TRACING THE THICKENING PROCESS OF CONTINENTAL CRUST THROUGH STUDYING ADAKITIC ROCKS:EVIDENCE FROM VOLCANIC ROCKS IN THE NORTH TIBET

Adakitic rocks can be produced through several different magmatisms, including crust and of delaminated lower crust section besides slab melting. In a continental setting, adakitic rocks suggest that their magmas were derived from low crust at depth over 40 km. Therefore, the adakitic rocks in continental setting indicate that the least thickness of crust is over 40 km. It is in Qiangtang area of the Tibetan Plateau that the adakitic volcanic rocks of the Cenozoic era have been found. Our study revealed that these adakitic volcanic rocks in the Qiangtang area were generated by lower crust melting and dehydration melting of delaminated lower crust section. The adakitic volcanic rocks of 40 Ma infer that the continental crust of the Qiangtang area in the Tibetan Plateau has been thickened to over 40 km, and the plateau likely started uplifting at that time.