南海海盆残留扩张中心地壳速度结构对比及构造意义

发布时间：2018-01-08 17:00

本文关键词：南海海盆残留扩张中心地壳速度结构对比及构造意义　出处：《科学通报》2017年21期 　论文类型：期刊论文

【摘要】：南海西北、西南和东部3个次海盆停止扩张之后都存在岩浆活动,扩张中心有多个海山.为了研究海山和扩张中心的地壳结构特征,本文使用穿越南海西北次海盆扩张中心的广角地震剖面(测线OBS 2006-p1),针对海盆区域,通过P波二维地震射线追踪正演,获得了西北次海盆垂直扩张方向的深部速度结构,讨论了西北次海盆及其扩张中心深部地壳结构特征;并结合南海东部次海盆和西南次海盆横穿扩张中心的海底地震仪(ocean bottom seismograph,OBS)剖面,对不同海盆的地壳结构进行了对比研究,获得了扩张后期岩浆活动对洋壳改造的新认识:(1)发现西北次海盆地壳具有明显的洋壳性质,莫霍(Moho)面埋深为11~12 km(从海平面起算),地壳厚度为6~8km,速度为5.7~7.0 km/s.扩张中心轴部双峰海山为西北次海盆扩张之后岩浆活动的产物;(2)西北次海盆、东部次海盆、西南次海盆东北部沿垂直扩张脊方向地壳速度结构均有明显的横向变化,在扩张中心处都表现为洋壳厚度增大约1 km,莫霍面埋深增大,表明后期岩浆活动对地壳结构有较大的改造作用.
[Abstract]:Magmatism occurred in the northwest, southwest and eastern part of the South China Sea after the three subbasins stopped spreading. There are several seamounts in the spreading center. In order to study the crustal structure characteristics of the seamounts and the spreading centers. In this paper, the wide-angle seismic profile (OBS 2006-p1), which passes through the spreading center of the subbasin in the northwest of the South China Sea, is used to trace the forward seismic ray through the P-wave 2-D seismic ray in the basin area. The deep velocity structure in the vertical spreading direction of the Northwest subbasin is obtained, and the characteristics of the deep crustal structure of the Northwest Subbasin and its spreading center are discussed. The ocean bottom seismograph-OBSs section of the subbasin in the east and southwest of the South China Sea is combined with the sea floor seismograph. A comparative study of the crustal structure of different basins has been carried out, and a new understanding of the alteration of the oceanic crust by magmatic activity in the late stage of the expansion has been obtained. (1) it is found that the crust of the northwest subbasin has obvious oceanic crust properties. The surface depth of Moho Moho is 1112km (from sea level) and the crustal thickness is 6m ~ 8km. The velocity is 5.7 ~ 7.0 km / s. The bimodal seamounts on the axis of the extension center are the product of magmatic activity after the expansion of the northwest subbasin. (2) the crustal velocity structures along the vertical spreading ridges in the northwest subbasin, the eastern subbasin and the northeast part of the southwest subbasin have obvious lateral changes, and the thickness of the oceanic crust increases about 1 km at the spreading center. The increase of Moho depth indicates that the late magmatic activity has great influence on the crustal structure.
【作者单位】：国家海洋局第二海洋研究所国家海洋局海底科学重点实验室;国土资源部海底矿产资源重点实验室;浙江大学地球科学系;
【基金】：国土资源部海底矿产资源重点实验室开放基金(KLMMR-2014-B-08,KLMMR-2014-B-07) 国家自然科学基金(41406052,41576037,41176046,41506048,91228205) 全球变化与海气相互作用专项(GASI-GEOGE-01) 科技基础性工作专项(2013FY112900)资助
【分类号】：P736.1
【正文快照】： *联系人,E-mail:ouyang7727@163.com;zhenli318@vip.sina.com;xdwei_922@126.com国土资源部海底矿产资源重点实验室开放基金(KLMMR-2014-B-08,KLMMR-2014-B-07)、国家自然科学基金(41406052,41576037,41176046,41506048,91228205)、全球变化与海气相互作用专项(GASI-GEOGE-01)

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