Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The availability of multispectral data from the satellite-borne ASTER (Advanced Space borne
Thermal Emission Reflection Radiometer) sensor with 14 spectral bands, launched on 18
December 1999, ushers in a new dimension in large-scale mineral exploration. The ASTER
bands are strategically positioned to map distinctive absorptive features for mapping
alteration mineralogy, which has increased the potential to map hydrothermal alteration zones
as compared to the conventional Landsat TM satellite and aerial photographs.
This research tests the ability of ASTER to map hydrothermal alteration zones by applying
various image enhancement techniques and comparing them. The study area is the Haib
copper prospect in Namibia. The Crosta technique, standard colour composites, spectral band
ratioing, the software defoliant technique, log residuals and spectral linear unmixing were
applied and compared against results from the previous detailed geophysical and geochemical
exploration. The results from all the techniques corresponded with published geological maps
from previous work and indicated ASTER's ability to detect alteration zonations.
Comparison of the methods applied showed that choice of technique is usually dependent of
the level of detail which one seeks to achieve. Standard colour composite and log residuals
are more useful for a generalized overview of the alteration mineralogy, whilst uniquely
defining mineral end members is achieved by application of the Crosta technique, ratioing and
spectral linear unmixing. Application of the software defoliant techniques involved ratioing
results, which are affected by spectral interferences from other minerals.
The presence of a highly fractured system has been established by application of Sobel
filtering. A spatial association of the extracted fracture system with alteration areas suggest
mineralization at the Haib is fracture controlled. The results support the presence of argillicphyllic
and prophylitic alteration zones on a regional scale, a scenario which can be equated
to the Lowell-Guilbert model. The potassic-phyllic zone boundary could not be spectrally
detected which also supports previous studies which suggest the potassic zone is nondefinitive
and is over-printed by the phyllic zone. The results demonstrate that ASTER is an
effective tool to map hydrothermal alteration systems in arid areas. / AFRIKAANSE OPSOMMING: Multispektrale data van die ASTER (' Advanced Space Borne Thermal Emmission Reflection
Radiometer') sensors bestaande uit 14 spektrale bande, afkomstig van 'n satelliet gelanseer op
18 Desember 1999 lui 'n nuwe era in vir grootskaalse minerale eksplorasie. Die ASTER
bande is strategies sodanig op die spektrum geposisioneer om onderskeidende absorberende
verskynsels van veranderde mineralisasie te identifiseer. Hierdie data het die potensiaal
verhoog om hidrotermale veranderingstelsels meer suksesvol te karteer as met konvensionele
Landsat TM beelde en lugfotos.
Hierdie navorsing toets die vermoeëns van ASTER om hidrotermale veranderingstelsels te
karteer deur 'n wye reeks beeldverrykings tegnieke toe te pas en te vergelyk. Die
studiegebied IS die Haib koperafsetting in Namibië. Die Crosta tegniek, standaard
kleursamestellings ('colour composites'), ratio-tegnieke, plantegroeistroping ('software
defoiliant'), log residuele ('log residual '), en spektrale lineêre ontmenging ('spectral linear
unmixing') is toegepas en die resultate met vorige gedetailleerde geofisiese en geo-chemiese
veldopnames te vergelyk.
Die verkreë resultate van al die verskillende tegnieke het grootliks met gepubliseerde
geologiese kaarte van die gebied ooreengestem en bevestig dat ASTER data geskik is om
sulke mineralogies veranderde gebiede te karteer.
Vergelykings tussen die tegnieke het getoon dat die keuse van tegniek bepaal word deur die
vlak en tipe detail wat verlang word. Standaard kleursamestellings en die log residuele
tegnieke lewer goeie resultate om veralgemeende oorsigte van mineralogies veranderde sones
te verskaf, terwyl die Crosta-, ratio- en spektrale lineêre ontmengingstegnieke meer suksesvol
is om spesifieke minerale te identifiseer. Die plantegroei stropingtegniek is nodig in gevalle
waar spektrale ratios deur plantegroeiresponse geaffekeer word.
Die aanwesigheid van 'n intensief gefraktuurde sisteem is bepaal deur 'n Sobel filter toe te
pas. Ruimtelike assosiasies tussen die voorkoms van die gefraktuurde sone met en die
minealogies gewysigde sones dui aan dat mineralogiese wysiging in die Haib gebied deur
frakturering beheer is. Die resultate steun die aanwesigheid van argillities-fillitiese enpropolities gewysigde sones op 'n streekskaal, 'n scenario wat deur die Lowell-Guilbertmodel
voorgehou word. Die grense van die kalium-fillitiese sone kon nie spektraal
waargeneem word nie. Dit steun ook vorige studies wat suggereer dat die kaliumsone nieafbakenbaar
is en waarskynlik deur die fillitiese sone oorlê word. Die resultate bevestig
onomwonde dat ASTER data benut kan word om hidrotermaal veranderde sones in semiariede
gebiede effektief te karteer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50462 |
| Date | 04 1900 |
| Creators | Mhangara, Paidamwoyo |
| Contributors | Zietsman, H. L., Scheepers, R., Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 104 pages : illusrations, maps |
| Rights | Stellenbosch University |
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