著者

野坂 俊夫

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.174-184, 2012 (Released:2012-11-30)

参考文献数

74

被引用文献数

2 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.

著者

栗林 貴弘

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.210115, (Released:2021-04-14)

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Hitachiite (IMA2018-027), ideally Pb5Bi2Te2S6, has been discovered from the Hitachi mine, Ibaraki Prefecture, Japan. Hitachiite commonly occurs as small size of crystals (∼ 30-50 μm) with euhedral hexagonal plate form within pyrite crystals, and co-exists with pyrite, chalcopyrite, sphalerite, pyrrhotite, and galena. Hitachiite shows a metallic luster and black streak, and its macroscopic color is silver grey. Hitachiite has a Mohs' hardness of 2½-3, and its calculated density is 7.54 g/cm3. The discovered hitachiite has trigonal symmetry with a = 4.2200(13) Å, c = 27.02(4) Å. Its space group is P3m1. Hitachiite has a layer-type structure based on ABC-type closed packing of each single element atomic sheet stacked along the c-axis. The stacking sequence is -Te-Bi-S-Pb-S-Pb-S-Pb-S-Pb-S-Pb-S-Bi-Te- (15 layers). It is possible that hitachiite would be forming a homologous series expressed as Bi2Te2S・nPbS with tetradymite (n = 0), aleksite (n = 1), and suddlebackite (n = 2).

著者

吉田 健太 丸谷 由 桑谷 立

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.51, no.1, pp.220412, 2022 (Released:2022-11-08)

参考文献数

52

被引用文献数

2

---

Pumice ejected from the Fukutoku-Oka-no-Ba (FOB) eruption of August 2021 arrived at the Nansei Islands after 2-months drifting, and subsequently arrived at Kanto area to the east and Taiwan, Philippines, and Thailand to the west. Deposition of huge amount of the drift pumice, most of which had a chocolate-chip cookie resemblance in appearance, is a drastic event and thus attracted SNS account holders, so that the arrival timeline can be traced via their daily posts. Gathering such huge amount of information from the internet can be a powerful tool to investigate and predict a geologic phenomenon that affects wide area in a short time scale. We introduce the drift pumice from FOB with respect to their deposition style, petrographic characteristics, and comparison with the previous drift pumice phenomena observed in Japan. Their impact to the Japanese society was well reflected to the buzz on Twitter. Finally, we discuss how the scientist should behave on the internet to provide correct information in an effective way.

著者

吉田 健太

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.50, no.1, pp.10-14, 2021 (Released:2021-03-25)

参考文献数

34

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Fluid inclusions in high-pressure type metamorphic rocks provide direct information of the deep fluid activity. However, their small size occasionally prevent detailed geochemical study of fluid inclusions. To overcome this difficulty, we applied crush-leach method to quartz veins developed during or near the peak metamorphic stage. Another possible solution is a focused ion beam that allows us precise machining of the solid material. The fluid inclusion study combined with conventional petrographic studies revealed the nature of fluid (and related material) cycle in the subduction zone. Another powerful approach to investigate the material transfer is so-called “data-driven approach” that employs high-dimension dataset and machine-learning techniques. NMF analysis applied to the Sanbagawa metapelite dataset revealed an evolutional change of the whole-rock composition with metamorphic grade.

著者

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.50, no.2, pp.57-58, 2021 (Released:2021-05-26)

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日本新産鉱物情報(2019年)以降,2020年12月末までに確認された日本産新鉱物および新産鉱物,その他について紹介する.太字は少なくとも化学的,結晶学的性質が明らかにされたもので,信頼度が高い.

著者

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.31, no.5, pp.261-267, 2002 (Released:2008-05-08)

参考文献数

31

被引用文献数

1 1

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According to the recommended nomenclature for zeolite minerals by the subcommittee on zeolites of the Commission on new minerals and mineral names of IMA (1997), 83 species have been defined. After the recommended report, three new zeolites have been approved in the Commission up to the date. Though gmelinite-K was recorded in the zeolite report of 1997, it was formally approved in 1999. Here, all 85 spicies are summerized and the 41 species among them found in Japan are briefly reviewed.

