Performance information

• 生活（科）改善計画1 : 日米における小学校低学年科学教育の違い　　　　　　　　　　　　　　　
  竹田,莉乃; 岡本,和明; 西崎,さくら
  Volume：73, Number：2, First page：341, Last page：347, Mar. 2025, [Corresponding]
• The Tokunoshima Belt: A New Geotectonic Unit in Central Ryukyus, Japan　　　　　　　　　　　　　　　
  Hiroshi Yamamoto; Yukio Isozaki; Kazuaki Okamoto
  Journal of Geography (Chigaku Zasshi), Volume：133, Number：6, First page：447, Last page：464, Dec. 2024, [Reviewed]
  The latest geological and geotectonic aspects of Tokunoshima Island in Central Ryukyus are reviewed. The pre-Quaternary basement geology of the island is two-fold; i.e., the Cretaceous accretionary complex （Amagidake and Omo units） and the high-grade metamorphic unit newly named the Inokawadake metamorphic complex （IMC）. The former is correlated with the northern subbelt of the Shimanto belt in SW Japan. The IMC is composed of high-grade metamorphic rocks composed of pelitic–psammitic schists, with minor lenses of serpentinite and “dioritic gneiss” with Paleoproterozoic （ca. 1.8 Ga） zircons. In the southern half of the island, the IMC structurally overlies the Cretaceous AC as a klippe, which is separated probably by a subhorizontal fault. The IMC suffered from high-grade metamorphism up to the amphibolite facies, which is extremely rare in the Shimanto belt. A new geotectonic unit, the Tokunoshima belt, is newly proposed for the area of the IMC, which is limited to a mountainous domain in southern Tokunoshima Island. Based on the youngest detrital zircon U-Pb ages （ca. 60 Ma） from psammitic schists, the metamorphism of the IMC probably occurred in the Paleocene or later. Possible sites for the Paleocene or later heat source may include the San-in （Paleogene batholith） belt in SW Japan on the north and/or an unknown collided island arc system from the south.
  Scientific journal
  DOI：https://doi.org/10.5026/jgeography.133.447
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  DOI ID：10.5026/jgeography.133.447, ISSN：0022-135X, eISSN：1884-0884, SCOPUS ID：85216956898
• Earth Environmental Problems and the Theory of Human and Nature : Definitions of Human, Nature, and the Earth Environment in the High School Designated Subject “Environmental Fundamentals”　　　　　　　　　　　　　　　
  三上 裕香; 岡本 和明
  Volume：73, Number：1, First page：285, Last page：293, Apr. 2024, [Corresponding]
  text
  application/pdf
  Faculty of Education, Saitama University, Japanese
  DOI：https://doi.org/10.24561/0002000448
  DOI ID：10.24561/0002000448, eISSN：1881-5146
• Enjoyable Volcanic Eruption Experiments in Science Class at Junior-High School : Analogue Experiments of Volcanic Eruption Based on Kitchen Earth Sciences　　　　　　　　　　　　　　　
  柴田 大介; 渡辺 桃子; 三浦 脩; 岡本 和明
  Volume：72, Number：2, First page：279, Last page：288, Sep. 2023, [Corresponding]
  text
  application/pdf
  Faculty of Education, Saitama University, Japanese
  DOI：https://doi.org/10.24561/0002000206
  DOI ID：10.24561/0002000206, eISSN：1881-5146
• Science Education on Rivers in Mongolia : Characteristics of Rivers and Blessings of Nature　　　　　　　　　　　　　　　
  エレデネ オチル アリウンボヤン; 三上 裕香; 岡本 和明
  Volume：72, Number：2, First page：289, Last page：300, Sep. 2023, [Corresponding]
  text
  application/pdf
  Faculty of Education, Saitama University, Japanese
  DOI：https://doi.org/10.24561/0002000207
  DOI ID：10.24561/0002000207, eISSN：1881-5146
• Pressure Calibrations of Quartz and Zircon Under Hydrostatic Condition up to 1 GPA Using Dac　　　　　　　　　　　　　　　
  三浦 脩; 久保 和希; 岡本 和明
  Volume：72, Number：1, First page：255, Last page：266, Apr. 2023, [Corresponding]
  type:text
  Japanese
  DOI：https://doi.org/10.24561/00019890
  DOI ID：10.24561/00019890, ISSN：1881-5146
• Improvement of University Experimental Class for Growth of Scientific Ability : Case Study from Earth Science Class in U.S.’s University, and Experimental Class in Studio Education　　　　　　　　　　　　　　　
  竹内 智美; 大塚 裕加里; 三上 裕香; 岡本 和明
  Volume：71, Number：2, First page：465, Last page：474, Nov. 2022, [Corresponding]
  type:text
  Japanese
  DOI：https://doi.org/10.24561/00019706
  DOI ID：10.24561/00019706, ISSN：1881-5146
• Oxygen isotope data of quartz from San-yo and Ryoke belt granites, schists, and siliceous veins: constraining the effects of ¹⁸O-rich fluids on granitic magma　　　　　　　　　　　　　　　
  Hafiz Ur Rehman; Hiroshi Yamamoto; Tayyaba Mateen; Kazuaki Okamoto; Tzen Fu Yui; Masaru Terabayashi; Kazuaki Nanamura
  Episodes, Volume：45, Number：2, First page：147, Last page：159, Jun. 2022, [Reviewed]
  Oxygen isotope data (δ18O) of quartz are reported for the San-yo and Ryoke belt granites, metamorphic rocks, and late-stage siliceous veins. The analyzed quartz showed δ18O values of 9.7-12.9‰ (relative to VSMOW) in granites, 15.1-17.3‰ in biotite schist, 16.4-17.8‰ in siliceous schist. The δ18O values of quartz in foliation-parallel and -normal veins are 16.6‰ and 17.3‰, respectively. The δ18O values of quartz in the granite samples are relatively higher than those crystallized from I-type granite magma (ca. 5–8‰) and similar with values of S-type granite magma (ca. 9–12‰). These features suggest partial melting of the chemically modified crust with sedimentary precursors to form the parental magma of granites. Hafnium isotope data of zircons from those granites, reported in an earlier publication, exhibited by εHf (t) values between +1.1 and -4.8, provide additional evidence for the formation of the granites from a continental crust with some incorporation of hydrothermally altered reworked crust before partial melting. The relatively higher δ18O values (> 15‰) of quartz in siliceous veins indicate their precipitation from silica- and 18O-rich fluids that were extracted from the slab-dehydration process during late-stages of their evolution.
  Scientific journal
  DOI：https://doi.org/10.18814/epiiugs/2021/021012
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  DOI ID：10.18814/epiiugs/2021/021012, ISSN：0705-3797, SCOPUS ID：85132506279
• Paleoproterozoic to Cenozoic zircon U–Pb ages with Hf signatures from metamorphic rocks and granodiorite of Tokunoshima: constraints on the geotectonic subdivision of the Ryukyu island arc, Southwest Japan　　　　　　　　　　　　　　　
  Hiroshi Yamamoto; Kazuaki Okamoto; Sun Lin Chung; Hao Yang Lee; Yuji Mita; Shuro Ueda; Masaru Terabayashi
  International Geology Review, Volume：64, Number：3, First page：425, Last page：440, Mar. 2022, [Reviewed]
  LA-ICP-MS U–Pb and Hf isotope analysis was conducted on zircons from the metamorphic unit of Omo Formation and a granodorite body of Tokunoshima in the Amami Islands, Southwest Japan. Zircons from dioritic gneiss (S9, S46) and pelitic schist (S99) yielded Paleoproterozoic upper intercept and Early Jurassic lower intercept ages. The positive εHf(t) values of the Paleoproterozoic zircons (between +12.7 and 0.8) and the negative εHf(t) values of the Jurassic zircons (−19.6 and −22.8) indicate Early Jurassic reworking of the older continental crust. The results suggest that the Omo Formation is an eastern equivalent of Cathaysia of the South China block. Zircons from granodiorite (S62) yielded a 206Pb/238U mean age of 61.3 ± 1.0 Ma with positive εHf(t) values of +12.0 and +12.6. The εHf(t) values indicate juvenile magmatic activity, which is correlated with that in the San-in batholith belt of Southwest Japan. Dioritic gneiss (S30) and psammitic schist (P91) yielded zircon U–Pb ages comparable to that of granodiorite (S62) with positive εHf(t) values (from +6.4 to +10.4). This suggests that the intrusion of the granodiorite induced the crystallization of zircon grains in the host rocks.
  Scientific journal
  DOI：https://doi.org/10.1080/00206814.2020.1858356
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  DOI ID：10.1080/00206814.2020.1858356, ISSN：0020-6814, eISSN：1938-2839, SCOPUS ID：85098483728
• Intra-oceanic arc accretion along Northeast Asia during Early Cretaceous provides a plate tectonic context for North China craton destruction　　　　　　　　　　　　　　　
  Jeremy Tsung Jui Wu; Jonny Wu; Kazuaki Okamoto
  Earth-Science Reviews, Volume：226, Mar. 2022, [Reviewed]
  North China craton destruction (i.e., NCC destruction) during the Early Cretaceous is typically considered within the context of continuous, westward subduction of the Izanagi /paleo-Pacific plate beneath eastern Eurasia (i.e., Andean-style subduction). However, geological evidence indicates intra-oceanic arc accretions along east Eurasia during the Early Cretaceous that are incompatible with Andean-style plate tectonics. Here we review oceanic terrane accretions along NE Asia during Cretaceous times from published magmatism, stratigraphy, and paleomagnetism. We synthesize an alternative ‘intra-oceanic subduction’-style NE Asian plate tectonic model between ~15–40° N latitudes during the Early Cretaceous (130–100 Ma) and discuss implications for NCC destruction. Well-known NE Asian magmatism migrated >1000 km inboard to NE China during the Jurassic, and then >1000 km outboard during early Cretaceous (140–110 Ma). Early Cretaceous NE Asian igneous rocks include: (1) arc-related igneous rocks, (2) 132–99 Ma adakites in Japan and Sikhote-Alin, and (3) 145–120 Ma K-rich adakites in NE China. Roughly co-eval to these periods (130 to 100 Ma), intra-oceanic arcs accreted diachronously along the Sambagawa belts, SW Japan, Oku-Niikappu belts, NE Japan, and Kema and Kiselevka-Manoma, Russian Far East. Based on the adakite geochemistry and spatiotemporal overlap between the arc accretions and adakites, we link the NE China adakites to lower NCC crustal melting, whereas the Japan-Sikhote Alin adakites originated from oceanic slab melting. We show that eastern Eurasia-NW Panthalassan plate tectonics during the Early Cretaceous was more complex than generally recognized, involving intra-oceanic subduction zones and multiple oceanic plates. The Early Cretaceous-aged NE Asian adakites were generated within elevated mantle geotherms during 140–110 Ma slab rollback and 130–100 Ma intra-oceanic arc accretions. Oceanic mantle emplaced during these events replaced the NCC subcontinental lithospheric mantle with more juvenile mantle during final NCC destruction at 115 Ma. The more complete plate tectonic picture provided here suggests that NCC destruction models that rely on straightforward Andean-style subduction are likely oversimplified. Instead, future NCC destruction studies should include more complex geodynamics with intra-oceanic subduction and additional plates that will alter boundary conditions for geodynamic modeling, petrogenesis, and magmatic mixing models.
  DOI：https://doi.org/10.1016/j.earscirev.2022.103952
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  DOI ID：10.1016/j.earscirev.2022.103952, ISSN：0012-8252, SCOPUS ID：85124071735
• 理科の単元系統性とコア単元 : スパイダーウェブによる単元系統解析<数学・自然科学>—Unit Systematicness of the Science and Core Units : Unit Systematics Based on the Spiderweb Analysis　　　　　　　　　　　　　　　
  岡本, 和明; 大塚, 裕加里; 三上, 裕香; エレデネ・, オチル・アリウンボヤン
  Volume：70, Number：1, First page：201, Last page：208, Jun. 2021, [Lead, Corresponding]
  type:text
  Japanese, Research institution
  DOI：https://doi.org/10.24561/00019231
  DOI ID：10.24561/00019231, ISSN：1881-5146, CiNii Articles ID：120007098439
• 科学力育成のための地学オンライン実験 : 河川の特徴、災害と自然の恵み<数学・自然科学>—Online Experimental Class in Geoscience for Development of Scientific Ability : River Characteristics, Flood Disasters, and Blessings from Nature　　　　　　　　　　　　　　　
  三上, 裕香; 大塚, 裕加里; エレデネ・, オチル・アリウンボヤン; 岡本, 和明
  Volume：70, Number：1, First page：187, Last page：199, Jun. 2021, [Corresponding]
  type:text
  This paper reports how to educate river characteristics, flood disasters and blessings from nature in online-geoscience-class. Japanese Islands are characterized by rivers which flows from high mountains to the river-mouth with steep streams, and suffers floods caused by heavy rains. Therefore, river educations are important in science class at school. It is required to learn water flow and river from 4th to 6th grades in Japanese primary school. However, field observation of rivers is limited in nearby area from school. It is necessary to observe from head stream in steep mountain, to river mouth in bay area. Online experimental class is quite useful and powerful tool to teach the essence of river to school children. Based on courses of study (determined by Ministry of Education, Culture, Sports, Science and Technology, Japan), we propose online experimental classes for river as follows.1)birds-eye-view observation using satellite image in google earth, and video learning program(NHK for school, rika)2)updated geo-hazard map (geographic information system map- natural disasters caused by rivers)3)demonstrating simple boiling experiments using hard water and soft water how to make tasty Japanese and European dashi (soup stock).In the 3), we used kelp and pork with the mineral water (hard water and soft water). The soft water is dominant as Japanese mineral water, especially in Kansai region. Because the soft water does not contain enough calcium to rid soup of the harshness caused by animal meat, dashi (e.g. kelp stock) plays significant role in washoku (Japanese cuisine). Besides, the soft water extracts umami whereas certain amount of minerals in the hard water seal the surface the umami gradients. On the other hand, strong smell of meat and poultry can be removed as scum when boiled in the hard water. Therefore, pork soup stock is better for the hard water. Thus, the dashi (kelp stock) is blessing from Japanese soft water from rivers.
