著者

西川 一雄 西堀 剛 小早川 隆 但馬 達雄 上嶋 正人 三村 弘二 片田 正人

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.78, no.2, pp.51-64, 1983-02-05 (Released:2008-08-07)

参考文献数

24

被引用文献数

3 4

---

The late Cretaceous Koto Rhyolite is divided into two groups according to the succession. Each group forms an igneous cycle. The older group consists of the Kaiwara Welded Tuff and the Hatasho Quartz Porphyry, and their relationship is transitional in the field showing their co-magmatic origin. The Kaiwara Welded Tuff erupted apparently first as vesiculated magma from the top of the magma_??_reservoir followed by the intrusive phase of the Hatasho Quartz Porphyry. There are enrichment of phenocrysts such as quartz and alkali feldspar in the Kaiwara Welded Tuff, whereas plagioclase phenocrysts are more commo in the Hatasho Quartz Porphyry. The K/Rb ratios of the whole rocks are larger in the Hatasho Quartz Porphyry than in the Kaiwara Welded Tuff. The younger group consisting of the Yatsuoyama Pyroclastic Rock and the Inugami Granite Porphyry is also considered to be of co-magmatic origin although obvious intimate relationship of the two units could not be observed in the field. The differences between them in the composition of phenocryst minerals and K/Rb ratio of the whole rocks are similar to and somewhat larger than those between the Kaiwara Welded Tuff and the Hatasho Quartz Porphyry. The Inugami Granite Porphyry of the last igneous activity intruded along the ring faults whose center subsided stepwise and resulted in a double ring dike about 30km across. Thus the Koto Cauldron was composed. Natural remanent magnetism through the Koto Rhyolite suggests a clock-wise movement of the area during its igneous activity.

著者

Kenji HORIE Tomokazu HOKADA Yoichi MOTOYOSHI Kazuyuki SHIRAISHI Yoshikuni HIROI Mami TAKEHARA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.111, no.2, pp.104-117, 2016 (Released:2016-05-05)

参考文献数

50

被引用文献数

2 10

---

U–Pb zircon geochronology was applied to nine metasedimentary samples collected from Mt. Yuzhnaya, Condon Hills, and Mt. Lira in the inland region of the Rayner Complex of western Enderby Land, East Antarctica, in order to define the eastern limits of the western Rayner Complex that underwent the Pan–African metamorphism and to evaluate potential source areas of metasedimentary rocks. Condon Hills and Mt. Lira revealed metamorphic ages of ~ 894 and ~ 934 Ma, respectively, which are consistent with previously reported metamorphism in association with Rayner Structural Episode (RSE). Mt. Yuzhnaya samples affected by the RSE contain zircon grains rejuvenated during 590–570 Ma, which indicates that the Pan–African reworking can be extended up to Mt. Yuzhnaya. On the other hand, the Condon Hills samples include Archean detritus, and the age peaks from 3850 to 2491 Ma are the oldest components in the Rayner Complex of western Enderby Land. There is no evidence of reworked Napier Complex rocks in the studied Rayner samples.

著者

北代 吉宏

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.60, no.1, pp.34-45, 1968

---

By diffusion of solid states, pseudowollastonite, forsterite and cristobalite phases are identified.Then silica glass rod is used as silica component. The growth of cristobalite phase is observed, onthe contrary, silicate minerals do not develope according to the increase of diffusion time.<br> The growth of cristobalite depends on heating time, temperature and the kind of oxide component. Thelarger interaction between metallic atom and oxygen, the smaller growth of cristobalite is observed. CaO component promote cristobalitization, compared with MgO. Interaction of Ca-O is smaller than that of Mg-O, therefore diffusion rate of CaO component is larger than that of MgO. Formation of cristobalite depends on the rate of diffusion.

著者

水田 敏夫

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.73, no.7, pp.202-215, 1978-07-05 (Released:2008-08-07)