著者

森下 知晃

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.52, no.1, pp.230203, 2023 (Released:2023-07-28)

参考文献数

98

---

Ultramafic rocks, i.e., peridotites and pyroxenites, occur in a variety of tectonic settings on Earth. Ultramafic rocks can form as accumulation of mafic minerals from basaltic to komatiitic melts and be a major component of the Earth's mantle. The origin and history of ultramafic rocks are expected to provide information on the processes of partial melting and melt migration/extraction in the mantle and on the tectonic evolution of geologic units containing ultramafic rocks. I study ultramafic rocks in metamorphic belts, ocean floor, and mantle sections of ophiolites. My career began with a study of the Horoman Peridotite Complex in the Hidaka metamorphic belt in Japan. The ultramafic rocks and associated mafic rocks in the Horoman body record a very complex evolutionary history from the mantle conditions to crustal conditions. It is difficult to constrain the tectonic setting affecting events in the Horoman Peridotite Complex. On the other hand, ultramafic rocks in the mantle section of ophiolites and abyssal peridotites directly recovered from ocean floor to study melting processes and melt-rock interactions in the mantle can be used to constrain their tectonic setting, or at least as analogs to these tectonic settings. Studies on the Oman ophiolite by Japanese groups and literature studies of other ophiolites suggest that many ophiolites are later modified by subduction-related magmatism. Several ophiolites are being studied to elucidate the maturing process by subduction-related magmatism. Simple partial melting and melt extraction is expected in the adiabatically upwelling mantle beneath the mid-ocean ridge. In fact, abyssal peridotites directly recovered from mid-ocean ridges provided a unique opportunity to elucidate these processes. Comparison of abyssal peridotites recovered from the mid-ocean ridges and arc regions (fore arc and back arc) is key to understand the differences in magmatic processes in the two regions. Ocean science with research vessels has a well-defined working hypothesis that can only be addressed by direct sampling from the seafloor. To understand a crucial issue in Earth science as to why plate tectonics occurs on Earth, it is essential to elucidate the life of the oceanic lithosphere from its birth to its subduction into the mantle. Direct sampling of oceanic lithosphere by drilling is the key to solving this issue. I would like to emphasize that members of the Japan Association of Mineralogical science can play an essential role in leading analyses of rock samples directly recovered from seafloor. Rock samples recovered from seafloor by drilling and any methodology, as well as samples from anywhere on Earth, should be published in as papers, and these data would help integrate knowledge about the history of the Earth and planet and its future.

著者

千葉 茂樹 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

vol.30, no.3, pp.126-156, 2001 (Released:2008-08-30)

参考文献数

54

被引用文献数

2 2

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Bandai volcano is located in the southern part of Tohoku-Honshu arc, Japan, and has been active from about 300 ka. Most recently, the volcano erupted in 1888 and the phreatic eruption caused volcanic body collapse and produced huge debris avalanche deposit. Here we present new data of the tephrochronology and volcanic geology of Bandai volcano and discuss its growth history. The tephra-loam association in this area consists of the Hayama and the Mineyama Loam Formations. Sixty-three layers of tephra are recognized in the Mineyama Loam Formation, and seventy-seven layers of tephra in the Hayama Loam Formation. The volcanic activity is classified into seven stages based on tephrochronology: Stage 1: 300 ka≤(presumed age), Stage 2: 300-280 ka, Stage 3: 250-230 ka, Stage 4: 170-85 ka, Stage 5: 75-57 ka, Stage 6: 36-28 ka, Stage 7: 24-0 ka. Pyroxene andesite lavas and tephras are eruptions of Bandai volcano throughout its activity, and more than 13 large avalanche deposits are found in Stages 2, 5, 6, and 7 including 1888 debris avalanche. Modes of eruptions were almost sub-plinian with lava effusions from Stages 2 to 3, whereas sub-plinian was subsequently followed by vulcanian with lava effusions from Stages 5 to 7. Sub-plinian eruptions occurred in the earliest phase of Stages 5, 6, and pumice falls with occasional pumice flows were associated. Stage 4 consists of two eruption types. Large debris avalanches were commonly produced related with the sub-plinian eruption, except for 1888 eruption. Bandai volcano is a complex of at least five stratocones, and resurge of volcanic activity caused collapse of pre-existed volcanic body. This cyclic feature is considered to be the behavior of the volcano.

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.50, no.2, pp.59, 2021 (Released:2021-05-26)

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田上ペグマタイト

著者

富山 眞吾 梅田 浩司 花室 孝広 高島 勲 林 信太郎 根岸 義光 増留 由起子

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.4, pp.111-121, 2007 (Released:2007-11-29)

