The Caledonian Tectonic-Sedimentary Evolution Process in Eastern Qinling Orogenic Belt

Jiang Xiaojun; Ren Jishun; Zhou Dingwu; Zhao Lei; Liu Renyan; Sun Huiyi

Abstract：As the volcanic-magmatic-metamorphic events related to the Caledonian subduction-collision are widely distributed in northern Qinling orogenic belt, Caledonian orogeny was believed to be limited there, and there is no response to Caledonian orogeny in southern-central Qinling orogenic belt, owing to the continuous/parallel unconformable"soft collision"between the Devonian and underlying strata.In this paper, deformation differences and discontinuous loss features of contact relationship between the Devonian and underlying strata of 22outcrop sections in southern-central Qinling orogenic belt are investegated.In addition, the SHRIMP U-Pb geochronology and sedimentary environment on the"Silurian red strata"in unconformities are analyzed.It is indicated that the contact relationship between the Devonian and underlying folded basement strata (Pt3-S1) is a regional angular unconformity (regional micro-angular unconformity) in general, and the stratigraphic hiatus shows pronounced differences from north to south in eastern Qinling orogenic belt.Whats more, different tectonic deformation features are presented in upper and lower strata.It is believed that the age of"Silurian red strata"in unconformities is the Middle-Later Silurian (S2-3, <435Ma) along Guanfang-Gongguan in Xunyang County.It should be front sedimentary response with the foreland basin formed by eastern Qinling Caledonian orogeny.It is confirmed that Caledonian orogeny induced strong folding orogeny in all Qinling orogenic belt, which will help us to get a better understanding for Caledonian orogenic-sedimentary evolution process in eastern Qinling mountains.