Clay mineralogy of the

More studies of the clay mineralogy of the C-T boundary layer are needed. These may indicate if the boundary deposition was associated with an extraordinary event. 

Weaver, C.E., 1961b. Clay mineralogy of the Late Cretaceous rocks of the Washakie Basin. Wyo. Geol. Assoc., Guidebook, 16 145-152. 

Montmorillonite clays absorb water readily, swell greatly and confer highly plastic properties to a soil. Thus soil stress (Section 14.8) occurs most frequently in these soils and less commonly in predominantly kaolinitic types. Similarly, a soil high in bentonite will show more aggressive corrosion than a soil with a comparable percentage of kaolinite. A chalky soil usually shows low corrosion rates. Clay mineralogy and the relation of clays to corrosion deserves attention from corrosion engineers. Many important relationships are not fully understood and there is need for extensive research in this area. 

Figure 5. Downcore profile of 6 Zn (Marechal et al. 2000) and 6 Cu values (unpublished) in Central Pacific core RC 17-203 (21° 50 S, 132° 53 W, z = 3900 m). The water-sediment interface is located below the carbonate compensation depth and deep-sea clays dominate the mineralogy of the samples.

Now we might consider what is in fact the common clay mineralogy of sandstones. Shelton (1964), Bucke and Mankin (1971) find it to be most often dominated by kaolinite. This mineral although hydrous, is conspicuous by its lack of alkalis. Thus one could suspect that alkali activity in pore solutions of sandstones is, or was, frequently low, lower at any rate than adjacent mica-bearing shales. Laboratory studies by Hanshaw and Coplen (1973) and Khareka and Berry (1973) would give a plausible explanation for such a phenomenon. If solutions are forced hydrostatically across the argillaceous membrane, ionic species in solution are selectively... 

The amount of charges on particle surfaces depends on the mineralogy of the solid and the nature of the aqueous solution in which it occurs. Several important kinds of surfaces are common in the environment (Table 11.3). Here we especially consider (1) oxides or oxyhydroxides, (2) alumino-silicates or clay minerals, and (3) natural organic matter and other solids like carbonates. 

Proc. Natl. Conf. Clays Clay Miner., 6th - Nall. Acad. Sci.Natl. Res. Counc., 1957 327-341. Bystrom, A.M., 1956. Mineralogy of the Ordovician bentonite beds at Kinnekullc, Sweden. Sver. Geol. Undersokn. Arsbok., 48 1-62. 

The mineralogy of the suspended matter carried by rivers is not well documented. There are numerous analyses either of the clay fraction or of sands carried by rivers, but only a few total quantitative analyses are reported in the literature. As examples, the average mineralogical composition of two large river systems, the Amazon and the Mississippi, are presented in Table 9.9. This table also includes the mean mineralogical composition of shales for comparison with river suspended sediments. The overall average of 300 samples of shales analyzed by Shaw and Weaver (1965) is 30.8% quartz, 4.5% feldspar, 60.9% clay minerals, and... 

Theoretically, a plot of S AR versus ExNa/ExCa1/2 or exchangeable sodium ratio (ESR) will produce a straight line with slope equal to KQ. The average magnitude of KG for soils of the arid west is approximately 0.015 (mmol L 1) 1/2. However, the experimental Kg appears to be dependent on pH, salt concentration, and clay mineralogy. Furthermore, the experimental KG does not appear to be constant across the various sodium loads. Commonly, as sodium load increases, KG also increases. Furthermore, as pH increases, KG decreases (Fig. 4.26). 

Sridhar Komarneni, Ph.D. is a professor of clay mineralogy at The Pennsylvania State University, University Park, Pennsylvania. 

Hurst, A. 1992. The clay mineralogy of Jurassic shales from Brora, NE Scotland. In H. van Olphen and F. Veniale (Editors), International Clay Conference, Developments in Sedimentology, Vol. 35. Elsevier, Amsterdam, pp. 677-684. 

S.I. Darmawan Wada, Effect of Clay Mineralogy on the Feasibility of Electro-kinetic Soil Decontamination Technology, Appl. Clay Sci. 20(6), 283-293, Eeb. (2002). 

The mineralogy that comprises the clay component of the soil is also critical to contamination of soils by biological and chemical threat agents. For example, ricin was sorbed to four different clay minerals as described above (Figure 4.2). Kaolinite, a 1 1 clay mineral, sorbed very little ricin. Sepiolite, a fibrous clay mineral, sorbed much more ricin. Illite, a tetrahedrally substituted 2 1 clay mineral, sorbed similar amounts of ricin as the sepiolite. The octahedrally substituted clay mineral, montmorillonite, sorbed much greater quantities than all of the other clay minerals. Even with this clay mineral, the cation that was dominantly sorbed to the clay made a difference. The Na-saturated montmorillonite sorbed more than the Ca-saturated montmorillonite. This is thought to be due to the swelling of the interlayers of the clays. Na-saturated clays swell more so than do Ca-saturated ones. Similar results are shown with aflatoxin Bj (Jaynes et al. 2007). 

Quaide, W.L., 1956. Petrography and clay mineralogy of Pliocene sedimentary rocks from the Ventura Basin, California. Ph.D. Thesis, Department of Geology and Geophysics, University of California, Berkeley, Calif. 

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