The Tectono-Magmatic Evolution Of The Volcanic Rocks From Yamansu Formation In Easten Tianshan, NW China

Tectono-magmatic evolution and framework of the Yamansu Formation in the East Tianshan Mountain has long been controversial, which highly constraints our understanding of regional tectonic environment and associated magma process. Various Carboniferous volcanic-sedimentary formations widely exposed in Qoltagh tectonic belt, East Tianshan of China. Yamansu Formation is composed of basite-mesite-acidic volcanic rocks, pyroclastic rocks and pyroclastic sedimentary rocks. Geochemical analyses shows that the volcanics from Yamansu Formation are mainly calk-alkaline and relatively rich in Al, poor in Ti. Rock association of volcanics composed a complete evolvement sequences from intermediate-acid to acid. It is proved that the volcanics are formed in an island-arc setting, grew and matured gradually vertically from bottom to top the, by evidence of geochemical characteristics. The formation of volcanics was related to the southward subduction of ancient Asian Oceanic crust under the Central Tianshan Block.