Paleozoic subduction-accretion-closure histories in the west Mongolian segment of the Paleo-Asian ocean: Evidence from pressure-temperature-time-Protolith evolution of high-Mg and -Al gneisses in the Altai Mountains

Nobuhiko Nakano, Yasuhito Osanai, M. Satish-Kumar, Tatsuro Adachi, Masaaki Owada, Sereenen Jargalan, Chimedtseie Boldbaatar, Aya Yoshimoto, Kundyz Syeryekhan

研究成果: ジャーナルへの寄稿記事

6 引用 (Scopus)

抄録

High-Mg, high-Al metasedimentary gneisses from the Altai Mountains, Mongolia, belonging to a subduction-accretion complex within the Central Asian Orogenic Belt can be divided into five rock types on the basis of mineral assemblages. Most rock types have high MgO and Al2O3 content and low CaO, Na2O, Rb, and Sr content. All rock types experienced a similar medium-pressure metamorphism characterized by a "hairpin"-shaped counterclockwise pressure-temperature path. U-Pb zircon and U-Th-Pb monazite ages indicated metamorphism at ca. 356 Ma and 277 Ma and inherited ages of 510-379 Ma, suggesting possible provenance to granitoids comparable to those in the Altai Mountains, China. The zircons that newly nucleated at ca. 356 Ma are characterized by high concentrations of light rare earth elements without a Ce anomaly-features common in zircons from hydrothermally altered rocks and a reducing environment. Petrological and geochronological results in this study suggest the following tectonic evolution: (1) continuous sub-duction and accretion of paleo-Asian oceanic crust during the Early Paleozoic, resulting in periodic granitoid mag-matism in the period 510-380 Ma and a continuous supply of granite-derived sediments providing detrital zircon and monazite grains to the accretionary prism; (2) ridge subduction during the Late Devonian-Early Carboniferous (ca. 356 Ma), resulting in hydrothermal metamorphism of the accretionary prism and interaction with seawater that produced rocks with unusual whole-rock chemistry; and (3) closure of the ocean leading to continental collision in the Early Permian (ca. 277 Ma), with part of the accretionary prism squeezed into lower crustal levels to form medium-pressure metamorphic rocks.

元の言語英語
ページ(範囲)283-308
ページ数26
ジャーナルJournal of Geology
122
発行部数3
DOI
出版物ステータス出版済み - 1 1 2014

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protolith
subduction
Paleozoic
accretion
mountain
accretionary prism
zircon
ocean
history
rock
metamorphism
temperature
monazite
continental collision
granitoid
orogenic belt
tectonic evolution
oceanic crust
metamorphic rock
provenance

All Science Journal Classification (ASJC) codes

  • Geology

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Paleozoic subduction-accretion-closure histories in the west Mongolian segment of the Paleo-Asian ocean : Evidence from pressure-temperature-time-Protolith evolution of high-Mg and -Al gneisses in the Altai Mountains. / Nakano, Nobuhiko; Osanai, Yasuhito; Satish-Kumar, M.; Adachi, Tatsuro; Owada, Masaaki; Jargalan, Sereenen; Boldbaatar, Chimedtseie; Yoshimoto, Aya; Syeryekhan, Kundyz.

:: Journal of Geology, 巻 122, 番号 3, 01.01.2014, p. 283-308.

研究成果: ジャーナルへの寄稿記事

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abstract = "High-Mg, high-Al metasedimentary gneisses from the Altai Mountains, Mongolia, belonging to a subduction-accretion complex within the Central Asian Orogenic Belt can be divided into five rock types on the basis of mineral assemblages. Most rock types have high MgO and Al2O3 content and low CaO, Na2O, Rb, and Sr content. All rock types experienced a similar medium-pressure metamorphism characterized by a {"}hairpin{"}-shaped counterclockwise pressure-temperature path. U-Pb zircon and U-Th-Pb monazite ages indicated metamorphism at ca. 356 Ma and 277 Ma and inherited ages of 510-379 Ma, suggesting possible provenance to granitoids comparable to those in the Altai Mountains, China. The zircons that newly nucleated at ca. 356 Ma are characterized by high concentrations of light rare earth elements without a Ce anomaly-features common in zircons from hydrothermally altered rocks and a reducing environment. Petrological and geochronological results in this study suggest the following tectonic evolution: (1) continuous sub-duction and accretion of paleo-Asian oceanic crust during the Early Paleozoic, resulting in periodic granitoid mag-matism in the period 510-380 Ma and a continuous supply of granite-derived sediments providing detrital zircon and monazite grains to the accretionary prism; (2) ridge subduction during the Late Devonian-Early Carboniferous (ca. 356 Ma), resulting in hydrothermal metamorphism of the accretionary prism and interaction with seawater that produced rocks with unusual whole-rock chemistry; and (3) closure of the ocean leading to continental collision in the Early Permian (ca. 277 Ma), with part of the accretionary prism squeezed into lower crustal levels to form medium-pressure metamorphic rocks.",
author = "Nobuhiko Nakano and Yasuhito Osanai and M. Satish-Kumar and Tatsuro Adachi and Masaaki Owada and Sereenen Jargalan and Chimedtseie Boldbaatar and Aya Yoshimoto and Kundyz Syeryekhan",
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AU - Nakano, Nobuhiko

AU - Osanai, Yasuhito

AU - Satish-Kumar, M.

AU - Adachi, Tatsuro

AU - Owada, Masaaki

AU - Jargalan, Sereenen

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AU - Yoshimoto, Aya

AU - Syeryekhan, Kundyz

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