Crustal Architecture of the Granites - Tanami Orogen: an Integrated Geophysical and Geological Study

Central Australia's Granites-Tanami Orogen (GTO) is a significant gold producing province. Determining the architectural controls on mineralisation and crustal evolution of the orogen will facilitate future exploration. A whole of crust model has been generated through the multi-scale integration and interpretation of potential field geophysical and geological data. The orogen contains a basin architecture 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 largely obscured by poor outcrop, 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 upright and doubly plunging isoclinal fold trains of wavelengths 10 km. These folds are recognised through the interpretation and modelling 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 polyphase deformational patterns produced by the refolding of earlier folds around doubly plunging E to ESE trending fold axes with steeply N dipping axial surfaces. 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.