2016-2017 CORE Geophysics and Drilling Collaborations Initiative, Final Report of 2016 Program, Undercover structure of the uranium-prospective Mt Eclipse Sandstone in the eastern Ngalia Basin

Abstract

Energy Metals Ltd (EME) has completed an integrated Drilling and Geophysical exploration program under the 2016-2017 CORE initiative. This report outlines the main achievements, and also discusses the rationale behind EME's program to better understand the undercover geology of the uranium-prospective, yet under-explored, eastern Ngalia Basin. Known undercover uranium prospects in this area include the Paladin Energy (PDN)-owned Minerva prospect and its along-strike extension, the Malawiri prospect (EME-PDN joint venture). The project area, within EL 24451 and ELR 41, consists of 70-100 m thick Cenozoic cover sequences of the Whitcherry Basin, which unconformably overlies the Neoproterozoic-to-Carboniferous succession of the Ngalia Basin. In late 2014 EME flew a high-resolution magnetic and radiometric survey over the western part of EL 24451. In order to 'see through' the relatively non-magnetic cover sequences into the underlying basement, EME's geophysical consultants developed a magnetic imagery deep-pass filtering technique; this led to development a new geological model for the eastern Ngalia Basin. In this area, Palaeozoic units, including the uranium-prospective Mt Eclipse Sandstone, are interpreted to form a series of complex, tightly folded synclinal, anticlinal and sometimes domal structures in which the anticlinal axes appear to be thrust faulted and prospective units repeated. The Minerva and Malawiri prospects appear to be located within the limbs of a tightly-folded syncline. Numerous other similar structural sites exist throughout EL 24451, suggesting that there is considerable potential for the presence of Malawiri- Minerva 'look-alike' deposits in stratigraphic repeats throughout the project area. reduced oxidation states in the prospective Mt Eclipse Sandstone. In order to precisely target the prospective units, EME first carried out a seismic survey, using the new passive seismic (PSS) method to derive the depth of Cenozoic cover and to determine the bedrock profile. Four PSS lines for 18 line-kilometres were extended across the interpreted structures. EME has developed a new geological model for the undercover eastern Ngalia Basin based on innovative deep filtering of magnetic imagery in order to 'see through' up to 100m of weakly magnetic Cenozoic cover. The collaborative drilling program successfully tested this model, in conjunction with new passive seismic survey (PSS) technology, to determine depth to bedrock and bedrock topography. EME has already successfully used PSS technology in depth-to-basement palaeochannel mapping. The PSS seismometers are portable, simple-to-use units that can provide estimates of thickness in soft sediment cover over hard basement rocks, provided some drillhole coverage is available along the seismic line to calibrate rock properties and derive a frequency-depth equation which can then be applied in areas between drillholes.