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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]

[Display omitted] • The initial ore-forming fluids were magmatic water, with input of meteoric water with time. • Fluid phase separation and mixing triggered the Pb-Zn-Ag and Sb precipitation, respectively. • Keyue is the distal Pb-Zn-Sb-Ag mineralization centered on the Cuonadong leucogranites. • Pegmatite-skarn-type W-Sn-Be deposits may occur at deeper sites beneath the Keyue area. The Keyue Pb-Zn-Sb-Ag polymetallic deposit is located within the North Himalayan Metallogenic Belt (NHMB). This study aims to clarify whether the Keyue deposit has close association in time and space with magmatism, and discuss the significance for further exploration. Orebodies are hosted by the Lower Jurassic Ridang Formation black carbonaceous slate and controlled by the NE-trending faults. Keyue is characterized by multiple stages of hydrothermal veins, including Mn-Fe Carbonate-sulfide (I), quartz-sulfide-sulfosalt mineral (II) and quartz-calcite-stibnite veins (III). Hydrothermal minerals contain six types of fluid inclusions, including H 2 O-rich bi-phase aqueous (type I), pure CO 2 (type II), CO 2 -rich H 2 O-CO 2 -NaCl tri-phase (type III), H 2 O-rich H 2 O-CO 2 -NaCl tri-phase (type IV), halite-bearing tri-phase (type V) and halite-bearing H 2 O-CO 2 -NaCl multiphase inclusions (type VI). All six types of inclusions were observed in stage II quartz, whereas only types I and III inclusions in stage I siderite and sphalerite and type I inclusions in stage III quartz and calcite. Type I inclusions in stage I display total homogenization temperatures (T h, total) ranging from 250.1 to 289.3 °C, with salinities of 9.6–16.3 wt% NaCleq. Types I, III, IV and V inclusions in stage II yield T h, total of 175.5–282.7 °C, 188.8–286.3 °C, 214.3–287.5 °C and 198.3–266.0 °C, with corresponding salinities of 4.0–21.5 wt% NaCleq, 0.6–2.9 wt% NaCleq, 0.0–11.0 wt% NaCleq and 30.1–33.2 wt% NaCleq, respectively. Type I inclusions in stage III have T h,total values of 172.3–240.7 °C and salinities of 3.1–12.6 wt% NaCleq. Fluid phase separation occurred in stages I and II, resulting in CO 2 and H 2 S release, pH increase and rapid Pb-Zn-Ag precipitation, whereas mixing of magmatic fluids and meteoric water in stage III caused the cooling, dilution and stibnite precipitation. Fluid inclusion analysis and C-H-O isotopic compositions indicate that the initial hydrothermal fluids were magmatic water, with increasing input of meteoric water with time. The δ34S CDT values of sulfides from three stages are similar and range from 4.8 to 10.3 ‰ (average 7.7 ‰), showing characteristics of mixture of magmatic and sedimentary sulfur. The Pb isotopic compositions of sulfides are closely consistent with those of Cenozoic leucogranite and Precambrian metamorphic crystalline basement in the NHMB, suggesting that the ore-forming metals were sourced from the hidden causative Himalayan leucogranite formed by the decompression melting of metamorphic crystalline domains. Combining evidence from geochronology, fluid inclusions, isotopes suggest that the Keyue Pb-Zn-Sb-Ag and Cuonadong W-Sn-Be mineralization at different locations around the Cuonadong Dome constitute an integrated magmatic-hydrothermal system, with the distal end-member Pb-Zn-Sb-Ag veins centered on the Cuonadong leucogranites-related W-Sn-Be mineralization. Pegmatite-skarn-type W-Sn-Be polymetallic mineralization may occur at deeper sites beneath the Keyue area, and the distal Pb-Zn-Sb-Ag veins controlled by faults within strata also need more attention around these leucogranite domes in the NHMB. [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]