Sedimentary rocks, clastic

The formation of a clastic sedimentary rock involves the following processes  

In the deposition process, when the velocity of the transporting medium becomes too low to transport sediment, the sediment falls out and becomes deposited. 

Some of fhe more common fypes of clastic sedimentary rocks are described below  

Sandstone—Sandstones, composed essentially of cemented sand, comprise about 30% of all sedimentary rocks. The most abundant mineral in sandstone is quartz, along with lesser amounts of calcite, gypsum, and various iron compounds. Sandstone is used as an abrasive (for sandpaper) and as a building stone. 

Oil shales range widely in organic content and oil yield. Commercial grades of oil shale, as determined by their yield of shale oil, range from about 100 to 200 liters per metric ton (L/t) of rock. The U.S. Geological Survey has used a lower limit of about 40 L/t for classification of federal oil shale lands. Others have suggested a limit as low as 25 L/t. 

Another application of stable isotopes in clastic rocks is the analysis of weathering profiles, which can potentially provide insight into the continental climate during 

Isotopic composition of authigenic minerals in Haitian weathering profiies  

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The most stable minerals are often physically eroded before they have a chance to chemically decompose. Minerals that decompose contribute to the dissolved load in rivers, and their solid chemical-weathering products contribute to the secondary minerals in the solid load. The secondary minerals and the more stable primary minerals are the most important constituents of clastic sedimentary rocks. Consequently, the secondary minerals of one cycle of erosion are... 

Clastic sediments are reservoirs of information about weathering processes, but are sufficiently complex that no study has yet to realize their potential. Despite a number of initial reports of relatively isotopically heavy samples, the majority of data for clastic sedimentary rocks have an average 8 Li 0, equivalent to the estimated average isotopic composition of the continental crust. 

Trenches excavated across the veins are typically flooded by surface water however, three partially flooded trenches have exposed bedrock. From small (< 5m ) outcrops exposed in three of the trenches, it is apparent that the average grain size of the clastic sedimentary rocks and the abundance of coarse-grained detritus, increases from NE to SW away from the buried Caradocian shale, with arkosic sandstone most abundant in the SW near the Christopher vein. An extensive array of 98 drill holes provides excellent downhole, 3-D control on our understanding of the geology. 

The clastic sedimentary rocks are the most common forms. They arise when an original rock wears down due to mechanical erosion and the weathering products are transported by gravity, mudflows, running water, glaciers and wind and eventually sorted by size deposited in various settings. 

If substantial arsenic is present in a sandstone or conglomerate, it may occur in hematite or other iron (oxy)(hydr)oxide cements or coatings on mineral grains. Arsenic may also be enriched in sandstones, conglomerates, and other clastic sedimentary rocks if hydrothermal or other secondary sulfide minerals are present (e.g. St. Peter Sandstone, (Gotkowitz et al., 2001) arsenian pyrite cement in the Marshall Sandstone of the Michigan Basin, USA, (Kolker et al., 2000 Szramek, Walter and McCall, 2004)). Sections of the St. Peter Sandstone in eastern Wisconsin, USA, are enriched in sulfide minerals and contain about 500 mg kg-1 of arsenic. In contrast, unmineralized portions typically have <10 mg kg-1 (Gotkowitz et al., 2001). If present in sedimentary rocks, hydrothermal sulfide deposits often tend to concentrate in veins and faults more than the rock matrices. 

Clastic sedimentary rock A sedimentary rock largely consisting of cemented particles from preexisting rocks rather than chemical precipitates or materials excreted by organisms (e.g. coral reef deposits). Sandstones are examples of clastic sedimentary rocks. 

Conglomerate A clastic sedimentary rock mostly composed of rounded or subrounded particles that are >2 mm in diameter. 

Mudstone A nonfissile clastic sedimentary rock largely or entirely consisting of silt- and clay-sized particles (less than 0.063 mm in diameter) (compare with claystone, shale, and siltstone). 

Sandstone A clastic sedimentary rock primarily consisting of sand-sized grains (0.063-2 mm in diameter). Usually, but not always, the major mineral in sandstone is quartz. 

Sedimentary rock A rock that formed from the natural cementing of sediments during burial, compaction, and interactions with groundwater (clastic sedimentary rocks) or that resulted from the burial and diagenesis of materials excreted from organisms or salts that precipitated from surface water. 

Shale A very fine-grained, laminar, and fissile clastic sedimentary rock consisting of 67 % or more clay-sized (<4 pm in diameter) particles (compare with claystone, mudstone, and siltstone). 

Besshi deposits comprise thin sheets of massive, well-layered pyrrhotite - - chalcopyrite + sphalerite - - pyrite with minor galena and cobalt minerals interlayered with terrigenous clastic sedimentary rocks and calc-alkaline... 

Clastic sedimentary rocks cap the stratigraphy in most greenstone belts and have been referred to as the Shamvaian Supergroup (Fig. 5). The central part of the Midlands greenstone belt is occupied by a narrow (1-10 km) NNE-trending fault-bounded unit of clastic sedimentary rocks, interbedded with felsic volcanic rocks (Fig. 3e, Bliss 1970 Harrison 1970 Wilson 1979). A similar unit is found in the Harare belt (Fig. 3g). Both... 

Curtis, C.D. (1990) Aspects of climatic influence on the clay mineralogy and geochemistry of soils, lateosols and clastic sedimentary rocks. J. Geol. Soc., London, 147, 351-357. 

The similarity of REE patterns for the widely scattered loess deposits to those of shales from widely separated continental areas indicates that loess also provides the same information on the composition of the upper crust as that provided by clastic sediments. There is little evidence these sediments have been affected by significant weathering. This demonstrates that upper crustal provenance is the prime control on REE patterns of clastic sedimentary rocks rather than the effects of sedimentary processes. 

Frey M (1987) Very low-grade metamorphism of clastic sedimentary rocks. In Low Temperatrrre Metamorphism. M Frey (ed) Blackie and Son Ltd, Glasgow Frey M, Robinson D (1999) Low-Grade Metamorphism. Blackwell Science, Oxford Grabb SMB, Peacor DR, Jiang W-T (1991) Transmission electron microscope observations of ilhte polytypism. Clays Clay Minerals 39 540-550... 

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