| Full Reference | Liu, Ying; Sun, Xiaoming; Fu, Yu; Xu, Li; Yang, Chengye; Liu, Qiaofen; Ran, Menglan; Ding, Zhengpeng; Ling, Shimeng; Yi, Jianzhou (2025) Genesis of the Chalapu orogenic gold deposit in southern Tibet: New insights from in situ geochemistry and sulfur isotopes of auriferous sulfides. Ore Geology Reviews, 186. 106891 doi:10.1016/j.oregeorev.2025.106891 |
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| Plain Text | Liu, Ying; Sun, Xiaoming; Fu, Yu; Xu, Li; Yang, Chengye; Liu, Qiaofen; Ran, Menglan; Ding, Zhengpeng; Ling, Shimeng; Yi, Jianzhou (2025) Genesis of the Chalapu orogenic gold deposit in southern Tibet: New insights from in situ geochemistry and sulfur isotopes of auriferous sulfides. Ore Geology Reviews, 186. 106891 doi:10.1016/j.oregeorev.2025.106891 |
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| Abstract/Notes | The Tethys Himalaya metallogenic belt hosts numerous significant gold deposits, among which the Chalapu gold mineralization represents one of the most substantial. However, the metallogenic mechanism, particularly the origins of mineralizing fluids, remains contentious due to limited research. Sulfide minerals are essential in determining the mechanisms of ore formation and tracing the origin of the mineralizing fluids. In this study, we investigate textures, trace element, and sulfur isotopic component of pyrite as well as the trace elements of arsenopyrite to elucidate the ore genesis. Five distinct types of pyrite and three types of arsenopyrite are identified: (1) framboidal pyrite (Py0), occurring in carbonaceous slate, represents pre-ore sedimentary pyrite; (2) euhedral, fine-grained pyrite (Py1) that forms aggregates and coexists with euhedral arsenopyrite (Apy1) in altered-rock ores; (3) euhedral, coarse-grained pyrite (Py2) and arsenopyrite (Apy2a) found in brecciated quartz veins. Py2 is further categorized into Py2a, Py2b, and Py2c. Py2a underwent coupled dissolution-reprecipitation to form Py2b. Coarse-grained pyrite (Py2c) exhibits fractures filled with native gold, galena, sphalerite, and chalcopyrite. Irregular arsenopyrite (Apy2b) occurs together with native gold in sulfide-bearing quartz veins. In situ sulfur isotope analyses reveal δ34S values of 0.70–2.95 ‰ for Py1, 3.11–3.34 ‰ for Py2a, 3.46–4.23 ‰ for Py2b, and 3.32–4.32 ‰ for Py2c. These data suggest a consistent sulfur source predominantly derived from metamorphic processes. Py1 formed under reduced conditions characterized by low oxygen fugacity and a stable physicochemical environment. The Co/Ni ratios for Py1 range from 1.12 to 5.35, indicative of a hydrothermal origin. The early hydrothermal fluid was enriched in As but depleted in Au, extracting trace elements such as Ag, Pb, Bi, Sb, Co, and Ni from the host rock through fluid-rock interactions, resulting in the formation of disseminated pyrite and arsenopyrite. Gold is preferentially enriched in Apy1, while Py1 exhibits relatively low concentrations of Au. Py2 represents the primary mineralization stage of hydrothermal pyrite, with Co/Ni ratios ranging from 0.02 to 0.59. This stage is characterized by As-, Au-, Cu-, Pb-, and Zn-rich hydrothermal fluids precipitated native gold, galena, sphalerite, chalcopyrite, and other sulfides within structurally controlled fracture zones and fold hinge regions, through processes involving fluid immiscibility and fluid-rock interaction. Previous studies have dated the Chalapu gold deposit to approximately 18.7 Ma, closely aligning with regional metamorphic events associated with the Yardoi gneiss dome and leucogranitic magmatism. Consequently, we propose that magmatic heat uplift during post-collisional orogenic extension served as the primary thermal driver for the large-scale circulation of ore-forming fluids. The Chalapu gold deposit is thus interpreted as an orogenic gold deposit formed within a post-collisional extensional tectonic setting. |
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