Was there the "Mongol-Okhotsk Ocean?"-On tectonic evolution of Eurasian Continent-

点击翻译按钮获取中文摘要

It have been considered that the rocks of the eastern part of the Khangai. Khentei belt, Mongolia were composed of Devonian or possibly Carboniferous accretionary complexes including radiolarian chert and Carboniferous shallow marine sedimentary rocks(Tomurtogoo, 2003), but we revealed that the Carboniferous formation is mostly a part of the accretionary complexes. In addition, the following three shear zones are recognized in the eastern part of the Khangai. Khentei belt.(1) The rocks of the northern part of this belt are intensely sheared with asymmetric structures showing a top-to the North sense of shear. The tectonic foliation is generally sub-horizontal and is cut by syn-tectonic plutonic rock dated between 434 and 462 Ma. Added to this, a granitic clast of 277 Ma is included in a sheared rock of the Haraa terrane. These facts suggest that the rocks of the area were sheared twice :(a) at pre-Silurian, and(b) at least after Early Permian.(2) A shear zone trending NE with asymmetric structures showing a dextral sense of shear is developed in the northern part of the belt.(3) The sheared rocks of the southern part of the belt which trend NE with steep dipping have asymmetric structures indicating a sinistral sense of shear. These sheared rocks are intruded by syn-tectonic granitic rocks dated between 314 and 278 Ma. This shear zone cuts across the shear zone(2) and is disturbed by the shear zone(1b).