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, 2013-01-30

参考文献数

20

著者

川崎 雅之 宮島 宏

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.34-40, 2013 (Released:2013-03-02)

参考文献数

29

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Mr. Shinmatsu Ichikawa was a prominent mineralogist, although he was an ordinary citizen and not in government service. He lived from the late Meiji Period to the early Showa Period. He taught in elementary school and teacher training school despite not having a regular university education. He was self-taught in mineralogy and foreign language, and became a pioneer in the field of crystal morphology. His contributions include observations of the etched surfaces of natural minerals and of artificial etched quartz crystals and quartz spheres. He observed the etch pits, etch hillocks, growth hillocks and striations on the surfaces of several minerals found in Japan, engraved their positions, shapes and distributions on metal plates, and discussed his observations.   He built the Ichikawa Mineral Laboratory in his house in 1918 to store his collection of minerals, rocks and fossils (more than 7000 specimens in all). His collection includes big quartz crystals twinned after Japan law from the Otome mine, twisted quartz from the Naegi region, amethyst crystals from Mt. Ametsuka and the Yusenji mine, natural etched minerals from various parts of Japan, and many minerals from the North America. The Laboratory is a historic cultural site in his hometown. Its preservation and enlightenment activities are cooperatively carried out by the local government and a neighborhood self-governing body.

著者

平野 伸夫 竹之下 愛 土屋 範芳

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.5, pp.198-207, 2009 (Released:2009-11-26)

参考文献数

28

被引用文献数

2 2

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Carbonate hot spring is a natural chemical reaction field for understanding CO2 geological sequestration as a natural analogue. Natural analogue studies are particularly important to understand the kinetics of mineral precipitation which has potential difficulties in experimental investigations. Carbonate sinter is frequently formed in and around carbonate hot spring, which can be suitable to elucidate mechanisms of carbonate precipitation associated with flushing CO2.   Oku-Okuhachikuro hot spring, located in Kosaka town, Akita Prefecture, NE Japan, is an artificial hot spring after drilling of exploration for the Kuroko-deposits, and it is still active where carbonate sinter has still been forming continuously for more than thirty years after drilling. The temperature of spring water is 44 °C and water pH is 6.2, with discharge rate of 0.08 m3/min. The average chemical compositions of sinter correspond about 80 wt% CaCO3, and 4 wt% Fe2O3, associated with minor (<1 wt% each) SiO2, MnO, MgO, Na2O and K2O. Carbonate sinter is mainly composed of aragonite with a small amount of calcite; an intimate occurrence of these two forms of CaCO3 is the most characteristic feature of this locality. However, mineral assemblage, texture and structure of carbonate sinter are different in relation to the distance from the blowout point. Near the blowout point, the sinter is well solidified and shows laminar structure having both of calcite and aragonite. Thickness of Ca-rich laminar ranges from 20 to 150 μm and Fe-rich one is from 10 to 80 μm. Calcite and aragonite assemblage is mainly observed in Ca-rich layer. The Fe-rich layer, however, is composed only of aragonite. The sinter along downstream becomes porous and is monomineralic having aragonite as CaCO3. The observed relations on the special distribution of aragonite/calcite and the possible stability relations of these phases through EPMA and TG-DTA analyses suggest an importance of minor elements (Fe, etc.) in the precipitation of metastable carbonates: this possible effect of the precipitation of metastable phases should be taken into account in the consideration of geochemical processes of CO2 mineral trapping.

著者

小原 泰彦

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.41, no.5, pp.193-202, 2012 (Released:2012-11-30)

参考文献数

61

被引用文献数

2 5

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The Godzilla Megamullion is the largest known oceanic core complex, located in the Parece Vela Basin, an extinct backarc basin in the Philippine Sea. The previous studies argued that the basin was active from 26 Ma to 12 Ma at an intermediate-spreading rate of 8.8-7.0 cm/year full-rate, although the basin shows the characteristics typical for slower spreading ridges. For example, many peridotites in the Parece Vela Basin are much less depleted than those exposed at comparable spreading rates on other mid-ocean ridge systems. The tectono-magmatic characteristics of the Parece Vela Basin were thus thought unusual and paradoxical.   However, the recent studies, based on the high-density samplings on the Godzilla Megamullion, show the evidences that the basin became slow to ultraslow environment in its terminal phase. Zircon U-Pb dating of gabbroic rocks from the Godzilla Megamullion reveals that the estimated slip rate of the Godzilla Megamullion detachment fault was ∼ 2.5 cm/y; significantly slower than the previous estimate. The morphology and geology of the termination area are similar to those observed in ultraslow-spreading ridges. Decreasing degree of partial melting of the peridotites as well as increased amount of plagioclase-bearing peridotites (showing melt stagnation in the shallow lithospheric mantle) are observed towards the termination of the Godzilla Megamullion.   Based on the recent observations at the Godzilla Megamullion, it would be argued that the terminal phase of a backarc basin development will go through an ultraslow-spreading environment, erupting alkaline basalts. There will be an overlap period of the terminal alkaline basalt magmatism and the rifting of a succeeding backarc basin.

