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JaLCDOI 10.18926/ESR/13949
Title Alternative Rb-Sr age of K-rich LL-chondrite Yamato-74442
FullText URL ESR_2_91.pdf
Author Nishiya, Nanayo| Okano, Osamu| Kagami, Hiroo| Nakamura, Noboru|
Abstract Yamato-74442, a brecciated LL-group chondrite, consists of fragments with igeous texture, chondrules, mineral fragments, and host. The fragments involve K-rich fragments as well as normal ones. Typically, both fragments consist mainly of euhedral porphyritic olivines and a few orthopyroxenes in a glassy grundmass. EPMA analyses for these fragments indicate that olivines and orthoptroxenes have a range of Fe/(Fe+Mg) ratio of 27.19~31.33 and 20.10~26.91 mol%, respectively. There is no significant difference in these rations between K-rich (Na2O/K2O<1) and normal framents. The K2O contents of groundmass for K-rich fragments range from 0.51 to 4.89 wt% and that of the normal fragments is 0.38~090 wt%. K2O contents of groundmass vary from fragment to fragment but are rather homegeneous in a single fragment. Rb-Sr isotopic determination on eighteen K-rich fragments (1.5 to 9.5mg in weight) gave an internal isochron age of 4.514±0.022 (2σ) Ga (λ87Rb=1.42×10-11y-1) and initial 87Sr/86Sr ratio of 0.7016±0.0024. This age is somewhat old compared with a whole rock isochron age of LL chondrites (4.493±0.18 Ga; Minster and Allegre, 1981). From a comoarison of the present result with others so far reported, it is inferred that the alkali differentiation as observed in Yamato-74442 probably occurred prior to or during a process of accumulation from LL chondrite parent material in the early solar nebula. 
Keywords LL-chondrite Rb-Sr age Sr isotope K-rich fragment
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 91
End Page 102
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310270
JaLCDOI 10.18926/ESR/13948
FullText URL ESR_2_81.pdf
Author Osae, Shiloh| Kase, Katsuo| Yamamoto, Masahiro|
Abstract The Ashanti gold deposit at Obuasi occurs in the Early Proterozoic Birimian formation. The orebodies consist of gold-sulphides disseminated in metasediments and metavolcanics, and gold-bearing quartz veins. Gold occurs mainly as native gold normally with arsenopyrite, pyrrhotite and pyrite in the metasediments and metavolcanics. In the quartz veins, however, it is associated with tetrahedrite and sphalerite. Microprobe analysis of gold grains gave an Ag content of about 8 wt.%. Textural relationships among the various mineral associations suggest that pyrrhotite, pyrite, arse-nopyrite and possibly gold may have been formed esrlier in the paragenetic sequence. The precipitation of some amounts of gold may have occurred during the later stages of the mineralisation sequence. Average arsenopyrite composition determined from electron microprobe study is: Fe: 33.6 ± 0.5 at.%, As: 29.3 ± 1.2 at.%, S: 37.1 ± 1.1 at.%, This suggests an average temperature of formation of less than 300℃ for the sulphides and possibly the gold assuming equilibrium was attained between pyrite, pyrrhotite and arsenpopyrite. The δ34S values for sulphide mineral separates are in the range between -4.1 and -10.8%. The values were, however, constrained between -4.1 and -7.0%. The narrow range and the depleted nature of the δ34S values may suggest a sedimentary sourcc of sulphur which may have undergone high temperature homegenisation before deposition. Sulphides from quartz vein samples had the most depleted δ34S values. This may indicate a different mineralisation history of the sulohides in the quartz veins from those dissemi-nated in metasediments and metavolcanics.