  Japanese, Research institution
  DOI：https://doi.org/10.24561/00019230
  DOI ID：10.24561/00019230, ISSN：1881-5146, CiNii Articles ID：120007098438
• Reply to Comment on ‘Metamorphic olivine after dehydration embrittlement in Serpentinite: Case study from the Shiraga Serpentinite mass in the Sanbagawa high P/T metamorphic belt, central Shikoku, Japan’ by Wallis and Endo, https://doi.org/10.1111/iar.12328　　　　　　　　　　　　　　　
  Seiya Fukumura; Kazuaki Okamoto; Masaru Terabayashi
  Island Arc, Volume：29, Number：1, Jan. 2020, [Reviewed], [Corresponding]
  DOI：https://doi.org/10.1111/iar.12338
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  DOI ID：10.1111/iar.12338, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：85081633658
• LA-ICP-MS zircon U-Pb age and Hf isotope data from the granitic rocks in the Iwakuni area, Southwest Japan: re-evaluation of emplacement order and the source magma　　　　　　　　　　　　　　　
  Tayyaba Mateen; Kazuaki Okamoto; Sun Lin Chung; Kuo Lung Wang; Hao Yang Lee; Shuhei Abe; Yuji Mita; Hafiz U. Rehman; Masaru Terabayashi; Hiroshi Yamamoto
  Geosciences Journal, Volume：23, Number：6, First page：917, Last page：931, Dec. 2019, [Reviewed]
  U-Pb-Hf isotopes of zircons from the granitic intrusive rocks in the Iwakuni area of Southwest Japan are determined by LA-ICP-MS analysis. The Gamano Granodiorite belonging to the Older Ryoke Granites of the Ryoke Belt yielded U-Pb mean age of 92.3 ± 2.6 Ma (MSWD = 1.8). The Namera Granite belonging to the Younger Ryoke Granites of the Ryoke Belt yielded U-Pb mean age of 106.3 ± 1.6 Ma (MSWD = 2.3). The Shimokuhara Granite belonging to the Hiroshima Granites of the San-yo Belt yielded U-Pb mean age of 103.8 ± 1.5 Ma (MSWD = 0.32). A granite porphyry sample taken from about 15 m thick dike discordantly intruded into pelitic schist of the Ryoke metamorphic rocks yielded U-Pb mean age of 92.5 ± 1.6 Ma (MSWD = 0.63). Hf isotope data, obtained from the same dated zircon grains, show initial 176Hf/177Hf isotopic ratios referred to as “εHf(t)” generally ranging between–4.8 and +1.1 except an anomalously low value (–15.0) from an inherited core. The εHf(t) values, calculated with average crustal 176Lu/177Hf ratio of 0.015, correspond to Hf isotope crustal model ages between 1474 to 1087 Ma (Mesoproterozoic). The Gamano Graodiorite has long been regarded to be a syn-tectonic intrusion, but the zircon ages and εHf(t) values are similar to those of the post-tectonic granite porphyry dike. The results of this study together with available U-Pb zircon ages of granitic rocks in the Iwakuni area reported elsewhere reveal that the order of emplacement indicated by the U-Pb zircon ages are much discrepant with the traditional classification, the Older Ryoke, the Younger Ryoke. It is better to refrain from the use of “Older” and “Younger” for the collective names of the granitic intrusive bodies.
  Scientific journal
  DOI：https://doi.org/10.1007/s12303-019-0003-1
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  DOI ID：10.1007/s12303-019-0003-1, ISSN：1226-4806, eISSN：1598-7477, SCOPUS ID：85073534881
• モンゴルの資源、地質を生かした自然科学教育 : 琥珀入り石炭を用いた実験<数学・自然科学>　　　　　　　　　　　　　　　
  折原 有紀; 堀口 輝樹; 森田 めぐみ; 安藤 祐美; 岡本 和明
  Volume：68, Number：2, First page：487, Last page：493, Oct. 2019, [Corresponding]
  type:text
  This paper reports an example of simple experiment using amber-bearing coal-stone. The aim of this experiment is to grow scientific interest and ability for Mongolian students. School science teachers in Mongolia, is now required to develop Mongolia as natural resource- and science-technology based country. We have analyzed the science class room conditions in Mongolia and proposed better experimental plans for science classes as follows. In physics, and chemistry, conventional experimental kits are desired to make by school teachers teachers themselves in cheaper prices, and encouraged to perform experiments in every unit subjects. In biology and geoscience, experimental classes should be done using Mongolian natural resources. Summer field classes are also very strong to motivate Mongolian family to learn biology and geoscience related to their Mongolian culture, knowledge and history. Coal-stone is most important natural resource for Mongolian people, and amber is very attractive for school children to stimulate their scientific interest. Amber identification is done using ultraviolet light and separation of amber is opearated using density difference between amber and salt water. In such experiment, physics, chemistry and biology knowledges are used. Thus, this amber bearing coal-stone experiment will guide students and teachers to deep science world.
  Japanese
  DOI：https://doi.org/10.24561/00018728
  DOI ID：10.24561/00018728, ISSN：1881-5146, CiNii Articles ID：120006734104
• Thematic section: Orogenic processes in island arcs: Subduction, accretion, collision and recycling　　　　　　　　　　　　　　　
  Hiroshi Yamamoto; John Wakabayashi; Susumu Umino; Masaru Terabayashi; Kazuaki Okamoto; Hafiz Ur Rehman
  Island Arc, Volume：28, Number：2, Mar. 2019, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12292
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  DOI ID：10.1111/iar.12292, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：85059003219
• Metamorphic olivine after dehydration embrittlement in Serpentinite: Case study from the Shiraga Serpentinite mass in the Sanbagawa high P/T metamorphic belt, central Shikoku, Japan　　　　　　　　　　　　　　　
  Seiya Fukumura; Kazuaki Okamoto; Masaru Terabayashi
  Island Arc, Volume：28, Number：2, Mar. 2019, [Reviewed], [Corresponding]
  Metamorphic olivine veins in serpentinites are considered to be a metamorphism dehydration product. However, the previous descriptions of these veins have been from paleo-collision belts such as those in the Alps, Norwegian Caledonides, and Spain. Here the unique metamorphic olivine veins in a mass of serpentinite in the high-pressure/low-temperature (high P/T) Sanbagawa belt was reported. The Sanbagawa belt is a product of the subduction of oceanic plates during the Cretaceous. Elongated olivine-talc veins were observed along shear bands in serpentine mylonite. The olivine's chemical composition is nearly pure forsterite; magnetite is distributed along the boundary of the olivine vein. This clearly suggests that the olivine was formed by the antigorite terminal reaction at a pressure less than 1.5 GPa. The reaction was caused by local heating in the mylonite as there is little evidence of the continuous antigorite breakdown reaction in the serpentinite. Metamorphic olivines are possibly formed in the intraslab earthquake zone of a relatively warm subduction zone such as southwest Japan after the antigorite terminal reaction at P less than 1.5 GPa.
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12293
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  DOI ID：10.1111/iar.12293, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：85059013465
• 日本とタイの化学教育について<数学・自然科学>　　　　　　　　　　　　　　　
  ナンタプ ジラット; 岡本 和明; 冨岡 寛顕; 上坂 智美
  Volume：66, Number：2, First page：569, Last page：574, Oct. 2017, [Corresponding]
  type:text
  This paper reports study about chemistry education in Saitama University and Saitama High School (Kawagoe Girls High School). The aim of the report is to show difference of chemistry education of Japan and Thailand. For the first part, from the view point of visiting foreign chemistry teacher from Thailand, we described the content of lecture classes on chemical experiments, lectures (chemistry), exercises (chemistry exercises) for subjects of science specialization students in Saitama University in Japan. In the second part, we briefly summarize the chemical lecture and experiment classes at the Kawagoe Girls High School. Finally, the chemistry education in Japan and Thailand was critically compared based on the text book, teaching style and quality of experimental class. and Thailand’s chemistry education. During experiment classes teachers in Saitama University and Kawagoe Girls High School give students certain time to think deeply before experiments following instruction sheets. This method gives all students much confidence to proceed the chemistry experiments in the class. Moreover, teachers in Saitama University and Kawagoe Girls High School have given interesting questions and discussions. At the result, it has brought students strong motivation and challenging split to study chemistry in advanced level. Above these teaching methods and teaching system will be applicable in chemistry experimental classes in Thailand’s junior and senior high school.
  Japanese
  DOI：https://doi.org/10.24561/00017856
  DOI ID：10.24561/00017856, ISSN：1881-5146, CiNii Articles ID：120006389470
• 科学力を育成する実験問題 : 鉱物の表面積、密度の関係<数学・自然科学>　　　　　　　　　　　　　　　
  岡本 和明; 森田 めぐみ
  Volume：66, Number：2, First page：575, Last page：584, Oct. 2017, [Corresponding]
  type:text
  This paper reports an example of experimental problem for junior high school students who attend science contest. The aim of this problem sheet is to grow scientific ability to proceed experimental study in Earth Science field. In Japanese school classes, several efforts have done to perform experiments and observation to cultivate scientific ability. However, the class style is still far from real scientific research. In the class, motivation and purpose of the experiments have never been proposed by students themselves. A priori experiments have been always prepared in advance. It should be prepared several alternative experiments then students can choose one of the experiments in recipe. In the present experimental problem, one or two kinds of experiments would be chosen by students themselves. Hypothesis has been well prepared before the experiment although validity of the hypothesis has never been discussed appropriately after the experimental result in the class. In the present experimental problem, the hypothesis is required to answer before the experiment, and detailed discussion is required if the result was different from the hypothesis. It is also noted if unexpected discovery was found. The present study strongly suggest that scientific experiments in junior high school classes can be dramatically improved to be a real science.
  Japanese
  DOI：https://doi.org/10.24561/00017857
  DOI ID：10.24561/00017857, ISSN：1881-5146, CiNii Articles ID：120006389471
• 固体物質の理科学習指導 : 鉱物多結晶体（岩石）の結晶境界の観察<数学・自然科学>　　　　　　　　　　　　　　　
  安藤 祐美; 岡本 和明
  Volume：66, Number：1, First page：265, Last page：276, Mar. 2017, [Corresponding]
  type:text
  This paper reports an example from the Geoscience Summer Experimental Class for school children. The aim of the class was how to teach the relation between the rock and mineral crystals in the interior of the Solid Earth. Generally, school children and even universities students often misunderstand that the solid material is supported by atomic force or molecular force. However, the strength of crustal rocks is obviously weaker than the atomic force. If the atomic force would support rock rigidity, there is no earthquake in the Earth. There are also many university students who believe that the glass has a crystal structure in Japan. Therefore the aim of the present research was preparation of simple recipe for mineral observation for school children. The mineral observation scale ranges from macro to micro scale using bare eyes, microscope to the scanning electron microscope. Based on the observation, mineral polycrystalline structures are investigated using analogue cubic and hexagonal tabular blocks. Following above the recipe, school children attending one-day summer school, had done the observation by themselves and performed the experiments. They learned scientific logic appropriately through the class and have increased their interests in natural minerals.
