热带海洋学报 ›› 2019, Vol. 38 ›› Issue (4): 81-90.doi: 10.11978/2018108

所属专题: 南海专题

• 海洋地球物理学 • 上一篇    下一篇

跨南海西南次海盆OBS、多道地震与重力联合调查

汪俊1,2(),邱燕1,2,阎贫3,DELESCLUSEM4,王彦林3,PUBELLIERM4,聂鑫1,2   

  1. 1. 广州海洋地质调查局, 广东 广州, 510075
    2. 国土资源部海底矿产资源重点实验室, 广东 广州 510075
    3. 中国科学院边缘海地质重点实验室(南海海洋研究所), 广东广州 510301
  • 收稿日期:2018-10-17 修回日期:2010-01-10 出版日期:2019-07-20 发布日期:2019-07-21
  • 作者简介:汪俊(1983—), 男, 浙江省江山市人, 工程师, 硕士, 从事海洋区域地质构造研究, 主要技术手段为联合重、磁、反射及折射地震等地球物理资料进行综合地球物理建模。E-mail: wangjun19830726@163.com
  • 基金资助:
    中国地质调查局国家海洋专项项目((GZH201100205、DD20160138););国家自然科学基金项目((91855101、41876052).)

A joint investigation using OBS, multi-channel seismic and gravity data across the southwestern sub-basin of the South China Sea

Jun WANG1,2(),Yan QIU1,2,Pin YAN3,M DELESCLUSE4,Yanlin WANG3,M PUBELLIER4,Xin NIE1,2   

  1. 1. Guangzhou Marine Geology Survey, Guangzhou 510075, China
    2. Key Laboratory of Marine Mineral Resources, Ministry of Land and Resources, Guangzhou 510075, China
    3. CAS Key Laboratory of Ocean and Marginal Sea Geology (South China Sea Institute of Oceanology), Guangzhou 510301, Guangdong, China
  • Received:2018-10-17 Revised:2010-01-10 Online:2019-07-20 Published:2019-07-21
  • Supported by:
    China Geological Survey Program((GZH201100205、DD20160138););National Natural Science Foundation of China((91855101、41876052).)

摘要:

对跨南海西南次海盆及两侧陆缘的一条1050km长的、包括海底地震(OBS)、长排列多道地震和重磁在内的综合地球物理探测剖面(CFT)进行了构造成像和研究。在多道地震成像基础上建立了CFT剖面初始速度模型, 进而通过初至波层析成像方法反演了CFT剖面的速度结构模型, 在重力异常资料的约束下建立了CFT剖面的综合地壳结构模型。讨论了沿CFT剖面出现的下地壳高速体、龙门海山的低密度物质等地质问题。结果表明, 下地壳高速层在北部陆坡、西南海盆和南部南沙地块均有分布, 厚度在0~4km之间, 可能与陆缘下地壳物质和地幔物质熔融混合, 以及深海盆海底扩张期间构造拉伸导致地幔蛇纹岩化有关。

关键词: 南海西南海盆, 海底广角地震, 长排列多道地震, 层析成像, 下地壳高速体, 龙门海山

Abstract:

A 1050-km long comprehensive geophysical profile (CFT) was acquired across the conjugate margins of the southwestern sub-basin of the South China Sea, which includes 49 OBSs, 6- or 8-km long streamer, gravimeter, and magnetometer. Various refined processing procedures were applied to the aforementioned geophysical data; and a joint reflection and refraction seismic travel time inversion was performed to derive a 2-D velocity model of the crustal structure and upper mantle. Based on this new tomographic model and shipboard gravity data, a comprehensive crustal structure model was created. Finally, some interesting issues including High Velocity Layer (HVL) in the base of crust, an anomalous low density seamount (long-men seamount) along the CFT profile are discussed in this paper. HVL are widely distributed under the northern slope, southwestern sub-basin and Nansha block along the CFT profile, with the velocity varying from 7.0 to 7.5 km·s -1, and thickness between 0 and 4 km. HVL in the marginal lower crust might be derived from melting and mixing of lower crust material and mantle material, and HVL in the oceanic crust might have originated from serpentinization by tectonically dominated seafloor spreading.

Key words: southwestern sub-basin, wide-angle refraction seismic, long streamer multi-channel seismic, seismic tomography, high velocity layer of lower crust, Longmen Seamount