参考文献数

15

被引用文献数

1 2

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Mutsu-Hiuchidake Volcano has an erosion caldera which shows a horseshoe-like geomorphological feature toward east. Tertiary strata as a basement are distributed in the caldera. Tertialy strata and a part of pyroclastic deposits of the Mutsu-Hiuchidake Volcano have altered strongly to moderately by hydrothermal activities related to the volcanism. This study is to clarify a progress history of the alteration by using a geological mapping, thermoluminescence (TL) dating, x-ray diffraction analysis, an infrared reflection absorption analysis and a fluid inclusion study.      Highly altered zone is recognized in the area of midstream to upstream along the Ohakagawa and the Koakagawa within erosion caldera. The argillic alteration zone surround a silicification zone in the highly altered area shows a circular distribution. The strongly altered areas are along NNW-SSE to NNE-SSW fractures. The alteration areas were divided into the smectite, kaolinite, alunite and pyrophyllite zones.      The kaolinite and alunite zones give the TL ages of quartz 67 ± 13 ka (KG-5), 88 ± 18 ka (OG-4) and 91 ± 23 ka (OG-1). The smectite zone within the argillic alteration zone of outside of collapse caldera, yield the ages 752 ± 215 ka (SO-2) and 615 ± 197 ka (KG-1). These TL ages suggest the hydrothermal activity end at 70 to 90 ka.      The existence of pyrophyllite suggests that hydrothermal temperatures were 200 to 250 °C in these area. This is supported from the homogenization temperatures of fluid inclusions in calcite, 242 °C in average.

著者

中野 聰志 岡村 聡 赤井 純治

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.52, no.1, pp.221005, 2023 (Released:2023-01-31)

参考文献数

54

被引用文献数

2

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The usage of “potassium feldspar” and “alkali feldspar” has been confused in earth sciences for a long time. The term “alkali feldspar” is for the solid solution series between the two components of KAlSi3O8 (potassium feldspar) and NaAlSi3O8 (sodium feldspar), including more or less CaAl2Si2O8 (lime feldspar) as the third component. The term “potassium feldspar” is in practice for KAlSi3O8 as an end member of the feldspar solid solution. At present, the scientific or appropriate usage of the two terms without confusion is needed in earth sciences. This review outlines the history of hitherto confused usage of the two terms, and interprets how important the appropriate usage of the two terms is in earth sciences, especially in mineralogical and petrological sciences. We recommend that perthite should be termed not “potassium feldspar” but alkali feldspar, and that the term potassium feldspar should be applied to alkali feldspar at least with KAlSi3O8 content ≥ 90 mol%.

著者

辻森 樹

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.51, no.1, pp.220310, 2022 (Released:2022-07-16)

参考文献数

110

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This paper contains a series of essays which form a synopsis of my research career, which has been dedicated to orogenic and metamorphic processes in plate boundaries. It also presents my future research directions and latest investigations into simplifying the complexity of metamorphic rocks, their field observations, and associated convergent plate margin dynamics. Slab dehydration beneath forearcs and arc has been one of the most exciting problems in the field of convergent plate margin dynamics in recent decades. Orogenic and metamorphic processes are closely related. In the subduction zones, the fluid-mediated processes primarily control the crust-to-mantle transfer of volatiles, redox states of the wedge mantle peridotite and arc magmas, flux-melting to generate arc magmas, and seismicity. Although the methods of classical metamorphic petrology, based on phase equilibrium calculations, and the application of conventional geochronology continue to provide the opportunities to link high-pressure and ultra-high-pressure metamorphism to geophysical observations today, advances in geochemical techniques have great potential for key geological markers in global convergent margins. For example, recent analytical techniques and applications used in studies of metamorphic rocks, such as in-situ Li-B-Sr-Pb spot isotope analyses of jadeite, serpentinite, lawsonite, etc., evaluate hydration and dehydration along the subduction channels and subsequent slab-mantle interaction, and visualize more realistic ancient Pacific-type convergent margins. The scientific value of subduction-zone rocks and crustal rocks are not limited to their worth for geochemistry: Some metamorphic rocks and minerals are important for all realms of geological sciences, from nano-scale kinetics to the scale of mountain building events. Consequently, collaborative exchange among geoscientists, through the application of applying different approaches, tests, and challenges, to address problems related to plate boundaries in the future.

