著者

佐藤 友彦 磯崎 行雄 張 興亮

出版者

The Geological Society of Japan

雑誌

日本地質学会学術大会講演要旨 (ISSN:13483935)

巻号頁・発行日

pp.345, 2014 (Released:2015-03-16)

著者

石川 晃 金子 慶之 太田 努 磯崎 行雄

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.120, no.1, pp.52-64, 2011-02-25 (Released:2011-05-20)

参考文献数

59

被引用文献数

2 2 3

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The western Pacific region, where the Eurasia, Australia, and Pacific plates currently interact, has been recognized as an important site for constraining the origins and emplacement of ophiolites (particularly for island-arc or supra-subduction zone types), because the spatial distribution of oceanic micro-plates and numerous ophiolitic rocks along their convergent margins infers possible genetic linkages among them. Mafic-ultramafic rocks distributed in the Timor-Tanimbar island chain, eastern Indonesia may be a good example of the on-going emplacement of the marginal basin lithosphere on the continental margin in the arc-continent collision zone, and are recognized as a possible modern analogue for Mesozoic Tethyan-type ophiolites (e.g. Troodos and Oman) in the Alpine-Himalayan orogenic system. Geological occurrence suggests that the buoyant subduction of the Australian continent uplifted fragments of newly formed mantle-crust section, which extends to neighboring pre-emplaced forearc marginal basins. However, from petrological and geochemical points of view, young pillowed basalt, dolerite, and gabbroic cumulate commonly possess island-arc signatures, whereas structurally underlying peridotites are mostly fertile (lherzolitic) in composition. This suggests that the crustal section is not linked to the underlying mantle by a genetic melt-and-residua relationship, as inferred from the lack of complete succession and the presence of abundant crosscutting structures. This inconsistency leads to the emergence of two contrasting models accounting for the unusual occurrence of a fertile mantle in the forearc setting of the Timor-Tanimbar region: (1) thrust-stacked fragments of the subcontinental mantle originally exhumed in the rifting stage of Australia; (2) depth-related heterogeneities in the lithospheric part of the mantle wedge. We note that the current debates on the origins of fertile lherzolites found throughout the Tethyan sutures and western Pacific regions can be settled through a better understanding of Timor-Tanimbar peridotite masses by age-dating studies employing several radiogenic isotope systematics.

著者

磯崎 行雄 丸山 茂徳

出版者

学術雑誌目次速報データベース由来

雑誌

地學雜誌 (ISSN:0022135X)

巻号頁・発行日

vol.100, no.5, pp.697-761, 1991

被引用文献数

77 207

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The Japanese Islands consist fundamentally of late Paleozoic to Cenozoic accretionary complexes that formed in situ in a subduction zone along the East Asian continental margin, i.e. 2.0 Ga Yangtze craton (South China) and 450 Ma fore-arc ophiolite. Recent research utilizing microfossil and radiometric dating has distinguished several major accretionary complexes, including high-P/T metamorphosed parts, and subordinate ophiolites. In particular, recognition of oceanic plate stratigraphy and age of subduction-related metamorphism for individual accretionary complex allows the geotectonic subdivision of the Japanese Islands be emended with a new definition of geotectonic units and their mutual boundaries. Removing the effect of arcrelated magmatism and secondary tectonic modification by microplate activities such as backarc basin opening, fore-arc sliver movement, and arc-collision, a remarkable oceanward younging polarity is recognized among the accretionary complexes. This polarity in growth is well observed in Southwest Japan where seven distinct units occur, i.e. from the Japan Sea side to the Pacific side: 400-300 Ma high-P/T schists, Permian (250 Ma) accretionary complex, 230-180 Ma high-P/T schists, Jurassic (180-140 Ma) accretionary complex, 100 Ma high-P/T schists, Late Cretaceous (80 Ma) accretionary complex, and Tertiary (50-20 Ma) accretionary complex. The sinuous surface trajectories of these geotectonic boundaries and occurrence of several tectonic outliers and windows indicate that all these complexes, including high-P/T schists, occur as subhorizontal (or gently northward dipping) thin tectonic unit, i. e. nappe. Thus the Japanese Islands form a huge pile of nappes that become younger structurally downward to the modern Nankai accretionary complex. What is remarkable in this subhorizontal orogen is that high-P/T units are tectonically intercalated between low-P units, e. g. the thin nappe of 100 Ma Sanbagawa blueschists between Jurassic and Late Cretaceous accretionary complexes of the prehnite-pumpellyite facies. Uplift of the Sanbagawa high-P/T unit appears to correlate with the arrival of the Kula/Pacific spreading ridge at the trench, suggesting that this high-P/T accretionary complex may have been extruded and uplifted into low-P domain in fore-arc by buoyant subduction of the spreading ridge at the trench. Evidence of ridge subduction at that time is supported by reconstructed paleoplate motion and the coeval climax of arc-related Ry-oke magmatism associated with low-P/T regional metamorphism. Formation of older high-P/T blueschist nappes sandwiched between low-P units can be explained likewise. Subduction of major spreading ridges seems most critical for the episodic oceanward development not only of subhorizontal high-P/T nappes but also of continent side granitic belts.

