Geochronology and geochemical composition of the Early Cambrian sedimentary strata in the Cathaysia block: Implications for its provenance and tectonic setting
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    Abstract:

    The Early Paleozoic sedimentary records of the Cathaysia block are of great significance for understanding the role of the South China block in the evolution of the Gondwana supercontinent. In this study, zircon geochronological and elemental geochemical investigations are carried out for the Lower Cambrian Bacun Group in the Shenwan area, Zhongshan City of the Guangdong Province. The results show that detrital zircon ages of metaargillaceous siltstone in the Bacun Group can be divided into six groups: 4034~3122 Ma, 2765~2250 Ma, 1765~1443 Ma, 1126~901 Ma, 884~773 Ma, and 595~547 Ma, with the weighted average age of the youngest group of detrital zircon constrains the maximum sedimentary age of the Bacun Group to 551±4 Ma. The Hf isotopic features of zircon constraining that the provenance of the Bacun Group might be dominated by recycling of ancient crustal materials, associated with small amount of juvenile crustal rocks. The chemical index of alteration (CIA) and the index of compositional variability (ICV) of metasiltstone and metamudstone from the Bacun Group are 79. 8~86. 4 and 0. 39~0. 87, respectively, suggesting that the provenance has experienced extensive chemical weathering. The Bacun Group samples show strong enrichment in incompatible elements but depletion in Ni, Cr, and Co, indicating that the provenance of the Bacun Group may be dominated by felsic rocks under active continental margin tectonic setting. Comparing the age composition of detrital zircon in the Bacun Group with the other contemporaneous continental blocks in the world, it is suggested that the Bacun Group may represent the sedimentary response of the orogeny during the assembly of the Gondwana supercontinent from Late Neoproterozoic to Early Paleozoic, supporting the view that the Cathaysia block is located in the northern margin of Gondwana supercontinent, close to the Northern Indian block and the Qiangtang terrane.

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CHEN Weixiong, XU Qiong, TONG Xirun, GU Tao, SAN Feixue, QIU Xiaofei.2023. Geochronology and geochemical composition of the Early Cambrian sedimentary strata in the Cathaysia block: Implications for its provenance and tectonic setting[J]. Acta Geologica Sinica,97(7):2157-2175

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History
  • Received:May 02,2022
  • Revised:July 10,2022
  • Adopted:October 24,2022
  • Online: July 24,2023
  • Published: