中国东部中新生代火山作用的pTtc模型与岩石圈演化

中国东北和华北地区中新生代火山岩的岩石化学研究表明 ,中新生代火山作用的深部过程均为逆时针的pTt轨迹 ,表现为岩浆源区从逐渐上升到下降的过程。中新生代火山作用的深部过程揭示的岩石圈演化历史为 :早侏罗世至早白垩世早期 ,岩石圈演化主要表现为逐渐减薄的过程 ,直至出现软流圈与地壳直接接触。从早白垩世晚期至中生代末 ,岩石圈演化为一增生过程。第三纪岩石圈演化为减薄过程 ,而到第四纪为岩石圈增生过程。中国东部现代岩石圈地幔是由中生代晚期 (K1末—K3)和第四纪两次增生事件形成的

pTtc MODEL OF MESOZOIC AND CENOZOIC VOLCANISMS AND LITHOSPHERIC EVOLUTION IN EASTERN CHINA

The petrochemical researches on Mesozoic and Cenozoic volcanic rocks in eastern and northern China indicate that the deep processes of Mesozoic and Cenozoic volcanisms all are a counterclockwise pTt locus, which corresponds with the upward to downward drifts of magma sources. The deep processes of Mesozoic and Cenozoic volcanisms reveal the history of lithospheric evolution. From early Jurassic to the early stage of early Cretaceous, the lithospheric thinning had been taken place, the asthenosphere could directly contact with the crust in the beginning of early Cretaceous. From the late of early Cretaceous to the end of Mesozoic era, the accretion of lithospheric mantle had been taken place. The lithospheric thinning was taken place again in Tertiary period. However, the accretion of lithospheric mantle was taken place during Quaternary period. The present lithospheric mantle in eastern China was formed in late Mesozoic (late of K 1-K 3) and Quaternary accretions.