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Variety and genesis of the pyroxene-bearing S- and I-type granitoids from the Hidaka Metamorphic Belt, Hokkaido, northern Japan

By
Toshiaki Shimura
Toshiaki Shimura
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Masaaki Owada
Masaaki Owada
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Yasuhito Osanai
Yasuhito Osanai
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Masayuki Komatsu
Masayuki Komatsu
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Hiroo Kagami
Hiroo Kagami
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Published:
January 01, 2004

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.

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GSA Special Papers

The Fifth Hutton Symposium on the Origin of Granites and Related Rocks

S. Ishihara
S. Ishihara
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W.E. Stephens
W.E. Stephens
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S.L. Harley
S.L. Harley
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M. Arima
M. Arima
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T. Nakajima
T. Nakajima
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Geological Society of America
Volume
389
ISBN print:
9780813723891
Publication date:
January 01, 2004

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