～(40)Ar/～(39)Ar Chronology And Geochemistry Of High-K Magmatic Rocks In The Nangqian And Mangkang Basins At The Northern Segment Of The Jinsha-Red River Shear Zone(JRRSZ)

One Cenozoic discontinuous arc-shaped high-K magmatism belt occurs along the JRRSZ. The author has taken the high-K magmatic rocks in the Nangqian and Mangkang basins at the northern segment of the JRRSZ as examples to date their 40Ar/39Ar ages and determine their genetic mechanism via elemental and isotopic tracing. The main conclusions of my thesis are described as below:1.Newly obtained high-quality 40Ar/39Ar age data suggest that the high-K rocks in the Nangqian and Mangkang basins at the northern segment of the JRRSZ were formed at the interval of 38.3-32.8 ?0.2 Ma.2. The formation of high-K magma was mainly controlled by batch partial melting, but affected by fractional crystallization.3. The evidently negative anomalies in Nb and Ta make clear that there is an input of the continental material into the mantle source, and the petrogenesis of high-K rocks are related to subduction.4. The tracing of elemental and Pb-Sr-Nd isotopic geochemistry of high-K rocks indicates that their source is an enriched continental lithospheric mantle, whose compositions are plotted in the junction area among EMI, EM2 and PREMA.5. The previous and newly-obtained evidence in geology, 40Ar/39Ar chronology and geochemistry suggests that the high-K magma was generated in the setting of continental subduction induced by the large-scale SE-treading extrusion of Indochina in the Cenozoic Indo- Asian collision...