Ngalia Basin Regional AEM survey summary results report

Abstract

Thundelarra Exploration Ltd was awarded funding via the Bringing Forward Discovery Geophysics and Drilling Collaboration initiative to conduct a regional airborne electomagnetic (AEM) surveying within the Ngalia Basin (the 'Ngalia Basin Regional AEM survey'). This survey was flown by Fugro Airborne Surveys in November 2010 The principal targets of Thundelarra?s exploration efforts within the Ngalia Basin are; 1) Uranium mineralisation hosted by the Tertiary sediments that cover large portions of the basin, and indeed around 99 percent of the Thundelarra exploration project area. The Tertiary sequence has demonstrated potential for calcrete deposits, and excellent theoretical potential to host ISR-amenable 'palaeochannel-type' deposits, with suitable hydrogeological characteristics, and an excellent sedimentary/metallogenic provenance; and 2) Bigrlyi-type uranium mineralisation. This type of mineralisation is hosted by the Carboniferous Mount Eclipse Sandstone. The Ngalia Basin has yet another potential mineralisation style; MVT sulphide deposits associated with the thick sequences of dolomitic rocks (principally the Walbiri and Wanapi Dolomites) located along basement highs and proximal-to fault zones that occur within the centre of the basin. Recent gravity surveys (i.e. structural targets) and XRF analysis of petroleum well chips (weak Cu + Pb + Zn metal anomalies) hint at the potential for this target style. The Ngalia Basin Regional AEM survey aimed to collect high quality airborne data over an area of 3300 km2. This represents a substantial portion (approximately 30 percent) of the total Basin area. The results of this program have substantially benefited the exploration programme, by directly identifying a complex Tertiary paleovalley system. This also allows for areas of shallow Tertiary to be identified within which it is more economically feasible to explor for Bigrlyi-style deposits. There is also evidence that the EM data can be used to map lithological variation within the Mount Eclipse to provide paleo-permeability constraints, and thus broadly the prospective corridors.