Two phases over-thrusting nappe in Shanyang-Zhashui-Xunyang-Ankang region of the South Qinling and the basic characteristics of Ⅱ-type orogenic belt

The Shanyang-Zhashui-Xunyang-Ankang tectonic beltlying in 108°30'～110°,and between Shangxian-Danfeng and Mianxian-Luey ang (or Dabashan) tectonic belts,is Ⅱ-type orogenic belt that was formed in Palaeozoic-Triassic by the transf omation from N-Strending intraplate oceanic sedimentary basin.It is different from Wudang-Shangnan tectonic belt to it seast and Foping -Hannan tectonic belt to its west in the composition and structure.The tectonic pattern produced by over-thrusting from south to north at the beginning and the over-thrusting from north to south late in Shanyang-Zhashui-Xunyang -Ankang region of the South Qinling is completely from the thin-skinned structural model in which the region was slide-thrusted toward Sichuan basin from north to south.This paper also discussed the basic features of Ⅱ-type orogenic belt.