Ryuichi Shinjo

University of the Ryukyus · Department of Physics and Earth Sciences

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 Ti...

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 Ti...

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 lim...

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 B...

This research presents the first quantitative analysis using the boron isotope in groundwater to study environmental contamination in the Quaternary limestone aquifers of the southern region of Okinawa Island. Due to the direct discharge of wastewater from human activities into the groundwater, monitoring water quality is of primary concern in this...

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 c...

Download full paper from here: https://www.tandfonline.com/eprint/R2QCDTSBCFQKAMHQ4PPA/full?target=10.1080/02626667.2023.2252406

The late Proterozoic - early Paleozoic tectono-magmatic evolution of Central Iran is considered to be a result of subduction of the Proto-Tethys Ocean and the amalgamation of Gondwana continental fragments. Here, we present whole-rock geochemistry, Sr-Nd-Pb isotopes and zircon U-Pb-Hf data for monzonite to quartz monzonite from deep drill core in t...

Late Precambrian–Early Paleozoic igneous rocks constitute volumetrically minor components of the Iranian Plateau but preserve important information about the magmatic and tectonic history of the northern Gondwana margin. The Chadormalu intrusions are part of Central Iran, which includes Late Precambrian–Early Paleozoic continental crust that is now...

The Choghart and Chadormalu iron deposits in Bafq metallogenic zone in Central Iran are classified as Kiruna-type deposits and surrounded by metasomatic rocks which Russian experts named them metasomatite. These rocks include different types of acidic to mafic igneous rocks and sediment and metamorphic rocks known as metasomatic bedrocks. The enric...

Anomaly 21A, as a part of Bafq iron-apatite ore metallogenic district, is located in Central Iran, and encompasses wide spectrum of igneous, sedimentary and metamorphic rocks. The igneous rocks that show narrow geochemical variations and dominantly plot in the monzonite to monzodiorite fields, are plotted in the calc-alkaline and high-K calc-alkali...

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 from three locati...

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-bas...

1 ‫مرکز‬ ‫و‬ ‫مرکزی‬ ‫ایران‬ ‫ساختاری‬ ‫منطقه‬ ‫خاوری‬ ‫قسمت‬ ‫در‬ ‫بافق‬ ‫آهن‬ ‫متالوژنی‬ ‫کمربند‬ ‫مرکزی‬ ‫ایران‬ ‫در‬ ‫طبس‬ ‫و‬ ‫یزد‬ ‫ساختاری‬ ‫بلوک‬ ‫دو‬ ‫بین‬ ‫کرمان‬ ‫کاشمر-‬ ‫ساختی‬ ‫زمین‬ ‫پهنه‬ .(Ramezani and Tucker, 2003; Haghipour and Pelissier, 1977) ‫است‬ ‫گرفته‬ ‫قرار‬ ‫میلیون‬ 1500 ‫از‬ ‫بیش‬ ‫ای‬ ‫ذخیره‬ ‫با‬ ‫آهن‬ ‫هنجاری‬ ‫بی‬ 34...

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 c...

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 ⁸⁷ Sr/ ⁸⁶ Sr ratios of the hydrothermal endmember fluids at the five sites were all higher than those at the sediment-starved sites. The endmember...

Numerous active and fossil hydrothermal carbonate chimneys have been reported at Lake Asal and Lake Abhe, in the southeastern part of the Afar Rift (Republic of Djibouti): a tectonically and volcanically active region for the last 30 million years. In this study, we report on a detailed mineralogical and geochemical investigation of unusual hydroth...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Kendari Bay has been designated as an ecotourism area and as the main route for local trading in Kendari City, Province of Southeast Sulawesi, Indonesia. An earlier study conducted by Armid et al [2] found that water quality in Kendari Bay has been polluted by heavy metals from household and factory wastes. Such metalsare spatially distributed thro...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...