Slab‐fluid metasomatism in the Early Paleozoic forearc mantle deduced from the Motai serpentinites, South Kitakami Belt, northeast Japan

The present study examines the petrology and geochemistry of the Early Paleozoic Motai serpentinites, the South Kitakami Belt, northeast Japan, to reveal the subduction processes and tectonics in the convergent margin of the Early Paleozoic proto‐East Asian continent. Protoliths of the serpentinites are estimated to be harzburgite to dunite based on the observed amounts of bastite (orthopyroxene pseudomorph). Relic chromian spinel Cr# [=Cr/(Cr + Al)] increases with decreasing amount of bastite. The compositional range of chromian spinel is similar to that found in the Mariana forearc serpentinites. This fact suggests that the protoliths of the serpentinites are depleted mantle peridotites developed beneath the forearc regions of a subduction zone. The Motai serpentinites are divided into two types, namely, Types 1 and 2 serpentinites; the former are characterized by fine‐grained antigorite and lack of olivine, and the latter have coarse‐grained antigorite and inclusion‐rich olivine. Ca‐amphibole occurs as isolated crystals or vein‐like aggregates in the Type 1 serpentinites and as needle‐shaped minerals in the Type 2 serpentinites. Ca‐amphibole of the Type 1 serpentinites is more enriched in LILEs and LREEs, suggesting the influence of hydrous fluids derived from slabs. By contrast, the mineral assemblage, mineral chemistry, and field distribution of the Type 2 serpentinites reflect the thermal effect of contact metamorphism by Cretaceous granite. The Ca‐amphibole of the Type 1 serpentinites is different from that of the Hayachine–Miyamori Ophiolite in terms of origin; the latter was formed by the infiltration of melts produced in an Early Paleozoic arc–backarc system. Chemical characteristics of the Ca‐amphibole in the ultramafic rocks in the South Kitakami Belt reflect the tectonics of an Early Paleozoic mantle wedge, and the formation of the Motai metamorphic rocks in the forearc region of the Hayachine–Miyamori subduction zone system, which occurred at the Early Paleozoic proto‐East Asian continental margin.

[1]  K. Michibayashi,et al.  Temporal and spatial mineralogical changes in clasts from Mariana serpentinite mud volcanoes: Cooling of the hot forearc-mantle at subduction initiation , 2021 .

[2]  K. Yi,et al.  Reappraisal of the oldest high-pressure type schist in Japan: New zircon U-Pb age of the Kitomyo Schist of the Kurosegawa Belt , 2021 .

[3]  T. Iizuka,et al.  Thermal state of the upper mantle and the origin of the Cambrian-Ordovician ophiolite pulse: Constraints from ultramafic dikes of the Hayachine-Miyamori ophiolite , 2020, American Mineralogist.

[4]  A. Miyashita,et al.  Phengite K-Ar ages of the Yamagami Metamorphic Rocks in the Motai-Matsugataira Belt , 2020, The Journal of the Geological Society of Japan.

[5]  A. Tamura,et al.  Magma mixing model for the genesis of middle crust in the Izu–Bonin–Mariana arc: evidence from plutonic rocks in the Mineoka-Setogawa ophiolitic mélange, central Japan , 2020, International Geology Review.

[6]  H. Maekawa,et al.  Serpentinization and blueschist-facies metamorphism beneath the Mariana forearc , 2017 .

[7]  M. Takeuchi,et al.  Ophiolites and ultramafic rocks , 2016 .

[8]  T. Tsujimori,et al.  Palaeozoic basement and associated cover , 2016 .

[9]  Y. Asahara,et al.  Evolution processes of Ordovician–Devonian arc system in the South‐Kitakami Massif and its relevance to the Ordovician ophiolite pulse , 2015 .

[10]  Y. Ichiyama.  Petrogenesis and geotectonics of the Mikame ultramafic body, western Shikoku, Japan , 2015 .

[11]  Y. Ichiyama,et al.  Jurassic plume-origin ophiolites in Japan: accreted fragments of oceanic plateaus , 2014, Contributions to Mineralogy and Petrology.

[12]  J. Sasaki,et al.  LA-ICP-MS zircon U-Pb geochronology of Paleozoic granitic rocks and related igneous rocks from the Kurosegawa tectonic belt in Kyushu, Southwest Japan , 2014 .

