摘要
研究发现，南海北部陆缘地壳厚度从陆架、陆坡至深海平原呈阶梯状减薄。上地壳薄，下地壳厚，上地壳厚度占整个地壳厚度的百分比在１６．０％～４４．９％之间，约为１５～１３。下地壳下部存在高速地壳层，陆缘东部普遍存在，中部和西部则零星出现；推测这种地壳层在新生代前的地壳中已存在，但厚度较薄，在新生代张性构造运动中，熔融的上地幔基性岩浆侵入到地壳底部，或进入下地壳，冷却后形成高速地壳层。陆缘地壳结构存在横向变化，反映了改造陆缘地壳结构的新生代张性构造运动强度之横向变化。还发现陆缘地壳结构和广东—福建沿海地区的地壳结构存在较大差异，反映它们可能是由不同陆块经碰撞、缝合而形成的，所以，香港—南澳断裂是一条古缝合线。
オe collected twoship seismic data,deep seismic sounding data and seismic sonobuoy data on the northern margin of the South China Sea,and made a synthetical research on the crust structure of the margin.We find that the crust of the margin thins gradually from the shelf through the slope to the abyssal.The upper crust is thinner than the lower crust.The percentage of thickness of the upper crust in the all crust is 160～449%,about a fifth to third.In the lower part of the lower crust there exist the highervelocity crust layers(V=70～74km/s),widely occurring under the east part of the margin but sporadically under the middle and the west parts.We infer that the layers existed under the margin before Cenozoic,but the then thickness was thinner than today.In the Cenozoic tectonic movements,the basic magma from the partly melting upper mantle intruded into the base of the crust,or into the lower crust and formed the highervelocity layers after cold down.There are traverse changes in the crust structure,and Cenozoic tectonic movements which reformed the crust structure of the margin were such traverse changes.We yet find that there exist differences in the crust structure between the coast area of the Fujian—Guangdong Provinces and the northern margin of the South China Sea,reflecting that it might be two blocks which collided first and then sutured together in geological time.Therefore,the Nan’aoHongkong fault may be an ancient suture zone.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1998年第2期1-16,共16页
Marine Geology & Quaternary Geology
关键词
地壳结构
高速地壳层
地壳减薄
南海
陆缘
crust structure highervelocity crust layer tensional tectonic movement suture zone northern part of the South China Sea
