Chlorite-vermiculite

Vermiculites exist in various stages of dehydration. Because of the similar dimensions of the water-cation layer in vermiculite and the brucitelike layer in chlorite, vermiculites can be confused with the chlorites. The common substitutions of Fe" or Fe for Mg (in either the water or octahedral sheet of vermiculites), and AF for Si (in the tetrahedral sheets), as well as the hydration variations, present enormous potential for structural distortion in these types of minerals. Fibrous vermiculite was described by Weiss and Hofmann (1952). 

If we consider three components, the phases will be arranged as in Figure 48a at conditions of initial burial. The solid solution series are somewhat abbreviated for simplicity. The phase relations are dominated by fully expanding and mixed layered minerals which cover a large portion of the compositional surface. Notably two dioctahedral expandable minerals exist as does a large undefined series of trioctahedral phases designated as expanding chlorite, vermiculite and trioctahedral montmorillonite. 

JOHNSON (L.J.), 1964. Occurrence of regularly interstratifled chlorite-vermiculite as a weathering product of chlorite in a soil. Amer. 

Mixed-layer illite-montmorillonite is by far the most abundant (in the vicinity 90%) mixed-layer clay. The two layers occur in all possible proportions from 9 1 to 1 9. Many of those with a 9 1 or even 8 2 ratio are called illites or glauconites (according to Hower, 1961, all glauconites have some interlayered montmorillonite) and those which have ratios of 1 9 and 2 8 are usually called montmorillonite. This practice is not desirable and js definitely misleading. Other random mixed-layer clays are chlorite-montmorillonite, biotite-vermiculite, chlorite-vermiculite, illite-chlorite-montmorillonite, talc-saponite, and serpentine-chlorite. Most commonly one of the layers is the expanded type and the other is non-expanded. 

Mg-rich chlorites do not seem to form readily in low-temperature marine environments. Mixed-layer chlorite-vermiculites form fairly easily in magnesium-rich environments but complete development of the brucite sheets must be considerably more difficult. Mixed-layer chlorite-vermiculite is the predominant clay in the Lower Ordovidian limestones and dolomites of southern United States, usually over a thousand feet thick and extending over 500,000 square miles, yet very little chlorite is present (Weaver, 1961a). These mixed-layer clays and others like them appear to have formed on extensive tidal flats where the clays were exposed to alternating evaporitic... 

Most of the chlorite-like material formed in soils is dioctahedral rather than trioctahedral. In the process of weathering, illite and muscovite are stripped of their potassium and water enters between the layers. In these minerals and in montmoril-lonites and vermiculites, hydroxides are precipitated in the interlayer positions to form a chlorite-like mineral (Rich and Obenshain, 1955 Klages and White, 1957 Brydon et al., 1961 Jackson, 1963 Quigley and Martin, 1963 Rich, 1968). Al(OH)3 and Fe(OH)3 are likely to be precipitated in an acid to mildly basic environments and Mg(OH)2 in a basic environment. The gibbsite sheets in the soil chlorites are seldom complete and the material resembles a mixed-layer chlorite-vermiculite. The gibbsite may occur between some layers and not between others or may occur as islands separated by water molecules. 

A number of Al chlorites in which both octahedral sheets are dioctahedral have recently been described. Dioctahedral Al chlorites have been reported in bauxite deposits (Bardossy, 1959 Caillere, 1962). These chlorites appear to have been formed by the precipitation-fixation of Al hydroxide in the interlayer position of stripped illite or montmorillonite. A similar type of chlorite, along with dioctahedral chlorite-vermiculite, occurs in the arkosic sands and shales of the Pennsylvanian Minturn Formation of Colorado (Raup, 1966). Bailey and Tyler (1960) have described the occurrence of dioctahedral chlorite and mixed-layer chlorite-montmorillonite in the Lake Superior iron ores. Hydrothermal occurrences have been described by Sudo and Sato (1966). 

So-called mixed-layer chlorite-vermiculites are common in marine sedimentary rocks, but it appears that in most, if not all, instances the vermiculite layers will not contract when saturated with potassium and the expanded layers are probably some form of smectite. These clays probably formed from volcanic material, montmorillonite or chlorite, rather than from the degradation of micas and illites. 

The most common type of mixed-layer clay is composed of expanded, waterbearing layers and contracted, non-water-bearing layers (i.e., illite-montmorillonite, chlorite-vermiculite, chloritc-montmorillonite). Most of these clays form by the partial leaching of K or Mg (OH)2 from between illite or chlorite layers and by the incomplete adsorption of K or Mg(OH)2 on montmorillonite- or vermiculite-like layers. They most commonly form during weathering or after burial but are frequently of hydro-thermal origin. 

Bradley, W.F. and Weaver, C.E., 1956. A regularly interstratified chlorite-vermiculite clay mineral. Am. Mineralogist, 41 497-504. 

Clay minerals Illite, kaolinite, halloysite, smectites, chlorites, Vermiculites, palygorskite, mixed-layer clays, etc. 

This process comprises dissolution of alumino-silicate minerals, and is the basis for much of the discussion concerning the development of saprolites and associated weathering products. Although conditions at the weathering front may initially favour the formation of micaceous clays (e.g. chlorite, vermiculite) and smectite, small quantities of gibbsite may also be formed, and, eventually, kaolinite can come to dominate those free-draining profiles where there is an adequate water supply. 

Banfield JF, Murakami, T (1998) Atomic-resolution transmission electron microscope evidence for the mechanism by which chlorite weathers to 1 1 semi-regular chlorite-vermiculite. Am Mineral 83 348-357... 

