Ryuichi Shinjo

Ryuichi Shinjo
University of the Ryukyus · Department of Physics and Earth Sciences

PhD

About

158
Publications
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Publications

Publications (158)
Article
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The Sawlava ophiolite is situated on the Iran–Iraq border within the Walash-Kermanshah ophiolitic belt and represents remnants of the Cenozoic southern Neo-Tethys Ocean, which was located between the Arabian plate and the Sanandaj–Sirjan zone. It contains a complete ophiolitic sequence started from harzburgites with foliated/discordant dunites, gab...
Article
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), i...
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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...
Article
Metal lead constitutes one of the major elements of the common historic firearm’s bullets. Since their early development in Medieval China, lead bullets in combination with gunpowder have been consistently used in historical wars worldwide. The increasing demand to produce lead bullets peaked during the 19th century when multiple wars were happenin...
Article
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. C...
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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 (δ ¹³ C and δ...
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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...
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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...
Article
The late Cenozoic geohistory of the Ryukyu arc is closely related to the rifting history of the Okinawa Trough. The submarine geology and stratigraphy of areas around Kume Island, which is situated near the eastern rifted margin of the middle Okinawa Trough, provide key constraints to understand the timing and mode of Okinawa Trough rifting. Here w...
Article
Amphibole plays an important role in arc-related magma differentiation. This relates to the fact that it contains a variety of elements and volatiles, and because it is one of the main minerals comprising the lower crust. Pliocene-Pleistocene Yoneyama volcanic rocks (northern Fossa Magna, central Japan) show a high-K sub-alkalic composition, and pa...
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In the Hamadan region, Sanandaj-Sirjan Zone (SaSiZ), W Iran, a pegmatite-aplite vein occurs that contains up to 15 vol% sapphire. The Hamadan sapphire is black to blue, and translucent to opaque, which reveals its semi-gem and gem quality. On the basis of petrographic studies, the Hamadan sapphire-bearing pegmatite-aplite vein represents alkali sye...
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Staring Bay has long been used by the local community for fisheries and fishing activities; however, the rapid population growth and industrial activities around the bay in recent years are predicted to contribute significantly to the increase of waste entering the bay. This particular study was aimed to provide baseline levels of trace elements Pb...
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Plain Language Summary Although sediments and stalagmites play a leading role in Quaternary paleoclimate studies, the slow rates of sedimentation frequently preclude from climate reconstruction on a seasonal or interannual timescale. From geochemical records of fossil corals in Okinawa, Japan, we first reconstructed a >50‐year‐long bimonthly time s...
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Esna-Ashari and Tiepolo (2020) provide new mineral chemistry data for some samples from the previously reported outcrop of mafic plutonic rocks from the northwestern part of the Malayer-Boroujerd Plutonic complex (MBPC in Deevsalar et al., 2017), which they referred to as MPC. In this paper, they proposed an oversimplified petrogenetic model, in wh...
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The geochemistry of the calcium carbonates of marine organisms is an excellent proxy for reconstruction of the paleoceanographic history. However, previous studies of hypercalcified demosponges (sclerosponges) are considerably fewer than those of corals, foraminifers, and bivalves. Here, we investigated stable oxygen (δ18O) and carbon (δ13C) isotop...
Article
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 p...
Article
Major and trace element and Nd–Hf isotopic compositions of Paleoproterozoic meta‐igneous rocks from the lower part of the Lesser Himalayan sequence provide insights into the nature of their source mantle and its tectonic setting. We observed bimodal (basaltic and rhyolitic) magmatic compositions in these rocks; this type of volcanism generally occu...
Article
Damavand is a Quaternary stratovolcano in N Iran, associated with small volumes of under-saturated to weakly-saturated mafic lavas (Tephrite-Basanite-Alkali olivine basalt), and large volumes of saturated lavas (trachyandesite-trachyte (TT)) together with minor pyroclastic rocks. TT rocks are characterized by LILE and HFSE enrichments, whereas the...
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This paper presents review of dissolved Rare Earth Elements (REE) and methane anomalies distribution in the East China Sea water column. In general, the REE concentrations of the shelf water are markedly higher than those of Okinawa Trough water in the East China Sea. Rare earth elemental concentrations in the Okinawa Trough water mainly governed b...
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Biotite is the most frequent ferromagnesian phase in granitoids from the Malayer-Boroujerd Plutonic complex (MBPC), Zagros Orogen. The abundance of biotite decreases from granitoids towards dioritic intrusions, dioritic and gabbroic dykes to gabbroic intrusions coincident with increase in hornblende/biotite ratio. Primary magmatic biotite compositi...
Article
Basaltic and related- pyroclastic products aged 0.67, 0.46 and 0.2 Ma produced by eruption of Chư B'luk (Buon Choah), Phu Son (Pass 52, Quang Phu) volcanoes in the Krông Nô district, and Ea T’ling and Nam Dong volcanoes in the Cu Jut district covers an area of 120 km2 with a thickness of a few meters to about 80 m. The volcanoes are aligned along a...
Article
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...
Article
A set of 72 low-volume seawater samples (25 mL) collected from 9 stations in the East China Sea in 2009 and 2011 is analyzed for dissolved rare earth element (REE) concentrations. The elemental concentrations in continental shelf waters are markedly higher than those from the shelf slope and Okinawa Trough waters. The transition in the REE concentr...
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The Sanandaj–Sirjan Zone (SaSiZ) is a magmatic terrane within the Zagros Orogen, western Iran, marking the Tethyan suture zone between the Afro-Arabian Plate and the Central Iran Micro-Continent. Mafic–intermediate dyke swarms with Middle Jurassic (Group 1: hornblende gabbro and diorite) and Late Eocene (Group 2: hornblende–pyroxene gabbro) ages ar...
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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 zon...
Article
