This map is part of a series which comprises 50 maps which covers the whole of Australia at a scale of 1:1 000 000 (1cm on a map represents 10km on the ground). Each standard map covers an area of 6 degrees longitude by 4 degrees latitude or about 590 kilometres east to west and about 440 kilometres from north to south. These maps depict natural and constructed features including transport infrastructure (roads, railway airports), hydrography, contours, hypsometric and bathymetric layers, localities and some administrative boundaries, making this a useful general reference map.

G50/B1-2647-2 Vertical scale: 50

(west) I50/B1-119

Geoscience Australia (GA) has been acquiring both broadband and long-period magnetotelluric (MT) data over the last few years along deep seismic reflection survey lines across Australia, often in collaboration with the States/Territory geological surveys and the University of Adelaide. Recently, new three-dimensional (3D) inversion code has become available from Oregon State University. This code is parallelised and has been compiled on the NCI supercomputer at the Australian National University. Much of the structure of the Earth in the regions of the seismic surveys is complex and 3D, and MT data acquired along profiles in such regions are better imaged by using 3D code rather than 1D or 2D code. Preliminary conductivity models produced from the Youanmi MT survey in Western Australia correlate well with interpreted seismic structures and contain more geological information than previous 2D models. GA has commenced a program to re-model with the new code MT data previously acquired to provide more robust information on the conductivity structure of the shallow to deep Earth in the vicinity of the seismic transects.

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In 2009, as part of its Onshore Energy Security Program, Geoscience Australia, in conjunction with the Northern Territory Geological Survey, acquired 373 km of vibroseis-source, deep seismic reflection, magnetotelluric and gravity data along a single north-south traverse from the Todd River in the south to nearly 30 km north of the Sandover Highway in the north. This traverse, 09GA-GA1, is referred to as the Georgina-Arunta seismic line, extends from the northeastern Amadeus Basin, across the Casey Inlier, Irindina and Aileron provinces of the Arunta Region and Georgina Basin to the southernmost Davenport Province. Here, we report the results of an initial geological interpretation of the seismic and magnetotelluric data, and discuss some preliminary geodynamic implications.

These data are the definitive time series data collected at Geoscience Australia's geomagnetic observatories in Australia and Antarctica. Some data are also provided for historic Australian observatories and some observatories operated by New Zealand and Indonesia.

Structures and structural (tectonic) processes provide critical controls on the evolution of hydrothermal mineral systems, both as pathways for fluid flow and as a trigger or driver. Not all these structures or tectonic processes are, however, necessarily obvious, particularly when the scale of study is restricted to a mineral deposit alone. This is because mineral deposits are just a `symptom' of a much larger system 'a mineral system' which involves enormous energy and mass fluxes. Using mineral systems thinking is a powerful tool for explorers. The scale of a mineral system is many orders of magnitude larger than the individual mineral deposit, and consequently, the system offers a far larger target than the deposit. For example, a deposit only 500 m wide may have a fluid outflow zone many tens of kilometres wide, such as in the Eastern Goldfields. Similarly, the zone of depletion of the metal-rich source rock may be many tens of kilometres in extent, such as in Broken Hill. A mineral system is a generic concept. Here, I use an example from the gold mineral system of the Eastern Goldfields Superterrane of Western Australia to consider some of the less obvious, but nevertheless important, structures and their attendant processes, as well how to recognise them.

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