Eluvium


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eluvium

[ē′lü·vē·əm]
(geology)
Disintegrated rock material formed and accumulated in situ or moved by the wind alone.

Eluvium

 

loose deposits that occur when the original (parent) rock weathers at its place of origin. The eluvium comprises weathering crusts and soils.

A distinction is made between the orthoeluvium of crystalline (magmatic and metamorphic) rocks, the metaeluvium of consolidated sedimentary rocks, and the neoeluvium of young, unconsolidated deposits (in the last two cases, the parent rocks consist largely of redeposited and slightly altered products of weathering). The most characteristic type is orthoeluvium, which ranges in composition from pebbles and boulders in cold climates to clays in hot, humid climates. On the basis of degree of decomposition, a distinction is made between siallitic eluvium, in which the original aluminosilicates are preserved; acidic siallitic eluvium, which is composed chiefly of newly formed hydrous aluminosilicates of the group of clay minerals; and allitic, or ferralitic, eluvium, in which a significant share of the silicates have decomposed and are represented by free hydroxides of aluminum and iron.

E. V. SHANTSER

References in periodicals archive ?
Eluvium over the main mineralized vein system is often thin, but can be thicker over the main open-pit targets.
However, there may be gold-bearing eluvial cover within the many strong geochemical gold anomalies and, although the eluvium is likely to be thin in places, these are worth checking out as part of the first stage of exploration for the major deposits.
Landslide forms most frequently encountered in the Polish Carpathians are eluvium slippages and landslips.
These minerals came from the inner intermediate lithia zone and from the associated alluvium and eluvium (Kun, 1965).
Additional localities include Caraibas (= Mariano Dias) near the town of Rubilita; Valdete, near Coronel Murta, with pyrite and purple apatite; Lomoeiro, previously famous for topaz and other gem species, where a rose quartz crystal pocket was found in July 1989; Morro Redondo, formerly famous for gem tourmaline, where crowns of rose quartz crystals to 25 cm were found around 1990; Laranjeira, in a tourmaline-rich eluvium found in December 1989 about 2 km north-northeast of the Ademar pegamtite; and Girau in the upper Piaui Creek area, where a few tens of kilograms of fine rose quartz clusters and crowns with gem-grade green and blue tourmaline were found.