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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 gabbroi...
Article
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...
Article
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 volca...
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The concentrations of heavy metals Pb, Cd and Cr in the coastal waters of Kendari Bay were analyzed to assess their pollution status. Water samples from 32 sampling points were analyzed for dissolved heavy metals concentrations by using inductively coupled plasma mass spectrometry (ICP-MS). The RSD(%) of each metal was accounted to analyze the dive...
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The concentration and pollution level of heavy metals in the surface sediments of Kendari Bay, Indonesia were measured. Sediments samples from 25 sites, ranging from the inshore (Wanggu River) to the offshore regions of the bay, were analysed for metal concentrations (i.e., Mn, Fe, Co, Ni, Cu and Zn), sediment type and TOC. The results demonstrate...
Article
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-e...
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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 act...
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In order to provide information on the chemical processes in sediment fractions and their adsorption models, we investigated the contaminated sediments of the Sumida River in Tokyo, Japan and the Chao Phraya River in Bangkok, Thailand. Samples were leached through a sequential leaching technique to perform metal concentration analysis for the sedim...
Article
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We developed a simple, accurate, and sensitive analytical method for determination of the lithium isotopic ratio of seawater, using a multi-collector ICP mass spectrometer(MC-ICP-MS). The method involves a single-step column separation, and improvements in sensitivity and precision are achieved by the use of an X-type skimmer cone and relatively lo...
Article
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 (δ¹¹B) of pore fluids samp...
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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...
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The present study uses a two-dimensional boundary element method (BEM) numerical analysis to predict damage zone propagation associated with the required support pressure estimation around the two access tunnels of Barapukuria coalmine in northwest Bangladesh. Two tunnels at different depths are presented here. The stability of the two tunnels that...
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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 (δ11B, Sr/Ca, Mg/Ca, and Ba/Ca) of the coral skeletons can provide quantitative constraints on the effects of seawater p...
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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...
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In this study, mineralogical, geochemical, and isotopic data are presented for the Sylhet Trap at the southern flank of the eastern Shillong Plateau, northeastern India, to determine the magma genesis in relation to the Kerguelen plume mantle source. Sylhet Trap rocks are porphyritic tholeiite and have diverse chemical compositions from picro-basal...
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The geochemical characteristics of mantle xenoliths (spinel lherzolites) in Quaternary alkaline basalts from the northwestern Ethiopian plateau provide new insight into the conditions of melting associated with the Afar plume. The major element compositions of the spinel lherzolites are in the range of those of the primitive mantle. The high modal...
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The Japanese red and pink corals are known to be precious because of their commercial value resulting from their use in ornaments, jewelry, and medicine. Precious corals are very interesting models for biomineralization studies and possess two different skeletal structures: an axial skeleton and an endoskeleton (sclerites). Although it has long bee...
Article
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 environmen...
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Mafic magmatism, such as exposed in the Malayer-Boroujerd plutonic complex (MBPC), is rare in the northern part of the Sanandaj-Sirjan Magmatic Zone (N-SSMZ), Iran. The MBPC mafic rocks are volumetrically dominated by gabbro to gabbro-diorite and troctolite gabbro which can be separated geochemically into a suite of low Mg# - high Zr dykes (L-H maf...
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Geological characteristics of the Ryukyu Island Arc are overviewed and geology and its development of Okinawa Island in Central Ryukyus are described. Ryukyu Arc extends for ∼1200 km from Kyushu to Taiwan, which has been divided into three segments (North, Central, and South Ryukyus) with tectonic boundary of the Tokara Strait in the north and Kera...
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An organic matrix consisting of a protein-polysaccharide complex is generally accepted as an important medium for the calcification process. While the role this "calcified organic matrix" plays in the calcification process has long been appreciated, the complex mixture of proteins that is induced and assembled during the mineral phase of calcificat...
Article
We generated a 5.5-yr snapshot of biweekly-to-monthly resolved time series of carbon and oxygen isotope composition (δ13C and δ18O) and Sr/Ca and Mg/Ca from annually banded aragonite skeleton of a ~ 197 ka pristine Porites coral collected at Niue Island (19°00′S, 169°50′W) in the southwestern subtropical Pacific Ocean. This report is the first of a...
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Based on whole-rock chemical compositions of sandstone and greenstone, we estimate the geologic provenance and tectonic setting of pre-Neogene basement rocks of Okinawa Island and neighboring islands. Our results suggest that sandstone clasts in the Iheya Unit were derived from a continental arc and dissected arc, whereas sandstone clasts in the Mo...
Article
Ocean acidification caused by anthropogenically elevated CO2 concentration in the atmosphere can pose a critical threat to calcifying marine organisms and coral reef ecosystems. However, because of temporally and spatially limited instrumental pH records, little is known about the actual long-term trend and natural variability of seawater pH during...
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Basic volcanic rocks from the West Nain area of the Urumieh–Dokhtar Magmatic Assemblage demonstrate significant subduction-related geochemical characteristics; these along with the new age data obtained for the volcanic rocks shed new light on the geodynamic evolution of the Iranian segment of Alpine–Himalayan orogeny. The late Oligocene (26.5 Ma)...
Data
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The parent ion on the spectra of Thioredoxin (red arrow). (PDF)
Data
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The parent ion of actin. (A, B) The parent ion on the spectra (red arrows). (PDF)