【摘要】 LA-ICP-MS锆石U-Pb测年结果显示,库布苏南花岗闪长岩形成时代为(287±2)Ma,MSWD=0.15,包体年龄为(286±3)Ma,MSWD=0.22,两者在误差范围内完全一致,表明花岗闪长岩和暗色微粒包体是同时代形成的。包体是岩浆混合作用的产物,是过冷的镁铁质岩浆混入到中酸性岩浆中经快速冷凝的结果。在岩浆混合过程中,基性的包体岩浆和中酸性的寄主岩浆通过化学扩散发生成分交换,使包体受到了花岗闪长质岩浆的改造和同化。这可能就是库布苏南花岗闪长岩及其包体LA-ICP-MS锆石U-Pb年龄相同的原因所在。库布苏南花岗闪长岩形成的时代属于东准噶尔后碰撞深成岩浆活动的范围330～265Ma,略晚于东准噶尔乌伦古河碱性花岗岩和卡拉麦里碱性花岗岩的形成时代(300Ma左右),均为准噶尔周边地区后碰撞岩浆活动的产物,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。更多还原

【Abstract】 LA-ICP-MS zircon U-Pb dating of the Kubusunan granodiorite and its enclaves in the Kalamaili area, eastern Junggar, Xinjiang, indicates an age of 287±2 Ma (MSWD=0.15) for the granodiorite and an age of 286±3 Ma (MSWD=0.22) for its enclaves. The two ages are the same within the error limits, suggesting that granodiorite and dark enclaves formed synchronously. Enclaves resulted from magma mixing, i.e. they were the result of mixing of supercool mafic magma into intermediate-acid magma and then fast condensation. In the process of magma mixing,basic magma of enclaves and acid magma of host rocks changed their components by chemical diffusion, and thus enclaves were modified and assimilated by granodiorite magma. This might be why the Kubusunan granodiorite and its enclaves have the same LA-ICP-MS U-Pb zircon age. The ages of the Kubusunan granodiorite is in the range of 330-265 Ma for post-collisional magmatic activity in East Junggar, slightly younger than the age (300± Ma) of the Wulungu River alkali granite and Kalamaili alkali granite, all being the product of post-collisional magmatic activity at peripheries of East Junggar, and their formation and evolution indicate that underplating of post-collision mantle-derived magma in Junggar resulted in vertical growth of continental crust.更多还原