Growth conditions of andradite in Triassic sandstone from Kurobayama, Onoda City, Yamaguchi Prefecture.

Shibuya, Gorô; Komatsu, Hiroshi

doi:10.2465/gkk1952.17.217

Cited by 3 publications

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“…(); 11, M iyamoto and K uwazuru (); 12, M iyamoto and K uwazuru (); 13, M usashino and K asahara (); 14, N akamoto et al . (); 15, O bayashi (); 16, S hibuya and K omatsu (); 17, S uzuki (); 18, T akeuchi (); 19, T akeuchi (); 20, T akeuchi (); 21, T akeuchi (); 22, T anaka and A dachi (); 23, T eraoka et al . (); 24, T eraoka et al .…”

Section: Introductionmentioning

confidence: 99%

Detrital anisotropic grandite garnet as an indicator of denudation level of Permian volcanic arc in the provenance of the South Kitakami Belt, Northeast Japan

Takeuchi

2013

Island Arc

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In this study, the chemical and optical features of detrital garnets from the Middle Permian to Upper Triassic sandstones in the South Kitakami Belt, Northeast Japan, were examined to reveal the tectonic movement in the provenance. The sandstones contain a large amount of detrital grandite garnet grains with a wide range of andradite content. Among them, some grandite garnet grains show optically anisotropic features and rarely oscillatory zoning and sector twinning. The proportion of the detrital anisotropic grandite garnet increases from the Permian to the Middle Triassic and decreases in the Late Triassic. Such grandite garnets with various andradite contents occur in skarn deposits. Isotropic grandite garnets in the early stage of skarn evolution are distributed widely around a pluton, which affects the thermal metamorphism of the surrounding strata. However, anisotropic grandite garnets are formed along veinlets and fractures in the middle to late hydrothermal stage as the pluton cools, and their distribution is limited to a narrower area near the pluton compared to the metamorphic aureoles formed in the early stage. Changes in the chemical and optical features of the detrital garnets indicate a progressive denudation of the plutonic body accompanying skarn deposits in the provenance. The proportion of detrital anisotropic grandite garnet grains among all of the detrital grandite garnet is considered to be a sensitive indicator of the denudation level in a deeper part of the volcanic arc in association with skarn deposits, together with traditional sandstone composition datasets. This newly proposed method should be useful for clarifying the paleogeography during the Permian to Triassic in the East Asian continental margin, associated with uplift and denudation of the Permian volcanic arc, which seems to have been induced by the collision of the North China and South China Blocks.

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Section: Introductionmentioning

confidence: 99%

Detrital anisotropic grandite garnet as an indicator of denudation level of Permian volcanic arc in the provenance of the South Kitakami Belt, Northeast Japan

Takeuchi

2013

Island Arc

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Changes in garnet chemistry show a progressive denudation of the source areas for Permian-Jurassic sandstones, Southern Kitakami Terrane, Japan

Takeuchi

1994

Sedimentary Geology

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Detrital garnets from Paleozoic to Tertiary sandstones in Southwest Japan.

Teraoka¹

2003

Bull. Geol. Surv. Japan

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Garnets are classified into low P/T type, intermediate P/T type (Ia, Ig1, Ig2), high P/T type, eclogite type and grandite. They are characteristic of low-pressure metamorphic and granitic rocks, intermediate-pressure metamorphic rocks (Ia : up to amphibolite facies, Ig1 and Ig2 : granulite facies), high-pressure metamorphic rocks, eclogites and calcareous metamorphic rocks, respectively. Ig1 and Ig2 garnets are rich in Mg, and the latter has not been reported from metamorphic rocks in the Japanese Islands, but from those of Archean age in the Asian continent. Garnets exclusive of grandite are collectively called pyralspite.Detrital garnet analysis was carried out on the basis of the above-mentioned classification of garnets on Devonian to mid Tertiary sandstones in Southwest Japan. The results indicate that assemlage of detrital garnets changed markedly in the following stages : 1) post-Devonian pre-Permian, 2) latest Middle to mid Late Triassic, 3) mid Cretaceous and 4) Cretaceous / Paleogene boundary. In the time from Permian to stage 2, grandites were predominant in some places and pyralspites in others, whereas after that pyralspites prevailed everywhere with a few exceptions. Enterring to the Late Cretaceous, low P/T type garnets began to increase in the Median Zone of Southwest Japan and the Chichibu Terrane as the result of exhumation of the Ryoke Metamorphic and Granitic Rocks in contrast of its decreasing in the Shimanto Terrane, where Ig2 garnets increased twofold or more at the begining of the Paleogene.The most common detrital garnets are intermediate P/T type (Ia, Ig1, Ig2), followed by low P/T type, grandite, high P/T type and eclogite type in order of abundance on the whole in Southwest Japan. The former three are considered to have been supplied mainly from Precambrian to Paleozoic metamorphic and granitic rocks in the Asian continent with minor derivations from the Japanese Islands. On the other hand, main source of high P/T type detrital garnets must have been the Sangun Metamorphic Rocks.

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Growth conditions of andradite in Triassic sandstone from Kurobayama, Onoda City, Yamaguchi Prefecture.

Cited by 3 publications

References 0 publications

Detrital anisotropic grandite garnet as an indicator of denudation level of Permian volcanic arc in the provenance of the South Kitakami Belt, Northeast Japan

Detrital anisotropic grandite garnet as an indicator of denudation level of Permian volcanic arc in the provenance of the South Kitakami Belt, Northeast Japan

Changes in garnet chemistry show a progressive denudation of the source areas for Permian-Jurassic sandstones, Southern Kitakami Terrane, Japan

Detrital garnets from Paleozoic to Tertiary sandstones in Southwest Japan.

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