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Origin of Neoproterozoic anorthosites in the Wadi El Dib ultramafic-mafic layered intrusions, Egypt

Eliwa, HA; Deevsalar, R; Mahdy, NM; Pan, Y; El-Gameel, K; El-Desouky, HA; Khamis, H; Murata, M; Andresen, A; Chew, D; El Sundolly, H; Fawzy, MM; Kato, Y; Fujinaga, K; Shin, KC; Shinjo, R

PRECAMBRIAN RESEARCH ( Precambrian Research ) 421 107750 - 107750 2025年06月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Coral Decline Linked to Exchangeable Phosphate in Seawater from Coastal Calcareous Sediments, as Evidenced in Sekisei Lagoon, Japan

Yasumoto, J; Iijima, M; Iguchi, A; Nakamura, T; Takada, R; Yasumoto-Hirose, M; Iwasaki, Y; Yasutaka, T; Mori-Yasumoto, K; Shinjo, R; Ide, R; Yamazaki, A; Mizusawa, N; Ohno, Y; Suzuki, A; Watabe, S; Yasumoto, K

MARINE BIOTECHNOLOGY ( Marine Biotechnology ) 27 ( 2 ) 50 2025年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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1924年西表海底火山噴火由来軽石層の発見

宇佐美賢, 加藤祐三, 新城竜一, 新山颯大

沖縄県立博物館・美術館，博物館紀要 ( 18 ) 1 - 8 2025年03月

掲載種別: 研究論文（大学，研究機関紀要）

Geochemistry of late Miocene-Pleistocene basalts from a coastal area of Vietnam: Implication for small-scale mantle heterogeneities

Nguyen Hoang, Tran Thi Huong, Ryuichi Shinjo, Le Duc Anh, Le Duc Luong, Phan Dong Pha

Journal of Asian Earth Sciences ( Elsevier BV ) 281 106488 - 106488 2025年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Pleistocene basaltic volcanism in the southeastern Ailao Shan - Red River Shear zone: Implications for the injection of metasomatized asthenospheric mantle under the region

Hoang Nguyen, Ryuichi Shinjo, Luong Le Duc, Huong Tran Thi, Anh Tran Viet, Pha Phan Dong, Dang Pham Thanh, Thang Cu Sy, Thu Nguyen Thi, Dung Le Thi Phuong

Vietnam Journal of Earth Sciences ( Publishing House for Science and Technology, Vietnam Academy of Science and Technology (Publications) ) 47 16 - 43 2024年09月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

The Lung Po basalt, dating to 0.93, 0.81, and 0.47 Ma, occupies approximately 1 km² and is situated 12 km west of the Ailao Shan Red River Shear Zone (ASRRSZ) and about 65 km south of the 12-0 Ma Maguan intraplate volcanic area in southwest Yunnan (SW China), within the ASRRSZ. This olivine-bearing phyric alkaline basalt is characterized by high TiO₂ (around 2.3 wt.%), MgO (8-10 wt.%), and K₂O (approximately 2.8-3 wt.%) with Na₂O/K₂O ratios ranging from 1 to 1.2. These features partially overlap with the Maguan mantle xenolith-bearing alkaline basalt but are distinct from the Pleistocene alkaline basalt of Vietnam's Western Highlands. The Lung Po basalts exhibit a typical oceanic island basalt (OIB) trace element distribution pattern and a 'crossing' rare earth element (REE) pattern, indicating magma generation possibly by melting of garnet peridotite. They have high ⁸⁷Sr/⁸⁶Sr isotopic ratios (around 0.706) and low ¹⁴³Nd/¹⁴⁴Nd ratios (approximately 0.5126), along with moderate ²⁰⁶Pb/²⁰⁴Pb and ¹⁷⁶Hf/¹⁷⁷Hf isotopic ratios (respectively <18.3-18.4 and 0.28295-0.2830). These isotopic characteristics, coupled with OIB trace element features, challenge the involvement of crustal material. The Lung Po Pleistocene basalt and the 12-0 Ma Maguan alkaline basalt differ significantly from the 42-24 Ma post-collision high-K magmas in the ASRRSZ, which are associated with crustal tectonic processes. Instead, the Lung Po (and Maguan) basalt likely originated from a newly emplaced, metasomatically altered fertile asthenosphere following localized lithosphere extension and delamination after the India-Eurasian collision events.

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Reply to discussion of "An assessment of small Island hydrological research activity conducted in the Oceania Region"1

Leong, C; Solomone, M; Shinjo, R; Tomojiri, D; Uchiyama, C; Yasumoto, J; Razafindrabe, B

HYDROLOGICAL SCIENCES JOURNAL ( Hydrological Sciences Journal ) 2024年08月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Metagenomic analysis of the microbial communities and associated network of nitrogen metabolism genes in the Ryukyu limestone aquifer

Maruyama, R; Yasumoto, K; Mizusawa, N; Iijima, M; Yasumoto-Hirose, M; Iguchi, A; Hermawan, OR; Hosono, T; Takada, R; Song, KH; Shinjo, R; Watabe, S; Yasumoto, J

SCIENTIFIC REPORTS ( Scientific Reports ) 14 ( 1 ) 4356 2024年02月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Abstract While microbial biogeochemical activities such as those involving denitrification and sulfate reduction have been considered to play important roles in material cycling in various aquatic ecosystems, our current understanding of the microbial community in groundwater ecosystems is remarkably insufficient. To assess the groundwater in the Ryukyu limestone aquifer of Okinawa Island, which is located in the southernmost region of Japan, we performed metagenomic analysis on the microbial communities at the three sites and screened for functional genes associated with nitrogen metabolism. 16S rRNA amplicon analysis showed that bacteria accounted for 94–98% of the microbial communities, which included archaea at all three sites. The bacterial communities associated with nitrogen metabolism shifted by month at each site, indicating that this metabolism was accomplished by the bacterial community as a whole. Interestingly, site 3 contained much higher levels of the denitrification genes such as narG and napA than the other two sites. This site was thought to have undergone denitrification that was driven by high quantities of dissolved organic carbon (DOC). In contrast, site 2 was characterized by a high nitrate-nitrogen (NO3-N) content and a low amount of DOC, and this site yielded a moderate amount of denitrification genes. Site 1 showed markedly low amounts of all nitrogen metabolism genes. Overall, nitrogen metabolism in the Ryukyu limestone aquifer was found to change based on environmental factors.

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Mechanism of denitrification in subsurface-dammed Ryukyu limestone aquifer, southern Okinawa Island, Japan

Hermawan, OR; Hosono, T; Yasumoto, J; Yasumoto, K; Song, KH; Maruyama, R; Iijima, M; Yasumoto-Hirose, M; Takada, R; Hijikawa, K; Shinjo, R

SCIENCE OF THE TOTAL ENVIRONMENT ( Science of the Total Environment ) 912 169457 - 169457 2024年02月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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下北半島中部で掘削されたSN-010深部ボーリングコア中の中新統泊火山岩類の岩石記載と層序対比

相澤正隆, 稲葉充, 岡村聡, 新城竜一

地質学雑誌 ( 一般社団法人日本地質学会 ) 129 ( 1 ) 587 - 602 2023年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

青森県下北半島東部に分布する泊火山岩類は，東北日本弧の中期中新世の火山フロントを構成していた火山岩層である．火山活動は4つのステージに分けられており，第Iステージの地質体は金津山安山岩，第IIステージの地質体は下部が月山安山岩，上部が泊玄武岩，第IIIステージの地質体は鷹架安山岩，第IV ステージの地質体は吹越安山岩と呼ばれる．このうち，泊玄武岩はかんらん石に富みクロムスピネルも含むことで特徴づけられる．2014～2016 年にかけて泊層の西隣でボーリング調査が行われ，得られたコアの 308 m 以深に泊火山岩類が産出した．本研究による岩石学的検討により，コアの深度約1003 m 前後の溶岩が泊玄武岩に対比された．全岩化学組成は浅部コア試料と地表の泊層で類似する一方，深部コア試料はより高いLIL/HFS 元素比を有することから，本層の活動中にスラブ由来流体の組成が変化した可能性が示唆される．

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環境水のホウ素同位体分析のための簡易分離方法の開発—認証標準物質のホウ素同位体組成の初報告—

宋科翰, 新城竜一, 諸見里結美

環境科学会誌 ( 社団法人環境科学会 ) 36 ( 6 ) 211 - 217 2023年11月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

ホウ素同位体は，河川水や地下水中の汚染物質の定量的評価など，環境問題の解決に有効なトレーサーである。同位体分析の正確度を評価するためには，マトリックスが類似し値付けされた標準物質（RM）が必要である。しかし，ホウ素濃度の保証値はあるものの，同位体組成が既知の標準物質はまだ少ない。今回，河川水（NMIJ CRM 7202-c, JSAC 0301-4a）および水道水（NMIJ CRM 7203-a）の日本産認証標準物質（CRM）のホウ素同位体組成を初めて報告する。あわせて，0.1 mLの陽イオン交換樹脂カラムのみを用いた，環境水からのホウ素の簡便な分離法も開発した。この方法は煩雑な分離を簡略化したもので，ホウ素の回収率は97％以上，マトリックス元素の分離効率は98％以上である。δ11B値は7202-cが−8.81±0.19‰，0301-4aが14.33±0.49‰，7203-aが17.86±0.28‰である。また，応用例として市販されている4種類のペットボトル水（富士山，六甲，阿蘇山，久米島）を分析した。報告した分離方法は，簡便かつ短時間での処理であり，ブランクレベルも低く，ホウ素の測定効率を向上させることができる。

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An assessment of small island hydrological research activity conducted in the Oceania Region

Leong, C; Solomone, M; Shinjo, R; Tomojiri, D; Uchiyama, C; Yasumoto, J; Razafindrabe, B

HYDROLOGICAL SCIENCES JOURNAL ( Hydrological Sciences Journal ) 68 ( 14 ) 2105 - 2120 2023年10月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Assessing the activity of mud volcanism using boron isotope ratios in pore water from surface sediments of mud volcanoes off Tanegashima (SW Japan)

Mitsutome, Y; Agena, K; Toki, T; Song, KH; Shinjo, R; Ijiri, A

FRONTIERS IN MARINE SCIENCE ( Frontiers in Marine Science ) 10 2023年09月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Mud volcanoes can cause various geohazards, so it is very important to know their activity level and their distribution. Surface sediments were collected from four submarine mud volcanoes (MVs) off Tanegashima (SW Japan), namely, MV1, MV2, MV3, and MV14. We extracted pore water from the surface sediments and investigated its chemical and isotopic compositions. The sodium (Na) and chloride (Cl-) concentrations decreased and the boron (B) and lithium (Li) concentrations increased with increasing depth, suggesting that some fluids with lower Na and Cl- concentrations and higher B and Li concentrations than seawater were supplied upward from the deep sub-seafloor. The fluid advection velocities estimated from the pore-water profiles differed for each MV, and those of MV3 were the fastest (14 cm/yr) in this study. The estimated equilibrium temperature with clay minerals using Na and Li concentrations were 93-134°C, corresponding to the temperature of environments around 3.7 to 5.3 km below the seafloor. This indicates that these components originated from these depths and that the origin depth did not reach the plate boundary in this area. The B isotope ratio in the pore water was extremely high up to +57 ‰, suggesting that it was strongly affected by adsorption onto the surface of the sediments. A higher B isotope ratio (+57 ‰) was detected in MV3, which was considered to be more active, indicating that more B was adsorbed onto clay minerals supplied from deeper depths.

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Petrogenetic and geodynamic evolution of plutonic rocks from the Chadormalu district, Kashmar-Kerman tectonic zone, Central Iran

Nayebi, N; Esmaeily, D; Shinjo, R; Deevsalar, R; Modabberi, S; Lehmann, B

MINERALOGY AND PETROLOGY ( Mineralogy and Petrology ) 117 ( 4 ) 619 - 637 2023年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Effective use of farmland soil samples for N and O isotopic source fingerprinting of groundwater nitrate contamination in the subsurface dammed limestone aquifer, Southern Okinawa Island, Japan

Hermawan O.R.

Journal of Hydrology ( Journal of Hydrology ) 619 129364 - 129364 2023年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Geology and geochemistry of metasomatite rocks associated with Kiruna iron oxide apatite and the evolution of fluids responsible for metasomatism in Choghart and Chadormalu deposits (Bafq mining district, Central Iran)

Somayeh Teimouri, Mansour Ghorbani, Ryuichi Shinjo, Soroush Modabberi

Arabian Journal of Geosciences ( Springer Science and Business Media LLC ) 16 ( 4 ) 2023年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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μ-XRFを用いた福徳岡ノ場の軽石の簡易元素分析手法の開発および地球科学的考察

中野ひとみ, 新城竜一, 駒谷慎太郎

Ｘ線分析の進歩 54 203 - 216 2023年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Zircon U–Pb ages and Sr–Nd–Pb–Hf isotopic compositions constrain the tectono-magmatic evolution of the Anomaly 21-A iron ore region, Bafq metallogenic province, Central Iran

Nayebi N.

Journal of Asian Earth Sciences ( Journal of Asian Earth Sciences ) 250 105646 - 105646 2023年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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福徳岡ノ場2021年噴火起源軽石の漂着量とサイズの時間変化：神奈川県天神島の例

柴田健一郎, 小長谷美沙, 新城竜一

横須賀市博研報 (自然) ( 70 ) 39 - 51 2023年03月

掲載種別: 研究論文（大学，研究機関紀要）

慶良間諸島に分布する四万十帯の砂岩の産状および砕屑性ジルコンの年代測定の試み

宇佐美賢, 宮城宏之, 仲村渠聖也, 宋科翰, 高橋凪, 新城竜一

沖縄県立博物館・美術館, 博物館紀要 ( 16 ) 1 - 11 2023年03月

掲載種別: 研究論文（その他学術会議資料等）

Effect of groundwater residence time on geogenic fluoride release into groundwater in the Mt. Meru slope area, Tanzania, the Great Rift Valley, East Africa.

