Sediments and sedimentary rocks

The Fe content of sediments varies greatly with the type of rock (Wedepohl, 1969 a). Sandstones contain ca. 10 g kg Fe, claystones ca. 50 g kg and carbonatic rocks ca. 4 g kg Fe. In recent deep sea sediments Fe contents are low in carbonates (9 g kg ), but high in clays (65 g kg ). Sedimentary iron minerals belong to the groups of oxides, carbonates, clay silicates and sulphides. In addition, Fe is a common impurity in other sedimentary minerals. 

Sediments contain detrital and neoformed Fe oxides. Among the detrital oxides are those which survived weathering due to their high stability in surface environ- 

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Dean WE, Jr. Determination of carbonate and organic matter in calcareous sediments and sedimentary rocks by loss on ignition-comparison with other methods. J. Sediment. Petrol. 1974 44 242-248. 

During chemical weathering, rocks and primary minerals become transformed to solutes and soils and eventually to sediments and sedimentary rocks. 

Lithium isotope studies of sediments and sedimentary rocks have thus far concentrated on marine clastic and carbonate material. No systematic description of the effects of diagenetic processes on sediments has been made. Clay rich sediments are important to Li budgets in near-surface systems, as they concentrate Li relative to marine carbonates, which are among... 

Hagiwara (2000) completed a reconnaissance survey of Se isotope variation in marine sediments and sedimentary rocks (Table 4). The most important observation was a lack of strong enrichment in lighter isotopes in most shale samples and three Black Sea sediments. It appears that near-surface alteration has altered Se isotope ratios in some cases. All of the Phosphoria formation samples were probably altered by deep groundwater or hydrothermal... 

Following burial, marine sediments are recycled via two pathways a crustal route or a mantle route. In the crustal route, burial followed by diagenesis, catagenesis, and metagenesis transfers sediments into either sedimentary or metamorphic rocks. These rocks are eventually uplifted onto land by crustal motions associated with plate tectonics. In the mantle recycling route, sediments and sedimentary rocks are subducted at... 

Cracking reactions Chemical reactions that occur during catagenesis and metagenesis in marine sediments and sedimentary rocks. During this process, petroleum compounds are formed as hydrocarbons are broken off heteroatomic macromolecules. 

Migration The movement of petroleum through marine sediments and sedimentary rock as a result of overlying pressure. 

Chester R, Green RN (1968) The infrared determination of quartz in sediments and sedimentary rocks. Chem Geol 3 199-212... 

Our knowledge about the forms and genesis of neoformed Fe " oxides in sediments and sedimentary rocks is still rather limited because the low concentrations and poor crystallinity of these oxides hinder their identification and description. Two groups of Fe-containing sediments, whose Fe oxides have, however, attracted more interest than usual, are red beds and sedimentary iron ores (Fiichtbauer, 1988). 

Bustin, R. M. Wust, R. A. J. 2003. Maturation, organic. In Middleton, G. V. (ed) Encyclopedia of Sediments and Sedimentary Rocks. Kluwer Academic Publishers, Dordrecht, 424-429. 

CO, SC ), or the occurrence of the minerals is sufficiently rare to represent a special case—the various halide salts, for example. However, dolomite presents a special problem in that the existence of Mg is important to silicate equilibria under consideration. The main trouble here is that the conditions of crystallization and stability of dolomite in sediments and sedimentary rocks is imperfectly known, thus leaving a question as to its influence on silicates or the influence of silicates on its presence. One is forced more or less to ignore the importance of dolomite at present. This does not mean that it can be ultimately excluded from a complete discussion of clay mineral stability. 

The forms of SiC found in sediments and sedimentary rocks are quite varied but those which could be suspected of near surface origin are generally as follows quartz, chalcedony, opal, amorphous gels and ionic forms in solution. Natural occurrences indicate that the solid forms of silica precipitate which has crystallized after the time of initial deposition (Siever, 1962). 

