Geochemistry and isotope tracer study of UHP metamorphic rocks

After more than a decade of research, the concept of subduction of light continental rocks into the denser upper mantle has become a well-established fact. Primary evidence for this phenomenon is found in the similarity of lithologic successions of UHP metamorphic terranes with stratigraphic sequences observed in upper continental rocks. Interlayered quartzite, marble, mica schist, and paragneiss resemble sedimentary sequences of sandstone, limestone, shale and graywacke deposited along continental margins. Concordant layers of eclogite in quartzite, marble, schist, and biotite gneiss suggest basaltic sills or lava flows. More importantly, based on chemical and isotopic analyses, eclogites from many UHP...