摘要
广西钦防地区位于扬子地块和华夏地块结合带的西南段,是华南唯一的海相志留系与下泥盆统连续沉积出露区.对钦防地区志留系地层中的沉积岩展开了精细的LA-ICP-MS锆石U-Pb年代学分析和测试.分析结果表明,7个代表性沉积岩样品的年龄频谱图显示出了~2.5 Ga、~1.0 Ga、~0.47 Ga 3个明显的年龄峰值,暗示太古代全球地壳生长事件(~2.5 Ga)、格林威尔期造山运动(~1.0 Ga)以及早古生代构造事件(~0.47 Ga)在华南地区保存有记录.结合锆石的阴极发光图像特征和相关区域地质资料,推测~2.5 Ga、~1.0 Ga和~0.47 Ga碎屑锆石均主要来源于钦防地区东北侧的云开地块,钦防地区与华夏地块具有亲缘性,早古生代时期钦防地区可能为一夭折的裂谷,这一时期华夏与扬子地块西南端的分界线至少位于钦防地区的西北侧.
The Qinzhou-Fangchenggang area,located at the southwestern intersection between the Yangtze block and the Cathaysia block,is the only contiguous marine sedimentation during the period of Silurian to Early Devonian in South China.Detailed LA-ICPMS U-Pb dating analyses were carried out on detrital zircons of 7 Silurian sandstone samples from the QinzhouFangchenggang area.Age spectra of the 7 typical sedimentary rock samples show three significant age peaks:~2.5 Ga,~1.0 Ga and^0.47 Ga,indicating that the Archean global crustal growth event(~2.5 Ga),the Grenville orogeny(~1.0 Ga)and the Early Paleozoic tectonic event(~0.47 Ga)were recorded in South China.In combination with cathodoluminescence(CL)images and regional geological data,it is suggested that the detrital zircons of^2.5 Ga,~1.0 Ga and^0.47 Ga should be mainly derived from the Yunkai massif,southeastern Cathaysia block.Comparative analysis of age spectra of the Early Paleozoic sedimentary rocks from this study and Yunkai massif indicates that the Qinzhou-Fangchenggang area has an affinity to the Cathaysia block.These evidences imply that the Qinzhou-Fangchenggang area represented a failed rift during Early Paleozoic and the southwestern boundary between the Cathaysia block and Yangtze block is at least in the northwest of the Qinzhou-Fangchenggang area,rather than in the southeast area.
作者
蒙麟鑫
周云
蔡永丰
冯佐海
唐专红
蒙有言
麻艺超
Meng Linxin;Zhou Yun;Cai Yongfeng;Feng Zuohai;Tang Zhuanhong;Meng Youyan;Ma Yichao(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration&Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi,Guilin University of Technology,Guilin 541004,China;Guangxi Institute of Regional Geological Survey,Guilin 541003,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2020年第4期1227-1242,共16页
Earth Science
基金
广西自然科学基金项目(Nos.2017GXNSFAA198209,2015GXNSFBA139204,2015GXNSFDA139029,2018GXNSFBA281069)
国家自然科学基金项目(Nos.41503021,41572191).
关键词
钦防地区
早古生代
碎屑锆石U-PB年龄
沉积物源
地质年代学
Qinzhou-Fangchenggang area
Early Paleozoic
detrital zircon U-Pb age
sedimentary source
geochronology