Nakaya S, Takada R, Yasumoto J, Masuda H, Yoshitani J, Shinjo R, Lugodisha I, Komakech H

Journal of contaminant hydrology ( Elsevier BV ) 253 104125 - 104125 2023年02月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Mixed carbonate-siliceous hydrothermal chimneys ahead of the Asal propagating rift (SE Afar Rift, Republic of Djibouti)

Moussa N.

Journal of African Earth Sciences ( Journal of African Earth Sciences ) 197 104765 - 104765 2023年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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The geochemical gas field in surface sediments in the Southwest sub-basin of East Vietnam Sea: distribution, origin, and comparative features with other regions of Western East Vietnam Sea

Duc Luong Le, Hoang Nguyen, Anatoly Obzhirov, Ryuichi Shinjo, Renat B. Shakirov

Vietnam Journal of Marine Science and Technology ( Publishing House for Science and Technology, Vietnam Academy of Science and Technology (Publications) ) 22 ( 4 ) 337 - 362 2022年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

We analyzed 39 gas samples, including carbon dioxide, hydrocarbon gases C1–C4, hydrogen, and helium, in surface sediment from 19 gravity cores collected from the SW sub-basin of the East Vietnam Sea (EVS) using the headspace and vacuum degassing methods. Based on the result, we discussed the distribution and origin of gases in the southwest sub-basin EVS surface sediments. The sediments are mostly clay and silty clay containing methane ranging from 0.5–440 ppm. The anomalous concentrations of methane, helium, and hydrogen occur along the continental slope in the Nam Con Son basin of Southwest EVS. Methane is the dominant gas compared to other detected hydrocarbon gases, including ethylene, propane, and butane. Based on comparative results, the background methane concentrations in surface sediments decrease from South to North, from the southwestern sub-basin of the East Vietnam Sea to the Phu Khanh and the Red river basins. We propose the presence of a large-scale degassing zone of hydrocarbon gases and discuss the gases’ origin in surface sediments based on hydrocarbon gas ratios, carbon isotope compositions of carbon dioxide and methane, and the relationship between geochemical characteristics of surface sediments and fault system, and surface sediment gases.

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Redox evolution of differentiating hydrous basaltic magmas recorded by zircon and apatites in mafic cumulates: The case of the Malayer Plutonic Complex, Western Iran

Deevsalar R.

Geochemistry ( Geochemistry ) 83 ( 1 ) 125946 - 125946 2022年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Development and Application of an Environmental Education Tool (Board Game) for Teaching Integrated Resource Management of the Water Cycle on Coral Reef Islands

Shimabukuro M.

Sustainability (Switzerland) ( Sustainability (Switzerland) ) 14 ( 24 ) 16562 - 16562 2022年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

To solve resource issues on coral reef islands, an understanding of the water cycle is essential. Water resource management is intricately linked to diverse occupational industries and coral reef ecosystems on these islands. To effectively promote sustainable natural resource management, we developed a board game as an environmental education and communication tool for school students and people of all ages. The concept of the game is that “clean water will always be available if it is used properly”. The board game was designed based on an island with an underground freshwater lens as its main water resource. Role-playing was used to enhance islander livelihoods such as with vegetable and livestock farming, fishing, and tourism. Players, while working collaboratively, have to use the island’s groundwater adequately and conserve it for future generations. The game was developed through a transdisciplinary process in collaboration with scientists, administrative officers, civic groups, and students. Additionally, the board game was tested in diverse communities. In this study, we elaborated on the board game after it was played by students at an elementary school on Tarama Island. We observed that participants learned that cooperation is important for the sustainable use of water resources. Moreover, the participants proposed two methods for cooperation: joint discussion and ‘assembly decisions’. The board game has the potential to be used as an effective environmental education tool to promote sustainable water resource management on coral reef islands.

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鉛同位体比による近世〜近代日本で流通した銃弾鉛の原産地推定

相澤正隆, 溝田智俊, 細野高啓, 新城竜一

金属 92 ( 11 ) 62 - 78 2022年11月

掲載種別: 研究論文（その他学術会議資料等）

Sr isotopic ratios of hydrothermal fluids from the Okinawa Trough and the implications of variation in fluid–sediment interactions

Toki, T, Nohara, T, Urata, Y, Shinjo, R, Hokakubo-Watanabe, S, Ishibashi, J, Kawagucci, S

Progress in Earth and Planetary Science ( Progress in Earth and Planetary Science ) 9 ( 59 ) 2022年10月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Abstract Sr isotope ratios of hydrothermal fluids were observed at five sediment-associated sites in the Okinawa Trough to investigate the diversity of subseafloor fluid–rock–sediment interactions. The estimated 87Sr/86Sr ratios of the hydrothermal endmember fluids at the five sites were all higher than those at the sediment-starved sites. The endmember Sr isotopic ratios of hydrothermal fluids were diverse within the Okinawa Trough, ranging from 0.7077 at the Iheya North Knoll site to 0.712 at the Yonaguni Knoll IV site. To our knowledge, 0.712 is the highest value reported to date for seafloor hydrothermal fluids. This variation is likely attributable to the relative contributions of multiple subseafloor Sr reservoirs, which are 87Sr-poor volcanic rock and 87Sr-rich hemipelagic sediments containing clay minerals of terrestrial origin. These data support a model based on the carbon isotope ratio of CH4, which indicates whether volcanic rocks or terrestrial sediments are distributed in the high-temperature reaction zone of the hydrothermal system.

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Geochemical and geochronological constraints on origin of the Sawlava ophiolite (NW Iran): Evidence for oceanic mantle evolution beneath Iran-Iraq border

Ghorbani M.R.

Lithos ( Lithos ) 418-419 106695 - 106695 2022年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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福徳岡ノ場2021年8月噴火による沖縄県における漂着軽石の記録

宇佐美賢, 新城竜一

沖縄県立博物館・美術館, 博物館紀要 ( 15 ) 1 - 16 2022年03月

掲載種別: 研究論文（大学，研究機関紀要）

THE ORIGIN OF GEM SPODUMENE IN THE HAMADAN PEGMATITE, ALVAND PLUTONIC COMPLEX, WESTERN IRAN

Gheshlaghi, RS; Ghorbani, M; Sepahi, AA; Deevsalar, R; Nakashima, K; Shinjo, R

CANADIAN MINERALOGIST ( Canadian Mineralogist ) 60 ( 2 ) 249 - 266 2022年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

ABSTRACT Pegmatite bodies with a simple mineral composition are widespread within the Sanandaj-Sirjan Zone (SaSiZ), Zagros Orogen, Iran; however, gem-bearing pegmatite bodies are rare. There is a pegmatitic vein within the Hamadan garnet (± andalusite ± staurolite) schist adjacent to the Alvand Plutonic Complex (APC), south of Hamedan city (western Iran), in which large crystals of gem spodumene occur together with quartz, amazonite, beryl, tourmaline, and apatite. This spodumene-bearing pegmatite consists of four major zones with slightly different mineral compositions from the border to the core. The wall zone of quartz-rich granitoid and the intermediate zone of alkali granite have trondhjemitic compositions near the quartzolitic gem-bearing core zone. All parts of the vein are peraluminous in composition and exhibit S-type affinity. Two types of spodumene which have been distinguished in the core zone are colorless to very pale yellow and pink, transparent with vitreous luster and inclusion-free (eye clean) under 10× magnification. The different color in these minerals can be attributed to the slightly different chemical compositions, particularly lower Fe/Mn ratios in the pink material. The δ7Li values of the spodumene (+5.58 to +6.57‰) are indicative of the incorporation of middle continental crustal components in their genesis. Change in the mineral assemblage from tourmaline-bearing in the intermediate zone to spodumene + tourmaline in the core zone of the spodumene-bearing pegmatite is consistent with increasing lithium content from the wall zone to the core. Petrographic, geochemical, and isotopic data indicate that partial melting of middle-crustal Al-rich metapelitic source was followed by fractional crystallization to generate these rocks. In this concern, the required Li for the crystallization of spodumene was probably supplied by the breakdown of staurolite of the Hamadan schist and/or subsequent fractional crystallization of the parent magma. The results also demonstrate that the regional tectonic regime exerts a primary control on the occurrence and emplacement of the miarolitic pegmatite in the upper crust and the formation of gem spodumene during late-stage magmatic activities.

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Lead isotopic characteristics of gun bullets prevailed during the 19th century in Japan: Constraints on the provenance of lead source from the United Kingdom and Japan

Aizawa M.

Journal of Archaeological Science: Reports ( Journal of Archaeological Science: Reports ) 41 103268 - 103268 2022年02月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Provenancing Nineteenth Century Saltpetre From British India Using Nitrogen, Oxygen, and Strontium Isotope Ratios

Chitoshi Mizota, Robin Hansen, Takahiro Hosono, Azusa Okumura, Ryuichi Shinjo, Masataka Aizawa

Collections: A Journal for Museum and Archives Professionals ( SAGE Publications ) 18 ( 2 ) 155019062110729 - 155019062110729 2022年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Highly purified specimen of saltpetre, kept in two glass jars are stored in the collections of the Natural History Museum, London, United Kingdom. Historic catalogs of the specimen collection record their acquisition date as 17th March, 1881. The specimen represent heritage of the saltpetre industry during the times of the colonial British India. Chemical analysis shows that they are highly refined, containing only traces of impurities. Dual isotopic composition (δ15N and δ18O) of nitrate implies their intrinsic origin as British India. In addition, relative to highly radiogenic signature of Sr widespread throughout India, less radiogenic strontium (87Sr/86Sr = 0.707859–0.714168) in the specimens suggests that final stages of the refining took place in western India where relevant waters containing pristine Sr were used. Stable isotope geochemistry in combination with history and socio-economy provide new insights into this research area which is not yet fully understood.

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Geochemistry and petrogenesis of intrusive rocks of Chadormalu deposit; an implication on whole-rock geochemistry and Sr-Nd-Pb isotopes

Nayebi, N, Esmaeily, D, Modabberi, S, Shinjo, R, Deevsalar, R, Lehmann, B

Scientific Quarterly Journal of Geosciences 32 29 - 42 2022年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Mantle geodynamics and source domain of the East Vietnam Sea opening- induced volcanism in Vietnam and neighboring regions

Hoang Nguyen, Ryuichi Shinjo, Thi Huong Tran, Duc Luong Le, Duc Anh Le

Vietnam Journal of Marine Science and Technology ( Publishing House for Science and Technology, Vietnam Academy of Science and Technology (Publications) ) 21 ( 4 ) 393 - 417 2021年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

The spreading of the East Vietnam Sea (EVS, also known as Bien Dong, or the South China Sea), leading to the occurrence of syn-spreading (33-16 Ma) and post-spreading (< 16 to present) volcanism. Syn-spreading magma making up thick layers of tholeiitic basalt with a geochemical composition close to the refractory and depleted mid-ocean ridge basalt (MORB) is mainly distributed inside the EVS basin. The post-spreading magma is widely distributed inside the basin and extended to South and SE China, Hainan island, Southern Laos (Bolaven), Khorat Plateau (Thailand), and Vietnam, showing the typical intraplate geochemistry. Basaltic samples were collected at many places in Indochina countries, Vietnam’s coastal and continental shelf areas, to analyze for eruption age, petrographical, geochemical, and isotopic composition to understand the similarities and differences in the mantle sources between regions. The results reveal that basalts from some areas show geochemical features suggesting they were derived subsequently by spinel peridotite and garnet peridotite melting, forming high-Si, low-Mg, and low-Ti tholeiitic basalt to low-Si, high-Mg, and high-Ti alkaline basalt with the trace element enrichment increasing over time. Other basalts have geochemical and isotopic characteristics unchanged over a long period. The post-spreading basalt’s radiogenic Sr-Nd-Hf-Pb isotopic compositions show different regional basalts distribute in the various fields regardless of eruption age, suggesting that their mantle source feature is space-dependent. The post-EVS spreading basalts expose the regional heterogeneity, reflecting the mixture of at least three components, including a depleted mantle (DM) represented by the syn-EVS spreading source, similar to the DUPAL-bearing Indian MORB source; an enriched mantle type 1 (EM1), and type 2 (EM2). The DM may interact and acquire either EM1 or EM2 in the sub-continental lithospheric mantle; as a result, different eruption at different area acquires distinct isotopic signature, reflecting the heterogeneous nature of the subcontinental lithospheric mantle. The study proposes a suitable mantle dynamic model that explains the EVS spreading kinematics and induced volcanism following the India - Eurasian collision from the Eocene based on the research outcomes.

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Last glacial temperature reconstructions using coupled isotopic analyses of fossil snails and stalagmites from archaeological caves in Okinawa, Japan.

Asami R, Hondo R, Uemura R, Fujita M, Yamasaki S, Shen CC, Wu CC, Jiang X, Takayanagi H, Shinjo R, Kano A, Iryu Y

Scientific reports ( Scientific Reports ) 11 ( 1 ) 21922 2021年11月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Abstract We applied a new geoarchaeological method with two carbonate archives, which are fossil snails from Sakitari Cave and stalagmites from Gyokusen Cave, on Okinawa Island, Japan, to reconstruct surface air temperature changes over the northwestern Pacific since the last glacial period. Oxygen isotope ratios (δ18O) of modern and fossil freshwater snail shells were determined to infer seasonal temperature variations. The observational and analytical data confirm that δ18O values of fluid inclusion waters in the stalagmite can be regarded as those of spring waters at the sites where snails lived. Our results indicate that the annual mean, summer, and winter air temperatures were lower by 6–7 °C at ca. 23 thousand years ago (ka) and 4–5 °C at ca. 16–13 ka than those of the present day. Our reconstruction implies that surface air cooling was possibly two times greater than that of seawater around the Ryukyu Islands during the Last Glacial Maximum, which potentially enhanced the development of the East Asian summer monsoon during the last deglaciation. Considering the potential uncertainties in the temperature estimations, the climatic interpretations of this study are not necessarily definitive due to the limited number of samples. Nevertheless, our new geoarchaeological approach using coupled δ18O determinations of fossil snails and stalagmite fluid inclusion waters will be useful for reconstructing snapshots of seasonally resolved time series of air temperatures during the Quaternary.

