Chlorite-montmorillonite

Mica, kaolins (kaolinite and halloysite), Mg-rich chlorite, talc, montmorillonite and chlorite/montmorillonite are abundant in the host epiclastic sediments and pumiceous tuffs at Jade in the Okinawa Trough (Marumo and Hattori, 1997). 

The global distribution patterns of kaolinite, chlorite, montmorillonite, and illite in pelagic sediments are listed in Table 14.3 and illustrated in Figures 14.8 through 14.11. 

Oceanic Area Chlorite Montmorillonite Kaolinite Illite... 

Clay minerals occur in all types of sediments and sedimentary rocks and are a common constituent of hydrothermal deposits. They are the most abundant minerals in sedimentary rocks perhaps comprising as much as 40% of the minerals in these rocks. Half or more of the clay minerals in the earth s crust are illites, followed, in order of relative abundance, by montmorillonite and mixed-layer illite-montmorillonite, chlorite and mixed-layer chlorite-montmorillonite, kaolinite and septachlorite, attapulgite and sepiolite. The clay minerals are fine-grained. They are built up of tetrahedrally (Si, Al, Fe3+) and octahedrally (Al, Fe3+, Fe2, Mg) coordinated cations organized to form either sheets or chains. All are hydrous. 

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. 

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). 

K is obtained from associated K-feldspars and micas. The layer charge is increased by the reduction of iron in the octahedral sheet and incorporation of Al, entering through the ditrigonal holes in the basal oxygen plane, into the tetrahedral sheets (Weaver and Beck, 1971a Pollard, 1971). Weaver and Beck have presented evidence that indicates mixed-layer clays formed in this manner contain 20—30% chloritic layers and are actually mixed-layer illite-chlorite-montmorillonite clays. 

Chemical analyses of some mixed-layer chlorite-montmorillonites... 

The X-ray diffraction patterns for the sand and silt fractions had a nearly identical predominance of quartz and feldspar peaks. The "clay" fraction, however, showed X-ray peaks from quartz and feldspars as well as for chlorite/montmorillonite. Our use of the silt fraction in the following adsorption experiments is supported by the similarity in composition (i.e., mostly quartz and feldspars and no clays) between the silt and sand fractions. The silt fraction, more easily suspended than sand, was an indicator of the adsorption characteristics that might logically be expected of the sand fraction as well. 

The most widespread fill material is reddish brown (2.5 YR 4/4, 5 YR 4/4) loam with a minor admixture of relatively large oolitic bauxite pebbles (derived from the Late Triassic - Camian - beds) and coarse clasts of black chert. Pilot X-ray diffraction analysis revealed mostly muscovite/illite, plus mixed-layer clay minerals of illite/montmorillonite type, chlorite plus mixed-layer clay minerals of chlorite/montmorillonite type, calcium montmorillonite, and diaspore plus gibbsite, or just traces of bauxite minerals (Misic, 2000). The mineral composition is not as uniform as might be expected, and further research, intended for application of factorial analysis, is in progress. A potential sediment source area in the present Cerkniscica River basin (Fig. 1) appears obvious at first glance, but similar outcrops of bauxite and chert do also appear at other sites that are not much more remote. 

Kaolinite is present in large quantities in soils of higher elements ofrelief. In the less acidic soils of lower slopes, where solutions containing silica, magnesium and iron can enter from the slopes, the quantity of montmorillonite, especially chloritized montmorillonite and chlorite, increases. The biogeochemical cycle is generally depressed (see Table I). 

The components making up the fine-grained fractions of the terrigenous-halitic complex are essentially Mg-rich trioctahedral well-crystallized chlorites without swelling layers as well as Fe-illites, the structure of which does not contain swelling layers (see model in Fig. 2.10). At the same time there are no mixed-layer species of the chlorite-montmorillonite type which were so characteristic of the carbonate-terrigenous complex (dolomite-sulfate facies). Mixed-layer clays of the illite-montmoriUonite type also diminish throughout the complex. 

Corrensite, a mixed-layer mineral of the chlorite-montmorillonite type with an ordered structure, occurs at several levels within the Triassic Basin and in particular in the area of the Hassi R Mel deposit (Plate 15). Corrensite is a highly useful geothermal indicator in sediments (Porrenga 1967 Kiibler 1973)- In the area mentioned it starts to appear at a depth of 2.1 km and remains stable down to 2.3 km. The maximum temperatures reached were reconstructed on the basis of the appearance or disappearance of allevardite, kalkbergite and corrensite mixed-layer minerals (Fig. 8.2). Min-eralogical and crystallochemical analyses of mixed-layer clay minerals reveal the pro-... 

Corrensite is present in several genetic types as described by Kubler (1973). It has been observed in the Triassic dolomitic limestones associated with evaporites and in volcanic sandstones which experienced some burial. Correlations with other data like i o or vitrinite reflectance and the temperatures measured in the holes show that the transformation of volcanic ferromagnesian minerals into corrensite takes place at a temperature of 90-100 °C at which the haphazardly arranged layers of montmorillo-nite in the chlorite-montmorillonite structure largely disappear. Corrensite is everywhere encountered in complexes, the temperatures of which, as measured in the boreholes, went up to 148 °C. 

Brydon et al. [1961] report dioctahedral chlorite occurring with quartz and an inter-stratified chlorite-montmorillonite mineral in the AB horizon of the Alberni soil series in British Columbia. The d(060) value of the chlorite is 1.496 A. The 001 reflection at 14.15 A increases in intensity on heating at 550°C and is stable in position to 700°C. Two alternative structural formulas, depending on the estimated amount of free quartz, are given for the clay fraction containing both the chlorite and the interstratified mineral ... 

This equation has been programmed for a HIPAC 103 Computer by Sato [1965], for combinations of illite-montmorillonite, chlorite-montmorillonite, and others. 

Mixed-layer montmorillonite-chlorite has been found in fireclays in Idaho by Ponder and Keller [1959], and mixed-layer chlorite-montmorillonite-vermiculite in fireclays from Olive Hill district in Kentucky by Patterson and Hosterman [1958]. These chlorites are relatively stable to the action of ethylene glycol. Mixed-layer ilUte-chlorite has been found in the Morrison formation of the Colorado Plateau by Keller [1958, 1962] in Jurassic shales. 

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. 

The similar chlorite-montmorillonite interstratification has been identified by Di Paola [1968] from the upper cretaceous in Argentina and by Morelli [1967] in Italy (X-ray, D.T.A., chemical analysis and cation exchange data). 

Hayashi [1961] has obtained mixed-layer chlorite-montmorillonite and sericite-mont-morillonite, both regular and irregular, from altered aureoles of so-called kuroko deposits in Japan. Mitsuda [1957], from the Uku Mine Yamaguchi Prefecture, Japan, has obtained a clay giving a 28.8 A reflection, which he interprets as a regular interstratification of mont-morillonite and aluminum-chlorite. 

Interstratifications between three and more types of minerals should also be possible, e.g., illite-chlorite-montmorillonite (Weaver [1956] Powers [1957] Engelhardt et al. 

Slat, A., R. Wey, and R. Weil, 1959. Identiflcation d une argile chlorite-montmorillonite a inter-stratiflcation r6guli6re dans une roche fllonienne des Vosges. Bull. Soc.fr. Min. Crist. 82 402. Smith, W. W., 1956-1958. Some interstratifled clay minerals from basic igneous rocks. Clay Min. Bull. 3 182. 

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