Metamorphic belts and complexes of the northwestern Pacific region may be subdivided into 6 types corresponding to certain types of metamorphism.

1. Early Precambrian granulitic and high-temperature migmatite gneissic massifs (Omolon, Okhotsk, Khankaiy, partly Chukotsk massifs).

2. Precambrian(?) kyanite-staurolite schist-gneissic complexes (massifs) such as Hida, Abukuma massifs, partly Chukotsk and central Kamchatka's massifs reworked by later orogeny.

3. Zonal belts of andalusite-sillimanite type, associated with granitoids and blocks of types 1 and 2: (a) Paleozoic (Pylgyn, Su-chan); (b) Mesozoic (Taygon, central Kamchatka, Kitakami-Abukuma, Kyoke belts, etc.).

4. Glaucophane-schistic belts, most specific, closely associated with ophiolitic belts, commonly treated as ancient boundary zones of oceanic platform. (a) Paleozoic (Pen-yin, San-gun, Matsugadaira-Motai, etc.) (b) Early Paleozoic (Pekulney-Vayega, Ganal, Susunai, Kamuikotan, Sanbagawa, etc.).

5. Green schistic uniformly metamorphosed rock series (such as pre-Amur Riphean rock series type).

6. Poorly metamorphosed rock series (prehnite-pumpellyitic and lomontitic facies) of different age. Treated as external zones or second-stage metamorphism of types 3-5; also as independent transient-to-low temperature metasomatosis.

Comparisons of the peculiarities found in these types, their tectonic positions and age succession, in addition to their relation with granitoids implies the validity of 2 concepts suggested by Miyashiro about paired belts and that of de Roever-Marakushev about successive age changes in the different types of metamorphism supplementing each other. This may be reflected as an idealized scheme, distinguishing zones of subsidence from zones of uplift.

End_of_Article - Last_Page 2477------------