研究者詳細 - 越後　拓也

研究等業績 - 原著論文 - 越後　拓也

分割表示 32 件中 1 - 20 件目／全件表示 >>

Platinum-group element mineralization in the Merensky Reef of the Limpopo mine, Eastern Limb of the Bushveld Complex, South Africa.

Maki BIRUKAWA, Yasushi WATANABE, Takuya ECHIGO and Carmela TUPAZ

International Journal of the Society of Materials Engineering for Resources ( 日本素材物性学会 ) 25 ( 2 ) 183 - 188 2022年10月 [査読有り]

研究論文（学術雑誌）国内共著

K–Ar geochronology of orogenic gold mineralization in the Vangtat gold belt, southeastern Laos: Effect of excess argon in hydrothermal quartz

Patthana Bounliyong, Tetsumaru Itaya, Antonio Arribas, Yasushi Watanabe, Henry Wong, Takuya Echigo

Resource Geology ( Resource Geology ) 71 ( 2 ) 161 - 175 2021年04月 [査読有り]

研究論文（学術雑誌）国際共著

DOI

Reduction of oxidized sulfur in the formation of the Grasberg porphyry copper-gold deposit, Papua, Indonesia

Adi Sulaksono, Yasushi Watanabe, Antonio Arribas, Takuya Echigo, Reza Al Furqan, Clyde A. Leys

Mineralium Deposita ( Mineralium Deposita ) 2021年02月 [査読有り]

研究論文（学術雑誌）国際共著

DOI

Mineralogy and geochemistry of the Berong Ni-Co laterite deposit, Palawan, Philippines

Carmela Alen Tupaz, Yasushi Watanabe, Kenzo Sanematsu, Takuya Echigo

Ore Geology Reviews ( Ore Geology Reviews ) 125 2020年10月 [査読有り]

研究論文（学術雑誌）国内共著

フィリピンのパラワン島に位置するBelong Ni-Co鉱床は、カンラン岩が風化して生成したラテライト鉱床である。本研究では、Belong鉱床の地質学的、地球化学的、鉱物的な調査研究を行い、ガニエライト・Mn水酸化物・ゲーサイトといった鉱物がNiおよびCoの主要なホストであることを明らかにした。

DOI

Ni-Co mineralization in the Intex laterite deposit, Mindoro, Philippines

Carmela Alen J. Tupaz, Yasushi Watanabe, Kenzo Sanematsu,Takuya Echigo, Carlo Arcilla, Cherisse Ferrer

Minerals ( MDPI (Multidisciplinary Digital Publishing Institute) ) 10 ( 7 ) 1 - 33 2020年07月 [査読有り]

研究論文（学術雑誌）国際共著

フィリピンのミンドロ島に位置するIntex Ni-Co鉱床は、輝石を主とする超苦鉄質岩が風化して生成したラテライト鉱床である。本研究では、Intex鉱床の地質学的、地球化学的、鉱物的な調査研究を行い、ガニエライト・Mn水酸化物・ゲーサイトといった鉱物がNiおよびCoの主要なホストであることを明らかにした。

DOI

Organic matters and acid-sulfate alteration in Itomuka mercury mine, Hokkaido, Japan: Implications for the transportation and deposition mechanisms of Hg

Takuya Echigo, Mitsuyoshi Kimata, Masahiro Shimizu

Resource Geology ( Resource Geology ) 70 ( 2 ) 204 - 213 2020年04月 [査読有り]

研究論文（学術雑誌）

DOI

Chemical characteristics of zircon from Khaldzan Burgedei peralkaline complex, western Mongolia

Sarangua, Nergui, Yasushi Watanabe, Takuya Echigo, Mihoko Hoshino

Minerals ( Minerals ) 9 ( 1 ) 2019年01月 [査読有り]

研究論文（学術雑誌）

DOI

新潟県阿賀町の流紋岩質溶結凝灰岩に産する球晶の鉱物学的特徴とその形成機構

越後拓也・齋藤庸一朗・木股三善・清水雅浩・西田憲正・滝沢茂

岩石鉱物科学 ( 日本鉱物科学会 ) 47 ( 2 ) 69 - 81 2018年06月 [査読有り]

