Zircon U-Pb chronology, platinum group element geochemistry characteristics of Hulu Cu-Ni deposit, East Xinjiang, and its geological significance.
新疆葫芦铜镍矿床锆石U-Pb年代学、铂族元素地球化学特征及其地质意义

Hulu intrusion lies in the eastern part of Tudun-Huangshan-Jingerquan-Tulargen mafic-ultramafic rocks belts in East Tianshan, and cover an area of about 0.75km2, is a multiple intrusion and composed of gabbro diorite, gabbro, pyroxenite, pyroxene peridotite and peridotite. The zircon LA-ICP-MS U-Pb dating for gabbro diorite of Hulu intrusion yielded 274.5±3.9Ma. The data suggest that the Hulu intrusion was intruded at Early Permian, is the result of a post-collisional extensional setting. The total concentration of platinum-group element (PGE) in ores and rocks is low. The average concentration of PGE in rocks is 7.90×10-9, and 45.57×10-9 in ores. Rock and ore samples have similar mantle-normalized PGE patterns, the diversity between IPGE and PPGE is lower. The diagram of Ni/Cu verses Pd/Ir reveals that the initial magma of Hulu mafic-ultramafic complex is high magnesian basaltic magma. The Ni/Cu ratio of ores and rocks is from 114.67×103~157.42×103(136.05×103 in average) and 11.07×103~294.35×103 (125.48×103 in average) respectively, which show that the magma has occurred sulfide pre-segregation from the magmatic system resulting in parental magma depleted in PGE. Crustal contamination (addition of SiO2 and S) and the fractionation of olivine and pyroxene in the magma revolution process may be the main factors leading to S-saturation and sulfide segregation in deep crust.