Nature of Lower Crust and Crust-mantle Exchange

摘要

Based on the petrological approach in combination with geophysical model and experimental or calculated data of Vp & Vs for the rocks, the crust-mantle petrological structure of three geotectonic units of china are presented by this paper . From oceanic crust through continental collision belt, with rapid increasing crust thickness, the mineral facies of the lower crust is changed from normal igneous or green-schist facies through amphibolite and granulite facies to eclogite facies, in correspondence with which the composition is changed from basaltic through andesitic to granitic, the compositional trend is called "granitization" resulted from the basaltic eclogite crust recycling back into the mantle .However, from the continental collision belt to the craton or through continental rifting to the oceanic crust, the crust thickness, mineral facies and composition of the lower crust are developed oppsitely, the compositional trend is called "basification" generated by the basaltic magma underplating into the lower crust from the mantle.