New advances in the geological study of the Qinling orogen

Abstract: During the Eighth and Ninth Five-Year Plan periods, major developments were made in geological studies of the Qinling-Bashan region: (1) creation of the new theory of choula (drawing) thrust sheet tectonics, which enriched and developed the diversity of the movement modes of the lithospheric plates or crustal blocks; (2) discoveries of N-S-trending uplift zones and sedimentary basins in the E-W-trending Qinling orogen, especially the discovery of the Taibai uplift zone and Baoji-Foping- Hannan uplift zone, which will bring about a radical change of our understanding of the tectonic framework of the Qinling Mountains and even east-central China; (3) recognition of two new types of orogen for the supracrustal layers, type-Ⅱ and type- Ⅲ, the former being E-W-trending orogens transformed from N-S-trending sedimentary basins and the latter being those formed by drawing-out and thrusting of deep tectonic sheets over Meso-Cenozoic continental sedimentary basins; (4) recognition of the existence of three types of sedimentary basins, three kinds of basin-range transformation, three development stages and three types (Ⅰ, Ⅱ and Ⅲ) of orogen; (5) reassessment of the tectonic natures and ages of the Shangdan, Mianlue and Erlangping tectonic belts and first proposition of the new view that the development of the Qinling orogen was controlled by three tectonic systems and went through four evolution stages and that the intracontinental orogen formed by drawing-out tectonism was the most important development stage; (6) first presentation of overpass structure; (7) discovery of some pre-Sinian metamorphic crystalline series and reassessment of the ages of some strata, especially the discovery of the Mesoproterozoic strata in the Xicheng lead-zinc ore field in the West Qinling, in which the superlarge Changba deposit is hosted; (8) presentation of the new concept of para-turbiditic fluid; and (9) advancement of a new geodynamic hypothesis concerning the tectonic evolution of the Qinling orogen and the continent of China.