Magnetotelluric Study of the Southern Margin of the Capricorn Orogen, Western Australia

Abstract:

We present the current status and the preliminary results of a magnetotelluric (MT) study that is being performed in the Capricorn Orogen, in northern Western Australia. This project is a component of large multi-disciplinary geoscience project on the ‘Distal Footprints of Giant Ore Systems’. The Capricorn Orogen, a largely Proterozoic orogenic belt, is being used as a natural laboratory to develop methods for exploring for mineral deposits ‘under cover’.

The MT dataset consists of a total of 240 broadband magnetotelluric stations (BBMT) and 84 long period stations (LMT). Analysis of the dataset reveals the area to have complex 3-D variations in electrical conductivity, making 3-D interpretation methods essential.

The first 3-D inversion model encompasses south-eastern part of the Capricorn Orogen (Padbury-Bryah Basins) and the adjoining Yilgarn Craton, and involves the inversion of 58 BBMT sites. The results shown a prominent resistive feature that is tentatively correlated with the northern boundary of the Yilgarn Craton. Apart from this, the other main geoelectrical feature is a high conductivity body located within the Yilgarn Craton. This structure could be related to tectonic features associated with the accretion of the different terranes composing this part of the craton. Forward models were used to validate these and other structures.

Major faults occurring at cratonic margins are known to be important indicators of increased prospectivity and our preliminary results suggest MT surveys are a useful tool for regional scale exploration in the study area.