甘肃新疆交界地区四顶黑山镁铁质-超镁铁质岩的锆石U-Pb年龄及地质意义

摘要

采用高精度LA-ICP-MS锆石U-Pb同位素定年,获得甘肃新疆交界地区四顶黑山镁铁质-超镁铁质岩体中辉长岩的年龄为320.9Ma±3.0Ma,代表该岩体的形成时代为早石炭世,与镁铁质-超镁铁质岩紧密伴生的碰撞型花岗岩(二长花岗岩)的形成年龄为369.2Ma±2.7Ma,属晚泥盆世.结合区域研究资料对比,认为四顶黑山地区的碰撞作用应该在早石炭世之前结束,早石炭世已进入陆内裂谷岩浆作用阶段,为进一步探讨区域构造演化提供了更为丰富的年代学依据.%LA-ICP-MS zircon U-Pb dating of gabbro in Sidingheishan mafic-ultramafic rocks yielded an age of 320.9Ma±3.0Ma, which indicates the emplacement age of Sidingheishan mafic—ultramafic rock. The zircon U—Pb age of the monzogranite (collisional granite) associated with the mafic—ultramafic rock is 369.2Ma±2.7Ma. Combined with previous studies of regional geology, the authors infer that the collision period was ended before the early Carboniferous and Sidingheishan area entered into the stage of continental rift in early Carboniferous. The result obtained by the authors is important for the study of the tectonic evolution in this area.