Chemical analyses illite

Table 4. Chemical Analysis of Illite, Glauconite, and Attapulgite, wt %...

Most likely, the chemical system remains closed, as far as the other components in the silicate phases are concerned, as diagenesis or low grade metamorphism becomes more evident. Although there may be transfer of calcium, it seems, from bulk chemical analysis, that there is no systematic increase in potassium nor decrease in sodium content of argillaceous sediments. The transfer of Na and K is between the two size fractions—clay and coarse fraction—or between phyllosilicates and tectosilicates. Albitization of argillaceous rocks should be a common phenomenon where mixed layered phases are predominant in clay assemblages and especially evident in the illite-chlorite zone. 

The total potassium contents of illites are lower than those of true micas. Illite contents of soils are often calculated from the chemical analysis of bulk clay samples by assuming potassium contents of 5 to 8% in contrast to theoretical values of 9.8, 7.6, and 9.4%, which follow from the ideal structural formulas of muscovite, biotite, and phlogopite, respectively. 

The most important observation which can be made after the analysis of the chemical and phase equilibria information is that illite and glauconite mineral series, do not overlap. Solid solution is not continuous, neither in the mica-like phase alone nor in mixed layering between mica and expanding layers. Glauconite is not a subspecies of illite. 

In each of the different parageneses outlined here, the instability of a mineral can be denoted by its replacement with one or usually several minerals. The rocks in these facies are typified by multi-phase assemblages which can be placed in the K-Na-Al-Si system. This is typical of systems where the major chemical components are inert and where their masses determine the phases formed. The assumptions made in the analysis up to this point have been that all phases are stable under the variation of intensive variables of the system. This means that at constant P-T the minerals are stable over the range of pH s encountered in the various environments. This is probably true for most sedimentary basins, deep-sea deposits and buried sedimentary sequences. The assemblage albite-potassium feldspar-mixed layered-illite montmorillonite and albite-mixed layered illite montmorillonite-kaolinite represent the end of zeolite facies as found in carbonates and sedimentary rocks (Bates and Strahl,... 

Table I contains seven chemical analyses of purified Fithian illite (type illite— Grim et al., 1937). The variations are large as it was not possible to exercise any control over these analyses. The variation is a composite of all the errors inherent in any analytic analysis operator, instrument, method, beneficiation, sampling. This is in addition to real differences. Unfortunately, this statement can be made about most clay-mineral analyses. There are relatively few duplicate analyses in the literature and little effort has been made to determine sub-sample variation.

Beckett described inductively coupled plasma mass spectrometry (ICP-MS) as an off-line detector for FFF which could be applied to collected fractions [ 149]. This detector is so sensitive that even trace elements can be detected making it very useful for the analysis of environmental samples where the particle size distribution can be determined together with the amount of different ele-ments/pollutants, etc. in the various fractions. In case of copolymers, ICP-MS detection coupled to Th-FFF was suggested to yield the ratio of the different monomers as a function of the molar mass. In several works, the ICP-MS detector was coupled on-line to FFF [150,151]. This on-line coupling proved very useful for detecting changes in the chemical composition of mixtures, in the described case of the clay minerals kaolinite and illite as natural suspended colloidal matter. 

Figure 5.8 Analysis of the infrared spectrum of a mineral, (a) Sample spectrum 50% albite (k-feldspar) 23% siderite 17% illite 10% chlorite, (b) Calculat spectrum 49.7% feldspar (8.0% albite, 13.2% orthoclase and 28.5% microcline) 25.2% siderite 19.0% illite 6.8% chlorite, (c) Residnal difference spectrum. From Brown, J. M. and Elliot, J. J., The Quantitative Analysis of Complex, Multicomponent Mixtures by FTIR the Analysis of Minerals and of Interacting Organic Blends , in Chemical, Biological and Industrial Applications of Infrared Spectroscopy, Durig, J. R. (Ed.), pp. 111-125. Copyright 1985. John Wiley Sons Limited. Reproduced with permission.

Chemical characterization of fines implies the elemental and mineral compositional analysis of migratory fines in porous media. Khilar and Fogler (1998) presented the range in chemical composition of migratory clays primarily of kaolinite, illite, montmorillonite, and chlorite particles in Table 5.6. We observe from this table that silica, Si02, and alumina are the major minerals. 

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