内蒙古乌拉特中旗德岭山地区石英闪长岩的锆石U-Pb年龄及地质意义

Zircon U-Pb Dating of the Quartz Diorite from Delingshan Area of Urad Zhongqi in Inner Monglia and Its Geological Significance

内蒙古乌拉特中旗德岭山地区石英闪长岩位于华北克拉通北缘中段晚古生代构造岩浆岩活动带中，对其进行了同位素地质年代学和地球化学研究，探讨了石英闪长岩形成时代和构造背景。利用锆石LA-MC-ICP-MS U-Pb法测得石英闪长岩的年龄为（278.1±1.6）Ma，表明其形成于早二叠世。其地球化学特征显示：属准铝质高钾钙碱性-钙碱性系列，I型花岗岩类；富集轻稀土（LREE）、大离子亲石元素（K、Rb、Sr），亏损高场强元素（Th、Ta），Eu异常不明显（δEu=0.61～1.46），形成于大陆活动边缘构造环境，是壳幔部分熔融的产物。结合区域上岩浆活动带出露的石英闪长岩地质特征，根据索伦山蛇绿岩带的出露位置和本区石英闪长岩产出的大地构造位置、形成环境及侵位时代，认为德岭山地区石英闪长岩的侵位反映了古亚洲洋俯冲消减于华北板块北缘之下及岩浆混合作用的岩浆事件。

The quartz diorite in Delingshan, Urad, Inner Mongolia is tectonically located in the central-northern margin of the North China craton and geochronology and petro-geochemistry of quartz diorite are investigated, and it＇s forming age and tectonic background are discussed. The age of the quartz diorite dated by LA-MC-ICP-MS U-Pb of zircons is（278.1±1.6）Ma,indicating that it was formed in the Early Permian. Petro-geochemical characteristics show that the quartz diorites are I-type granites, belonging to high-K cale-alkaline series, enriched in large ionic lithophile elements （LIL） of Rb, Sr and K, and depleted in High field strength elements（HFS） of Th,Ta with weakly negative Eu anomalies （δEu=0.61-1.46）. This kind of intrusions were formed in an active continental margins, derived from the melt mixing of crust and lithospheric mantle. Combined with geological feature of regional magmatic belt, tectonic settings, forming conditions and emplacement times of the quartz diorite, it is suggested that the quartz diorite of Delingshan intrusion was a result of the subduction of the Paleo-Asian Ocean beneath the northern margin of the North China craton.