Southwest Boundary of Yangtze and Cathaysia Blocks:Constraints from the Luojiashan Gabbro in Yingyangguan Region,Northeastern Guangxi  

作　　者：Ya Qin Zuohai Feng Jiaming Zhu Yonggao Huang Jie Wu Yun Zhou Yunfeng Xue Chunzeng Wang 

机构地区：[1]Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Eficient Utilization of Resources by the Province and Ministry,Guilin University of Technology,Guilin 541004,China [2]Jiangsu Tuojia Engineering Design and Research Co.,Ltd.,Nanjing 211100,China [3]China Chemical Geology and Mine Bureau Henan Branch,Zhengzhou 450000,China [4]University of Maine at Presque Isle,Presque Isle,Maine 04769,USA

出　　处：《Journal of Earth Science》2024年第5期1447-1463,共17页地球科学学刊（英文版）

基　　金：funded by the Natural Science Foundation of Guangxi Province(Nos.2022GXNSFAA035570,2022GXNSFBA035463);the National Natural Science Foundation of China(Nos.42162018,42072259);the Innovation Project of Guangxi Graduate Education(No.YCBZ2021065)。

摘　　要：The Luojiashan gabbro is a newly discovered mafic pluton emplaced in the Neoproterozoic Yingyangguan Formation in Yingyangguan region of northeastern Guangxi,South China.Comprehensive whole-rock geochemical and zircon geochronological and Hf isotopic analyses are performed on the gabbro and comparisons are made with the coeval mafic-ultramafic sills and dikes located in Longsheng region of northern Guangxi in order to understand the magmatic origin,evolution,and tectonic setting of the Luojiashan gabbro and to address the location of the suture zone of the Southwestern Jiangnan Orogen(SJO).LA-ICP-MS zircon U-Pb ages obtained from the Luojiashan gabbro show that it was emplaced at~770 Ma.The gabbro contains abundant inherited zircons aged at 0.9-1.3 Ga,consistent with age spectrum of the Cathaysia Block.Chondrite-normalized REE pattern,primitive mantle-normalized trace element spider diagram,incompatible element ratios of Nb/Ta,Zr/Hf,La/Nb,Ba/Th,Th/La,and Ba/La,and Th/Yb-Ta/Yb discrimination diagram of the gabbro are indicative of OIB-like geochemical characteristics and of derivation from partially melted garnet peridotite of the asthenospheric mantle.Tectonic discrimination based on the trace and rare earth elements also indicate that the Luojiashan gabbro was emplaced in a within-plate extensional rift setting,probably as a result of Rodinia supercontinent dismantling,lithospheric thinning,and underplating and upwelling of the asthenospheric mantle.Based on zircon age,Hf isotopic data and comparison between northern and northeastern Guangxi,it is suggested that the Yingyangguan region was tectonically situated in a different tectonic locale from the Longsheng region of northern Guangxi at about 770 Ma during the post-orogenic mafic-ultramafic magmatic event,with the former within the Cathaysia Block and the latter along the southeast margin of Yangtze Block.The suture between the Yangtze and Cathaysia blocks must be located between Yingyangguan of northeastern Guangxi and Longsheng of northern Guangxi.

关 键 词：GEOCHRONOLOGY inherited zircon Luojiashan gabbro SUTURE Yingyangguan tectonic 

分 类 号：P588.124[天文地球—岩石学] P534.3[天文地球—地质学] P597.3