内蒙古阿拉善北部陶豪托西圈辉长岩LA-ICP-MS锆石U-Pb年龄和地球化学特征

在内蒙古阿拉善地区北部庆格勒图附近零星分布着数个基性侵入岩体，陶豪托西圈辉长岩是其中最大的一个。早期资料显示，这些基性侵入岩可能形成于早古生代。2件陶豪托西圈辉长岩样品的LA-ICP-MS锆石U-Pb年龄结果一致．表明其形成时代为276-275Ma，相当于早二叠世晚期。地球化学特征表明，陶豪托西圈辉长岩中存在早期分离结晶所形成的斜长石的富集，而其中Nb的负异常可能是源区特征的反映，暗示着该岩体可能形成于俯冲背景下，而不是伸展环境下的产物。结合区域地质资料，阿拉善北部晚石炭世一二叠纪的岩浆活动存在幔源岩浆的强烈参与，这一时期该地区可能属于俯冲背景下的岩浆弧。

LA-ICP-MS zircon U-Pb age and geochemical characteristics of the Taohaotuoxiquan gabbro in northern Alxa, Inner Mongolia.

In Qinggeletu area of northern Alxa within Inner Mongolia, several mafic plutons are sporadically outcropped, of which the Taohaotuoxiquan gabbro is the largest one. These mafic plutons were previously considered to be Early Paleozoic in age. LA-ICP- MS zircon U-Pb dating of two samples from Taohaotuoxiquan gabbro yielded a consistent age of 276-275Ma, suggesting an em- placement of Early Permian. Geochemical characteristics of the Taohaotuoxiquan gabbro indicate that it contains some fractional crys- tallized plagioclase with the Nb negative anomaly inherited from its source, implying that this gabbro was formed in a subduction set- ting rather than in the continental rift. Combined with previous studies, the authors hold that a large amount of mantle-derived melt was involved in Late Carboniferous-Permian magmatism in northern Alxa, and this area might have been an arc in a subduction set- ting at that time.