参考文献数

42

被引用文献数

2 4

---

Peridotites characterized by the texture of elongated olivine crystals, are found in the Higo metamorphic belt mainly composed of psammitic gneiss. The peridotite mainly consists of olivine, orthopyroxene, tremolite, serpentine, and talc. Spinifex-like olivine crystals, partly altered to serpentine and magnetite, consist of randomly oriented plates parallel to (010). The elongated olivine crystals in same handspecimen are chemically homogeneous, and the compositional zonation of the crystals has not been observed by microprobe analysis. However, the chemical composition of olivine ranges from FO83 to FO92 in different handspecimens. The NiO content of olivine varies from 0.2 to 0.5 weight per cent and the MnO content from 0.1 to 0.2 weight per cent. The NiO and MnO contents are about the same as those of komatiitic olivines. On the other hand, the olivines in the Higo perioditite contain a negligible amount of CaO and remarkabIly differ from those of extrusive peridotite (komatiite). The rocks are free from clinopyroxene and contain large and prismatic orthopyroxene. The extremely Ca-depleted orthopyroxenes (En89-En92) are interlocked with tabular olivines in each other. The Al2O, and Cr2O3 contents of orthopyroxenes are relatively lower than those of orthopyroxenes in alpine peridotites. From the mineral assemblages of peridotites and metamorphic rocks, and from the chemical composition of olivine and orthopyroxene, it is suggested that the peridotite bodies suffered from the regional metamorphism of amphibolite facies (approximately 700°C, 3-4kb). This conclusion is also supported by the data concerning Mg-Fe2+ distribution between olivine and chromian spinel in the Higo peridotite.

著者

井上 秀雄 佐藤 和郎

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.46, no.4, pp.133-137, 1961-10-05 (Released:2008-08-07)

参考文献数

9

---

There are three pegmatites in Ryuen mine, Fukuoka Prefecture, which intruded in Masaki granite of the middle Cretaceous. The U-Pb age of uraninite from a pegmatite has been chemically determined as 100×106 years by Kimura and Iimori (1937). Uraninite was collected from the other pegmatite, of which mode of occurrence was different from the above mentioned uraninite. It occurred in chlorite vein cut the pegmatite. In order to know whether or not any measurable time interval existed between the pegmatite solodification and the vein formation, isotopic U-Pb age was determined on the uraninite from the chlorite vein. The age of uraninite is 110×106 years and the formation of chlorite vein continued immediately after the solidification of pegmatite.

著者

友成 才

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.69, no.7, pp.267-273, 1974-07-05 (Released:2008-08-07)

参考文献数

6

被引用文献数

1

---

In the central part of Chugoku Province, several types of granitic rocks, presumably of Late-Mesozoic are widely distributed. The granitic rocks in the Fuchu District have been hitherto divided into two types, namely, the Hiroshima granitic complex and the Central plutonic complex. Furthermore, the granites belonging to the latter have been divided into three groups; those of the older, the younger, and the unknown ages. Detailed classification and the relationship among these granitic rocks in the Fuchu District have been left unsolved. From the standpoint of petrographical features such as color of potash-feldspar, volume ratio of minerals, chemical composition and occurrence of xenoliths and dyke rocks, granitic rocks of the district can be divided into four types of complex as follows: (1) Mannari type (2) Ashida type (3) Hirotani type (4) Mikawa type The Mannari type granite belongs to the Central plutonic complex, and the other types to the Hiroshima granitic complex according to the current classification. The Ashida and the Mikawa type granites can be divided into those of coarse, medium, and fine grained ones and the Mannari type granite into coarse and fine members. The Mannari type granite has been intruded by the Mikawa and Ashida type. From the field evidences, the Ashida, the Hirotani, and the Mikawa types are considered to be nearly of the same age. Therefore, the Mannari tvpe granite is thought to be the oldest among these four types.

著者

南部 松夫

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.59, no.4, pp.143-151, 1968-04-05 (Released:2008-08-07)