Keywords Birimian Ashanti gold arsenopyrite
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 81
End Page 90
ISSN 1340-7414
language English
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310561
JaLCDOI 10.18926/ESR/13947
FullText URL ESR_2_71.pdf
Author Frank k, Nyame| Kase, Katsuo| Yamamoto, Masahiro|
Abstract X-ray diffraction, ore microscopy, and electron microprobe studies have been done on ore samples obtained from the mine site at Nsuta, Ghana. Manganese ore minerals identified include nsutite, cryptomelane, pyrolusite, and lithiophorite. Except for pyrolusite, all these minerals are poorly crystalline. Chemical compositions of the minerals indicate little contamination by other elements. Quartz, muscovite, and clay minerals feature prominently as gangue in most samples. Textures are varied, and modes of occurrence are prinicipally by replacements, cavity or fracture fills, leaching and precipitaion. Mineral associations seem rather complex, as a result of which definitive paragenetic relations could not be established. Supergene formation of the manganese oxide ore is shown by the abundance of manganese minerals in solution channels such as fractures and cavities within silicate gangue. Much of the ore, howver, appears to have been enriched by leaching of gangue minerals and the later addution of manganese.
Keywords Nsuta nsutite cryptomelane pyrolusite lithiophorite
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 71
End Page 80
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310527
JaLCDOI 10.18926/ESR/13945
Title Alternative solubility and polymerization of silica in salt solutions
FullText URL ESR_2_63.pdf
Author Sugita, Hajime| Yamamoto, Masahiro|
Abstract The solubility of amorphous silica was determined in sodium chloride,potassium chloride, magnesium chloride and calium chloride solutions from 0.01 to 1moI/I and at temperatures of 21,36,50 and 65℃. The Setchenow equation was applied to the results, which enabled us to estimate the equilibrium concentration of "dissoloved silica" (molybdate-reactive silica) in the studied chloride solutions. Next, the effects of pH, supersaturation of silica and salt concentration on the polymerization rate of silica were investigated at 35℃. In the pH range from 6.4 to 7.9, the maximum polymerization rate increased with increasing pH. The maxima occurred when dissoloved silica decreased by 25% of the initial supersaturation concentrations irrespective of pH. The polymerization rate was found to be dependent on the supersaturation degree rather than on the supersaturation concentration of silica. The results in magnesium chloride solutions suggest that magnesium ions may act as nuclei in the formation of colloidal silica in geothermal waters.
Keywords amorphous silica solubility polymerization
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 63
End Page 70
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310447
Author Murakami, Masae|
Published Date 1993-10
Publication Title 岡山医学会雑誌
Volume volume105
Issue issue9-10
Content Type Journal Article
JaLCDOI 10.18926/ESR/13943
Title Alternative Water-soluble materials on volcanic ash from the 1990-94 eruption of the Unzenn volcano
FullText URL ESR_2_55.pdf
Author Akagi, Seishi| Yamamoto, Masahiro|
Abstract Water-soluble materials on volcanic ash from the Unzen volcano collected from February, 1991 to July, 1994 were chemically analyzed. They were similar in chemical characteristics to those obtained from other volcanoes. Chemical compositions varied even for materials from the same pyroclastic flow. C1 contens increased with increasing residence time of volcanic ash in air, but SO4 contents were almost fixed. It therefore seems that the reaction of volcanic ash with HC1 proceeds even at low temperatures, whereas the reaction with SO2 takes place only at high temperatutes.