[13]  英男 石塚,et al.  九州・黒瀬川構造帯における古生代花崗岩類および関連火成岩類の LA-ICP-MS ジルコン U-Pb 年代 , 2014 .

[14]  K. Hattori,et al.  Geochemistry of subduction zone serpentinites: A review , 2013 .

[15]  S. Machida,et al.  Tectonics of small ultramafic bodies in Northeast Japan, inferred from chemical composition of chromian spinels , 2013 .

[16]  F. Hawthorne,et al.  Nomenclature of the amphibole supergroup , 2012 .

[17]  茂徳 丸山,et al.  南部北上帯古期岩類のLA-ICP-MS U-Pbジルコン年代 , 2010 .

[18]  M. Kawamura,et al.  Sodic-calcic amphiboles found from dolerite in the Nedamo Terrane, Northeast Japan , 2010 .

[19]  M. Kawamura,et al.  Glaucophane found from meta-basalt in the Nedamo Terrane, Northeast Japan, and its geologic significance , 2010 .

[20]  T. Hirata,et al.  LA-ICP-MS U-Pb Age of Some Older Rocks of the South Kitakami Belt, Northeast Japan , 2010 .

[21]  S. Arai,et al.  Hydrous peridotites with Ti-rich chromian spinel as a low-temperature forearc mantle facies: evidence from the Happo-O’ne metaperidotites (Japan) , 2010 .

[22]  Y. Ichiyama,et al.  Petrogenesis of greenstones from the Mino–Tamba belt, SW Japan: Evidence for an accreted Permian oceanic plateau , 2008 .

[23]  S. Arai,et al.  Calcic amphiboles in peridotite xenoliths from Avacha volcano, Kamchatka, and their implications for metasomatic conditions in the mantle wedge , 2008 .

[24]  M. Kawamura,et al.  Phengite 40Ar/39Ar age of garnet-bearing pelitic schist pebble obtained from conglomerate in the Nedamo Terrane, Northeast Japan , 2008 .

[25]  川村 信人,et al.  380Ma 40Ar/39Ar ages of the high-P/T schists obtained from the Nedamo Terrane, Northeast Japan , 2007 .

[26]  K. Ozawa,et al.  Rb–Sr and Sm–Nd isotopic systematics of the Hayachine–Miyamori ophiolitic complex: Melt generation process in the mantle wedge beneath an Ordovician island arc , 2007 .

[27]  隆之 内野,et al.  根田茂帯(旧"早池峰帯")から発見された藍閃石を含む苦鉄質片岩とその意義 , 2006 .

[28]  T. Morishita,et al.  Determination of Multiple Trace Element Compositions in Thin (> 30 μm) Layers of NIST SRM 614 and 616 Using Laser Ablation‐Inductively Coupled Plasma‐Mass Spectrometry (LA‐ICP‐MS) , 2005 .

[29]  W. Seyfried,et al.  REE controls in ultramafic hosted MOR hydrothermal systems: An experimental study at elevated temperature and pressure , 2005 .

[30]  Y. Ichiyama,et al.  Petrochemical evidence for off‐ridge magmatism in a back‐arc setting from the Yakuno ophiolite, Japan , 2004 .

[31]  T. Tsujimori.  Origin of serpentinites in the Omi serpentinite melange (Hida Mountains, Japan) deduced from zoned Cr-spinel , 2004 .

[32]  T. Nozaka.  Compositional heterogeneity of olivine in thermally metamorphosed serpentinite from Southwest Japan , 2004 .

[33]  S. Vysotskiy,et al.  Petrological diversity and origin of ophiolites in Japan and Far East Russia with emphasis on depleted harzburgite , 2003, Geological Society, London, Special Publications.

[34]  S. Miyashita,et al.  Petrology of the greenstones of the Lower Sorachi Group in the Sorachi–Yezo Belt, central Hokkaido, Japan, with special reference to discrimination between oceanic plateau basalts and mid‐oceanic ridge basalts , 2002 .

[35]  M. Kawamura,et al.  Late Devonian conodont age of red chert intercalated in greenstones of the Hayachine Belt, Northeast Japan. , 2002 .

[36]  B. McInnes,et al.  Hydrous metasomatism of oceanic sub-arc mantle, Lihir, Papua New Guinea: Part 2. Trace element characteristics of slab-derived fluids , 2001 .

