北祁连走廊南山西水地区加里东期大野口埃达克质闪长玢岩的成因及其地质意义

摘要

北祁连走廊南山北坡西水地区的加里东期大野口岩体中闪长玢岩地球化学的研究表明,该套岩石的SiO2>56%,Al2O3>15%,Na2O>K2O,富集大离子亲石元素和轻稀土元素,具正Eu异常,富集Sr元素、亏损重稀土元素Yb和Y,具有较高的Sr/Y值,表现出明显的埃达克岩的地球化学性质.结合岩体产出的时空位置,认为大野口岩体形成于奥陶纪与板块俯冲作用相关的俯冲洋壳部分熔融和壳幔岩浆混合作用.%Geochemical studies of diorite porphyrite in Xishui area of Zoulangnanshan within North Qilian Mountain show that the rock is characterized by SiO2>56%,Al2O3>15%,Na2O>K2O%,LILE and LREE enrichment,positive Eu anomalies,Sr enrichment, depletion of heavy rare earth elements Yb and Y,and higher Sr/Y ratios,showing obvious geochemical characteristics of adakite.Ac-cording to the regional geological study,the authors hold that Dayekou diorite porphyrite was formed in the Caledonian Ordovician period associated with subduction of the oceanic crust partial melting and crust-mantle magma mixing.