Although gibbsite and kaolinite are important in quantity in some soils and hydrothermal deposits, they have diminishing importance in argillaceous sediments and sedimentary rocks because of their peripheral chemical position. They form the limits of any chemical framework of a clay mineral assemblage and thus rarely become functionally involved in critical clay mineral reactions. This is especially true of systems where most chemical components are inert or extensive variables of the system. More important or characteristic relations will be observed in minerals with more chemical variability which respond readily to minor changes in the thermodynamic parameters of the system in which they are found. However, as the number of chemical components which are intensive variables (perfectly mobile components) increases the aluminous phases become more important because alumina is poorly soluble in aqueous solution, and becomes the inert component and the only extensive variable. 

In sediments and sedimentary rocks lMd is the predominant polymorph of illite which indicates a diagenetic origin for more of the material. 

The mineral types familiar in sediments and sedimentary rocks are present micas, mica-like phases, fully expandable phases and mixed layered series. In a sense, celadonite mica is isolated from dioctahedral mica by a multiphase zone where montmorillonite is stable with a feldspar and mica. It is evident that the only way to. produce celadonite mica under high potassium concentrations is by having a proper bulk composition toward that of celadonite. The possibility of producing celadonite in a potassium deficient system, i.e., where montmorillonite coexists with a non-alkali bearing phase, has not yet been studied experimentally. 

It is obvious then that A1 is not synonymous with Fe in sedimentary mica-like minerals. The increasing influence of trivalent iron in a sedimentary system will obviously provoke the crystallization of a specific mineral series which is not contiguous with illite and which would not be present otherwise. The development of glauconite in sediments should be due to specific local conditions which permit the chemical evolution of an initial montmorillonite material to celadonite mica-like phase. In fact previous observations have consistently led to this conclusion as to the origin of glauconite in sediments and sedimentary rocks. 

Natural occurrences in hydrothermal areas show that the replacement of analcite + quartz by albite probably takes place near 150-180°C (Coombs, et al., 1959) at several hundred meters depth. The observed upper limit of analcite appears to be 100-125°C in deeply buried rocks in Japan 5Km depth). In other rocks for which no temperature data are available analcite can be found to coexist with sodium feldspar (High and Picard, 1965 Iijima and Utada, 1966 Iijima and Hay, 1968 Otalora, 196A Callegari and Jobstribitzer, 1964 Gulbrandsen and Cressman, 1960). Several authors have indicated that analcite replaces other zeolites in buried sequences of rocks (Moiola, 1970 Sheppard, 1970 Iijima and Hay, 1968 Iijima, 1970 Gude and Sheppard, 1967) but this is certainly not the rule since analcite is frequently associated with other zeolites as a primary mineral in soils sediments and sedimentary rocks (Hay, 1966). 

The absence of sepiolite and palygorskite from sediments and sedimentary rocks in other parts of the world is most likely due to a lack of attention on the part of researchers who have looked at clay mineral suites in the past. This can be explained in part by the similarity of the respective major low-angle peaks which can be confused with montmorillonite (12 8 sepiolite-one water layer montmorillonite) and illite (10.5 8 palygorskite-slightly "expanded" illite). A priori there is no reason why these minerals should be particular to French sedimentary rocks except that workers from this country have been particularly alert to their presence. This opinion is reinforced by the now-frequent reports of sepiolite and, to a lesser extent, palygorskite in sea sediments of the Atlantic shelf and ridge, Mediterranean, Red Sea and Pacific deep sea (see JOIDES reports—National Science Foundation Publications). 

Two minerals frequently encountered in sediments and sedimentary rocks are not accounted for in the Figures 48a to c. These are glauconite and chlorite, the two major iron-bearing phyllosilicates in sediments and sedimentary rocks. Glauconite formation can be explained on the basis of... 

There are standard terms applied to sediments and sedimentary rocks that can be used with coal minerals. Those minerals which were trans-... 

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