Sm-Nd isotopic compositions of Cambrian-Ordovician strata at the Jinggangshan area in Jiangxi Province: Tectonic implications  

作　　者：SHEN WeiZhou LING HongFei SHU LiangShu ZHANG FangRong XIANG Lei 

机构地区：[1]State Key Laboratory for Mineral Deposits Research, College of Earth Sciences and Engineering, Nanjing University, Nanjing 210093,China [2]Geological Survey Institute, Jiangxi Province, Nanchang 330030, China

出　　处：《Chinese Science Bulletin》2009年第10期1750-1758,共9页

基　　金：Supported by National Natural Science Foundation of China (Grant Nos. 40634022 and 40572118);the Project of Ministry of Education of China (Grant No. 20060284008)

摘　　要：Whole-rock Sm-Nd isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area between the Yangtze Block and Cathysia Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low εNd(t) values of –13.9 to –7.9 and old Nd model ages of 1842 to 2375 Ma. In tDM-tStr diagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of mat- ters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathysia Block. However, the Ordovician Jueshangou Formation and Dui’ershi Formation have εNd(t) values of –10.5 and –7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovician sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.Whole-rock Sm-Nd isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area between the Yangtze Block and Cathysia Block in South China. These strata were deposited as a greatly thick unit of muddy-sandy laminas with intercalated carbonate and organic carbon-bearing layers. They have low εNd（t） values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In tDM-tStr diagram, they are far away from the concordant line but fall within the evolution zone of the Proterozoic crust of South China. This indicates that the Cambrian-Ordovician strata are mainly composed of matters eroded from ancient Paleoproterozoic crust that may mainly consist of continental-derived detrital sediments with high maturity in the Cathysia Block. However, the Ordovician Jueshangou Formation and Dui＇ershi Formation have εNd（t） values of -10.5 and -7.9 at the higher end of the above range and Nd model ages of 1842 to 2059 Ma at the lower end of the above range. This suggests involvement of more detritus that were eroded from the relatively juvenile crust from Late Paleoproterozoic to the Early Neoproterozoic. All the Nd model ages for the Cambrian-Ordovician sedimentary rocks in the Cathysia Block and the southeastern margin of the Yangtze Block are older than 1800 Ma, suggesting that no material from the Early Paleozoic depleted mantle-derived magmas was involved in these regions.

关 键 词：ND同位素 井冈山地区 地层沉积 奥陶系 寒武系 同位素组成 构造意义 Sm 

分 类 号：P588.3[天文地球—岩石学] TE271[天文地球—地质学]