参考文献数

14

被引用文献数

5 7

---

The new mineral akaganeite is beta-ferric oxyhydroxide from the weathered outcrop of the Akagane pyrometasomatic copper-iron deposit in Carboniferous green rock, Iwate Prefecture, Japan. The mineral is the supergene oxidation product of massive pyrrhotite and intimately associated with goethite, melantilite and two kinds of ferric sulfates. The mineral occurs in powdery aggregates of very fine orange to brownish-yellow crystals, elongated [001] and flattened (100) up to 0.3×0.03μ in size under the electron microscope. Two chemical analyses carried out in 1956 and 1959, respectively: Fe2O3 78.23, 80.98; FeO 0.82, 0.23; SiO2 3.10, 3, 57; A12O3 1.21, 1.40; Na2O 0.62, 0.82; K2O 0.19, 0.29; H2O+ 10.20, 9.71; H2O- 4.96, 2.55, sum 99.33, 99.55%. These data correspond closely to FeOOH. Chlorine was detected qualitatively, but material was in sufficient for a quantitative analysis. X-ray powder data are indexed on a tetragonal cell with a=10.50, c=3.03A. The strongest lines are 7.45 (98) (110), 5.31 (48) (200), 3.71 (21) (220), 3.34 (100) (310), 2.361 (33) (400), 2.553 (95) (211), 2.340 (8) (420), 2.300 (43) (301), 2.103 (31) (321), 1.954 ((39) (411), 1.750 (42) (600), 1.720 (12) (501, 431), 1.646 (52) (521), 1.520 (21) (002), 1.456 (28) (640), 1.441 (30d) (1.438), 1.381 (40d) (730, 312). These data agree very closely with the data obtained by Macky (1960), who showed the synthetic β-FeOOH is tetragonal, 14/m, a=10.48, c=3.023A. A DTA curve showed a slight endothermal reaction at about 300°C and a marked exothermal peak at 375°C. The mineral loss 11% in weight to 350°C, nearly all between 250 and 350°C. The name is for the mine. The mineral and name were aproved before publication by the Commission on New Minerals and Mineral Names, IMA. Two short communications on akaganeite have been described in Japanese by the present author (1957, 1960).

著者

小野 晃

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.78, no.1, pp.38-39, 1983-01-05 (Released:2008-08-07)

参考文献数

6

被引用文献数

4 5

---

K-Ar dating on hornblende from biotite-hornblende quartz diorite in northeastern part of the Kanto Mountains was carried out. The age of the quartz diorite is 251±8 Ma. The result, together with geological facts, supports the idea that island arc composed of granitic plutons was present between the Sanbagawa and the Ryoke metamorphic belts.

著者

斎藤 洋彦

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.67, no.5, pp.158-165, 1972-05-05 (Released:2008-08-07)

参考文献数

12

---

The Kabasawa placer deposit is categorized as one of the Pliocene ilmenite placer deposit and its sedimentary and conservative environment is controlled by warping movement of the Okubushi line. the purpose of this paper lies in the research of such elements which influenced the deposition of the Kabasawa placer deposit characteristics relating to type of movement, behavior and development stage of the Okubushi line made during the Pliocene era. The Okubushi line consists of combinations of cross structure of NW and NE branches meeting at tangent angles to each other which reflects the tectonics in the basement of this area. Of these, the NW brach plays a main role in the tectonic movement. The NW branch of Okubushi line controlled the deposition in Pliocene Sendai Group as well as Pliocene sedimentary basin after making warping movement and bringing about an upheaval on its southwestern side and tilting subsidence on its northeastern side. In other words, the NW branch brought about a differential movement of upheaval and subsidence through the depositional stage of Kameoka and Tatsunokuchi formation and the central part of the past upheaval changed into a depressional tilting subsidence at the depositional stage of Kitayama formation. Finally, the NW branch terminated its geologic movement with the eruption of tuff (acidic volcanic deposits) at the depositional stage of Hirosegawa tuff. The Kabasawa sandstone and conglomerate member intercalating Kabasawa ilmenite placer deposit, is a deltaic deposit which was piled up upon the region of depressional tilting subsidence during the depositional stage of Kitayama formation. It forms a circle of 2km diameter and has an extraordinary thick stratum. It is generally believed that the movement in the NW branch of Okubushi line is the result of a tectonic movement, referred to as “Green Tuff Crustal Movement”, in full activity during the Miocene era and succeeded to the Pliocene era in the northeastern part of Japan.

著者

苣木 浅彦 島 敞史 北風 嵐

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.73, no.3, pp.63-77, 1978-03-05 (Released:2008-08-07)

参考文献数

40

---

To reconfirm whether minerals of luzonite-famatinite series form complete solid solution between them as Springer (1969) reported or limited solid solution having immiscibility gap from approximately 10 to 40 mol% Cu3SbS4 as Skinner (1960) inferred. 16 samples of luzonite and famatinite from 7 mines in Japan, Formosa and Philippines were examined by electron probe microanalyser (EPMA). The quantitative analytical data by EPMA for the samples are given in Tables 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 and 13. The specimens from the Hokuetsu mine, Japan and the Mankayan mine, Philippines have most nearly stoichiometric composition of luzonite as from 0 to 3 mol% Cu3SbS4. They from the Lobo mine, Philippines and the Kinkaseki mine, Formosa have from 2 to 12 mol% Cu3SbS4, and from 2 to 7 or 36 to 41 mol% Cu3SbS4 in composition, respectively. Also luzonite-famatinite series minerals from the Teine, Kasuga and Akeshi mines, Japan have compositions of such wide range as from 19 to 71, 26 to 82 and 3 to 78 mol% Cu3SbS4, respectively. However, the composition corresponding to stoichiometric Cu3SbS4 of famatinite was not found during this study. Analytical data for 378 points in 16 specimens are summarized as shown in Fig. 5, and it is found that there is existance of minerals having continuous compositions between luzonite and famatinite except nearly famatinite end. Therefore it is concluded that the complete solid solution between them exists at low temperature as the result of Springer's examination.

