Weathering mechanical

Trace elements are discharged into the ocean in particulate and dissolved form as a component of river runoff and groundwater seeps. They are introduced into these waters during the chemical and mechanical weathering of crustal rocks. Thus, the chemical composition of river water is dependent on the composition of the rocks in the... 

Lee M. R., Hodson M. E., and Parsons 1. (1998) The role of intragranular microtextures and microstructures in chemical and mechanical weathering direct comparisons of experimentally and naturally weathered alkali feldspars. Geochim. Cosmochim. Acta 62, 2771-2788. 

The processes of mechanical weathering and dissolution in recycling systems lead to the diminution of grain size of all mineralogical constituents, as well as to progressively mono-mineralic quartz-rich sediments (Cox and Lowe, 1995). Sedimentary recycling is particularly effective in redistributing the trace elements, a topic discussed in the next section. 

The rate of chemical weathering is usually increased if the rate of physical or mechanical weathering is increased. Physical weathering (the breakdown of rock due to physical proc-cesses), which is most active in mountainous areas, can repeatedly expose fresh mineral surfaces to chemical weathering. 

Table 3 Incongruent release of isotopes from strongly mechanically weathered continental rocks ...

Nickel, the 24th most abundant element in the earth s crust, is found in combination with other elements in soils and sediments. Nickel is present in detectable amounts in most types of rocks, and it may be mobilized in the surface environment during the chemical and mechanical weathering of rock to form soil. 

Finely ground minerals such as talc (10-20 wt%) and mica, or aluminum powder (1 -5 wt%) are usually incorporated into the asphalt to improve its film properties, in particular its mechanical, weather, and aging resistance. Antisettling agents such as montmorillonite-bentone (0.5-1.5 wt%) also have to be used. 

Waterborne bitumens may be anionic, cationic, or rarely nonionic emulsions, and are produced with the aid of emulsifiers and, if necessary, stabilizers conventionally used in the paint industry. The properties of bitumen paint (solutions and emulsions) (e.g., stability mechanical, weather, water, and chemical resistance corrosion protection properties) can be substantially improved by incorporating extenders. Suitable extenders include ground slate, ground limestone, chalk, talc, and mica (25 45 wt%, depending on extender type and required properties). The use of extenders... 

Briefly, sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks (1) clastic sedimentary rocks, such as breccia, conglomerate, sandstone, and shale, which are formed from mechanical weathering debris, (2) chemical sedimentary rocks, such as rock salt and some limestone rocks, which form when dissolved materials precipitate from solution, and (3) organic sedimentary rocks, such as coal and some limestone rocks, which form from the accumulation of plant or animal debris. 

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