Initial Exploration to Mesozoic Basin—Orogen Dynamical Coupling of "Sanjiang"(Nujiang River—Jinsha River—Lancang River) Region,Western Yunnan

The coupling relations on dynamic mechanism between basin and adjacent orogenic belt are a research front of continental dynamics. The current typical basin—orogen pattern of the Sanjiang region (means three rivers,i.e.:Nujiang River—Jinsha River—Lancang River) is an ideal region to carry out this study. The conversion from foreland basin to rift basin of the Simao basin is involved with orogenic evolution. Therefore,it could be a breakthrough point of this research. The research methods include analysis to basin—orogen coupling process and its sedimentary responses,geophysics and geochemical characteristics of igneous rocks. Studies have shown that its Meso—Cenozoic basin—orogen evolutional history include three phases:basin orogen transition(T1—T2),orogen control basin (T3—E1) and basin—range covariation (T3—E1); The Simao lacustrine basin responds deep dynamical process by facies migration,sequences formation,deformation of basement and sedimentary cycle; the velocities structure section of lithosphere reveals that lower crust and lithosphere mantle under the Simao basin have a higher P wave velocity,and the Moho interface seems deeper; in addition,combining with characteristics of magmatic movement sequence and geochemistry,writers consider that basic magma underplating,lithosphere delamination and subduction slab-off might be the deep dynamical models of the basin conversion.