Re–Os dating of two Cu–Ni sulfide deposits in northern Xinjiang, NW China and its geological significance

Abstract

Mafic–ultramafic intrusions in northern Xinjiang are located along major fault zones. Some of these intrusions host Cu–Ni sulfide deposits and amongst these are two economically important Cu–Ni deposits – Kalatongke (also called Karatungk) and Huangshan East (Huangshandong). Sulfides from these deposits were selected for a Re–Os geochronological study in order to understand the tectonic and metallogenic environment of the mafic–ultramafic intrusions and the associated Cu–Ni sulfide deposits in northern Xinjiang. Re–Os dating of Cu–Ni sulfide ores in the Nos. 1 and 2 intrusions of the Kalatongke ore district and Huangshan East deposit gave isochron ages of 282.5 ± 4.8, 290.2 ± 6.9 and 284 ± 14 Ma, respectively, with initial 187Os/ 188Os ratios of 0.2563 ± 0.0073, 0.2721 ± 0.0053 and 0.241 ± 0.092. The γ Os values of the Kalatongke and Huangshan East deposits range from 100.6 to 124.2 and from −25.6 to 235.9. These results indicate that the Cu–Ni sulfide mineralization in both deposits formed during the Early Permian (280–290 Ma). Integrating our field observations with published literature and the Re–Os data presented in this work, we suggest that the mafic–ultramafic rocks investigated were emplaced in a post-collisional extensional setting and the Cu–Ni sulfide ores were segregated from crustally contaminated magmas.