Clay mineral typing

Particle size distribution Bulk density Clay mineral type pH... 

This information is reported as the percentage that each of the clay mineral type contributes to total identifiable clay mineral content of the noncarbonate clay-sized fraction of the surface sediments. These percentages were determined by x-ray diffraction, which is luiable to identify noncrystalline solids. Using this technique, clay minerals were found to comprise about 60% of the mass of carbonate-free fine-grained fraction. Most of the noncrystalline soUds are probably mixed-layer clay minerals. Carbonate was removed to facilitate the x-ray diffraction characterization of the clay minerals. In some cases, roimd off errors cause the sum of the percentages of kaolinite, illite, montmorillonite, and chlorite to deviate slightly from 100%. 

The 1 1 clay-mineral type consists of one tetrahedral sheet and one octahedral sheet. These two sheets are approximately 7 A thick. This two-sheet type is divided into kaolinite (dioctahedral) and serpentine (trioctahedral) groups. The kaolinite minerals are all pure hydrous aluminum silicates. The different members are characterized by the manner of stacking of the basic 7 A layers (Brindley, 1961b). 

White, W.A., 195 3. Allophanes from Lawrence County, Indiana. Am. Mineralogist, 38 634-642. Whitehousc, U.G. and McCarter, R.S., 1958. Diagenetic modification of clay mineral types in artificial sea water. Proc. Natl. Conf. Clays Clay Miner., 5th-Natl. Acad. Sci. Natl. Res. Counc., Publ., 566 81-119. 

Clay mineral Type CEC ( cmolc kg- ) Surface area (m g- ) Expanding non-expanding c spacing Interlayer nm binding ... 

By contrast, smectite clays develop in poorly drained sites. On the basaltic island of Hawaii, soil clay mineral type changes in the sequence smectite-kaoli-nite-gibbsite as rainfall amount increases (Fig. 4.18). A similar, generalized zona-tion has been proposed for clay mineral distribution with depth in soils, again based on the degree of leaching (Fig. 4.19). 

Fig. 1.4 Schematic diagram of clay mineral types Left According to the combination of tetrahedral- and octahedral-coordinated sheets Right Diagrammatic sketch of the structure of smectite (after Hillier 1995 and Grim 1968).

FIGURE 5.11 Th/K versus PE crossplot for clay mineral typing. Baker Atlas (1992). 

Ostrom, M. E., 1960. An interlayer mixture of 3 clay mineral types from Hector, California. Am. Mineralogist 45 886. 

Clays are composed of extremely fine particles of clay minerals which are layer-type aluminum siUcates containing stmctural hydroxyl groups. In some clays, iron or magnesium substitutes for aluminum in the lattice, and alkahes and alkaline earths may be essential constituents in others. Clays may also contain varying amounts of nonclay minerals such as quart2 [14808-60-7] calcite [13397-26-7] feldspar [68476-25-5] and pyrite [1309-36-0]. Clay particles generally give well-defined x-ray diffraction patterns from which the mineral composition can readily be deterrnined. 

Two classes of clays are known [3] (i) cationic clays (or clay minerals) that have negatively charged alumino-silicate layers balanced by small cations in the interlayer space (e.g. K-10 montmorillonite) and (ii) anionic clays which have positively charged brucite-type metal hydroxide layers balanced by anions and water molecules located interstitially (e.g. hydrotalcite, Mg6Al2(0H)igC034H20. 

Main gangue minerals of the Se-type deposits comprise quartz, adularia, illite/ smectite interstratified mixed layer clay mineral, chlorite/smectite interstratified mixed layer clay mineral, smectite, calcite, Mn-carbonates, manganoan caleite, rhodoehrosite, Mn-silicates (inesite, johannsenite) and Ca-silicates (xonotlite, truscottite). 

In eomparison, the Te-type deposits contain fine-grained quartz, chalcedonic quartz, sericite, barite, adularia, ehlorite/smectite interstratified mixed layer clay mineral and rarely anatase. Carbonates and Mn-minerals are very poor in the Te-type deposits and they do not coexist with Te-minerals. Carbonates are abundant and barite is absent in the Se-type deposits. The grain size of quartz in the Te-type deposits is very fine, while large quartz crystals are common in the Se-type deposits although they formed in a late stage and do not coexist with Au-Ag minerals. 

Principal gangue minerals in base-metal vein-type deposits are quartz, chlorite, Mn-carbonates, calcite, siderite and sericite (Shikazono, 1985b). Barite is sometimes found. K-feldspar, Mn-silicates, interstratified mixed layer clay minerals (chlorite/smectite, sericite/smectite) are absent. Vuggy, comb, cockade, banding and brecciated textures are commonly observed in these veins. 

D and 5 0 data on fluid inclusions and minerals, 8 C of carbonates, salinity of inclusion fluids together with the kind of host rocks indicate that the interaction of meteoric water and evolved seawater with volcanic and sedimentary rocks are important causes for the formation of ore fluids responsible for the base-metal vein-type deposits. High salinity-hydrothermal solution tends to leach hard cations (base metals, Fe, Mn) from the country rocks. Boiling may be also the cause of high salinity of base-metal ore fluids. However, this alone cannot cause very high salinity. Probably the other processes such as ion filtration by clay minerals and dissolution of halite have to be considered, but no detailed studies on these processes have been carried out. 

Nagasawa, K Shirozu, H. and Nakamura, T. (1976) Clay minerals as constituents of hydrothermal metallic vein-type deposits. Mining Geology Special Issue, 7, 75-84 (in Japanese). 

Shirozu, H. (1974) Clay minerals in altered wall rocks of the Kuroko-type deposits. In Ishihara, S. (ed.). Geology of Kuroko Deposits, Mining Geology Special Issue, 6, 303-310. 

Sudo, T. (1954) Types of clay minerals closely a.s.sociated with metalliferous ores of the epithermal type. Sci. Repts. Tokyo Kyoiku Daigaku, Sen C, 3, 173-197. 

Osmotic swelling is a second type of swelling. Where the concentration of cations between unit layers in a clay mineral is higher than the cation concentration in the surrounding water, water is osmotically drawn between the unit layers and the c-spacing is increased. Osmotic swelling results in larger overall volume increases than surface hydration. However, only certain clays, like sodium montmorillonite, swell in this manner. 

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