Late Paleozoic-mesozoic Granites Origin And Its Tectonic Settings Analysis Of Inner Mongolia Wula Mountain

Late Paleozoic-Early Mesozoic geological evolution of the global historical process is a very important stage, marked by a collision with Carboniferous Gondwana Laurasia in Hercynian period; Late Triassic to form a unified final super-continent. On Laurasia, the Siberian Plate and North China Plate collage process has long been concerned by many geologists.The study area of this thesis is the middle of the northern margin of the North China Plate, the study is Wula Mountain granites of Late Paleozoic- early Mesozoic,on the basis of previous full collection of relevant geological information on the region of 1: 50000 regional geological surveys, field rock samples collected in the field in the region, and geochemical studies. Through a comprehensive study, the Late Paleozoic-Early Mesozoic granites Wula Mountain region is divided into Dahuabei rock and West Shadegai rock, according to geochemical analysis and zircon SHRIMP dating results for different Causes and tectonic environment of rock in the north, Siberia two plates collage process were studied and analyzed, characterized as follows:Dahuabei granite located in the western part of the North China Taipei margin Wula Mountain region. Constructed from the middle position for mainly granite and syenite outcrops adamellite, is an important area of research of ancient Asian Paleozoic oceanic plate and the North China Plate interactions. LA-ICP-MS zircon U-Pb dating of 332.6±1.1Ma get emplacement age, silicon-rich rock, quasi aluminum-weakly peraluminous, high alkali, relatively rich in potassium, calcium belongs to the alkaline series, poor iron, magnesium, calcium, phosphorus, manganese; varying degrees of enrichment of Rb, Th, U, Pb, Zr, Hf, Sm, loss of Ba, Ta, P, Ti, high field strength elements Nb, Sr content is low; light rare earths enrichment, rightist type HREE distribution patterns, and low total rare earth, light rare earth fractionation strong HREE fractionation obvious, obvious negative anomaly, with high score feature exclusive I-type granites. Post Dahuabei granite formation in ancient Asian Ocean plate during subduction arc to the north stretch squeeze the transition to active continental margin tectonic environment background.West shadegai rock tectonic position of Wula Mountain region is the western part of the northern margin of the North China craton, located within Hadamengou molybdenum ore field range, lithology consists of Archean gneisses and Triassic granite. Geochemistry of high performance silicon(Si O2 mass fraction of 74.08%- 75.95%), potassium-rich(K2O /Na2 O value of 1.20 to 3.39), alkali-rich(K2O+Na2O is 7.03%~8.46%), weak peraluminous(Al2O3 mass fraction of 11.22%~13.06%, A/CNK value of 1.002~1.284), Rittman index belong to the calc-alkaline; LREE enrichment, HREE(LREE/HREE 27.83-19.84), Eu slightly depleted(δEu is 0.36 to 0.53); trace element enrichment of Rb, Th, U, Pb, Zr, Hf, Sm, loss Ba, Ta, P, Ti, high field strength elements Nb, Sr content is low, A-type granites have characteristics; the use of LA-ICP-MS for Shad cap rock were dating, the use of the sample measured 30 zircon data points, 206Pb/238 U age statistical weight average of 231.13±0.85 Ma, belongs to the three Permian. Permian ancient Asian Ocean closed, ocean basins North China plate and between the Siberian plate shrinks, Siberia ancient super continent and the ancient continent collision docking, mantle-derived mafic magma formed by the collision caused by the invasion and early old basement extensional tectonics crustal partial melting, become the main mechanism for the formation of the power of rock Shadegai.In summary, late Paleozoic-Early Mesozoic granites of the study area basically reflects the geological evolution of the northern margin of the North China Plate stage Wula Mountain region. In the Hercynian stage of geological development, since the late Early Ordovician, the area always uplift and erosion, but the crust activity to the Early Carboniferous time zone strongly, mainly as a strong magmatic activity, appeared early Carboniferous quartz diorite and granite intrusions; the Indo geological evolution stage, early stage of the survey area Indosinian basically inherited the late Hercynian tectonic pattern when, in the late Triassic, there was a strong north-south squeeze orogeny fold in the region, forming a eastwest or northeast trending overthrust fault. The board in the process of orogenic magmatism accompanied with granite emplacement.