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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
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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.
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