The Redefinition Of The Silurian System And Its Significances In The Eastern E-Min,Western Junggar

Silurian is the important stages of the construction and development of ocean basin and island arc in the northern of West Junggar, during this period, there has experienced the process of mutal subduction in ocean basin and action in island arc zone, the Boshchekul-Chingiz magmatic arc was also started in this time from Eastern Kazakhstan to Northern Xinjiang. Scholars has the different understanding on Silurian formation since the study of basic geology is not enough in this area. The new founded Silurian formation and volcanic in East Emin was studied detailly on stratigraphic classification and contrasting, combing the predecessors’ research data, the early–middle Silurian Qiaergaye formation and middle Silurian Shaerbuer formation geologic feature, lithological association, sedimentary environment was be discussed, besides the lithology, lithofacies, petrogeochemistry, zircon LA-ICP-MS dating and structural setting of volcanic was studied, On this basis, we discussed the tectonic evolution of Silurian.The Qiaergaye formation consists of island-arc volcanic clastic rock in study area, comprehensive analysis shows the evidence of littoral and shallow marine facies, furthermore,the Qiaergaye formation can be divided into three segment, the lower segment is given priority to with middle and coarse clastic sediments, fine clastic sediments(contain the coral, wrist and other fossils) and lava rock taking up a small amount. The middle segment is characterized by volcanic clastic rock(tuffaceous), the upper segment is coarse clastic sediments. The Qiaergaye formation is close to the crater of the volcano, and affected by volcanic activity in the process of sediment.The Qiaergaye formation is given priority to with lava rock and volcanic clastic rock, the lava rock consists of grey purple and celadon pyroxene andesite. LA-ICP-MS zircon U-Pb dating of pyroxene andesite age is obtained 428.7±2.7Ma, belonging to Wenlock era, middle Silurian. The geochemical features of volcanic rocks shows are relatively enriched in Si、Sr、Ba、LILE, has the high value of Mg#、Sr/Y and Ba/La, rocks are loss of HFSE, Among them, Nb、Ta、Ti is obvious low, however the Eu negative abnormality is small. The rock geochemical features is similar to Miocene sanukitoid in Japenese Setouchi volcanic belt. Integrated all of the information on geology structure, sedimentary characteristics, and tectonic setting reveal that volcanic rock formed volcanic island arc environment.All above, the ocean development in late Early Paleozoic in the north part of West Junggar was recorded by Silurian in study area; the rock association, sedimentary environment paleotological features and volcanic in Silurian formation is of great significance on tectonic evolution and tectonic development in the north part of West Junggar from The late Early Paleozoic to early Late Paleozoic.