A giant Late Mesozoic A-type granitoid zone occurred in east China can be divided into five sub -zones of two episodes. The products of the first episode(135～100Ma) include lower Yangzi zone,Northern Jiangsu-Jiaonan zone,Shanhaiguan zone and Nianzishan zone,and those of the second one(100～70Ma) are located at the Southeastern coast of China named Fujian-Zhejiang zone. They exhibit not only various rock assemblages but also obvious regional change in their emplacement patterns of the intrusives for the different zones and episodes. The study indicates that the A-type granitoids of the first episode were produced in the continent- continent collision transpression orogenic zone in the eastern Asia active continental margin where wide shearing tectonics was well developed (160～100Ma ), and emplaced in the places where the extensional jogs of P-shears and the collapse in the junction of P,T, and R shear zones were developed. which was generated by the intensive transtension in the pressure-shear stress field setting. The A-type granitoids of the second episode were produced in the collisional zone of the accretional terrane in the oblique subduction continental margin of southeast China,and related to the back--arc extension resulted from the Kula plate subducted beneath the Euroasian plate(10070Ma). The magmas emplaced in the areas of collapse which was generated by the differential uplifting and depression of the crust. Moreover, the extensional degree is possibly one of the important factor that constrained the formation of the A-type granitoids and affected the characteristics of the magma nature and emplacement.
Geological Journal of China Universities
A-type granitoid, tectonic constraint, Late Mesozoic, east China