【摘要】 通过对无水石榴石橄榄岩地幔的绝热减压部分熔融模型进行详细的数学推导,本文建立了准确的数学表达式以定量描述伸展因子、地幔部分熔融系数以及熔融体厚度之间的动力学关系。在详细的地球化学研究基础上,认为软流圈的部分熔融是济阳坳陷新生代火山岩的来源,并利用该模型对济阳坳陷新生代伸展裂陷阶段形成的熔融体厚度进行了预测,取得了与深部地球物理探测较为接近的结果。认为中下地壳中赋存的高导低速体是软流圈熔融体释放气体后聚集的结果,是盆地内分布的火山岩的直接源区。更多还原

【Abstract】 Up to now,it is difficult to quantitatively describe the real geodynamic relation be-tween continental lithosphere stre tching and magmatism originated fro m partial melting of the mantle.According to detailed mathematical deductions,this paper establishes the exact ex-pression to quantitatively describ e the geodynamic relation among exte nsion factor,mantle frac-tion coefficient and melting thickn ess,based on adiabatically decompr ession partial melting model of mantle with anhydrite garnet peridotite.On the basis of exact study on geochemistry character of the volcanic rocks in Ce nozoic of Jiyang depression,Bohai Bay basin,this paper deduces the partial melting of asthenosphere should be the magma source.Then the geody-namic relation is used to predict the melting thickness formed in this sta ge.The result is quite close to that from deep geophysical o bservation,i.e.the predicted distribution of melting thickness is consistent with the low-velocity body distributing in the m id -and lower crust.This is the evidence for the low -velo city body originating from magma flu id concentration from asthenosphere after releasing CO 2 and He.更多还原