Study On The Enrichment Regularities Of Mineralization And Geological Characteristics Of Niubiziiiang Nickel Ore Deposit, Mangya, Qinghai Province

Qaidam Basin and surrounding areas are the largest mineral region in QinghaiProvince, where discovery of Niubiziliang copper-nickel ore deposit was the first typedeposit relating to mafic-ultramafic rocks. The discovery of Niubiziliang and itsgeological significant is able to expand idea of prospecting or exploration of space inQaidam Basin and surrounding areas.The ore deposits located in ancient craton margin of Qaidam Basin, its mafic-ultramafic magmatic activity is closely related to the geodynamic evolution of thenorthern Qaidam Qilian orogenic belt. The study area has simple stratum,mainly includinglower Proterozoic Jinshuikouyan group gneiss and Quaternary strata.Ore region has manyfaults with EW or NEE towards, which all are later than metallogenic epoch，some faultshave a damaging effect on ore body. There are many magmatic activities, such asDevonian mafic-ultramafic rocks, Devonian diorite, Carboniferous monzonitic granite.The NO. Ⅱo re body of Niubiziliang located in southwestern ore deposit, with goodore and wedge morphology, meanwhile the ore dip in southwest, there is an opposite diptendency in some area, NO.Ⅲ ore body located in southern ore deposits, with NWWtendency, east narrow west wide and wedge morphology. The ore dip in south, there isalso an opposite dip tendency in some area. These two ore body have similar lithofaciesfeature(Ore-bearing rock facies are mainly pyroxenite and peridotite phase) and mineralization type. Rock mineral grains are finer, with poor shaped degree andmineralization weak and scattered，they should belong to whole rock， then devided intodifferent two ore body by F4fault.There is an obvious lithofacies zonation, like peridotite, pyroxenite, gabbro anddiorite phase, mafic-ultramafic rocks have transition trend, diorite invade intomafic-ultramafic rocks. Ore mainly exists in peridotite, pyroxenite phase.Ore bodydevelop alteration, such as serpentinization, silicification, chloritization, steatite,epidotization, carbonatization, reflecting the late hydrothermal alteration.LA-ICP-MS zircon U-Pb dating indicates that gabbro(389±2Ma)，pyroxenolite（380±2Ma）,augite peridotite（373±2Ma）,which shows that Niubiziliang mafic andultramafic intrusion belongs to complex massif because of multiphase magamatic activity,meanwhile adding later neutral and acidic magamas activity.Study on rock geochemistry and isotope,main elements shows that transiting fromcalcium alkali to high potassium calcium alkali,geochemical background is extension ofcollision,trace element shows LREE enrichment and HREE loss,Eu anomaly is notobvious, Ore-forming materials mainly come from mantle source, with late crustalmaterial adding.According to the research of regional geological background, minerogeneticcondition，geological features of mafic-ultramafic rock and deposit, author can come to theconclusion that Niubiziliang nickel deposit is formed in the lately Devonian, Many timesthe liquation-injection eventually lead to the formation of ore deposits and belongs to thedeep segregation-pulse penetration model with late hydrothermal process superimposed.