Ni-Cu Metallogenic Characteristics of Small Intrusions in Hualong, Southern Qilian Mountains

Hualong,is located in the South Lajishan,has developed many small basic-ultrabasic intrusions,simultaneously,is a great important Ni-Cu metallogenic belt in South Qilian mountains,and formed Yulonggou,Lashuixia,Yaqu small scale magmatic Ni-Cu sulfide deposits that relationed closely with these small intrusions.It found that the small intrusions belong to iron series basic-ultrabasic complex in Hualong by the study on geological and geochemical characteristics,expressed as the intrusions with Cu-Ni sulpides develop an iron-enrichment trend,rare earth elements exhibit a LREE enrichment characteristics,and shows egative Eu anomalies The enrichment in large ion lithophile elements (LILE),depleteion in high field strength elements (HFSE) and the appearance of a negative Nb-Ta anomally indicate a chemical affinity to cal-alkaline rocks.Ore isotope study revealed that the Ni-Cu deposits had formed from crystallization and differentiation of the original magma,suffered from crustal contamination,and the participation of Si-rich material.Together with regional tectonic evolution and mineralization recognization,it suggests that the formation of rock and ore in Hualong were related closely to geological environment on subduction.