Volcanic lavas of the Yixian Formation in western Liaoning province, China. Products of lower crust delamination or magma mixing?
辽西义县组火山岩:拆沉作用还是岩浆混合作用的产物?

The authors,based on the systematics of all the published major,trace elemental and isotopic data of volcanic lavas from the Yixian Formation,western Liaoning Province,found that the volcanic lavas of the Yixian Formation are composed dominantly of mafic-intermediate components with the increasing intermediate-acidic components in the upper sequence.Their high Mg~# values and adakitic geochemical characteristics are not the primary features of the initial magma,and thus cannot be regarded as the powerful evidence for the existence of lower crust delamination in the region.The mafic components of the Yixian Formation were originally derived from the lithospheric mantle,which were previously modified by the subducted oceanic crust.The mixing of mafic magma with ancient lower crust-derived magma to a certain degree produced the various volcanic lavas of the Yixian Formation.Therefore,volcanic lavas of the Yixian Formation are the products of magma mixing rather than lower crust delamination.Basaltic underplated lower crust was involved in the origin of these volcanic lavas,with little and limited contribution of the asthenosphere.