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Accueil du site → Doctorat → Canada → Influence of chromite mineralization on vegetation : a geobotanical investigation in West Pokot District, Kenya

University of Waterloo (1993)

Influence of chromite mineralization on vegetation : a geobotanical investigation in West Pokot District, Kenya

Odhiambo, Beneah Daniel Onyango

Titre : Influence of chromite mineralization on vegetation : a geobotanical investigation in West Pokot District, Kenya

Auteur : Odhiambo, Beneah Daniel Onyango

Université de soutenance : University of Waterloo

Grade : Doctor of Philosophy (PhD) 1993

Résumé
In order to explore for new sources of mineral deposits, especially in vegetated areas, several studies have demonstrated the effectiveness of geobotanical methods. The technique has been used since ancient times. This research is designed to investigate the influence of chromite mineralization on the associated vegetation. The objectives of the study are : to identify chromite indicator species around the mineralization ; to determine the spectral characteristics of the geobotanical anomaly as it appears on satellite imagery ; to determine whether known sites of the chromium and nickel deposits can be identified by an analysis of nickel, cobalt, manganese, and chromium (the chromite pathfinder elements) in the geobotanical samples ; and to determine how the spectral reflectance of the vegetation is influenced by these elements. Identification of the geobotanical units around the mineralization was undertaken using aerial photographs at scales of 1:50,000 and 1:12,500 ; and by analysis of a landsat thematic mapper image. Trace element analysis of the pathfinder elements in vegetation samples involved the collection of plant samples from pre-selected sample locations around the chromite mineralization. The samples were ashed at 500$/sp/circ$c in a muffle furnace, digested in anal sulfuric acid, and analyzed for the elements using a perkin-elmer atomic absorption spectrophotometer. In the field, the spectral reflectance of the same plants were measured using an se590 portable spectroradiometer. In the laboratory, independent spectral reflectance parameters at the red edge of the vegetation spectra were derived by analysis of all the plant spectra using the floating r$/sb[/rm o]$ spectral analysis technique and the fixed r$/sb[/rm o]$ technique. By simple correlation analysis, the degree of association between the independent spectral parameters and the element concentrations in the vegetation is established. The study concludes that a distinct geobotanical unit is associated with the chromite mineralization. These units are unique on remote sensing images. Chromite indicator (tolerants) species were identified, and include Faurea saligna, Leucas tomentosa, Protea kilimandischarica, Maerua subcordata, and Satureja abyssinica. These plants only occur in the vicinity of the mineral deposits. They contain anomalous concentrations of the pathfinder elements in their ashes, which locates the known sites of the chromium and nickel deposits. The effect of these elements on the vegetation spectra is to shift the red edge towards shorter wavelength, thereby causing a blue shift effect in most of the species. Correlation analyses of these elements and the independent spectral parameters derived from the indicator species are particularly strong, indicating the potential value of these species in spectral geobotanical studies for mineral exploration

Sujets : West Pokot District ; Mineralogy ; Scientific imaging ; Remote sensing ; Flowers and plants ; Environmental impact ;

Présentation (BAC)

Page publiée le 14 janvier 2017, mise à jour le 7 septembre 2019