Pyrite Re-Os geochronology of the Sareke sediment-hosted Cu deposit, Xinjiang, NW China

Abstract

The Sareke Cu deposit in the western Tarim region (Xinjiang, NW China) is hosted in continental sedimentary rocks of the Upper Jurassic Kuzigongsu Formation and Lower Cretaceous Kezilesu Group. Stratabound orebodies occur mainly in conglomerate and minor in siltstone. Both stratabound (major) and vein type (minor) ores are composed of chalcocite, chalcopyrite, bornite and pyrite with minor sphalerite and galena, which show a zonation pattern of chalcocite → chalcopyrite → sphalerite + galena → pyrite from north to south of Sareke. Carbonation is the most important hydrothermal alteration at Sareke and dolomite together with calcite are the dominant gangue minerals.Six pyrite samples which coexist closely with copper sulfides are Re-Os dated and yielded a Re-Os isochron age of 115.8 ± 4.7 Ma and a weighted mean age of 114.3 ± 1.8 Ma, which constrain the Sareke Cu mineralization to the late Early Cretaceous. This age is synchronous with the tectonic inversion event and the basaltic magma activities of the Tuyon basin, which could been sources of dynamics and thermodynamics during the ore-forming process. This is the first unambiguous evidence for an appreciable copper concentration of Mesozoic age, and based on this evidence, additional Mesozoic sediment-hosted stratabound copper mineralization event may have occurred elsewhere within basins along the Talas-Fergana fault.