Adakite:Its characteristics and implications

The similarity and difference between C -type adakitic rocks in eastern China and typical Adakite in the Pacific Ocean in respect to geochemistry and tectonic setting are discussed.Mesozoic inter-mediate-acid igneous rocks with adakitic signatures in eastern China are considered as the product of in-tracontinental magmatism.It is inferred that they originated by partial melting of basic rocks in the lower crust due to underplating of basaltic magma from the lithospheric mantle to the bottom of the thickened continental crust(50km)with cratonic affinity.The geodynamic implications of Adakite,especially C-type Adakite,are dealt with in the paper.Adakite can be considered as a new series of island-arc magma-tism and its discovery marks a major breakthrough in the petrological study and initiates a new way for the study of granitoids rocks.Several possible tectonic settings for the formation of Adakite are also dis-cussed.Adakite is a key to the study of crustal thickening and relevant events in geological history and the backward deduction of the composition of the lower crust.In addition,the relation of Adakite to mineral-ization is also discussed.