Clays and Clay Minerals, Vol. 55, No. 3, 253–259, 2007.
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Authors
Balan, Etienne
Fritsch, Emmanuel
Allard, Thierry
Calas, Georges
Issue Date
2007
Type
Article
Language
Keywords
Periodicals , Geology , Disorder , EPR , Infrared , Kaolinite , Laterite
Alternative Title
Inheritance Vs. Neoformation Of Kaolinite During Lateritic Soil Formation: A Case Study In The Middle Amazon Basin
Abstract
The tropical weathering of sedimentary kaolin deposits from the plateaux surrounding Manaus (Alter do Chao formation, Amazon basin, Brazil) leads to the in situ formation of thick kaolinitic soils. The structural changes of kaolinite have been investigated quantitatively by infrared spectroscopy and electron paramagnetic resonance. Both techniques consistently show that each sample contains two types of kaolinite in various proportions. The progressive decrease in kaolinite order from the bottom to the top of the profile results from the gradual replacement of an old population of well-ordered kaolinite, typical of the underlying sedimentary kaolin, by a more recent generation of poorly ordered soil kaolinite. The vertical pattern of kaolinite replacement differs from that of the transformation of Fe oxides and oxyhydroxides previously observed in the same profile. The inherited fraction of well-ordered kaolinite ranges from 60% at a depth of 9 m to 30% in the upper levels of the soil. The persistence of sedimentary kaolinite in the upper horizons suggests that the rate of kaolinite transformation is relatively slow at the time scale of lateritic soil formation. Kaolinite inheritance unlocks the lateritic record of past weathering conditions.
Description
Clays and Clay Minerals, Vol. 55, No. 3, 253–259, 2007. Inheritance Vs. Neoformation Of Kaolinite During Lateritic Soil Formation: A Case Study In The Middle Amazon Basin. Etienne Balan; Emmanuel Fritsch; Thierry Allard; Georges Calas. DOI: 10.1346/CCMN.2007.0550303. Copyright © 2007, The Clay Minerals Society
Citation
Clays and Clay Minerals, Vol. 55, No. 3, 253–259, 2007.
Publisher
The Clay Minerals Society
License
Copyright © 2006-2018, The Clay Minerals Society