Exploring for the Future—Preliminary HyLogger results of borehole samples from the Southern Stuart Corridor Project area. Northern Territory

The hyperspectral HyLoggerTM instrument for collecting high resolution spectra data of drill core and drilling chips is a widely used and powerful in mineral and energy exploration, including sediment hosted mineralisation and hydrocarbons. It enables mapping of hydrothermal, diagenetic, and weathering assemblages, clarification of stratigraphy, and determination of primary mineralogy. This report presents key results of hyperspectral data from the HyLogger-3TM instrument collected from drilling in the Southern Stuart Corridor (SSC) project area in the Northern Territory conducted as part of Exploring for the Future (EFTF)—an eight year, $225 million Australian Government funded geoscience data and information acquisition program focused on better understanding the potential mineral, energy and groundwater resources across Australia. The results show that HyLogger plots are in most cases in the most effective means of identification of stratigraphic contacts. HyLogger plots are also especially effective and determining the depth and mineralogy of weathering and distinguishing provenance in shallow transported material such as palaeovalley fill and alluvium. Geological observations are however still crucial, especially in determining texture, which cannot be determined by the HyLogger scans or from photographs of chips and core, and in cases where contamination obscures or confuses the spectral signals. Weathering in the SSC can be determined by the appearance of dickite and poorly crystalline kaolinite. This allows a better determination of base of weathering than visual means: generally based of the presence of oxidised iron phases such as goethite and haematite (which are not definitive where the rocks already contained these prior to weathering), or where oxidised iron deposition has not occurred. This aids in depth of weathering mapping from regional AEM data. The ability of the HyLogger to discriminate between swelling (montmorillonite) and non-swelling (kaolinite, dickite) clays is potentially significant in the prediction of aquifer properties and the validation of borehole MR methods. The detection of zones of potential dolomitisation and dedolomisation through mineralogy (presence of dolomite and possible secondary calcite and magnesite, respectively) in carbonate units has the potential to similarly predict properties in carbonate units, through the potential increase in porosity/permeability of the first and decreased porosity/permeability of the second.