Illite occurrence

Porrenga, 1968). These minerals are related to illite, both in type of occurrence and chemistry as we will see later. 

In zones of hydrothermal alteration it is apparent that the formation of dioctahedral montmorillonites is limited by temperature. They almost never occur in the innermost zone of alteration, typically that of sericitization (hydro-mica or illite), but are the most frequent phase in the argillic-prophylitic zones which succeed one another outward from the zone where the hydrothermal fluid is introduced in the rock. Typically, the fully expandable mineral is preceded by a mixed layered phase (Schoen and White, 1965 Lowell and Guilbert, 1970 Fournier, 1965 Tomita, et al., 1969 Sudo, 1963 Meyer and Hemley, 1959 Bundy and Murray, 1959 Bonorino, 1959). However, temperature is possibly not the only control of expandable clay mineral occurrence, the composition of the solutions and the rock upon which they act might also be important. It is possible that high magnesium concentrations could form chlorite, for example, instead of expandable minerals. 

Weaver and Beck, 1971 Dunoyer de Segonzac, 1969 van Moort, 1971 and Hower, et al.. 1976). This is especially true for alkalis. Thus the occurrence of illite or mica is not a function of bulk composition but one... 

The stability conditions of corrensite then cover the low grade clay mineral facies (near 100°C) and extend well into the calcium zeolite-prehnite, muscovite-chlorite facies. In pelitic rocks the upper limit will be somewhat lower near the illite-chlorite zone. It is evident that composition of a rock governs the occurrence of corrensite. It can be... 

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). 

Triplehorn, D.M., 1967. Occurrence of pure, well-crystallized 1M illite in Cambro-Ordovician sandstone from Rhourde El Baguel Field, Algeria. J. Sediment. Petrol, 37 879-884. 

Factor-1 samples contain high concentrations of many trace elements, particularly boron and the transition elements Co, Cu, Mo, Ni, Pb, Zn, and V (Table III). These samples also contain illite (CR-2 core) and relatively high concentrations of analcime and oil (both cores) which suggests that adsorption of trace elements onto clay, altered tuffaceous material, and (or) organic matter may be important 1n controlling the distribution of these trace elements. The sulfide phase also may control the occurrence of these metals (10-11). Factor 1 samples also... 

Because they are the dominant mineral in shales, illites, and illite-smectites (see below) are the most abundant of all the clays. Illites are defined as micalike materials less than 2 yttm in size, which, like the micas, have a basal spacing of 10 A (Drever 1988). Most illites are dioctahedral and structurally similar to muscovite, although some are trioctahedral like biotite. Illites contain less and Al and more Si than muscovite. They also usually contain some Mg + and Fe, The irregularity of occurrence of interlayer K+ makes bonding between the layers weaker than in muscovite. Illitic clays... 

The formation and survival of unstable or metastable micas and clays in sediments and soils at low temperatures reflects kinetic as well as thermodynamic factors. First, the rates of reactions involving solid-aqueous and especially solid-solid transformations in dilute solutions are very slow at low temperatures (most natural waters are dilute )- The slow kinetics of clay transformations reflects small differences in free energy between stable and metastable clays. Also, the occurrence of specific clays is related to the chemistry and crystal structure of source minerals. Thus, illite often results from the weathering of muscovite, and vermiculite results from the weathering of biotite (cf. Drever 1988), consistent with the similar chemistries and structures of these pairs of T 0 T minerals. 

The carbonates are mainly calcite, dolomite, or siderite. The occurrence of calcite is frequently bimodal. Some calcite occurs as inherent ash, while other calcite appears as thin layers in cleats and fissures. Iron can be present in small quantities as hematite, ankorite, and in some of the clay minerals such as illite. In addition to the more common minerals, silica is present sometimes as sand particles or quartz. The alkalies are sometimes found as chlorides or as sulfates but probably most often as feldspars, typically orthoclase and albite. In the case of lignites, unlike bituminous and subbituminous, sodium is not present as a mineral but is probably distributed throughout the lignite as the sodium salt of a hydroxyl group or a carboxylic acid group in humic acid. Calcium, like sodium, is bound organically to humic acid. Therefore, it too is uniformly distributed in the sample [10]. 

A zonal distribution of clay minerals occurs in the East Hachimantai thermal area, characterized by smectite - illite/smectite - illite/chlorite, with the latter tending to occur in the vicinity of hot upflow zones. The smectite is characteristically Ca-smectite. The occurrence of Ca-bearing zeolite minerals, such as laumontite and wairakite correspond to the presence of hot hydrothermal fluids near in the center of the geothermal resource. In contrast, Na-smectite and Na-zeolite (e.g. clinoptilolite - mordenite - analcime) in marine sediments and pyroclastic sequences tend to envelope the main thermal area. Inoue et al. (2001) and Hara et al. (2001) have described the style and distribution of alteration in the Hachimantai area. The Na-enriched alteration zones contain higher Na concentrations than... 

Although much is known about the minerals in coal, much remains to be learned about their occurrence, abundance, origin, and composition. For example, the type of clay mineral in a coal, whether montmorillonite or illite, determines how a coal will react when burned. 

The occurrence of clay minerals in the great soil groups has been reviewed (Jackson [1959], Grim [1968], Millot [1970]). The abundance and frequently even the predominance of micaceous minerals in the clay fraction of numerous soil types have been confirmed by these articles. Micas and their degraded forms (illite, hydrous mica, mixed-layer minerals with micaceous components) were found to prevail in the clay fraction of arctic raw soils, brown earth s, prairie soils, chernozems, chestnut soils, syrozem, alkali soils, intrazonal mountain soils, and different azonal soils. Remarkable contents of illite have also been observed in the clay fractions of gray-brown, gray, red, and red-yellow podzolic soils. 

The development of vermiculite minerals in soils at the expense of micas is now well established as a common phenomenon, more particularly by the work of Jackson and his collaborators e.g., Jackson et al. [1952], Schmehl and Jackson [1956], Jackson [1959,1963], Brown and Jackson [1958]) as well as by others e.g., Fieldes and Swindale [1954], Rich [1958], Cook and Rich [1962], Millot and Camez [1963], Nelson [1963]). In spite of the frequent occurrence of dioctahedral clay vermiculites in soils, dioctahedral clay micas, in general, appear to resist decomposition better than their trioctahedral counterparts and, where direct comparison is possible, the dioctahedral type may remain unaffected, whereas the trioctahedral mica in the same profile is almost completely altered (Mitchell [1955]). Vermiculitelike minerals, however, may also develop in soils by other routes, for example, from montmorillonite (Bundy and Murray [1959], Jackson [1963]) or from chlorite (Droste and Tharin [1958], Brown and Jackson [1958], Droste et al. [1962], Millot and Camez [1963]). Such alterations are reversible, and they depend on a chemical equilibrium between the mineral and the soil solution. Hence clay chlorites, illites, and montmorillonites may develop from clay vermiculites in an appropriate environment, and intermediate types are common. The alteration of clay vermiculites to kaolinite in podzols has also been proposed (Walker [1950], Brown [1953], Jackson et al. [1954], McAleese and Mitchell [1958a]). 

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