GEOLOGICAL CHARACTERISTICS AND TECTONIC SIGNIFICANCE OF GONGHUDUGE GRANITE ROCK BODY IN SIZIWNAGQI, INNER MONGOLIA

The Gonghuduge granite rock body, which is tectonically located in the north margin of Sino-Korean platform,intruded Ordovician strata and was intruded by late Late Paleozoic granite. The K-Ar dating (306.4 Ma) of biotite shows that the rock is formed in the middle stage of Late Paleozoic era. The rock body is composed of mainly granodiorite and quartz-mica diorite. It is characterized by peraluminous rock, with high-Fe biotite. The Gonghuduge rock body belongs to crust-derived granite of S-type, formed in the post-collision-epirogenic movement in the later stage of the convergence of Sino-Korean and Siberian plates. The occurrence of the Gonghuduge granite is controlled by deep fault.