The Geochronology And Geochemistry Of Middle-Late Permian Granitoids In The Middle Segment Of The North Margin Of The North China Craton

The center Inner Mongolia is located in the middle segment of the northern margin of the North China Craton(NMNCC) and the southern margin of the Central Asian Orogenic Belt(CAOB). The CAOB, which separates the Siberian craton from the Tarim and North China Cratons, is one of the most important site of Phanerozoic continental growth in the word. Influenced by the CAOB, the NMNCC underwent intensive magmatic and tectonic activity from late Paleozoic to early Mesozoic, forming a series of E-W trending magmatic zones. Although much progress has been made in documenting the feature of the continental margin, much uncertainty still persists regarding the tectonics history of the NMNCC. Here, we present SHRIMP and LA-ICP-MS zircon U-Pb ages, in situ zircon Lu-Hf isotopic data, and whole-rock Sr-Nd isotopic and geochemical data for a variety of granitoids from seven plutons in Bainaimiao-Shangdu- Xianghuangqi region.(1) The rocks of the study area, including biotite granite, alkali feldspar granite and granodiorite associated with multiple veins and minerals microcrystalline enclaves, are composed of quartz + feldspar + plagioclase + biotite +(amphibole) +(muscovite) + magnetite. The magmatic age of the biotite granite, alkali feldspar granite and granodiorite respectively is 260 Ma ~ 269 Ma, 263.5 ~ 270.7Ma and 270 Ma. The neighborhood areas also develop a series of granitoids, There was severe magmatic activity in the northern margin of North China in Late Permian magmatic activity.(2) The granitoids of the study area is characteristic of high silicon, high potassium, high-sodium, high-alumina abundance, exhibiting high-K calc alkaline or shoshonite characteristic. The granitoids fall in metaluminous to weakly peraluminous characteristic field, classified of A- and I-type granites. The wide ranges of εNd(t) and εHf(t) and old model ages of Nd and Hf isotope of the granitoids suggest the presence of crust-mantle interaction and partial melting of the lower continental crust.(3) Basaltic magma intrude into the crust along the flauts after collision gravitational collapse that in the northern margin of North China Craton in Permian, providing heat to evolve partial melting of metamorphic greywackes, khondalites and felsic granites, that formed felsic magma interacted with basaltic magma. Subsequently magma crystallized in the middle crust through a series of evolution.