首页|U-Pb zircon geochronology of basaltic pyroclastic rocks from the basement beneath the Xisha Islands in the northwestern South China Sea and its geological significance

U-Pb zircon geochronology of basaltic pyroclastic rocks from the basement beneath the Xisha Islands in the northwestern South China Sea and its geological significance

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As one of the micro-blocks dispersed in the South China Sea(SCS),the basement of the Xisha Islands has rarely been drilled because of the thick overlying Cenozoic sediments,which has led to a confused understanding of the pre-Cenozoic basement of the Xisha Islands.Well CK-1,a kilometer-scale major scientific drill in the Xisha Islands in the northwestern SCS,penetrated thick reefal limestone(0-888.4 m)and the underlying basement rocks(888.4-901.4 m).In this study,we present the zircon U-Pb ages of basement basaltic pyroclastic rocks from Well CK-1 in the Xisha Islands of the northwestern SCS to investigate the basement nature of the Xisha micro-block.The basement of Well CK-1 consists of basaltic pyroclastic rocks on the seamount.The zircon grains yielded apparent ages ranging from ca.2 138.9 Ma to ca.36 Ma.The old group of zircon grains from Well CK-1 was considered to be inherited zircons.Two Cenozoic zircons gave a weighted mean 206Pb/238U age of(36.3±1.1)Ma,Mean Squared Weighted Deviations(MSWD)= 1.2,which may represent the maximum age of the volcano eruption.The Yanshanian inherited zircons(116.9-105.7 Ma and 146.1-130.2 Ma)from Well CK-1 are consistent with the zircons from Well XK-1,indicating that the basement of Chenhang Island may be similar to that of Well XK-1.We propose that the Xisha micro-block may have developed on a uniform Late Jurassic metamorphic crystalline basement,intruded by Cretaceous granitic magma.

South China SeaXisha Islandsbasaltic pyroclastic rockszircon

Yu Zhang、Kefu Yu、Shiying Li

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Guangxi Laboratory on the Study of Coral Reefs in the South China Sea,Guangxi University,Nanning 530004,China

Coral Reef Research Center of China,Guangxi University,Nanning 530004,China

School of Marine Sciences,Guangxi University,Nanning 530004,China

Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Science,Guangzhou 510301,China

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National Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaNational Natural Science Foundation of ChinaGuangxi Scientific ProjectsGuangxi Scientific ProjectsGuangxi Youth Science Fund Project under contractStartup Foundation of Guangxi University

420305024209004142166003AD17129063AA172040742019GXNSFBA185016XBZ170339

2024

10.1007/s13131-023-2198-2

海洋学报(英文版)
中国海洋学会

海洋学报(英文版)

CSTPCD
影响因子：0.323
ISSN：0253-505X
年,卷(期)：2024.43(2)
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