著者

磯崎 行雄 丸山 茂徳 柳井 修一 下司 信夫 佐野 修 笠原 順三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.2, pp.187-189, 2010-04-25 (Released:2010-07-06)

参考文献数

15

著者

丸山 茂徳 磯崎 行雄 柳井 修一 下司 信夫 佐野 修 笠原 順三

出版者

公益社団法人 東京地学協会

雑誌

地学雑誌 (ISSN:0022135X)

巻号頁・発行日

vol.119, no.6, pp.959-962, 2010-12-25 (Released:2011-03-17)

参考文献数

28

著者

田近 英一 多田 隆治 橘 省吾 関根 康人 鈴木 捷彦 後藤 和久 永原 裕子 大河内 直彦 関根 康人 後藤 和久 大河内 直彦 鈴木 勝彦 浜野 洋三 永原 裕子 磯崎 行雄 村上 隆

出版者

東京大学

雑誌

基盤研究(B)

巻号頁・発行日

2006

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約25億~20億年前に生じた全球凍結イベントと酸素濃度上昇の関係を明らかにするため,カナダ,米国,フィンランドにおいて地質調査及び岩石試料採取を実施し,様々な化学分析を行った.その結果,同時代の地層対比の可能性が示された.またいずれの地域においても氷河性堆積物直上に炭素同位体比の負異常がみられることを発見した.このことから,氷河期直後にメタンハイドレートの大規模分解→温暖化→大陸風化→光合成細菌の爆発的繁殖→酸素濃度の上昇,という可能性が示唆される.

著者

磯崎 行雄

出版者

日本地質学会

雑誌

地質学論集 (ISSN:03858545)

巻号頁・発行日

no.50, pp.89-106, 1998-07-31

被引用文献数

12

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日本列島を含む東アジアの顕生代造山帯は, 海洋プレートの沈み込みによって先カンブリア時代の安定大陸の周囲に新しい大陸地殻が成長した場である。日本の起源は6〜7億年前に超大陸Rodiniaから揚子地塊がリフト化して離れた時の大陸縁に求められる。この受動的大陸縁は約5億年前に活動的大陸縁に転化した。新しい海洋プレート沈み込みは大陸縁に弧-海溝系を生じ, 4億年頃にそれが成熟すると, それ以後はほぼ水平な古生代-新生代付加体のナップ群やカルクアルカリ岩系火成岩をつくった。また間欠的な中央海嶺の海溝への沈み込みは, 低温高圧型変成帯の上昇や, 高温低圧型変成帯を伴う花崗岩バソリス帯の形成をもたらした。日本の造山帯は北米西岸のコルディレラ造山帯と鏡対称の構造をもち, それらの歴史は超海洋太平洋がたどったウィルソンサイクルの前半史にあたる。その後半史は2億年後に北米とアジアが衝突して次の超大陸Amasiaができる時に完結する。