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Chemical, mineralogical, and physicochemical features of surface saline muds from Southwestern sub-basin of the East Vietnam Sea: Implication for new peloids

Luong Le Duc, Hoang Nguyen, Ryuichi Shinjo, Renat B. Shakirov, Anatoly Obzhirov

Vietnam Journal of Earth Sciences ( Publishing House for Science and Technology, Vietnam Academy of Science and Technology (Publications) ) 1 - 13 2021年09月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

This study presents the chemical, mineralogical and physicochemical features of 8 saline mud samples from 8 gravity cores located in the southwestern sub-basin of the East Vietnam Sea. The grain-size analysis of mud samples reveals the amount of clay and silt particles in the ranges of 65.1-89.2% and 9.5-34.2%, respectively and a very low fraction of sand. The analytical results showed that mud samples have high contents of SiO2 (32.79-48.09%), Al2O3 (11.26-13.63%), CaO (3.10-13.93%), Fe2O3 (4.15-9.45%), and low contents of TiO2, MnO, MgO, Na2O, K2O and P2O5. The XRD analysis of mud samples indicated mineral compositions with major minerals of quartz, illite, calcite, chlorite, feldspar, kaolinite, and other minor minerals like halite, smectite, fluorapatite, pyroxene, amphibole. The organic and physicochemical parameters of mud samples were also measured. Potentially toxic elements in mud samples were determined and compared with reference values and the technical standard. This study proposes that saline mud samples from the studied area are potential peloids.

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Reconstruction of ocean environment time series since the late nineteenth century using sclerosponge geochemistry in the northwestern subtropical Pacific

Asami R.

Progress in Earth and Planetary Science ( Progress in Earth and Planetary Science ) 8 ( 1 ) 2021年06月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

<title>Abstract</title>The geochemistry of calcifying marine organisms is an excellent proxy for reconstructing paleoceanographic history, but studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. For this study, we first generated near-annual resolved stable carbon and oxygen isotope (δ13C and δ18O) and element/Ca ratios (Sr/Ca, Ba/Ca, Pb/Ca, U/Ca) time series for 1880–2015 from sclerosponge samples (<italic>Acanthochaetetes wellsi</italic>) collected at Miyako Island and Okinawa Island in the Ryukyu Islands of southwestern Japan. The δ13C records exhibited a typical variation of anthropogenically derived Suess effects, demonstrating that the rates of decrease of –0.0043‰/year before 1960 and – 0.024‰/year after 1960 in the northwestern subtropical Pacific were respectively similar to and about 1.4 times higher than those of the Caribbean Sea in the tropical Atlantic. Spectral analysis of the δ18O time series revealed significant periodicity of approximately 2, 3, 6.5, 7–10, and 20–30 year/cycle, indicating that sea surface conditions in the southern Ryukyu Islands had been dominated by interannual and decadal variations in temperature and seawater δ18O since the late nineteenth century. The Sr/Ca and U/Ca ratios for the species <italic>A. wellsi</italic> (high-Mg calcite) might not be a robust proxy for seawater temperatures, unlike <italic>Astrosclera willeyana</italic> and <italic>Ceratoporella nicholsoni</italic> sclerosponges (aragonite). An evident increasing Pb/Ca trend after 1950 found in the samples is probably attributable to Pb emissions from industrial activities and atmospheric aerosols in eastern Asian countries. The Ba/Ca variations differ greatly among sampling sites, which might be attributable to the respective local environments. This evidence demonstrates that more high-resolution age determinations and geochemical profilings enable delineation of secular variations in ocean environments on annual and interannual timescales. Results of our study suggest that if sclerosponges living in deeper ocean environments are collected, spatial and vertical oceanographic variations for the last several centuries will be reconstructed along with coral proxy records.

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Dynamical spatial model of heavy metals in Kendari bay using Bayesian geographical weighted regression

Mukhsar

Journal of Physics: Conference Series ( Journal of Physics: Conference Series ) 1899 ( 1 ) 2021年05月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Geochemical evidence for “cryptic amphibole fractionation” and lower crust melting for the generation of island arc tholeiitic rocks from northern Fossa Magna, central Japan

Aizawa M.

Lithos ( Lithos ) 386-387 106028 - 106028 2021年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Shimajiri Group equivalent sedimentary rocks dredged from sea knolls off Kume Island, central Ryukyus: Implications for timing and mode of rifting of the middle Okinawa Trough back-arc basin

Kikunaga R.

Island Arc ( Island Arc ) 30 ( 1 ) 2021年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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隠岐諸島に産する後期新生代火山岩類の起源マントルの地球化学的変遷

相澤正隆, 新城竜一, 岡村聡, 平井康裕

日本地質学会学術大会講演要旨 ( 一般社団法人日本地質学会 ) 2021 ( 0 ) 059 2021年

掲載種別: 研究論文（研究会，シンポジウム資料等）

はじめに隠岐諸島には，漸新世～更新世の火山岩類と堆積岩類が分布する。隠岐諸島の後期新生代の火山活動は，中期中新世以前は非アルカリ岩の活動が中心で，後期中新世以降はアルカリ岩の活動が中心となる[1]。本研究では，隠岐諸島に分布する後期漸新世以降の火山岩類について岩石学的検討を行い，日本海拡大の直前に活動していた火山岩の起源マントル，日本海拡大を引き起こしたアセノスフェアマントル，および日本海拡大後のアルカリ岩類の起源マントルの地球化学的組成の時間変化について考察した。全岩化学組成時張山［ときばりやま］層（26.0～18.1 Ma）は安山岩質の火砕岩と溶岩，郡［こおり］層（19.2～13.7 Ma）は玄武岩質の溶岩と火砕岩からなる。これらの火山岩はいずれも島後に分布し，非アルカリ岩とアルカリ岩の境界付近の組成を有する。不適合元素パターンは，E-MORBに類似したやや肥沃的な組成で，Nb-Taに負異常を持ち，高いLILE/HFSEを示す沈み込み帯火山岩の特徴を示す。Sr-Nd-Pb-Hf同位体組成は，第四紀の東北日本弧火山フロントの最も南部の火山グループ[2]の組成と一致する。重栖［おもす］層と葛尾［つづらお］層（5.7～5.0 Ma）は島後に広く分布し，主に粗面岩～アルカリ流紋岩の溶岩からなり，島後の西部ではショショナイト（5.5～5.1 Ma）がシート状に郡層中に貫入している。また，島前火山の外輪山上部溶岩（5.8～5.6 Ma）は，島前に広く分布し，主に粗面安山岩～粗面岩の溶岩からなる。これらの酸性岩類はいずれも，OIBに類似した肥沃な不適合元素組成を示し，ショショナイトを除き，Ba，Sr，Euに顕著な負異常がみられる。ショショナイトは，Nb-Ta，Zr-HfおよびSrに弱い負異常が認められる。これらのアルカリ酸性岩類の同位体組成は，下部地殻起源と考えられる隠岐島後の苦鉄質捕獲岩[3]の組成に近い。同時期の島前には，アルカリ玄武岩質の外輪山下部溶岩（6.3～5.8 Ma）が分布する。また，島前の宇受賀［うずか］玄武岩（2.9 Ma）は，スピネルレルゾライトを捕獲する島後のアルカリ玄武岩（4.7～0.42 Ma）と同時期のアルカリ玄武岩の活動である。これらのアルカリ玄武岩はいずれも，OIBに類似した極めて肥沃的な組成で滑らかな不適合元素パターンを示し，大和海盆の玄武岩とEM-Iの中間的な同位体組成を示す。なお，スピネルレルゾライトの捕獲岩は，日本海の海底玄武岩の同位体組成[4など]と類似する。（年代値は浦郷図幅[5]，西郷図幅[1]より引用）考察アルカリ玄武岩は，一部に未分化玄武岩を含み，数％以下のかんらん石の逆分別により，初生メルト組成を求めることができる。初生メルトの温度とマグマ分離深度は1290-1380℃，1.8-2.6 GPaと見積もられ，スピネルレルゾライトの高圧側のリキダス温度に近い。隠岐島後のレルゾライト捕獲岩の同位体組成は，時張山層・郡層火山岩の組成とは明らかに異なる。つまりこれらのかんらん岩は，阿部ら[6]の主張する日本海拡大期に噴出した玄武岩の残存固相である可能性がある。このレルゾライトはスピネル相の安定領域を示すことから，日本海拡大を引き起こしたアセノスフェアマントルは，アルカリ玄武岩の起源マントル（EM-I）の直上に分布していると推定される。隠岐諸島の火山活動は，7-5 Ma頃にアルカリ岩系列の玄武岩と酸性岩のバイモーダルな火山活動が生じている。この時期のアルカリ酸性岩類は，玄武岩質マグマによる下部地殻の部分融解，あるいは混染作用により生成されたと考えられており[7など]，本研究による微量元素・同位体組成の特徴もこの見解を支持する。以上を総合的に解釈すると，隠岐諸島の周辺では少なくとも18 Ma頃までは古い大陸下リソスフェアマントルに由来する沈み込み帯マグマが生成され，15 Ma頃までに日本海拡大を引き起こしたアセノスフェアマントルが流入し，7 Ma頃には，さらにその下位から肥沃的なマントル（EM-I）が流入してきたと考えられる。※本研究は，2019年度，2020年度隠岐ジオパーク研究助成を受けた。引用文献[1]鈴木ほか, 2009, 5万分の1西郷図幅，[2]Kimura and Yoshida, 2006, J.Petrol.，[3]Moriyama, 2006, 岡山大博論，[4]Hirahara et al., 2015, G3，[5]千葉ほか, 2000, 5万分の1浦郷図幅，[6]Abe et al., 2003, Island Arc，[7]小林ほか, 2002, 岩鉱

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Spatial distribution and pollution assessment of trace elements Pb, Cu, Ni, Fe and as in the surficial water of Staring Bay, Indonesia

Armid A.

Journal of the Brazilian Chemical Society ( Journal of the Brazilian Chemical Society ) 32 ( 2 ) 299 - 310 2021年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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第一原理計算による溶融鉄-溶融ケイ酸塩間のHf~W分配とそのエチオピア玄武岩の182W同位体に対する示唆

鈴木勝彦, 賞雅朝子, 土屋卓久, 深海雄介, 折橋裕二, 新城竜一

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 68 ( 0 ) 115 2021年

掲載種別: 研究論文（研究会，シンポジウム資料等）

182Wは消滅核種182Hfのβ壊変によって生成される。ハワイ，サモアなどの海洋島玄武岩には現在のマントル値に対して低い182W同位体を持つ。本研究では、地球初期のコア分離において、第一原理自由エネルギー計算により、コア-マントル境界P-T条件においても、Wは液体金属相に強く分配され、Hfは溶融ケイ酸塩に留まることが明らかになった。このようなHf-Wの分別により、コアは182Hf /182W比が低くなり，その結果コアは182Wの低い特性を持つことになる。本研究ではさらに，エチオピア玄武岩のW同位体比組成を分析した。その結果，エチオピア玄武岩は，現在の平均的なマントルに比べてわずかに負のμ182Wを示した。この結果と上記の第一原理計算によるコアの低い182W同位体を考え合わせると，ハワイ，サモアの玄武岩やエチオピア玄武岩は182W同位体値の低いコア成分を含んでいる可能性が高いことを示唆する。

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"Petrogenesis of gabbroic rocks from the Malayer plutonic complex (Sanandaj-Sirjan zone, west Iran)": Discussion

Deevsalar, R; Shinjo, R

PERIODICO DI MINERALOGIA ( Periodico di Mineralogia ) 89 ( 3 ) 281 - 284 2020年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Evaluation of geochemical records as a paleoenvironmental proxy in the hypercalcified demosponge Astrosclera willeyana

Asami R.

Progress in Earth and Planetary Science ( Progress in Earth and Planetary Science ) 7 ( 1 ) 2020年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Petrogenesis of gem sapphire in a pegmatite-aplite vein from the Alvand batholith, Western Iran

Sheikhi Gheshlaghi R.

Mineralogy and Petrology ( Mineralogy and Petrology ) 114 ( 6 ) 501 - 513 2020年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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High-Resolution Evidence for Middle Holocene East Asian Winter and Summer Monsoon Variations: Snapshots of Fossil Coral Records

Asami R.

Geophysical Research Letters ( Geophysical Research Letters ) 47 ( 16 ) 2020年08月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Barium isotope systematics of subduction zones

Nielsen S.G.

Geochimica et Cosmochimica Acta ( Geochimica et Cosmochimica Acta ) 275 1 - 18 2020年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Subduction zones are the focal points of mass transfer between the surface and deep Earth. Despite their significance, there remains substantial debate regarding the specific mechanisms of material transport from the slab to the overlying magmatic arc. Broadly, models accounting for slab material transport focus on the relative sequence of events promoting arc volcanism and, in particular, whether mobilization of the down-going slab leads or lags mixing with the mantle wedge. To address these uncertainties, we outline the utility of barium (Ba) isotope mass balance in subduction zones as a means to test different slab material transport models. Barium is a highly fluid-mobile element that is significantly enriched in arc magmas and is thus thought to be a sensitive tracer of slab material transport in arcs.We also present qualitative Ba isotopic mass balances for two well-characterized subduction zones the Aleutian and Ryu- kyu magmatic arcs by analyzing the Ba isotope systematics of their respective subduction inputs and outputs. Despite the narrow (and similar) Ba-isotope range of slab inputs to both systems, we find that erupted magmas exhibit systematic variations indicative of a small negative isotope fractionation during Ba mobilization (approximate to 20-40 ppm AMU(-1)). We suggest that AOC (altered oceanic crust) is not the principal source of these negative isotope values using other geochemical parameters (e.g., Rb/Ba, Pb isotopes), and infer that the Ba isotope composition of AOC though contributing a minor amount of Ba in these systems is isotopically heavier than the overlying sediment package and the depleted mantle. Altogether, these findings are significant as they indicate that the magnitude of isotope fractionation associated with Ba mobilization is small relative to the likely isotopic contrast between subduction inputs in other subduction zones, such as beneath areas of strong ocean upwelling (e.g., South Sandwich, Kamchatka). Thus, we propose that the Ba isotope composition of erupted arc magmas holds great promise for constraining the importance of different slab components, which could help address uncertainties regarding the mechanism of slab material transport in subduction zones. (C) 2020 Elsevier Ltd. All rights reserved.

