Orggenic Processes Of The Inner Mongolia-Yanshan Area In Eastern China During The Late Late Paleozoic-Mesozoic

Inner Mongolia—Yanshan area orogenic belt in Eastern China, which with the tectonic evolutional background from the Archean to the early Paleozoic, was formed as a compound orogenic belt during the late Late—Paleozoic—Mesozoic. Piror to the orogeny, it was a plate subduction—collision evolutional processes of continent—island arc—island arc—continent be- tween Siberian and Sino—Korean active continental margins. The orogenic process started . from P₁²â€”P₂¹ In different time, the tectonic evolution was accompanied with various sedimen- tary basins such as the remnant island arc basin, the molasse basin, the up—piled basin and fault basins etc. When P₂—T₂, in this region, the strong and wide ductile shear extended to EW direction and guard—like fold, "A"type fold, sliding fold, reverse fold and so on devel- oped. Within the Inner Mongolian orogenic belt, the ductile shear zones were built up at 246. 3 Ma—197. 4±3.8Ma ( K—Ar isostopic age). Also, in Yanshan area, the formation of the ductile shear zones grew during 256. 10±0. 56—202. 0Ma±(³⁹Ar/⁴⁰Ar ). In T₃—J₁, the piled—up coal—bearing basins in Inner Mongolia and other regions took shape. At J₁—J₂, the brittle thrust systems developed from Sunite—Xilinhaote—Baiyinbaolige line verging toward south and north respectively. Also, from the north to the South, the compressive shortenings are descent from 65% to 20%, until non—deformation. And, from the north to the south, in Inner Mongolia area, the evolutional time and the vergences of the tectonic deformation are concordant with Yanshan region. The tectonic framework is ductile shear—sliding fold defor- mation ( fold nappe tectonics ) pried up the upper brittle thrust nappe tectonics.From J₂ on (161Ma±), in Inner Mongolia—Yanshan area, the geodynamics changed into the Circum Pacific territory appeared as the reverse clockwise ductile shear rotation, fold and thrust nappe as well as.The regularity of the petrochemical composition changes during the process of the my- lonites formation can be found that the components of the mylonite and their protoliths are in- crease or decrease or a little change at different time, for various types of mylonites, as well as in progressively deformational process. The ductile shear zones were built up on the different P—T—τenvironment: within the Inner Mongolia coUisional zone, P=1.5—2.5kbar, T=320°—400℃, highÏ„; In Yanshan and the south of Inner Mongolia tectonic belt, P=4.5—6. 5kbar, T=480°—620°, lowÏ„.With the ductile state formed by the thermal—magmatism, the stress and the energy to- ward the stress descent direction passed on from the plate collision belt to the relatively stable continental block by the dislocation glide ( climb ) within the crystalline, the fluid action, slid- ing media supported by schist materials, the sliding space by feldspar, quartz ere rotational mortar texture.The various kinds of intensive magmatic intrusion such as the mantle—derived magma- tism, the crust anatexis ere related and compared with the formation and the tectonic evolution in different time. As well as, the stress of the deformation on the upper—middle crust is con- troverse relationship to the upper mantle evolutional geodynamics.