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Alteration Mapping

Alteration Mapping Alteration Mapping 2
NPA’s spectral mapping from satellite imagery is used to outline and differentiate lithologies and mineral suites. This enables explorationists to map alteration halos associated with the circulation of hydrothermal fluids that maybe related to mineral deposits (VMS, IOCG, epithermal etc). Two main satellite platforms are used routinely: Landsat ETM and ASTER.

Landsat ETM is ideal for broad mapping and discrimination of lithological and mineral suites as it covers a wide swath of the electromagnetic spectrum. Mapping shear-zone hosted Au deposits in Central Asia is illustrated in the image top right, which outlines the main mapped shear zones. The image below, shows clay alteration patterns. Landsat data covers a broad swath of the electromagnetic spectrum.

However, ASTER data with its narrower band coverage of the spectrum, has greater mineral discrimination and is therefore ideal for the further mapping and discrimination of mineral suites. The ASTER image extracts (approximately 5km across, right) show distinct mineral alteration halos due to the circulation of hydrothermal fluids. Such clay alteration patterns are associated with epithermal gold deposits in this region.

Alteration Mapping 3

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