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.