著者

浜田 盛久 東宮 昭彦

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.40, no.3, pp.91-100, 2011 (Released:2011-07-22)

参考文献数

69

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The slab-derived fluids and/or hydrous slab melts released from a subducted slab ascend into the mantle wedge, lower its melting temperature and thus induce generation of hydrous arc magmas. The estimation of H2O concentration in primary arc magmas provides an important constraint on pressure and temperature conditions of magma generation at subduction zones. This paper gives an overview of the estimation of H2O concentration in primary arc magmas by combining two petrological methods: experimental petrological studies and analyses of melt inclusions. Melting experiments of hydrous primary arc magmas have clarified that the P-T condition of magma generation shifts toward lower temperature and higher pressure with increasing H2O concentration. Another experimental constraint is that only primary magmas with low H2O (≤ 2 wt%) can erupt without modification of their primary composition by crystallization differentiation due to comparable dT/dP between olivine liquidus and basalt adiabat. However, this does not exclude presence of hidden H2O-rich primary magmas at depths. Indeed, the H2O concentrations in primary melt estimated from the analyses of primitive melt inclusions suggest wide variation (e.g., ~ 2 wt% at Kamchatka arc and ~ 4 wt% at Central American arc). H2O-rich primary magmas may ascend and erupt after differentiation and/or supply volatiles to magmas at shallower level and cause so-called “excess degassing”. Analyses of melt inclusions also clarified that the H2O concentration in primitive melt inclusions is almost constant or decrease from volcanic front to rear arc. This observation is opposite to a previous understanding that H2O concentration in primary melt increases as well as incompatible K2O across the arc.

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.4, pp.143a, 2020 (Released:2020-03-31)

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「マグマの発泡と結晶化 火山噴火過程の基礎」

著者

森下 知晃

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.230203, (Released:2023-06-28)

---

Ultramafic rocks, i.e., peridotites and pyroxenites, occur in a variety of tectonic settings on Earth. Ultramafic rocks can form as accumulation of mafic minerals from basaltic to komatiitic melts and be a major component of the Earth's mantle. The origin and history of ultramafic rocks are expected to provide information on the processes of partial melting and melt migration/extraction in the mantle and on the tectonic evolution of geologic units containing ultramafic rocks. I study ultramafic rocks in metamorphic belts, ocean floor, and mantle sections of ophiolites. My career began with a study of the Horoman Peridotite Complex in the Hidaka metamorphic belt in Japan. The ultramafic rocks and associated mafic rocks in the Horoman body record a very complex evolutionary history from the mantle conditions to crustal conditions. It is difficult to constrain the tectonic setting affecting events in the Horoman Peridotite Complex. On the other hand, ultramafic rocks in the mantle section of ophiolites and abyssal peridotites directly recovered from ocean floor to study melting processes and melt-rock interactions in the mantle can be used to constrain their tectonic setting, or at least as analogs to these tectonic settings. Studies on the Oman ophiolite by Japanese groups and literature studies of other ophiolites suggest that many ophiolites are later modified by subduction-related magmatism. Several ophiolites are being studied to elucidate the maturing process by subduction-related magmatism. Simple partial melting and melt extraction is expected in the adiabatically upwelling mantle beneath the mid-ocean ridge. In fact, abyssal peridotites directly recovered from mid-ocean ridges provided a unique opportunity to elucidate these processes. Comparison of abyssal peridotites recovered from the mid-ocean ridges and arc regions (fore arc and back arc) is key to understand the differences in magmatic processes in the two regions. Ocean science with research vessels has a well-defined working hypothesis that can only be addressed by direct sampling from the seafloor. To understand a crucial issue in Earth science as to why plate tectonics occurs on Earth, it is essential to elucidate the life of the oceanic lithosphere from its birth to its subduction into the mantle. Direct sampling of oceanic lithosphere by drilling is the key to solving this issue. I would like to emphasize that members of the Japan Association of Mineralogical science can play an essential role in leading analyses of rock samples directly recovered from seafloor. Rock samples recovered from seafloor by drilling and any methodology, as well as samples from anywhere on Earth, should be published in as papers, and these data would help integrate knowledge about the history of the Earth and planet and its future.

著者

山崎 誠子 梅田 浩司

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.41, no.2, pp.39-46, 2012 (Released:2012-05-04)

参考文献数

60

被引用文献数

6 14 6

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The cooling history of the Crateceous Toki granite, exposed in the eastern Sanyo Belt, Central Japan, was constructed from various geochronological data. The granite yields K-Ar biotite ages of 74±2 to 72±2 Ma (±1σ) and K-Ar hornblende ages of 75±4 to 74±4 Ma, which are concordant with a previously reported Rb-Sr whole-rock isochron age. Fission-track ages of zircon and apatite in the granite give ages 73±3 to 64±3 Ma and 40±4 to 37±4 Ma, respectively. These above thermochronological data suggests two distinctive cooling stages for the Toki granite; 1) a first rapid cooling stage in which the granitic magma was cooled to the temperature of host rock soon after intrusion at depths of 5-7 km in the upper crust, and 2) second slow cooling stage (7-9 °C/m.y.) associated with the uplift and subsequent erosion of the granite intrusion after ∼ 70 Ma.

