The high-dT/dP-type Hidaka Metamorphic Belt in Hokkaido, northern Japan, represents a tilted crustal section of a magmatic arc of Tertiary age. The highest metamorphic grades reached are granulite facies, and the syn-metamorphic granitic rocks are widely distributed in this metamorphic terrane. The granitic rocks are mainly tonalitic and granodioritic in composition, and are classified into peraluminous (S-type) and metaluminous (I-type) granitoids. A large amount of pyroxene-bearing S-type tonalites (garnet-orthopyroxene tonalite) is distributed in the Niikappu river region in the northern part of the Hidaka Metamorphic Belt. Pyroxene-bearing I-type tonalite (two-pyroxene hornblende tonalite) bodies are also distributed in this area.The pyroxene-bearing tonalites are classified into several sub-types on the basis of their field occurrence, texture, mineral assemblage and geochemical features. Homogeneous IH- and SH-type tonalite are thought to represent original magmas, i.e. those which have been generated by partial melting of mafic metamorphic rocks and pelitic-psammitic metamorphic rocks, respectively. Model calculations assuming batch partial melting indicate that possible restites are garnet-two-pyroxene mafic granulite for IH-type and garnet-orthopyroxene aluminous granulite for SH-type. The unexposed lowermost crust of the ‘Hidaka crust’ is thought to be composed of garnet-two-pyroxene mafic granulite, garnet-orthopyroxene aluminous granulite and metagabbros.
Garnet bearing granite (Grt granite) and high grade pelitic gneisses occur in the Kannak Complex, southern Kontum Massif, central Vietnam. Electron microprobe (EMP) dating of monazite in Grt granite and garnet orthopyroxene gneiss (Grt Opx gneiss) gave ages of ca. 260 Ma from cores and ca. 230 Ma from thin rims. Since most monazite grains are predominately of core composition, the ca. 260 Ma age indicates the timing of high temperature metamorphism and the formation of Grt granite. Grt granite is locally accompanied by coeval intrusions of fine grained gabbro, which is a candidate for the heat source leading to high grade metamorphism and partial melting of the crust during the Late Permian.
The Vengen Granite, one of early Paleozoic granitic rocks crops out of the southern end of the Vengen ridge, the Kanino-tsume Peak at the Main Shear Zone (MSZ) of the Sør Rondane Mountains, East Antarctica. This granite is composed of medium-to fine-grained mylonitic biotite granite and cuts the MSZ and Kanino-tsume Shear Zone. The fine-grained A c c e p t e d i n J M P S P r e -p r o o f
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