著者

岡田 敏朗 長瀬 敏郎 今井 裕之 上原 誠一郎

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.46, no.4, pp.117-123, 2017 (Released:2018-01-12)

参考文献数

17

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Sakura quartz, which shows cherry blossom-like texture on the (0001) cross-section, occurs from Obira mine in Oita prefecture, Japan. The unique texture was analyzed by using CL, EBSD, EPMA, BSE, and OPM. The texture includes numerous solid and liquid inclusions, and is composed of Brazil twin lamellae and Dauphine twin domains. The texture would be named as sakura texture after sakura-ishi (cerasite), which was a variety of cordierite. The quartz crystal with the sakura texture grew by two growth stages. At the first stage, numerous inclusions were incorporated into the milky part and the growth bands are indistinct. In contrast, growth bands were clearly observed at the second stage. The sakura texture developed at the first stage. Almost all quartz crystals from Obira mine have the sakura texture, and the texture formed on replacement process at late greisenization. The sakura texture is a characteristic feature of quartz from skarn deposit.

著者

木村 眞

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.44, no.1, pp.1-9, 2015 (Released:2015-03-05)

参考文献数

59

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Minerals in meteorites give constraints on the formation history of not only meteorites, but the solar system. Here I introduce some characteristic minerals in meteorites. Enstatite chondrites contain abundant unusual sulfide and metallic minerals that were formed under highly reducing conditions. Refractory inclusions were formed in the earliest stage of the solar system. They typically contain Ca-Al-rich minerals. A new mineral, kushiroite, is one of such minerals, and formed under rapid crystallization conditions. Ultrahigh-pressure minerals are commonly encountered both in chondrites and differentiated meteorites, indicative of pervasive impact processes in the early solar system. An eclogitic mineral assemblage encountered in a CR chondrite suggests the possibility that asteroids were primarily larger than previously estimated.

著者

海野 進

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.48, no.2, pp.63-75, 2019 (Released:2019-06-05)

参考文献数

70

被引用文献数

1

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Boninite is the only igneous rock in the IUGS recommendations, which was named after a Japanese island ‘Bonin’, a corrupted Japanese of ‘Munin-to’. Homogeneous glass inclusions in chrome spinel of boninite from Ogasawara, Guam and Oman Ophiolite preserve at least three primary magmas followed by discrete fractionation paths designated high-silica, low-silica, and ultralow-silica boninites, in decreasing degree of source mantle depletion. The T-P conditions and the source depletion of boninites led to a model of subduction initiation along the Izu-Bonin-Mariana (IBM) arc at 52 Ma. The Philippine Sea and Pacific plate boundary was underlain by heterogeneous mantle with depleted harzburgite blocks embedded in depleted mid-ocean ridge basalt (MORB) mantle (DMM). Subsidence of the old and dense Pacific Plate caused upwelling of the heterogeneous mantle, causing adiabatic melting of DMM to MORB, while the refractory harzburgite was uplifted without melting. Fluids from the subducted slab induced flux melting of the MORB residue and harzburgite to generate low- and ultralow-silica boninites and high-silica boninite, respectively. The variations of magma geochemistry in the IBM arc indicate sustained subarc mantle convection, arc magmatism and backarc spreading, which were driven by trench retreat resulted from the foundering dense Pacific Plate. The Oman Ophiolite formed at a divergent plate boundary in the Neotethys and subsequently experienced arc tholeiite and low-silica boninite magmatism, indicating depletion of the source mantle through time. The arc magmatism was caused by thrusting of a rotating microplate over young and buoyant lithosphere, imposing a compressive stress field on the overriding plate. This prohibited forearc spreading and mantle wedge convection, leading to rapid cooling and termination of the arc magmatism in <3 Myr. Os isotopic modeling demonstrate that the enigmatic harzburgite for the IBM high-silica boninite source fractionated from the primitive upper mantle at 1.5-1.7 Ga, whereas the IBM (ultra) low-silica boninite source fractionated at 3.6-3.1 Ga. The average DMM and the source of Oman low-silica boninite differentiated at 2.6-2.0 Ga.

