1991 Fiscal Year Final Research Report Summary
Mineralogical and chemical study on Cretaceous fine-grained sediments
| Project/Area Number |
02640593
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | University of Tokyo |
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Principal Investigator |
UTADA Minoru University Museum, University of Tokyo, Associated Professor, 総合研究資料館, 助教授 (50012406)
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| Co-Investigator(Kenkyū-buntansha) |
SHIMIZU Masaaki University Museum, University of Tokyo, Research Associated, 総合研究資料館, 助手 (50162714)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Cretaceous sediments / Kwanmon Group / mineralogical composition / purple shale / carbonate cement / chemical composition / 炭酸塩鉱物 |
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| Research Abstract |
Fine-grained sediments of the Kwanmon Group(Cretaceous)had been studied mineralogically and chemically.
Mineral Composition : Fine-grained sediments are constituted by detrital grains, fine matrix, and cementing materials. The-detrital grain is mainly composed of quartz, feldspars, rhyo-dacitic and andesitic volcanic rocks, and red shale. The matrix is composed of illite, illite/smetite, " chlorite", hematite, goethite and pyrite. Illite-illite/smectite is very common without respect to stratigraphic horizon or rock-type. It is characteristic that the sediments are largely cemented by such carbonate minerals as calcite, dolomite, siderite, and rarely quartz.
Chemical Composition : The Cretaceous sediments have a wide range in chemical composition than basement sediments(Jurassic). The frequency(%)distribution patterns of SiO_2/Al_2O_3 are very similar to those of volcaniclastic sediments, which suggests that the sediments may partly contain volcaniclastic materials. The Fe_2O_3/Al_2O_3 ratios of them, especially pf purple shale, often exceed those of basalt. The frequency(%)distribution patterns of MnO/Al_2O_3, MgO/AL_2O_3 and CaO/Al_2O_3 are very similar to each other. The ratios are discreted into very low and high, which suggests that these elements may have moved in sediments after deposition. The TiO_2 and K_2O ratios to Al_2O_3 are fairly constant without respect to stratigraphic horizon and rock-type.
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