Structural chlorite

An additional structural variant for clay minerals is the chlorite-type structure. Chlorites are similar to the pyrophyllite-type structures with two tetrahedral sheets and an octahedral sheet making up each layer. Instead of alkali or alkaline earth interlayer cations, chlorites contain a brucite (Al-Mg hydroxide) layer between successive pyrophyllite-type layers [18]. 

Figure 9.12 Schematic representation of the structures of muscovite mica, (K2Al4(Si6Ali)02o(OH)4], hydrated montmorillonite, [Al4Sig02o(OH)4].xH20 and chlorite, (MgioAl2(Si6Al2)02o(6H)i6], see text.

Write the 1 ewis structures of (a) water, H20 (b) methanal, H2CO and (c) the chlorite ion, CI02. Use the rules in Toolbox 2.1 note that we must add one electron for the negative charge of C102. ... 

Write the Lewis structure, including typical contributions to the resonance structure (where appropriate, allow for the possibility of octet expansion), for (a) dihydrogen phosphate ion (b) chlorite ion (c) chlorate ion (d) nitrate ion. 

The variations in Fe and Mg contents of the 14 A Fe-chlorite-14 A Mg-chlorite solid solution are considered here. However, structural formulae for chlorite are not as simple as those considered here. As mentioned by Walshe and Solomon (1981), Stoesell (1984), Cathelineau and Nieva (1985) and Walshe (1986), chlorite solid solution may be represented by six components, and accurate thermochemical data on each end-member component at the hydrothermal conditions of concern are necessary to provide a far more rigorous calculation of the equilibrium between chlorite and hydrothermal solution. However, the above argument demonstrates that the composition of chlorite is a highly useful indicator of physicochemical conditions of hydrothermal solution and extent of water-rock interaction. 

Some interesting organic chemistry is involved in the synthesis of chlorite-resistant brighteners for acrylic fibres. None of these compounds is easy to make and methods for preparation of the starting materials can be complex. Much manufacturing know-how is involved. One route for introduction of the benzimidazole nucleus into structure 11.55 is shown in Scheme 11.22. Preparation of the chemically rather simpler benzoxazole grouping in product 11.56 is shown in Scheme 11.23. 

Fig. 2 Molecular structures of regulated DBPs (THMs, HAAs, bromate, and chlorite)...

In drill hole GP07-92, a strong VIRS response to sericite and chlorite occurs in host rocks up to 15 m structurally above a quartz vein intercept, whereas a sample of lithic greywacke, 5 m below a ca. 3 m wide quartz veined zone (22.2-25.9 m) yields... 

The Key Anacon deposits are exhalative deposits with metal zonation grading from a pyrite-chalcopyrite-pyrrhotite zone in the footwall, through a pyrite-sphalerite zone in the main parts of the deposits, to pyrite-sphalerite-galena zone in the upper and vent-distal parts of the system (cf. Petruk 2000). At the base, these deposits consist of structurally attenuated and dismembered stockwork veins and disseminations of chalcopyrite and pyrrhotite, in a matrix of chlorite. 

Fig. 2.13 The 1 1 and 2 1 layer arrangements in the sheet structure minerals and the (010) view of the structures of the serpentine, clay, talc, pyrophyllite, mica, and chlorite minerals. X = layer charge per formula unit. [From Bailey (1980), Fig 1.1, p. 3 Fig 1.2, p. 6.1...

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). 

Bailey, S. W., and B. E. Brown (1962). Chlorite polytypism—regular and semirandom one-layer structures. Amer. Min. 47 819-850. 

The chlorites are a group of minerals with a layered structure, which in many respects resemble the micas. The monocUnic structure of chlorite is one of regularly alternating talc-Uke Y6Z802o(OH)4 and brucite-like Y6(OH)i2 sheets. 

Table 2 gives temperatures of montmorillonite stability which are established by the experiments reported. The most important criteria used is reaction reversal this lacking, length of the experiments and variety of starting material was taken into consideration. Two points are important among micas and other phyllosilicates only kaolinite, serpentine and muscovite are stable to very low temperatures. All trioctahedral 2 1 structures break down to expandable phases at low temperatures (bio-tites) or to 1 1 structures plus expandable phase (chlorites). 

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