Geological characteristics and its setting for volcanic rocks of early Cretaceous Yixian Formation in western Liaoning province, eastern China
辽西早白垩世义县组火山岩的地质特征及其构造背景

Volcanic rocks of early Cretaceous Yixian Formation were widely distributed in western Liaoning province. Based on the studies of petrology, element- isotopic geochemistry, volcanic rocks of Yixian Formation have the characteristics of continental intraplate and continent margin arc which were mainly high-K calc-alkaline series and enriched relatively in large ion lithophile elements (e. g. Rb, Sr, Ba etc. ) and relatively low radio-active elements (U, Th) and high field strength elements (e. g. Nb, Ta, Ti, Zr, Hf etc. ) and unconspicuous Eu-negative abnormity, lower radio-origin isotopes of Nd, Sr and Pb. The authors think the volcanic rocks of Yixian Formation in western Liaoning province derived from partial melting of enriched lithosphere mantle and suffered from the dominant evolution by crystal-liquild fractionation with the small degrees of lower crust assimilation(AFC-type processes). Combined to the prevenient study of regional structures and geochemisty of volcanic rocks, the volcanic rocks of Yixian Formation were generated in response to lithosphere inhomogeneous extension in the continental intraplate orogenic belt, which were not directly associated with the subduction of the Pacific plate beneath the Eurasian plate during the Mesozoic.