Genesis of the Dadonggou Pb–Zn deposit in Kelan basin, Altay, NW China: Constraints from zircon U–Pb and biotite 40Ar/39Ar geochronological data

Abstract

The genesis of polymetallic deposits in southern Altay, NW China has been disputed between a syngenetic seafloor hydrothermal process and an epigenetic orogenic-type mineralization. The Dadonggou Pb–Zn deposit occurs as NW-trending veins in the Devonian Kangbutiebao Formation volcanic-sedimentary sequence in the Kelan basin, southern Altay. A set of integrated zircon U–Pb and biotite 40Ar/39Ar geochronological data were applied to constrain the forming ages of the ores and their country rocks. Three samples of host volcanic rocks yielded weighted mean 206Pb/238U ages of 397.1±4.5Ma, 391.7±3.6Ma and 391.1±4.2Ma, respectively, indicating that the Kangbutiebao Formation was deposited in a Devonian back-arc basin. Two biotite samples separated from the Pb–Zn-containing quartz veins yielded 40Ar/39Ar plateau ages of 205.9±2.1Ma and 204.3±2.2Ma, respectively, which represent the age of the Pb–Zn mineralization that is attributed to the closure of the Kelan back-arc basin and the Late Triassic orogeny. Combining the available geological and geochronological data, this contribution outlines the successive evolution from the development of a Devonian back-arc basin to the Late Triassic post-subduction orogeny, and proposes that the Dadonggou Pb–Zn deposit is an epigenetic orogenic-type deposit placed in the Late Triassic orogeny.