  Japanese
  DOI：https://doi.org/10.24561/00017816
  DOI ID：10.24561/00017816, ISSN：1881-5146, CiNii Articles ID：120006389431
• EBSD-measured crystal preferred orientation of eclogites from the Sanbagawa metamorphic belt, central Shikoku, SW Japan　　　　　　　　　　　　　　　
  Hafiz Ur Rehman; David Mainprice; Fabrice Barou; Hiroshi Yamamoto; Kazuaki Okamoto
  European Journal of Mineralogy, Volume：28, Number：6, First page：1155, Last page：1168, Mar. 2016, [Reviewed]
  Electron back-scattered diffraction (EBSD) maps and crystal-preferred orientation (CPO) of eclogite-facies (omphacite and garnet) and amphibolite-facies (hornblende and actinolite) phases are reported for understanding the rheological behaviour of crust during subduction. Two types of eclogites from the subduction-related high-pressure/low-temperature type Sanbagawa metamorphic belt, Japan, have been investigated. Type-I eclogite (sample Sb-1) is composed of garnet, omphacite, secondary actinolite and hornblende. Type-II eclogite (samples Sb-2 and Sb-2a) are mainly composed of omphacite, garnet, and retrograde hornblende with no actinolite. Omphacite, the peak eclogite-facies phase, exhibits L-type CPO (maximum density of [001] axes parallel to and high density of {110} poles normal to the lineation) in Type-I eclogite, suggesting intra-crystalline plasticity with [001] {110} and (110){110} active slip systems, indicating a constrictive strain regime at mantle depths. Omphacite in Type-II eclogite exhibits a similar fabric but with much weaker CPO. Using the LS-index symmetry analysis (one for the end-member L-type, zero for the end-member S-type, and intermediate values for LS-types), a progressive change in LS index of 0.80 for Type-I and 0.61 to 0.44 for Type-II eclogites is observed. These values suggest a transition fromaxial extension parallel to the lineation for Sb-1 and weaker CPO associated with pure or simple shear for Sb-2 and Sb-2a. Garnet, the second dominant phase in the eclogite-facies stage, exhibits weak and complex fabric patterns in all eclogite types, behaved like rigid bodies and does not show plastic deformation.Amphibolite-facies phases (e.g., hornblende and actinolite) exhibit more than two types of CPO. Hornblende and actinolite in Type-I eclogite have a strong CPO along [001] axes aligned parallel to the lineation, indicating homotactic crystal growth probably by the replacement of omphacite during the early stages of retrogression. Type-II eclogites have weak CPO in hornblende but with characteristic alignment of [001] parallel to the lineation and other poles to planes (100), (010), and {110} normal to the lineation. This fabric might have resulted from a cataclastic deformation and could be related to the late-"D1" deformation stage in the Sanbagawa metamorphic belt.
  Scientific journal
  DOI：https://doi.org/10.1127/ejm/2016/0028-2574
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  DOI ID：10.1127/ejm/2016/0028-2574, ISSN：0935-1221, eISSN：1617-4011, SCOPUS ID：85015617818
• Petrogenesis and chemogenesis of oceanic and continental orogens in Asia: Current topics, Part I　　　　　　　　　　　　　　　
  Rehman, H.U.; Tsujimori, T.; Okamoto, K.; Spengler, D.
  Island Arc, Volume：23, Number：4, First page：251, Last page：253, Dec. 2014, [Reviewed]
  English, Scientific journal
  DOI：https://doi.org/10.1111/iar.12097
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  DOI ID：10.1111/iar.12097, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：84919664126
• SHRIMP U-Pb dating of zircons related to the partial melting in a deep subduction zone: Case study from the Sanbagawa quartz-bearing eclogite　　　　　　　　　　　　　　　
  Miyuki Arakawa; Kazuaki Okamoto; Keewook Yi; Masaru Terabayashi; Yukiyasu Tsutsumi
  Island Arc, Volume：22, Number：1, First page：74, Last page：88, Mar. 2013, [Reviewed], [Corresponding]
  Dehydrated fluid from a subducting cold slab is considered to cause deep focused earthquakes and island-arc volcanism. The Sanbagawa high P-T metamorphic rocks have been considered as typical cold oceanic material subducted during the Cretaceous. However, we have discovered an eclogite outcrop exhibiting partial melting texture in the Sanbagawa metamorphic belt, central Shikoku, Japan. The discovery is significant because the melt may play an important role in deep-focused earthquakes and the melt itself may directly contribute to the origin of island-arc magmatism. In order to confirm the age of partial melting of Sanbagawa metamorphic rocks, we dated zircons from both the melted portion and the host eclogite using the U-Pb SHRIMP age-dating at the Korean Basic Science Institute. Zircons from the melted portion (SHT16, 75) are rounded and have sector zoning. The core and mantle yield U-Pb age in the 130-113Ma range (120Ma average), and the rim ages are in the 115-104Ma range. Zircons from the eclogite (SHT15, 76) have a homogenous core with thin mantle and rims. The U-Pb ages are concentrated at 123-112Ma. These pieces of evidence suggest that the eclogite metamorphism occurred at about 120Ma and subsequent partial melting happened at about 110Ma. © 2013 Wiley Publishing Asia Pty Ltd.
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12012
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  DOI ID：10.1111/iar.12012, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：84874381912
• Thematic section: Frontier of micro-scale analysis of HP and UHP rocks　　　　　　　　　　　　　　　
  K. Okamoto; M. Terabayashi; H. Yamamoto
  Island Arc, Volume：22, Number：1, First page：1, Last page：3, Mar. 2013, [Reviewed], [Lead, Corresponding]
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12018
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  DOI ID：10.1111/iar.12018, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：84874358950
• Redox state at ultrahigh-pressure metamorphism: Constraint from the chinese continental scientific drilling eclogites　　　　　　　　　　　　　　　
  Kazuaki Okamoto; Borming Jahn; Tzen Fu Yui; Masahide Akasaka
  Island Arc, Volume：22, Number：1, First page：25, Last page：36, Mar. 2013, [Reviewed], [Lead, Corresponding]
  In order to estimate the fluid composition, C-species of the CCSD (Chinese Continental Scientific Drilling) eclogites were investigated. Graphite is always recognized with pyrite in the eclogites, suggesting their growth from the H2O-rich (CO2-poor) fluids released during metamorphism. The studied eclogites contain vacancy (CaEs component =Ca0.5□0.5AlSi2O6) in clinopyroxene. Therefore, Fe3+ content in clinopyroxene cannot be calculated based on their chemical composition determined by an electron probe micro analyzer. We estimated Fe3+/ΣFe based on the Mössbauer analysis and calculated the pressure-temperature (P-T) conditions from the assemblage of phengite-garnet-clinopyroxene-(coesite) as P=3-4 GPa, and T=650-780°C. The P-T-values obtained in this study show lower values than those which were previously reported elsewhere for the CCSD eclogites, suggesting that the effect of Fe3+ estimation is significant. © 2013 Wiley Publishing Asia Pty Ltd.
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12016
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  DOI ID：10.1111/iar.12016, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：84874366121
• Micro-X-ray absorption near edge structure determination of Fe³⁺/ΣFe in omphacite inclusion within garnet from Dabie eclogite, East-Central China　　　　　　　　　　　　　　　
  Masaru Terabayashi; Takashi Matsui; Kazuaki Okamoto; Hiroaki Ozawa; Yoshiyuki Kaneko; Shigenori Maruyama
  Island Arc, Volume：22, Number：1, First page：37, Last page：50, Mar. 2013, [Reviewed]
  Abstract: The Fe K-edge micro-X-ray absorption near edge structure (XANES) spectra of omphacite included within garnet from the Dabie eclogites, east-central China, were measured to estimate the oxidation state of iron in omphacite. The micro-XANES analyses of omphacite inclusions within garnet yield higher Fe3+/ΣFe ratios of 0.18 to 0.59 than those of 0.00 to 0.31 calculated by charge balance from electron microprobe analyses. The estimated temperatures of garnet-clinopyroxene pairs from 10 eclogites using Fe3+ and Fe2+ contents calculated by charge balance are 603 to 1078°C except one sample. The temperatures calculated using micro-XANES-measured Fe3+ and Fe2+ contents are 530-918°C except one sample. Along the north-south cross-section in the study area, the estimated temperatures based on the charge balance calculation of Fe3+ tend to be identical or higher than temperatures estimated based on the calculation of Fe3+ using the XANES technique. Seven of the micro-XANES measurements give approximate temperatures from 500°C to 700°C, and three of the measurements give temperatures of more than 800°C. Those three samples contain higher XGrs corresponding to the distribution coefficient of garnet-clinopyroxene pairs. The pressure and temperature results estimated by the garnet-clinopyroxene-phengite geothermobarometers are mostly in subsolidus conditions, suggesting that there is no extensive melting in eclogite. The present study represents a new temperature calibration based on Fe3+ estimates in omphacite inclusion within garnet based on the XANES analysis, which is taken into account. © 2013 Wiley Publishing Asia Pty Ltd.
  Scientific journal
  DOI：https://doi.org/10.1111/iar.12017
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  DOI ID：10.1111/iar.12017, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：84874386217
• Dehydrated fluid and seismic deformation in deep subduction zone　　　　　　　　　　　　　　　
  OKAMOTO Kazuaki; KOBAYASHI Masayo; ARAKAWA Miyuki; FUKUMURA Seiya
  Chikyukagaku, Volume：46, Number：4, First page：205, Last page：215, Apr. 2012, [Reviewed], [Lead, Corresponding]
  Dehydrated fluid in deep subduction zone causes various geological phenomena such as earthquake, and arc volcanism. It has been considered that there is a correlation between the double seismic zone and metamorphic dehydration reaction in deep slab. The location of the upper limits of the upper seismic plane correspond to metamorphic facies boundary where H₂O contents change in subducting crust; numerous earthquakes from 60 to 110 km depths in the lawsonite-blueschist facies, many earthquakes in the lower crust of the slab from 110 to 150 km depths in the lawsonite-amphibole eclogite facies and few earthquakes in the lawsonite eclogite facies. Recent petrological researches have revealed that both blue schist and lawsonite eclogite are stable in the same pressure and temperature condition because chemical variation including water content creates both lawsonite-amphibole eclogite and lawsonite eclogite in different portion of subducted crust. Partial melting would occurred in eclogite in deep subduction zone if warm slab is subducted. In descending slab, the eclogite would reach wet solidus defined as phengite-, through zoisite-, and amphibole-decomposition reactions with increasing temperatures. The lower plane of the double seismic zone, is considered to be related to dehydration reaction in the slab. Metamorphic olivine has been described in vein from serpentinite mylonite. The vein was created by dehydration reaction to decompose antigorite under shear deformation. In the cold slab beneath Tohoku arc, the reaction has a negative slope in P-T space and forms olivine + orthopyroxene + fluid. In the warm slab beneath SW Japan, the reaction has a positive slope in P-T space and forms olivine + talc + fluid. The above these dehydration reactions are well-described in the serpentinite from high P/T metamorphic belt from Spain, and Italy, respectively.
  The Geochemical Society of Japan, Japanese
  DOI：https://doi.org/10.14934/chikyukagaku.46.205
  DOI ID：10.14934/chikyukagaku.46.205, ISSN：0386-4073, eISSN：2188-5923, CiNii Articles ID：110009577760, CiNii Books ID：AN00141280
• Intra-oceanic island arc origin for Iratsu eclogites of the Sanbagawa belt, central Shikoku, southwest Japan　　　　　　　　　　　　　　　
  Atsushi Utsunomiya; Bor Ming Jahn; Kazuaki Okamoto; Tsutomu Ota; Hironao Shinjoe
  Chemical Geology, Volume：280, Number：1-2, First page：97, Last page：114, Jan. 2011, [Reviewed]
  New geochemical and Sr-Nd isotopic data for the Iratsu eclogite and surrounding metamorphic rocks of the Sanbagawa belt, Japan, show that, while the protoliths of the metamorphic rocks formed in a variety of tectonic settings, the Iratsu body represents a deeply subducted and accreted island arc. The igneous protoliths of eclogites and garnet amphibolites were probably generated from a mantle source that had components of both a depleted mantle modified by slab-released fluid (as seen in a negative Nb anomaly) and an enriched mantle, similar to that of ocean island basalts (OIB). Fractional crystallization modeling indicates that the protoliths of some garnet clinopyroxenites from the Iratsu body are cumulates from a basaltic magma that crystallized under high O2 and H2O fugacities in the middle to lower crust. The source characteristics and crystallization conditions suggest that the protoliths of the Iratsu rocks formed in an oceanic island arc. Quartz eclogites from the marginal zone of the Iratsu body have geochemical signatures similar to turbidites from the Izu-Bonin island arc (as seen in a negative Nb anomaly and a concave REE pattern). The protoliths might be volcaniclastic turbidites that formed in a setting proximal to the oceanic island arc. Geochemical and isotopic signatures of the surrounding mafic schists are similar to normal (N-) and enriched (E-) mid-ocean-ridge basalt (MORB), and distinct from the rocks from the Iratsu body. The protoliths of the mafic schists likely formed in a plume-influenced mid-ocean ridge or back-arc basin. Pelitic schists from the surrounding rocks and pelitic gneisses from the marginal zone of the Iratsu body have evolved, continental geochemical signatures (as seen in a negative εNd(t) value (~-5)), consistent with their origin as continent-derived trench-fill turbidites. © 2010 Elsevier B.V.
  Scientific journal
  DOI：https://doi.org/10.1016/j.chemgeo.2010.11.001
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  DOI ID：10.1016/j.chemgeo.2010.11.001, ISSN：0009-2541, SCOPUS ID：78650750104
• Detrital zircon evidence for the antiquity of Taiwan　　　　　　　　　　　　　　　
  Ching Ying Lan; Tadashi Usuki; Kuo Lung Wang; Tzen Fu Yui; Kazuaki Okamoto; Yuan Hsi Lee; Takafumi Hirata; Yoshitaka Kon; Yuji Orihashi; Juhn G. Liou; Chun Sun Lee
  Geosciences Journal, Volume：13, Number：3, First page：233, Last page：243, Nov. 2009, [Reviewed]
  In-situ U-Pb geochronology and Hf isotopic studies of zircons from the Pre-Tertiary basement complex and Eocene rocks of the Central Range of Taiwan were carried out to elucidate the history of detrital zircons older than 2.3 Ga. Zircons from the eastern Backbone Range and Eastern Central Range show Paleoproterozoic to late Neoarchean ages (2.3-≥2. 5 Ga), whereas those from the Hsuehshan Range yield Neoarchean to Mesoarchean ages (2.6-3. 2Ga). The εHf(T) for the Paleoproterozoic to late Neoarchean zircons varies from -7.4 to +5.1, implying both juvenile crustal growth and reworking of old crusts. This dual origin could extend back to Mesoarchean-Paleoarchean (3.0-3.4 Ga) based on Hf isotopic model ages. Consistent but narrower εHf(T) values and Hf crustal model ages for zircons from Taiwan compared to Cathaysia suggest a possible common origin for these zircons, although Taiwan has a generally younger crustal evolution history than SE China. © The Association of Korean Geoscience Societies and Springer 2009.