著者

田崎 和江 朝田 隆二 渡邊 弘明 白木 康一

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.35, no.1, pp.22-33, 2006 (Released:2006-03-01)

参考文献数

27

被引用文献数

1 2

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Characterization of man-made rock-wool fibers were investigated by using optical and electron microscopic techniques and discussed how to affect on human health. The rock-wool fibers were collected from spraying on the roof. Mineralogical analyses were carried out by X-ray powder diffraction. Most fibers can exist as straight or curved fine threads with sharp points μm-nm in diameter under electron microscopy observations. The rock-wool is complex agglomerates of fibers and fumes with cement of calcite. The shape and size are significantly important factors for hazardous assessment of man-made fibers. The fibers are easily adhering to protein-rich spherical materials in 1% BSA (bovine serum albumin) and in ringer’s solution for few days aging. Spherical protein-like materials are similar to “asbestos body” with dumbbells shape. Man-made fibers have been manufactured for over 20 years, but there have been few concerns raised regarding the safety of rock-wool, were considered to be non-hazardous, because of the different durability in the lung. Present study consistently suggests that man-made fibers with fine and sharp points have similar risk as carcinogen of asbestos. The results of both patch test and adhesion materials with dumbbells shape provide clues regarding the mechanisms of tolerance in the lungs of exposed animals, and may be relevant for humans.

著者

山元 正継 西澤 達治 三森 俊亮 業田 顕行 緒方 武幸

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.46, no.3, pp.81-107, 2017 (Released:2017-10-07)

参考文献数

62

被引用文献数

3

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Two suites of xenoliths and an associated scoria-bearing pyroclastic fragment were sampled near Kampu volcano on Oga Peninsula of the northeast Japan arc. These scoria-hosted xenoliths consist of hornblende-bearing clinopyroxenite, hornblendite, and hornblende gabbro cumulates, hornblende megacrysts, and minor amounts of lower crustal pyroxene-plagioclase granulites. The minerals within the cumulates are euhedral and the interstitial glass is interconnected with the hosting scoria. The cumulates and their hornblende megacrysts have 87Sr/86Sr and 143Nd/144Nd ratios (0.70316-0.703390 and 0.512877-0.512974) similar to those of the Kampu magmas (0.702917-0.703409 and 0.512883-0.512988). However, these samples are not in isotopic equilibrium with each other or with the hosting scoria, with the latter having relatively constant Sr isotopic compositions (average of 0.703187). This is exemplified by two hornblende megacrysts with unusually high Al2O3 contents (< 17 wt%) that have different Sr isotopic ratios (0.703039 and 0.703235) and are isotopically homogenous from core to rim. This suggests that each melt that coexisted with the megacrysts was separated as a discrete batch without any isotopic mixing near the base of the lower crust. The host scoria was derived from discrete batches of magma having different isotopic compositions, but the scoria itself is isotopically homogeneous, indicating magma mixing and homogenization during the rapid ascent and transportation of these xenoliths from the lower crust to the Kampu volcano. This was most likely caused by the injection of upper-mantle-derived mafic magma into the base of the lower crust, as evidenced by micro-hornblende within the hosting volcanic glass that contains more Mg than the hornblende megacrysts.   The granulite xenoliths have mosaic textures, contain plagioclase with deformation twins, are closely inter-locked, and do not contain any hosting glass material. They have Sr and Nd isotopic compositions (0.70501-070532 and 0.51260-0.51263) that contrast with the cognate hornblende megacrysts, the cumulates, and the Kampu lavas, but are similar to less metasomatized lower-crustal amphibolites (amphibole with compositions of 0.70524 and 0.51261) from Ichinomegata maar near Kampu volcano. Rare hornblendes within these granulites record the onset of metasomatism, although the isotopic composition of these samples remained relatively unchanged until a subsequent cryptic metasomatic event that generated the wide range of isotopic and trace element compositions present within the Ichinomegata amphibolites.