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Geochemical characteristics of mafic and felsic igneous rocks (1.9–1.75 ga) in the lesser Himalaya: Regional variation and its implications for tectonic setting

Shinjo R.

Island Arc ( Island Arc ) 29 ( 1 ) 1 - 14 2020年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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“Petrogenesis of gabbroic rocks from the Malayer plutonic complex (Sanandaj-Sirjan zone, west Iran)”: Discussion

Reza Deevsalar, Ryuichi SHINJO

Periodico di Mineralogia 89 281 - 284 2020年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Geochemical and isotopic constraints on the evolution of magma plumbing system at Damavand Volcano, N Iran

Eskandari, A, Deevsalar, R, De Rosa, R, Shinjo, R, Donato, P, Neill, I

Lithos ( Lithos ) 354-355 2019年10月 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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Pleistocene basaltic volcanism in the Kr_ng N_ area and vicinity, Dac Nong Province (Vietnam)

Nguyen Hoang, Shinjo Ryuichi, La The Phuc, Le Duc Anh, Tran Thi Huong, Pecskay Zoltan, Dao Thai Bac

JOURNAL OF ASIAN EARTH SCIENCES ( Journal of Asian Earth Sciences ) 181 103903 2019年09月 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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Geochemical fractions and modeling adsorption of heavy metals into contaminated river sediments in Japan and Thailand determined by sequential leaching technique using ICP-MS

Wijaya Anugrah Ricky, Ohde Shigeru, Shinjo Ryuichi, Ganmanee Monthon, Cohen Michael Dustin

ARABIAN JOURNAL OF CHEMISTRY ( Arabian Journal of Chemistry ) 12 ( 6 ) 780 - 799 2019年09月 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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Features in REE and Methane Anomalies Distribution in the East China Sea Water Column: a Comparison with the South China Sea

Le Due Luong, Shakirov Renat B, Nguyen Hoang, Shinjo Ryuichi, Obzhirov Anatoly, Syrbu Nadezhda, Shakirova Maria

WATER RESOURCES ( Water Resources ) 46 ( 5 ) 807 - 816 2019年09月 [ 査読有り ]

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Biotite compositional variations - A physicochemical approach to investigate crustal involvement and ore potential in Middle Jurassic plutonic rocks from the Malayer-Boroujerd Plutonic complex, W Iran

Yeganehfar Hadi, Deevsalar Reza, Ahadnejad Vahid, Shinjo Ryuichi, Neill Iain

NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN ( Neues Jahrbuch fur Mineralogie, Abhandlungen ) 196 ( 1 ) 19 - 42 2019年06月 [ 査読有り ]

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エチオピア玄武岩とアデン湾MORBの高精度182W/184W比：コア－マントル相互作用検出の試み

鈴木勝彦, 賞雅朝子, 深海雄介, 飯塚毅, 折橋裕二, 新城竜一

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 66 ( 0 ) 214 - 214 2019年

掲載種別: 研究論文（研究会，シンポジウム資料等）

182Hfは比較的短い半減期890万年で182Wにベータ壊変する。Hfは親石元素、Wは親鉄元素であるために、マントルとコアの間で分別が起き，マントルは高いHf/W比，コアは低いHf/W比を持つと考えられる。地球の初期，182Hfが消滅する前にコアが分離すれば，Hf/Wの高い始原マントルは高い182W/184W比を，Hf/W比の低いコアは低い182W/184W比を持っていることになる。本研究では，東アフリカAfarプルームに由来するエチオピアの玄武岩とアデン湾のMORBに適用した結果，いくつかの試料で，繰り返しの誤差の範囲を超えて負異常が得られた。コアの物質を含んでいる可能性が考えられるか，少なくとも地球ができて間もない頃の化学分別の痕跡を含んでいると考えられる。

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伊平屋島西部の2種類の緑色岩の産状と全岩化学組成：その噴出テクトニック場の考察

宇佐美賢, 宮城宏之, 我謝昌一, 宮城直樹, 新城竜一

伊是名島・伊平屋島総合調査報告書、沖縄県立博物館・美術館 1 - 20 2019年

掲載種別: 研究論文（その他学術会議資料等）

テーマセッション報告　琉球大学高度統合型熱帯海洋科学技術イノベーション創出研究拠点形成事業（ORCHIDS）プロジェクトにおける海洋科学研究の取組み

中村崇, James Davis Reimer, 新城竜一, 中村衛, 田中厚子, Hin Boo Wee

日本サンゴ礁学会誌 ( 日本サンゴ礁学会 ) 21 ( 1 ) 1 - 12 2019年

掲載種別: 研究論文（学術雑誌）

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高含水量マグマに由来する高K系列の米山層ソレアイト系列火山岩

相澤正隆, 岡村聡, 新城竜一, 高橋俊郎, 米山団体研究グループ

岩石鉱物科学 ( 一般社団法人　日本鉱物科学会 ) 48 ( 1 ) 1 - 24 2019年

掲載種別: 研究論文（その他学術会議資料等）

Late Pliocene-Early Pleistocene igneous rocks of Yoneyama Formation from the northern Fossa Magna region, central Japan, consist of basaltic to andesitic rocks and small intrusive rocks; they contain frequently hornblende (Hbl) gabbroic xenoliths and Hbl xenocrysts. Based on field data, together with petrographic, geochemical, and geochlonological descriptions, the volcanism comprised 5 stages. The rocks at the Ogamidake, the 1st and 3rd stages are tholeiitic rock series (TH), whereas calc-alkalic rock series (CA) are dominated at the 2nd and 4th stages. All rocks are characterized by high-K content and contain pargasitic Hbl phenocrysts in both rock series. Estimation using Ca-amphibole geobarometer suggests that Hbls have crystallized at depths of lower crust. Existence of Hbl and high An content of plagioclase (～ An90) in both rock series imply that both magmas are rich in H2O. Estimated H2O contents are ～ 5 wt％ for both TH and CA magmas. Based on mineral texture, P-T estimation and major-trace elements modeling, we infer that cryptic fractionation of Hbl can produce the TH magma trend. Our model is incompatible with general model that TH magma originate from anhydrous or low H2O content magma.

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北部フォッサマグナ西部の海川火山岩類における角閃石の潜在的な分別結品作用

相澤正隆, 新城竜一, 岡村聡, 宮城磯治

日本火山学会講演予稿集 ( 特定非営利活動法人日本火山学会 ) 2019 ( 0 ) 26 - 26 2019年

掲載種別: 研究論文（その他学術会議資料等）

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Breakdown of residual zircon in the Izu arc subducting slab during backarc rifting

Hirai Y.

Geology ( Geology ) 46 ( 4 ) 371 - 374 2018年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

High field strength elements (HFSEs) are depleted in subduction-related melts because of the residual minerals in the slab. It has been suggested that high slab-surface temperatures cause the breakdown of residual zircon in the slab. In this study, we found that two geochemical types can be identified within basalts from the active backarc rift zone of the Izu arc (northwest Pacific Ocean). Low-Zr/Y basalts (LZBs) were collected from across the entire area of the active rift zone, whereas the high-Zr/Y basalts (HZBs) were identified only at the Sumisu Rift. Although enrichment of large-ion lithophile elements (LILEs) and Nb-Ta depletion are recognized in both types, a minimal negative Hf concentration anomaly (Hf/Hf* = 0.98) characterizes the HZB. In Nd-Hf isotope space, the HZB lies close to the Indian/Pacific mantle boundary, displaced from the LZB. Variations in Nb/Yb and Zr/Yb indicate differences in the fertility and/or degree of melting of source mantle that can explain the HFSE systematics in the LZB, but not in the HZB. Geochemical modeling demonstrates that mixtures of mantle wedge and ~2% slab-derived melt, not in equilibrium with residual zircon, produces the observed trace-element and isotopic characteristics in the HZB. Moreover, the range of occurrence of the HZB corresponds with the range in seismic low-velocity anomalies in the upper slab. We suggest that asthenospheric material injected into the mantle wedge beneath the Sumisu Rift is a possible heat source for the breakdown of residual zircon in the slab.

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Deevsalar R.

Swiss Journal of Geosciences ( Swiss Journal of Geosciences ) 111 ( 1-2 ) 269 - 293 2018年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

The Malayer–Boroujerd plutonic complex (MBPC) in western Iran, consists of a portion of a magmatic arc built by the northeast verging subduction of the Neo-Tethys plate beneath the Central Iranian Microcontinent (CIMC). Middle Jurassic-aged felsic magmatic activity in MBPC is manifested by I-type and S-type granites. The mafic rocks include gabbroic intrusions and dykes and intermediate rocks are dioritic dykes and minor intrusions, as well as mafic microgranular enclaves (MMEs). MBPC Jurassic-aged rocks exhibit arc-like geochemical signatures, as they are LILE- and LREE-enriched and HFSE- and HREE-depleted and display negative Nb–Ta anomalies. The gabbro dykes and intrusions originated from metasomatically enriched garnet-spinel lherzolite [Degree of melting (fmel) ~ 15%] and exhibit negative Nd and positive to slightly negative εHf(T) (+ 3.0 to − 1.6). The data reveal that evolution of Middle Jurassic magmatism occurred in two stages: (1) deep mantle-crust interplay zone and (2) the shallow level upper crustal magma chamber. The geochemical and isotopic data, as well as trace element modeling, indicate the parent magma for the MBPC S-type granites are products of upper crustal greywacke (fmel: 0.2), while I-type granites formed by partial melting of amphibolitic lower crust (fmel: 0.25) and mixing with upper crustal greywacke melt in a shallow level magma chamber [Degree of mixing (fmix): 0.3]. Mixing between andesitic melt leaving behind a refractory dense cumulates during partial crystallization of mantle-derived magma and lower crustal partial melt most likely produced MMEs (fmix: 0.2). However, enriched and moderately variable εNd(T) (− 3.21 to − 4.33) and high (87Sr/86Sr)i (0.7085–0.7092) in dioritic intrusions indicate that these magmas are likely experienced assimilation of upper crustal materials. The interpretations of magmatic activity in the MBPC is consistent with the role considered for mantle-derived magma as heat and mass supplier for initiation and evolution of magmatism in continental arc setting, elsewhere.

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The processes of alteration of volcanic rocks under the influence of the fumarolic gases in the Tatun Volcano Group, Taiwan

Ke―Han SONG, Chia―Mai LIU, Ching―Huei KUO, Yu―Wei TSAI, Ryuichi SHINJO

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 65 ( 0 ) 114 2018年

掲載種別: 研究論文（研究会，シンポジウム資料等）

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北部フォッサマグナ周辺のマントル物質の改変：起源マントルとスラブ溶融成分変化

岡村聡, 稲葉充, 新城竜一

月刊地球 40 ( 4 ) 225 - 233 2018年

掲載種別: 研究論文（その他学術会議資料等）

Spatial variations in dissolved rare earth element concentrations in the East China Sea water column.

Luong, L.D, Shinjo, R, Hoang, N, Shakirov, R.B, Syrbu, N

Marine Chemistry ( Marine Chemistry ) 205 1 - 15 2018年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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Gabbroic-dioritic dykes from the Sanadaj-Sirjan Zone: windows on Jurassic and Eocene geodynamic processes in the Zagros Orogen, western Iran

Deevsalar, R, Shinjo, R, Wang, K.-L, Yeganehfar, H, Neill, I

Journal of the Geological Society ( Journal of the Geological Society ) 175 ( 6 ) 915 - 933 2018年 [ 査読有り ]

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北部フォッサマグナ周辺のマントル物質の改変：起源マントルとスラブ溶融成分変化

新城竜一

月刊地球 40 225 - 233 2018年

掲載種別: 研究論文（学術雑誌）

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首里城の大龍柱と伝えられる残欠の石質について

新城竜一

沖縄県立博物館・美術館, 博物館紀要 11 11 - 14 2018年

掲載種別: 研究論文（学術雑誌）

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首里城の大龍柱と伝えられる残欠の石質について

宇佐美賢, 佐々木健志, 知念正昭, 新城竜一

沖縄県立博物館・美術館, 博物館紀要 ( 11 ) 11 - 14 2018年

掲載種別: 研究論文（その他学術会議資料等）

米山層火山岩類のSr, Nd, Hf同位体組成

相澤正隆, 新城竜一, 岡村聡, 高橋俊郎, 米山団体研究グループ

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 65 ( 0 ) 118 - 118 2018年

掲載種別: 研究論文（研究会，シンポジウム資料等）

北部フォッサマグナ地域北東部に分布する米山層火山岩類(鮮新世-更新世)は，玄武岩から安山岩組成の火山岩からなり，5つの火山活動ステージに区分される．大部分の岩石は均質なSr, Nd, Hf同位体組成を示すが，第3ステージの岩石の一部は高Sr，低Nd，低Hf同位体組成を示し，分別結晶作用に加えて下部地殻物質の混染を受けた可能性がある．ただし，下部地殻の深度からもたらされた角閃石斑れい岩質捕獲岩は幅広いSr同位体組成を示すため，下部地殻の混染の程度を詳細に見積もるには，今後捕獲岩のHf同位体データを考慮して検討する必要がある．

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北部フォッサマグナ米山層火山岩類のマグマプロセス—希土類元素組成からの制約—

相澤正隆, 新城竜一, 岡村聡, 高橋俊郎, 藤林紀枝, 米山団体研究グループ

日本火山学会講演予稿集 ( 特定非営利活動法人日本火山学会 ) 2018 ( 0 ) 37 - 37 2018年

掲載種別: 研究論文（その他学術会議資料等）

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下北半島泊層火山岩類ボーリングコアの岩石学的検討

相澤正隆, 稲葉充, 岡村聡, 新城竜一

日本地質学会学術大会講演要旨 ( 一般社団法人日本地質学会 ) 2018 ( 0 ) 368 - 368 2018年

掲載種別: 研究論文（その他学術会議資料等）

【災害のためプログラム中止】平成30年北海道胆振東部地震により学術大会のプログラムが大幅に中止となりました．中止となったプログラムの講演要旨については，著者のプライオリティ保護の見地からJ-STAGEに公開し，引用可能とします．ただし，学術大会においては専門家による議論には供されていませんので「災害のためプログラム中止」との文言を付記します．（日本地質学会行事委員会）

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Tracing subducted sediment inputs to the Ryukyu arc-Okinawa Trough system: Evidence from thallium isotopes

Shu Y.

