青海祁漫塔格地区牛苦头矿床和卡而却卡矿床B区花岗质岩石LA-ICP-MS锆石U-Pb年龄——对泥盆纪成岩成矿作用的指示

Geochronological study of granitoids from the Niukutou and B section of the Kaerqueka deposits,Qimantag area,Qinghai Province:Implications for Devonian magmatism and mineralization

牛苦头矿床和卡而却卡矿床是青海祁漫塔格地区重要的多金属矿床。利用LA-ICP-MS锆石U-Pb法测得牛苦头矿床花岗闪长岩成岩年龄为394.0±1.3Ma,卡而却卡矿床B区黑云母二长花岗岩的成岩年龄为406.4±4.2Ma。这些年龄与区内野马泉、乌兰乌珠尔及夏日哈木矿床成矿岩体的形成时代范围基本一致,说明青海祁漫塔格地区早、中泥盆世可能发生了大规模的岩浆作用和与之有关的成矿作用。结合区域地质特征和已发表的地质年代学及岩石地球化学数据可知,青海祁漫塔格地区早、中泥盆世处于后碰撞伸展的构造背景,暗示早、中泥盆世可能是青海祁漫塔格地区又一个重要的多金属成矿期。

The Niukutou and the Kaerqueka deposits are economically important in the Qimantag area of Qinghai Province （QA？ QP）. In this paper, the authors present new LA-ICP-MS zircon U-Pb ages for granitoids from these two deposits, which show that the emplacement ages of the Niukutou granodiorite and B section of the Kaerqueka biotite monzogranite are 394.0 ± 1.3Ma and 406.4±4.2Ma, respectively. These ages are consistent with those of granitic intrusions associated with the Yemaquan, Wulanwuzhuer and Xiarihamu deposits, indicating that Early and Middle Devonian is an important period for magmatism and mineralization of the QAQP. Combined with previously published data and geological features, the authors hold that Early and Middle Devonian magma-tism and related polymetallic mineralization occurred in a post-collision tectonic setting, implying that Early and Middle Devonian might have been another significantly metallogenic period for the QAQP.