  Scientific journal
  DOI：https://doi.org/10.1007/s12303-009-0023-3
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  DOI ID：10.1007/s12303-009-0023-3, ISSN：1226-4806, eISSN：1598-7477, SCOPUS ID：71249102957
• Early Paleozoic medium-pressure metamorphism in central Vietnam: Evidence from SHRIMP U-Pb zircon ages　　　　　　　　　　　　　　　
  Tadashi Usuki; Ching Ying Lan; Tzen Fu Yui; Yoshiyuki Iizuka; Tich van Vu; Tuan Anh Tran; Kazuaki Okamoto; Joseph L. Wooden; Juhn G. Liou
  Geosciences Journal, Volume：13, Number：3, First page：245, Last page：256, Nov. 2009, [Reviewed]
  To constrain the timing of collisional event in the Indochina block, SHRIMP U-Pb dating and REE analyses of zircon were carried out for two paragneiss samples of the Kham Duc Complex, central Vietnam. Both samples contain kyanite, staurolite, and zoisite as relics from an early metamorphic stage (M1), and biotite and sillimanite as major minerals constituting the foliation formed during the late metamorphic stage (M2). The change in mineral assemblages indicates a clockwise P-T path composed of a high- or medium-P + low-T stage (M1) and a subsequent low- P + high-T stage (M2). The U-Pb concordia ages of zircon rims are 447 ± 6 Ma and 452 ± 6 Ma for the two samples, respectively. These results are distinctly different from the available Ar-Ar mineral ages of 254-225 Ma. Following the clockwise P-T path and phase equilibrium analyses of the Complex, we suggest that the zircon rims were formed near peak temperatures during the decompression. The ∼450 Ma zircon rim thus gives the minimum age constraint for a possible crustal thickening event during Early Paleozoic, whereas the reported Permo-Triassic Ar-Ar ages would result from an Indosinian overprint. This Early Paleozoic event is most likely related to a collisional orogeny between the Indochina and South China blocks. Late Neoproterozoic to Neoarchean ages are recorded from detrital zircon cores of the Kham Duc Complex, the Kontum Massif and Truong Son Belt, suggesting that their protoliths might have derived from sediments at the Gondwana margin. © The Association of Korean Geoscience Societies and Springer 2009.
  Scientific journal
  DOI：https://doi.org/10.1007/s12303-009-0024-2
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  DOI ID：10.1007/s12303-009-0024-2, ISSN：1226-4806, eISSN：1598-7477, SCOPUS ID：71249099792
• Tectonics of the Sanbagawa metamorphic belt, central Sikoku, Japan　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Aoki Kazumasa; Maruyama Shigenori
  The Journal of the Geological Society of Japan, Volume：115, Number：Supplement, First page：37, Last page：49, Sep. 2009, [Reviewed], [Lead, Corresponding]
  三波川変成帯のテクトニクスは，四国中央部での地質学的，岩石学的研究により論じられてきた．しかし沈み込み帯深部で形成された三波川変成岩は上昇し，板状構造を呈して地表では帯状に分布している．そのため三波川変成岩のテクトニクスを理解にするには，上下境界の認定，源岩の起源，変成，源岩年代の決定が重要である．案内者を含む研究グループにより，大歩危地域に三波川変成岩と下盤の四万十帯相当層の境界が存在することが明白になった．さらに四万十相当層の変成条件が青色片岩相の温度圧力条件に達していることが明らかにされた．これは三波川変成岩が，沈み込み帯上面に沿って上昇したことを示す．三波川変成岩の上盤境界の特定は，詳細な年代学的研究により進められてきた．上盤境界が三波川変成岩の上昇に伴う低角正断層運動を起こしたことが明らかになった．源岩岩層単位の地質構造の解析から，三波川変成岩の内部構造は，付加体構造が複数回褶曲作用を受けている．そして，マントルウエッジからのテクトニックブロックやナップと考えられてきた中核部のエクロジャイト，角閃岩も，詳細な地質調査の結果，巨大海山（海台）や海山上の陸源細屑物質の付加体であることが明らかになった．
  The Geological Society of Japan, Japanese
  DOI：https://doi.org/10.5575/geosoc.115.s37
  DOI：https://doi.org/10.1111/iar.12012_references_DOI_IpgehQrXE4q9c65qTccae8ndm91
  DOI ID：10.5575/geosoc.115.s37, ISSN：0016-7630, eISSN：1349-9963, CiNii Articles ID：10030368918
• Late Triassic-Late Cretaceous accretion/subduction in the Taiwan region along the eastern margin of South China –evidence from zircon SHRIMP dating　　　　　　　　　　　　　　　
  TF Yui; K Okamoto; T Usuki; CY Lan; HT Chu; JG Liou
  International Geology Review, Volume：51, Number：4, First page：304, Last page：328, Mar. 2009, [Reviewed]
  To examine the tectonic history of the Taiwan segment of the eastern margin of South China, six rock samples from the Tailuko belt, the metamorphic basement of Taiwan, were selected for zircon SHRIMP dating. The aim was to identify evidence shedding light on the timing of the change from passive to active tectonics for this part of the continental margin since South China separated from the supercontinent of Rodinia. The results lead to two age groups, 190-200 and 88-90Ma. These age groups, augmented by the previously published age data, suggest that they could have resulted from two Mesozoic accretion/subduction events. In addition, this mid-late Mesozoic Tailuko belt might have also been reactivated and structurally complicated by the late Cenozoic collision/accretion of the Luzon arc with the Eurasian continent. Records of older tectonic events, such as those derived from the Japanese Islands, are absent in this metamorphic basement. An important finding of this study is the existence of the 19110Ma Talun metagranite, the oldest granitic intrusion ever reported in the Taiwan region and along the eastern coast area of South China. In spite of a large age uncertainty, the occurrence of this metagranite is not consistent with the apparent younging trend of Jurassic-Cretaceous igneous activity toward the coastline in South China, and should be taken into consideration by future studies.
  TAYLOR & FRANCIS INC, English
  DOI：https://doi.org/10.1080/00206810802636369
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  DOI ID：10.1080/00206810802636369, ISSN：0020-6814, eISSN：1938-2839, SCOPUS ID：70349753794, Web of Science ID：WOS:000264824600002
• Thematic Section: Fluid-rock interaction in the bottom of the inland seismogenic zonePreface　　　　　　　　　　　　　　　
  Masaru Terabayashi; Kazuaki Okamoto; Hiroshi Yamamoto; Yu Chang Chan
  Island Arc, Volume：19, Number：1, First page：1, Last page：3, Mar. 2009, [Reviewed]
  Scientific journal
  DOI：https://doi.org/10.1111/j.1440-1738.2010.00706.x
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  DOI ID：10.1111/j.1440-1738.2010.00706.x, ISSN：1038-4871, eISSN：1440-1738, SCOPUS ID：77950197584
• On-going orogeny in the outer-arc of the Timor-Tanimbar region, eastern Indonesia　　　　　　　　　　　　　　　
  Yoshiyuki Kaneko; Shigenori Maruyama; Ade Kadarusman; Tsutomu Ota; Masahiro Ishikawa; Tatsuki Tsujimori; Akira Ishikawa; Kazuaki Okamoto
  GONDWANA RESEARCH, Volume：11, Number：1-2, First page：218, Last page：233, Jan. 2007, [Reviewed]
  The Timor-Tanimbar islands of eastern Indonesia form a non-volcanic arc in front of a 7 km deep fore-arc basin that separates it from a volcanic inner arc. The Timor-Tanimbar Islands expose one of the youngest high P/T metamorphic belts in the world, providing us with an excellent opportunity to study the inception of orogenic processes, undisturbed by later tectonic events.
  Structural and petrological studies of the high P/T metamorphic belt show that both deformation and metamorphic grade increase towards the centre of the 1 km thick crystalline belt. Kinematic indicators exhibit top-to-the-north sense of shear along the subhorizontal upper boundaries and top-to-the-south sense in the bottom boundaries of the high P/T metamorphic belt. Overall configuration suggests that the high P/T metamorphic rocks extruded as a thin sheet into a space between overlying ophiolites and underlying continental shelf sediments. Petrological study further illustrates that the central crystalline unit underwent a Barrovian-type overprint of the original high P/T metamorphic assemblages during wedge extrusion, and the metamorphic grade ranged from pumpellyite-actinolite to upper amphibolite facies.
  Quaternary uplift, marked by elevation of recent reefs, was estimated to be about 1260 m in Timor in the west and decreases toward Tanimbar in the east. In contrast, radiometric ages for the high P/T metamorphic rocks suggest that the exhumation of the high P/T metamorphic belt started in western Timor in Late Miocene time and migrated toward the east. Thus, the tectonic evolution of this region is diachronous and youngs to the east. We conclude that the deep-seated high P/T metamorphic belt extrudes into shallow crustal levels as a first step, followed by doming at a later stage. The so-called 'mountain building' process is restricted to the second stage. We attribute this Quaternary rapid uplift to rebound of the subducting Australian continental crust beneath Timor after it achieved positive buoyancy, due to break-off of the oceanic slab fringing the continental crust. In contrast, Tanimbar in the east has not yet been affected by later doming. A wide spectrum of processes, starting from extrusion of the high P/T metamorphic rocks and ending with the later doming due to slab break-off, can be observed in the Timor-Tanimbar region. (C) 2006 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.gr.2006.04.013
  DOI ID：10.1016/j.gr.2006.04.013, ISSN：1342-937X, Web of Science ID：WOS:000243473400014
• Water transportation from the subducting slab into the mantle transition zone　　　　　　　　　　　　　　　
  Shigenori Maruyama; Kazuaki Okamoto
  Gondwana Research, Volume：11, Number：1-2, First page：148, Last page：165, Jan. 2007, [Reviewed]
  Using a recently developed petrogenetic grid for MORB + H2O, we propose a new model for the transportation of water from the subducting slab into the mantle transition zone. Depending on the geothermal gradient, two contrasting water-transportation mechanisms operate at depth in a subduction zone. If the geothermal gradient is low, lawsonite carries H2O into mantle depths of 300 km
  with further subduction down to the mantle transition depth (approximately 400 km) lawsonite is no longer stable and thereafter H2O is once migrated upward to the mantle wedge then again carried down to the transition zone due to the induced convection. At this depth, hydrous β-phase olivine is stable and plays a role as a huge water reservoir. In contrast, if the geothermal gradient is high, the subducted slab may melt at 700-900 °C at depths shallower than 80 km to form felsic melt, into which water is dissolved. In this case, H2O cannot be transported into the mantle below 80 km. Between these two end-member mechanisms, two intermediate types are present. In the high-pressure intermediate type, the hydrous phase A plays an important role to carry water into the mantle transition zone. Water liberated by the lawsonite-consuming continuous reaction moves upward to form hydrous phase A in the hanging wall, which transports water into deeper mantle. This is due to a unique character of the reaction, because Phase A can become stable through the hydration reaction of olivine. In the case of low-pressure intermediate type, the presence of a dry mantle wedge below 100 km acts as a barrier to prevent H2O from entering into deeper mantle. © 2006.
  English, Scientific journal
  DOI：https://doi.org/10.1016/j.gr.2006.06.001
  DOI ID：10.1016/j.gr.2006.06.001, ISSN：1342-937X, SCOPUS ID：33845285497
• Zircon-inclusion mineralogy of a diamond-grade eclogite from the Kokchetav massif, northern Kazakhstan　　　　　　　　　　　　　　　
  Kazuaki Okamoto; Ikuo Katayama; Shigenori Maruyama; J. G. Liou
  INTERNATIONAL GEOLOGY REVIEW, Volume：48, Number：10, First page：882, Last page：891, Oct. 2006, [Reviewed], [Lead, Corresponding]
  In order to understand the dehydration process related to phengite decomposition during subduction of crust into the deep mantle, we systematically investigated mineral inclusions in zircons from Kokchetav diamond-grade eclogites. In the eclogites, phengite is absent from the matrix but only occurs as inclusions in clinopyroxene. The clinopyroxene is zoned; the core augite contains K2O up to 0.24 wt%, whereas the rim omphacite contains secondary K-feldspar inclusions. Phengite may have been consumed during prograde reactions, and K was fixed in clinopyroxene or in a fluid/ melt phase. Inclusions of clinopyroxene and garnet were identified in zircon cores, whereas garnet, rutile, quartz, and composite inclusions are present in the mantles and quartz occurs in the rims. Distribution of mineral inclusions in zoned zircons indicates that zircon cores grew at the peak UHP stage, whereas the rims grew in the quartz stability field during decompression. The composite inclusions have assemblages of albite + glass + epidote, rutile + ilmenite, quartz + rutile, and rutile + albite. The former three-phase composite inclusions have rounded outlines and triple-junction grain boundaries, suggesting crystallization from fluid or melt. During the growth of zircon from core to mantle, phengite was consumed, and new garnet, rutile and fluid/melt were formed.
