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doi: 10.1080/014311697218205pmid: N/A
Abstract The precious metal class of ore deposit is composed of several subtypes. Occurrences are dominated by systems of hydrothermal origin commonly classified by physical geologic features that relate conveniently to remote sensing. Variability between types of deposits is an important consideration in the selection, application, and interpretation of remote sensing data. This paper outlines and compares both the physical geologic features and the important remote sensing characteristics of the economically important sediment-hosted and volcanichosted types. The spectral and spatial resolution requirements of the significant deposit features - primary alteration, secondary alteration, host rocks, structure, zoning relationships, and vegetation - are reviewed. Exploration strategies and project scales, including reconnaissance, regional, district and deposit scales, influence spatial resolution requirements. Hyperspectral imagery and spatial resolutions of up to 3-4 m are required to satisfy some detection and mapping objectives at some precious metal projects.
doi: 10.1080/014311697218214pmid: N/A
Abstract Discovery of diamondiferous kimberlite in northwestern Canada, and occurrences of similar intrusions and alluvial diamonds elsewhere, suggest North America is fertile ground for economic primary diamond deposits. Using a Diamond Exploration Geoscientific Information System (DEGIS) to develop an exploration model, we identified four areas of permissive terrain in the northcentral United States: Wisconsin-Upper Peninsula of Michigan, southeastern Wyoming, North Dakota-Minnesota-Ontario, and northwestern Iowa. Permissive areas feature lithosphere that is > 1.6 billion years old and > 150 km thick; and prospective zones within this terrain contain point and linear features that are associated with kimberlite and lamproite emplacement.
doi: 10.1080/014311697218223pmid: N/A
Abstract The results of a comparative investigation of lineament mapping from stereoscopic Large Format Camera (LFC) photographs and from SIR-C L- and C-band Synthetic Aperture Radar (SAR) data are described. The lineament patterns are used to test a model developed by Koch (1993) of groundwater flow in the arid Red Sea Hills area of Sudan. Initial results show that the LFC imagery is most useful for mapping detailed fracture patterns while the combination of the L- and C-bands of the SIR-C Synthetic Aperture Radar is helpful in the location of major deep-seated fracture zones. The lineament patterns derived from LFC and SIR-C show strong N-S and E-W orientations, which correspond to the current tectonic configuration of the Red Sea rift system. The longer E-W trending features may be important from a regional hydro-geological point of view, whereas the shorter features are significant in that they interconnect the major faults.
Paradella, W. R.; Bignelli, P. A.; Veneziani, P.; Pietsch, R. W.; Toutin, T.
doi: 10.1080/014311697218232pmid: N/A
Abstract This research focuses on the integration of Synthetic Aperture Radar (SAR) (C-HH airborne, JERS-1, ERS-1) with Landsat TM and airborne gamma ray (total count, uranium, and thorium) data for geological mapping in Carajas Province, Brazil. The area is related to an Archean shear belt, with metasediments, metavolcanics, gneisses, and granulites. Anorogenic granites with Middle Proterozoic ages are scattered throughout the study area. The vegetation is typical of tropical upland rain forest. Radar and Landsat TM produce enhanced images closely related to geobotanical associations. Radar and gamma channels show the relationships between terrain morphology and bedrock radioactivity, good indicators of structures, lithological units, rock types, and hydrothermal metasomatism processes. The research emphasizes the practical importance of using SAR integrated products for geological mapping in the Amazon Region when airborne geophysical data are available.
Schetselaar, E. M.; Rencz, A. N.
doi: 10.1080/014311697218241pmid: N/A
Abstract The gamma-ray spectrometry responses from bedrock in Canadian Shield areas are substantially masked by overburden and vegetation. Proper interpretation of airborne gamma-ray spectrometry data is dependent on accounting for the interference provided by surface cover. In this paper, a method is tested to correct airborne gamma-ray spectrometry, acquired over the Canadian Shield of northeastern Alberta, for vegetation screening by estimating the proportions of bedrock and vegetation cover from Landsat TM data. TM pixel values, due to the patchy network of bedrock and vegetation, result from a spectral mixture of these ground cover classes. Linear unmixing was implemented to deconvolve TM bands in abundance images to estimate proportions of bedrock and vegetation for each pixel. The outcrop abundance image, representing spatial variation in area percentage of bedrock, is used in linear regression analysis to calibrate co-registered K, eTh, and eU gamma-ray spectrometry channels to 40 per cent bedrock endmember images.
doi: 10.1080/014311697218250pmid: N/A
Abstract AVIRIS, TIMS, and AIRSAR data were integrated to provide a better understanding of surface variations in Death Valley, California, U.S.A. Inversion models were used to obtain quantitative measures of surface mineralogy and morphology from the data. The data inversion results were integrated for an alluvial fan site showing that the fan morphology is affected by the mineralogy of the surface. A more accurate geologic map and the relative ages of the fan surfaces were determined. Integrating the inversion results for a portion of the salt flats showed morphological and mineralogical variations that were caused by surface washing and flooding.
doi: 10.1080/014311697218269pmid: N/A
Abstract Fe 3+ bearing minerals and poorly crystalline mineraloids can host pernicious trace metals released by mining activities. Such mineral phases are readily detectable in imaging spectrometer data such as is collected by NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS). Laboratory measured reflectance spectra of fluvial sediment samples gathered downstream from the Summitville mining district in southwest Colorado, U.S.A., have been compared with AVIRIS data collected over Summitville and the surrounding San Juan mountains. Spectra from the AVIRIS image cubes over Summitville match with the laboratory measured reflectance of several Fe 3+ bearing mineral phases including a ferrihydrite produced in an acid water environment.
Resmini, R. G.; Kappus, M. E.; Aldrich, W. S.; Harsanyi, J. C.; Anderson, M.
doi: 10.1080/014311697218278pmid: N/A
Abstract The areal distributions of the minerals alunite, kaolinite, and calcite in an approximately 1.8km 2 area of the Cuprite mining district, Nevada, have been mapped by applying constrained energy minimization (CEM) to remotely sensed data from the HYperspectral Digital Imagery Collection Experiment (HYDICE) sensor, a 210 channel, 0.4 mum to 2.5 mum airborne hyperspectral imaging spectrometer. The image data analysed here have ground sample distances of approximately 3 m. CEM is a powerful and rapid technique for mineral mapping which requires only the spectrum of the mineral to be mapped and no prior knowledge of background constituents. Other spectral image processing techniques applied to the data produce results essentially identical to those of CEM and which agree with the mapping of Ashley and Abrams (1980).
Ninomiya, Y.; Matsunaga, T.; Yamaguchi, Y.; Ogawa, K.; Rokugawa, S.; Uchida, K.; Muraoka, H.; Kaku, M.
doi: 10.1080/014311697218287pmid: N/A
Abstract In order to obtain ground truth data for multispectral thermal infrared sensors such as TIMS and ASTER, in situ spectral emissivity measurements were made during field surveys. These spectral emissivity measurements and laboratory spectral reflectance measurements of field samples were compared to emissivity spectra extracted from TIMS data at the surveyed points. The results indicate that emissivity spectra derived from the TIMS data agree well in shape with the spectra measured in situ or in the laboratory.
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