Keywords volcanic ash volcanic gas Unzen volcano C1/SO4 ratio water-soluble material
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 55
End Page 62
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310484
Author Munetomo, Kazuo|
Published Date 1993-02-27
Publication Title 岡山医学会雑誌
Volume volume105
Issue issue1-2
Content Type Journal Article
JaLCDOI 10.18926/ESR/13941
Title Alternative A suggestion on the origin of biotite gneisses of the Ryoke belt in the Seto Inland Sea (Seto-nai-kai) region : Some biotite gneisses were derived from a different geologic unit to the Kuga froup
FullText URL ESR_2_23.pdf
Author Nureki, Terukazu|
Abstract The Kuga group is a Jurassic accretional complex that has been believed by many workers to be a unique geologic unit transformed into the Ryoke gneisses in the Seto Inland Sea region. I will now suggest the presence of a different geologic unti in addition to the Kuga group. Most of the biotite gneisses found at the Iwakuni-Yanai area are probably derived from rocks of the Kuga group, but the rest biotite gneisses that occur in the Murotu Peninsula, the Yashiro-jima, the E-no-shima, and the other several islands in the Seto Inland Sea region were derived from a un-known and a different geologic unit to the Kuga froup. Some pieces of evidence proving the distinct origin of the latter biotite gneisses are: (1) the biotite gneisses commonly occur as small to large fusiform bodies generally enclosed in the older Ryoke granite or as large masses contacting only with the older Ryoke granite; (2) tight folds with parallel axial surfaces are very common, and dupli-cated fold systems are found in many localities; (3) microtextures of some minerals, e.g. garnet and K-feldspar, often suggest a plural metamorphic history of the gneisses (Nuraki et al., 1982a; Miyashita % Komatsu,1993); and (4) the sillimanite zone (Ikeda,1991 : Okudaira et al.,1993) is only a metamorphic zone that can be found. The sillimanite zone is interpreted to be excluded from the progressive metamorphism in the Iwakauni-Yanai area (Wallits et al.,1992). Biotite gneisses of the sillimanite zone are found here and there and show no zonal arrangement of distribu-tion in the Ryoke belt. The estimated metamorphic temperature and pressures for the biotite gneisses of the silliman-ite zone are 530-710℃ and 2-4kb respectively, both of which are lower than of the peak metamorphism, estimated as 550-820℃ and 5-6kb, at the Iwakuni- Yanai area.
Keywords Kuga group Ryoke belt biotie gneisses Sillimanite Zone Iwakuni-Yanai area
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 23
End Page 54
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310501
JaLCDOI 10.18926/ESR/13940
Title Alternative Application of the remotely operated TV vehicle to make geological maps of the Seto Inland Sea
FullText URL ESR_2_13.pdf
Author Suzuki, Shigeyuki| Inada, Takashi|
Abstract Submarine geological survey using the remotely operated TV vehicle (RV100), was carried out in 4 offshores of the Seto Inland Sea in Kagawa Prefecture. The study areas are west of Kosei Island of Sakaide City, south of Okado-bana of Nankai Town, west of Misaki of Takuma Town and north of Nou-Misaki of Sakaide City. TV vehicle transmite clear pictures of bottom of the sea to the monitor on board. The submarine geology of the study areas are composed of Cretaceous granitic basements and Quaternary sedimentary covers. By using these pictures Recent and Pleistocene deposits could be distinguished and lithology of sediments could also be identified. Lithology of sediments was however difficult to identify using the usual sonic prospecting method. Furthermore, pictures suggesting that ripples are just forming have been obtained. The TV vehicle is convenient in submarine survry, because it can travel much longeer and deeper than human diver. A new method of mapping submarine geology using TV vehicle was developed.
Keywords Submarine geology the Seto Inland Sea remotely operated TV vehicle
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 13
End Page 22
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310382
Author Ishizu, Hideo| Miyaishi, Satoru| Yamamoto, Yuji| Takata, Shingo|
Published Date 1993-10
Publication Title 岡山医学会雑誌
Volume volume105
Issue issue9-10
Content Type Journal Article
JaLCDOI 10.18926/ESR/13938
FullText URL ESR_2_1.pdf
Author Nozaka, Toshio| Shibata, Tsugio|
Abstract The Ohsa-yama ultramafic body, which consists of several types of serpentinized peridotites, underwent contact metamorphism caused by a Cretaceous granite intrusion ; this metamorphism resulted in the formation of contact aureole, 1.5-2.0 km wide, around the granite intrusion, and produced progressive mineral changes in metaserpentinites toward the contact between the Ohsa-yama body and the granite intrusion. On the basis of analysis of mineral paragenetic relations, the Ohsa-yama ultramafic body can be divided into three zones with progressive changes in mineral assemblages as follows : Zone Ⅰ : serpentine ± chlorite ± brucite Zone Ⅱ : olivine + talc ± tremolite ± chlorite Zone Ⅲ : olivine + orthopyroxene ± tremolite ± spinel Zone Ⅰ corresponds to the parts unaffected by the thermal event, and Zones Ⅱ and Ⅲ correspond to the thermally metamorphosed parts of the Ohsa-yama body. The results obtained in this study are generally consistent with those of the previous studies on metamorphic peridotites from the Sangun and Muzuru zones.
