The age determination of Late Paleozoic volcanic rocks in Shuanghetun area, Mulan County, Heilongjiang Province and its constraints on tectonic environment

A set of acidic volcanic rocks are exposed in Shuanghetun area, Mulan County, Heilongjiang Province.According to the lithologic association, they were divided into Early Permian Wudaoling Formation.In this work, the zircon U-Pb age of the rhyolite is 303±4 Ma.Based on the lithostratigraphic characteristics and zircon U-Pb dating data, they are redefined as Tangjiatun Formation and formed in Late Carboniferous.The quasi aluminous-peraluminous high-K calc alkaline volcanic rocks have geochemical characteristics of A-type granite.The obvious differentiation of LREE and HREE, with strong negative Eu anomaly, enrichment of large ion lithophile elements Rb, K, U, etc., and depletion of high field strength elements Nb, P, Ti, etc., indicate that the magma originated from partial melting of the lower crust, which may be the product of post collisional orogenic extension mechanism.Combined with the regional geological tectonic setting, it may have formed in the collision between Erguna -Xing'an block and Songnen -Zhangguangcailing block.The post orogenic extensional environment indicates that the study area changed from collisional orogeny to post orogenic extension in the Late Carboniferous.