993 resultados para Mineral resources


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Fine-grained clay subfractions (SFs) with particle size of <0.1, 0.1-0.2, 0.2-0.3, 0.3-0.6, 0.6-2.0, and 2-5 µm separated from claystone of Upper Precambrian Pumanskaya and Poropelonskaya formations on the Srednii Peninsula were studied by transmission electron microscopy, X-ray diffraction, and Rb-Sr methods. All subfractions consist of low-temperature illite and chlorite, and contribution of chlorite decreases with diminishing particle size. The crystallinity index and I002/I001 ratio increase from coarse- to fine-grained SFs. Leaching by ammonium acetate solution and Rb-Sr systematics in combination with mineralogical and morphological data indicate that illite in Upper Proterozoic claystone from the Srednii Peninsula formed during three time intervals: 810-830, 610-620, and about 570 Ma ago. The first generation of this mineral with low Rb/Sr ratio dominates in coarse-grained SFs while the second and third generations with a high Rb/Sr ratio prevail in fine-grained SFs. All of three generations are known in Poropelon claystone, whereas Puman claystone contains only illite of the first and second generations. Geological processes responsible for multistage illite evolution in claystones are discussed.

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Bibliography: p. 123-135.

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Mode of access: Internet.

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First vol. (through 1950) compiled by M.R. Burks and J.H. Schilling; 1951-55 and 1956-60 by C.F. and J.H. Schilling: 1961-65 by T. Ray; 1966-70 by M.A. and H.H. Koehn; 1971-75 by J.R. Wright and J.A. Russell; 1976-80 by Dana M. Adkins-Heljeson and Candace L. Holts.

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Succeeds Illinois resources, published in 1944 by the Illinois Post-War Planning Commission.

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Mode of access: Internet.

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None issued for 1919; 1920 includes data for 1919.

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Cover title.

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This report was written on work performed under Federal solid waste management demonstration grant no. S-801535 awarded to Lowell, Mass. in October, 1972, and cancelled at the request of the grantee in July, 1975.