著者

原田 一雄 児玉 秀臣

出版者

Japan Association of Mineralogical Sciences

雑誌

岩石鉱物鉱床学会誌 (ISSN:00214825)

巻号頁・発行日

vol.49, no.3, pp.115-118, 1963-03-05 (Released:2008-08-07)

参考文献数

6

---

A new occurrence of freibergite from the Chichibu Mine is described. The freibergite, which was found from the upper part of the Daikoku ore deposits, associated with pyrite, euhedral crystal of chalcopyrite, bornonite, ankerite and quartz. Mineralogical properties of the mineral are as follows; 1. euhedral, tetrahedral crystal about 1cm in diameter. 2. streak color, reddish brown. 3. ao=10.435A. 4. the spectrochemical analysis shows the presence of the major amounts of Cu, Ag and Sb, minor amounts of Fe, As and Si, and trace of Zn, Pb and Cd.

著者

Tomoki NAKAMURA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.100, no.6, pp.260-272, 2005 (Released:2005-12-21)

参考文献数

61

被引用文献数

117 154

---

The presence of abundant phyllosilicates in many carbonaceous chondrites indicates a prevailing activity of low-temperature aqueous alteration in primitive asteroids. However, among the hydrous carbonaceous chondrites known, more than 20 samples show evidence of having been heated at elevated temperatures with corresponding phyllosilicate dehydration. The mineralogical features of dehydration suggest that the heating occurred in situ in meteorites, which demonstrates that there are some hydrated asteroids that have been heated at a certain period after aqueous alteration. Recent studies have uncovered details of heating and dehydration processes in hydrous carbonaceous chondrites: step-by-step changes in mineralogy, trace element chemistry, carbonaceous materials, and reflectance spectra have been clarified. Based on data from synchrotron X-ray diffraction analysis of the matrix, heated hydrous carbonaceous chondrites have been classified as Stages I-IV, with the temperature of heating increasing from I to IV. In spite of recent progress, heat sources are poorly defined, mainly due to a lack of chronological information on the timing of the heating, and therefore more data are needed to fully clarify the thermal metamorphism of hydrous carbonaceous chondrites.

著者

Toshiro NAGASE Koichi MOMMA Takahiro KURIBAYASHI Masahiko TANAKA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.108, no.2, pp.87-93, 2013 (Released:2013-05-03)

参考文献数

21

被引用文献数

2

---

Lutecite is an aggregate of microcrystalline silica; its variety with a hexagon form is known as hexalite. Textures of lutecite and hexalite from the Arz-Bord Range, in northwestern Gobi, Mongolia, and from Banyan-obo, China, were observed by optical microscopy, synchrotron X-ray diffraction, and transmission electron microscopy (TEM). Cross sections of lutecite and hexalite observed through optical microscopy show fibrous textures. TEM observations revealed that the quartz crystals constituting each fiber exhibit irregular shapes elongated parallel to [212], which is nearly perpendicular to (101); a width of 0.5 μm; and length of a few micrometers. The results of selected area electron diffraction analyses show that the fiber bundles have V-shaped cross textures, and the crystals are twinned according to the Reichenstein-Grieserntal law. X-ray diffraction analysis indicates a total moganite content of approximately 10 wt% in this lutecite aggregate, and moganite appears as irregular-shaped domains within quartz under high-resolution TEM.

