Some Geological Terms

The discovery of the elements and the manufacture of products from mineral sources bring us in close contact with some geological and mining phenomena. Some of these are defined and explained in Table 1.1. 

Mineral A naturally occurring inorganic, crystalline homogenous substance with defined 

Geochemical Analysis of soils or plants is useful in prospecting for metals. Underlying deposits prospecting of minerals have some influence on the chemical composition of plants and of the soil in which they grow. 

A naturally formed aggregate or mass of one or (usually) more minerals. 

Magma Naturally occurring mobile molten rock material, generated within the earth. 

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Decay of forms Np, which is important because its ( , y) and (n, 2n) reactions lead to Pu and Pu. Also, Np is an important long-term constituent of radioactive wastes, particularly because its transport through some geologic media is not as delayed as that of other actinides and because of the toxicity of radionuclides in its decay chain, especially U, Th, and Ra. 

All ore mineral deposits lie in or on solid rocks of which the Earth s crust is predominantly composed. The geological processes which are responsible for the formation of rocks also form the ore bodies associated with them. For the formation of an ore body, the metal or metals concerned must be enriched to a considerably higher level than their normal crustal abundance. The degree of such enrichment below which the extraction cost makes the processing of the ore uneconomical is termed the concentration factor. Typical values of the concentration factor for some of the common metals are given in Table 1.5. 

Laser ablation ICP-MS (LA-ICP-MS) was established in the early 1990s as a potential routine tool for the measurement of trace and ultra-trace elements in silicate systems for geology. Early studies (Perkins et al. 1993) used sample preparation techniques identical to that used to prepare rock samples for WDXRF, i.e., either a pressed powder disk or a glass bead fusion method (see Appendix VIII). Such studies concluded that LA-ICP-MS had the potential to surpass XRF in terms of the limits of detection achieved and INAA in terms of the speed of analysis (Perkins et al. 1993 481). It has long been recognized that the main limit on the quantitative performance of LA-ICP-MS is the homogeneity at the trace and ultra-trace level of the solid calibration standards available. Subsequent work (e.g., Hollecher and Ruiz 1995, Norman et al. 1996) has demonstrated that some of the international... 

SOLUTION and MIXTURE - There is some confusion between these two terms in geological literature. According to the I.U.P. A.C. (International Union for Pure and Applied Chemistry), the term mixture must be adopted whenever all components are treated in the same manner , whereas solution is reserved for cases in which it is necessary to distinguish a solute from a solvent. This distinction in terminology will be more evident after the introduction of the concept of standard state. It is nevertheless already evident that we cannot treat an aqueous solution of NaCl as a mixture, because the solute (NaCl) in its stable (crystalline) state has a completely different aggregation state from that of the solvent (H2O) and, because NaCl is a strong electrolyte (see section 8.2), we cannot even imagine pure aqueous NaCl. 

It is commonplace to assume a form of the Gibbs energy function which excludes the pressure variable for solid-state phase transformations, as the magnitude of the PAV term is small at atmospheric pressures. This is of course not the case in geological systems, or if laboratory experiments are deliberately geared to high-pressure environments. Klement and Jayaraman (1966) provide a good review of the data available at the time when some of the earliest CALPHAD-type calculations were made (Kaufman and Bernstein 1970, Kaufman 1974). Much work was also carried out on specific alloy systems such as Fe-C (Hilliard 1963) and the Tl-In system (Meyerhoff and Smith 1963). 

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