• Ley, Yusen
• Abdat, Tania
• Anand, Ravinder
• Gonzalez-Alvarez, Ignacio
• Salama, Walid

Abstract

This report evaluates a dataset acquired with a Spectrem2000 airborne electromagnetic (AEM) system at the Neale and Zanthus tenements, and integrates the results with the available drilling and field observations for the Neale tenement to provide insights on the regolith architecture. The electromagnetic (EM) data yielded inferred variations of conductivity with depth, which have been compiled as maps and profiles for both tenements. The Zanthus tenement has no available drilling information, and therefore interpretation of regolith architecture at this site was not conducted.The Spectrem2000 dataset was interpreted after processing the data using a CSIRO-Geosciences workflow and inversions with a layered earth algorithm. The AEM interpretation, when integrated with the geological and regolith context, has proven to be a highly reliable technique for mineral exploration in this area in describing regolith thickness variability and architecture.A regolith thickness map of the surveyed portion of the Neale tenement suggests thickness variations in the variations between 6 and 70 m. Thickness increases towards the Southeast due to the thickening transported cover of the Eucla Basin.Thickness also increases towards the Northeast, which is related to a complex background paleodrainage channel set of Northwest-Southeast secondary paleochannels draining into a major Northeast-Southwest paleochannel feature.The transported cover varies from 2-25 m in thickness, and the in situ saprolite spans from 22 to 70 m in thickness. Regolith architecture is defined by the lateral variability of four mineral units: a ferruginous transported sediment package (2-25 m thick), silcrete (4-20 m thick), an upper kaolinitic saprolite and a lower ferruginous sandy saprolite unit (18-50 m thick), over a granitic/gneiss and gabbro/basalt basement. These units are laterally continuous throughout the area surveyed at the Neale tenement.The integration of AEM data, drill data and field observations suggests that the silcrete unit comprises a strongly silica cemented unit that contains weakly cemented areas. Geochemical sampling above these silcrete weakly cemented "windows" are potentially the most reliable areas to obtain geochemical information of the basement, since geochemical dispersion processes in the basement and through the regolith can potentially reach the surface through these more permeable silcrete "windows".Spectrem Air Ltd. has identified an AEM geophysical basement anomaly from the dataset, confirmed by this study.This anomaly is located in the Atlantis prospect in line 11040.

Topics

• impedance spectroscopy
• mineral
• dispersion
• surface
• layered
• analytical electron microscopy