25 years of continental deep subduction

This year marks the 25th anniversary of the discovery of coesite in metamorphic rocks of supracrustal origin. This initiated a revolution of the plate tectonics theory due to intensive studies of ultrahigh pres-sure metamorphism and continental deep subduction. The occurrence of coesite was first reported in 1984 by two French sci-entists, C. Chopin and D.C. Smith, re-spectively. Later on, occurrences of dia-mond in metamorphic rocks were reported by Russian scientists N.V. Sobolev and V.S. Shatsky in 1990 as well as by Chi-nese scientists S.T. Xu and his colleagues in 1992. These discoveries have resulted in the realization that some segments of the continental crust were subducted to mantle depths in excess of 100 km and returned to the surface during continental collision orogeny. This challenges the paradigm of plate tectonics in that the continental crust is not able to be subducted to mantle depths because of its lower density than the oceanic crust. Now our understanding of continental subduction/collision processes has been restructured after the 25 years of study on regional metamorphic rocks containing coesite and diamond. Our view of plate tectonics has being developed on the way from oceanic subduction to continental collision.......