湘西南-桂北交界地区加里东期基性岩的发现及其地质意义

湘西南-桂北交界地区属于江南造山带(或称之为钦杭结合带)西南段的重要组成部分,该区与Rodinia超大陆聚合与裂解有关的岩浆活动十分强烈,但至今还没有加里东期基性岩存在的报道。采用LA-ICP-MS锆石U-Pb法对湘西南—桂北交界地区首次发现的加里东期变辉长辉绿岩进行了年代学研究。结果表明,变辉长辉绿岩形成于(421.9±7.8)Ma,为加里东期岩浆活动的产物。该基性岩的发现及其年龄的确定;并结合区域上的研究结果表明,扬子板块和华夏板块结合带(钦杭结合带)西南段可能存在有从新元古代至早古生代的双向洋陆俯冲-碰撞过程。

Discovery of Caledonian mafic rocks in southwestern Hunan-northern Guangxi border area and its geological significance

The southwestern Hunan-northern Guangxi border area is an important part of the southwestern segment of Jiangnan orogenic belt (so-called Qinzhou-Hangzhou joint belt). There is a very strong magmatic activity related to theSassemblySand break-upSofSRodinia supercontinent, but Caledonian mafic rocks have not been found in this area. In this paper, geochronology of Caledonian metamorphic gabbro-diabase discovered firstly in southwestern Hunan-northern Guangxi border area was studied by using LA-ICP-MS zircon U-Pb method. The research results showed that the metamorphic gabbro-diabase is developed during(421.9±7.8)Ma,and it is the product of Caledonian magmatism activity. The discovery of Caledonian mafic rock and the determination of its era, and in combination with the regional research results, we consider that there was likely a double ocean-continentSsubduction-collision event occurred during Neoproterozoic to early Paleozoic time.