首页|Petrogenesis and Economic Potential of the Sangong Mafic-Ultramafic Intrusion in the Eastern Tianshan, Central Asian Orogenic Belt: Constraints from Mineral, Whole-Rock, and PGE Geochemistry
Petrogenesis and Economic Potential of the Sangong Mafic-Ultramafic Intrusion in the Eastern Tianshan, Central Asian Orogenic Belt: Constraints from Mineral, Whole-Rock, and PGE Geochemistry
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The Sangong Cu-Ni sulfide mineralized mafic-ultramafic intrusion is located on the south-ern margin of the Bogeda-Harlik belt, eastern Tianshan, China. The intrusion is a well-differentiated complex and is comprised of leucogabbro, gabbro, olivine gabbro, Pl-bearing peridotite, and Pl-bearing pyroxenite. The Pl-bearing pyroxenite hosts both irregularly disseminated sulfide and round droplet sul-fide. The intrusive rocks have a wide range of SiO2 (42.1 wt.％-50.48 wt.％) and MgO (6.21 wt.％-22.11 wt.％), and are enriched in light rare earth elements (LREE), large-ion lithophile elements (LILE; e.g.,Rb, Ba, Sr, and Pb), and palladium platinum group elements (PPGE) but depleted in high-field-strength elements (HFSE; e.g., Nb, Ta, and Ti) and iridium PGEs (IPGE). These geochemical characteristics indi-cate that the Sangong mafic-ultramafic intrusion was derived from high degree of partial melting of de-pleted mantle and interacted with subduction-related material. The low Pd/Ir (3.21-27.44) but high Ni/Cu (1.64-24.16) ratios, combined with the olivine crystals with low Fo (60.88-78.65) and Ni (54.99 ppm-1688.87 ppm) concentrations suggest that the parental magma of the Sangong intrusion were likely high MgO basaltic in composition that experienced extensive evolution prior emplacement. The Ce/Pb ratios (5.8-13.6) and Nb/U ratios (11.6-30.3) of the intrusive rocks all range between MORB and crustal values, the Nb/Yb and Th/Yb values are close to the lower crust values, together with the low Se/S ratios [(17-100) × 10-6)] suggest that the magma experienced assimilation not only in mantle source but also in conduit, but the degree of crustal contamination is limited. The Cu/Pd ratios of the rocks range from 3.9 × 104 to 10.8 × 104, and the Cu/Zr ratios of Pl-bearing pyroxenite in the Sangong intrusion are >1, com-bined with the presence of sulfide droplets in the Pl-bearing pyroxenite, indicating the parental magma experienced sulfide saturation and the economical ore bodies may present in the depth of the intrusion. Furthermore, given the discovery of the Baixintan and Yueyawan deposits, we propose the Dananhu-Harlik belt as an essential prospecting target for Cu-Ni mineralization in North Xinjiang.
College of Resources and Environmental Engineering, Guizhou University, Guiyang 550012, China
Technic Research Center for Deep Resources Exploration in Non-ferrous Metal Mines, Beijing Institute of Geology for Mineral Resources Co., Ltd., Beijing 100012, China
Sino-Zijin Resources Ltd., Beijing 100012, China
State Key Laboratory of Nuclear and Environment, East China University of Technology, Nanchang 330013, China
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