Minerals, aeolian transport

The production of illite from chemical weathering occurs at all latitudes. It dominates the clay mineral assemblage in the North Atlantic and North Pacific Ocean, particularly at 40° reflecting aeolian transport by the westerlies (Figure 14.11). In the southern hemisphere, the input of illite by the westerlies is diluted by a large input of authigenic montmorillonite in the South Pacific and Indian Oceans and in the South Atlantic by a large input of kaolinite. 

The abyssal clays are composed primarily of clay-sized clay minerals, quartz, and feldspar transported to the siuface ocean by aeolian transport. Since the winds that pick up these terrigenous particles travel in latitudinal bands (i.e., the Trades, Westerlies, and Polar Easterlies), the clays can be transported out over the ocean. When the winds weaken, the particles fell to the sea siufece and eventually settle to the seafloor. Since the particles are small, they can take thousands of years to reach the seafloor. A minor fraction of the abyssal clays are of riverine origin, carried seaward by geostrophic currents. Despite slow sedimentation rates (millimeters per thousand years), clay minerals, feldspar, and quartz are the dominant particles composing the surface sediments of the abyssal plains that lie below the CCD. Since a sediment must contain at least 70% by mass lithogenous particles to be classified as an abyssal clay, lithogenous particles can still be the major particle type in a biogenous ooze. 

In the South Pacific, the CCD is deep enough to permit the preservation of calcareous oozes except in the center of the basin, which as a result is covered by abyssal clays. The relatively rapid supply of hydrogenous sediments prevents the accumulation of calcareous oozes on the East Pacific Rise. In the North Pacific, abyssal clays dominate as this is the location where the CCD is shallowest. Aeolian transport is the source of the clay minerals that make up these deposits. 

Variations both or grain size and mineral density result in separation of minerals and rock fragments during aqueous and aeolian transport of sedimentary material. Such transport may affect lanthanide abundance patterns in the resulting sedimentary rock because of the widely variable patterns in the constituent minerals. The two most important effects are... 

These deposits are formed in the natural process of weathering, transportation, and concentration at the site of heavy minerals originating from some primary source rock. Commercially, beach placers are the most important along with alluvial streams aeolian deposits are insignificant. 

Merrill, J., E. Arnold, M. Leinen, and C. Weaver, Mineralogy of Aeolian Dust Reaching the North Pacific Ocean. 2. Relationship of Mineral Assemblages to Atmospheric Transport Patterns, J. Geophys. Res., 99, 21025-21032 (1994). 

Since the age of agriculture is estimated to be about 10 ky, it follows that any discussion of natural inputs of minerals to agricultural soils from an external source will be limited to comparatively recent phenomena. Thus, rocks and minerals that have been transported in the distant geologic past by ice, wind, and water to form glacial, aeolian, alluvial, lacustrine, and marine deposits are outside the scope of this chapter, since these are generally parent materials from which modem soils were formed. Dense populations usually developed where the soils had been enriched by recent volcanic activity or by young alluvial deposits. 

McMuny PH, Woo KS, Weber R, Chen DR, Pui DYH (2000) Size distributions of 3-10 mu atmospheric particles Implications for nucleation mechanisms. Philos Trans Roy Soc Lond A 358 2625-2642 Merrill J, Arnold E, Leinen M, Weaver C (1994) Mineralogy of aeolian dust reaching the north pacific-ocean. 2. Relationship of mineral assemblages to atmospheric transport patterns. J Geophys Res 99 21025-21032... 

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