The bojite occurs in the Mangya area, south margin of the Altun Mountains, shows typical calc-alkalic series trend. The intrusion is enriched in LREE,LILE ( Rb, Ba, Sr ), U, Pb, and depleted in HFSE ( Nb, Ta, Zr, Hf ), which is similar to the products of island-arc structure setting. Writers considered that the bojite magma originated from lithospheric mantle, the primary magma resulted from partial melting of mantle materials, and mixed with crust materials while the melt uprising. LA-ICP-MS zircon dating shows that the formation age of the bojites is 444. 9 ± 1.3 Ma ( WSMD＝ 0. 94 ), which suggests that subduction of oceanic crust occurred in southern margin of Altun Mountains in Late Ordovieian. So, this paper provides some important evidences for studying further formation and evolution of the Altun Tagh tectonic belt.%阿尔金茫崖地区发育的角闪辉长岩,属钙碱性岩石系列.岩体相对富集LREE、大离子亲石元素(Rb、Ba、Sr)以及U和Pb,亏损高场强元素(Nb、Ta、Zr、Hf),类似于岛弧环境产物.推测其源区为岩石圈地幔,原生岩浆通过幔源物质部分熔融产生,在上升就位过程中遭受地壳混染.LA-ICP-MS锆石U-Pb测年获得谐和年龄444.9±1.3Ma(WSMD=0.94),为岩体的形成年龄,指示阿尔金南缘在晚奥陶世末存在洋壳俯冲作用,为进一步研究阿尔金构造带的形成及演化提供了重要证据.
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