Geological applications

Regional metamorphic rocks containing orthopyroxene and K-feldspar i.e., charnockites, must have crystallized in H20-poor environment, or have a significant Fe content. If sufficient H2O were present, such rocks would become either quartz-biotite schists or silicate melts. The low H2O activity can be accoxmted for either by the intrinsic composition of the rocks (metavolcanics) or by the introduction of CO2 into the system by virtue of decarbonation reactions. The fact that many charnockites are fo md in marblebearing terrains is in accord with the requirement for low H2O activity. 

and Zussman, J. Rock Fonning Miner s v.2. Chain Silicates, Longman, Green Co., London, 379 P (1963). 

A Catalog of Analyzed calciferous and subcalciferous amphiboles together with their nomenclature and associated minerals. Geol. Soc. Am. Special Paper 98 (1968). 

Stewart, D.B. Feldspar Mineralogy, Mineral. Soc. Am. Short Course, vol.2, St-1-22, (1975). 

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XRF is widely used in industrial applications where a large number of elements need to be determined quantitatively. It is used for continuous quality control in the steel industry (e.g., the determination of Mn, Cr, Ni, Co, etc., in the production of stainless steels), and also for casting quality of coins in the Royal Mint (where Cu, Ni, and Zn are continuously monitored). Geological applications include whole rock analyses and clay identification. The power industry uses it as pollution control management, measuring sulfur and heavy metal concentrations in fuels (coal, oil) and ash. 

Selenium (masses 74, 76, 77, 78, 80, and 82 Table 1) and chromium (masses 50, 52, 53 54 Table 1) are treated together in this chapter because of their geochemical similarities and similar isotope systematics. Both of these elements are important contaminants in surface and ground water. They are redox-active and their mobility and environmental impact depend strongly on valence state and redox transformations. Isotope ratio shifts occur primarily during oxyanion reduction reactions, and the isotope ratios should serve as indicators of those reactions. In addition to environmental applications, we expect that there will be geological applications for Se and Cr isotope measurements. The redox properties of Se and Cr make them promising candidates as recorders of marine chemistry and paleoredox conditions. 

Bohlen S. R. and Boettcher A. L. (1981). Experimental investigations and geological applications of orthopyroxene geobarometry. Amer. Mineral, 66 951-964. 

Epstein S. (1959). The variation of the ratio in nature and some geologic applications. 

Geochemical kinetics is stiU in its infancy, and much research is necessary. One task is the accumulation of kinetic data, such as experimental determination of reaction rate laws and rate coefficients for homogeneous reactions, diffusion coefficients of various components in various phases under various conditions (temperature, pressure, fluid compositions, and phase compositions), interface reaction rates as a function of supersaturation, crystal growth and dissolution rates, and bubble growth and dissolution rates. These data are critical to geological applications of kinetics. Data collection requires increasingly more sophisticated experimental apparatus and analytical instruments, and often new progresses arise from new instrumentation or methods. 

Zhang (1993) used this approach successfully to model concentration profiles from crystal dissolution experiments. The applicability needs to be investigated further. To establish this method, a major effort is necessary to extract and compile V values for geological applications. 

Not many practical uses have been found for the compensation law because it is not accurate enough. One potential use of the compensation law is that if one knows the diffusivity at one single temperature, then both the pre-exponential factor A and the activation energy E may be estimated. That is, the temperature dependence of the diffusivity may be inferred. In practice, however, because the compensation "law" itself is not accurate, the uncertainty of the approach is very large (intolerable in geologic applications). Hence, the approach is not recommended. 

Ganguly J. (1982) Mg-Fe order-disorder in ferromagnesian silicates, 11 thermodynamics, kinetics and geological applications. In Advances in Physical Geochemistry, Vol. 2 (ed. S. K. Saxena), pp. 58-99. Springer-Verlag. 

The applications for ICP-MS are broadly similar to those for ICP-AES, although the better sensitivity of the former has resulted in applications such as the determination of ultra-low levels of impurities in semiconductors and long-lived radionuclides in the environment. Also, ICP-MS is better suited to the determination of the lanthanide series of elements in many geological applications because the mass spectrum is much simpler than the equivalent optical spectrum. 

A major attraction is the ability to perform isotope ratio measurements, e.g. in many geological applications to determine the age of rocks, and isotope dilution analysis. The latter in particular is gaining-popularity as a highly accurate, precise and hence traceable, method of analysis, so it is worthwhile describing these techniques in more detail. 

Low-temperature relations and geologic applications are discussed by Moh and Udubasa37. Naturally occurring members of the MoS2—WS2 solid solution series are reported in Refs.17-19. ... 

There are many instances in which it is highly desirable to analyze the smallest possible sample. This is of obvious importance when radioactive species are involved, but it is also advantageous when analyzing smaller samples means processing smaller amounts of material for an analysis, as is often the case in geological applications, among others. Measurement of isotopic ratios from pico-gram or smaller quantities of analyte has been reported for technetium [70,71], actinide elements [72], and rare earth elements [73]. 

Another large instrument with emphasis on high transmission at high resolution for isotopic measurements in geological applications is the IMS 1270 [60]. This instrument is similar in design to the IMS-3f and other Cameca f-series instruments but is much larger. It operates in either microprobe or microscope mode. Four auxiliary detector assemblies, containing an electron multiplier or Faraday cup plus the central beam primary detector, provide simultaneous detection of five isotopes. 

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