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.46, no.2, pp.68-68, 2017 (Released:2017-05-13)

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日本新産鉱物情報(2015年)以降,2016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と,種名変更などがあるものや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

榎並 正樹

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.35, no.1, pp.11-21, 2006 (Released:2006-03-01)

参考文献数

26

被引用文献数

5 9

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Asbestos consists of fibrous aggregates of serpentines and/or amphiboles including chrysotile, anthophyllite-gedrite, cummingtonite-grunerite, tremolite-actinolite and riebeckite. The dispersion staining method, X-ray diffractometry, electron-probe microanalysis and Raman spectroscopy are briefly reviewed to assess their potential use for asbestos identification. Optical, crystal chemical and spectrographic characteristics of asbestos are summarized along with their powder X-ray diffraction patterns, energy dispersive spectra and Raman spectra data.

著者

柚原 雅樹 鮎沢 潤 大平 寛人 西 奈保子 田口 幸洋 加々美 寛雄

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.34, no.6, pp.275-287, 2005-11-30

被引用文献数

3 5

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The Cretaceous granitic rocks, the Kitazaki Tonalite and Shikanoshima Granodiorite, and veneer Oligocene sedimentary rocks, the Tsuyazaki Formation, are distributed in the Watari Peninsula, Fukuoka Prefecture. There are mineral veins composed by calcite and zeolites in those rocks. Rb-Sr, and fission track geochronological analyses were carried out for granitic rocks, in order to determine the cooling process of granitic rocks and timing of hydrothermal activity. Biotite and felsic fraction separated from the Kitazaki Tonalite and Shikanoshima Granodiorite give Rb-Sr isochron age of 108.6 ± 2.5 Ma and 107.0 ± 0.7 Ma, respectively. Fission track ages from the Kitazaki Tonalite are 97 Ma (titanite), 89-88 Ma (zircon), 14 Ma (apatite). Fission track ages from the Shikanoshima Granodiorite are 95 Ma (titanite), 87-84 Ma (zircon), 15 Ma (apatite). Fission track ages of apatite from granitic rocks are younger than the Tsuyazaki Formation, which suggests a thermal event at about 15 Ma to reset the fission track apatite age. The homogenization temperature of fluid inclusions in calcite are 89-111 °C (Kitazaki Tonalite), 95-118 °C (Shikanoshima Granodiorite) and 85-91 °C (Tsuyazaki Formation). Sr isotopic compositions of calcite and zeolites in granitic rocks and Tsuyazaki Formation are overlap with one another. These data suggest that vein minerals in granitic rocks and zeolites and calcite in the IC Member of the Tsuyazaki Formation were formed by a series of hydrothermal activity at about 15 Ma.

著者

新井 宏嘉 宮下 敦 田辺 克幸 村田 守

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.6, pp.177-194, 2011 (Released:2012-01-21)

参考文献数

57

被引用文献数

5 7

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Jadeite-bearing meta-basalt occur within a greenstone complex at the southern margin of the Mikabu greenstones in the Shimonita area, northern Kanto Mountains, Central Japan. The greenstone complex shows a block-in-matrix structure consisting of small, sporadically occurring greenstone blocks (jadeite-bearing meta-basaltic lavas, jadeite-free pargasite rocks, and jadeite-free garnet-epidote rocks) embedded within a matrix of actinolite rocks. The complex has been interpreted as a tectonic mélange composed of allochthonous metamorphic blocks within the Mikabu greenstones. However, both the greenstone blocks and actinolite rocks preserve original igneous or pyroclastic textures without the deformation structures commonly seen in tectonic mélanges. The concentrations of high field strength (HFS) elements within the jadeite-bearing lavas indicate that these rocks are alkali basalts derived from oceanic island basalt (OIB). The composition of these lavas is similar to that of OIB blocks in the Mikabu greenstones in Shikoku, western Japan. The whole-rock chemical composition of the lavas reveals higher Na2O concentrations (max. 10.1 wt%) than in unmetamorphosed Hawaiian OIB alkali basalts. The actinolite rocks of the matrix show a pyroclastic texture and contain relic Ca-pyroxenes. The concentrations of HFS elements and pyroxene chemistry of the actinolite rocks indicate an origin from tholeiitic MORB, similar in composition to typical Mikabu greenstones in the Kanto Mountains and Shikoku. These observations strongly suggest that the greenstone complex is not a tectonic mélange comprising allochthonous metamorphic rocks within a matrix of Mikabu greenstones, but that the entire complex consists of Mikabu greenstones. Therefore, the complex was subjected to Sanbagawa metamorphism after a Na-enrichment event; jadeite grew in Na-rich blocks during the metamorphism.

