USING MULTISPECTRAL DATA TO TARGET POTENTIALLY GOLD-BEARING CONGLOMERATES IN THE MARBLE BAR BASIN, WESTERN AUSTRALIA
The Marble Bar basin hosts two different sedimentary units known to host gold-bearing conglomerates. The lower unit (unnamed) is 10-100 m thick and lies immediately beneath the Mt. Roe basalt. The upper unit, Hardy sandstone, is 50-200 m thick and lies beneath the Kylena basalt. Extensive cover by both basalts makes locating outcropping sedimentary rocks difficult. ASTER data was used to highlight the signature of sedimentary rocks and differentiate it from that of overlying basalts. This was completed by using a combination of different ASTER ratios and ratio math. For example, utilizing b14/b12 thermal bands defines areas of quartz-rich rock. Once desired ratios were identified and applied, a map was created targeting prospective areas to be examined during a two-week ground and air-supported basin-wide exploration program.
Field examination proved the pre-screening methodology to be highly effective in locating prospective conglomerates horizons with numerous new discoveries being made. Each conglomerate horizon was sampled, mapped and photographed. Rock samples were submitted to Genalysis Laboratory Services, Perth, WA for gold assay. Conglomerate samples returning high gold values (>1 ppm Au) were prioritized for follow-up work including detailed mapping and sampling. Conglomerate samples with low level anomalous gold (0.1-1 ppm Au) are scheduled for follow-up work at a later date.
In the Marble Bar basin, use of multispectral data helped identify potentially gold-bearing conglomerates prior to field reconnaissance thus saving time and money and quickly generating multiple new exploration targets. Utilizing a similar approach in other geologic environments should be feasible where similar contrasting rock types are present.