Nd Isotopes and Geochemistry of Phanerozoic Clastic Sedimentary Rocks from the Yangtze Block and Their Tectonic Implications

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• 作者：Zhou Lian ; Gao Shan ; Liu Yongsheng ; Corey Archer
• 关键词：Yangtze block ; Sm-Nd isotope ; trace element ; metasediment
• 刊名：Journal of China University of Geosciences
• 出版年：2007
• 出版时间：June 2007
• 年：2007
• 卷：18
• 期：2
• 页码：109-127
• 全文大小：2053 K

文摘

This article presents Sm-Nd and geochemical data on fine-grained sediments of the northern margin from the Yangtze block, China, to understand the variations of Nd isotopic compositions and crustal evolution history in this area. The results are as follows: (1) Nd isotopic compositions for clastic sedimentary rocks of the Middle-Late Proterozoic have relatively positive Nd(t) values (+ 2.72 to + 0.69), with Nd model ages from 1.38 Ga to 1.55 Ga, corresponding to the contemporaneous volcanic rocks from the Xixiang () Group. This indicates that the arc-related materials from Middle-Late Proterozoic dominate the provenances of the Middle-Late Proterozoic periods. (2) The gradual decrease in Nd(t) during the Cambrian-Carboniferous periods is likely to reflect the progressively increasing proportion of erosion materials from the Foping () and Qinling () complexes, corresponding to a gradually decreasing trend in the La/Th ratios. (3) A prominent increase in the Nd(t) value of the Late Permian strata probably reflects the significant incorporation of the mantle-derived materials. The trace element data are compared with data of the Emeishan () flood basalts. These data indicate that the volcanic dust has been added to the Late Permian strata during the Late Permian, represented by periods of extremely high Emeishan flood basalt activity in the south-eastern margin of the Yangtze block.