著者

森下 知晃 荒井 章司 田村 明弘 石田 義人

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.37, no.1, pp.1-14, 2008 (Released:2008-05-12)

参考文献数

92

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A peculiar amphibolite rich in deep vivid green-colored amphibole porphyroblast was found as a boulder in the Chiroro River of Hidaka Town, Hokkaido, Japan. The amphibolite mainly consists of deep vivid green-colored amphibole (porphyroblast), colorless amphibole (matrix) and plagioclase with a small amount of chlorite, epidote and chromian spinel. Deep vivid green-colored amphibole porphyroblast is more than 20 modal % in the rock. Chromian spinel rarely occurs as inclusions in deep vivid green-colored amphibole porphyroblast. The Cr2O3 content of the deep vivid green-colored domain is usually ∼1 wt% (up to 2.5 wt% nearby chromian spinel) whereas that of colorless amphibole in the matrix is low, < 0.1 wt%. Deep vivid green-colored amphibole porphyroblast is heterogeneous in chemical compositions within each grain and is divided into three domains as follows: (1) high-Cr2O3 (∼1 wt%, up to 2.5 wt%) and Al2O3 (> 10 wt%) green-colored domain, (2) relatively high-Cr2O3 (∼1 wt%) and low- Al2O3 (< 10 w%) green-colored domain and (3) low-Cr2O3 (< 0.1wt%) and Al2O3 (< 10 wt%) colorless domain. Chondrite-normalized rare earth element (REE) patterns of both deep vivid green-colored amphibole porphyroblast and colorless amphibole in the matrix are characterized by low light REE with positive Eu anomaly. The Cr#[= Cr/(Cr + Al) atomic ratio] and TiO2 content of chromian spinel in the amphibolite are similar to those in a serpentinite complex of the Kamuikotan Zone. The amphibolite was formed by either amphibolitization of a rock containing chromian spinel derived from the surrounding serpentinite complex or extensively metasomatized serpentinite due to interaction with surrounding metamorphic rocks.

著者

龍 徹 木股 三善 西田 憲正 興野 純 清水 雅浩

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.34, no.5, pp.242-251, 2005 (Released:2005-10-18)

参考文献数

27

被引用文献数

2 2

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Chemical evolution of ferrocolumbites from the Ishikawa-yama granitic pegmatites, Fukushima, Japan, has been revealed by electron microprobe analysis. The compositions of ferrocolumbites are different among sample locations, which are within about 1 km distant from each other. Three discernible trends in compositional variations in ferrocolumbites have been observed: (1) a homogeneous crystal trend, with low Ta/(Ta + Nb); (2) a trend with oscillatory zoning related to Ta and Nb; (3) a trend with patchy zoning related to Fe and Mn. Oscillatory zoning of ferrocolumbite is intimately related to crystal growth in magmatic process. Ferrocolumbite with patchy zoning shows parallel extinction and doesn’t appear to have the complementary distribution of octahedral cations due to some coupled substitutions on the plots of partition coefficient (each zone/the assumed average) against ionic radius. These facts and the curved boundaries of patchy zoning suggest that patchy zoning of ferrocolumbite has been produced by topotaxy in the open system.

著者

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

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.48, no.1, pp.1-24, 2019

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<p>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, <i>P-T</i> 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.</p>

著者

阿部 なつ江 荒井 章司

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.34, no.4, pp.143-158, 2005 (Released:2005-09-10)

参考文献数

89

被引用文献数

6 12

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Recent developments in instrumentation for in situ trace element analysis of peridotite minerals give us valuable data set of petrological and geochemical insights of the upper mantle. Here, we summarize petrographical, petrological and geochemical characteristics of mantle xenoliths from the Northeastern and Southwestern Japan arcs. They have clear correlations between microtexture and mineral compositions in terms of both major and trace elements. That suggests that influx-assisted melt extraction occurs simultaneously with deformation/recrystalization in the upper mantle. Their characteristics of trace-elements in clinopyroxene are distinguished from those of abyssal peridotite and peridotite xenoliths from continental regions. The geochemistry of Japan arcs’ clinopyroxenes have characteristics of arc-type mantle source; i.e., low light rare earth element (LREE) and high field strength element (HFSE; Ti, Zr and so on), rather high heavy rare earth (HREE) relative to LREE elements and Sr concentrations. They also have a rather constant Ti/Zr ratio, variable REE patterns, and relatively low LREE/HREE ratios. The simple melt extraction model can not explain these characteristics. These features are due to metasomatism, which is different from carbonatite metasomatism.

