Abstract for SGA Townsville 2009

Preliminary compilation of data in the onshore Carptentaria Basin, Northern Territory. This basin, previously named the Dunmarra Basin, is poorly understood. This Record details the compilation of data in 3D for the basin. Data included are surface geological mapping, drillholes, gravity, magnetic, radiometric, visible LANDSAT, seismic reflection and digital elevation data.

Significant volumes of Big Lake Suite granodiorite intrude basement in the Cooper Basin region of central Australia. Thick sedimentary sequences in the Cooper and overlying Eromanga Basins provide a thermal blanketing effect resulting in elevated temperatures at depth. 3D geological maps over the region have been produced from geologically constrained 3D inversions of gravity data. The inverted density models delineate regions of low density within the basement that are inferred to be granitic bodies. The 3D maps include potential heat sources and thermally insulating cover, the key elements in generating an EGS play. A region was extracted from the Cooper Basin 3D map and used as a test region for modelling the temperature, heat flow and geothermal gradients. The test region was populated with thermal properties and boundary conditions were approximated. Temperatures were generated on a discretised version of the model within GeoModeller and were solved by explicit finite difference approximation using a Gauss-Seidel iterative scheme. An enhancement of the GeoModeller software is to allow the input thermal properties to be specified as distribution functions. Multiple thermal simulations using Monte-Carlo methods would be carried out from the supplied distributions. Statistical methods will be used to yield the probability estimates of the in-situ heat resource, reducing the risk of exploring for heat. A fast solver for the inhomogeneous heat equation in free space has been developed using Fourier domain techniques. Typical speed-ups for this strategy over the conventional solvers is better than 1000 to 1.

The new Australian geodetic VLBI network operated by University of Tasmania (UTAS) started regular observations in October, 2010. Three 12-meter "Patriot" radio telescopes are focused on improvement of the celestial and terrestrial reference frames in the southern hemisphere. We present first results from analysis of an eight-month set of geodetic VLBI data.

High-CO2 gas fields serve as important analogues for understanding various processes related to CO2 injection and storage. The chemical signatures, both within the fluids and the solid phases, are especially useful for elucidating preferred gas migration pathways and also for assessing the relative importance of mineral dissolution and/or solution trapping efficiency. In this paper, we present a high resolution study focused on the Gorgon gas field and associated Rankin trend gases on Australia's Northwest Shelf of Australia. The gas data we present here display correlate-able trends for mole %-CO2 and %C CO2 both areally and vertically. Generally, CO2 % decreases and becomes depleted in %C (lighter) upsection and towards the north; a trend which also holds true for the greater Rankin trend gases in general. The strong spatial variation of CO2 content and %C and the interrelationship between the two suggests that processes were active to alter the two in tandem. We propose that these variations were driven by the precipitation of a carbonate phase, namely siderite, which is observed as a common late stage mineral. This conclusion is based on Rayleigh distillation modeling together with bulk rock isotopic analyses of core, which confirms that CO2 in gases are genetically related to the late stage carbonate cements. The results from this study have important implications for carbon storage operations and suggest that significant CO2 may be reacted out a gas plume over short migration distances.

Examination of developing geothermal exploration techniques and a geothermal play systems framework in Australia.

Seismic line 07GA-IG1, described here, forms part of the Isa-Georgetown-Charters Towers seismic survey that was acquired in 2007. The seismic line is oriented approximately northeast-southwest and extends from northwest of Cloncurry in the southwest to east of Croydon in the northeast (Figure 1). The acquisition costs for this line were provided jointly by Geoscience Australia and the Geological Survey of Queensland, and field logistics and processing were carried out by the Seismic Acquisition and Processing team from Geoscience Australia. Six discrete geological provinces have been interpreted on this seismic section (Figure 2). Two of these, the Numil and Abingdon Provinces, only occur in the subsurface. The Mt Isa Province occurs in the southwest, with the Kowanyama Province occurring on the middle of the section and the Etheridge province in the northeast. The Millungera Basin, first observed on two seismic lines in the 2006 Mt Isa seismic survey, occurs beneath shallow cover of the Jurassic-Cretaceous Carpentaria Basin and sits above the Kowanyama Province.

The Common Earth Model is a collection of data collated by Geoscience Australia that aims to give a unified overview of the geology of Australia. The data are visualised in the Geoscience Australia 3D Data Viewer software and the intention is to give users a rich environment to explore diverse geological data. Geoscience Australia has collated these datasets from a wide range of sources. Copyright in all content on the DVD remains with the originating organisations and individuals, and may not be reproduced without permission. The 3D Data Viewer software itself is released under Creative Commons Attribution 3.0.

SGA 2009 abstract

Six deep seismic reflection profiles totalling ~900 km were acquired across the Mount Isa Province in 2006 (Figure 1). Each vibe point was recorded to ~20 s TWT (two-way travel time), which equates to ~60 km depth. The aims of the survey were to develop a 3D model and a geodynamic history of the province, link deep crustal structure with known mineral deposits, and demonstrate the potential of deep seismic surveys in mineral exploration