Geochimica et Cosmochimica Acta ( Geochimica et Cosmochimica Acta ) 217 462 - 491 2017年11月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Sediments are actively subducted in virtually every arc worldwide. However, quantifying their contributions to arc lavas and thereby establishing budgets of how sediments participate in slab-mantle interaction is challenging. In this contribution we use thallium (Tl) abundances and isotopic compositions of lavas from the Ryukyu arc (including south Kyushu) and its back-arc basin, Okinawa Trough, to investigate the influence of sediments from arc to back-arc. We also present extensive geochemical data for sediments and altered oceanic crust (AOC) outboard of the northern (DSDP Sites 296, 442B, 443 and 444) and central (DSDP Sites 294 and 295) part of the Ryukyu arc. The Tl isotopic compositions of sediments change systematically from lighter outboard of northern Ryukyu arc to heavier outboard of central Ryukyu arc. The feature reflects the dominance of terrigenous material and pelagic sedimentation outboard of the northern and central Ryukyu arc, respectively. Central and northern sections of Ryukyu arc and Okinawa Trough display larger range of Tl isotopic variation than southern section, which is consistent with more pelagic provenance for sediments outboard of central and northern Ryukyu arcs than that of expected sediments outboard of southern Ryukyu arc. Identical Tl, Sr, Nd and Pb isotope variations are found when comparing arc and back arc lavas, which indicates that sediments fluxes also account for the Tl isotopic variations in the Okinawa Trough lavas. Two-end-member mixing models of Tl with Pb, Sr and Nd isotopes require sediment inputs of< 1%, 0.1-1% and 0.3-2% by weight to the depleted mantle source to account for all these isotopic compositions of lavas from northern, central and southern portion of the Ryukyu arc and Okinawa Trough. Bulk mixing between mantle and sediment end members predict very similar sediment fluxes when using Tl, Sr, Nd and Pb isotopes, which indicates that fractionation of these elements must have happened after mixing between mantle and sediments. This conclusion is corroborated by model calculations of mixing between sediment melts with fractionated Sr/Nd ratios and mantle wedge, which show that no arc lava plot on such mixing lines. Thus bulk sediment mixing, rather than sediment melt, is required for the generation of the lavas from the Ryukyu arc and Okinawa Trough. The requirement of bulk sediment mixing occurring before trace element fractionation in the sub-arc mantle is consistent with models where melange layers form at the top of the slab and are the principle source material for arc lavas. In addition, the fact that sediment components observed in the Ryukyu arc and OkinawaTrough lavas are similar, suggests that transport of melange material to the source regions of the arc and back arc is equally efficient. This feature is most readily explained if melange material is transported from the slab as diapirs. (C) 2017 Elsevier Ltd. All rights reserved.

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Mesozoic–Cenozoic mafic magmatism in Sanandaj–Sirjan Zone, Zagros Orogen (Western Iran): Geochemical and isotopic inferences from Middle Jurassic and Late Eocene gabbros

Deevsalar R.

Lithos ( Lithos ) 284 588 - 607 2017年07月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

One of the consequences of Neo-Tethys ocean subduction beneath the Central Iranian Micro-continent (CIMC) is the development of rare gabbroic intrusions in the Malayer-Boroujerd Plutonic Complex (MBPC) located in the Sanandaj-Sirjan Zone (SaSZ) of the Zagros Orogenic belt. The MBPC is a suite of extensive felsic and lesser mafic magmatic products in the northern SaSZ with geochemical signatures of arc-like magmatism during the Middle Jurassic (Ghorveh-Aligudarz arc) and intraplate type in the Late Eocene. Middle Jurassic gabbros (non-cumulate and cumulate) have low-Ti concentrations (<1 wt.%) and quite uniform isotopic compositions (initial Sr-87/Sr-86: 0.7035-0.70593 and epsilon Nd(t): -6.18 to -0.7), enriched LILE relative to HFSE, variable fractionation between the LREE and HREE ((La/Yb)(cn) : 227-7.45) and both negative to positive Eu anomalies. These distinctive features of arc-type magmatism are consistent with a subduction-modified mantle source for these rocks. Trace element and REE models indicate similar to 15% melting of a metasomatized amphibole-bearing garnet-spinel lherzolite (gamet:spinel similar to 7:3) in the sub-arc mantle wedge. The cumulate gabbros and non-cumulates belong to common liquid line of descent, with complementary trace element patterns. Much of the variation between samples can be modeled by fractional crystallization (FC) of a common parent; only one cumulate gabbro from this suite exhibits isotopic evidence of contamination, probably by Rb-depleted crustal materials. The Late Eocene gabbros have relatively high-Ti (>1 wt.%) and display isotopically depleted Sr-Nd values (initial Sr-87/Sr-86: 0.7044-0.7087, epsilon Nd(t): 1.9 -+3.2, barring one crustally-contaminated sample). OIB-like trace element characteristics such as enriched HFSE, and only minor enrichment of LILE and LREE, reflect a within-plate character and asthenospheric source. Trace element modeling indicates small degree melting (f(melting): 0.05) of upper mantle lherzolite (garnet:spinel similar to 3:1) followed by higher degree melting (f(melting): 0.15) at shallower depths (garnet:spinel similar to 4.5:2). The Eocene parental magma underwent FC of olivine and clinopyroxene. We propose that Eocene asthenospheric upwelling was triggered by slab tearing in response to slab-rollback, which is elsewhere reported to have triggered a 'flare-up' of extension-related magmatism across Iran. Three stages of tectono-magmatic evolution in the Ghorveh-Aligudarz arc segment of the N-SaSZ are represented by: 1) arc-like magmatism during active subduction of the Neo-Tethys seaway at Middle Jurassic, 2) magmatic quiescence during an interval of shallow-angle or highly oblique subduction during the Cretaceous-Paleocene, and 3) asthenosphere melting during slab tearing shortly before the onset of the Arabia-Eurasia collision. (C) 2017 Elsevier B.V. All rights reserved.

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Petrologic and geochemical characterization of rift-related magmatism at the northernmost Main Ethiopian Rift: Implications for plume-lithosphere interaction and the evolution of rift mantle sources

Feyissa D.

Lithos ( Lithos ) 282 240 - 261 2017年06月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

In this paper, we present petrography, K-Ar ages, whole-rock major- and trace-element concentrations, and Sr-Nd-Hf-Pb isotopic ratios of volcanic rocks from Debre Birhan area in the northernmost Main Ethiopian Rift (MER). The K-Ar ages of the mafic series range from 27 to 0.25 Ma, and two felsic rocks yield ages of 0.93 and 0.23 Ma. The mafic volcanics are classified into older and younger series based on their K-Ar ages. The Mg-numbers (Mg# < 60) of both mafic series, along with low Ni and Cr contents, clearly indicate that these lavas have undergone fractionation en route to the surface. Geochemical and isotopic compositions of the older and younger mafic lavas indicate that crustal contamination did not play a significant role in the evolution of their magmas, hence reflect the geochemical characteristics of the sources. The older and younger mafic volcanic rocks display contrasting trace element and isotopic signatures. The older lavas have higher La/Nb, Zr/Nb, Ba/Nb and Sr-87/Sr-86(i) (0.70445-0.70681) and lower epsilon(Hf) (-2.58 to + 6.01) and epsilon(Nd) ( -1.25 to +3.43) and less radiogenic Pb isotopic ratios (Pb-206/(204)Pbi = 17.82-18.64, except TG-54 = 19.1) relative to the younger mafic lavas. Correlations among isotopic ratios and trace element concentrations provide evidence for the involvement of at least three major end-member components (C-1, C-2, and C-3) in the petrogenesis of these mafic lavas. The C-1 end-member component contributes dominantly to younger mafic lavas, and has isotopic composition similar to the common component 'C' deduced from oceanic basalts. The second end-member component (C-2) is represented by lavas near the transition between older and younger, and has isotopic composition similar to that of the seafloor basalts of the Red Sea and the Gulf of Aden. The third end-member component (C-3) is prominent in the older mafic series, and similar isotopically to Pan-African lithosphere. The younger felsic volcanic rocks generally have higher Sr-87/Sr-86(i) (0.70395-0.70689) than younger mafic series (0.70366-0.70454) but Nd, Hf and Pb isotopic ratios similar to those of the younger mafic lavas. The element concentrations and Sr, Nd, Hf and Pb isotopic compositions of the younger felsic rocks are explained by fractional crystallization of mafic melts in shallow-level magma chambers accompanied by limited assimilation of crustal material. Low degrees of partial melting of existing mafic underplate can account for the genesis of the least differentiated (intermediate) lavas, but failed to explain highly evolved younger felsic rocks. (C) 2017 Elsevier B.V. All rights reserved.

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Contribution of slab-derived fluid and sedimentary melt in the incipient arc magmas with development of the paleo-arc in the Oman Ophiolite

Kusano Y.

Chemical Geology ( Chemical Geology ) 449 206 - 225 2017年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Major-element and trace-element geochemistry of fresh volcanic glass, and the whole-rock Hf and Nd isotopic compositions of volcanic rocks from the Oman Ophiolite were used to understand the extent to which slab-derived fluids and melts were involved in magma generation during incipient arc development. The spreading stage (V1) samples have trace-element characteristics similar to those of mid-ocean-ridge basalts, with Hf and Nd isotopic compositions of the Indian mantle domain. The incipient arc stage (V2) volcanic glasses have lower abundances of high field strength elements (HFSEs) and middle and heavy rare earth elements (MREE5 and HREES), and higher abundances of large ion lithophile elements (LILEs) than the V1 glasses. Progressive increases in B, Pb, and LILEs in the V2 stage glasses with age indicate an increasing contribution of slab-derived fluids from earlier arc tholeiite (LV2) to later boninite (UV2). The LV2 was generated by the contribution of amphibolite-derived fluid. The UV2 is subdivided into low-Si UV2 and high-Si UV2 magmas, with the former having lower SiO2, and LILE, and higher Na2O, HFSE and REE concentrations than the latter. The low-Si UV2 magma was generated with the involvement of high-temperature slab-derived fluid. In contrast, the high-Si UV2 shows a spoon-shaped trace-element pattern and Hf and Nd isotope chemistry, indicating the involvement of sediment melt in its magma genesis. Decreasing HFSEs and HREEs in the magmas with age indicate progressive depletion of the source mantle during the V2 arc magmatism, suggesting an absence of convection in the mantle wedge that resulted from subduction of a hot, buoyant slab beneath young, hot lithosphere. (C) 2016 Elsevier B.V. All rights reserved.

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Pollution assessment of various heavy metals in the surface sediment of Kendari Bay, Indonesia

新城竜一

Nature Environment and Pollution Technology 16 1067 - 1074 2017年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Pollution assessment of various heavy metals in the surface sediment of Kendari Bay, Indonesia

Armid, A, Shinjo, R, Sabarwati, S.H, Ruslan, R

Nature Environment and Pollution Technology 16 ( 4 ) 1067 - 1074 2017年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

北部フォッサマグナ周辺の新生代火成活動と背弧海盆テクトニクス

岡村聡, 稲葉充, 足立佳子, 新城竜一

地球科学 ( 地学団体研究会 ) 71 ( 2 ) 65 - 73 2017年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

地質調査で採取された堆積物試料中の間隙水の地球化学的解析

石橋純一郎, 土岐知弘, 新城竜一

SIP 『次世代海洋資源調査技術』（海のジパング計画）　海底熱水鉱床の調査技術プロトコル - 61 2017年

掲載種別: 研究論文（学術雑誌）

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地質調査で採取された堆積物試料中の間隙水の地球化学的解析

石橋純一郎, 正木裕香, 岡村慶, 野口拓郎, 土岐知弘, 新城竜一

SIP 『次世代海洋資源調査技術』（海のジパング計画）海底熱水鉱床の調査技術プロトコル 2017年

掲載種別: 研究論文（その他学術会議資料等）

北部フォッサマグナ周辺の新生代火成活動と背弧海盆テクトニクス

岡村聡, 稲葉充, 足立佳子, 新城竜一

地球科学 ( 地学団体研究会 ) 71 ( 2 ) 65 - 73 2017年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

