摘要
经过半个多世纪的努力,中国学者在青藏高原进行的地壳上地幔地球物理探测工作取得了巨大进展.累计完成长约45000km的深部地球物理探测工作,取得了许多科学数据,为探讨高原地壳上地幔结构、隆升机制和动力学研究奠定了基础.为比较全面反映中国学者多年来的工作成果,作者广泛收集资料,总结了中国学者在青藏高原地壳上地幔地球物理探测工作程度,并按照方法分类绘制了系列工作程度图.文中分别对地壳结构、上地幔的横向不均匀性、岩石圈的电性结构、青藏高原隆升机制、青藏高原地球动力学模型等几个方面所取得的主要成果做了概略的评述.已有资料表明:青藏高原的莫霍面埋深变化较大,且在几条重要缝合带莫霍面两侧都有断错;根据目前的探测结果,高原在20±5km埋深范围内普遍存在壳内低速高导层,速度一般为5.6~5.8km/s,电阻率约为1~10Ω.m,厚度一般为5~10km,但横向分布不连续.低速层与高导层的深度、厚度在趋势上一致,但不十分吻合.天然地震的研究结果表明,组成高原各个地块内部的地震各向异性方向大致相同,各地块的分界处各向异性方向往往有明显的变化;虽然对高原隆升机制还存在不同的看法,但至少认为高原是多期隆升、多种机制共同作用的结果这一点已达成共识.综合已有的地球物理调查成果,结合地质地球化学资料建立的高原地球动力学模型,形象地表达出青藏高原岩石圈的双向挤压变形模式.这些工作为研究青藏高原隆升和变形机制提供有价值的信息.
Chinese geophysicists carried on a series of geophysics research on the crust and upper mantle of Qinghai-Tibet plateau since 1958 and the total investigation length is about 45000km.In order to express the achievements in all aspects,the authors collect materials extensively,summarize the geophysical work on the crust and upper mantle of Qinghai-Tibet plateau,and draw a series of work degree figures according to different methods.This article gives a systematic account of the crustal structure,lateral heterogeneity of the upper mantle,resistivity of the lithosphere,uplifting mechanism of the Qinghai-Tibet plateau,geodynamic model and numerical simulations on lithosphere tectonic stress field.The available data shows that Moho is comparatively deep in this area.From south to north,Moho has different depths and features undulation beneath several main sutures.The results show that there is generally a discontinuous layer of low velocity and high conductivity in the crust of Tibetan plateau,which exists in 20±5km depth generally with a velocity of 5.6~5.8km/s,a low resistivity of 1~10Ω·m and a thickness of 5~10km.The low velocity layer and high conductivity layer are similar but not same in the depth and thickness.The natural earthquake research achievements show similar seismic anisotropy direction in every block on Qinghai-Tibet plateau,but there is obvious change at the boundary of blocks.Though there are different opinions regarding the uplifting history of Qinghai-Tibet plateau,it has been generally acknowledged that the plateau has undergone multi-phase uplift under multiple action mechanisms.On the basis of the results of comprehensive geophysical survey and interpretation and geological information,a geodynamic model was built to demonstrate the deformation mode of the plateau lithosphere.