著者

モリス ポール 三宅 康幸 古山 勝彦 ペレス パブロ

出版者

Japan Association of Mineralogical Sciences

雑誌

岩鉱 : 岩石鉱物鉱床学会誌 : journal of mineralogy, petrology and economic geology (ISSN:09149783)

巻号頁・発行日

vol.94, no.11, pp.442-452, 1999-11-05

被引用文献数

4 5

---

島根県東部中海の若い盾状火山である大根島の玄武岩について全岩の主要元素・微量元素·同位体組成を分析した。K-Ar年代は第四紀の約20万年前の噴出を示している。層準ごとのサンプルの化学組成の変異は,これらがすべて同一の玄武岩質親マグマ(100 Mg/(Mg+Fe)∼56, Ni 101-160 ppm, Cr 110-226 ppm)からの分化物であることを示している。SrとNd同位体組成からは,全地球組成に近い均一な起源物質が示される。初期のマグマは後期よりも低い溶融程度で生じ,より若い溶岩の間の化学的変異は,異なる溶融程度といくらかの地殻物質混合とにより説明される。

著者

Ushio HONMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.107, no.1, pp.8-32, 2012 (Released:2012-02-29)

参考文献数

50

被引用文献数

3 3

---

It has been well established that the exchange partition coefficient for the exchange of Ca and Na between plagioclase and silicate melts [Kd = (Ca/Na)pl/(Ca/Na)melt] increases with increasing water content in the melt, but its atomistic interpretation is not well developed. This work presents new experimental data on the partition coefficient in an alkali basalt and a transitional tholeiite from the Oginosen volcano, southwest Japan and discusses the possible role of melt polymerization in the variations of the partition coefficient. The experiments were conducted at 0.1 MPa, and hydrous 100 MPa and 200 MPa conditions. The partition coefficient at 0.1 MPa increases from 0.8-1.4 to 1.5-1.8 over a temperature increase from 1090 °C to 1190 °C in the transitional tholeiite, and from 1.2 to 1.7 for 1090 °C to 1150 °C in the alkali basalt. The partition coefficient increases up to 4.1-4.2 in the presence of 3.4-3.5 wt% water in the melt in both basalts. The variations of the Ca-Na partition coefficient between the plagioclase and the melt is interpreted in terms of the degree of polymerization of the melt. The degree of polymerization of the melt decreases with the increase of temperature and water content, both of which increase the Ca-Na partition coefficient.   The anorthite content of the core of natural plagioclase phenocrysts in the alkali basalt is 63-66 mol%, suggesting crystallization under water-undersaturated conditions. In the transitional tholeiite, some of the cores of the plagioclase phenocrysts have An81-85, which is formed in a water-supersaturated run at 100 MPa and 1085 °C; however, the significance of the presence of An81-85 is unknown and must be investigated further.

著者

Kenta YOSHIDA Takao HIRAJIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

pp.1202160190, (Released:2012-02-18)

被引用文献数

5 5

著者

Kenta YOSHIDA Yoshiteru SENGEN Shigeki TSUCHIYA Kouta MINAGAWA Tomoyuki KOBAYASHI Taketoshi MISHIMA Shinji OHSAWA Takao HIRAJIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Journal of Mineralogical and Petrological Sciences (ISSN:13456296)

巻号頁・発行日

vol.106, no.3, pp.164-168, 2011 (Released:2011-07-05)

参考文献数

26

被引用文献数

5 5

---

A remarkably high Li/B ratio has been recognized from a crush-leached fluid extracted from a foliation-parallel quartz vein, IR27, intercalated with a pelitic schist in the northern proximal to the Western Iratsu body of the Sambagawa metamorphic belt, SW Japan. Thin section observation shows that most quartz grains in the vein are polygonal and rarely show the undulatory extinction. These facts suggest that the quartz grains in the vein could be recrystallized under relatively high-T condition with the stress free environment, and that these fluid inclusions could be trapped during the peak metamorphic stage. Most fluid inclusions in the investigated sample are composed of liquid and vapor. Raman spectroscopy revealed that the liquid phase is aqueous fluid and the vapor is mainly a mixture of CH4 and N2. Their ice melting temperatures determined by microthermometry, ranging from -3.5 to -7.1 °C, show a striking contrast against the data of the fluid inclusions in later stage veins, ranging from -0.6 to -1.7 °C. However, the homogenization temperatures of IR27 are much lower than the peak metamorphic temperature of the host pelitic schist. The partition coefficients between the host rock and released fluid (Drock/fluid) calculated from P-T pseudosection show that DBrock/fluid tends to be higher than DLirock/fluid in a pelitic system, because of generally high modes of white mica in pelitic schists. The calculation suggests that the crush-leached fluid obtained from the quartz vein intercalated with the pelitic schist has higher Li/B ratio than fluids of those intercalated with the metabasite.