著者

北風 嵐

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.39, no.3, pp.104-109, 2010-05-30

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Sulfide blebs composing of bornite solid-solution, mooihoekite, isocubanite and pyrrhotite occur in andesite from the lava dome, Tarumai volcano, Hokkaido, Japan. The lava dome consists of two-pyroxene andesite. Some bornite solid-solutions are found as exsolution lamellae in mooihoekite which is originally crystallized as intermediate solid-solution (iss) in the Cu-Fe-S system at high-temperature, included in magnetite phenocrysts of the andesite. Isocubanite occurs closely associating with pyrrhotite included in orthopyroxene phenocrysts of the andesite, and is exsolved from the Cu-bearing pyrrhotite. Some bornite solid-solutions and mooihoekite are found in a ground mass as micro-crystals. The magnetite including mooihoekite and bornite solid-solution, and the orthopyroxene including pyrrhotite and isocubanite may be crystallized at different conditions. The crystallization temperatures are about 950 °C for the silicate melt including magnetite phenocrysts, and about 1150 °C for the orthopyroxene bearing silicate melt. Therefore, this andesite magma is thought to be formed by the magma mixing.<br>

著者

新田 恵理子 木股 三善 星野 美保子 越後 拓也 濱崎 聡志 篠原 宏志 西田 憲正 八田 珠郎 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.35, no.6, pp.270-281, 2006 (Released:2007-03-15)

参考文献数

43

被引用文献数

1

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High temperature volcanic sublimates including so-called “molybdenum blue” sampled around the high-temperature fumaroles at Iwodake volcano, Satsuma-Iwojima, Kyushu, Southwestern Japan, were characterized by X-ray powder diffraction, X-ray micro-diffraction, Raman micro-scattering, electron microprobe and X-ray photoelectron spectroscopic analyses. The identified minerals are molybdenite, sphalerite, tugarinovite, molybdite, hematite, halite, sylvite, anglesite, wulfenite, quartz, tridymite, cristbalite and potassium alum. Occurrences of both tugarinovite and molybdite are observed in Kudriavy volcano, too, and the coexistence of their minerals is characteristic of high-temperature volcanic sublimates. The molybdenite and sphalerite from Iwodake are exceedingly rich in Re (up to 0.77 wt%) and In (up to 1.69 wt%), respectively, distinguished from those of a different origin by chemical composition. The molybdenite consists of both of 3R and 2H1 polytypes. Sublimates from Iwodake and Kudriavy volcanoes are similar in mineralogy. Although the difference in the host rock arises between the Iwodake (rhyolite) and the Kudriavy (basaltic andesite) volcanoes, their volcanic gases resemble each other in F and Cl contents. This resemblance might cause the similarity in sublimate mineralogy between these volcanoes.

著者

田切 美智雄 松本 哲平 谷本 一樹

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.32, no.4, pp.175-184, 2003 (Released:2008-04-21)

参考文献数

11

被引用文献数

2 4

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Precision of the degree of graphitization (GD) is evaluated based on repeated experiments on a sample of pelitic schist, and analyses on ten pelitic schists collected from an outcrop. The experimental error is ±2 in two sigma confidential level at GD=31 and GD=26, respectively. The results suggest that if GD value difference is larger than 6, two neighboring samples have the discontinuous metamorphic grade. The systematic sampling and experiments along the direction normal to the strike, revealed the discontinuous boundaries of the metamorphic grade existing at a upper stream of the Sanbagawa-river and at an outcrop of the Arakawa-river, i.e., the boundaries between the shuffled cards Miyashiro (1994). The former boundary is serpentinitic greenschist within the pelitic schists, the latter one, the thrust plane in pelitic schists. A thick layer having continuous GD value also exists in the Sanbagawa metamorphic terrain as revealed by the experiments of the Kamabuse-yama boring core of 280m depths.

