Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia

Nugroho Imam Setiawan, Yasuhito Osanai, Nobuhiko Nakano, Tatsuro Adachi, Kazuhiro Yonemura, Aya Yoshimoto

研究成果: ジャーナルへの寄稿記事

5 引用 (Scopus)

抄録

This contribution reports the metamorphic evolution of the high-pressure metamorphic rocks from the Bantimala Complex, South Sulawesi, Indonesia. Barroisite-bearing and barroisite-free eclogites were examined to assess their metamorphic evolutions, which have implications regarding the tectonic conditions in this region. The eclogites mainly consist of garnet, omphacite, phengite, rutile, and epidote, with or without barroisite. The variations in mineral assemblages are interpreted to depend upon local changes in the bulk chemical composition. The barroisite-bearing eclogites contain two types of euhedral garnet: coarse- (1-1.5 mm) and fine- grained (<0.5 mm). Mineral inclusions in the coarse-grained garnet core and mantle show epidote + titanite and glaucophane + epidote assemblages, that stabilized at 0.9-1.5 GPa and 350-550 °C within epidote blueschist- facies conditions. Mineral chemistry and chemical-mapping analyses indicate that both fine-grained garnet and the rim of coarse-grained garnet formed at peak P-T conditions, which were estimated as 2.3-2.7 GPa at 615-680 °C based on the garnet-omphacite-phengite-quartz equilibrium. Peak P-T conditions for barroisite- free eclogite were similar (2.5-2.7 GPa at 650-690 °C) to those for barroisite-bearing eclogite. Actinolite rims overgrowing matrix sodic-calcic amphiboles attest to retrogression at P < 0.5 GPa and T < 350 °C in a clockwise P-T path. The very low geothermal gradient experienced during the prograde path (~ 5 °C/km) likely suggests the subduction of an old and cold oceanic crust. The low geothermal gradient on the retrograde path suggests decompressional cooling during exhumation, possibly favored by a serpentinite-dominated matrix within a subduction channel environment.

元の言語英語
ページ(範囲)211-225
ページ数15
ジャーナルJournal of Mineralogical and Petrological Sciences
111
発行部数3
DOI
出版物ステータス出版済み - 7 22 2016

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Indonesia
garnets
garnet
epidote
eclogite
omphacite
phengite
minerals
geothermal gradient
P-T conditions
rims
mineral
subduction
blueschist facies
glaucophane
gradients
metamorphic rocks
matrix
retrogression
amphiboles

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geology

これを引用

Prograde and retrograde evolution of eclogites from the Bantimala Complex in South Sulawesi, Indonesia. / Setiawan, Nugroho Imam; Osanai, Yasuhito; Nakano, Nobuhiko; Adachi, Tatsuro; Yonemura, Kazuhiro; Yoshimoto, Aya.

:: Journal of Mineralogical and Petrological Sciences, 巻 111, 番号 3, 22.07.2016, p. 211-225.

研究成果: ジャーナルへの寄稿記事

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abstract = "This contribution reports the metamorphic evolution of the high-pressure metamorphic rocks from the Bantimala Complex, South Sulawesi, Indonesia. Barroisite-bearing and barroisite-free eclogites were examined to assess their metamorphic evolutions, which have implications regarding the tectonic conditions in this region. The eclogites mainly consist of garnet, omphacite, phengite, rutile, and epidote, with or without barroisite. The variations in mineral assemblages are interpreted to depend upon local changes in the bulk chemical composition. The barroisite-bearing eclogites contain two types of euhedral garnet: coarse- (1-1.5 mm) and fine- grained (<0.5 mm). Mineral inclusions in the coarse-grained garnet core and mantle show epidote + titanite and glaucophane + epidote assemblages, that stabilized at 0.9-1.5 GPa and 350-550 °C within epidote blueschist- facies conditions. Mineral chemistry and chemical-mapping analyses indicate that both fine-grained garnet and the rim of coarse-grained garnet formed at peak P-T conditions, which were estimated as 2.3-2.7 GPa at 615-680 °C based on the garnet-omphacite-phengite-quartz equilibrium. Peak P-T conditions for barroisite- free eclogite were similar (2.5-2.7 GPa at 650-690 °C) to those for barroisite-bearing eclogite. Actinolite rims overgrowing matrix sodic-calcic amphiboles attest to retrogression at P < 0.5 GPa and T < 350 °C in a clockwise P-T path. The very low geothermal gradient experienced during the prograde path (~ 5 °C/km) likely suggests the subduction of an old and cold oceanic crust. The low geothermal gradient on the retrograde path suggests decompressional cooling during exhumation, possibly favored by a serpentinite-dominated matrix within a subduction channel environment.",
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AU - Setiawan, Nugroho Imam

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AU - Yonemura, Kazuhiro

AU - Yoshimoto, Aya

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