内蒙古敖汉旗辉绿岩脉体LA-ICP-MS锆石U-Pb年代学——对赤峰-开原深断裂活动的指示

ZIRCON LA-ICP-MS U-Pb GEOCHRONOLOGY OF THE DIABASE DIKES IN AOHAN QI, INNER MONGOLIA: Indication for the Activity of Chifeng-Kaiyuan Deep Fault

摘要: 辉绿岩脉作为来源于地幔的脉体，可作为深断裂活动的标志.在赤峰敖汉旗1：5万区调工作中，在邢家窝铺古元古代宝音图群中识别出近东西向展布的辉绿岩脉.辉绿岩脉锆石U-Pb LA-ICP-MS年龄显示603~521 Ma、450 Ma、259~262 Ma、237 Ma、（167.4±3.0）Ma等5组年龄.其中最小年龄（167.4±3.0）Ma代表了辉绿岩脉体的形成年龄.反映了赤峰-开原深断裂在中侏罗世的活化；其余几组年龄也与赤峰地区不同期次的岩浆活动相对应.结合前人资料总结了赤峰-开原深断裂的形成与演化.

Abstract: Diabase dikes, which are derived from the mantle, can be used as an indicator of deep fault activities. During the 1:50000 geology survey in Aohan Qi area, Inner Mogolia, the authors identified near east-west extended diabase dikes in the Paleoproterozoic Baoyintu group in Xingjiawopu. The zircon U-Pb LA-ICP-MS dating of the diabase dikes show five age groups:603-521 Ma, 450 Ma, 259-262 Ma, 237 Ma and 167.4±3.0 Ma. The youngest age (167.4±3.0 Ma) represents the cooling age of the dikes, indicating the activation of Chifeng-Kaiyuan deep fracture in Middle Jurassic. The other ages are also corresponding to the magmatic activities of different periods in Chifeng area. The formation and evolution of the Chifeng-Kaiyuan deep fault are summarized by combination with previous literatures.