Whether orogenic gold deposits formed from crustal or subcrustal sources is debated, and their link to orogenic processes is ambiguous. Gold mineralization in the Triassic East Kunlun−West Qinling Orogen, China, displays a spatial zonation in terms of its ages and stable isotope compositions. In the West Qinling segment, most gold deposits formed in a back-arc setting at 220∼210 Ma during a collisional episode within late slab rollback. These deposits have dominant δ34S of 5∼15‰ and δ18Ofluid of 10∼14‰, whereas those formed in the suture zone at 210∼170 Ma, during a post-collisional episode after slab break-off, have lower δ34S of −5∼+5‰ and δ18Ofluid of 6∼10‰. In the East Kunlun segment, those deposits that formed in a continental-arc setting and its related suture zone at 240∼200 Ma, in collisional to post-collisional episodes associated with slab break-off, have δ34S and δ18Ofluid values that are essentially similar to those in the West Qinling suture. δ34S values of ore sulfide separates and rims of zoned pyrites that have mantle-like signatures, in contrast with crustal signatures of host rocks, are indicative of subcrustal ore-fluid sources. The combined chronological and stable isotope shifts are consistent with a model in which ore fluids for gold mineralization in a back-arc setting were sourced from mantle lithosphere that was metasomatized by subducted oceanic sediment; whereas those in a continental-arc setting—including its suture zone—were sourced from fluid derived from altered oceanic crust. This study thus provides new insights into the complexity of orogenic gold systems in evolving orogens.

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