Research On Petrology And Mineralogy Of Tulargen Ni-Cu Deposits, Eastern Xinjiang

The Central Asian Orogenic Belt(CAOB) is the largest Phanerozoic continental crust hyperplasia belt and is also one of the important magmatic Cu-Ni metallogenic belts, which has attracted many attentions of geologists. Many mineralized mafic-ultramafic intrusions are distributed in the southern margin of the CAOB, including East Tianshan area(Huangshan, Huangshandong, Hulu, Tulargenand Xiangshan deposit) and the Beishan region(Heishan, Bijiashan and Hongshikou deposit). The Tulaergen deposit is located at northeastern margin of the Jueluotage belt.The Jueluotage belt has undergone intense ductile shearing deformation with numerous mafic-ultramafic mineralized intrusions. There are three small ma?c–ultrama?c intrusions in the Tulaergen Ni-Cu sulfide deposit: namely, the I, II and III complexes. The I complex are wholly mineralized and sulfide content in most of the orebodies tends to increase upward, inconsistent with the principal characteristic that orebodies are usually at the base of the intrusion. Both of II and III complexes are without obvious mineralization. We selected the I complexe for a detailed study, focusing on petrology, mineral deposit and geochemistry. Some conclusions are as following :① TulargenⅠrock is a typical small-scale mafic-ultramafic ore-bearing intrusion, which is composed of different mafic-ultramafic lithofacies. hornblende lherzolite, hornblende olivine websterite, hornblende websterite, websterite and hornblende gabbro with adjacent lithofacies having a gradational transition relationship. The densely disseminated and massive sulfide ores are mainly occurred in hornblende lherzolite. Pyroxene, olivine, amphibole, feldspar, biotite are the main petrogenic minerals.② The Mineralogical characteristics indicate that Fo values are between 81.08 and 84.53, Fo values were rising from the edge to the core part..The trapped silicate and sulfur liquid had changed the origin composition of olivine significantly.③The modeling indicate that Tulaergen parental magma result from depleted mantle basaltic magmas by 14% partial melting of mantle souce.. The parental magma undergone 3% olivine fractional crystallization and then “S” began to reach saturation with sulfides segragation.④The Ni contents of some olivines are abnormally high, partly because after the plate subduction, providing H2 O so as to improve the oxygen fugacity of the parent magma. The evidence for this prediction is that amphibole mineral are found in Tulaergen deposit. The other reason is everfount upwelling magma provides a large number of Ni to offset the Ni decreasing result from the sulfide segregation, olivine crystallization differentiation.