研究論文（学術雑誌）

This paper reports detailed mineralogical and geochemical descriptions of the spherulite occurring in welded tuff from Aga town, Niigata Prefecture, Japan, and also discusses its formation process. Powder X-ray diffraction showed that this spherulite mainly consists of cristobalite, Na-rich sanidine, and Na-rich plagioclase without any secondary minerals such as clay and zeolite minerals produced by hydrothermal alteration. Both the chemical compositions of plagioclase phenocrysts included in spherulite and groundmass and the chondrite-normalized rare earth elements (REE) patterns of the spherulite and its host rock are similar, showing that the present spherulite crystallized from the same pyroclastic deposits as the host rock (strongly welded rhyolite tuff). Textural observation using back-scattered electron image and micro-Raman spectroscopy showed that the present spherulite has three layers structure: rim (dense texture), mantle (porous texture) and core (fan-shaped aggregates of fibrous crystals). The distribution of elements within spherulite was examined using electron-microprobe analyzer with wave-dispersive spectrometer (EMPA-WDS). The results demonstrated that both Ca and Na are enriched in both the rim and core of spherulite, suggesting that plagioclase distributes dominantly in these parts. Detailed observation with secondary electron microscopy showed that fibrous microcrystals (～1 μm in width) of both feldspar minerals and cristobalite were intergrown to constitute fan-shaped aggregates in the core, and porous aggregates of larger crystals (～5 μm) in the mantle. These chemical and textual evidence suggested that the present spherulite formed in a series of steps as follows: (1) Nucleation and rapid intergrowth of cristobalite and Na-rich plagioclase occurred in the core of spherulite, and these minerals made up into the fan-shaped aggregate. (2) From the surrounding glass, fibrous crystals of Na-rich sanidine, and cristobalite were intergrown radially, and the incompatible components such as H2O and Ca were expelled into the residual glass, creating enrichments of those elements along the spherulite-host boundary. (3) Saturation of H2O in the residual glass resulted in pore generation in the mantle part. (4) On cooling, cristobalite precipitated on the pore wall due to degassing of volatile components and the residual glass rich in Ca crystallized into Na-rich plagioclase in the rim part of spherulite.

DOI

有機鉱物の生成機構およびナノ鉱物の表面構造と反応性に関する研究

越後拓也

岩石鉱物科学 ( 日本鉱物科学会 ) 47 ( 1 ) 34 - 42 2018年03月 [招待有り]

研究論文（学術雑誌）単著

Organic minerals are natural organic compounds with both well-defined chemical composition and crystallographic properties; their occurrences show traces of the high concentration of certain organic compounds in natural environments. Thus the origin and formation process of organic minerals will lead us to understand the fate and behavior of the organic molecules in the lithosphere. All of each organic mineral can be classified into the one of following two groups: ionic organic minerals in which organic anions and various cations are held together by ionic bonds, and molecular organic minerals in which electroneutral organic molecules are bonded by weak intermolecular interactions. Karpatite, a natural crystal of coronene (C24H12), is the most typical molecular organic minerals and its crystal/molecular structures and carbon isotopic composition suggests that this mineral was crystallized from PAHs (polycyclic aromatic hydrocarbons)-rich hydrothermal petroleum by hydrothermal activity. In the process of formation of organic minerals, the formation of structural units, such as organic acid anion and PAH molecules, precedes their migration and concentration. The first stage includes the formation or cleavage of C-C bonds, but the latter stage does not. In addition, we have investigated the influence of size, morphology, surface structure, and aggregation state on the reductive dissolution of hematite with ascorbic acid using two types of nanoparticles with average diameters of 6.8 ± 0.8 nm and 30.5 ± 3.5 nm, referred to as Hem-7 and Hem-30, respectively, in this paper. TEM (transmission electron microscope) observation revealed that previous to dissolution, Hem-7 is present as both dispersed particles and as aggregates. Dispersed particles dissolve initially before aggregates, which influences its dissolution rate. The Hem-30 hematite has nanoscale surface steps and internal defects, and its dissolution initiates from the steps, defects, or sharp edges of the crystals. This study directly shows the importance of size, surface roughness, defects, crystal morphology and aggregation states on dissolution rates of nanoparticles.

DOI

Manganese contents in volcanic pyroxenes in island arcs: case study from the South Yatsugatake Volcanic area, Japan

Ayumi Miyasaka, Mitsuyoshi Kimata, Mihoko Hoshino, Takuya Echigo, Masahiro Shimizu, Norimasa Nishida

Neues Jahrbuch für Mineralogie - Abhandlungen ( Schweizerbart Science Publishers ) 193 ( 3 ) 311 - 323 2016年08月 [査読有り]

研究論文（学術雑誌）国内共著

本研究は、八ヶ岳火山帯南部で採取された安山岩中の輝石を電子線マイクロプローブ装置で詳しく化学分析し、日本以外の島弧火山に産する輝石と比較したものである。検討の結果、八ヶ岳に産する単斜輝石はMnに富み、斜方輝石はMnに乏しいことが判明した。この結果は、八ヶ岳火山における火成活動において、Mnに富む地殻成分の取り込みがあったことを示唆する。

DOI

Inferring origin of mercury inclusions in quartz by multifractal analysis

Tomo Shibata, Teruyuki Maruoka, Takuya Echigo

Nonlinear Processes in Geophysics 22 ( 1 ) 47 - 52 2015年01月 [査読有り]

研究論文（学術雑誌）国内共著

DOI

Single crystal X-ray and electron microprobe study of Al/Si-disordered anorthite with the low content of albite

Takuya Echigo, Mihoko Hoshino, Mitsuyoshi Kimata, Misahiro Shimizu, Tomoaki Matsui, Norimasa Nishida

Zeitschrift für Kristallographie 229 ( 6 ) 435 - 449 2014年05月 [査読有り]

研究論文（学術雑誌）国内共著

DOI

ジオマテリアルを利用した除染