The Madang Cenozoic sodic alkaline basalt occurred in the eastern margin of the Tibetan Plateau, where is a key tectonic transform region of Tibet, North China, and Yangtze blocks. The basalts are characterized by the...The Madang Cenozoic sodic alkaline basalt occurred in the eastern margin of the Tibetan Plateau, where is a key tectonic transform region of Tibet, North China, and Yangtze blocks. The basalts are characterized by the variation in SiO2=42%―51%, Na2O/K2O>4, belonging to the sodic alkaline basalt series. The rocks are enriched in Ba, Th, Nb, Ta, relative to a slight depletion in K, Rb in the trace and rare earth element (REE) spider diagrams that are similar to the typical oceanic island alkaline basalt. The Sr-Nd-Pb isotopic compositions suggest that they are derived from a mixed mantle reservoir. The western Qinling-Songpan tectonic region was controlled by Tibet, North China and Yangtze blocks since Cenozoic, therefore, the region was in the stage of the substance converge from the mantle to upper crust, producing a mixed mantle reservoir in the studied area. The Madang basalts occurred in the specific tectonic background, they result from partial melting of a mixed asthenospheric mantle reservoir in the western Qinling-Songpan tectonic node.展开更多
基金Supported jointly by the National Natural Science Foundation of China (Grant Nos. 40572050 and 40234041) and the Teaching and Research Award Program for Outstanding Young Teachers in Higher Education Institutions of MOE, China
文摘The Madang Cenozoic sodic alkaline basalt occurred in the eastern margin of the Tibetan Plateau, where is a key tectonic transform region of Tibet, North China, and Yangtze blocks. The basalts are characterized by the variation in SiO2=42%―51%, Na2O/K2O>4, belonging to the sodic alkaline basalt series. The rocks are enriched in Ba, Th, Nb, Ta, relative to a slight depletion in K, Rb in the trace and rare earth element (REE) spider diagrams that are similar to the typical oceanic island alkaline basalt. The Sr-Nd-Pb isotopic compositions suggest that they are derived from a mixed mantle reservoir. The western Qinling-Songpan tectonic region was controlled by Tibet, North China and Yangtze blocks since Cenozoic, therefore, the region was in the stage of the substance converge from the mantle to upper crust, producing a mixed mantle reservoir in the studied area. The Madang basalts occurred in the specific tectonic background, they result from partial melting of a mixed asthenospheric mantle reservoir in the western Qinling-Songpan tectonic node.
