Chlorite occurrence

Aluminum chlorite, (Al,Fe)4(Si,Al)402Q(0H)g, in which a gibbsitelike interlayer proxies in part for the bmcitelike interlayer, is being discovered in increasing occurrences and abundance (11,141). Chloritelike stmctures have been synthesi2ed by precipitation of Mg and Al between montmorillonite sheets (143). Cookite [1302-92-7], an aluminous chlorite containing lithium, has been found in high alumina refractory clays and bauxite [1318-16-7] (139). 

Shikazono et al. (1998) found that carbonates are common alteration minerals in the Uwamuki mine area of Hokuroku district and carbonate alteration superimposed on chlorite alteration. They showed that the mode of occurrences and the Mg/(Mg -(-... 

Trioctahedral chlorite occurs commonly in geothermal and hydrothermal areas, whereas the occurrence of dioctahedral chlorite is very limited. For instance, donbasite... 

The dominant clay mineral at high latitudes is chlorite. In addition to ice rafting, lithogenous materials are transported in the polar oceans by rivers and winds. Polar seas are also characterized by diatomaceous oozes due to the occurrence of upwelling supported by divergence at 60°N and 60°S. 

Silicate minerals that usually occur as spherulitic aggregates of fibers have formed as a result of the alteration of the many minerals subsumed within the category of biopyriboles. Alteration of the micas under hydrothermal conditions produces compositional variants on recrystallization such as hydrous muscovite. Some of these samples have been labeled asbestiform, probably because they are found in veins that criss-cross rock masses. Fibrous micaceous minerals also occur as discrete disseminated particles, although few detailed analyses of crystallites from the disperse occurrences have been made. Fibrous mica found in veins usually grades (composition-ally) into members of the serpentine mineral group, the clays or the chlorites. 

Occurrence of Chlorite and Chlorate Ions in Finished Water From Utilities That Use Chlorine Dioxide... 

Eh and pH at which the process takes place. In both cases the role of organic material is evident and similar, acting as a motor in changing the aspect of the silicate in the pellet both in chemistry and mineralogy from that of the enclosing sediment. The reasons for the development of one mineral species or the other are at the moment somewhat obscure but, considering the similarity of the occurrence, the mechanism is probably the same. With this in mind the analysis which follows for sedimentary glauconites can be considered applicable for sedimentary 7 X chlorite pellets. 

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. 

The occurrence of kaolinite is generally erratic but in the terrigenous sediments (Muffler and White, 1969) it can apparently react with dolomite to form the assemblage calcite + chlorite between 120-180°C. Expandable chlorite was noted in shear zones, and iron-rich chlorite is common in most of the rocks becoming more evident at greater depths. In the terrigenous rocks observed, the apparent alumina content of chlorite decreases with depth. Alkali zeolites have been observed at temperatures up to 100°C in the deeply buried rocks. 

One aspect of sedimentary 7 8 chlorite formation which is particularly interesting is the fact that these minerals are never found forming at depths greater than 80 meters in recent sediments. Porrenga (1967b) thinks that they are characteristic of tropical sediments and their formation is thus temperature dependent. This appears invalid since they are known to form in recent sediments in a Scottish loch (Rohrlich, e al.. 1969). Nevertheless there does seem to be a bathymetric control on their occurrence. This is probably not a pressure effect but more likely some sort of factor related to organic activity in the sediments which is controlled by the biotic factors of sea depth, temperature, nutrients, etc. 

Although the information available from synthetic studies strongly indicates a P-T control of the chlorite polymorph, natural minerals appear to exhibit both polymorph, 7 and 14 8, at low temperature. Most diagenetic chlorites correspond to a 7 8 polymorph. However, there are occurrences especially in deep ocean sediments of a 14 8 phase. The contradiction cannot be resolved with the information available at present. It is probably reasonable to assume that the 7 8 polymorph stable for all chlorite compositions (i.e., various Fe +, Mg, A1 ratios) and that the 14 8 forms are metastable at low temperatures. However, this is certainly not definitive. 

Because the compositions are basic, the expanding minerals are trioctahedral and they are apparently associated in all facies with chlorite. The occurrence of a regularly interstratified montmorillonite (saponite) -chlorite mineral, corrensite, is typified by an association with calcic zeolites and albite. Temperature measurement in the "hydrothermal" sequences at several hundred meters depth indicate that the ordered, mixed layered mineral succeeds a fully expandable phase between 150-200 C and this ordered phase remains present to about 280°C. In this interval calcium zeolites disappear, being apparently replaced by prehnite. The higher temperature assemblage above corrensite stability typically contains chlorite and epidote. 

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... 

Figure 41. Phase diagram for the extensive variables R -R -Si combining the data for synthetic magnesian chlorites and the compositional series of natural sepiolites and palygorskites. Numbers represent the major three-phase assemblages related to sepiolite-palygorskite occurrence in sediments. Chi = chlorite M03 = trioctahedral montmorillonites M02 = dioctahedral montmorillonite Sep = sepiolite Pa = palygorskite Kaol = kaolinite T = talc.

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

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). 

The very narrow region of the constraint space where oscillations could occur in this system was not found until after the chlorite-iodate-arsenite oscillator had been discovered. Its occurrence is shown in the cross-shaped diagram for chlorite-iodide (Fig. 8.)... 

There have been tremendous strides made recently towards understanding how volatiles in general and water in particular is transported and stored in the mantle. This progress is based on research on a number of fronts studies of mantle-derived samples have provided insight into the nature and occurrence of hydrous phases such as amphibole, mica, and chlorite, and have provided constraints on the capacity of nominally anhydrous minerals (NAMs) such as olivine, pyroxenes, and garnet to contain water by a variety of substimtion mechanisms. Experimental studies on mantle-derived magmas have provided constraints on volatile contents in their source regions. Other studies have constrained the pressure, temperature, and composition conditions over which hydrous phases are stable in the mantle. 

Pyrite averages 0.2 vol%, and only in a few samples forms up to 1.3 vol%. It shows two occurrence habits (i) fine crystals (< 2. im) or framboids scattered in kaolinized or chloritized detrital clays and micas, or engulfed by coarse carbonate cements (Fig. 15E) and (ii) coarsely crystalline (up to 200 pm across), intergranular replacive cement. 

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