著者

江島 輝美

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.6, pp.323-328, 2015 (Released:2016-01-09)

参考文献数

22

被引用文献数

2

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The chemical compositions and oxidation states of Fe in olivine phenocrysts in scorias from Kami-Kometsuka, Aso, Kumamoto Prefecture, Japan, were analyzed to evaluate effect of high temperature oxidation on the scoria. The rocks in the interior of the Kami-Kometsuka scoria cone are red-brown and weakly welded, whereas black scoria occurs on the upper zone of the cone. Olivine phenocrysts within the black scoria lack precipitate minerals, but those exposed on the voids contain small amounts of precipitates at their rims. Olivine phenocrysts in the red-brown scoria contain abundant cryptocrystalline precipitates including hematite, magnetite and enstatite. Olivines in the black scoria have normal zoning with Fo87 cores and Fo68 rims and reverse zoning with Fo66 cores and Fo70 rims, whereas those in the red-brown scoria reach 99 mol% Fo. By applying the relationship between FeLβ/FeLα-intensity ratios and Fe3+/∑Fe, the Fe3+/∑Fe of the olivine phenocrysts in the black scoria were determined to be 0-1(2)% at the cores and 3(2)% at the rims. The Fe3+ at the rims of the olivine phenocrysts in the black scoria and the cryptocrystalline precipitates and extremely high Fo contents within olivine phenocrysts in the red-brown scoria are due to high temperature oxidation.

著者

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

pp.231004, (Released:2023-10-20)

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日本新産鉱物情報(2021年)以降,2022年12月末までに確認された日本産新鉱物および新産鉱物,その他について紹介する.太字は少なくとも化学的,結晶学的性質が明らかにされたもので,信頼度が高い.

著者

越後 拓也 木股 三善

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.38, no.3, pp.57-74, 2009 (Released:2009-07-23)

参考文献数

167

被引用文献数

1

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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. This review divides organic minerals into the following two groups to discuss their contribution to new developments in mineralogy: 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. This review is composed of five sections. The first section is concerned with the definition of both organic minerals and the above two groups. The second deals with crystal chemistry and geochemistry of oxalate minerals, which are the most typical ionic organic ones. In this section, the role of (H2O)0 is firstly discussed since most oxalate minerals incorporate (H2O)0 into their crystal structures. Then the phase relationships among hydrous/anhydrous calcium oxalate minerals, namely their structural hierarchy are described, owing to the fact that they are the most abundant ionic organic minerals. In addition, the weak Jahn-Teller effect in humboldtine [Fe2+(C2O4)·2H2O] is mentioned. Fe2+ ion causes octahedral distortion in the organic mineral though the effect has hardly been observed in inorganic minerals. The third describes the origin and formation process of karpatite (C24H12), which is the molecular crystal of coronene and the most typical molecular organic mineral. The fourth and last sections summarize the characteristics of organic minerals and discuss their contribution to earth science, respectively.

著者

荒岡 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.5, pp.259-270, 2015 (Released:2015-11-11)

参考文献数

66

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Lithium, one of the ‘rare metals’ defined by Japanese government, is industrially important, and Li compounds are used for many purposes (e.g., Li-ion batteries). The major types of lithium deposits are (1) brine, (2) pegmatite, and (3) sedimentary deposits. Because of the low production costs for Li in brine deposits, they account for approximately 60% of identified worldwide Li resources and for approximately 70% of worldwide Li production. Recent increases in Li production, an expected high demand for its use in eco-friendly cars, and uneven distribution of Li-producing countries underline the importance of maintaining a stable Li supply. Therefore, more brine deposits should be exploited, and the development of other types of Li deposits should be explored.   Lithium carbonate is extracted from brine deposits in playas and salt crusts by exploiting the solubility differences of different ionic compounds. Li-rich brine deposits probably form by orographic/topographic effects and by local hydrothermal activity, because Li is a fluid-mobile element and its elution from solids into fluids is temperature dependent. Lithium-pegmatite deposits probably form by intermittent intrusions of pegmatite magma in which Li has become concentrated by the addition of Li-rich differentiates from felsic magma, because Li is a moderately incompatible element. Sedimentary-type Li deposits, which are composed of hectorite and jadarite, are still relatively undeveloped, but they are attracting a great deal of attention as possible new Li resources. In addition to these sources, methods to extract Li from seawater and to reclaim Li by urban mining of discarded products have also been examined.   Lithium isotope analysis is a powerful tool for tracing water-rock interactions and for investigating various geochemical and geological processes. Moreover, the origin of Li and the history of Li accumulation in Li deposits can often be determined from its isotopic signature.