Cenozoic magmatism in the northern continental margin of the South China Sea: evidence from seismic profiles

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• 作者：Qiao Zhang ; Shiguo Wu ; Dongdong Dong
• 刊名：Marine Geophysical Researches
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：37
• 期：2
• 页码：71-94
• 全文大小：44,240 KB
• 刊物类别：Earth and Environmental Science
• 刊物主题：Earth sciences
  Oceanography
  Geophysics and Geodesy
  Geosciences
  Offshore Engineering
  
• 出版者：Springer Netherlands
• ISSN：1573-0581
• 卷排序：37

文摘

Igneous rocks in the northern margin of the South China Sea (SCS) have been identified via high resolution multi-channel seismic data in addition to other geophysical and drilling well data. This study identified intrusive and extrusive structures including seamounts and buried volcanoes, and their seismic characteristics. Intrusive features consist of piercement and implicit-piercement type structures, indicating different energy input associated with diapir formation. Extrusive structures are divided into flat-topped and conical-topped seamounts. Three main criteria (the overlying strata, the contact relationship and sills) were used to distinguish between intrusive rocks and buried volcanos. Three criteria are also used to estimate the timing of igneous rock formation: the contact relationship, the overlying sedimentary thickness and seismic reflection characteristics. These criteria are applied to recognize and distinguish between three periods of Cenozoic magmatism in the northern margin of the SCS: before seafloor spreading (Paleocene and Eocene), during seafloor spreading (Early Oligocene–Mid Miocene) and after cessation of seafloor spreading (Mid Miocene–Recent). Among them, greater attention is given to the extensive magmatism since 5.5 Ma, which is present throughout nearly all of the study area, making it a significant event in the SCS. Almost all of the Cenozoic igneous rocks were located below the 1500 m bathymetric contour. In contrast with the wide distribution of igneous rocks in the volcanic rifted margin, igneous rocks in the syn-rift stage of the northern margin of the SCS are extremely sporadic, and they could only be found in the southern Pearl River Mouth basin and NW sub-sea basin. The ocean–continent transition of the northern SCS exhibits high-angle listric faults, concentrated on the seaward side of the magmatic zone, and a sharply decreased crust, with little influence from a mantle plume. These observations provide further evidence to suggest that the northern margin of the SCS is a magma-poor rifted margin.KeywordsIgneous rockSeismic imagingPassive continental marginSouth China Sea