Shales mineralogical composition

Table 9.9. Mineralogical composition of river suspended load and shales (wt.%). (After Wollast and Mackenzie, 1983.)...

The mineralogy of the suspended matter carried by rivers is not well documented. There are numerous analyses either of the clay fraction or of sands carried by rivers, but only a few total quantitative analyses are reported in the literature. As examples, the average mineralogical composition of two large river systems, the Amazon and the Mississippi, are presented in Table 9.9. This table also includes the mean mineralogical composition of shales for comparison with river suspended sediments. The overall average of 300 samples of shales analyzed by Shaw and Weaver (1965) is 30.8% quartz, 4.5% feldspar, 60.9% clay minerals, and... 

Mineralogic Composition. The subject shales are designated silty shales due to their high quartz content. The mineralogic composition of these shales has been studied (14-18) and is summarized in Table III. Illite (2M), muscovite and/or illite/smec-tite are the predominant clays found in these shales. 

Table III. Modal Mineralogic Composition of Devonian Oil Shales.

Eastern U.S. oil shales are also sedimentary rocks. However, in contrast to Green River shales, the mineral constituents of Eastern U.S. shales are primarily silicates, with only about 1 wt% carbonate minerals. The bulk mineralogical composition of the Kentucky shale consisted primarily of quartz, illite and kaoli-nite, with some chlorite and pyrite. This is consistent with elemental analysis data which found the major mineral constituents to be Si, Al, Fe, and K. The elemental Ca concentration was less than 100 ppm. 

Triassic sediments are deposited only in the eastern and northern parts of the Sahara, in the Triassic Province. Triassic sandstones are mainly a combination of deltaic to prodeltaic facies represented by upper deltaic fluvial system deposits, lower distributary channel rivers, mouth bars, beach sands and tidal flat and prodeltaic shales. Typical marine Triassic shales are restricted in extent in the study area. Triassic Lower, Middle and Upper sandstones are stratigraphically separated by shale intervals, but occasionally also by carbonates or volcanic interbeds. They are often medium grained, and range from friable to cemented with clay mineral, carbonate, anhydrite and siliceous cement. Porosity ranges from 12 to 22%. With respect to mineralogical composition and maturity, Triassic sandstones are mature sublitharenite (Lower Triassic), sublitharenite to submature subarkose (Middle Triassic) and submature subarkose (Upper Triassic). 

Schultz, L. G., 1964. Quantitative Interpretation of Mineralogical Composition from X-ray and Chemical Data for the Pierre Shale. U. S. Geol. Surv. Prof Paper 391-C, 31 pp. 

The clay mineral component used for cement manufacture will generally be a soft or loose-textured material clays, silts, or sands with highcontentof clay minerals. These materials are classified according to particle size distribution rather than mineralogical composition (Table 1). Rock-type clay materials may occur as clay slate, shale and (to some extent) crystalline slates. Subject to chemical suitability, such rocks as granites, gneisses, basalts and basaltic tufas or pozzolanas may also serve as clay mineral components. 

Shaw DB, Weaver CE (1965) The mineralogical composition of shales. J Sediment Pet 35 213-222... 

GER analysis incorporating element combinations designed to reflect the main minerals of the unaltered, altered and weathered rocks reveals clear separation of these different compositions and explains the mineralogical changes during alteration (Fig. 4). Unaltered shale compositions cluster toward the muscovite/ankerite node of the... 

The major element content and mineralogy of air-borne particles reflect closely those of continental soils and shales, although atmospheric particulates also include materials of oceanic origin (Delaney et al., 1967), and show considerable enrichments in some trace metals (Buat-Menard and Chesselet, 1979). The average composition of shales and soils (Table 9.8) was chosen to represent the properties of dust transported from the continents to the ocean. Fluxes of elements in atmospheric transport to the ocean are given in Table 9.14. 

Suitable shales and clays typically have bulk compositions in the region of 55-60% Si02, 15-25% AI2O3 and 5-10% Fe203, with smaller amounts of MgO, alkalis, H2O and other components. Mineralogically, their main constituents are clay minerals, finely divided quartz and, sometimes, iron... 

Table 15-1 Ranges of Chemical Composition and Mineralogical Phases Present in Acid Brick (Red Shale and Fireclay)...

In petrology one takes data from the rock - such as chemical composition, mineralogy, and grain relationships - and tries to establish how the rock evolved. Of the tools used in petrology, thermodynamics and chemical reaction relations are the two most useful (12-15). In the case of spent shale, temperatures of 500°C... 

If it is assumed that the composition of the roof shales is the closest representation of parent mineralogy available, the clay sediments entering the depositional basin included considerable amounts of illite/mica, moderate amounts of kaolinite, relatively small amounts of expandable clays, and some chlorite. Whereas some modifications may have taken place since deposition of the clays in the roof shales, they probably have been affected less by the organic acids than the clays in the underclays, coals or partings. The presence of chlorite in the roof rocks suggests that acidic... 

Mineralogy and Chemical Composition of the Pierre Shale in South Dakota and Adjacent Parts of North Dakota, Nebraska, Wyoming, and Montana, U. S. Geol. Survey Prof. Paper (1960) 400-B, B447-B452. 

---