著者

三浦 裕行

出版者

Japan Association of Mineralogical Sciences

雑誌

鉱物学雜誌 = Journal of the Mineralogical Society of Japan (ISSN:04541146)

巻号頁・発行日

vol.25, no.1, pp.9-10, 1996-01-01

著者

Manabu YAMADA Ritsuro MIYAWAKI Izumi NAKAI Fujio IZUMI Kozo NAGASHIMA

出版者

Japan Association of Mineralogical Sciences

雑誌

Mineralogical Journal (ISSN:05442540)

巻号頁・発行日

vol.20, no.3, pp.105-112, 1998 (Released:2007-03-31)

参考文献数

11

被引用文献数

1 9

---

The crystal structure of ammonioleucite was refined by a Rietveld analysis using X-ray diffraction data of the type specimen. The refinement with a space group I4l/a was converged at Rwp=12.12, Rp=9.39, RF=4.86, RB=7.71, and Re=2.55% with lattice parameters of a=13.2106(6) and c=13.7210(7) Å. Ammonioleucite is isostructural with leucite. The (Si, Al)O4 tetrahedra form 4-, 6-, and 8-membered rings by sharing their apical oxygen atoms. The crystal structure consists of the three-dimensional framework of the rings of the tetrahedra. Ammonium ions are located in cavities in the framework. The (NH4)+ ions in these cavities are larger than the corresponding K+ ions in leucite, causing the cavities to be enlarged relative to those in leucite. Among the 4-, 6-, and 8-membered rings of (Si,Al)O4 tetrahedra, only the 8-membered rings have diameters large enough to allow the migration of exchangeable K+, (NH4)+ and Na+ ions.

著者

宮脇 律郎 松原 聰 横山 一己

出版者

Japan Association of Mineralogical Sciences

雑誌

日本鉱物学会年会講演要旨集

巻号頁・発行日

pp.137, 2003 (Released:2004-07-26)

---

福島県川俣町水晶山から発見されたイットリウムタンタル酸塩鉱物は、既知の類縁鉱物Formanite-(Y)のようにメタミクト化することなく、明瞭な粉末X線回折を示す(堀・小林,2000)。今回、この鉱物について、EPMAによる定量分析と単結晶X線回折強度データを用いた結晶構造解析を行った。 Y,Ln(ランタニド),TaおよびNdに加えて、本研究では少量のTi、Th、U およびCaが検出された。後方散乱電子像では、試料は均一ではなくラメラ状の組織が観察された。微少部位についてガンドルフィーカメラや四軸自動回折計によりX線回折実験を行ったところ、ウラン含有量の多い部位はX線の回折を与えず、本試料が部分的にメタミクト化されていることが判った。ウラン含有量が少ない結晶質部位の定量分析結果から以下の実験式が得られた:(Y0.78Yb0.06Dy0.04Er0.04Gd0.02Lu0.01Ho0.01Sm0.01Ca0.01Tm0.01Tb0.01U0.01)Σ1.01(Ta0.58Nb0.39Ti0.02)Σ0.99O4。本鉱物は単斜晶系で空間群はP2/aである。最小二乗法で精密化した格子定数は、a = 5.292(2), b = 5.452(2), c = 5.1149(18) Å, β = 95.89(3)°, Z = 2、である。この空間群と格子定数は、合成YTaO4 (Wolten, 1967)と良く一致し、正方晶系のFormanite-(Y)とは一致しない。構造解析は、R1 =0.0340に収れんし、以下の結果が得られた: 席,x y z Ueq;Y 0.2500 0.76342(17) 0.0000 0.0076(2); Ta 0.2500 0.30254(11) 0.5000 0.0088(2); O1 0.4922(10) 0.4360(12) 0.2669(10) 0.0096(11); O2 0.0975(11) 0.0868(11) 0.2514(11) 0.0111(11)。 この解析結果は基本的に合成YTaO4と同じである。ニオブに部分置換されたタンタルの配位は四面体4配位とみなすことができる。一方、希土類元素は酸素により8配位されている。本鉱物の解析結果から計算した平均原子間距離はTa-Oが1.916、Y-Oが2.368 Åで、合成YTaO4と比較するとTaO4四面体に明らかな収縮が見られる。本鉱物は単純にFergusonite-(Y)やFergusonite-β-(Y)のTa置換体とは位置づけず、これまで知られているどの鉱物種にも該当しない。 堀・小林(2000)日本鉱物学会2000年度年会講演要旨集,P08. Wolten, G. M. (1967) Acta Crystallogr., 23, 939