New data on the geology and geochronology of the Sarsuk deposit, a Au–bearing VMS deposit in the Ashele Basin, Altay Orogenic Belt, Xinjiang, Northwest China

Abstract

The Sarsuk polymetallic gold deposit, located in the Ashele Basin of the Chinese Altay Orogenic Belt in the Central Asian Orogenic Belt (CAOB), Xinjiang, China, is a gold–bearing volcanogenic massive sulfide (VMS) deposit. This deposit primarily consists of veins within the rhyolitic porphyry and tuff of the Ashele Formation, with a minor occurrence of stratiform mineralization within the tuff. Chronometric studies of ores at various depths and volcanic rocks in the deposit, suggest that the vein mineralization hosted in the upper rhyolitic porphyry is dated at 383–386 Ma, whereas vein mineralization within the tuff is dated at 387–388 Ma. The veins in the rhyolitic porphyry formed slightly later than the veins that mineralized in the tuff. Additionally, LA–ICP–MS dating of zircons indicates that the basalts of the Ashele Formation formed at 405.7 ± 4.8 Ma, with andesites forming at 403.4 ± 8 Ma, and SHRIMP U–Pb dating reveals that basaltic andesites were formed at 397.5 ± 4.1 Ma. Integrating these findings with those of previous studies indicates that the Sarsuk deposit is a complex VMS deposit that is closely related to regional volcanic activity. The ore-forming processes are divided into an exhalative-sedimentary period, corresponding to mineralization within the volcanic rocks of the Ashele Formation, and a subvolcanic hydrothermal period, associated with the rhyolitic porphyry. The two periods of mineralization are products of the same VMS mineralization system. The Sarsuk polymetallic gold deposit is a product of the main mineralization period of the Altay VMS deposits.