Ore-forming Mechanism And Ore-bearing Property Evaluation For Getashankou Ni-Cu Deposit In Eastern Tianshan, Xinjiang

The newly-discovered Getashankou Ni-Cu deposit is located in the eastern of theKanggur-Huangshan ductile shear fracture zone, eastern Tianshan, NW-China. There arefive intrusions, and the intrusionⅠ, Ⅱ, Ⅲ and Ⅴ are Ni-Cu sulfide bearing intrusions.By high-precision SIMS Zircon U-Pb dating, the age of ore-bearing gabbros fromintrusion is282~285Ma. The age is consistent with other sulfide bearing mafic-ultramaficintrusions in eastern Tianshan, Beishan area and the Tarim basalt and mafic dykeswarm.The δ18O of zircon is located near the mantle range.The main lithofacies of Getashankou intrusions are olivine-websterite, buchnerite,gabbro and diorite. The geochemical data shows that the m/f values of28samples rangefrom2.16to5.05(falling into the range of ferruginous ultramafic rocks), LREE-richpattern with the ratio of LREE/HREE ranges from2.64to5.13, enriched LILE(Ba、Sr)and HFSE(U、Pb), depleted HFSE(Th、Nb). The correlation of SiO2-(Na2O+K2O),(TFeO/MgO)-TFeO, trace elements and its ratio and the compositions of amphibole andclinopyroxene indicates that the magma of Getashankou is derivative magma originatedfrom the calc-alkaline basaltic which came into being through15.1%~18.8%partialmelting for the mantle source region, and the excess olivine in addition. The diagenesis ismainly controlled by the magmatic crystallization, and contaminated by the crust duringupward of magma. The formation of Getashankou intrusions may be related to thePermian mantle-plume activity add to the post-orogenic processes.The the forsterite (Fo) values of fresh olivine vary from81.4to87.6, and thecomponent of nickel ranges from1069to2829ppm. The crystallization temperature ofolivine and spinel ranges from978℃to1466℃. The model calculation of the variationof nickel content and Fo of olivine crystals shows that before the olivine crystal, themagma has reached sulfur saturation. Therefore, the Getashankou intrusions hava goodpotential for Ni-Cu sulfide exploration.