Tailings Mineralogy. Tailings minerals consist of sand, clays, amorphous oxides, and trace metals. The sand is 97.5-99% Si02, 0.5-0.9% Al203, and 0.1-0.9% Fe (4, 27, 28). The oil sands, and hence the clay minerals found in the fine tails suspension, come from the McMurray Formation. The majority of clays in this formation are kaolinite and illite with traces of smectites, chlorite, vermiculite, and mixed-layer clays (5, 29). The upper McMurray Formation has a larger amount of smectites, whereas the lower McMurray Formation has larger amounts of vermiculite and mixed-layer clays. However, in both areas, kaolinite and illite are still the predominant clay minerals (5). 

In addition to swelling chlorite (vermiculite) there is also in association with mixed-layer minerals of the ilUte-montmorillonite type (sometimes Fe-bearing) a chlorite that is unstable on thermal treatment. The diffractogram of oriented samples is char-... 

The clay mineral spectrum is characterized by the paragenesis of dioctahedral chlorites exhibiting primary crystallochemical features with dioctahedral illites sometimes containing swelling layers. This association is quite typical for continental deposits or those from brackish-water basins. In addition to chlorites with a stable structure we also observe swelling chlorites which are unstable on heat treatment and which occupy a sort of intermediate position between chlorite and vermiculite. It appears to represent a process of incomplete crystallization of minerals of the chlorite-vermiculite group in continental basins or under freshwater to brackish conditions. The minerals may thus be considered as metastable intermediate forms. 

Six surfactants/cosolvents were selected for the evaluation program on the basis of (a) solution chemistry, (b) proven ability to desorb/solubilize PAHs from soil particle surfaces in previous studies, (c) human health and environmental protection, and (d) compatibility with in situ electrochemical remediation technique. The chosen surfactants/cosolvents were (a) 3% Igepal CA-720, (b) 5% Igepal CA-720, (c) 5% Triton X-100, (d) 3% Tween 80, (e) 40% ethanol, and (f) a mixture of 40% ethanol and 5% Igepal CA-720. Two clayey soils, kaolin and glacial till, were selected for the study. Kaolin consists mainly of kaoUnite clay mineral, while glacial till consists of a combination of different soil minerals including quartz, feldspar, carbonates, iUite, chlorite, vermiculite, and trace amounts of smectite. 

There are also the other reactive aggregates, namely gneiss and mica containing shales [41], In the interfacial transition zone, in the vicinity of aggregate surface— kaolinite and hydromicas, while from cement paste side—gel of sodium-calcium silicate hydrate, respectively are formed. However, in the case of serpentine concrete deterioration is due to the formation of brucite [75]. The clay minerals, such as chlorites, vermiculite, as well as micas and feldspars, are also included to reactive aggregate components. 

Micas are common or dominant in many arid soils (McNeal and Sansoterra [1964] Al-Rawi et al. [1969]). Even in the old soils of the Piedmont of the U.S.A., micas are common, although there is much evidence of weathering to vermiculite or a chloritized vermiculite (Rich [1958], Weed and Nelson [1962]). Micas are reported in nearly all analyses of soil clays, other than those derived from amorphous volcanic material and those extensively weathered, i.e., laterites. Since these publications rarely give any further information concerning the mica, little is gained in citing many of these references. 

With these reservations in mind, the approximate range of cation exchange capacities of the vermiculite group can be written as 120 to 200 meq/100 g air-dry Mg-vermiculite. A more satisfactory basis would be to record the exchange capacity as meq/100 g interlayer-water-free and interlayer-cation-free mineral (Walker [1965]), and on this basis, the vermiculites range approximately from 140 to 240 meq. Values of cation exchange capacity below those quoted above have been reported, but their validity is in considerable doubt. These low values have invariably been obtained, not from pure vermicuUtes, but from mixed-layer minerals such as hydrobiotite or chlorite-vermiculite, a correction being applied for the proportion of non-vermiculite layers estimated to be present. The error involved in such corrections is considerable. 

The citrate extract contained alumina as well as iron oxide, so Tamura considers that the structure is stabilized by the two oxides. The indication is that the vermiculite-illite interstratification is changing to a chlorite-illite, or chlorite-vermiculite-illite system. 

Regular mixed-layer chlorites similar probably to corrensite have been found in various types of limestones, dolomitic limestones, calcareous and quartzitic rocks in the lower part of the Oquirrh formation in Utah by Tooker [1960] and in uranium-containing carbonate rocks from the Cumberland Plateau, Tennessee, by Peterson [1961]. (This mineral was interpreted as a 1 1 regular chlorite-vermiculite interstratification.)... 

A regular chlorite-vermiculite interstratification has been reported by Slat et al. [1959] from an ore-bearing rock of the Vosges, France. This particular mineral gives a 23.9 A reflection on heating. Alietti [1958] has reported interstratifications of saponite-talc, chlorite-saponite, and chlorite-vermiculite in serpentine rocks of Monte Chiaro in Italy and has also (1963) reported a chlorite-montmorillonite interstratification in Alpine and Appennine felspathic rocks. 

Nakahira and Sugiura [1960] have studied a regular mixed-layer chlorite-vermiculite mineral from an alteration zone of tertiary mudstones in the Noto Peninsula, Japan. It gives a 29.2 A reflection plus a series of rational orders. The (060) reflection is at 1.53 A suggesting a trioctahedral chlorite-vermiculite interstratification. 

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