Fertile upper mantle peridotite xenoliths indicate no wholesale destruction of cratonic root in East Asia

Abstract

A major question in geodynamic evolution of the Earth is whether the continental keel evolved geochemically or were delaminated and replaced by a new mantle. Here we present direct evidence for the geochemical evolution of continental keel from lherzolite xenoliths preserved in the Cenozoic alkali basalts from Jeju Island, Korea. Our findings, using detailed petrography and geochemical methods, reveal distinct textures and compositional changes (represented by olivine with magnesium number 91–87, 86–61 respectively) of two stages of geochemical alteration. The first stage involved a parental kimberlite melt that penetrated during the Paleozoic, and the second was caused by alkali basalt during Cenozoic. Our findings suggest that the Archean depleted harzburgitic upper mantle partially evolved to lherzolitic through interaction with melts/fluids that originated from the deep mantle, implying no wholesale delamination of the upper mantle root of East Asian continents.