湘桂交界地区三江断裂带的变形时代及对泛非构造热事件的响应  

The Deformation Age of Sanjiang Fault Zone and Discovery of Pan-African Tectonic Thermal Events in Adjacent Areas of Hunan and Guangxi

作　　者：秦亚[1] 冯佐海[1] 邢全力 吴杰[1] 薛云峰 QIN Ya;FENG Zuohai;XING Quanli;WU Jie;XUE Yunfeng(Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi&Guangxi Key Laboratory of Hidden Metallic Ore Exploration,Guilin University of Technology,Guilin 541004,China)

机构地区：[1]桂林理工大学广西有色隐伏金属矿产勘查与新材料开发协同创新中心,广西隐伏金属矿产勘查重点实验室,桂林541004

出　　处：《高校地质学报》2022年第2期211-224,共14页Geological Journal of China Universities

基　　金：国家自然科学基金项目(42072259,42162018);广西自然科学基金项目(2018GXNSFAA281248,2019GXNSFDA245009)联合资助。

摘　　要：文章对三江断裂带的湘西通道长界橄榄辉石岩进行年代学研究,讨论了岩体的侵位时代、断裂变形时限及对泛非事件的响应。长界蚀变橄榄辉石岩侵入于丹洲群合桐组,发生强烈的绿泥石化、蛇纹石化和透闪石化蚀变。显微镜下,晚期绿泥石脉穿切早期蚀变矿物,显示多期蚀变的特征,暗示成岩后至少遭受两期构造热事件的影响。锆石U-Pb测年结果集中在441.0±11.0 Ma、546.5±8.5 Ma、774.3±3.9 Ma和820~1000 Ma。结合锆石阴极发光图像和稀土微量元素特征,进行锆石成因类型研究,774.3±3.9 Ma的锆石为最年轻的岩浆锆石,其年龄代表长界蚀变橄榄辉石岩的形成时代。820~1000 Ma的锆石为岩浆侵位过程中捕获物质的年龄。441.0±11.0 Ma的锆石为热液锆石,该年龄与区域NNE向断裂的变形时代一致,代表三江断裂带的活动时代。546.5±8.5 Ma的锆石亦为热液锆石,该年龄与泛非构造热事件的时代一致,表明研究区曾遭受到泛非构造热事件的影响。The chronology of the Changjie altered olivine pyroxenite of Tongdao area of western of Hunan province in Sanjiang fault is researched in this paper to discuss the emplacement age of rock, the deformation time of the fault and the response to the Pan-African event. Changjie altered olivine pyroxenite intruded into the Hetong formation of Danzhou group, which suffered intense chloritization, serpentinization and tremolite alteration. Microscopically, the late chlorite veinlets cut through the early altered minerals, showing the characteristics of multi-stage alteration and suggesting that they were affected by at least two tectonic thermal events after diagenesis. Zircon U-Pb dating results are concentrated at 441.0±11.0 Ma、546.5±8.5 Ma、774.3±3.9 Ma and 820-1000 Ma. 774.3±3.9 Ma is the youngest magmatic zircon age, which represents the formation age of the Changjie altered olivine pyroxenite. 820-1000 Ma is the age of captured zircons during magmatic emplacement. The hydrothermal zircon age of 441.0±11.0 Ma is consistent with the formation age of the regional NNE trending fault, which represents the active age of the Sanjiang fault. The age of 546.5±8.5 Ma is also hydrothermal zircon age, which is consistent with the age of Pan-African tectonothermal event, indicating that the research area was influenced by Pan-African tectonic thermal event.

关 键 词：热液锆石 变形时代 泛非构造事件 三江断裂带 湘桂交界地区 

分 类 号：P548[天文地球—构造地质学] P597[天文地球—地质学]