Types and Time of Late Carboniferous Liukeshu Formation Volcanic Edifices in Eastern Junggar, Xinjiang

The study area is located south of Kalamaili great fault, east Junggar. Geotectonic environment activities were very strong in Kasimovian-Gzhelian, while volcanoes interacted by marine and continental facies erupted frequently, especially in Liukeshu formation. Three craters which combined as beaded were recognized in Yiziende'ader area. X-shaped profile of the best preserved No.1 crater was measured; combined with spot5 images and rock chemical characteristics, the activities of the polycyclic volcano are mostly central eruption, with both multi-center fissure eruption; the eruption manner are mainly effusive. The profile is a typical rock mushroom structure; the surrounding rocks centered to the funnel-shaped middle from outside to inside with the dip angle gradually slowing down. The center is felsitic volcanic porphyry neck; inner ring is a large number of andesitic tuff breccia, rhyolitic tuff breccia, andesitic ignimbrite, andesitic volcanic tuff dust and volcanic breccia filling; for the outer ring, brecciated tuff, volcanic breccia, brecciated andesite unconformably overlies the late Carboniferous Shiqiantan formation. Zircon SHRIMP U-Pb dating of volcanic bodies basalts shows a weighted average age of 305±21 Ma. Shallow marine animal fossils in Moscovian are rich in Shiqiantan formation of the underlying layer, while continental plant fossils in Gzhelian are rich in Kongqueping formation of the upper layer. In view of the above, the age of the volcanic eruption mechanism is limited to Kasimov of late Carboniferous.