Geology and geochronology of the volcanogenic massive sulphide polymetallic deposits in Altay Orogenic Belt, Xinjiang, Northwest China: examples from the Kelan Basin

The Chinese Altay orogenic belt (comprising the Ashele, Kelan, and Maizi volcano-sedimentary basins) contains more than 20 volcanogenic massive sulphide (VMS) deposits and mineralizations. VMS deposits in the Kelan Basin are hosted in volcano-sedimentary rocks of the Lower Devonian Kangbutiebao Formation. The orebodies are lenticular bedded in shape and are conformable with the surrounding country rock. The ore structures include massive, banded, ribbon, dense disseminated, veinlet, stockwork, and veinlet-disseminated structures. Four mineralizing events have been identified in the Dadonggou Pb–Zn, Tiemierte, and Wulasigou polymetallic deposits. We performed Rb–Sr isotopic dating on sphalerites and pyrites of the exhalative-sedimentary period from the Dadonggou, Tiemierte, and Wulasigou deposits. Seafloor exhalative processes are identified as being most significant for the formation of economic mineralization during the 394–391 Ma interval. The syndepositional VMS deposits in the Chinese Altay formed during the Early–Middle Devonian (386–413 Ma): the mineralization ages of the Maizi, Kelan, and Ashele basins are 386–400 Ma, 391–413 Ma, and 387–394 Ma, respectively. The younger subvolcanic hydrothermal mineralization in the Ashele Basin occurred from 379–383 Ma.