Geophysical constraints of shear zones and geometry of the Hiltaba Suite granites in the western Gawler Craton, Australia

Abstract

The emplacement of the ca 1590-1575 Ma Hiltaba Suite granites records a large magmatic event throughout the Gawler Craton, South Australia. The Hiltaba Suite granites intrude the highly deformed Archaean-Palaeoproterozoic rocks throughout the craton nuclei. Geophysical interpretation of the poorly exposed central western Gawler Craton suggests that the region can be divided into several distinct domains that are bounded by major shear zones, exhibiting a sequence of overprinting relationships. The north-trending Yarlbrinda Shear Zone merges into the east-trending Yerda Shear Zone that, in turn, merges into the northeast-trending Coorabie Shear Zone. Several poorly exposed Hiltaba Suite granite plutons occur within a wide zone of crustal shearing that is bounded to the north by the Yerda Shear Zone and to the south by the Oolabinnia Shear Zone. This wide zone of crustal shearing is interpreted as a major zone of synmagmatic dextral strike-slip movement that facilitated the ascent of Hiltaba Suite granite intrusions to the upper crust. The aeromagnetic and gravity data reveal that the intrusions are ~ 15-25 km in diameter. Forward modelling of the geophysical data shows that the intrusions have a tabular geometry and are less than 6 km deep.

Evidence for Early Mesoproterozoic Arc Magmatism in the Musgrave Block, Central Australia: Implications for Proterozoic Crustal Growth and Tectonic Reconstructions of Australia

“…The Hiltaba Suite may be an inboard expression of the south-dipping subduction to the north, much like the GRVs. Intrusion of the Hiltaba Suite in a compressional setting has recently been proposed (McLean and Betts 2003) and is interpreted in this study as resulting from the stresses formed by the encroaching NAC continental fragment from the north. Regional north-south compressional metamorphism in this time period is seen over much of the NAC, including the 1.595-1.57-Ga Chewings Orogeny (e.g., Collins and Shaw 1995;Young et al 1995;Williams et al 1996;Hand and Buick 2001;Rubatto et al 2001) and the ∼1.585-Ga early Isan Orogeny (e.g., Page and Sun 1998;Giles and Nutman 2002).…”

Three-dimensional potential field modelling of the subsurface morphology of complex maar volcanoes - Examples from the Newer Volcanics Province, Western Victoria

“…Any geophysical model is limited in that an infinite number of solutions to the data may exist (Whiting 1986;Valenta et al 1992;Jessell et al 1993;McLean & Betts 2003). The examples presented here are constructed from a combination of 2D and 3D modelling techniques and are constrained by all the available geologic data, thus limiting the number of plausible solutions.…”

Orogen-perpendicular structures in the central Tasmanides and implications for the Paleozoic tectonic evolution of eastern Australia

“…Potential field (gravity and magnetic) data can provide insights into crustal architecture and terrane analyses, and are specifically vital for investigating regions of limited rock exposures Whiting, 1986;Jessell and Valenta, 1996;Gunn et al, 1997;McLean and Betts, 2003;McLean et al, 2008;Stewart and Betts, 2010). Although interpretation of gravity and aeromagnetic data does not necessarily provide unique solutions McLean and Betts, 2003;McLean et al, 2008;Stewart and Betts, 2010), the combined use of geological and geophysical constraints, such as borehole and seismic data, may significantly reduce the ambiguity, and serve as a powerful tool for investigating inaccessible terranes.…”

“…Although interpretation of gravity and aeromagnetic data does not necessarily provide unique solutions McLean and Betts, 2003;McLean et al, 2008;Stewart and Betts, 2010), the combined use of geological and geophysical constraints, such as borehole and seismic data, may significantly reduce the ambiguity, and serve as a powerful tool for investigating inaccessible terranes.…”