Keywords peridotite serpentinite thermal metamorphism contact metamorphism
Publication Title Okayama University Earth Science Report
Published Date 1995-09-20
Volume volume2
Issue issue1
Start Page 1
End Page 12
ISSN 1340-7414
language English
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310611
JaLCDOI 10.18926/ESR/13937
Title Alternative A microcomputer-controlled gradual cooling system for hydrothermal reactors
FullText URL ESR_3_65.pdf
Author Yamakawa, Junji| Kawahara, Akira|
Abstract A used 8 bit microcomputer is applied for an instrument of controlling the heating temperatures of hydrothermal reactor furnaces. The temperatures were changed into appropriate values of voltage by thermocouples and additional devices. The interface board, programmable peripheral interface LSI and some IC's for addres decording are assembled into a complte unti. The device is useful for the inexpensive way of the construction of the accurate temperature control system.
Keywords hydrothermal synthesis cooling system personal computer
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 65
End Page 70
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310682
JaLCDOI 10.18926/ESR/13936
FullText URL ESR_3_57.pdf
Author Okamoto Yasuhiko| Kawahara, Akira|
Abstract The syntheses of kaliophilite have been carried out from the starting materials of near kalsilite compotions (KAISiO4), of which the AI2O3/SiO2 ratio is greater than 1/2. The X-ray powder deffraction pattern fit well to those of previous investigators. The crystal structure of synthetic kaliophilite was proposed by using the model consisting of four different types of kalsilite structure. The positions and intensities of the X-ray powder pattern were able to be explained on the basis of these four domains, belonging to thr twinning by merohedory. As a result of the conditions of the syntheses, it may be supposed that the violation of the AI-O-AI avoidanice rule can possibly exist along the domain boundaries.
Keywords kaliophilite kalsilite synthese domain boundary
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 57
End Page 64
ISSN 1340-7414
language English
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310557
Author Yamate, Tomoo|
Published Date 1993-02-27
Publication Title 岡山医学会雑誌
Volume volume105
Issue issue1-2
Content Type Journal Article
JaLCDOI 10.18926/ESR/13934
FullText URL ESR_3_47.pdf
Author Matsuda, Toshihiko| Kurosaki, Makoto|
Abstract Several specimens of rectorite-type regularly interstratified mineral (including Ca-rich one of hydrother-mal origin) from roseki deposits together with a few rectorites were examined by chemical analysis, X-ray diffraction and IR spectroscopy. These specimens are rich in SiO2, AI2O3 and H2O in addition to considerable amounts of CaO, Na2O and K2O. The Ca content in mica-like layers ranges from a slight amount to exceeding 50% of the total interlayer population. For the Ca-bearing specimens, AI-for-Si substitution in the tetrahedral sheets of mica-like layers increases in proportion to the Ca contents. Characteristic absorption bands of 950-900 cm-1 and 700-670 cm-1 are observed in IR spectra. The bands are due to AI-for-Si substitution in the tetrahedral sheets. Judging from the chemical analysis and IR spectra, the component of mica-like layer rich in Ca is not that of mica but mainly that od margarite (brittle mica). Expansion characteristics of the Ca-rich mineral are similar to rectorite and expandable layer is close to beidellite. The mineral is somewhat less expandable than rectorite under the condition of RH70-80% (Na-saturation) and EG treatment (K-saturation). The rectorite-type Ca-rich mineral reported here is simlar to rectorite in its expansion characteristics, but the component of mica-like layers is different from that of rectorite. Mica-like layer of the mineral must be mainly composed of margarite-like layer. The mineral is mainly composed of a 1 : 1 regular interstratification of dioctahedral britlle mica (margarite) and smectite (beidellite). The mineral does not strictly correspond to rectorite, defined as a 1 : 1 interstratified mineral of dioctahedral mica and smectite.