著者

皆川 鉄雄

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.42, no.1, pp.30-33, 2013 (Released:2013-03-02)

参考文献数

20

著者

森 慎一 山下 浩之 有馬 眞 藤岡 換太郎

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.41, no.3, pp.67-86, 2012 (Released:2012-06-28)

参考文献数

185

被引用文献数

2 3

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We determined K-Ar ages of the late Miocene to Pliocene andesitic to basaltic dykes and lavas distributed in the Tanzawa-Oiso area in the southern Fossa Magna region, central Japan. Our data indicate two distinct periods of volcanic activity in this region; one took place during the middle Miocene (about 15 Ma) and another during the late Miocene to Pliocene (7.5-4.2 Ma). Combined the present results with the age data reported previously from volcanic rocks in the southern Fossa Magna region, the present study suggests that the volcanic front in this region during 8 to 4 Ma was located at about 40 km east of the present-day volcanic front. The volcanic front began to migrate westward to the present-day location at about 4 Ma. The westward migration of volcanic front was probably associated with an abrupt change of lateral motion of the Philippine Sea Plate from north- northwestward to northwestward occurred between 4 and 2 Ma.

著者

木村 純一

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

pp.120611b, (Released:2013-01-12)

被引用文献数

1 2

著者

岡本 敦

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.41, no.5, pp.185-192, 2012 (Released:2012-11-30)

参考文献数

33

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Serpentinization is a hydration process that causes significant changes in physical and chemical properties of the oceanic lithosphere. Based on hydrothermal experiments, the reaction rates of serpentinization have been empirically obtained for typical reaction (i.e., Olivine+H2O → Serpentine+Brucite) as a function of temperature and initial grain size of the reactant mineral. However, the rate equations used for these analyses take quite empirical forms, in which the solution chemistry (saturation state) is not taken into consideration; therefore, it is difficult to extrapolate the results to different conditions and to predict evolution of the fluid chemistry in the hydrothermal systems. Serpentinization reactions are characterized by coupled dissolution of primary minerals (Olivine, Pyroxenes) and formation of secondary minerals (Serpentine, Brucite, Talc, Magnetite); therefore, the rates of elementary reactions between individual minerals and solution will be required for estimating the rate of overall hydration reaction. I also discuss the effects of competitive processes among grain surface reactions, element diffusion, water supply and structural development during serpentinization.

著者

松山 文彦 藤本 雅太郎 松原 聰

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.35, no.4, pp.207-211, 2006 (Released:2006-08-30)

参考文献数

18

被引用文献数

1

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Garronite occurs as radiating aggregates of minute fibrous crystals in amygdales of altered trachybasalt from Kuniga, Oki Islands, Shimane Prefecture, Japan. The mean chemical composition by EDS analysis leads to the empirical formula, (Na1.15K0.15)Σ1.30Ca2.28 [Al5.88Si10.06]O32·13.60H2O on the basis of O=32 in anhydrous part and H2O by difference. The unit cell parameters calculated from the X-ray powder diffraction data are a = 9.961 (3), b = 10.178 (4), c = 9.958 (4) (Å) and β = 90.020 (1) (°) with a monoclinic cell.

著者

北風 嵐

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.39, no.1, pp.32-33, 2010 (Released:2010-03-27)

参考文献数

10

著者

浜根 大輔

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.44, no.1, pp.57-59, 2015 (Released:2015-03-05)

参考文献数

6

著者

北風 嵐 小松 隆一

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.45, no.5, pp.133-137, 2016 (Released:2016-11-02)

参考文献数

14

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Ni-rich horomanite is found from the chalcopyrite-bearing (1.0-1.5 mode%) layer in the Kouyama gabbroic body, Hagi city, Yamaguchi Prefecture, western Japan and as second occurrence in the world.  It occurs as inclusions in chalcopyrite interspaced with silicate minerals, vanadium-bearing magnetite and ilmenite. It is often associated with siegenite and is secondarily replaced by violarite. Chalcopyrite associating with Ni-rich horomanite commonly shows the polysynthetic twin.  Analytical data for horomanite obtained by EPMA are Cu: 0.56-2.19, Fe: 23.01-25.32, Ni: 37.45-41.35, Co: 1.56-4.03 and S: 32.85-33.32 wt%. Their variations are small for inner grain or another grain. The atomic ratio of (Cu + Fe + Ni + Co): S correlates well with ideal formula of 9:8 for horomanite. In addition, Ni content in metal ratio for (Cu + Co): Fe: Ni (at%) ranges from 52 to 59 and is Ni-rich than that of original horomanite from the Horoman peridotite. Horomanite might be considered to be continuous solid solution ranging from 3.0 to 5.5 in terms of Ni(+Co) content. Therefore, general formula for horomanite is thought to be (Fe + Cu)6 − x(Ni + Co)3 + xS8(0 < x < 2.5).

