P-T Conditions of Granulite-Facies Rocks From the Hidaka Metamorphic Belt, Hokkaido, Japan

康人, 小山内; 一則, 在田; 光隆, 番場

doi:10.5575/geosoc.92.793

Cited by 37 publications

(17 citation statements)

References 16 publications

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“…In the higher-grade metasedimentary schists and gneisses, found along the western part of the KoikakushueSatsunai River, the mineral assemblages are mainly muscovite and biotite; a temperature of 404e596 C was estimated by RSCM thermometry (Tables 1 and 2). Biotite recrystallized to form clotted textures along the schistosity when the temperatures were around 500 C. These estimated temperatures by RSCM thermometery are consistent with temperature estimates based on garnetebiotite geothermometers in other regions of the Hidaka metamorphic belt (Osanai et al, 1986(Osanai et al, , 1991(Osanai et al, , 2007. On the other hand, the graphite in the fault rocks shows lower degrees of graphitization than that in the host metamorphic rocks.…”

Section: Graphite In the Cataclasites Ultracataclasites And Pseudotsupporting

confidence: 77%

“…1b). The metamorphic grade of the Hidaka metamorphic rocks decreases progressively from granulite facies in the basal (western) part to very low-grade metasediments in the top (eastern) part of the belt (Osanai, 1985;Osanai et al, 1986Osanai et al, , 1991Osanai et al, , 2007Komatsu et al, 1989). The Hidaka metamorphic rocks are grouped into two sequences, lower and upper (Komatsu et al, 1983).…”

Section: Geological Settingmentioning

confidence: 99%

“…The Hidaka metamorphic rocks are grouped into two sequences, lower and upper (Komatsu et al, 1983). The lower sequence is composed of amphibolite to granulite facies mafic, pelitic, and psammitic rocks, and the upper sequence, in descending order, consists of very lowgrade (prehniteepumpellyite facies) metasediments, muscovite (Ms)echlorite (Chl) metasediments, biotite (Bt)eMs schists, BteMs gneisses, and banded Bt gneisses (Osanai et al, 1986(Osanai et al, , 1991Komatsu et al, 1989). The uppermost (easternmost) metasediments of the Hidaka metamorphic belt are lithologically continuous with sedimentary rocks of the Nakanogawa Group that overlie the upper sequence (e.g., Komatsu et al, 1989;Osanai and Owada, 1989), and the Nakanogawa Group is considered to be the protolith of the upper sequence (Komatsu et al, 1983).…”

Section: Geological Settingmentioning

confidence: 99%

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Strain-induced amorphization of graphite in fault zones of the Hidaka metamorphic belt, Hokkaido, Japan

Nakamura

Oohashi

Toyoshima

et al. 2015

Journal of Structural Geology

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Section: Graphite In the Cataclasites Ultracataclasites And Pseudotsupporting

confidence: 77%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

See 1 more Smart Citation

Strain-induced amorphization of graphite in fault zones of the Hidaka metamorphic belt, Hokkaido, Japan

Nakamura

Oohashi

Toyoshima

et al. 2015

Journal of Structural Geology

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“…1. Simplified geological map and pseudotachylyte distribution of the Hidaka metamorphic belt, compiled from Osanai et al (1986a), Owada (1989), Toyoshima (1990), Shimura (1992), Toyoshima et al (1994), Komatsu et al (1994), Obara (1997), and Niizato and Toyoshima (2000).…”

Section: Geology and Tectonics Of The Hidaka Metamorphic Beltmentioning

confidence: 99%

Pseudotachylytes, related fault rocks, asperities, and crustal structures in the Hidaka metamorphic belt, Hokkaido, northern Japan

