Regional mineral exploration targeting based on crustal electrical conductivity variations from magnetotelluric data

Abstract

A magnetotelluric survey, comprising 40 stations, has been completed in the southern Yilgarn Craton. The preferred resistivity cross section through the crust and upper mantle shows the local lithosphere comprises three distinct units separated by steep boundaries. The central unit, interpreted as equivalent to the Southern Cross Domain has a resistive crust overlying a more conductive mantle. The two units on either side comprise a conductive lower crust overlying a resistive mantle. Dipping narrow zones of increased conductivity in the crustal part of the model correlate with known surface structures. The eastern margin of the Southern Cross Domain as inferred from deep crustal and mantle resistivity occurs about 50 km to the west of the Ida Fault, the margin of the domain at the surface. The three fold subdivision of the local lithosphere is consistent with the geologically and geochemically defined terranes and domains in this part of the Yilgarn. Current models for regional mineral exploration targeting emphasize the significance of major geological structures and the edges of cratonic blocks as areas of greatest prospectivity. The South Yilgarn MT dataset demonstrate that such features can be located based on variations in the electrical conductivity of the lower crust and mantle, which can be measured in a cost effective manner using the magnetotelluric method.