北部フォッサマグナ周辺の新第三系玄武岩類について，同位体組成と微量元素組成を検討した結果，マグマの起源物質とマントルウェッジの熱構造が漸新世から鮮新世にかけて変化することが明らかとなった．前期中新世玄武岩は，一部の玄武岩（切明玄武岩）を除き，HFS 元素に富み低176 Hf/ 177 Hf 比，低143 Nd/ 144 Nd 比を示すエンリッチした組成からなり，大陸縁辺を構成していた大陸下リソスフェアマントル起源と考えられる．中期中新世～鮮新世玄武岩は，HFS 元素に乏しく高176 Hf/ 177 Hf 比，高143 Nd/ 144 Nd 比を示す枯渇した組成であり，中でも中期中新世玄武岩は，インド洋MORB に類似の最も枯渇した同位体組成を示す．これらの枯渇組成マグマは，背弧海盆である日本海の拡大をもたらしたMORB 様アセノスフェアマントル起源だったらしい．漸新世～前期中新世のエンリッチしたマグマは，湧昇してきたアセノスフェアマントルの加熱によって，リソスフェアマントルが部分溶融して造られたと考えられるが，同時期に活動した枯渇組成の切明玄武岩の存在は，北部フォッサマグナにおいて，中絶リフト軸部に沿ってアセノスフェアの部分溶融メルトが生じたことを示す．各時代の玄武岩質火山岩類の化学組成は，異なるマントル物質の部分溶融に加え，スラブ堆積物の脱水作用や部分溶融メルトの影響を受けている．漸新世～中期中新世玄武岩類は，スラブ堆積物の高温部分溶融メルトの汚染を受けており，後期中新世～鮮新世玄武岩類は，ジルコンを残存固相とする低温部分溶融メルトによって汚染されたことを示唆する．

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伊是名海穴における海底下鉱体周辺の熱水性成分の分布

土岐知弘, 大竹翼, 石橋純一郎, 松井洋平, 川口慎介, 加藤大和, 淵田茂司, 宮原玲奈, 堤映日, 中村峻介, 川喜田竜平, 宇座大貴, 上原力, 新城竜一, 野崎達生, 熊谷英憲, 前田玲奈

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 64 ( 0 ) 147 - 147 2017年

掲載種別: 研究論文（学術雑誌）

2016年11月16日～12月15日にかけて、SIP「海のジパング計画」の一環として沖縄トラフの伊是名海穴HAKUREIサイトにおいて、地球深部探査船「ちきゅう」を用いて海底熱水域を掘削した。掘削は、HAKUREIサイトの北部マウンドの頂上から、東側に約500 mの測線上において5本、またリファレンスサイトとしてマウンドから北西500 mほど離れた地点において1本を掘削した。採取したコアから、船上でヘッドスペースガス測定用および間隙水抽出用の試料を採取した。試料から抽出した間隙水について、船上でpH、アルカリ度、栄養塩および硫化水素濃度を、陸上で主成分および微量元素濃度、並びにホウ素同位体比を測定した。また、ガス測定用の試料については、船上で炭化水素および水素濃度を、陸上においてメタンの炭素同位体比を測定した。

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Fluid flow and water–rock interaction across the active Nankai Trough subduction zone forearc revealed by boron isotope geochemistry

Hüpers A.

Geochimica et Cosmochimica Acta ( Geochimica et Cosmochimica Acta ) 193 100 - 118 2016年11月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Compositional changes, dehydration reactions and fluid flow in subducted sediments influence seismogenesis and arc magmatism in subduction zones. To identify fluid flow and water-rock interaction processes in the western Nankai Trough subduction zone (SW Japan) we analyzed boron concentration and boron isotope composition (delta B-11) of pore fluids sampled across the subduction zone forearc from depths of up to similar to 922 m below seafloor during four Integrated Ocean Drilling Program (IODP) Expeditions. The major structural regimes that were sampled by coring include: (1) sedimentary inputs, (2) the frontal thrust zone, (3) the megasplay fault zone, and (4) the forearc basin. From mass balance consideration we find that consumption of boron (B) by ash alteration and desorption of B from the solid phase, mediated by organic matter degradation, produces a net decrease in B concentrations with depth down to similar to 120 mu M and variable (delta B-11) values in the range of similar to+20 parts per thousand and +49 parts per thousand. Interstitial water in sediments on the incoming oceanic plate are influenced by more efficient mobilization of exchangeable B from the solid phase due to higher temperatures and alteration of the oceanic crust that acts as a sink for B-10. At the tip of the megasplay fault zone, elevated B concentration and B isotopic composition suggest that underthrust coarse-grained slope sediments provide a pathway for fluids out of the upper(<2 km) accretionary prism. Silt and sand layers in the underthrust section of the downgoing plate favor fluid escape in seaward direction from depths equivalent to the temperature range of 60-150 degrees C. At both locations the (delta B-11) signature evolves during updip migration through re-adsorption. Mass balance considerations suggest a shallower fluid source depth compared to pore fluids sampled previously near the decollement zone along the central portion of the Nankai margin. (C) 2016 Elsevier Ltd. All rights reserved.

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Miocene-Pliocene mantle depletion event in the northern Fossa Magna, western NE Japan

Okamura S.

Journal of Geodynamics ( Journal of Geodynamics ) 97 42 - 61 2016年07月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

New isotopic and trace element data presented here imply a temporal change in magma sources and thermal conditions beneath the northern Fossa Magna of NE Japan from the Miocene to the Pliocene. Less radiogenic Hf-176/Hf-177 and Nd-143/Nd-144, high Zr/Hf, and little or no Hf anomaly characterize the Early Miocene volcanism in the northern Fossa Magna region. The mantle wedge consisted of chemically heterogeneous mantle source. Based on out isotope proxies, we propose that during the onset of subduction, influx of hot asthenospheric mantle provided sufficient heat to partially melt newly subducting sediment. Geochemical modeling demonstrates that slab-derived melt mixed with mantle wedge produces the observed isotopic and trace elemental characteristics. In the Middle Miocene, the injection of hot and depleted asthenospheric material replaced the mantle beneath the northern Fossa Magna region of NE Japan. This caused the isotopic signature of the rocks to change from enriched to depleted. Then, the mantle wedge was gradually cooled during the Middle Miocene to the Pliocene with back-arc opening ending in the Late Miocene. Slab surface temperatures were still high enough for sediments to melt but not too high (<similar to 780 degrees C) to lose zircon as a residual phase. The Late Miocene and Pliocene volcanism at the post stage of the back-arc opening is best explained by a partial melting of subducted metasediment saturated with trace quantities of zircon and rutile. (C) 2016 Elsevier Ltd. All rights reserved.

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Development of a New Method of Extraction of Interstitial Water from Low-Porosity Consolidated Sediments Recovered During Super-Deep Drilling Projects

Toki T.

Geostandards and Geoanalytical Research ( Geostandards and Geoanalytical Research ) 40 ( 2 ) 291 - 300 2016年06月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

During the Integrated Ocean Drilling Program (IODP) Expedition 338, several methods were tested for the extraction of interstitial water in consolidated, low-porosity deep-sea sediments from Site C0002 in the Kumano Basin. On the basis of those tests, we propose a modified ground rock interstitial normative determination (GRIND) method of extraction of interstitial water. In separate runs of the new method, sediment samples were ground in a ball mill with either ultrapure water or a solution of HNO3. The interstitial water was then extracted with a conventional squeezer. Sufficient solution was extracted by this method to analyse most major and a few minor components of interstitial water that were comparable to those previously reported for samples extracted by the conventional squeezing method. The new method requires much smaller amounts of sediment than that of the conventional method and will be useful for analysis of samples recovered during superdeep drilling programmes.

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Finite element method (FEM) groundwater inflow modeling associated with an unconfined aquifer into the open-pit coalmine of the Phulbari area, NW Bangladesh

Islam M.

Arabian Journal of Geosciences ( Arabian Journal of Geosciences ) 9 ( 5 ) 394 2016年05月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

This paper uses a two-dimensional finite element method (FEM) numerical modeling to predict groundwater inflow from an unconfined aquifer into the open-pit coalmine in the Phulbari area of northwest Bangladesh. The rock mass of the unconfined aquifer in the Phulbari coal deposit is highly porous and permeable. Interconnected pores within rock mass are the main paths for groundwater flow. Model assumes groundwater inflow rate through the rock mass associated with interconnected pores. Eleven stages of computation associated with variable overall pit slope angle (OPSA) 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, 30 degrees, 31 degrees, 32 degrees, 33 degrees, 34 degrees, and 35 degrees are presented here. Model reveals that the probable inflow rate from unconfined aquifer in the open-pit coalmine would be about 377.68, 364.93, 354.38, 340.20, 331.29, 326.36, 316.86, 315.36, 308.03, 302.86, and 298.00 m(3)/h with relevant slope angles of 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, 30 degrees, 31 degrees, 32 degrees, 33 degrees, 34 degrees, and 35 degrees, respectively. It is reasonable to emphasize that the computed inflow rate (m(3)/h) in the present numerical model would be effective through unit width of rock strata up to the pit depth of about 320 m in the Phulbari coal deposit. From the simulation results, it is thought that the open-pit coalmine in the Phulbari area would be an environmentally challenging issue because of regional unconfined mega-aquifer.

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The epilog of the western paleo-Pacific subduction: Inferred from spatial and temporal variations and geochemistry of the Late Cretaceous to Early Cenozoic silicic magmatism in coastal South China

Chen C.

Journal of Asian Earth Sciences ( Journal of Asian Earth Sciences ) 115 520 - 546 2016年01月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

The Late Cretaceous to Early Cenozoic magmatism in the South China coastal area produced some amounts of rhyolitic rocks in two phases, which may be used to unravel the geohistory of the epilog of the paleo-Pacific plate subduction system. Essence of the Phase I rocks is the high temperature rhyolite (A-type)-trachydacite association in north Fujian (95-91 Ma) that was coeval with regional A-type granites. They succeeded the vast rhyolite-dacite-andesite (RDA) associations and I-type granitoids (113.5-96 Ma) and preceded the silicic-dominating rhyolite/basalt bimodal suites or monolithologic rhyolite in Zhejiang (89-86 Ma). Phase II rocks include (a) the RDA association or rhyolite alone in some drifted continental fragments nearby (83-56 Ma) and (b) the following rift-basin related rhyolite-tra chyte/basalt bimodal suites in Guangdong and west Taiwan (56-38 Ma). The silicic volcanism, spatially changed from a NE-SW to the nearly E-W direction after 83 Ma, may reflect tectonic-driven eruptions occurred in the post-orogenic extensional (Phase I), resumed plate subducting (Phase Ha) and continental margin rifting (Phase IIb) stages. Rhyolitic rocks basically are shoshonitic to high-K calc-alkaline affinities while the Phase Ha RDA associations are mostly concentrated in the high-K to medium-K calc-alkaline series. All these rocks generally possess a continental arc character in tectonic discrimination diagrams, except shoshonitic rocks that have within-plate signatures. Based on the trace element and Nd-Pb isotope data, A-type rocks are suggested to have derived from mixing between trachydacitic (or syenitic) magmas and crustal melts of various sources under the high temperature condition (+/- metasomatism), and the succeeding silicic rocks are derivatives of the contaminated lithospheric mantle melts through crystal fractionation. On the other hand, Phase II silicic rocks are mainly the fractionation products of mafic magmas originated either from the lithospheric or the asthenospheric mantle. In reflection to such magmatotectonics with time, break-off of the subducted slab shortly before 113.5 Ma, change of the plate-moving direction between 86 and 83 Ma, and termination of plate movement probably at similar to 56 Ma signify the epilog of the paleo-Pacific plate. (c) 2015 Elsevier Ltd. All rights reserved.

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鳥海山、貞観噴火前後の噴出物の特徴の変化

高橋拓也, 伴雅雄, 大場司, 林信太郎, 新城竜一

日本鉱物科学会年会講演要旨集 ( 一般社団法人日本鉱物科学会 ) 2016 ( 0 ) 186 2016年

掲載種別: 研究論文（研究会，シンポジウム資料等）

鳥海火山は過去約60万年間、山体の成長と崩壊を繰り返してきた。最新の山体崩壊は紀元前466年に発生し、東鳥海カルデラが形成された。その後はカルデラ内で溶岩流出主体の活動が続いている。また、鳥海山は西暦869年の貞観地震の2年後に噴火（貞観噴火）しており、東北地方太平洋沖地震後、噴火が危ぶまれる火山の一つである。そこで、本研究では、貞観地震の前後における噴出率やマグマの特徴に変化がみられるかどうかを火山地質学・岩石学的に検討した。その結果、貞観噴火を境にして、噴出率が低下したこと、また苦鉄質マグマの組成が変化したことなどが判明した。

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ダンボールでしゅう曲を作る(監修)

新城竜一

理科教育ニュース 2016年11月28日発行 ( 995 ) 2016年

掲載種別: 研究論文（その他学術会議資料等）

Geochemical characteristics of hydrothermal fluids at Hatoma Knoll in the southern Okinawa Trough

Toki Tomohiro, Itoh Michihiro, Iwata Daigo, Ohshima Shogo, Shinjo Ryuichi, Ishibashi Jun-ichiro, Tsunogai Urumu, Takahata Naoto, Sano Yuji, Yamanaka Toshiro, Ijiri Akira, Okabe Nobuaki, Gamo Toshitaka, Muramatsu Yasuyuki, Ueno Yuichiro, Kawagucci Shinsuke, Takai Ken

ＧＥＯＣＨＥＭＩＣＡＬ　ＪＯＵＲＮＡＬ ( 一般社団法人日本地球化学会 ) 50 ( 6 ) 493 - 525 2016年

掲載種別: 研究論文（学術雑誌）

Chemical and isotopic compositions of hydrothermal fluids from Hatoma Knoll in the southern Okinawa Trough were investigated. The hydrothermal fluids were derived from a single pure hydrothermal fluid source, but they underwent phase separation beneath the seafloor prior to venting. Only vapor-like fluids vent at the Hatoma system, and the most active area is around the center of the crater, based on the location of the maximum temperature and the lowest Cl– concentrations. Compared with other hydrothermal systems in the world, at Hatoma the pH and alkalinity, as well as the B, NH4+, K, Li, CO2, and CH4 concentrations, were higher, and the Fe and Al concentrations were lower, suggesting that the characteristics of the Hatoma hydrothermal fluids are comparable to those of the other Okinawa Trough hydrothermal fluids. Helium isotope ratios were lower than those of sediment-starved hydrothermal systems, suggesting that 4He derived from the sediment is supplied to the hydrothermal fluids in Hatoma Knoll. The carbon isotope ratios of CO2 in the hydrothermal fluids indicate an influence of organic carbon decomposition. The carbon isotope ratios of CH4 in the hydrothermal fluids imply that most of the CH4 originated from microbial methane produced in a recharge zone of the hydrothermal system. Although sediment influences are a typical feature of Okinawan Trough hydrothermal fluids, the Hatoma hydrothermal system has the lowest carbon isotope ratios of CH4 among them, which suggests that Hatoma is the most highly influenced by the sediments in the recharge zone. Thus, the degree of the sediment influences has a variable in each hydrothermal field in the Okinawa Trough.

