The author picks up the study topics of metamorphic rocks in consideration of the paradigm of plume tectonics. First of all, He refers to minerals which are considered to have derived from the transitional zone and the lower mantle, i.e., inclusions in diamond in kimberlite. A problem of transitional zone origin of the Alpe Arami peridotite is introduced. Subsequently, ultra high pressure (UHP) metamorphic rocks exhumed by continent-continent collision are also briefly introduced. In addition, he reviews a discussion on diamond of possible UHP origin in the New England Fold Belt (NEFB), Australia.
The author emphasizes that tectonics of regional metamorphic belts in global scale relates closely to the formation and subsequent fragmentation of a Late Proterozoic supercontinent, Rodinia, and amalgamation forming new continents. Chronological study, especially by SHRIMP, is effective to estimate linkage among fragmented continental blocks, and an example in northern Japan is referred.
Introduced is the structural studies on the metamorphic belts along the plate collision zones which reveal non-rigidness of the lithosphere. Active deformation in the mountains is explained by not only extrinsic force along the plate boundary but also intrinsic force (gravitational potential energy) acting on the continental lithosphere. Study on deformation of metamorphic rocks composing the lower crust is important to test the effect of the intrinsic force and to reveal the influences of regional surface subsidence behind the subduction zone and mountain building along the collision zones. Modelling by experimental work and computer simulation increase the weights in studies of tectonics of metamorphic belts.