SIMS U–Pb zircon dating and Re–Os isotopic analysis of the Hulu Cu–Ni deposit, eastern Tianshan, Central Asian Orogenic Belt, and its geological significance

Abstract

Exploration of the Hulu Cu–Ni–Co sulfide deposit in Eastern Tianshan, Central Asian Orogenic Belt, has detected horizons of sulfide mineralization in pyroxenite and peridotite units. SIMS U–Pb zircon ages of the gabbro-hosting Cu–Ni–Co sulfide deposit indicate that the Hulu intrusion was emplaced at 282.3 ± 1.2 Ma (95% confidence level, MSWD = 3.30, n = 13). Osmium isotopic data suggest that the Hulu intrusion and associated Cu–Ni mineralization were derived from crustally-contaminated mantle melts. The intrusions clearly show island-arc geochemical signatures, such as negative Nb, Ta, Zr and Ti anomalies and enrichment in LILE. These geochemical tracers indicate that the Hulu mafic–ultramafic intrusions, along with the Cu–Ni deposit, formed as a result of subduction of oceanic crust in the Early Permian. The arc-related geodynamic setting of the Hulu Cu–Ni deposit is unusual for magmatic sulfide deposits. This new type of ore deposit offers an alternative perspective for Cu and Ni exploration.