The 'green-bean rock' (GBR) is a greenish or yellowish green Triassic potassium-rich felsic tuff containing prominent bean-like quartz grains, which is widespread in the Yangtze platform and Nanpanjiang basin, South China. This paper studies the age, origin and tectonic setting of the GBR from the western margin of the Yangtze platform through whole-rock geochemistry and zircon U--Pb geochronology and Hf isotopes. In contrast to the Nanpanjiang basin, where multiple GBR layers are developed and encompass the Olenekian-Anisian boundary (OAB), which is constrained to be at 247.1–247.3 Ma, the age of the single GBR layer in the western margin of the Yangtze platform and its relationship with the OAB have not been determined. U--Pb dating on zircons from the GBR in this study yielded an age of 247.49 ± 0.68 Ma, which is considered to be comparable to that of the OAB, and thus the GBR may be used as a marker for regional stratigraphic correlation. The volcanic ashes of the GBR have been previously suggested to be derived from the Siberian Traps Large Igneous Province or from the Shiwandashan-Qingfang suture zone to the south of the Nanpanjiang basin. However, the whole-rock geochemistry of the GBR, especially enrichment in LREE, Th and U and depletion in Nb, Ta, Sr, Ba, K, Rb and Ti, and strong to moderate negative Eu anomalies (δ Eu = 0.16–0.20), suggest that the volcanic ashes are more likely derived from the adjacent Sanjiang Orogen to the southwest. The zircon geochemistry, especially the negative ε Hf (t) values (−16.4 to −5.1) and old two-stage Hf model (T DM2) ages (1.60–2.30 Ga), are also similar to those from the Early-Middle Triassic felsic volcanic rocks in the Sanjiang Orogen. The subduction of the Paleo-Tethys Ocean was previously inferred to have started between Early Permian and Middle Triassic. The data obtained in this study, in combination with those compiled for igneous rocks and volcanic ashes from Middle Permian to Late Triassic from the region, suggest that the subduction initiation of the Paleo-Tethys Ocean began no later than ~254 Ma, in middle Late Permian. • The new zircon U--Pb age of 247.49 ± 0.68 Ma was obtained for the GBR. • The GBR can be used as a marker for the Olenekian-Anisian boundary (OAB). • The GBR are derived from the Sanjiang Orogen. • The subduction of the Paleo-Tethys Ocean started at 254.8 Ma. [ABSTRACT FROM AUTHOR]