Geological Evolution And Dynamics Of The Mianlue-A'nyemaqen Tectonic Zone , Central China

Qinling Mianlue belt, a composite faulted structure zone, was located in the southern magin of Qinling-Dabie erogenic belt of the Central Orogenic System in China. The belt is another suture zone in the Qinling erogenic belt and a huge structure zone formed faults of superimposition Mesozoic-Cenozoic structure, extending from the East Kunlun belt through Huashixia, Maqen, Maqu, Nanping, Wenxian, Kangxian, and Mianlue area to south magin of Dabie. It is a macroscopic composite faulted structure zone along China continent, an important subduction-collision suture zone of subsidiary ocean basin of north side in Eastern Paleo-Tethys, representing main site of Indosinian welding of North China Block with Yangtze Block. This thesis mainly focus on structure, composition and evolution of the Mianlue-A'nyemaqen zone in Wenxian-Nanping-Maqu region and A'nyemaqen region with comprehensive research of the structure geology, petrology, sedimentology, geochemistry and geophysics, by which some new points are achived,1. Mianlue-A'nyemaqen zone presently was preserved as an EW to NWW-striking gigantic multi-layerd overthursting faulted zone in southward arcuating, which can be divided into Kangxian-Wenxian-Nanping Sections, Nanping-Diebu-Maqu Section and Maqu-Maqen Section (also termed as A'nyemaqen belt). The Kangxian-Wenxian-Nanping Section represents a southward multi-layered overthrusting faulted structural system. The Diebu-Maqu Section is overlapped in the South by the Bailongjiang steep-angle overthrusting system but crop out in the west as composite overthursting zone comparable in structure with the west counterpart. The major thrusting interface of the Kangxian-Wenxian-Nanping overthursting system is the Dongbeicun-Wenxian-Lueyang fault, making up a southward mid-to-steep angle arcuate thursting system, which can be 5 structural elements, 1) northern magin overthrusting structure; 2)Qiaotou-sanhekou overthrusting structure; 3)Nanping-Heihe overthrust-decollement structure; 4) major suturing zone, presently represented as Tazang-Wenxian-Linjiang-Pipasi overthrusting structure belt; 5)major overthrusting zone at the northern margin of Bikou Block. In Maqu-Nanping area and the northern part of Rergai Block, as the overlapping of Bailongjiang thrust nappe over the Triassic sediment of Rergai Block, possible relic Ophiolite and related igneous rocks are locally absent. The A'nyemaqen overthrusting system in the west displays 2 characteristics, 1) syn-collisional southwards imbricated overthrusting structure; 2) post-collisional low-angle allochthonous thrusted slices, exampled by C3-P] block limestone thursted nappe near Huashixia-Shixia, which construct overlapped composite thrust system in both horizontal and vertical sections.2. The Mianlue-A'nyemaqen belt is proven to be a tectonic suturing zone, where deformation can be divided into 2 stages corresponding to the subducting and collision, respectively. The deformation in early stage of subducting is characterized by southwards low-angle ductile shearing and lower-depth horizontal shearing thrust. Deformation in Early stage of collision is characterized by N-W compressnal isoclinal folds, representing northwards subducting in the Mianlue-A'nyemaqen belt. In later collisional stage is featured by southwards overthrust and laevorotatory shearing. Two type of melange are recognized in A'nyemaqenarea, one of which is ophiolitic melange formed by tectonic jumbling associated with subduction and collision of rocks in different origins and ages, another type is associated with sedimentary processes and experienced later deformative modifications.3. The Dur'ngoi Ophiolite is recognized from A'nyemaqen area, which yields typical depleted REE pattern and 40Ar/39Ar plateau age of 345.3h7.9Ma, with an isochronal age of 336.d;7.1Ma. Together with fossils discovered in this area, the formation age of Dur'ngoi Ophiolite is constrained within early Carboniferous period. Regional investigations provide preliminary recognitions of oceanic island basalt (OIB)...