Sedimentary rocks mineralogy

The outline of Victoria Crater is serrated, with sharp and steep promontories separated by rounded alcoves (Fig. 8.36). The crater formed in sulfate-rich sedimentary rocks, and is surrounded by a smooth terrain that extends about one crater diameter from the rim. On the crater floor is a dune field. There are no perched ejecta blocks preserved on the smooth terrain around the crater rim, probably planed off by Aeohan abrasion. The Mossbauer mineralogy of the sedimentary rocks at the crater rim and inside the crater itself is nearly the same as at Eagle crater landing site and Endurance crater, both about 6-8 km away [335]. 

Acebal, S.G. Mijovilovich, A. Rueda, E.H. Aguirre, M.E. Saragovi, C. (2000) Iron-oxide mineralogy of a mollisol from Argentina A study by selective-dissolution techniques, X-ray diffraction, and Mossbauer spectroscopy. Clays Clay Min. 48 322-330 Adams, W.A. Kassim, J.K. (1984) Iron oxy-hydroxides in soils developed from lower palaeozoic sedimentary rocks in mid-Wales and implications for some pedogenetic processes. J. Soil Sd. 35 117-126... 

Clay is found everywhere on earth, usually as part of the outer layer of the earth s crust, the lithosphere. In a few places clay is also found and mined below the surface. Clay is an erosion product of magma or sedimentary rock. Before entering into the phenomenon erosion , first some information about the various kinds of rocks of which the earth s surface is built up. By now we know that the elements O, Si, Al, Fe, Ca, Na, K and Mg mainly occur in rocks (see Geology /Mineralogy). 

Because sedimentary carbonates represent primarily chemical and biochemical precipitates from seawater, and because they make up 20% of the common sedimentary rock record, these rock types have been particularly good sources of chemical and mineralogical data for interpretation of the secular and cyclic evolution of the Earth s surface environment. This carbonate rock record as a function of geological age is now explored as are age trends in other rock types and sediment properties. With this information as background material, we can then discuss what these relationships tell us about the history of carbonates and the exogenic system throughout geologic dme. 

As might be anticipated, the trends observed for lithologic types versus age are reflected in trends in the chemistry and mineralogy of carbonates and other sedimentary rocks. Discussion of some of these latter trends, emphasizing first the overall trends for the past 3.8 billion years, then those of the Phanerozoic, are presented below. 

Kisch H. J. (1983) Mineralogy and petrology of burial diagenesis (burial metamorphism) and incipient metamorphism in clastic rocks. In Diagenesis in Sediments and Sedimentary Rocks (eds. G. A. C. Larsen and G. V. Chilinger). Elsevier, Amsterdam, vol. 2, pp. 289-493. 

Carr, G.R., 1981. The mineralogy, petrology and geochemistry of the zinc-lead-silver ores and host sedimentary rocks at Lady Loretta, northeast Queensland. Unpubl. Ph.D. thesis, Univ. Wollongong, NSW. 

Eastern U.S. oil shales are also sedimentary rocks. However, in contrast to Green River shales, the mineral constituents of Eastern U.S. shales are primarily silicates, with only about 1 wt% carbonate minerals. The bulk mineralogical composition of the Kentucky shale consisted primarily of quartz, illite and kaoli-nite, with some chlorite and pyrite. This is consistent with elemental analysis data which found the major mineral constituents to be Si, Al, Fe, and K. The elemental Ca concentration was less than 100 ppm. 

Quaide, W.L., 1956. Petrography and clay mineralogy of Pliocene sedimentary rocks from the Ventura Basin, California. Ph.D. Thesis, Department of Geology and Geophysics, University of California, Berkeley, Calif. 

Curtis, C.D. (1990) Aspects of climatic influence on the clay mineralogy and geochemistry of soils, lateosols and clastic sedimentary rocks. J. Geol. Soc., London, 147, 351-357. 

McLennan, S.M. (1989) Rare earth elements in sedimentary rocks influence of provenance and sedimentary processes. In Geochemistry and Mineralogy of Rare Earth Elements (Eds Lipin, B.R. McKay, G.A.). Rev. Mineral., Mineral. Soc. Am., 21, 169-199. 

The slow carbon cycles are intimately connected with the geochemical cycles of sedimentary rocks, which involves all crustal elements. Although our interest is focused on carbon, we must discuss some related elements but can do so only superficially. For aspects not covered, especially those of mineralogy, reference is made to the geochemistry texts of Krauskopf (1979) and Garrels and MacKenzie (1971). 

Mineralogically, zeolites are hydrated aluminosilicate minerals, which originate during the formation of igneous, metamorphic, or sedimentary rocks, principally via hydrothermal processes. Hot circulating water leaches out mineral components deep within the Earth, particularly from basalt magmas. Zeolites form in these water-rich geological environments when conditions of low temperature (<200 °C) and low pressure (4 X 10 Pa, equivalent to around 15 km depth of burial) are attained. 

The geochemical classificadon of sedimentary rocks is not as developed as for igneous rocks and most systems of sedimentary rock classificadon utHize features which can be observed in hand specimen or in thin section, such as grain size and the mineralogy of the particles and matrix. 

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