  V H WINSTON & SON INC, English, Scientific journal
  DOI：https://doi.org/10.2747/0020-6814.48.10.882
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  DOI ID：10.2747/0020-6814.48.10.882, ISSN：0020-6814, SCOPUS ID：33750371014, Web of Science ID：WOS:000241136400002
• Fossil fluid reservoir beneath a duplex fault structure within the Central Range of Taiwan: Implications for fluid leakage and lubrication during earthquake rupturing process　　　　　　　　　　　　　　　
  Yu Chang Chan; Kazuaki Okamoto; Tzen Fu Yui; Yoshiyuki Iizuka; Hao Tsu Chu
  Terra Nova, Volume：17, Number：6, First page：493, Last page：499, Dec. 2005, [Reviewed], [Corresponding]
  In order to understand the kinematics which likely facilitated the speedy rupturing process of the 1999 Mw 7.6 Taiwan Chi-Chi earthquake, we examined exposed rocks in the Taiwan Slate belt, where the pressure and temperature conditions most resembled the hypocentre of the Chi-Chi earthquake, i.e. sub-greenschist facies. Field observations and composition analyses of the silicified vein-rich zones beneath the duplex structure suggest that impermeable slate layers may serve as cap rocks for confining deep-seated fluids. These fluids most likely come from the Taiwan metamorphic complex at deeper depths by the dehydration and decarbonation reactions (or partial melting). In addition, the gouge zone of a link fault above the detachment also indicates the presence of overpressured fluids during faulting. It is probable that episodic leakage of the confined fluid reservoirs may provide essential fluids for fault lubrication during earthquake ruptures. © 2005 Blackwell Publishing Ltd.
  Scientific journal
  DOI：https://doi.org/10.1111/j.1365-3121.2005.00636.x
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  DOI ID：10.1111/j.1365-3121.2005.00636.x, ISSN：0954-4879, eISSN：1365-3121, SCOPUS ID：33745274151
• Accretionary complex origin of the mafic-ultramafic bodies of the Sanbagawa belt, central Shikoku, Japan　　　　　　　　　　　　　　　
  TERABAYASHI M; OKAMOTO K; YAMAMOTO H; KANEKO Y; MARUYAMA S; KATAYAMA I; KOMIYA T; OTA T; OZAWA H; ANMA R; WINDLEY B. F; LIOU J. G
  International Geology Review, Volume：47, Number：10, First page：1058, Last page：1073, Dec. 2005, [Reviewed]
  In the high-grade Cretaceous Sanbagawa high-pressure (HP) metamorphic belt, our new 1:5000 scale mapping of eclogitic mafic-ultramafic bodies and their surrounding epidote-amphibolite—facies schists has revealed a duplex structure formed by the subduction of the Izanagi-Pacific oceanic plate. Lithologies of the two largest mafic-ultramafic bodies in the Sanbagawa belt, the Iratsu eclogite and the Higashi-Akaishi peridotite, strike WNW-ESE and dip N; the upper boundary with the surrounding schist is a normal fault, whereas the lower boundary is a thrust. The Iratsu body is subdivided into at least two tectonic units; the unit boundary is subparallel to a lithological boundary. Protoliths of the upper unit are gabbro, basalt, minor quartz rock, and pelite, and those of the lower unit are pyroxenite, gabbro, basalt, chert, and marble, in ascending order. The lower unit is characterized by layers of alternating eclogitic metagabbro and pyroxenite. The layers are extensive at the bottom of the Iratsu eclogite, and transient toward the Higashi-Akaishi body. Eclogitefacies metapsammite is intercalated between the Iratsu and Higashi-Akaishi bodies. Our mapping has revealed the following: (1) a duplex structure of the mafic-ultramafic bodies indicating their accretionary complex origin; (2) reconstructed oceanic plate stratigraphy in ascending order of peridotite, gabbro, basalt, limestone, minor chert, and pelite, suggesting that different parts of the protolith were derived from a mid-oceanic topographic high, an oceanic island or plateau, and an overlying trench turbidite; and (3) a change in the convergent motion of the oceanic plate from NW to NE during the accretion of the large oceanic island or plateau. © 2005 Taylor & Francis Group, LLC.
  Scientific journal
  DOI：https://doi.org/10.2747/0020-6814.47.10.1058
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  DOI ID：10.2747/0020-6814.47.10.1058, ISSN：0020-6814, eISSN：1938-2839, SCOPUS ID：26844435604
• Exhumation tectonics of the sanbagawa high-pressure metamorphic belt, southwest japan—constraints from the upper and lower boundary faults　　　　　　　　　　　　　　　
  Hideki Masago; Kazuaki Okamoto; Masaru Terabayashi
  International Geology Review, Volume：47, Number：11, First page：1194, Last page：1206, Nov. 2005, [Reviewed]
  We have determined the exhumation process of the Sanbagawa Belt based on kinematic analyses of the upper and the lower boundary faults. The Sanbagawa Belt is tectonically intercalated as a thin subhorizontal sheet between overlying, weakly metamorphosed Jurassic and underlying Cretaceous accretionary complexes (e.g., Maruyama et al., 1996). On the lower boundary in Kii Peninsula, pumpellyite—actinolite facies metabasites have undergone semibrittle deformation, indicating a top-to-the south sense of thrusting. The upper boundary in central Shikoku is north-vergent, and indicates a top-to-the north sense of shear; this suggests that the original normal fault on the boundary was warped by later doming. These results support a model of selective exhumation of the Sanbagawa Belt from a depth of 30 km, and its juxtaposition against the over-and underlying accretionary complexes by orogen-orthogonal movements. © 2005 Taylor & Francis Group, LLC.
  Scientific journal
  DOI：https://doi.org/10.2747/0020-6814.47.11.1194
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  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=26844537486&origin=inward
  DOI ID：10.2747/0020-6814.47.11.1194, ISSN：0020-6814, eISSN：1938-2839, SCOPUS ID：26844537486
• Southward extrusion of eclogite-bearing mafic-ultramafic bodies in the Sanbagawa belt, central Shikoku, Japan　　　　　　　　　　　　　　　
  Hiroshi Yamamoto; Kazuaki Okamoto; Yoshiyuki Kaneko; Masaru Terabayashi
  Tectonophysics, Volume：387, Number：1-4, First page：151, Last page：168, Aug. 2004, [Reviewed]
  Several mafic rock masses, which have experienced eclogite facies metamorphism, are distributed in flat-lying non-eclogitic schists in an intermediate structural level (thermal core) of the Sanbagawa belt. The largest, Iratsu mass, and an associated peridotite, the Higashi-Akaishi mass, extend E-W for about 8 km, and N-S for about 3 km, and are surrounded by pelitic, basic and quartz schists. The Iratsu mass consists of metabasites of gabbroic and basaltic origin, with intercalations of ultramafic rocks, felsic gneiss, quartz schist and metacarbonate. The Iratsu mass can be divided into two layers along a WNW-trending metacarbonate layer. The Higashi-Akaishi mass consists of peridotite with intercalations of garnet clinopyroxenite. It is situated beneath the western half of the Iratsu mass, and their mutual boundary dips gently or steeply to the N or NE. These masses underwent eclogite, and subsequent epidote-amphibolite facies metamorphism as has been reported elsewhere. The Iratsu-Higashi-Akaishi masses and the surrounding rocks underwent ductile deformation under epidote-amphibolite facies (or lower P-T) metamorphic conditions. Their foliation generally trends WNW and dips moderately to the NNE, and the mineral lineation mostly plunges to the N and NE. In non-eclogitic schists surrounding the Iratsu-Higashi-Akaishi masses, the foliation generally trends WNW and dips gently or steeply to the N or S and the mineral lineation mostly plunges to the NW, N and NE. Kinematic analysis of deformation structures in outcrops and oriented samples has been performed to determine shear senses. Consistent top-to-the-north, normal fault displacements are observed in peridotite layers of the Higashi-Akaishi mass and eclogite-bearing epidote amphibolite layers of the Iratsu mass. Top-to-the-northeast or top-to-the-northwest displacements also occur in non-eclogitic pelitic-quartz schists on the northern side of the Iratsu mass. In the structural bottom of the Iratsu-Higashi-Akaishi masses and to the south, reverse fault (top-to-the-south) movements are recognized in serpentinized peridotite and non-eclogitic schists. These observations provide the following constraints on the kinematics of the rock masses: (1) northward normal displacement of Iratsu relative to Higashi-Akaishi, (2) northward normal displacement of non-eclogitic schists on the north of the Iratsu mass and (3) southward thrusting of the Iratsu-Higashi-Akaishi masses upon non-eclogitic schists in the south. The exhumation process of the Iratsu-Higashi-Akaishi masses can be explained by their southward extrusion. © 2004 Elsevier B.V. All rights reserved.
  Scientific journal
  DOI：https://doi.org/10.1016/j.tecto.2004.06.014
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  DOI ID：10.1016/j.tecto.2004.06.014, ISSN：0040-1951, SCOPUS ID：11144254015
• The Eclogite-Garnetite transformation in the MORB + H2O system　　　　　　　　　　　　　　　
  Kazuaki Okamoto; Shigenori Maruyama
  Physics of the Earth and Planetary Interiors, Volume：146, Number：1-2, First page：283, Last page：296, Aug. 2004, [Reviewed], [Lead, Corresponding]
  To decipher phase relations of oceanic crust in the coldest slab at the mantle transition zone, multi-anvil experiments were conducted in the MORB+H2O system at pressures of 10-19 GPa, and temperatures of 700-1500 °C. Garnet and stishovite were recognized in all run charges. Above 15 GPa, garnet drastically increases NaSi (Na2MSi5O12) component (M = Ca, Mg, Fe2+), jadeite occurs instead of omphacite. Na-, K-hollandite containing 7 mol% NaAlSi3O8 and Ca-perovskite with 60 mol% CaTiO3, were observed at P> 17 GPa. With decomposition of omphacite and increase of modal ratio of garnet, there is a sharp increase of density at 440 km. The density increase due to appearance of Ca-perovskite at 570 km, is estimated approximately 100 km shallower than that of previous estimation. © 2004 Elsevier B.V. All rights reserved.
  Scientific journal
  DOI：https://doi.org/10.1016/j.pepi.2003.07.029
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  DOI ID：10.1016/j.pepi.2003.07.029, ISSN：0031-9201, SCOPUS ID：3042717142
• SHRIMP U-Pb zircon dating of quartz-bearing eclogite from the Sanbagawa Belt, south-west Japan: Implications for metamorphic evolution of subducted protolith　　　　　　　　　　　　　　　
  Kazuaki Okamoto; Hironao Shinjoe; Ikuo Katayama; Kentaro Terada; Yuji Sano; Simon Johnson
  Terra Nova, Volume：16, Number：2, First page：81, Last page：89, Apr. 2004, [Reviewed], [Lead, Corresponding]
  In order to decipher the origin of eclogite in the high-P/T Sanbagawa metamorphic belt, SHRIMP U-Pb ages of zircons from quartz-bearing eclogite and associated quartz-rich rock (metasandstone) were determined. One zircon core of the quartz-rich rock yields an extremely old provenance age of 1899 ± 79 Ma, suggesting that the core is of detrital origin. Eight other core ages are in the 148-134 Ma range, and are older than the estimated age for trench sedimentation as indicated by the youngest radiolarian fossil age of 139-135 Ma from the Sanbagawa schists. Ages of metamorphic zircon rims (132-112 Ma) from the quartz-rich rock are consistent with metamorphic zircon ages from the quartz-bearing eclogite, indicating that eclogite facies metamorphism peaked at 120-110 Ma. These new data are consistent with both the Iratsu eclogite body and surrounding highest-grade Sanbagawa schists undergoing coeval subduction-zone metamorphism, and subsequent re-equilibration under epidote amphibolite facies conditions during exhumation. © 2004 Blackwell Publishing Ltd.
  Scientific journal
  DOI：https://doi.org/10.1111/j.1365-3121.2004.00531.x
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  DOI ID：10.1111/j.1365-3121.2004.00531.x, ISSN：0954-4879, SCOPUS ID：1942466543
• Petrology of the diamond-grade eclogite in the Kokchetav Massif, northern Kazakhstan　　　　　　　　　　　　　　　
  K. Okamoto; J. G. Liou; Y. Ogasawara
  Island Arc, Volume：9, Number：3, First page：379, Last page：399, Sep. 2000, [Reviewed], [Lead]
  The Kokchetav Massif of northern Kazakhstan is unique because of the abundant occurrence of microdiamond inclusions in garnet, zircon and clinopyroxene of metasediments. In order to determine precise pressure-temperature (P-T) conditions, we have systematically investigated mineral inclusions and the compositions of major silicates in Ti-clinohumite-garnet peridotite and diamond-grade eclogite from Kumdy-Kol. It was found that garnet peridotites from Kumdy-Kol contain assemblages of garnet, olivine, Ti-clinohumite and ilmenite. The garnet contains inclusions that are indicative of both ultrahigh pressure (UHP) and retrograde conditions. Inclusions of hydrous phases such as chlorite, amphibole and zoisite were formed at the post-UHP stage. The study also found that eclogite from Kumdy-Kol contains albite-augite symplectites after omphacitic pyroxene. The core of pyroxene (sodic augite) contains high K2O (up to 1wt%; average 0.24wt%). Phengite is included in the core. Applying the K2O-in-augite geobarometry, which is based on recent experiments, and the garnet-clinopyroxene (Grt-Cpx) geothermometer for peak metamorphism, the eclogites yield P-T estimates of >6 GPa and > 1000°C, and the diamond-grade eclogites yield lower temperature estimates at 900-1000°C and 5 GPa.
