0000000000602844

AUTHOR

Jean-louis Dumont

showing 2 related works from this author

A biogeochemical model for chalk alteration by fungi in semiarid environments

1996

Fungal filaments are the most abundant organic features in weathered profiles developed on chalky limestone ("platy calcrete"). Their activity affects the mineral dynamics of the pore/carbonate microsystem. A theoretical biogeochemical model is proposed to describe the Ca-oxalate-carbonate cycle related to fungal activity in dry environments.

CalciteGeochemistryMineralogyGeochemical cyclechemistry.chemical_compoundCalcium carbonatechemistryEnvironmental ChemistryCarbonate rockCarbonateSedimentary rockEcosystemGeologyEarth-Surface ProcessesWater Science and TechnologyBiomineralizationBiogeochemistry
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Spherulites in Calcrete Laminar Crusts: Biogenic CACO3 Precipitation as a Major Contributor to Crust Formation

1995

ABSTRACT Spherulites (calcitic fibro-radial spherulitic polycrystals) are a major component of calcite layers in Quaternary calcrete laminar crusts. To explain the formation of spherulites, petrographic and chemical studies were performed on Pleistocene calcrete laminar crusts, Holocene biological crusts, and laboratory (in vitro) cultures of cyanobacterial strains. Spherulites were found to be formed of acicular and radiating crystals, either smooth and regular-edged, or twisted and irregular-edged. Spherulites were composed of low-Mg calcite, the concentration of Mg in the spherulites increasing from nucleus to periphery. The shape and chemistry of the in vitro spherulites and laminar cru…

CalciteAcicularchemistry.chemical_compoundSpherulitechemistryMicriteSubaerialMineralogyCarbonateGeologyCrustGeologyBiomineralizationSEPM Journal of Sedimentary Research
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