Journal of Tropical Oceanography ›› 2010, Vol. 29 ›› Issue (6): 162-169.doi: 10.11978/j.issn.1009-5470.2010.06.162cstr: 32234.14.j.issn.1009-5470.2010.06.162

• Marine geophysics • Previous Articles     Next Articles

Magnetic field of the northern South China Sea: its characteristics and tectonic significance

WU Zhao-cai1, GAO Jin-yao1, ZHAO Li-hong1, ZHANG Tao1, YANG Chun-guo1   

  1. Key Laboratory of Submarine Geosciences of State Oceanic Administration, Second Institute of Oceanography, State Oceanic Administration, Hangzhou 310012, China
  • Received:2009-06-30 Revised:2009-07-16 Online:2010-12-15 Published:2010-12-15
  • About author:吴招才(1980—), 男, 湖北省蕲春县人, 博士, 从事海洋地球物理和海底构造研究。E-mail: wzc_dh@163.com
  • Supported by:

    国家自然科学基金项目(40776036); 科技部“973”项目(2007CB411702); 我国近海海洋综合调查与评价专项(908-ZC-I-06)

Abstract:

According to the magnetic field of the northern of the South China Sea and its “reduction-to-the-pole”- anomaly, the area could be divided into four zones with different tectonic features from north to south. They are complex magnetic anomaly zone and high magnetic anomaly belt in the shelf, magnetic quiet zone in the slope, and magnetic lineation zone in the ocean ba-sin. The magnetic quiet zone could be divided further into three parts for inside magnetic quiet zone 1, inside magnetic quiet zone 2, and outside magnetic quiet zone. The depth of magnetic basement in the outside magnetic quiet zone is 6?7 km, between the inside magnetic quiet zone (8?10 km) and the lineation zone in the ocean basin (4?5 km). It may be the residue oceanic crust before the Cenozoic. Outside the magnetic quiet zone there is a high velocity layer  in the lower crust, which implies that the magnetic quiet zone is formed by under plating during rifting or pre-rifting. F2 fault is located in the shelf slope break, which is the northern border of the inside magnetic quiet zone. The fault may indicate the transformational border from continental crust to transitional crust in the northern South China Sea. F4 fault, located at the junction between lower continental slope and ocean basin, is the south border outside the magnetic quiet zone. F3 fault may indicate the location of continent–ocean boundary.

Key words: northern South China Sea, magnetic field characteristics, fault, magnetic quiet zone, high velocity layer in the lower crust