  Scientific journal
  DOI：https://doi.org/10.1046/j.1440-1738.2000.00284.x
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  DOI ID：10.1046/j.1440-1738.2000.00284.x, ISSN：1038-4871, SCOPUS ID：0033753385
• Supersilicic clinopyroxene and silica exsolution in UHPM eclogite and pelitic gneiss from the Kokchetav massif, Kazakhstan　　　　　　　　　　　　　　　
  I. Katayama; C. D. Parkinson; K. Okamoto; Y. Nakajima; S. Maruyama
  American Mineralogist, Volume：85, Number：10, First page：1368, Last page：1374, Mar. 2000, [Reviewed]
  Abundant exsolved quartz rods occur in matrix clinopyroxene of eclogite from the Kokchetav massif, Kazakhstan. These rocks are diamond-grade, ultrahigh-pressure (UHP) metamorphic rocks that recrystallized at P > 6 GPa and T > 1000 °C, Zircon is an excellent container, which effectively protects peak UHP metamorphic phases from retrogression. Therefore, to ascertain the pre-exsolution composition of the clinopyroxene, we analyzed clinopyroxene inclusions in zircon of the eclogite and a diamond-bearing biotite gneiss. Clinopyroxene in zircon has an excess of Fe3+ + (VI)Al over (IV)Al + Na + K, and calculated cation totals significantly less than 4.0 per six O atoms. The stoichiometry of these pyroxenes can be reconciled if the Ca-Eskola end-member (Ca0.5[ ]0.5AlSi2O6) is considered. The zircon-hosted clinopyroxene in the eclogite contains up to 9.6 mol% of the Ca-Eskola component, and in the biotite gneiss up to 18.2 mol%, whereas the matrix clinopyroxene contains much less (1.3 mol%, on average). Recalculation of the composition of the matrix clinopyroxene prior to exsolution of quartz rods yields 6.8 mol% Ca-Eskola component, which is consistent with the composition of the clinopyroxene inclusions in zircon. We conclude that the Ca-Eskola component in the peak metamorphic clinopyroxenes broke down by a retrograde reaction: 2 Ca0.5[ ]0.5AlSi2O6 → CaAl2SiO6 + 3 SiO2 resulting in exsolution of the quartz rods in the matrix clinopyroxene. Subducted crustal and supracrustal rocks from the Ca-Eskola clinopyroxene at high pressures and temperatures. The vacancy-containing clinopyroxene may have an important bearing on the physico-chemical properties of the subducted slab at upper mantle depth.
  Scientific journal
  DOI：https://doi.org/10.2138/am-2000-1004
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  DOI ID：10.2138/am-2000-1004, ISSN：0003-004X, SCOPUS ID：0033709289
• Accretionary complex origin of the Sanbagawa, high P/T metamorphic rocks, Central Shikoku, Japan. Layer-parallel shortening structure and greenstone geochemistry.　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Maruyama Shigenori; Isozaki Yukio
  The Journal of the Geological Society of Japan, Volume：106, Number：1, First page：70, Last page：86, Jan. 2000, [Reviewed], [Lead]
  Despite suffering extensive penetrative deformation and high-grade metamorphism up to 600°C and 10-12 kb, Sanbagawa schists of SW Japan preserve imbricate structures and oceanic plate stratigraphy, of MORB, pelagic bedded chert, hemipelagic rocks and overlying turbidites. The field occurrence and petrochemistry of the metabasites suggest that a back-arc basin setting or a passive continental-margin setting is unlikely for their origin. Instead, we suggest that the protoliths of Sanbagawa schists formed in a part of an oceanic plate prior to Cretaceous subduction and incorporation into an accretionary complex.
  The Geological Society of Japan, English
  DOI：https://doi.org/10.5575/geosoc.106.70
  DOI：https://doi.org/10.5026/jgeography.120.115_references_DOI_TqGPi56O7vz1CzVQ4UupzZunR81
  DOI ID：10.5575/geosoc.106.70, ISSN：0016-7630, eISSN：1349-9963, CiNii Articles ID：110003013069, CiNii Books ID：AN00141768
• Plate tectonics at 3.8-3.7 Ga: Field evidence from the Isua Accretionary Complex, southern West Greenland
  Tsuyoshi Komiya; Shigenori Maruyama; Toshiaki Masuda; Toshiaki Masuda; Susumu Nohda; Susumu Nohda; Mamoru Hayashi; Mamoru Hayashi; Kazuaki Okamoto
  Journal of Geology, Volume：107, Number：5, First page：515, Last page：554, Sep. 1999, [Reviewed]
  A 1:5000 scale mapping was performed in the Isukasia area of the ca. 3.8-Ga Isua supracrustal belt, southern West Greenland. The mapped area is divided into three units bounded by low-angle thrusts: the Northern, Middle, and Southern Units. The Southern Unit, the best exposed, is composed of 14 subunits (horses) with similar lithostratigraphy, bound by layer-parallel thrusts. Duplex structures are widespread in the Isua belt and vary in scale from a few meters to kilometers. Duplexing proceeded from south to north and is well documented in the relationship between link- and roof-thrusts. The reconstructed lithostratigraphy of each horse reveals a simple pattern, in ascending order, of greenstone with low-K tholeiitic composition with or without pillow lava structures, chert/banded iron-formation, and turbidites. The cherts and underlying low-K tholeiites do not contain continent- or arc-derived material. The lithostratigraphy is quite similar to Phanerozoic 'oceanic plate stratigraphy,' except for the abundance of mafic material in the turbidites. The evidence of duplex structures and oceanic plate stratigraphy indicates that the Isua supracrustal belt is the oldest accretionary co
  Scientific journal
  DOI：https://doi.org/10.1086/314371
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033367509&origin=inward
  DOI ID：10.1086/314371, ISSN：0022-1376, SCOPUS ID：0033367509
• The high-pressure synthesis of lawsonite in the MORB+H2O system　　　　　　　　　　　　　　　
  Kazuaki Okamoto; Shigenori Maruyama
  American Mineralogist, Volume：84, Number：3, First page：362, Last page：373, Mar. 1999, [Reviewed], [Lead]
  Lawsonite is an important water reservoir in subducting oceanic crust below the amphibole dehydration depth ~70 km. To determine the maximum pressure stability of lawsonite in the MORB+H2O system, experiments were carried out using a 1000 ton uniaxial multi-anvil apparatus (SPI-1000). Mixtures of synthetic gel + 2wt% H2O were used for the starting materials with the average MORB composition. Experimental P-T conditions were T = 700-900 °C and P = 5.5-13.5 GPa. Run durations were 12 and 24 h. Lawsonite was synthesized stably up to 10 GPa and T < 700 °C in the stishovite stability field, and <900 °C at 8 GPa and 750 °C at 5.5 GPa in the coesite stability field, with a steep positive slope for the lawsonite-out reaction. The lawsonite-out reaction in the coesite stability field changes to have a gentle negative slope in the stishovite stability field. The reaction leading to the disappearance of lawsonite is a continuous reaction due to the compositional enlargement of garnet toward the grossular end-member with increasing T and P. Lawsonite disappears when the tie line connecting grossular-rich garnet with omphacitic clinopyroxene reaches the bulk composition on the conventional AC(FM) ternary diagram.
  Scientific journal
  DOI：https://doi.org/10.2138/am-1999-0320
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0033026127&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0033026127&origin=inward
  DOI ID：10.2138/am-1999-0320, ISSN：0003-004X, SCOPUS ID：0033026127
• Multi-anvil re-equilibration experiments of a Dabie Shan ultrahigh-pressure eclogite within the diamond-stability fields　　　　　　　　　　　　　　　
  OKAMOTO K.; MARUYAMA S.
  Island Arc, Volume：7, Number：1, First page：52, Last page：69, Jun. 1998, [Reviewed], [Lead]
  An eclogite (UHP303) formed at ~700°C and P >4 GPa from the Dabie Shan ultrahigh-pressure (UHP) terrane and the same sample +1.1 wt% K2O (UHK303) were used for re-equilibrium experimental studies at P = 2.6-3.2 GPa and T = 900-1000°C, employing a piston cylinder apparatus, and at P = 3-7 GPa and T = 900-1200°C, employing a 1000 ton uniaxial multi-anvil apparatus (SPI-1000). Run products of UHP303 are composed of garnet, sodic augite, with or without a SiO2 phase and phengite. Textural evidence indicates that the solidus lies between 900 and 1000°C at 5 GPa, and above 1000°C at 3 and 7 GPa for UHP303. The solidus temperature decreases to 1000°C at 3-5 GPa and below 900°C at 5 GPa in UHK303. Composition of rock-forming minerals of all run products were determined and compared with those of starting materials. Garnets of all run products have a relatively higher almandine + spessartine component (alm + sps 24-30 mol%) and lower grossular component (12-16) with constant pyrope component (58-61), compared to the starting garent (grs 16-26, alm 21-26, pyp 42-61). The stable Ca-Na pyroxenes are sodic augite rather than omphacite at T higher than 900°C in the P = 3-7 GPa pressure range, and the Cpx compositional gap is completely closed. The K2O content of Ca-Na pyroxenes is a function of P and T, and serves as a potential barometer in the diamont-stability field. Sodium content in garnet is negligible. Using the proposed K2O content in Ca-Na pyroxene as a function of pressure, the maximum Kokchetav UHP condition is suggested to have been 7 GPa at T = 900°C.
  English, Scientific journal
  DOI：https://doi.org/10.1046/j.1440-1738.1998.00179.x
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031710268&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031710268&origin=inward
  DOI ID：10.1046/j.1440-1738.1998.00179.x, ISSN：1038-4871, CiNii Articles ID：10026533340, CiNii Books ID：AA10848628, SCOPUS ID：0031710268
• Inclusion-trial geometry of albite porphyroblasts in a fold structure in the Sambagawa Belt, central Shikoku, Japan　　　　　　　　　　　　　　　
  Kazuaki Okamoto
  Island Arc, Volume：7, Number：1-2, First page：283, Last page：294, Apr. 1998, [Reviewed], [Lead, Corresponding]
  The orientation of straight inclusin trails within albite porphyroblasts from basic schists has been measured around a north-closure fold, in the Besshi district of the Sambagawa Belt, cenral Shikoku, Japan. The porphyroblasts are aligned with their longest dimension parallel to both the subhorizontal, east-west-directed mineral lineation and to the fold axis. There is a systematic variation in inclusion-trail geometry between the upper (northern) and lower (southern) fold limbs. The shear sense deduced from quartz c-axis fabrics is top-too-the-west in the upper limb and top-to-the-east in the lower limb. Based on observed variations in porphyroblast inclusion trails, the structural history can be modelled as follows; i) shear flow caused east-west stretching and folding of the metamorphic zonation; ii) east-west ductile shear resulted in opposing senses of shear in the upper and lower limbs as the eclogite body situated in the core of the fold was extruded to the east.