et al. 2014

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Many pseudotachylytes and their related fault rocks are found in the Hidaka metamorphic belt representing an ancient crustal section. On the basis of field observations of the pseudotachylytes and related fault rocks, nature of seismogenic faulting in the Hidaka crust is examined. The field observations suggest the following conclusions.(1) Two structural types of pseudotachylytes are distinguished: layer-parallel and layer-oblique. The latter are scattered in the metamorphic belt, but the former occur only in the southern part of the metamorphic belt. (2) An abundance of the layer-parallel pseudotachylytes suggests that earthquakes occurred repeatedly and frequently in the southern part, where complicated and duplicated crustal structures occur with many lowtemperature thin mylonite zones. The southern part with such crustal structures was an ancient seismogenic area containing asperities and having a radius of a few tens of kilometers in the Hidaka crust. In the seismogenic area, the layer-parallel pseudotachylytes resulted from seismic slip on the mylonitic foliation within the lowtemperature mylonite zones with strong preferred orientation of micas. (3) The layer-parallel pseudotachylytes and the subsequent layer-oblique pseudotachylytes post-date the latest and very-low-temperature mylonitization in the metamorphic belt. The former pseudotachylytes formed just above the upper side of the brittle-plastic transition zone.

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“…The mineral assemblage of orthopyroxene + garnet + cordierite is common in zone E. Zone C' is a contact aureole around the igneous complex (Shiba, 1988). Metamor phic conditions were estimated by Osanai et al (1986) and Shiba (1988) to be 6-6.5 kb, 650 750°C in the higher grade part of zone D, and 6.5-7 kb, 750-800°C for zone E. These metamor evolution of pelitic rocks 323 BT.' phic conditions are sufficient for the pelitic gneisses to melt (e.g.…”

Section: Introductionmentioning

confidence: 99%

Anatexis and chemical evolution of pelitic rocks during metamorphism and migmatization in the Hidaka metamorphic belt, Hokkaido.

1989

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The southernmost Hidaka metamorphic belt consists mainly of cordierite tonalite intrusions and pelitic metamorphic rocks ranging from the greenschist to the granulite facies. Anatectic migmatites are common in the higher amphibolite and granulite facies zones. Compositional changes in major, rare earth elements and some other trace metals are so small that they are undetectable among the pelitic metamorphic rocks of zones A + B + C and D, but they are large enough to be detected in the higher am phibolite (zone D) to the granulite facies rocks (zone E). The enrichment of Fe, Mg, Na, Eu, and Sc, and the depletion of K, P, La, Ce, Nd, Cs and Rb are statistically significant in pelitic granulites, while heavy REEs are very variable. The chemical variation of pelitic granulite was derived from the accumulation of plagioclase +garnet. This suggests that more than 50-60% of the total volume of pelitic granulite was melted to produce a large amount of tonalitic magma, leaving pelitic granulite as a restite.Migmatites of the higher amphibolite facies are anatexites, and their K, P, Cs, Rb and light REE content is the same as that of lower grade metamorphic rocks. Migmatites of the higher amphibolite facies melted incipiently to segregate only a small amount of melt, and could not produce a large magmatic mass such as the cordierite tonalites.Cordierite tonalites are S-type granites, and their major elements, Cs, Rb and light REE concentra tions are similar to those of lower grade metamorphic rocks. The chemical variation of cordierite tonalites is explained by the extraction of plagioclase +garnet from a tonalitic magma and the variation of original sedimentary rocks. The small chemical difference between the cordierite tonalites and the lower grade metamorphic rocks suggests that the former was derived from a massive melting of meta pelites or that much of the restite is retained. The material migration among higher amphibolite facies rocks, pelitic granulites, migmatites and cordierite tonalites took place through mineral /melt interac tion in the lower crust.

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P-T Conditions of Granulite-Facies Rocks From the Hidaka Metamorphic Belt, Hokkaido, Japan

Cited by 37 publications

References 16 publications

Strain-induced amorphization of graphite in fault zones of the Hidaka metamorphic belt, Hokkaido, Japan

Strain-induced amorphization of graphite in fault zones of the Hidaka metamorphic belt, Hokkaido, Japan

Pseudotachylytes, related fault rocks, asperities, and crustal structures in the Hidaka metamorphic belt, Hokkaido, northern Japan

Anatexis and chemical evolution of pelitic rocks during metamorphism and migmatization in the Hidaka metamorphic belt, Hokkaido.

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