著者

奥村 聡

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.230724, 2023 (Released:2023-09-26)

参考文献数

17

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Magma rheology is a key factor in understanding and modelling volcanic eruptions. Until now, macroscopic rheology experiments reveal the viscosity of the magma and conditions at which shear thinning and brittle failure occur. However, it remains unclear what mechanisms control complex magma rheology from the atomic and molecular-scale structure perspective. More specifically, no experimental data on molecular-scale structure have been obtained for deforming magma in the non-Newtonian regime. To resolve this situation, we have developed an experimental system for time-resolved X-ray diffraction and scattering at SPring-8, Japan. Based on the experiments on this system, we found that intermediate-range ordering (IRO), which is related to the size of the ring formed by SiO4 tetrahedra, expands under tensional deformation. In particular, the IRO shows elastic and anisotropic deformation in the non-Newtonian regime. On the other hand, the short-range ordering such as T-O and T-T distances, where T and O represent Si and Al in the T-site and oxygen, respectively, shows no clear change during the deformation. These results imply that shear thinning and brittle failure may originate from the expansion of the ring size because the large ring is relatively weak and its formation results in cavitation. According to this model, the magma fails when the stress is large enough, rather than the strain rate, because the IRO deforms according to the stress applied to the structure. Recent experiments also observed that small and anisotropic rings form under compression. Previous rheology experiments did not confirm the difference between the conditions, at which shear thinning and brittle failure occur, under tension and compression, but the experimentally-determined molecular-scale structure clearly shows different behavior. To fully understand the mechanism of magma rheology from the view of the molecular-scale structure, we need to perform additional studies including the experiments and theoretical approaches.

著者

富岡 尚敬

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.231002, (Released:2023-10-16)

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Akimotoite (IMA1997-044), (Mg,Fe)SiO3, a new silicate mineral of the ilmenite group, has been discovered in the shocked Tenham chondritic meteorite. It occurs as aggregates adjacent to clinoenstatite in host-rock fragments trapped into shock-induced melt veins. Chemical analysis gives the simplified formula to be (Mg0.79Fe0.21)SiO3, the same as for clinoenstatite. Selected-area electron diffraction (SAED) patterns correspond to the synthetic (Mg,Fe)SiO3 ilmenite phase with the space group R3. The lattice parameters estimated from the SAED patterns are a = 0.478(5) nm, c = 1.36(1) nm in the hexagonal setting. The calculated density is 4.0(1) g/cm3. In a shock-induced melt vein, akimotoite and clinoenstatite are intergrown with a topotaxial relationship in which close-packed oxygen layers of both phases are preserved. This occurrence suggests that the enstatite-akimotoite transition was caused by a shear transformation mechanism without long-range atomic diffusion.

著者

佐々木 宗建 徂徠 正夫 奥山 康子 村岡 洋文

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.5, pp.175-197, 2009 (Released:2009-11-26)

参考文献数

48

被引用文献数

2 2

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Water qualities and occurrence of precipitates in 10 hot and mineral springs with large calcareous deposits in Japan were investigated in order to elucidate geochemical conditions of the precipitation of carbonate minerals and water-rock interactions in their reservoirs. Chemical analyses of water samples have revealed that the spring waters were rich in NaHCO3 and CO2 components. Out of 10 springs investigated, 2 springs contain Ca and CO2-related soluble components with genetic relations to the dissolution of limestone underground; 4 springs also enriched in Ca were green-tuff type affected by gypsum dissolution. Other springs poor in SO4 component have geochemical characteristics suggesting the contribution of deep-seated fluid. The pH of reservoir fluids is considered to be buffered by CO2-HCO3 speciation. This chemical condition probably promotes rock alteration including dissolution of calcite and plagioclase, resulting in formation of large calcareous deposits in the fields studied. The calcareous precipitates consist only of calcite in three fields with relatively low water temperatures; the other deposits contain aragonite with calcite possible due to their formation at high temperatures and high concentrations of Mg, Mn and SO4 in spring waters. From a comparison of water chemistry at the points of precipitation, logarithmic critical saturation indices (SI) are empirically derived to be 0.7-0.9 for calcium carbonate and over 3.5, 0.5, 1.2 and 3.4 for dolomite, magnesite, siderite and dawsonite, respectively. Distribution coefficients of Sr and Mg between spring water and precipitates indicate that calcareous precipitates were formed near equilibrium conditions.   The possible ware-rock interaction processes elucidated in this study should be taken into account for geochemical modeling of CO2 geological reservoirs. The empirical values of SI, which are all positive for major carbonate minerals, can be the most important finding because geochemical simulation previously conducted commonly assumed precipitation at the point of saturation (SI=0).

