西藏与南亚地区大地水准面的场源及其动力效应初探

THE PRIME RESEARCH OF THE FIELD SOURCE AND DYNAMIC EFFECT BY THE GEOID IN TIBET AND SOUTH ASIA

根据西藏与南亚地区重力大地水准面的分布，对其相应的场源作了分析．其中除分别来自地球表层的地质构造和深部的核幔起伏外，剩下的主要部分可能是由密度较小的地幔热柱所形成，地幔热柱中心位置处于东经８２°和纬度０°附近，这和该处的热流密度异常位置十分吻合．所反演的热柱有关参数：上顶深１００ｋｍ，下底深２８５０ｋｍ，半径１００ｋｍ，与周围地幔的密度差为３０ｋｇ／ｍ３；另外，还讨论了在对流状态下该地幔热柱引起的动力效应，计算出对流速度和剪切力分别为４．８－４８ｃｍ／ａ和１１－１１０ＭＰａ，该力对我国岩石层应力场的构成和青藏高原的隆起有重要影响．

According to the distribution of the geoid in Tibet and South Asia. We analyse the corresponding field source and suggest that residual part of the geoid distribution is caused by the mantle Plume, whose center is located at λ=82°=0. This result fits well with the density anomaly of the heat flux in the mid-Indian Ocean Basin. The inversed difference of the density is -30 kg/m3. We also discuss the dynamic effect caused by the mantle plume in the convective state and compute the convective velocity and the shear stress which are 4.8-48 cm/a and 11-110 MPa respectively. This force plays an important role in the construction of the lithospheric stress field in middle and west China and the uplift of the Tibetan Plateau.