中国大陆岩石圈厚度分布研究

利用不同物理性质所估计的岩石圈厚度可能具有不同的地球动力学意义。大陆岩石圈等效弹性厚度往往只与岩石圈内部的某些岩层相关,因此它可能不代表一般意义上的岩石圈厚度。地震学岩石圈厚度虽然有较高的精度,但依赖于人为地对岩石圈的定义;并且其具有的短时间尺度效应决定了它与长时间尺度的岩石圈概念不一致。热学岩石圈厚度体现了长时间尺度上的岩石圈热学作用,因此其厚度定义的标准是较合理的。地震-热学岩石圈厚度研究利用地震波速反演得到的温度数据按照热学岩石圈标准来对岩石圈厚度进行研究,具有地震学和热学岩石圈厚度两者的优点,是较合理的对岩石圈厚度的估计。中国大陆地震-热学岩石圈厚度分布有如下特点:(1)中国东部岩石圈较薄,厚度约100 km,其中包括中国东北、中朝克拉通、扬子克拉通东部和华南造山带;(2)青藏高原和塔里木克拉通以南地区的厚度变化较大,厚度约在160~220 km;(3)三大克拉通的岩石圈厚度有较大区别,扬子克拉通的核心最厚达约170 km,塔里木克拉通的核心厚度约140 km,中朝克拉通的厚度约100 km;(4)昆仑秦岭造山带的岩石圈上地幔内部较复杂,可能有大面积的部分熔融;(5)整个大陆岩石圈厚度分布并没有显示出与地壳年龄的线性相关关系,却表现出了与大地构造格局的直接关系。受板块碰撞强烈影响的地区,岩石圈较厚;受大洋俯冲带影响较强的地区,岩石圈较薄。

Review on lithospheric thickness research of the Chinese continent

Lithospheric thicknesses determined from different physical properties have different geodynamic significances.The effective elastic thickness of continent can correspond to only a part of the lithosphere,not to the total lithosphere.Seismic information of the lithosphere provides high resolution,but a short-time elastic effect.Thermal information of the lithosphere shows long-time effects, and therefore the thermal definition of the base of the lithosphere is better than the definition using other information.A seismic-thermal definition of the base of the lithosphere uses temperature from inverted seismic velocities,and thus has advantages of thermal and seismic definitions,and provides a more reasonable estimate of lithosphere thickness.The distribution of the seismic-thermal lithosphere thickness within the Chinese continent is very complex and shows the following properties:(1) eastern China,including the northeast China,the Sino-Korean craton,the east Yangtze craton and the south China orogen,has thin lithosphere with a thickness of ~100 km;(2) the lithospheric bases of the Qinghai-Tibet plateau and south to the Tarim craton are at a depth range of about 160～220 km and show strong lateral variation;(3) the lithospheric thicknesses of three large China cratons are different,e.g.,~170 km for the core of the Yangtze,~140 km for the Tarim,and ~100 km for the Sino-Korean;(4) the variations in lithospheric thickness do not show obvious correlation with crustal geologic age,but do show dependence on tectonic settings.