Proterozoic turbiditic depositional system (Tanami Group) in the Tanami region, northern Australia, and implications for gold mineralisation

Abstract

Sedimentological interpretation of outcrop and drillcore, integrated with previously published seismic interpretation and regional chemostratigraphy, is used to establish a depositional model for gold-bearing Paleoproterozoic rocks of the Tanami region. Analyses of the Dead Bullock Formation and Killi Killi Formation of the Tanami Group form a basis for future correlations across northern Australia. Poorly exposed Paleoproterozoic sandstone, siltstone and claystone of the Killi Killi Formation record development of a deep-water, basin-floor turbidite system composed of channelised sandy lobes with muddy lobe fringes. The sediment source was located to the northwest. Underlying the Killi Killi Formation are the poorly exposed dark claystones of the upper Dead Bullock Formation, forming a condensed section. We interpret that this depositional system was an important control on gold mineralisation in both the Killi Killi Formation and the underlying Dead Bullock Formation of the Tanami Group. Gold deposition is enhanced within the Dead Bullock Formation where crustal faults intersect claystone facies. Similar facies in the Killi Killi Formation may also host gold mineralisation. Deep exploration holes at the Titania and Old Pirate prospects could potentially intersect the stratigraphically underlying gold-bearing claystones of the Dead Bullock Formation.

Key Words:

• Proterozoic
• turbiditic
• deep-water
• facies associations
• isopach surface
• gold
• exploration

Acknowledgements

This study could not have taken place without the support and enthusiasm of Newmont Australia and Tanami Gold. Many thanks are given to Pascal Hill, Martin Smith and Rosalyn Da Costa from Newmont and Tim Smith from Tanami Gold who provided initial collaboration opportunities. The Northern Territory Geological Survey also provided logistical support, and Andrew Crispe provided many useful discussions. AtGeoscience Australia, George Gibson, Lesley Wyborn and David Champion provided helpful and fun discussions. We are grateful to Jamie Vinnels who provided many discussions and critically read an earlier version of the manuscript. Ian Tyler, Simon Bodorkos, Elizabeth Jagodzinski and two anonymous reviewers are thanked for their detailed reviews and thoughtful suggestions, which greatly improved the focus of the paper. This contribution is published with permission of the Chief Executive Officer of Geoscience Australia.