Saprolite

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Saprolite profile about 15 m high in weathered paragneiss and light quartzites. Ampanobe, 8 km southeast of Antananarivo , Madagascar.

Saprolite ( ancient Greek σαπρός sapros , German 'rotten' and λίθος líthos 'stone'), also saprolite, is the name for an originally silicate rock that has undergone deep chemical weathering under humid conditions (e.g. in tropical regions) . It is usually soft or crumbly and shows the structure of the parent rock as autochthonous (not rearranged) weathering formation.

In addition to resistant minerals from the parent rock , especially quartz , saprolites contain high proportions of kaolinite , which has formed through the chemical weathering of primary minerals, especially feldspar . The compounds discharged as solution load in the course of weathering can be precipitated again elsewhere. Even more intensive weathering, which goes beyond the saprolite stage, leads to a depletion of quartz and thus to the formation of a laterite horizon above the saprolite.

Saprolite should not be confused with sapropelite , which is formed when digested sludge ( sapropel ), a dark, carbon-rich sediment deposited in a reducing chemical environment , is lithified .

literature

  • Hans Murawski, Wilhelm Meyer: Geological dictionary . 10th, revised and expanded edition, Enke Verlag, Stuttgart 1998, ISBN 3-432-84100-0 .

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