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琉球弧の地質とその成り立ち

新城竜一

ペドロジスト(日本ペドロジー学会誌) 60 47 - 54 2016年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

琉球弧の地質とその成り立ち

新城竜一

ペドロジスト ( 日本ペドロジー学会 ) 60 ( 1 ) 47 - 54 2016年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Response of Acropora digitifera to ocean acidification: constraints from δ11B, Sr, Mg and Ba compositions of aragonitic skeletons cultured under variable seawater pH

Tanaka, K, Holcomb, M, Takahashi, A, Kurihara, H, Asami, R, Shinjo, R, Sowa, K, Rankenburg, K, Watanabe, T, McCulloch, M

Coral Reef ( Coral Reefs ) 34 ( 4 ) 1139 - 1149 2015年12月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

The response of Acropora digitifera to ocean acidification is determined using geochemical proxy measurements of the skeletal composition of A. digitifera cultured under a range of pH levels. We show that the chemical composition (delta B-11, Sr/Ca, Mg/Ca, and Ba/Ca) of the coral skeletons can provide quantitative constraints on the effects of seawater pH on the pH in the calcification fluid (pH(CF)) and the mechanisms controlling the incorporation of trace elements into coral aragonite. With the decline of seawater pH, the skeletal delta B-11 value decreased, while the Sr/Ca ratio showed an increasing trend. The relationship between Mg/Ca and Ba/Ca versus seawater pH was not significant. Inter-colony variation of delta B-11 was insignificant, although inter-colony variation was observed for Ba/Ca. The decreasing trend of pH(CF) calculated from delta B-11 was from similar to 8.5, 8.4, and 8.3 for seawater pH of similar to 8.1, 7.8, and 7.4, respectively. Model calculations based on Sr/Ca and pH(CF) suggest that upregulation of pH(CF) occurs via exchange of H+ with Ca2+ with kinetic effects (Rayleigh fractionation), reducing Sr/Ca relative to inorganic deposition of aragonite from seawater. We show that it is possible to constrain the overall carbonate chemistry of the calcifying fluid with estimates of the carbonate saturation of the calcifying fluid (Omega (CF)) being derived from skeletal Sr/Ca and pH(CF) (from delta B-11). These estimates suggest that the aragonite saturation state of the calcifying fluid Omega (CF) is elevated by a factor of 5-10 relative to ambient seawater under all treatment conditions.

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沖縄トラフ海底熱水中のLi同位体比から導かれた海底下における固相側の情報について

土岐知弘, 平敷紗和子, 新城竜一, 石橋純一郎

日本地球化学会年会要旨集 ( 一般社団法人日本地球化学会 ) 62 ( 0 ) 4 2015年

掲載種別: 研究論文（研究会，シンポジウム資料等）

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δ11B, Sr, Mg and Ba in Acropora digitifera cultured under acidified seawater: Effects of seawater pH on trace element incorporation into coral aragonite

Tanaka, K, Holcomb M, Takahashi, A, Kurihara, H, Asami, R, Shinjo, R, Sowa, K, Rankenburg, K, Watanabe, T, McCulloch, M

Coral Reefs 2015年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

The geology of Okinawa-jima Island

Shinjo, R

Nature in the Ryukyu Archipelago: Coral Reefs, Biodiversity, and the Natural Environment 112 - 119 2015年

掲載種別: 研究論文（その他学術会議資料等）

Sr-Nd-Pb-Hf isotopic constraints on the diversity of magma sources beneath the Aden Ridge (central Gulf of Aden) and plume-ridge interaction

Shinjo R.

岩石礦物礦床學 ( 一般社団法人　日本鉱物科学会 ) 110 ( 3 ) 97 - 110 2015年

掲載種別: 研究論文（学術雑誌）

This paper presents new Sr–Nd–Pb–Hf isotopic compositions of tholeiitic basalts dredged along the Aden Ridge of the central Gulf of Aden (45.5°E–49°E). Two groups of basalts are identified based on their contrasting spatial distributions and geochemical signatures. Basalts dredged from east of 46.2°E (Group 1) are LREE–depleted but have relatively wide variations in 87Sr/86Sr (0.70278–0.70304) and 206Pb/204Pb (18.21–19.03) and limited 143Nd/144Nd (0.51301–0.51309) and 176Hf/177Hf ranges (0.283224–0.283276; εHf = 15.98–17.83), analogous to the geochemical signature of enriched to depleted normal mid–oceanic ridge basalts (N–MORB). In contrast, the basalts dredged between 45.6°E and 46.2°E (Group 2) are more enriched in incompatible elements [ocean island basalt (OIB)–like] but have little variation in 87Sr/86Sr (0.70323–0.70341), 206Pb/204Pb (19.33–19.49), and 143Nd/144Nd (0.51285–0.51292) and a wide variation in 176Hf/177Hf (0.283020–0.283155; εHf = 8.77–13.54). Isotopic and trace element variations can be attributed to the mixing of three types of mantle source: depleted MORB–type mantle (Component i), matrix mantle of the Afar plume (Component ii), and recycled oceanic crust (Component iii) occurring as blobs, streaks, or ribbons within the plume matrix. Mixing between Components i and ii would have produced Group 1 basalts, and Components ii and iii produced Group 2 basalts. Our data suggest that the Afar plume components were involved in magma genesis westward from 48°E in the Aden Ridge.

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Late Holocene coral reef environment recorded in Tridacnidae shells from archaeological sites in Okinawa-jima, subtropical southwestern Japan

Asami R, Konishi M, Tanaka K, Uemura R, Furukawa M, Shinjo R

Island Arc ( Island Arc ) 24 ( 1 ) 61 - 72 2015年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Seasonally resolved records of carbon and oxygen isotopic composition (δ18O) in fossil shells of giant clams (Tridacnidae) recovered from the Kogachibaru Shell Mound (26°26'N, 127°49'E) and the Second Aragusuku-Shichabaru Ruin (26°18'N, 127°46'E) in Okinawa-jima, southwestern Japan, were investigated to reconstruct subtropical coral reef environments of the past. The samples, mainly composed of aragonite shells with limited amounts of diagenetically-altered calcite cements, were selected for geochemical analyses. The radiocarbon dating of the samples for stable isotope analyses yields about 4000yr cal. BP for the Kogachibaru Shell Mound and about 1900-1700yr cal. BP for the Second Aragusuku-Shichabaru Ruin, respectively, that correspond to the early and middle Shell Mound periods in Okinawa-jima. These show good agreement with the respective ages inferred from excavation. The shell δ18O values roughly show seasonal variations, coincident with the occurrence of annual growth bands. Applying corrections for the effect of diagenetic alteration, the averages of annual, summer, and winter δ18O values of fossil shells were significantly lower (by 0.1-0.7‰) than those of aragonite theoretically precipitated in present-day coral reef water of Okinawa-jima. These results demonstrate that annual mean seawater temperature and salinity at the sites where the Tridacnida spp. lived were about 1-3°C higher and/or about 1-2 lower than at present. This variation cannot be fully explained by global climate change, sea level change, and topographic growth of coral reef. Therefore, it is likely that the giant clams lived in extremely small and/or closed coral-reef lagoons with less water circulation where seawater is highly susceptible to insolation-induced temperature increase and input of fresh water; the effect could be enhanced by the fisheries lifestyle that stonewalling would be constructed at shallow waters through the use of tidal variation during the early and middle Shell Mound period in Okinawa-jima.

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Improved method for seawater lithium isotopic ratio determination using MC-ICP-MS

新城竜一

Bulletin of the Society of Sea Water Science, Japan 69 326 - 331 2015年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

関連情報を調べる

CiNii Research

Data report: Boron isotope ratios in interstitial waters from Sites C0021 and C0022

Toki, T, Higa, K, Shinjo, R

Proceedings of the Integrated Ocean Drilling Program 338 2015年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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Damage zone propagation and support pressure estimation around two access tunnels of the Barapukuria coal mine in Bangladesh: a two-dimensional numerical modeling approach

Rafiqul, M. I, Faruque, M. O, Shinjo, R

International Journal of Advanced Geosciences 3 14 - 24 2015年 [ 査読有り ]

掲載種別: 研究論文（その他学術会議資料等）

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沖縄島の地質と成り立ち

新城竜一

琉球列島の自然講座サンゴ礁・島の生き物たち・自然環境 150 - 159 2015年

掲載種別: 研究論文（その他学術会議資料等）

Determination of rare earth elements in small-volume seawater by off-line preconcentration system and inductively coupled plasma mass spectrometry

Shinjo　Ryuichi,

No.92 (2011/9) ( 琉球大学理学部 ) ( 92 ) 17 - 22 2011年11月

掲載種別: 研究論文（大学，研究機関紀要）

An analytical method was developed for determining rare earth element (REE) concentrations in seawater using inductively coupled plasma mass spectrometry (ICP-MS). A relatively small-volume seawater sample (25 ml) was used for chemical separation. REE concentrations in 20-fold preconcentrated solution by an off-line preconcentration system were analyzed by ICP-MS with microflow nebulizer. The recoveries were mostly higher than 95%. To assess the analytical method, REE concentrations of the North Atlantic Surface Seawater (NASS-5), a seawater certified reference material, were measured with the proposed preconcentration procedure. Results obtained in this study are consistent with those of previous studies with good precision. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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The tectonic stress field and deformation pattern of northeast India, the Bengal basin and the Indo-Burma Ranges: A numerical approach

Islam, M.S., Shinjo, R. and Kayal, J.R.

Journal of Asian Earth Sciences ( その他の出版社 ) 40 121 - 131 2011年

掲載種別: 研究論文（学術雑誌）

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Pop-up tectonics of the Shillong Plateau in northeastern India: Insight from numerical simulations

Islam, M.S., Shinjo, R., Kayal, J.R.

Gondwana Research ( その他の出版社 ) (in press) 2011年

掲載種別: 研究論文（学術雑誌）

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Extracellular Matrix Protein in Calcified Endoskeleton: A Potential Additive for Crystal Growth and Design

Rahman, M.A., Fujimura, H., Shinjo, R. and Oomori, T.

Journal of Crystal Growth ( その他の出版社 ) (in press) 2011年

掲載種別: 研究論文（学術雑誌）

Geochemistry and geochronology of the mafic lavas from the southeastern Ethiopian rift (the East African Rift System): Assessment of models on magma sources, plume-lithosphere interaction and plume evolution

Shinjo, R., Chekol, T., Meshesha, D., Itaya, T. and Tatsumi, Y.

Contributions to Mineralogy and Petrology ( その他の出版社 ) (in press) 2011年

掲載種別: 研究論文（学術雑誌）

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New supplemental activator for lead isotope analysis with TIMS

Nohda, S., Wang, B.-S., You, C.-F. and Shinjo, R.

Geochemical Journal ( その他の出版社 ) (in press) 2011年

掲載種別: 研究論文（学術雑誌）

Barite geochemistry from hydrothermal chimneys of the Okinawa Trough: insight into chimney formation and fluid/sediment interaction

Noguchi, T., Shinjo, R., Ito, M., Takada, J. and Oomori, T.

Journal of Mineralogical and Petrological Sciences ( その他の出版社 ) 106 26 - 35 2011年

掲載種別: 研究論文（学術雑誌）

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Report on RN97 Cruise by T/S Nagasaki Maru in the Southern Okinawa Trough

Motoyama　Isao,Nakamura　Mamoru,Takaki　Yasuaki,Nishida　Hideaki,Morii　Yasuhiro,Tanaka　Hitoshi

No.65 (1998/3) ( 琉球大学理学部 ) ( 65 ) 39 - 51 2010年02月

掲載種別: 研究論文（大学，研究機関紀要）

As a part of the educational cruise (RN97 Cruise) for students of College of Science, University of the Ryukyus, by T/S Nagasaki Maru, the scientific survey is carried out during November 15 to 24, 1997. We dredge seafloor samples at several seaknolls which locate in the southern Okinawa Trough. Pumices and dacitic lava fragments are dredged. The rocks are quite fresh, and thus appear to be Quaternary eruptives, confirming the presence of continuous volcanic front from the northern Ryukyu Arc to the southern Ryukyu Arc. Surface sediment type varies depending on depositional settings. Sediments recovered by a grab sampler are composed of quartz sand in the continental shelf, biogenic calcareous sand in the Hokuto-Sekibi Bank and the Ryukyu Ridge, and mud in the Okinawa Trough. The radiolarian assemblage from the surface sediment sample in the Okinawa Trough is characterized by warm water species in accord with the oceanographic setting. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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Hafnium isotope variations in Bure volcanic rocks from the northwestern Ethiopian volcanic province: a new insight for mantle source diversity

Meshesha, D. and Shinjo, R.

Journal of Mineralogical and Petrological Sciences ( その他の出版社 ) 105 101 - 111 2010年

掲載種別: 研究論文（学術雑誌）

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Neotectonic stress field and deformation pattern within the Zagros and its adjoining area: An approach from finite element modeling

Islam, M.S. and Shinjo, R.

Journal of Geology and Mining Research ( その他の出版社 ) 2 170 - 182 2010年

掲載種別: 研究論文（学術雑誌）

Improved method for Hf separation from silicate rocks for isotopic analysis using Ln-spec resin column

Shinjo, R., Ginoza, Y. and Meshesha, D.

