The Granites - Tanami Orogen Subsurface Geometry as Revealed by and Integrated Potential Field Geophysical and Geological Study

Abstract

The Granites Tanami Orogen (GTO) in central Australia is a significant gold producing province. Future exploration will be facilitated by determining the structural controls on mineralisation and crustal evolution of the orogen. A whole of crust model has been generated through the multi-scale integration and interpretation of geophysical, geological and remote sensing data. The architecture of the orogen is that of a basin that has been inverted, deformed and intruded during: a) the collision between the Kimberley and Tanami basins along the Halls Creek Orogen to form the North Australian Craton; and b) during the amalgamation of the North Australian Craton with the Central Australia Craton. These continent-continent collisions have resulted in a complex structural framework, which is further complicated by deep weathering and extensive regolith across the region. Reconnaissance style outcrop mapping coupled with potential field interpretation has identified two main phases of deformation. The first regional deformation event resulted in north- to northeast-trending isoclinal fold trains of wavelengths ~10 km or greater. These folds are recognised through the interpretation of joint gravity and magnetic anomalies and are confirmed in outcrop. Gold mineralisation within the GTO is coincident with the second regional deformation event, which is recognised in regional aeromagnetic data as poly-phase deformational interference patterns caused by the refolding of earlier folds around axes trending E to ESE. This defining of upper crustal architecture to structural features observable in sparse outcrop coverage could not be sufficiently identified without this combined geology and geophysical approach.