Geochemical Characteristics And Tectonic Environment Of The Dahalajunshan Formation In Tekesi Daban, Xinjiang

This dissertation is object on the volcanic rock of Lower carboniferous Dahalajunshan in Tekesi area in Xin Jiang. Researching the character of volcanic rock and its tectonic environment, including the field character, petrology, lithofacies, petrochemistry, geochemistry, isotoplc geochronology and so on.Firstly, according to its rock characteristic, the rock combination and space distribute, the volcanic rock of the Dahalajun mountain formation is divided into up-segment and down-segmen. However, the bottom of Dahalajunshan formation hadn't found, and the Yishijilike, Akeshake and Wulang formation overtake it. The contact relationship is definitude.Secondly, there are many Lower Carboniferous fossil have been found in its top geologic strata—the Akeshake formation. It can evident that the ago of the Dahalajun mountain formation is Lower Carboniferous. Moreover, the Rb—Sr isolopic dating of the Dahalajun mountain formation is 351±2Ma, belong to Lower Carboniferous.Thirdly, On the rock chemistry classification it mainly allots for the alkaline series of calcium, the volcano clastic rock is main, the alkaline volcano rock is a little amount, and in basic lava and intermediate lavas there are among them which are often the poor TiO₂(<1.2%), with less of the neutral volcano rock, and main of the acid volcano rock. Therefore, we can prove that the Dahalajunshan formation have the character of epicontinental-arc volcano rock. Moreover, the trace element and lanthanon character also indicate that the volcano rock of Dahalajunshan formation is generated from epicontinental-arc environment.In conclusion, with a integrated researching, we conclude that Yili plot is a high mature plot which reflect the tectonic environment of Dahalajun mountain. Precambrian ancient stratum and antiquity metamaorphic rock with the character of stability had been founded in this reseach. So, we can find that the Yili plot is a landmass and the tectonic environment of Dahalajunshan formation is epicontinental-arc environment.