Exploration advances: New developments in spectral remote sensing in the Mount Isa region, Australia

Category GIS & Remote sensing
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Thomas, Matilda۱; Laukamp, Carsten۱; Cudahy, Thomas۲; Jones, Mal۳
Holding Date 11 October 2008

Advanced spectral remote sensing can be a valuable tool for explorers in both green-fields and brown-fields exploration. Using highly-calibrated spectral data and processing techniques, new perspectives can be gained in mapping and characterising materials at the surface. Surface expression of underlying materials, such as ore-deposits, can also be mapped and characterised using these methods. Mineral maps and products made from spectral datasets that can be integrated with other datasets provide a ready-to-use tool that aids explorers in identifying and mapping unconsolidated regolith material and underlying bedrock.
In the Mount Isa region, bedrock signatures have been discovered in areas recorded as "extensive cover sediments" where no bedrock had been previously mapped. This means that in addition to being able to make mineral classifications that characterise transported materials, it is also possible to find new windows of basement geology in areas previously mapped as cover. This has useful applications for mapping geomorphic processes in that it helps to understand mineral dispersion pathways and target surface sampling for mineral exploration.
The Predictive Mineral Discovery Cooperative Research Centre (pmd*CRC) developed a comprehensive spectral geology study in conjunction with the Queensland State Government’s "Smart Exploration Program" as part of a joint venture to collect and process new hyperspectral data in Queensland, and to calibrate an existing Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite mosaic, of some ~150 ASTER scenes.
This work demonstrated that a considerable amount of geochemical information about hydrothermal deposit "footprints" and alteration chemistry can be acquired by analysing spectral ground response, particularly in the short-wave infra-red where a great deal of mineralogical information is available. Materials which can be mapped include clays and magnesium/iron/aluminium oxyhydroxides, with specific information being obtainable (using higher resolution airborne methods such as HyMap) on mineral composition, abundance and physicochemistries (including crystallinity) for minerals such as kaolinite which can be used as a surrogate for identifying transported vs. in situ material. High resolution mineral maps enable the recognition of various types of hydrothermal alteration patterns and the localisation of fluid pathways, including geochemically discrete alteration shells in IOCG type deposits which correspond to distinct mineral distributions. Potassic alteration in mafic rocks was detected using a combination of MgOH, Fe2+ and Fe 3+ mineral maps combined with white mica composition and abundance products. MgOH, Fe2+ and Fe 3+ mineral products were also used to distinguish amphibole-bearing rocks, which host some of the Fe oxide Cu-Au deposits area, from other various mafic rocks.