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

• 来源期刊: 科学通报（英文版）
• 年，卷（期）: 2009,（10）
• 页码范围: 1750-1758
• 页数: 9页
• 语种: 英文
• DOI: 10.1007/s11434-009-0214-3

摘要

Whole-rock Sm-Nd Isotopes were investigated for Cambrian-Ordovician strata from the Jinggangshan area beTween the Yangtze Block and Cathysla 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 ε<,Nd>(t) values of -13.9 to -7.9 and old Nd model ages of 1842 to 2375 Ma. In t<,DM>-t<,Str>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 Cathyaia Block. However, the Ordovician Jueshangou Formation and Dui'erehi Formation have ε<,Nd>(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-Ordovlcian 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.