Timing of the formation of the Tianhuashan Basin in northern Wuyi as constrained by geochronology of volcanic and plutonic rocks  

作　　者：SU HuiMin MAO JingWen HE XiRong LU Ran 

机构地区：[1]State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences and Resources,China University of Geosciences(Beijing) [2]Institute of Mineral Resources,Chinese Academy of Geological Sciences [3]No.912 Geological Party,Jiangxi Bureau of Geology and Mineral Exploration and Development

出　　处：《Science China Earth Sciences》2013年第6期940-955,1092-1095,共16页中国科学（地球科学英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant No. 40930419);Special Research Funding for the Public Benefit Sponsored by MLR (GrantNo. 200911007)

摘　　要：The Tianhuashan Basin is one of the most important volcanic basins in the northern Wuyi,southeastern China,comprising two successive volcanic units,the Daguding Formation and the overlying Ehuling Formation,along with several small associated igneous intrusions.The Lengshuikeng super-large-scale Ag-Pb-Zn deposit,which is closely related to these volcanic-intrusive rocks,is located in the northwestern part of the basin.In order to understand the basin evolution and magmatism,we determined LA-ICP-MS U-Pb zircon ages for the volcanic successions and associated intrusive rocks.U-Pb zircon dating of volcanic units yielded precise ages of 144±1 Ma for crystal tuff in the lower member of the Daguding Formation,142±1 Ma for andesite within the upper member of the Daguding Formation,140±1 Ma for tuffite of the first(i.e.,lowermost) member of the Ehuling Formation,and 137±1 Ma for rhyolitic ignimbrite within the third volcano-stratigraphic member of the Ehuling Formation.Three types of intrusive igneous rocks(quartz syenite porphyry,K-feldspar granite porphyry,and rhyolite porphyry) yielded precise weighted mean 206 Pb/238 U ages of 144±1,140±1,and 140±1 Ma,respectively,suggesting that these intrusions along with the aforementioned volcanics were all emplaced during the Early Cretaceous.In addition,the weighted mean 206 Pb/238 U ages determined on zircon from two samples of a granite porphyry intrusion,which hosts ore mineralization of the Lengshuikeng Ag-Pb-Zn deposit,are 158±1 and 157±1 Ma,indicating emplacement in the Late Jurassic.These new geochronological results for igneous rocks of the Tianhuashan Basin constrain the timing of volcanic and plutonic activity in the basin,and have important implications for our understanding the tectonic history of the region,and for identifying metallogenic types and the timing of ore deposition of the Lengshuikeng deposit.The Tianhuashan Basin is one of the most important volcanic basins in the northern Wuyi,southeastern China,comprising two successive volcanic units,the Daguding Formation and the overlying Ehuling Formation,along with several small associated igneous intrusions.The Lengshuikeng super-large-scale Ag-Pb-Zn deposit,which is closely related to these volcanic-intrusive rocks,is located in the northwestern part of the basin.In order to understand the basin evolution and magmatism,we determined LA-ICP-MS U-Pb zircon ages for the volcanic successions and associated intrusive rocks.U-Pb zircon dating of volcanic units yielded precise ages of 144±1 Ma for crystal tuff in the lower member of the Daguding Formation,142±1 Ma for andesite within the upper member of the Daguding Formation,140±1 Ma for tuffite of the first（i.e.,lowermost） member of the Ehuling Formation,and 137±1 Ma for rhyolitic ignimbrite within the third volcano-stratigraphic member of the Ehuling Formation.Three types of intrusive igneous rocks（quartz syenite porphyry,K-feldspar granite porphyry,and rhyolite porphyry） yielded precise weighted mean 206 Pb/238 U ages of 144±1,140±1,and 140±1 Ma,respectively,suggesting that these intrusions along with the aforementioned volcanics were all emplaced during the Early Cretaceous.In addition,the weighted mean 206 Pb/238 U ages determined on zircon from two samples of a granite porphyry intrusion,which hosts ore mineralization of the Lengshuikeng Ag-Pb-Zn deposit,are 158±1 and 157±1 Ma,indicating emplacement in the Late Jurassic.These new geochronological results for igneous rocks of the Tianhuashan Basin constrain the timing of volcanic and plutonic activity in the basin,and have important implications for our understanding the tectonic history of the region,and for identifying metallogenic types and the timing of ore deposition of the Lengshuikeng deposit.

关 键 词：Cretaceous volcanic basin GEOCHRONOLOGY North Wuyi area Jiangxi Province 

分 类 号：P588.14[天文地球—岩石学]