Published Papers - SHINJO Ryuichi

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   2025.06 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2025.04 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2025.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Discovery of a Pumice Deposit from the 1924 Iriomote Submarine Volcanic Eruption on the Northeastern Coast of Ishigaki Island

Usami, K., Kato, Y., Shinjo, R., Niiyama, S.

Bull. Mus., Okinawa Pref. Mus. Art Mus.   ( 18 ) 1 - 8   2025.03

Type of publication: Research paper (bulletin of university, research institution)

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   2024.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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"<SUP>1</SUP>

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

HYDROLOGICAL SCIENCES JOURNAL ( Hydrological Sciences Journal )    2024.08 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2024.02 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2024.02 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Petrology of the Miocene Tomari volcanic rocks in the SN-010 deep core from the Shimokita Peninsula in northern Japan and its correlation to the surface geology

Aizawa Masataka, Inaba Mitsuru, Okamura Satoshi, Shinjo Ryuichi

The Journal of the Geological Society of Japan ( The Geological Society of Japan )  129 ( 1 ) 587 - 602   2023.12 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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<p>The Tomari volcanic rocks were products of the Middle Miocene volcanic front of the NE Japan arc. The volcanic activity has been divided into four stages with five lithologies, as assessed from surface geology. Eruptive rocks of Stage I (oldest) are the Kanatsuyama Andesite, the lower and upper units of Stage II are the Gassan Andesite and Tomari Basalt, respectively, Stage III comprises the Takahoko Andesite, and Stage IV is the Fukkoshi Andesite. Coring investigation was conducted on the northwestern side of the exposed Tomari volcanic rocks on central Shimokita Peninsula, Aomori Prefecture, in the northern NE Japan arc during 2014–2016. In the SN-010 core, the Tomari volcanic rocks occur from the bottom of the core at 1484 m below the surface to 308 m below the surface; the lower boundary of the volcanic rocks was not penetrated in the SN-010 borehole. We collected eight samples from the core and described their petrological characteristics to correlate the volcanic stages of the Tomari volcanic rocks between the core and surface geology.</p><p>Modal compositions, especially abundant olivine phenocrysts and the occurrence of chromium-spinel, define the Tomari Basalt as a rock with a unique signature within the exposed Tomari volcanic rocks. The Tomari Basalt includes a primitive basalt characterized by high whole-rock contents of MgO, Cr, and Ni compared with the other Tomari volcanic rocks. The SN-010 core samples at a depth of ~1003 m have similar petrological characteristics to those of the Tomari Basalt, except that olivine phenocrysts in the core samples are perfectly altered.</p><p>LILE/HFSE ratios, such as Ba/Nb, change below 1197.86 m (deep core samples) and above 1003.35 m (shallow core samples) in the SN-010 core. Ratios for shallow core samples are similar to those for surface samples. HFSE/HFSE ratios, such as Zr/Nb, show similar values among deep, shallow, and surface samples, indicating a cognate source mantle. These findings imply changes in the slab-derived component during magma generation associated with the opening of the Japan Sea.</p>

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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   2023.11 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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<p>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。</p>

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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   2023.10 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2023.09 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2023.04 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2023.04 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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 )   2023.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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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   2023.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Temporal variation in amount and size of the drift pumice from the 2021 eruption of Fukutoku-Oka-no-Ba submarine volcano: an example from the Tenjin-jima, Kanagawa Prefecture, central Japan

Shibata, K, Kohase, M, Shinjo, R

Sci. Rept. Yokosuka City Mus.   ( 70 ) 39 - 51   2023.03

Type of publication: Research paper (bulletin of university, research institution)

Development of a Simple Elemental Analysis Method for Pumices Derived from the 2021 Fukutoku-Oka-no-Ba Submarine Eruption Using μ-XRF: Implications to Earth Science

Nakano, H, Shinjo, R, Komatai, S

Adv. X-Ray. Chem. Anal., Japan   54   203 - 216   2023.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

Occurrence and Detrital Zircon U-Pb Dating of Sandstones in the Shimanto Belt of the Kerama Islands

Bulletin of the Museum, Okinawa Prefectural Museum and Art Museum   ( 16 ) 1 - 11   2023.03

Type of publication: Research paper (other science council materials etc.)

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   2023.02 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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