  Scientific journal
  DOI：https://doi.org/10.1046/j.1440-1738.1998.00176.x
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=0031684790&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=0031684790&origin=inward
  DOI ID：10.1046/j.1440-1738.1998.00176.x, ISSN：1038-4871, SCOPUS ID：0031684790
• A preliminary report on geological structure of the Manotani-Higo metamorphic rocks of the Kosa district, Kyushu　　　　　　　　　　　　　　　
  OKAMOTO,Kazuaki; HARA,Ikuo; SUZUKI,Morihisa
  Volume：33, First page：187, Last page：198, Jul. 1989, [Reviewed], [Lead]
  The Manotani metamorphic rocks are situated just on the north of the Higo metamorphic rocks in the Kosa district, Kumamoto Prefecture, Kyushu. YAMAMOTO (1962) explained that the former is in fault contact with the latter at the west side of the Miyauchi fault (Fig. 1), the fault being associated with intrusion of serpentinite. Both metamorphic rocks show an andalusite-sillimanite type metamorphism, though the Higo metamorphic rocks are of higher grade. In the Manotani metamorphic rocks have been found relicts of minerals such as alkali amphiboles, pumpellyite and lawsonite, suggesting that they were initially metamorphosed under high P/T condition (SATO & INOUE, 1968; KARAKIDA et al., 1984). Through our detailed geological survey, it has been clarified that the Manotani metamorphic rocks are not in fault contact with the Higo metamorphic rocks, and that the former lithologically gradually changes to the latter, though in the former basic metamorphic rocks of probably ophiolitic rock origin are predominant and in the latter siliceous metamorphic rocks of chert origin are predominant. In the transitional horizon between the Manotani and the Higo metamorphic rocks, serpentinite bodies as small lenses are found with various rock types such as pelitic, basic and siliceous metamorphites and the former stratigraphically con formably cover the latter. The Higo metamorphic rocks must have undergone high P/T type metamorphism together with the Manotani metamorphic rocks before the andalusite-sillimanite type metamorphism occurred. The geological structure of the Manotani-Higo metamorphic rocks is characterized by the development of gentle upright folds and of a nappe (Figs. 1, 2). The nappe (Kamakurayama nappe) is developed in the southern part of this district. The Manotani-Higo metamorphic rocks of the nappe is lithologically characterized by the predominance of calcareous metamorphic rocks derived from giant limestone masses, associating
  gneissose granitic rocks. The Manotani-Higo metamorphic rocks are, as a whole, mylonitic. The mylonitization is distinctly intense around the basal thrust (Kamakurayama thrust) of the Kamakurayama nappe, showing that it is related to the formation of the Kamakurayama nappe. In the highly mylonitized metamorphic rocks are found such de formation textures as the development of ribbon quartz and mica fish (Plate I). Ribbon quartz has some time aspect ratio of larger than 17. The Manotani-Higo metamorphic rocks around the Kamakurayama thrust are initially of the stability field of sillimanite associating disappearance of muscovite. However, they now generally show such textures and mineral characteristics of retrograde metamorphism as defined by the appearance of muscovite, chlorite and actinolite. The mylonitization related to the formation of the Kamakurayama nappe is followed by the cataclasis associating the formation of prehnite veins.
  Japanese
  CiNii Articles ID：10013585547, CiNii Books ID：AN00141779

• Relation between Deep-sea Hydrothermal Fluid and Life Activity Deciphered from Accreted Deep-sea Sedimentary Rocks in Japan　　　　　　　　　　　　　　　
  三上裕香; 岡本和明
  日本地球惑星科学連合大会予稿集(Web), 2023
  2023 - 2023
• Pressure calibration of Quartz Raman spectra variation under hydrostatic conditions.　　　　　　　　　　　　　　　
  S Miura; K Okamoto
  AGU Fall Meeting Abstracts 2023 (204), V23D-0204, 2023
• Dehydration embrittlement of subducting serpentinite: case study from the Sanbagawa high P/T metamorphic rock, Japan　　　　　　　　　　　　　　　
  K. Okamoto
  AGU Fall Meeting Abstracts (256), T41D-0256, 2023
• Tectonic relationship between the Ryukyu arc and the South China block shown by structural and zircon U-Pb-Hf isotopic studies of Tokunoshima Island, southwest Japan.　　　　　　　　　　　　　　　
  山本啓司; 岡本和明; 上田脩郎; 寺林優
  日本地質学会学術大会(Web), 2021
  2021 - 2021
• [Invited]Tectonic relationship between the Ryukyu arc and the South China block shown by structural and zircon U–Pb–Hf isotopic studies of Tokunoshima Island, southwest Japan.　　　　　　　　　　　　　　　
  Yamamoto Hiroshi; Okamoto Kazuaki; Ueda Shuro; Terabayashi Masaru
  Annual Meeting of the Geological Society of Japan, 2021, The Geological Society of Japan
  2021 - 2021, Japanese
  琉球弧は九州南端と台湾の間に約 1200 km にわたって連なる島々からなる島弧である．琉球弧の地体構造は、専ら「本州弧の○○帯の延長がどこを通過するか」という観点からから検討されている。地理的に隣接する台湾や中国南東部を含めた議論はほとんどなされていない。日本に比べて台湾や中国の地質情報が不十分という問題があったかもしれないが、その差はなくなりつつある．
  
  徳之島は琉球弧中央のやや北東寄りに位置し，大きさは南北約26 km, 東西約14 km である. 徳之島の地質は，中川(1967)，斎藤ほか (2009)などによる先行研究から要約すると，先古第三紀の堆積岩類，玄武岩質火山岩類，古第三紀の花崗岩質貫入岩類, およびそれらを不整合に覆う第四紀の礁性石灰岩と火砕堆積物から構成されていて, 島の中央部には超マフィック岩類を含むメランジが分布する．Ueda et al., (2017) は, 徳之島中央部の剥岳周辺の詳細な地質踏査と変形構造解析を行い, 斎藤ほか (2009)が「四万十付加体のメランジ」としている岩体が，泥質片岩，砂質片岩，閃緑岩質片麻岩，角閃岩, 超マフィック岩類から構成され，角閃岩相の低圧部に相当する温度圧力条件を経た変成ユニットであることを明らかにして，この変成ユニットの内部構造が北西に緩傾斜するホースからなるデュープレックスであることを提示した．Ueda et al., (2017) は,この変成ユニットの帰属の候補として本州弧の複数の低圧高温型変成帯を挙げているが，特定には至っていない．
  
  Yamamoto et al., (2020) は， Ueda et al., (2017) が記載した砂質片岩，閃緑岩質片麻岩,および島の北部に分布する花崗閃緑岩から分離したジルコンのU–Pb年代 とHf 同位体比を測定し，閃緑岩質片麻岩の2試料から2つのインターセプト上限年代 (1846 ± 27 Ma, 1814 ± 57 Ma) と，1つの 下限年代 (185.9 ± 5.6 Ma)を， 砂質片岩の1試料から1組の上限・下限年代 (2089 ± 18 Ma, 181 ± 15 Ma) を決定した．また，古原生代のジルコン測定スポットが正のε_Hf(t) 値 (+0.8 〜 +12.7) を示し，ジュラ紀の測定スポットが負の値 (-22.8, -19.6) であることから，古原生代に形成された地殻物質が前期ジュラ紀に変成作用を受けたと考えた．Isozaki et al. (2010)などは，南中国地塊に属するカタイシア (Cathaysia)の延長部が沖縄トラフおよび九州北部に達していることを提唱しているが，徳之島中央部の変成ユニットの年代はカタイシアで知られている地殻形成・改変のイベントと調和し，この見解を支持するものである．
  
  Yamamoto et al., (2020) によると，花崗閃緑岩の試料から抽出したジルコンの²⁰⁶Pb/²³⁸U 重み付平均年代は 61.3 ± 1.0 Ma で， ε_Hf(t) 値 (+12.0, +12.6) は未成熟のマグマソースを示す．徳之島の花崗閃緑岩は，暁新世の中国南東部にあった火成活動帯に由来し，その北東延長が本州の山陰帯花崗岩類に相当すると考えられる．
  
  
  
  引用文献
  
  Isozaki et al., 2010, Gondwana Research, 18, 82–105.
  
  中川久夫, 1967,東北大学地質古生物研究邦報, no. 63, 1-39.
  
  斎藤眞ほか, 2009, 20万分の1地質図幅「徳之島」. 産総研.
  
  Ueda et al., 2017, Island Arc, 26. e12199.
  
  Yamamoto et al., 2020. International Geology Review, vol. 63, 1-16.
• Relation between Deep-sea Hydrothermal Fluid and Life Activity Deciphered from Accreted Deep-sea Sedimentary Rocks in Japan　　　　　　　　　　　　　　　
  Y Mikami; K Okamoto
  AGU Fall Meeting Abstracts 2021, B35N-1586, 2021
• Significance of Oceanic-Island-Arc subduction and creation of high P/T metamorphic belt-case study from the Sanbagawa metamorphic belt　　　　　　　　　　　　　　　
  Kazuaki Okamoto
  AGU Fall Meeting Abstracts 2019, T54B-04, 2019
• Deeply subducted Jurassic ridge hydrothermal ore deposit-case study from the Sanbagawa eclogite-blueschist　　　　　　　　　　　　　　　
  Y Otsuka; K Okamoto
  AGU Fall Meeting Abstracts 2019, V43E-0141, 2019
• Geochemical signature of Metabasites from the Sanbagawa metamorphic rocks, Besshi district, Central Shikoku, Japan　　　　　　　　　　　　　　　
  I Shimazaki; K Okamoto
  AGU Fall Meeting 2019, 2019
• Slab dehydration recorded in subducted serpentine sea-mount (Oceanic Island Arc)　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Fukumura Seiya; Ishimori Chiharu
  Annual Meeting of the Geological Society of Japan, 2014, The Geological Society of Japan
  2014 - 2014
• Zircon Nano-SIMS U-Pb dating from the country gneiss surrounding Horoman peridotite –age constraint for tectonic juxtaposition of peridotite body into granulite in Arc-Arc collision zone-　　　　　　　　　　　　　　　
  Suzuki Ryosuke; Okamoto Kazuaki; Yamamoto Hiroshi; Sano Yuji; Takahata Naoto
  Annual Meeting of the Geological Society of Japan, 2013, The Geological Society of Japan
  2013 - 2013
• SHRIMP U-Pb dating of zircons related to the partial melting in deep subduction zone　　　　　　　　　　　　　　　
  ARAKAWA MIYUKI; OKAMTO KAZUAKI; Yi Keewook; TERABAYASHI MASARU
  Annual Meeting of the Geological Society of Japan, 2012, The Geological Society of Japan
  2012 - 2012
• Dehydration reaction in subducted serpentinite -case study from the Shiragayama mass, Sanbagawa belt-　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Fukumura Seiya
  Annual Meeting of the Geological Society of Japan, 2012, The Geological Society of Japan
  2012 - 2012
• 三波川帯白髪山蛇紋岩体の地質学および岩石学　　　　　　　　　　　　　　　
  岡本和明
  2012
  2012 - 2012
• Fluid chemistry in the major listric fault of the collision zone –fluid inclusion chemistry from the Lishan fault, Taiwan-　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Iijima Chihiro; Kurosawa Masanori; Chan Yu Chang; Terabayashi Masaru
  Abstracts for Annual Meeting of Japan Association of Mineralogical Sciences, 2011, Japan Association of Mineralogical Sciences
  2011 - 2011, Japanese
  We have detected that injected fluid in link thrust would cause fault propagation and fault lubrication due to vapor-separation from the fluid from the great link-thrust, Lishan fault, in Taiwan orogenic belt. In order to measure fluid chemistry, PIXI analysis was done. The result is summarized as follows. 1) Br/Cr ratio is lower than seawater, 2) Ti, Cr, Ni content is signifantly high, suggesting that fluid is related to magma activity beneath, and 3) Vapor-phase inclusion contains considerable amount of metal elements (Ti, Zn, Ge, Mn, Ca, Fe, Pb, Rb, Cu) as well as K, and Br.
• Reconstruction of Paleoclimate using stalagmite on Ishigaki-Island, Japan　　　　　　　　　　　　　　　
  Kayama Yutaka; Sakai Saburou; Okamoto Kazuaki
  Annual Meeting of the Geological Society of Japan, 2011, The Geological Society of Japan
  2011 - 2011, Japanese
• Brittle ductile deformation triggered by fluids separated from melt -Fossil evidence of Arc crustal earthquake preserved in Higo metamorphic rocks-　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Tsuchiya Tomohiko
  Annual Meeting of the Geological Society of Japan, 2010, The Geological Society of Japan
  2010 - 2010, Japanese
• Raman mapping of mineral inclusions in diamond-bearing garnet from Kokchetav UHPM dolomite marble, Kazakhstan　　　　　　　　　　　　　　　
  Terabayashi Masaru; Sato Shuichi; Okamoto Kazuaki; Ozawa Hiroaki
  Annual Meeting of the Geological Society of Japan, 2009, The Geological Society of Japan
  2009 - 2009, Japanese
• Redox state of garnet, clinopyroxene and phlogopite based on Micro-XANES analysis　　　　　　　　　　　　　　　
  OKAMOTO KAZUAKI; TERABAYASHI MASARU
  Annual Meeting of the Geological Society of Japan, 2008, The Geological Society of Japan
  2008 - 2008, Japanese
• S-47 Redox state of garnet, clinopyroxene and phlogopite based on Micro-XANES analysis　　　　　　　　　　　　　　　
  OKAMOTO K.; Terabayashi M.
