Permo–Triassic Barrovian-type metamorphism in the ultrahigh-temperature Kontum Massif, central Vietnam: Constraints on continental collision tectonics in Southeast Asia |
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Authors: | Nobuhiko Nakano Yasuhito Osanai Masaaki Owada Yasutaka Hayasaka Tran Ngoc Nam |
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Affiliation: | Division of Evolution of Earth Environments, Faculty of Social and Cultural Studies, Kyushu University, 4-2-1 Ropponmatsu, Chuo-ku, Fukuoka 810-8560 (email: ),;Division of Earth Sciences, Graduate School of Science and Technology, Yamaguchi University, Yamaguchi,;Department of Earth and Planetary Systems Science, Hiroshima University, Higashi Hiroshima, Japan, and;Department of Geosciences, Hue University, 77 Nguyen Hue Street, Hue, Vietnam |
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Abstract: | The Kontum Massif in central Vietnam is composed of various metamorphic complexes including a high-temperature southern part (Kannak and Ngoc Linh complexes) and a low- to medium-temperature northern part (Kham Duc complex). The Kham Duc complex exhibits Barrovian-type medium-pressure metamorphism evidenced by kyanite- and/or staurolite-bearing metapelites. The garnet–gedrite–kyanite gneiss, which is the focus of the present study, preserves several mineral parageneses formed during a prograde and retrograde metamorphic history: staurolite + quartz in gedrite, garnet + gedrite + kyanite in the matrix, and spinel + cordierite symplectite between gedrite and sillimanite. The calculated semiquantitative petrogenetic grid reveals peak pressure conditions of 620–650°C at 1.1–1.2 GPa and peak temperature conditions of 730–750°C at 0.7–0.8 GPa. The monazite U–Th–Pb electron microprobe ages of the garnet–gedrite–kyanite gneiss and associated gneisses yield 246 ± 3 Ma for the Kham Duc complex, which is similar to the age of the high- to ultrahigh-temperature metamorphism in the adjacent Kannak and Ngoc Linh complexes of the southern Kontum Massif. The present results indicate that both the Barrovian-type and ultrahigh-temperature metamorphism occurred simultaneously in the Kontum Massif during an event strongly related to Permo–Triassic microcontinental collision tectonics in Asia. |
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Keywords: | Barrovian-type metamorphism continental collision garnet–gedrite–kyanite gneiss Kham Duc complex Kontum Massif Permo–Triassic age Vietnam |
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