著者

奥村 聡

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.230724, (Released:2023-09-07)

---

Magma rheology is a key factor in understanding and modelling volcanic eruptions. Until now, macroscopic rheology experiments reveal the viscosity of the magma and conditions at which shear thinning and brittle failure occur. However, it remains unclear what mechanisms control complex magma rheology from the atomic and molecular-scale structure perspective. More specifically, no experimental data on molecular-scale structure have been obtained for deforming magma in the non-Newtonian regime. To resolve this situation, we have developed an experimental system for time-resolved X-ray diffraction and scattering at SPring-8, Japan. Based on the experiments on this system, we found that intermediate-range ordering (IRO), which is related to the size of the ring formed by SiO4 tetrahedra, expands under tensional deformation. In particular, the IRO shows elastic and anisotropic deformation in the non-Newtonian regime. On the other hand, the short-range ordering such as T-O and T-T distances, where T and O represent Si and Al in the T-site and oxygen, respectively, shows no clear change during the deformation. These results imply that shear thinning and brittle failure may originate from the expansion of the ring size because the large ring is relatively weak and its formation results in cavitation. According to this model, the magma fails when the stress is large enough, rather than the strain rate, because the IRO deforms according to the stress applied to the structure. Recent experiments also observed that small and anisotropic rings form under compression. Previous rheology experiments did not confirm the difference between the conditions, at which shear thinning and brittle failure occur, under tension and compression, but the experimentally-determined molecular-scale structure clearly shows different behavior. To fully understand the mechanism of magma rheology from the view of the molecular-scale structure, we need to perform additional studies including the experiments and theoretical approaches.

著者

秋澤 紀克

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.230204, 2023 (Released:2023-06-17)

参考文献数

84

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The life cycle of the oceanic lithosphere commences in the spreading axis and ends in the subduction zone. To trace the cooling and evolutional history of the Earth, the change in thermochemical state during the life cycle of present‒day oceanic lithosphere is desired to be elucidated. In terms of the material science, spatial limitation of human‒accessible Earth interior is a bottleneck in reconstructing the thermochemical state of the oceanic lithosphere. Yet, by combining active sampling methods using ocean research vessels (ocean drilling, ocean bottom dredging, submersible survey, etc.) and passive sampling methods using Earth’s deep materials exposed to the surface owing to tectonic forces and volcanoes, we can collect samples that cover a considerable dimension. Here, I present efforts toward the elucidation of the thermochemical state of the oceanic lithosphere during its life cycle from the spreading axis to the subduction zone. The Oman ophiolite is presented as an analogue of oceanic lithosphere formed in the vicinity of a fast‒spreading axis, whereas the peridotite xenoliths from Tahiti Island are treated as an analogue of thermochemically disturbed oceanic lithosphere by a mantle plume, and those from petit‒spots are considered as an analogue less affected by thermochemical disturbance considering the lack of mantle plume beneath the petit‒spots. A heterogeneous thermal state corresponding to the segment structure is inferred in the fast‒spreading axis. The thermochemical state of the aging oceanic lithosphere is modified by mantle plume and petit‒spot magmatism, but pristine state can be reconstructed by using suitable peridotite xenoliths whose heating‒cooling and melting history is well characterized. The peridotite xenoliths from the petit‒spots can enhance a step toward reconstructing the thermochemical state of the deep oceanic lithosphere because deep‒rooted garnet‒stable peridotite xenoliths can be found.

著者

越後 拓也

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.47, no.1, pp.34-42, 2018 (Released:2018-03-21)

参考文献数

56

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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. 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.

著者

佐藤 満雄

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.30, no.6, pp.288-299, 2001 (Released:2008-08-30)

参考文献数

21

被引用文献数

1 1

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Framework structures of tectosilicates including zeolite, silica and feldspar minerals are reviewed on the basis of concentric cluster (CCL). The structural characteristics of them can be simply represented by the points (Si or Al atoms) and the lines connecting between the points. Starting from a given point, an nth CCL can be graphically defined as a set of all the points ranging from topological distance 0 to n, and all the lines responsible for the connection between them. The topological distance used here means the shortest step numbers responsible for the connection between two points, not the geometrical distance. As any kind of tectosilicate frameworks can be completely covered with the CCL by extending its topological distance from 0 to n, the topological characteristics of them are realized on a series of these CCLs. In order to quantify these CCLs, the front nodes are newly defined, and a concept of the coordination degree sequence (CDS) is introduced. In the CDS, the front nodes are characterized in terms of their topological valence numbers. The CDS can be effectively applied to the topological characterization, the classification, and the systematic computer modeling of tectoslicate frameworks. Some of application examples are shown.