中国岩石圈的基本特征

中国及邻区岩石圈结构构造十分复杂,并具有若干明显的特点:中国大陆地壳西厚东薄、南厚北薄,青藏高原地壳平均厚度为60~65 km,最厚达80 km;东部地区一般为30~35 km,南中国海中央海盆平均只有5 km;中国大陆地壳平均厚度为476 km,大大超过全球地壳392 km的平均厚度。中国大陆及邻区岩石圈亦呈西厚东薄、南厚北薄的变化趋势,青藏高原及西北地区岩石圈平均厚度为165 km,塔里木盆地中东部、帕米尔与昌都地区岩石圈厚度可达180~200 km。大兴安岭-太行山-武陵山以东,包括边缘海为岩石圈减薄区,厚度为50~85 km。西部岩石圈、软流圈“层状结构”明显,反映了板块碰撞汇聚的动力学环境;东部岩石圈、软流圈呈“块状镶嵌结构”,岩石圈薄,软流圈厚,反映了地壳拉张、软流圈物质上涌的特点,并在东亚及西太平洋地区85~250 km深处形成一巨型低速异常体。中国东部上、下地壳及地壳、岩石圈地幔之间普遍存在“上老下新”年龄结构。

Principal characteristics of the lithosphere of China

The lithospheric structure of China and its adjacent area is very complex and has several prominent characteristic features:the continental crust of China is thick in the west but thin in the east;and it is thick in the south but thin in the north.The continental crust of Qinghai-Tibet Plateau has an average thickness of 60-65 km with a maximum thickness of 80 km.while in the Eastern China it is 30-35 km and the minimum thickness is only 5 km in the central sea basin of South China Sea.The average thickness of the continental crust of China reaches 47.6 km,which greatly exceeds the average thickness of 39.2 km of the global crust.The lithosphere of Chinese continent and its adjacent areas also shows the general change tendency of thicker in the west and thinner in the east,and thicker in the south and thinner in the north.The lithosphere of Qinghai-Tibet Plateau and northwestern China has an average thickness of 165 km with a maximum thickness of 180-200 km in the central and east part of Tarim Basin,Pamir and Changdu areas.The vast areas to the east of the Da Xinggan-Taihang-Wuling mountains including the marginal sea are the lithospheric thinning regions where the thickness of lithosphere is only 50-85 km.In the western China the lithosphere and asthenosphere behave as an obvious layered structure,reflecting the dynamic background of plate collision and convergence;in the eastern China,the lithosphere and asthenosphere display a block mosaic structure,the lithosphere is thin and the asthenosphere is very thick,reflecting the features of crustal extension and upsurge of asthenospheric materials and forming a huge low velocity anomaly at 85-250 km in east Asia and west Pacific.There is an age structure of being older in the upper and younger in the lower between the upper and the lower crust and between the crust and the lithospheric mantle.