  2008, The Geological Society of Japan
  2008 - 2008, Japanese
  type:text
  rights: 日本地質学会rights: 本文データは学協会の許諾に基づきCiNiiから複製したものであるrelation: IsVersionOf: http://ci.nii.ac.jp/naid/110007060451/
• Micro-XANES 分析に基づく単斜輝石、ガーネット、金雲母の酸化還元状態　　　　　　　　　　　　　　　
  2008
• Micro-XANES 分析に基づく単斜輝石、ガーネット、金雲母の酸化還元状態　　　　　　　　　　　　　　　
  日本地質学会第115学術大会講演要旨, 2008
• Formation and Exhumation process of the Sanbagawa metamorphic belt, central Shikoku, Japan　　　　　　　　　　　　　　　
  Aoki Kazumasa; Masago Hideki; Tarabayashi Masaru; Kaneko Yoshiyuki; Okamoto Kazuaki; Yamamoto Hiroshi; Ota Tsutomu; Maruyama Shigenori
  Annual Meeting of the Geological Society of Japan, 2007, The Geological Society of Japan
  2007 - 2007, Japanese
• S-58 Fossil fluid reservoir beneath a duplex structure in Taiwan　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Chan Yu-Chang
  2007, The Geological Society of Japan
  2007 - 2007, Japanese
  type:text
  rights: 日本地質学会rights: 本文データは学協会の許諾に基づきCiNiiから複製したものであるrelation: IsVersionOf: http://ci.nii.ac.jp/naid/110006435178/
• 台湾付加体構造下の過去の地殻滞留流体　　　　　　　　　　　　　　　
  2007
• 台湾付加体構造下の過去の地殻滞留流体　　　　　　　　　　　　　　　
  日本地質学会第114学術大会講演要旨, 2007
• O-190 Volatile transfer and recycling at UHP metamorphism; constraint from CCSD (Chinese Continental Scientific Drilling) eclogites　　　　　　　　　　　　　　　
  Okamoto K.; Iizuka Y.; Jahn B.; Yui T.F.; Akasaka Masahide; Xu ZhiQin
  Annual Meeting of the Geological Society of Japan, 2006, The Geological Society of Japan
  2006 - 2006, English
• P-6 Water transportation from the subducting slab into the mantle transition zone　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Maruyama Shigenori
  Annual Meeting of the Geological Society of Japan, 2006, The Geological Society of Japan
  2006 - 2006, English
• Fossil fluid reservoir beneath a duplex fault structure within the Central Range of Taiwan　　　　　　　　　　　　　　　
  Okamoto K.; Chan Yu-Chang; Yui Tzen-Fu; Iizuka Yoshiyuki; Chu Hao-Tsu
  Annual Meeting of the Geological Society of Japan, 2005, The Geological Society of Japan
  2005 - 2005, Japanese
• O-268 Subsolidus phase relations in the MORB+H_2O system up to 20 GPa　　　　　　　　　　　　　　　
  Okamoto K.; Maruyama S.
  Annual Meeting of the Geological Society of Japan, 2000, The Geological Society of Japan
  2000 - 2000, Japanese
• Petrology of the diamond-grade eclogite in the Kokchetav massif, northern Kazakhstan　　　　　　　　　　　　　　　
  Okamoto K.; Katayama I.; Maruyama S.; Liou J. G.
  Annual Meeting of the Geological Society of Japan, 1999, The Geological Society of Japan
  1999 - 1999, Japanese
• Supersilicic clinopyroxene in the Kokchetav UHPM rocks.　　　　　　　　　　　　　　　
  Katayama I.; Okamoto K.; Parkinson C. D.; Nakajima Y.
  Annual Meeting of the Geological Society of Japan, 1999, The Geological Society of Japan
  1999 - 1999, Japanese
• 三波川変成帯石英エクロジャイトのSHRIMP II U-Pbジルコン年代　　　　　　　　　　　　　　　
  岡本和明
  1999
  1999 - 1999
• Eclogite-Garnetite transformation in the MORB+H₂O system　　　　　　　　　　　　　　　
  OKAMOTO Kazuaki; MARUYAMA Shigenori
  Annual Meeting of the Geological Society of Japan, 1998, The Geological Society of Japan
  1998 - 1998, Japanese
• New observation on the earth by plume tectonics.Carry the ocean water to mantle.　　　　　　　　　　　　　　　
  岡本和明; 丸山茂徳; SCHMIDT M
  科学, Jul. 1997
  Jul. 1997 - Jul. 1997, Japanese
• 197 On-going Orogeny (1) : Tectonic evolution of the Timor-Tanimbar metamorphic belt,Eastern Indonesia　　　　　　　　　　　　　　　
  Kaneko Yoshiyuki; Maruyama Shigenori; Ota Tsutomu; Kadarusman Ade; Tsujimori Tatsuki; Okamoto Kazuaki
  Annual Meeting of the Geological Society of Japan, 1997, The Geological Society of Japan
  1997 - 1997, Japanese
• 198 On-going Orogeny (2) : Lithology and metamorphism of the eastern and western parts of the Timor-Tanimbar metamorphic belt,Eastern Indonesia　　　　　　　　　　　　　　　
  Ota Tsutomu; Tsujimori Tatsuki; Kaneko Yoshiyuki; Kadarusman Ade; Okamoto Kazuaki; Maruyama Shigenori
  Annual Meeting of the Geological Society of Japan, 1997, The Geological Society of Japan
  1997 - 1997, Japanese
• 211 The high pressure stability limit of lawsonite eclogite　　　　　　　　　　　　　　　
  OKAMOTO Kazuaki; MARUYAMA Shigenori
  Annual Meeting of the Geological Society of Japan, 1997, The Geological Society of Japan
  1997 - 1997, Japanese
• 429 Experimental study of the Dabie UHP eclogite formed at diamond grade, central China　　　　　　　　　　　　　　　
  OKAMOTO Kazuaki; MARUYAMA Shigenori
  Annual Meeting of the Geological Society of Japan, 1996, The Geological Society of Japan
  1996 - 1996, Japanese
• 367. Metasomatic process deduced from trace element geochemistry of the subducted oceanic crust(high P/T metamorphic rocks)　　　　　　　　　　　　　　　
  OKAMOTO Kazuaki; MARUYAMA Shienori
  Annual Meeting of the Geological Society of Japan, 1995, The Geological Society of Japan
  1995 - 1995, Japanese
• 236. Accretionary complex origin of the Sanbagawa,high P/T metamorphic rocks,Central Shikoku,Japan.　　　　　　　　　　　　　　　
  OKAMOTO K; MARUYAMA S; ISOZAKI Y
  Annual Meeting of the Geological Society of Japan, 1994, 一般社団法人 日本地質学会
  1994 - 1994, Japanese
• 251. Relation between the MTL and N-ward (upward) shear strain gradient developed in the Sambagawa belt during its exhumation.　　　　　　　　　　　　　　　
  OKamoto K.
  Annual Meeting of the Geological Society of Japan, 1993, The Geological Society of Japan
  1993 - 1993, Japanese
• 347 Strain process of recumbent folding and configuration of Stress - Strain axis of S-C mylonite : Sambagawa belt, Besshi district　　　　　　　　　　　　　　　
  Okamoto Kazuaki
  Annual Meeting of the Geological Society of Japan, 1992, The Geological Society of Japan
  1992 - 1992, Japanese
• 312 Structural analysis of the sambagawa belt in the Besshi district, Shikoku II　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Hara Ikuo; Shiota Tsugio; Hide Kei
  Annual Meeting of the Geological Society of Japan, 1991, The Geological Society of Japan
  1991 - 1991, Japanese
• 283 Quartz fabrics observed on P-T path of the Sambagawa metamorphic rocks of Central Shikoku　　　　　　　　　　　　　　　
  Sakakibara N.; Hara I.; Kaikiri K.; Okamoto K.; Shiota T.; Hide K.
  Annual Meeting of the Geological Society of Japan, 1991, The Geological Society of Japan
  1991 - 1991, Japanese
• 311 Strain picture variation in folding history of the Sambagawa belt. Central Shikoku　　　　　　　　　　　　　　　
  Kaikiri K.; Hara I.; Shiota T.; Okamoto K.; Hide K.
  Annual Meeting of the Geological Society of Japan, 1991, The Geological Society of Japan
  1991 - 1991, Japanese
• 330 Structural analysis of the Sogauchi nappe of the Sambagawa belt in central Shikoku　　　　　　　　　　　　　　　
  Okamoto Kazuaki; Hara Ikuo; Hide Kei; Shiota Tsugio
  Annual Meeting of the Geological Society of Japan, 1990, The Geological Society of Japan
  1990 - 1990, Japanese
• Structural analysis of the Sambagawa belt in the Basshi district, central Shikoku　　　　　　　　　　　　　　　
  Okamoto K.; Hara I.; Shiota T.; Hide K.
  Annual Meeting of the Geological Society of Japan, 1989, The Geological Society of Japan
  1989 - 1989, Japanese
• 282 Quartz fabrics of siliceous schists in the Sambagawa Belt of Central Shikoku　　　　　　　　　　　　　　　
  OKAMOTO K.; HARA I.; SHIOTA T.; HAYASAKA Y.
  Annual Meeting of the Geological Society of Japan, 1988, The Geological Society of Japan
  1988 - 1988, Japanese

• Mineralogical Society of America
• Geological Society of America
• American Geophysical Union

• Origin and chemistry of geofluids　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), 23 Jul. 2009 - 31 Mar. 2014
  KOGISO Tetsu; HIRAJIMA Takao; TAKAHASHI Eiichi; OKAMOTO Kazuaki; YAMAZAKI Daisuke; KAWAMOTO Tatsuhiko; OMORI Soichi; MATSUKAGE Kyoko; KATSURA Tomoo; NOGUCHI Naoki; OHI Shugo; BUREAU Hélène, Kyoto University
  Grant amount(Total)：158860000, Direct funding：122200000, Indirect funding：36660000
  In order to understand the chemical characteristics of aqueous fluids generated in subduction zones, and to know the role of such fluids in subduction zone phenomena, we have conducted in-situ chemical analyses of experimentally produced aqueous fluids and petrological investigations of natural metamorphic rocks. Through these researches, we have revealed that high-salinity fluids are being generated in subduction zones by metamorphic processes, and that those high-salinity fluids play critical roles in causing magmatism in volcanic arcs as well as seismic activities in subducting plate.
  Grant number：21109004
• State analysis of micro area of omphacite inclusions within garnet from eclogite　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 2010 - 2012
  TERABAYASHI Masaru; OKAMOTO Kazuaki, Kagawa University
  Grant amount(Total)：4420000, Direct funding：3400000, Indirect funding：1020000
  We have verified that Raman spectrums are useful as an indicator for the redox state of iron in omphacite included within garnet from eclogites. Eclogites from ultrahigh-pressure metamorphic belts often show symplectitic aggregate or lamellae composed of quartz needles. They are hardly observed in omphacite included within garnet or zircon, those are considered to have avoided the influence of retrograde metamorphism. Another problem in temperature estimation using geothermometer is the determination of Fe3+content in clinopyroxene. Mossbauer spectroscopy and micro-XANES (X-ray absorption near edge structure) in photon factory are effective for the measurement of the Fe3+/Fe2+ratio. In the former, mineral separation is necessary and it takes more than one day to collect spectra from one sample, but in situ analysis at the micron size is possible and it takes less than 2h to collect spectra in the latter except limited facilities.
  Grant number：22540493
• A project which gives surprise and impression and makes science favorite in order to prevent dislike of science.　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 2009 - 2012
  ASHIDA Minoru; OHMUKAI Ryuzo; HIBINO Taku; OKAMOTO Kazuaki; SHIMIZU Makoto; KATAHIRA Katsuhiro; YATSUKA Mitsunori; ASHIDA Masami, Saitama University
  Grant amount(Total)：19240000, Direct funding：14800000, Indirect funding：4440000
  Various enterprises were undertaken in order to prevent dislike of science. The students were dispatched to elementary schools as a helper. They were engaged in arrangement of a science laboratory and assistance of a lesson. The students were dispatched to the event of a science museum, the studying classroom in Misato, the contact enterprise of Kawagoe, etc. In the observation experiment classroom, we gave children various surprise and impression at elementary schools, etc. Moreover, astronomical observation meetings and workshops were held. We replied to many questions by the homepage and exhibited how to make solutions, simulation of experiments and science calendars.
  Grant number：21300288
• Dehydration and melting process in deep subduction zone-Zircon geochemistry from the Sanbagawa eclogite-　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), 2009 - 2011
  OKAMOTO Kazuaki; TERABAYASHI Masaru, Saitama University
  Grant amount(Total)：4420000, Direct funding：3400000, Indirect funding：1020000
  Partial melting texture was discovered from the Sanbagawa eclogoite which had been subducted down to upper mantle at Cretaceous time. Zircons were separated from the eclogite. The zircons exhibit sector zoning on the core to mantle under the CL images. SHRIMP U-Pb age dating and REE analysis from the zircons indicate that the partial melting had occurred in the case of young (hot) slab at upper mantle depth. The melting reaction was due to phengite decomposition. The zircon and the garnet were grown together in the presence of melt.
  Grant number：21540468
• Fluid-rock interaction deduced from geological time bright-layer in the middle crust　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 2007 - 2009
  TERABAYASHI Masaru; YAMAMOTO Hiroshi; OKAMOTO Kazuaki; HAFIZ Ur rehman; YOSHIDA Hidenori, Kagawa University
  Grant amount(Total)：16250000, Direct funding：12500000, Indirect funding：3750000
  The geological time bright-layer was recognized in the low-P/T metamorphic rocks. We found that silicified rocks distribute as layers or lenticular bodies, and they are restricted in the greenscist facies conditions within structurally vertical thickness. Quartz veins crossing high-angles with schistosity were preferentially developed. The mode of occurrences of quartz veins indicates that silicified rocks are competent relative to underlying rocks. Rock boundary with high competence contrast is probably a good reflector of seismic waves. Seismic bright-layer reflections in the middle crust would be arisen from observed silicified rock layers in this study, if those are distributed in the deep crust to a considerable extent.
  Grant number：19340152
• 地球深部　　　　　　　　　　　　　　　
  Competitive research funding
• Deep interior of the Earth　　　　　　　　　　　　　　　
  Competitive research funding