Geology, fluid inclusion and age constraints on the genesis of the Sarekuobu gold deposit in Altay, NW China

Abstract

The Sarekuobu gold deposit was discovered in the 1990s and is located in the Kelan Basin on the southern margin of the Chinese Altay Orogen. Orebodies are hosted in the Early Devonian metamorphosed volcanic‐sedimentary sequence and controlled by the NW‐trending Abagong Fault. Mineralization can be divided into early, middle and late stages, characterized by quartz–pyrite, polymetallic quartz–sulphides and carbonate–quartz, respectively. Four types of fluid inclusions were identified in quartz veins, i.e. pure CO2 (PC‐type), CO2–H2O (C‐type), aqueous (W‐type) and daughter mineral‐bearing inclusions (S‐type). Hydrothermal fluids related to the mineralization are composed of CO2–H2O–NaCl ± CH4 ± N2 fluids with Th values of 236–374 °C and salinities of 4.8–15.0 wt.% NaCl eqv. (in general 8.0–15.0 wt.% NaCl eqv.), combined with trapping pressures of 90–330 MPa, suggesting that the mineralization resulted from a metamorphic fluid system. One biotite sample from the polymetallic quartz lodes yields a 40Ar/39Ar isotopic plateau age of 213.5 ± 2.3 Ma, marking the time of mineralization as Triassic. This mineralization age is broadly comparable with the mineralization age reported from the Tiemurt Pb–Zn deposit and Wulasigou Cu deposit located near the Sarekuobu gold deposit, indicating that the deposit was possibly related to the Permian–Triassic continental collision at the southern margin of the Altay Orogen. Our results show that the Sarekuobu gold deposit is not syngenetic, but an epigenetic orogenic gold deposit. Copyright © 2014 John Wiley & Sons, Ltd.