江南西段新元古代板块运动机制及其地球动力学演化研究

Under the theoretical framework of modern plate tectonics, using advanced techniques and analysis means of geochemistry, isotopic geology and geochronology, this program will principally focus on scientific problems of Neoproterozoic plate tectonism and geodynamic evolution to carry out a systematic study in the western Jiangnan region of SE Yangtze plate. The studying contents are mainly the following five aspects: (1) the Precambrian basement and the unit division of plate tectonics in the northern Guangxi, eastern Guizhou and northeastern Hunan areas, (2) location of plate boundary and sutute zone between Yangtze and Cathaysia plates, (3) subduction-accretionary and colliosion process and kinematics of polyphase ductile deformation, (4) post-collision tectonism-magmatism-sedimentation and (5) reconstriction of temporal sequence of tectonic evolution and of geodynamical model. This program will interpret and answer the following problems: (1) the geological features and evolution of the Precambrian basement in the western Jiangnan region, the constitution and spatial-temporal relation of active continantal margin, (2) the location of sutute zone of Yangtze and Cathaysia plates, (3) confirming collision-collage process and kinematic sense of ductile deformation, (4) post-collision intraplate system of tectonism, magmatic activity and the sedimentary basin, and (5) re-constructing tectonic framework of Neoproterozoic trench-arc-basin system and plate evolution model of the western Jiangnan region. Furthermore, this program will compare the geometrical, kinematic and magmatic features with the eastern Jiangnan region. By aforementioned researches, our studied results will provide important constraints on the geological evolution of the early Earth for South China.

以研究相对薄弱的江南西段为研究对象，选择桂北、黔东、湘东北3个区段为重点解剖区，围绕新元古代板块运动机制及其地球动力学演化核心问题，运用当代板块构造理论和先进的定时定量测试技术和方法，开展江南西段基底构造和板块构造单元划分、板块边界位置、俯冲-碰撞增生过程及其构造变形运动学、后造山期构造-岩浆-沉积作用、构造演化时序等内容的研究。通过研究，查明江南西段基底组成与演化，诠释新元古代活动大陆边缘的物质组成和空间配置，弄清拼合-增生期的运动学动向，阐明新元古代板块运动机制和俯冲-增生过程，厘定碰撞拼合带位置，重建新元古代沟-弧-盆构造格架，了解拼合后构造转换及其板内岩浆活动特征，恢复构造时序，探索江南东、西两段构造异同，为建立华南地区地球早期板块构造与大陆动力学演化模型提供科学依据。

江南西段新元古代板块构造研究薄弱，争论较大。本项目选择桂北、黔东、湘东北3个区段为重点解剖区，围绕新元古代板块运动机制及其地球动力学演化核心问题，借助野外地质调查、岩石学、大地沉积学、岩石地球化学、同位素地质学和年代学等方法，开展研究区新元古代基底构造和板块构造单元划分、俯冲-碰撞增生过程及其构造变形运动学、板块边界位置、早古生代陆内沉积-构造变形-花岗岩浆事件特征及其对板块格局的再造、构造演化时序等内容的研究。通过研究，取得6项作用成果。① 追索到了江南西段基底多期构造演化信息，查明中国东南部是一个多地体构造格局，厘定了两种类型的造山带：板块边缘造山带和板内造山带。② 查明了江南西段新元古代活动大陆边缘的物质组成和空间配置，阐明了新元古代板块运动机制和俯冲-增生过程，发现华南首例蛇绿岩型斜长岩（848Ma），重建了新元古代沟-弧系（870-830 Ma）构造格架。③ 厘定了碰撞拼合带位置，为诸暨-龙游-东乡-萍乡岭上-祁东田家冲-全州茶林-桂林龙胜-永福断层，弄清了增生-拼合期的运动学动向，查明了后造山花岗岩浆活动（830-820Ma）特征。④ 发现可靠证据，确定了两期前泥盆纪变质作用,时间分别是900-835 Ma和435±5 Ma。⑤ 通过华南早古生代陆内沉积-构造变形-花岗岩浆作用的深入研究，确证华南不存在早古生代深海大洋，地质证据不支持早古生代大洋俯冲/增生作用的认识，华南早古生代造山作用是是全球板块围限下的陆内造山作用的结果。⑥ 重建了江南西段新元古代俯冲-增生和拼合过程，构建了新一代江南地区新元古代板块构造演化模式。.. 2017年获国家自然科学二等奖（排名第四）。项目培养出了5位博士。研究成果在国内外期刊上发表，计国际SCI期刊18篇，国内核心3篇。