Mesozoic Tectonic Deformation And Geological Implications In Malipo Area, Southeastern Yunnanprovince

Malipo in the southeast part of Yunnan province, located in the north of the Song Chay dome and in the southwest of the Southern China plate, has undergone periods of intense tectonic activities. There is a thrust nappe structure from SE to NW direction shown by tectonic deformation analysis in metamorphic rock and sedimentary layers.Inside the Song Chay dome, the extrusion caused the formation of two metamorphic sedimentary strata(Saxi petrofabric and Nanyangtian petrofabric) which presented as fault blocks in between the igneous rocks(Tuantian+Laochengpo gneissic granite and Nanlao tectonic gneiss). In the outer area of Song Chay dome, the allochthonous sequences(Cambrian strata and Devonian strata) were thrusted onto the autochthonous sequences(Permian strata and Triassic strata). The thrust nappe structure deformation is characterized by klippen, fault block, mylonite zone, inclined fold and mineral shear deformation. It changed the regional tectonic framework.According to both the isotope chronological studies and previous research results, this extrusion began after 220 Ma, and ended before 159 Ma. This extrusion shows the compression of Pacific plate and South China plates during the Mesozoic period. The tectonic interfaces,caused by this Mesozoic tectonic event,provided the migration pathway of fluid,and controled the distribution of the following tungsten polymetallic minerali zation.