Structural Evidence for the in‐situ Origin of the HP and UHP Eclogites in the Dabie‐Sulu Orogenic Belt

Abstract  Whether the HP and UHP metamorphic rocks of the Dabie‐Sulu orogenic belt are of an “in‐situ” or “foreign” origin is a long‐standing dispute among geologists. Eclogites preserved today in the HP and UHP units constitute merely 5–10%, which are not isolated exotic bodies tectonically intruding into amphibolite facies gneiss, but remnants of once pervasive or widespread eclogite‐facies terranes or slabs. The present spatial distribution and forms of the eclogites have resulted from polyphase and progressive deformation and strain partitioning of the HP and UHP slabs. From their formation in deep mantle to their exhumation to the surface, the eclogites have experienced long‐term deformation with different strain regimes. The dominant regime responsible for the present spatial distribution and forms of the eclogites is the shear process. The deformation patterns of the eclogites and gneiss matrix also clearly show that the eclogites were metamorphosed in situ. The original distribution area of the eclogites is much larger than that seen today.