Rocks mineralogy

Depending upon lithologic and structural relationship with host rocks, mineralogy, attendant alteration, paragenesis and spatial and temporal constraints, the uranium resources of the world can be assigned to the 15 main categories of uranium ore deposits. They have been shown numerically numbered in sequence in the order of their approximate economic significance in Table 1.18. At present, only 7 can be said to be economically important (see Table 1.19) and these account for more than 95% of the world resources of ura-... 

Total phosphorus content of phosphate rocks is relatively unimportant, since what really matters is its reactivity in the soil, which in turn depends on the soil itself, the rock mineralogy and the level of rock grinding. 

Classification of Igneous Rocks Using Lithogeochemistry Data, Essential Rock Mineralogy, and Projective Geometry in a Streckeisen Ternary Diagram Approach... 

Table V compares the Sierra waters with some waters from other felsic rocks. The fundamental similarities are clearly apparent as well as the minor variations that show the imprint of the details of rock mineralogy and small additions of constituents from various other sources.

Figure 4 compares several of these models with respect to the nature of the constants that each uses. The simplest model (linear sorption or Ai ) is the most empirical model and is widely used in contaminant transport models. values are relatively easy to obtain using the batch methods described above. The Aid model requires a single distribution constant, but the Aid value is conditional with respect to a large number of variables. Thus, even if a batch Aid experiment is carefully carried out to avoid introduction of extraneous effects such as precipitation, the Aid value that is obtained is valid only for the particular conditions of the experiment. As Figure 4 shows, the radionuclide concentration, pH, major and minor element composition, rock mineralogy, particle size and solid-surface-area/solution volume ratio must be specified for each Aid value. 

Although mass balance and reaction path models share a conceptual basis, they are quite different in their implementation. Reaction path models begin with an initial solution and rock composition and use equilibrium reactions to predict a final solution and rock mineralogy. Mass balance models use initial and final solution compositions and rock mineralogy to determine the extent of mineral solution reactions. Those reactions need not have reached equilibrium. 

Brown Parsons (1989) Brown, W.L. Parsons, 1. Alkali feldspars ordering rates, phase transformations and behaviour diagrams for igneous rocks Mineralogical Magazine 53 (1989) 25-42... 

The pH of most groundwaters of interest to waste disposal is in the range 6-10 (Fig. 1). There are a number of factors which are important in governing the pH of groundwater reactions with minerals in the rock, particularly aluminosilicates such as feldspars, micas and clays the partial pressure of carbon dioxide (Fcoj) the concentration of so-called conservative or mobile ions such as chloride (Michard 1987) and temperature. Reactions with the rock mineralogy and dissolved carbon dioxide can affect pH through temperature-dependent equilibria such as ... 

Igneous rocks can be classified according to their chemical or mineralogical composition. Chemical classification distinguishes acid, intermediate, basic, and ultrabasic rocks. Mineralogical classification uses the types (see also Fig. 1.2) ... 

The dominant processes controlling the movements of P through terrestrial ecosystems are schematically presented in Fig. 14-4. In a general way, the overall movement of P on the continents may be envisioned as the constant erosion of P from continental rocks and transport in both dissolved and particulate form by rivers to the ocean, stopping occasionally along this pathway to interact with biological and mineralogical systems. 

Several sub-classification.s of epithermal preciou.s-metal deposits have been proposed mineralogy, host-rock composition and elemental association (Lindgren, 1928), gold-silver ratios of metal weights (Ferguson, 1929 Nolan, 1933), mineral paragenesis (Nishiwaki et al., 1971), and production ratios of metals (Heald-Wetlaufer et al., 1983). 

Several workers have intended to estimate the chemical compositions of Kuroko ore fluids based on the chemical equilibrium model (Sato, 1973 Kajiwara, 1973 Ichikuni, 1975 Shikazono, 1976 Ohmoto et al., 1983) and computer simulation of the changes in mineralogy and chemical composition of hydrothermal solution during seawater-rock interaction. Although the calculated results (Tables 1.5 and 1.6) are different, they all show that the Kuroko ore fluids have the chemical features (1 )-(4) mentioned above. 

Several factors such as Cl concentration, water/rock ratio and temperature are important in controlling the chemical composition of the hydrothermal solution interacted with the rocks. For example, water/rock ratio affects the alteration mineralogy (Mottl and Holland, 1978 Seyfried and Mottl, 1982 Shikazono, 1984). For example, at low water/rock ratio, epidote is stable, while chlorite at high water/rock ratio (Shikazono, 1984 Shikazono and Kawahata, 1987). 

Wolery (1978) and Reed (1982, 1983) have indicated based on a computer calculation of the change in chemistry of aqueous solution and mineralogy during seawater-rock interactions that epidote is formed under the low water/rock ratio less than ca. 50 by mass. Humphris and Thompson (1978), Stakes and O Nell (1982) and Mottl (1983) have also suggested on the basis of their chemical and oxygen isotopic data of the altered ridge basalts that epidote is formed by seawater-basalt interaction at elevated temperatures (ca. 200-350°C) under the rock-dominated conditions. If epidote can be formed preferentially under such low water/rock ratio, the composition of epidote should be influenced by compositions of the original fresh rocks. 

Bryndzia, L.T., Scott, S.D. and Farr, J.E. (1983) Mineralogy, geochemistry, and mineral chemistry of siliceous ore and altered footwall rocks in the Uwamuki 2 and 4 deposits, Kosaka mine, Hokuroku district, Japan. Econ. GeoL Mon., 5, 507-522. 

Shikazono, N. (1985a) Mineralogical and fluid inclusion features of rock alterations in the Seigoshi gold-silver mining district, western part of Izu Peninsula, Japan. Ghent. Geol, 213-230. 

Stakes, D.S. and O Neil, Jr. (1982) Mineralogy and stable i.sotopes geochemistry of hydrothermally altered ocean rocks. Earth Planet. Sci. Lett, 57, 285-304. 

Geological, mineralogical and geochemical features of these deposit types (distribution, age, associated volcanism, host and country rocks, fluid inclusions, opaque, gangue and hydrothermal alteration minerals, chemical features of ore fluids (temperature, salinity, pH, chemical composition, gaseous fugacity, isotopic compositions (O, D, S, Sr/ Sr, Pb), rare earth elements)) were summarized. 

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