[37]  S. Maruyama,et al.  Activation of Pacific mantle plumes during the Carboniferous: Evidence from accretionary complexes in southwest Japan , 2000 .

[38]  S. Barnes.  Chromite in Komatiites, II. Modification during Greenschist to Mid-Amphibolite Facies Metamorphism , 2000 .

[39]  S. Sano,et al.  Geochemical characteristics of Carboniferous greenstones in the Inner Zone of Southwest Japan , 2000 .

[40]  T. Tsujimori,et al.  Blueschist‐facies metamorphism during Paleozoic orogeny in southwestern Japan: Phengite K–Ar ages of blueschist‐facies tectonic blocks in a serpentinite melange beneath early Paleozoic Oeyama ophiolite , 1999 .

[41]  R. Vannucci,et al.  The Finero phlogopite-peridotite massif: an example of subduction-related metasomatism , 1999 .

[42]  樹 辻森.  中国山地中央部,大佐山蛇紋岩メランジュの地質:大江山オフィオライトの下に発達した320 Ma 青色片岩を含む蛇紋岩メランジュ , 1998 .

[43]  A. Klaus,et al.  GEOCHEMICAL EVIDENCE FOR A MID-CRETACEOUS SUPERPLUME , 1998 .

[44]  S. Jackson,et al.  A Compilation of New and Published Major and Trace Element Data for NIST SRM 610 and NIST SRM 612 Glass Reference Materials , 1997 .

[45]  N. Shimizu,et al.  Open‐system melting in the upper mantle: Constraints from the Hayachine‐Miyamori ophiolite, northeastern Japan , 1995 .

[46]  W. McDonough,et al.  The composition of the Earth , 1995 .

[47]  S. Arai.  Compositional variation of olivine-chromian spinel in Mg-rich magmas as a guide to their residual spinel peridotites , 1994 .

[48]  M. Ehiro,et al.  K-Ar ages of amphibolites from the Matsugadaira-Motai Metamorphics and their significance , 1992 .

[49]  K. Ozawa,et al.  Ordovician arc ophiolite, the Hayachine and Miyamori complexes, Kitakami Mountains, Northeast Japan: isotopic ages and geochemistry , 1992 .

[50]  T. Ishii,et al.  Petrological studies of peridotites from Diapiric Serpentinite seamounts in the Izu-Ogasawara-Mariana forearc, Leg125 , 1992 .

[51]  K. Ozawa.  Ultramafic tectonite of the Miyamori ophiolitic complex in the Kitakami Mountains, Northeast Japan: hydrous upper mantle in an island arc , 1988 .

[52]  K. Ozawa,et al.  K-Ar ages of hornblende in gabbroic rocks from the Miyamori ultramafic complex of the Kitakami Mountains , 1988 .

[53]  R. Berman,et al.  Heat capacity of minerals in the system Na2O-K2O-CaO-MgO-FeO-Fe2O3-Al2O3-Sio2-TiO2-H2O-CO2: representation, estimation, and high temperature extrapolation , 1985 .

[54]  H. Dick,et al.  Chromian spinel as a petrogenetic indicator in abyssal and alpine-type peridotites and spatially associated lavas , 1984 .

[55]  H. Maekawa.  Geology of the Motai Group in the southwestern part of the Kitakami Mountains , 1981 .

[56]  S. Arai.  Dunite—Harzburgite—Chromitite Complexes as Refractory Residue in the Sangun—Yamaguchi Zone, Western Japan , 1980 .

[57]  B. W. Evans,et al.  Chrome-spinel in progressive metamorphism—a preliminary analysis , 1975 .

[58]  S. Arai.  Contact metamorphosed dunite-harzburgite complex in the Chugoku district, western Japan , 1975 .

[59]  蟹沢 聡史.  Metamorphic rocks of the southwestern part of the Kitakami Mountainland, Japan , 1964 .

[60]  Kozo Takahashi,et al.  On the Motai Group of the Kitakami Massif, Japan , 1962 .

[61]  M. Shimazu.  On the Glaucophane Rock found in the Kitakami-Mountainland , 1959 .

[62]  M. Shimazu.  Mafic and ultramafic rocks in the Takozu district, southwestern Kitakami mountain-land (I) , 1954 .