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本文对青海南山构造带西段黑马河花岗杂岩体中的石英闪长岩和花岗闪长岩以及花岗闪长岩中的暗色微粒包体进行了详细的岩石学、岩石地球化学和LA-ICP-MS锆石U-Pb年代学研究。结果表明,花岗闪长岩及暗色微粒包体的结晶年龄分别为244.4±1.1 Ma和243.0±1.2 Ma,表明岩体形成于中三叠世早期。石英闪长岩和花岗闪长岩为准铝质高钾钙碱性系列,暗色微粒包体为高钾钙碱性—钾玄岩系列,稀土元素配分曲线均具有轻重稀土明显分异的右倾特征,具弱负Eu异常(δEu=0.65~0.83),富集大离子亲石元素(Cs、Rb、Th、K)和Pb,亏损高场强元素(Nb、Ta、Ti)和P、Ba负异常。岩相学和岩石地球化学特征指示黑马河花岗杂岩体具壳幔岩浆混合特征,形成于活动大陆边缘的俯冲环境,石英闪长岩为受俯冲流体交代的地幔楔部分熔融产生的基性岩浆演化的产物,花岗闪长岩则源自壳源岩浆与少量幔源岩浆的混合。黑马河花岗杂岩体是中三叠世早期宗务隆洋向南俯冲消减的岩浆记录。
In this paper, the detailed petrological, petrogeochemical and geochemical characteristics of quartzite and granodiorite in the Hemahe granodiorite complex in the western part of Nanshan structural belt of Qinghai Province and dark-colored granulite inclusions in granodiorite LA-ICP-MS zircon U-Pb chronology. The results show that the crystallization ages of granodiorite and dark particle inclusions are 244.4 ± 1.1 Ma and 243.0 ± 1.2 Ma, respectively, indicating that the rock mass formed in the early Middle Triassic. Quartz diorite and granodiorite are quasi-aluminum high-K calc-alkaline series, and the dark particle inclusions are high-K calc-alkaline-potassium basalt series. The REE distribution curves have the right-leaning (ΔEu = 0.65-0.83), enrichment of large ion lithophile elements (Cs, Rb, Th, K) and Pb, depleted high field strength elements (Nb, Ta, Ti) and P, Ba Negative abnormalities. Petrography and lithogeochemical characteristics indicate that the Hemahe granodiorite complex has crust-mantle magmatic mixing characteristics and formed in the subduction environment at the active continental margin. Quartz diorite is a basic mantle derived from partial melting of subducted wedge fluid The product of magmatic evolution, granodiorite is derived from the mixing of crustal magma and a small amount of mantle magma. The Hemahe granodiorite body is a magma record of the subduction of the Chongzuo Longyang subduction in the early Middle Triassic.