Journal of Tropical Oceanography ›› 2016, Vol. 35 ›› Issue (6): 46-57.doi: 10.11978/2016018CSTR: 32234.14.2016018

• Marine Geology • Previous Articles     Next Articles

Basin-mountain evolution, thermo-tectonic history and surface crustal recycling processes of the northern margin of the South China Sea

YAN Yi1, ALMATARI Ali Ahmed Ali1, 2, TIAN Zhixian1, QIAN Kun1, 2   

  1. 1. Key Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2016-02-23 Revised:2016-04-19 Online:2016-11-30 Published:2016-12-15
  • Contact: YAN Yi. E-mail: yanyi@gig.ac.cn
  • Supported by:
    National Natural Science Foundation of China (41476036)

Abstract: The continental margin of South China has a long and complex history that dates back to the Mesozoic when it formed part of an active “Andean type” margin associated with north-directed subduction of the Paleo-Pacific Plate. In the Paleocene, the margin experienced significant extension, leading to a complex passive margin. Whilst considerable research effort has been directed at explaining extension across the South China margin, and the age and mechanisms for opening of the South China Sea, relatively little attention has been paid to the impact of these processes on the evolution of the exposed South China continental margin. Coupling between the sedimentation in a basin and the unroofing-erosion in the surrounding orogens makes it possible to understand the basin-mountain evolution, thermo-tectonic history and surface crustal recycling processes by studying the detritus composition, geochemical characteristics of the basin sediments and the timing and rates of exhumation surrounding the orogens. The purpose of this study is to document the timing and rates of exhumation across the Pearl River Mouth region of the South China margin and the provenance of the basins in the northern margin of the South China Sea. Zircon fission track (ZFT), apatite fission track (AFT) and (U-Th)/He thermochronometric data show that the timing and pattern of rock uplift and erosion do not fit conventional passive margin landscape models that require youngest exhumation ages to be concentrated at or close to the rifted margin. The history of South China margin is more complex aided by weakened crust from the active margin period that immediately preceded rifting and opening of the South China Sea. Generally, the higher εNd values dominated by Yanshanian (180~67 Ma) zircon grains in sediments deposited prior to 25 Ma indicate the detritus in the northern margin of the South China Sea mainly eroded from Phanerozoic granitic sources exposed in coastal South China. Whereas the lower εNd values dominated by the Indosinian (257-205 Ma) zircon grains together with Yanshanian, Proterozoic and Archean population in the Miocene rock suggest that the main sources had evolved to inland South China by 25 Ma.

Key words: South China Sea, basin provenance, lower thermochronometry, fission track