内蒙古巴林左旗九井子蛇绿岩锆石U-Pb定年:对西拉木伦河缝合带形成演化的约束

发布时间：2018-03-03 13:55

本文选题：内蒙古东南部　切入点：西拉木伦河蛇绿岩　出处：《中国地质》2016年06期 　论文类型：期刊论文

【摘要】：本文对位于西拉木伦河蛇绿岩带东段的九井子蛇绿岩中辉长岩脉以及蛇绿岩的围岩开展了锆石U-Pb定年。结果表明辉长岩的形成时代为(274.7±1.7)Ma,MSWD=0.079,属于早二叠世晚期;结合前人地层、古生物、岩浆岩等方面的资料,表明内蒙古东南部早二叠世晚期还可能存在大洋盆地。与九井子蛇绿岩呈断层接触的粉砂岩碎屑锆石年龄大致构成4个峰值:2350~2700 Ma、1700~2100 Ma、370~470 Ma和250~290 Ma,通过与区域构造热事件的对比分析,表明其物源主要来自中朝古板块的北缘。粉砂岩中最小的锆石年龄为晚二叠世末—早三叠世初((249±4.7)Ma),该年龄与内蒙古东南部海相地层消失的时代、安加拉植物群和华夏植物群出现混生的时代、西伯利亚和中朝古板块古纬度曲线收敛的时代以及区域上与碰撞相关的岩浆岩形成时代大致相同,据此本文认为九井子蛇绿岩的构造侵位时代应为晚二叠世末—早三叠世初,同时也可能代表古亚洲洋的最终闭合时代。
[Abstract]:In this paper, zircon U-Pb dating of gabbro veins and surrounding rocks of ophiolite in Jiujingzi ophiolite located in the eastern section of the Xilamulunhe ophiolite belt has been carried out. The results show that the pyroxenite was formed at a age of 274.7 卤1.7 MaMSWDN 0.079, belonging to the late early Permian, and combining with previous strata, Information on paleontology, magma, etc., It is suggested that the oceanic basin may also exist in the late early Permian period in the southeast of Inner Mongolia. The zircon ages of siltstone fragments in contact with the ophiolite of Jiujingzi are roughly composed of four peak values: 2 350 Ma, 2 700 Ma, 1 700 Ma, 3 70 470 Ma and 250 0 0 Ma, respectively, through comparative analysis with regional tectonic heat events. The results show that the source material is mainly from the northern margin of the Middle Korean paleo-plate. The minimum zircon age in siltstone is 249 卤4.7 Ma-mau from late Permian to early Triassic, which is the age of the disappearance of marine strata in southeastern Inner Mongolia. The age when Angara flora and Cathaysian flora were mixed, the paleolatitude curve of ancient plates of Siberia and Central Korea converged, and the age of magmatic formation related to collision in the region were approximately the same. Therefore, the tectonic emplacement age of Jiujingzi ophiolite is considered to be the late Permian to early Triassic, and it may also represent the final closure of the Paleo-Asian Ocean.
【作者单位】：中国地质科学院地质研究所;东北亚矿产资源评价国土资源部重点实验室;中国地质调查局天津地质调查中心;吉林大学地球科学学院;
【基金】：国家自然科学基金项目(41102029,41472055) 中国地质调查局地质调查项目(12120115069301,DD20160201-01)联合资助~~
【分类号】：P597.3;P542;P588

【相似文献】