Sedimentary environment

To gain an understanding of the composition of the reservoir rock, inter-reservoir seals and the reservoir pore system it is desirable to obtain an undisturbed and continuous reservoir core sample. Cores are also used to establish physical rock properties by direct measurements in a laboratory. They allow description of the depositional environment, sedimentary features and the diagenetic history of the sequence. 

Barite [13462-86-7], natural barium sulfate, BaSO, commonly known as barytes, and sometimes as heavy spar, tiU, or cawk, occurs in many geological environments in sedimentary, igneous, and metamorphic rocks. Commercial deposits are of three types vein and cavity filling deposits residual deposits and bedded deposits. Most commercial sources are replacement deposits in limestone, dolomitic sandstone, and shales, or residual deposits caused by differential weathering that result in lumps of barite enclosed in clay. Barite is widely distributed and has minable deposits in many countries. 

This removal may also include diffusion of soluble U(VI) from seawater into the sediment via pore water. Uranium-organic matter complexes are also prevalent in the marine environment. Organically bound uranium was found to make up to 20% of the dissolved U concentration in the open ocean." ° Uranium may also be enriched in estuarine colloids and in suspended organic matter within the surface ocean. " Scott" and Maeda and Windom" have suggested the possibility that humic acids can efficiently scavenge uranium in low salinity regions of some estuaries. Finally, sedimentary organic matter can also efficiently complex or adsorb uranium and other radionuclides. 

Sedimentary deposits are usually carried to the region of deposition by water and are deposited in water. (In some cases deposits are carried by wind or ice.) It is within these water leposited sediments that hydrocarbons are likely generated from the plant and animal life that exists in these environments. Two principal properties of the sedimentary rocks that form from such deposits are porosity and permeability. 

Davies-Colley, R. J., Nelson, P. O. and Williamson, K. J. (1984). Copper and cadmium uptake by estuarine sedimentary phases. Environ. Sci. Technol. 18, 491-499. 

Coates ID, EJP Phillips, DJ Lonergan, H Jenter, DR Lovley (1996) Isolation of Geobacter species from diverse sedimentary environments. Appl Environ Microbiol 62 1531-1536. 

Thick sedimentary pile from middle Miocene to late Pliocene is exposed in the Oga Peninsula, northern Honshu, Japan (Fig. 1.153). Age of the sedimentary rocks has been determined by microfossil data. Thus, the sedimentary rocks in the Oga Peninsula where type localities of Miocene sedimentary rocks in northern Japan are well exposed have been studied to elucidate the paleoenvironmental change of the Japan Sea (Watanabe et al., 1994a,b). Kimura (1998) obtained geochemical features of these rocks (isotopic and chemical compositions) and found that regional tectonics (uplift of Himalayan and Tibetan region) affect paleo-oceanic environment (oxidation-reduction condition, biogenic productivity). However, in their studies, no detailed discussions on the causes for the intensity and periodicity of hydrothermal activity, and temporal relationship between hydrothermal activity, volcanism and tectonics in the Japan Sea area were discussed. They considered only the time range from ca. 14 Ma to ca. 5 Ma. 

The sulfur isotopic data are consistent with geologic environments of Hg and Sb deposits Sedimentary rocks are dominant and marine rocks are not present in Sb-Hg mineralization districts. However, a few samples of stibnite and cinnabar from the deposits in Green tuff region display high S S values. In contrast of this interpretation on the origin of sulfur, Ishihara and Sasaki (1994) thought that sulfur came from ilmenite-series granific rocks. However, these rocks are not found in the north Hokkaido. 

Kimura, S., (1998) Paleoceanographic Environment of Japan Sea Deduced from Chemical and Isotopic Features of Miocene-Pliocene Sedimentary Rocks. Doctoral Thesis, Keio University, 224 pp. 

White, D.E. (1965) Saline waters of sedimentary rocks. Fluids in subsurface environments. A symposium. Am. A.ssoc. Petrol. Geol. Mem., 4, 342-366. 

For instance, polymetallic vein-type deposits formed under the subaerial environment influenced by igneous and sedimentary components. 

Matthew RK (1968) Carbonate diagenesis Equihbration of sedimentary mineralogy to the subaerial environement coral cap of Barbados, West Indies. J Sed Petrol 38 1110-1119 McCulloch MT, Esat T (2000) The coral record of last interglacial sea levels and sea surface temperatures. ChemGeol 169 107-129... 

Sedimentary rocks have formed as a result of accumulation and compaction of mineral particles derived from pre-existing rocks, transported from their original places of occurrence and deposited in new environments. The essential ingredients for the formation of sedimentary rocks are (i) source materials, (ii) mechanical and chemical disintegration of these source materials, (iii) transportation of the released materials either in a clastic form... 

Syn-sedimentary chemical deposits form by chemical and biochemical precipitation of valuable metal components carried in solution, concomitant with the formation of the enclosing sedimentary rock. The manner of such deposition depends on the concentration of the metal in the solvent, the solubility of the precipitating product, the solution chemistry, and the deposition environment. Iron, manganese, phosphorus, lead, zinc, sulfur and uranium are some of the elements that have formed economically valuable deposits by chemical precipitation during sedimentation. 

By far the most important ores of iron come from Precambrian banded iron formations (BIF), which are essentially chemical sediments of alternating siliceous and iron-rich bands. The most notable occurrences are those at Hamersley in Australia, Lake Superior in USA and Canada, Transvaal in South Africa, and Bihar and Karnataka in India. The important manganese deposits of the world are associated with sedimentary deposits the manganese nodules on the ocean floor are also chemically precipitated from solutions. Phosphorites, the main source of phosphates, are special types of sedimentary deposits formed under marine conditions. Bedded iron sulfide deposits are formed by sulfate reducing bacteria in sedimentary environments. Similarly uranium-vanadium in sandstone-type uranium deposits and stratiform lead and zinc concentrations associated with carbonate rocks owe their origin to syngenetic chemical precipitation. 

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