Keywords rectorite brittle mica/smectite margarite regular interstrarification
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 47
End Page 56
ISSN 1340-7414
language English
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310640
JaLCDOI 10.18926/ESR/13933
Title Alternative Sulfur isotope ratios of some Roseki deposits in the Inner Zone of Southwest Japan
FullText URL ESR_3_43.pdf
Author Yamamoto, Masahiro| Matsuda, Toshihiko| Nakagawa, Raiki|
Abstract Sulfur isotope ratios of pyrite and alunite from 5 Roseki deposits in the Inner Zone of Southwest Japan were determined. The δ34S values of all pyrite samples were in the range from -13.2 to +2.3%, the variation range for each deposit being within 8%. In each deposit δ34S values of alunite were always higher than those of pyrite, which may be interpreted as that alunite was precipirated under more oxidizing conditions than pyrite. Sulfur isotope rations of the Roseki pyrite showed a distribution similar to that of ore sulfur from skarn and vein deposits in the same Zone. This suggests that the origin of sulfur of the Roseki deposits is also host igneous rocks.
Keywords sulfur isotope ratio Roseki deposit pyrite alunite
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 43
End Page 46
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310309
Author Murakami, Takuro| Taguchi, Takehito| Ohtsuka, Aiji|
Published Date 1993-02-27
Publication Title 岡山医学会雑誌
Volume volume105
Issue issue1-2
Content Type Journal Article
JaLCDOI 10.18926/ESR/13931
Title Alternative Inversion of normal mode frequencies for estimation of lateral heterogeneity of the earth's elasticity atructure: A numerical test
FullText URL ESR_3_33.pdf
Author Onishi, Seiji| Oda, Hitoshi|
Abstract An investigation was made on effect of lateral heterogenity of the earth's elasticity structure on the normal mode frequencies. The lateral heterogeneity is expressed by an expansion of spherical harmonic functions, Pιm(cosθ)sinmΦ and Pιm(cosθ)cosmΦ, up to the second order harmonics (ι≤2). Free oscillation freguencies of the heterogeneous earth were computed by the xyz algorithm. Further we derived an analytic expression of partial derivatives of eigenfrequency with respect to the expansion coefficients, and performed a numerical test to verify whether or not it is possible to estimate the heterogeneity of the earth's structure by the inversion of noemal mode frequencies. When the earth is assumed to be elastically isotropic spheroid with short polar and long equatorial radii, frequency spectra affected by longitudinal heterogeneity terms, Pιm(cosθ)(sinmΦ, cosmΦ) (m≠ 0), for given values of ι and m coincide with each other, because these two terms describe the same heterogeneity when the earth is rotated by π/2m around rotation axis. In such a case, we cannot determine accurately the expansion coefficients of tha two heterogeneity terms by inversion of normal mode frequencies, whereas the coefficients of the latitudinal heterogeneity Pι0(cosθ) can be precisely determined. Therefore it is difficult to estimate of lateral heterogeneity of the earth's elasticity structure by the inversion of normal mode frequencies.
Keywords Normal Mode Inversion Earth's Structure Lateral Heterogeneity
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 33
End Page 42
ISSN 1340-7414
language Japanese
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310694
JaLCDOI 10.18926/ESR/13930
FullText URL ESR_3_25.pdf
Author Kajiyoshi, Koji| Suzuki, Isao|
Abstract Thermal expansion of forsterite, Mg2SiO4, is measured up to 1,600 K by the dilatometric method. The present results of volume thermal expansion Yv is 3.20 percent from 300 to 1,200 K and expansion coefficient αv is 40.5 × 10-6 K-1 at 1,200 K. They are close to those of a natural olivine (Suzuki, 1976), but are 4.4 and 11 percent smaller as compared with those reported in the former paper (Suzuki et al., 1984). The Yv and αv of forsterite are 5.00 percent and 46.7 × 10-6 K-1 respectively, at 1,600 K.
Keywords forsterite olivine thermal expansion high temperature
Publication Title Okayama University Earth Science Report
Published Date 1996-09-20
Volume volume3
Issue issue1
Start Page 25
End Page 32
ISSN 1340-7414
language English
Copyright Holders 岡山大学地球科学研究報告編集委員会
File Version publisher
NAID 120002310333