Journal of Mineralogical and Petrological Sciences ( その他の出版社 ) 105 297 - 302 2010年

掲載種別: 研究論文（学術雑誌）

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Submarine active normal faults completely crossing the southwest Ryukyu Arc

Matsumoto, T., Shinjo, R., Nakamura, M., Kimura, M. and Ono, T.

Tectonophysics ( その他の出版社 ) 466 289 - 299 2009年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Mining-induced fault reactivation associated with the main Conveyor Belt Roadway and safety of the Barapukuria Coal Mine in Bangladesh: constraints from BEM simulations

Islam, M.R. and Shinjo, R.

International Journal of Coal Geology ( その他の出版社 ) 79 115 - 130 2009年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Numerical simulation of stress distributions and displacements around an entry roadway with igneous intrusion and potential sources of seam gas emission of the Barapukuria coal mine, NW Bangladesh

Islam, M.R. and Shinjo, R.

International Journal of Coal Geology ( その他の出版社 ) 78 249 - 262 2009年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Submarine, across-arc normal fault system in the southwest Ryukyu arc triggered the 1771 tsunami hazard?: field evidences from multibeam survey and in-situ observation by ROV

Matsumoto, T., Shinjo, R., Nakamura, M., Doi, A., Kimura, M., Ono, T. and Kubo, A.

Polish J. Environ. Stud. ( その他の出版社 ) 18 123 - 129 2009年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Geology and Petrology of the Nishi and Fudenzaki Formations of the Aguni Group, Aguni Island, the Central Ryukyu Arc : Petrogenetic Relationship between the Andesites and Dacites

Usami　Ken,Kato　Yuzo

No.60 (1995/9) ( 琉球大学理学部 ) ( 60 ) 27 - 50 2008年03月

掲載種別: 研究論文（大学，研究機関紀要）

The late Miocene volcanic rocks of the Aguni Group range from basalt to rhyolite, and have a pronounced compositional gap between 57 and 69 wt.% SiO_2. Sr isotopic ratios for a dacite lava from the Nishi Formation (0.70463) and a gabbroic fragment from the Fudenzaki Formation (0.70455) are similar to those of the basalt-andesite suite (0.70452-0.70466). Both major- and trace-element variations from andesite to dacite are explainable in terms of fractional crystallization involving removal of the observed phenocryst phases in the evolved volcanic rocks. The Rare Earth Elements (REE) patterns of gabbroic fragments appear to coincide with the pattern of cumulate expected from fractional crystallization. A shallow composition-temperature slope of cotectic involving amphibole-bearing gabbroic assemblages is responsible for the development of bimodality between the andesites and dacites. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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Petrology and petrogenesis of volcanic rocks from the Uegusukudake Formation in Kume-jima, central Ryukyu Arc

Shinjo　Ryuichi,Kato　Yuzo

No.77 (2004/3) ( 琉球大学理学部 ) ( 77 ) 81 - 103 2008年03月

掲載種別: 研究論文（大学，研究機関紀要）

Major and trace element concentrations and Sr and Nd isotopic ratios are presented for volcanic rocks from the Uegusukudake Formation (～$3-2 Ma) in Kume-jima, central Ryukyu Arc, in order to understand the origin of varieties of erupted magmas. The Uegusukudake Formation is mainly composed of lavas and pyroclastic rocks with subordinate dikes. Volcanic rocks collected from lavas and dikes are grouped into four types based on their petrological characteristics: (1) picrite basalt (PB); (2) aphyric, tholeiitic basalt and basaltic andesite (A-TH); (3) porphyritic, tholeiitic basaltic andesite (P-TH); and (4) porphyritic, calc-alkaline basaltic andesite and andesite (CA), in ascending order. The PB sample is isotopically distinct in having significantly low ^<87>Sr/^<86>Sr (0.7035) and high ^<143>Nd/^<144>Nd (0.51290) compared with the other three types. The A-TH, P-TH, and CA types have similar isotopic compositions (^<87>Sr/^<86>Sr=0.7045-0.7054, ^<143>Nd/^<144>Nd=0.51270-0.51284) and show rather coherent incompatible trace element patterns. These results suggest that the three types of magmas were derived from a similar source material, distinctive from the source of the PB magma. A slight difference in isotopic and trace element ratios (La/Sm and La/Yb) among the three types can be attributed to the different degree of contributions of crustal assimilation. Geochemical variations within the A-TH type rocks can be explained by fractional crystallization, and the variation of the CA type is considered to have resulted from internal hybridization within a single magma reservoir. For the variation of the P-TH type, plagioclase accumulation is inferred to have played a dominant role. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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Petrochemical evidence for diversity of magma compositions at the northwestern Ethiopian volcanic province

Shinjo　Ryuichi,

No.78 (2004/9) ( 琉球大学理学部 ) ( 78 ) 251 - 266 2008年03月

掲載種別: 研究論文（大学，研究機関紀要）

Petrographic characteristics and whole-rock major and trace element data are presented for the Bure volcanic rocks from the northwestern Ethiopian plateau of East Africa continental flood basalt province, to investigate the processes that involved in the genesis of the erupted magma and its source composition during plume-induced continental rifting. The Bure area is mainly composed of stratified basalts, recent basalts, scoria cones and trachyte plugs. The successions of the erupted basalts are from transitional tholeiites to alkaline basalts. The transitional tholeiites have higher Zr/Nb (8.88-21.86) and Rb/Nb (0.66-1.87) than those of the alkaline (Zr/Nb=2.19-6.21, Rb/Nb=0.26-0.74), indicating that they are originated from distinct magma sources. The compositional variation in the transitional tholeiites cannot be explainable in terms of fractional crystallization of common (or similar) primary magma; instead it reflects the involvement of various mantle and crustal components in their petrogenesis. By contrast, the variation in the alkali suite can be explained by dominant fractional crystallization process of OIB-like primary basalts that derived from the Afar mantle plume. The strong lithospheric signature observed in the transitional tholeiites suggests pronounce interaction between the Afar plume and the lithosphere at the initial stage of continental break-up. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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蛍光Ｘ線分析装置（XRF）による1：5希釈ガラスビードを用いた全岩主成分・微量成分元素の定量分析

宮本　正雪,

No.84 (2007/10) ( 琉球大学理学部 ) ( 84 ) 5 - 13 2008年03月

掲載種別: 研究論文（大学，研究機関紀要）

Analytical results of major and trace elements（Ba, Co, Cr, Nb, Ni, Rb, Sr, V, Y, and Zr) for bulk rocks by XRF using 1:5 dilution glass bead were evaluated. Analytical conditions and protocol are also reported. The results show relatively good accuracy and precision for major and trace elements. This method could be suitable to basalts to andesites, with error <$pm$3% for major elements and <$pm$10% for trace elements. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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Geology of the Shar and Bulen areas, northwestern Ethiopia: Preliminary result

Negussie　Aweke,Shinjo　Ryuichi

No.79 (2005/3) ( 琉球大学理学部 ) ( 79 ) 27 - 42 2008年03月

掲載種別: 研究論文（大学，研究機関紀要）

Geological assessment of Shar and Bulen areas, northwestern Ethiopia indicates distinctive rock associations consisting of pelitic and pssamitic sediments that are interbedded with volcanic rocks and linear belt of mafic-ultramafic rocks. These volcano-sedimentary associations signify interchanges of sedimentary process and volcanic activity. Deposition is interpreted to have occurred within a marginal to shallower marine setting. The rocks were subjected to different phases of deformation and were metamorphosed to greenschist facies. Structural investigation indicates that the area underwent at least three phases of deformation (D_1-D_3) with pre-, syn- and post- kinematic granitic intrusions. The volcano-sedimentary association together with mafic-ultramafic rocks can be interpreted as an arc/continent suture zone. （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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那覇市の河川及び沿岸堆積物の起源と人為的影響

与那覇寛, 藤田和彦, 新城竜一

日本サンゴ礁学会誌 ( その他の出版社 ) 10 1 - 21 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Data report: Pb isotope compositions of sediment from the eastern flank of Juan de Fuca Ridge

Noguchi, T., Shinjo, R. and Oomori, T.

Proc. IODP, 301: College Station, TX ( その他の出版社 ) 301 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Rethinking geochemical feature of the Afar and Kenya mantle plumes and geodynamic implications

Meshesha, D. and Shinjo, R.

J. Geophys. Res. ( その他の出版社 ) 113 B09209 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Propagators and ridge jumps in a back-arc basin, the West Philippine Basin

Deschamps, A., Shinjo, R., Matsumoto, T., Lee, C.-S., Lallemand, S.E., Wu, S. and Scientific party of KR03-04 and KR04-14 cruises

Terra Nova ( その他の出版社 ) 20 327 - 332 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Was there Jurassic paleo-Pacific subduction in South China?: Constraints from 40Ar/39Ar dating, elemental and Sr-Nd-Pb isotopic geochemistry of the Mesozoic basalts

Chen, C.H., Lee, C.Y. and Shinjo, R.

Lithos ( その他の出版社 ) 106 83 - 92 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Origin of sapphirine-bearing garnet-orthopyroxene granulites: possible hydrothermally altered ocean floor

Baba, S., Shinjo, R. and Windley, B.F.

Polar Science ( その他の出版社 ) 2 87 - 107 2008年 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Crustal contamination and diversity of magma sources in the northwestern Ethiopian volcanic province

Meshesha, D. and Shinjo, R.

J. Mineral. Petrol. Sci. ( その他の出版社 ) 102 272 - 289 2007年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Determination of uranium in pore water from coastal sediment by standard addition ICP-MS analysis

Armid, A., Ohde, S., Shinjo, R. and Toki, T.

J. Radioanal. Nucl. Chem. ( その他の出版社 ) 275 233 - 237 2007年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Chemical impact of the acidic red soil on seawater

Kombo, M.M., Bakari, S.S., Shinjo, R. and Tokuyama, A.

Galaxea, JCRS ( その他の出版社 ) 8 13 - 23 2006年04月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Petrology of Aoso volcano, northeast Japan arc: temporal variation of the magma feeding system and nature of low-K amphibole andesite in the Aoso-Osore volcanic zone.

Toya, N., Ban, M. and Shinjo, R.

Contrib. Mineral. Petrol.DOI 10.1007/s00410-004-0621-z. ( その他の出版社 ) 148 566 - 581 2005年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

Geochemical constraints for the genesis of post-collisional magmatism and the geodynamic evolution of the northern Taiwan region.

Wang, K.-L., Chung, S.-L., O'Reilly, S.Y., Sun, S.-S., Shinjo, R. and Chen, C.-H.

J. Petrol. ( その他の出版社 ) 45 975 - 1011 2004年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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琉球列島四万十帯中の現地性緑色岩の産状と化学組成.

知念正昭, 新城竜一, 加藤祐三

岩石鉱物科学 ( その他の出版社 ) 33 208 - 220 2004年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China: Partial melting of delaminated lower continental crust?

Xu, J.-F., Shinjo, R., Defant, M.J., Wang, Q. and Rapp, R.P.

Geology ( その他の出版社 ) 30 1111 - 1114 2002年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Fluid bubbles in melt inclusions and pillow-rim glasses: high-temperature precursors to hydrothermal fluids?

Kamenetsky, V.S., Davidson, P., Mernagh, T.P., Crawford, A.J., Gemmell, J.B., Portnyangin, M.V. and Shinjo, R.

Chem. Geol. ( その他の出版社 ) 183 349 - 364 2002年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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中琉球弧久米島宇江城岳層の玄武岩質安山岩の全岩K-Ar年代.

北川宙, 新城竜一

岩石鉱物科学 ( その他の出版社 ) 30 237 - 240 2001年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Chemical characteristics of newly discovered black-smoker fluids and associated hydrothermal plumes at the Rodriguez Triple Junction, Central Indian Ridge.

Gamo et al.

Earth Planet. Sci. Lett. ( その他の出版社 ) 193 371 - 379 2001年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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JNdi-1: a neodymium isotopic reference in consistency with LaJolla neodymium.

Tanaka, T., Togashi, S., Kamioka, H. et al. (incl. Shinjo, R.)

Chem. Geol. ( その他の出版社 ) 168 279 - 281 2000年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Geochemical variation within the northern Ryukyu Arc magma source compositions and geodynamic implications.

Shinjo, R., Woodhead, J.D. and Hergt, J.M.

Contrib. Mineral. Petrol. ( その他の出版社 ) 140 263 - 282 2000年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Geochemical constraints on the origin of bimodal magmatism at the Okinawa Trough, an incipient back-arc basin.

Shinjo. R., Kato. Y.

Lithos ( その他の出版社 ) 54 117 - 137 2000年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Initiation of arc magmatism in an embryonic continental rifting zone of the southernmost part of Okinawa Trough.

Chung, S.-L., Wang, S.-L., Shinjo, R., Lee, C.-S. and Chen, C.-H.

Terra Nova ( その他の出版社 ) 12 230 - 255 2000年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Geochemistry of high Mg andesites and the tectonic evolution of the Okinawa Trough-Ryukyu arc system.

Shinjo. R.

Chem. Geol ( その他の出版社 ) 157 69 - 88 1999年03月 [ 査読有り ]

掲載種別: 研究論文（学術雑誌）

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Post-collisional magmatism around northern Taiwan and its relation with opening of the Okinawa Trough.

Wang. K.-L, Chung, S.-L., Chen, C.-H., Shinjo, R., Yang, T.F. and Chen, C.-H.

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Geochemical and Sr-Nd isotopic characteristics of volcanic rocks from the Okinawa Trough and Ryukyu Arc:Implications for the evolution of a young, intracontinental back arc basin.

Shinjo. R, Chung, S.-L., Kato, Y. and Kimura, M.

J. Geophys. Res. ( その他の出版社 ) 104 10591 - 10608 1999年03月 [ 査読有り ]

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J. Volcanol. Geotherm. Res. ( その他の出版社 ) 80 39 - 53 1998年03月 [ 査読有り ]

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琉球弧に産する高Mg安山岩および尖閣諸島の火山岩のK-Ar年代

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掲載種別: 研究論文（学術雑誌）

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