Petrographic and geochemical characteristics of the Tulargen Cu-Ni-Co sulfide Deposit, East Tianshan, Xinjiang, and its tectonic setting

Abstract：The Tulargen Cu-Ni-Co deposit, lying in the northeastern segment of the Kangurtag-Huangshan ductile sheer zone, is a semi-hidden deposit formed mainly by deep-level liquation of sulfide, combined with in-situ liquation and hydrothermal superimposition. Intrusion No.1 is characterized by whole-rock mineralization and can be divided into four rock facies：hornblende peridotite, pyroxene peridotite, hornblende pyroxenite and gabbro. The rocks show the features of repeated pulsatory magmatic upwelling and ore formation in a single phase. The m/f ratio of the intrusion varies from 3.1 to 4.8, falling into the range of ferrous-ultramafic rocks. The intrusion is featured by low Ti, low total alkalis and low Al2O3, similar to the petrochemical characteristics of the Huangshan-Jing＇erquan mafic-ultramafic complex. The REE distribution patterns and trace element and transition element spidergrams indicate that the No.1 and No.2 mafic-ultramafic intrusions in the Tulargen ore district are comagmatic and supplementary, implying that the deep part of the No.2 intrusion has a great ore potential though gabbro of the No.2 intrusion shows weak mineralization at the surface. According to the MT section across both the No.1 and No.2 intrusions, it is clear that they share only one magma conduit at depth and originated from the same magma source. Lower La/Sm (<2) and Th/Ta (4.6) ratios suggest a mantle origin of the ore magma and little contamination with crustal material during the emplacement of the intrusion.