东准噶尔库布苏南岩体中闪长质包体特征及地质意义

Characteristics and Geological Significance of Microgranular Dioritic Enclaves in Kubusunan Granodiorite form Kalamaili Area,Junggar,Xinjiang

新疆东准噶尔卡拉麦里地区库布苏南晚古生代后碰撞准铝质过铝质花岗闪长岩体中广泛发育大量的暗色微粒闪长质包体。岩石学、矿物学、主量元素和微量元素地球化学研究表明,包体在地球化学特征上表现为与寄主花岗岩既相互联系又受其制约。库布苏南花岗闪长岩体具有低锶初始比值I(Sr)和正εNd(t)值,表明花岗岩的来源有地幔物质参与,而大量发育的暗色微粒闪长质包体是壳幔岩浆混合作用最直接的证据,微粒包体是基性源岩部分熔融作用形成的残余体。与准噶尔碱性花岗岩一样,载荷包体的准铝质过铝质花岗岩是晚古生代后碰撞阶段构造岩浆活动的岩石类型之一,其形成和演化标志了准噶尔地区后碰撞幔源岩浆底侵作用导致大陆地壳垂向生长的过程。

A large number of microgranular dioritic enclaves occur in some post-collisional metaluminousperaluminous granites, in Kubusunan orebody, in Kalamaili area , eastern Junggar, North Xinjiang. Petrological and geochemical researches reveal that the enclaves and the host granites are related to each other and restricted with each other. Kubusunan granite is chracterized by low ^87Sr/^86 Sr initial values and high εNd （t） values, indicating its origin partly from mantle rocks. The number of microgranular dioritic enclaves is the direct evidence for crust-mantle magma mixing, thus showing that enclaves are the residual formed from the partly fusing of basic magma. Consequently , these enclaves in common with Junggar peralkaline granite are products of post-collisional magmatic activity in late-Paleozoic. The formation and evolution of both enclaves and host granites in Junggar prove that the process of vertical growth of continental crust resulted from the underplating of post-collisional mantle-derived magmas in late-Paleozoic.