Geological Characteristics And Tectonic Environment Analysis Of The Tanjianshan Group In The Buhete Mountain In The Northern Margin Of The Qaidam Basin

This paper takes Tanjianshan group of Buhete mountain Wulan County Qinghaiprovince as the research object, filling the predecessor to the Tanjianshan group of Buhetemountain area research from the formation of the distribution, deformation characteristics,petrology,and discusses on the Buhete mountain area geological evolution of the Paleozoicera Combining with geochemical characteristics and regional tectonic evolutioncharacteristics, characteristics of the rock. Starting from the geochemical aspects，We studyon Tanjianshan group of Buhete mountain and volcano rock comprehensively，and coming aconclusion that it formed in an island arc environment.Through field geological route and profile measurement, We identify the Tanjianshangroup of this area can be divided into three subgroups, underlying the Qiujidonggouformation for fault contact, and the overlying late Devonian Maoniushan formation as angularunconformity or fault contact; The Tanjianshan group metamorphic is low greenschist faciesmetamorphic belt, designated as the biotite zone.The Tanjianshan group in the late Devonianago, experienced at least two deformation: The first period of ductile deformation, the mainstructural features including small the tight fold symmetric，the formation of large compoundsyncline; The second is a brittle deformation, appear in different forms in different lithology,in phyllite and deterioration of performance basic volcano rocks as dense kink band, in themetamorphic carbonate rocks joints. Its formation age is the subject of the Ordovician, mayalso extend to the Cambrian, can compare better with Tanjianshan group of Xitieshan.Tanjianshan group of Buhete mountain volcano rock assemblage with andesite，belongto the sub alkaline series in calc alkaline series. The content of SiO2is between49.61-66.69%, showing the characteristics of low Ti, P, and Litman index is between1.03-1.95. It is LREE enrichment type, with obvious negative europium anomalies andenriching of large ion dear stone elements Cs, Rb etc., Ba, lossing of high field strengthelements Nb, Ta, Y etc..Through the geochemical evidence, combining with regional geological evolution, theTanjianshan group volcanic rocks formed in island arc tectonic environment environment.