Rock, composition sedimentary

In order to determine the source composition of sediments using trace elements, it is necessary to ascertain that the element is immobile under conditions of diagenesis and weathering (Spalletti 2008). Several ratios and plots may be used to define the source rocks. The felsic source rock compositions are found in the Co/Th vs. La/Sc diagram (Fig. 3 Table 1). Other trace element characteristics of sedimentary rocks also place some constrains on the nature of the source rock. Floyd Leveridge (1987) used a La/Sc vs. Hf plot to discriminate between different source compositions. In this plot, most data fall in the felsic source to mixed felsic/basic source field (Fig. 4 Table 1). 

The isotope composition of the precursor rock - either sedimentary or magmatic - is usually difficult to estimate. Only in relatively dry nonvolatile-bearing precursor rocks do retain metamorphic rocks their original composition. 

This chapter will examine the ways in which major element data axe used in geochemistry. The discussion will be restricted to the ten elements traditionally listed as oxides in a major element chemical analysis — Si, Ti, Al, Fe, Mn, Mg, Ca, Na, K and P. Geochemists make use of major element data in three principal ways — in rock classification, in the construction of variation diagrams and as a means of comparison with experimentally determined rock compositions, whose conditions of formation are known. Each of these uses will be discussed in a separate section of this chapter. In addition, major elements are used, often together with trace elements, in the identification of the original tectonic setting of igneous and some sedimentary rocks. This topic will be discussed in Chapter 5. 

Average trace element composition Cppm) of igneous rocks [79], sedimentary rocks [77] and soils [77]... 

In igneous rocks, density increases from felsic (acid) to mafic (basic) types. Each rock type shows a range of density values. In comparison with most sedimentary rocks, this range is relatively small and is mainly result of a variation of the particular rock composition and a very small influence of pore or fracture volume. 

Because igneous (and metamorphic) rocks and sedimentary rocks are distinctly different with respect to mineral composition and types of pores and fractures, the two groups are discussed separately. 

To gain an understanding of the composition of the reservoir rock, inter-reservoir seals and the reservoir pore system it is desirable to obtain an undisturbed and continuous reservoir core sample. Cores are also used to establish physical rock properties by direct measurements in a laboratory. They allow description of the depositional environment, sedimentary features and the diagenetic history of the sequence. 

Limestone. This is a sedimentary rock that is formed by the accumulation of organic marine life remains (shells or coral). Its main component is calcium carbonate. Cement rock. This is a sedimentary rock that has a similar composition as the industrially produced cement. 

Composites are combinations of two or more materials with the properties shown by individual components. They are made to perform as a single material. Nature made the first composite in living things. Wood is a composite of cellulose fibers held together with a matrix of lignin. Most sedimentary rocks are composites of particles bonded together by... 

During the last two decades, many experimental studies on the seawater-rock interaction at elevated temperatures (100-400°C) have been conducted. Particularly, detailed seawater-basalt interaction experiments have been done. Several experimental studies on seawater-rhyolite interaction and seawater-sedimentary rock interaction are also available (Bischoff et al., 1981). Examples of chemical compositions of modified seawater experimentally interacted with various kinds of rocks are shown in Table 1.9. 

Thick sedimentary pile from middle Miocene to late Pliocene is exposed in the Oga Peninsula, northern Honshu, Japan (Fig. 1.153). Age of the sedimentary rocks has been determined by microfossil data. Thus, the sedimentary rocks in the Oga Peninsula where type localities of Miocene sedimentary rocks in northern Japan are well exposed have been studied to elucidate the paleoenvironmental change of the Japan Sea (Watanabe et al., 1994a,b). Kimura (1998) obtained geochemical features of these rocks (isotopic and chemical compositions) and found that regional tectonics (uplift of Himalayan and Tibetan region) affect paleo-oceanic environment (oxidation-reduction condition, biogenic productivity). However, in their studies, no detailed discussions on the causes for the intensity and periodicity of hydrothermal activity, and temporal relationship between hydrothermal activity, volcanism and tectonics in the Japan Sea area were discussed. They considered only the time range from ca. 14 Ma to ca. 5 Ma. 

Average analytical data on the sedimentary rocks are compared with NASC (North American Shale Composite Grometet al., 1984) in Fig. 1.154. 

Cement rock Sedimentary rock with composition similar to industrial cement... 

Gypsum, one of the more common sedimentary rocks in the earth s crust, occurs in varieties that differ from each other in texture rather than in composition. In most of its varieties gypsum is very soft and can be scratched even with a fingernail. One massive and fine-grained variety of gypsum, known as alabaster, much appreciated for designing delicate decorative objects, has been used particularly for carving and ornamentation. 

The isotopic composition of carbon in carbonaceous organic material (kerogen) from ancient sedimentary rocks gives information on whether photosynthetic organisms were present during rock formation or not. It can also provide information on biological activities if cellular structures had already been destroyed. Sulphur can be used in a similar way (Schopf, 1999). 

The REE data suggest that these carbonate rocks cannot be carbonatites of mantle origin. However, it is noteworthy that the range of compositional variations of typical carbonatite family rocks overlaps with those of sedimentary, metamorphic, and endogenic carbonate rocks (Samoilov 1991). Samoilov (1991) explained that one reason for the significant compositional variations of the carbonatites were due to different types of the associated alkaline rocks under different geologic-tectonic settings. 

---