著者

佐脇 貴幸

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.32, no.1, pp.23-41, 2003 (Released:2008-04-21)

参考文献数

155

被引用文献数

2 7

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Crustal fluids are sometimes trapped in minerals during crystal growth or healing of microcracks. The fluids trapped and completely sealed in minerals are called “fluid inclusions”. A fluid inclusion is considered to be a small closed system after trapping, and the conditions of temperature, pressure and chemistry at fluid-trapping can be reproduced in fluid inclusions by various analytical systems. Microthermometry, chemical analyses and observation on occurrence of fluid inclusions are available for exploration of ore deposits, geothermal and petroleum resources, for studies on thermal histories of sedimentary rocks, for elucidation of origins, formation conditions and processes of igneous and metamorphic rocks, for analyses of paleo-stresses and paleo-climates, and consideration on astronomical events.

著者

野坂 俊夫

出版者

日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.41, no.5, pp.174-184, 2012

被引用文献数

2

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Serpentinization of peridotites involves the production of hydrogen, which is a source of vital energy for chemosynthetic communities and abiotic methane or other hydrocarbons. Serpentinite-hosted hydrothermal vent fields that discharge fluids with hydrogen have been widely noticed as a possible environment for the generation of life on the early Earth and other terrestrial planets. In this context, it is important for us to understand petrological constraints on serpentinization processes related to hydrogen production. Magnetite formation by oxidation of iron in olivine is the most effective process for hydrogen production during serpentinization. Recent petrological studies have revealed that the magnetite formation is controlled by silica activity and Fe-Mg diffusion rate in olivine crystal, as well as temperature and water/rock ratio during serpentinization. Without local elevation of silica activity via fluid infiltration, magnetite forms at temperatures ranging approximately from 150 to 350 °C with most favorable condition at around 300 °C, but fails to form because of increasing diffusion rate in olivine crystal at higher temperatures and Fe-serpentine or Fe-brucite formation at lower temperatures. It should be kept in mind, however, that the formation of oxidized serpentine could produce hydrogen as well.<br>

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.45, no.1, pp.43-44, 2016 (Released:2016-03-03)

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「地球温暖化シミュレーション 地質時代の炭素循環」「隕石でわかる宇宙惑星科学」

著者

角縁 進 永尾 隆志 長尾 敬介

出版者

日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.29, no.5, pp.191-198, 2000-11-30

被引用文献数

3 16

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More than 40 monogenetic volcanoes are distributed over an area of 400 km² in the Abu Monogenetic Volcanic Field, southwest Japan. The eruptive products consist of alkaline basalt and calc-alkaline andesite to dacite lavas and pyroclastics, which are collectively known as the Abu Monogenetic Volcano Group. We have examined the eruption history of the Abu Monogenetic Volcano Group based on 33 new K-Ar ages. Most samples were dated by normal K-Ar method, and yielded ages between 1.9 and 0.1 Ma. The ages of two very young samples were determined using an unspiked method incorporating a mass-fractionation correction procedure. This gave an averaged age of about 40 ka.<br> K-Ar ages from the Abu Monogenetic Volcano Group are concentrated at around 1.7 Ma and 0.2 Ma, and the activity is therefore classified into early and late periods, respectively. The early activity had a duration of about 0.4 mys, during which time 0.3 km³ of alkaline basalt alone was erupted. The late activity produced 0.8 km³ of alkaline basalt and 2.1 km³ calc-alkaline andesite to dacite, and lasted about 0.8 mys. Alkaline basalt was mostly produced in the first half of the late period, with maximum eruption rate at about 0.4 Ma. This activity was followed by more voluminous calc-alkaline andesite-dacite eruptions which climaxed at 0.2 Ma. Although associated alkaline basalt activity continued in this period, eruption volumes steadily decreased.<br> Periodic alkaline basalt activity in southwest Japan is thought to have originated from small mantle diapirs, with intermediate calc-alkaline magmas being produced by mixing between alkaline basalt and felsic crustal melts. Coincidence of alkalic and calc-alkaline magmas and the eruption history in the later period in the Abu Monogenetic Volcano Group suggest that heating induced by repeated intrusion of alkaline basalt resulted in partial melting of the lower crust, thus producing intermediate to felsic calc-alkaline magmas. These crustal melts may then have mixed with alkaline basalt and produced the relatively voluminous intermediate calc-alkaline magmas erupted in the latest stage.

著者

宮脇 律郎

出版者

一般社団法人 日本鉱物科学会

雑誌

岩石鉱物科学 (ISSN:1345630X)

巻号頁・発行日

vol.36, no.6, pp.182-183, 2007 (Released:2008-03-27)

参考文献数

9