Reconstruction of protoliths of metamorphic rocks of the Xingzi Group and discrimination of their tectonic setting

Abstract：The study of nature of the protoliths of metamorphic rocks in the Xingzi Group and their tectonic setting shows that the protoliths of mica schist, quartz schist and granulitite (leptite) in metamorphic rocks of the Xingzi Group are sedimentary rocks. Among other things, the protolith of mica schist is claystone, those of quartz schist and granulitite are graywacke or subgraywacke and those of amphibolite, hornblende schist and garnet amphibolite are basic volcanic rocks. Discrimination of the tectonic setting of metasedimentary rocks indicates that the Xingzi Group formed on active continental margins. Metabasic volcanic rocks are a transitional type between island-arc tholeiite and mid-oceanic tholeiite. They were formed in extensional basins.