Australia's lithospheric architecture

To successfully target major new economic mineral deposits under cover requires a better understanding of the architecture of the whole lithosphere that focuses magmas and fluids to produce large deposits or deposit clusters. Geoscience Australia will augment its national pre-competitive geoscience datasets by acquiring a combination of high-resolution data along key transects of poorly understood geology and low-resolution data over very broad areas.

The ultimate goal of this theme is to create a new 3D map (model) of Australia's lithosphere. The 3D map will be built by integrating the new pre-competitive data and existing data with pre-existing regional-scale 3D geological maps. The 3D map will provide the spatial framework for understanding the geodynamic and metallogenic evolution of Australia.

Broad area and national initiatives

A key new initiative will be the commencement of AusLAMP—a Geoscience Australia and collaborator survey of long-period magnetotelluric data at a nominal scale of a half degree grid (55 km) across the continent. These data will provide a consistent continental-scale image of the electrical and magnetic structure of the entire Australian continental lithosphere and will provide insights to 'big' structures, particularly in the mantle lithosphere where other techniques such as seismic reflection provide little signal.

The survey will commence in Victoria and the nation-wide programme is expected to take between four and six years to complete, depending on the level of co-investment from collaborators. Data and processed products will be released throughout the project life span.

The building blocks of Australia are rooted in the deep fabric of the continent. The ancient foundations of Australia's continental crust can be mapped through isotopic tracers that provide the age when the precursor source (igneous) rock separated from the primitive mantle.

Compilation of existing samarium–neodymium (Sm–Nd) data for granites across the continent, together with new isotopic analyses of other systems (hafnium, oxygen, lead), will enable the major crustal elements and their boundaries to be better defined. Such knowledge will provide first-order constraints on the location of deep-cutting structures, which form a key input to area selection for specific mineral systems, such as nickel-sulphide deposits.

High-resolution transects

Geoscience Australia will co-invest with partners in the acquisition, processing and interpretation of high-resolution geophysical transects across key areas of the continent.

Geoscience Australia, the Geological Survey of Western Australia and the Geological Survey of South Australia will collaborate on a deep seismic reflection and magnetotelluric data traverse of the Nullarbor Plain.

This data-poor region is entirely undercover and thus poorly understood in terms of geology and mineral prospectivity. The survey will image the basement and several geological boundaries that are fundamental to the understanding of the evolution of the continent. The survey represents the final segment in an east-west deep seismic reflection transect of continental Australia.

Adding to the nation's seismic and magnetotelluric database, Geoscience Australia will provide acquisition support and state-of-the-art processing of a series of deep seismic reflection and magnetotelluric surveys in central New South Wales, northwest Queensland and northwest Western Australia. These data will be acquired in 2013–14 with processing and data release by 2014–15.

In future years transects could be acquired across north-eastern Victoria, northern Tasmania and/or the central Northern Territory.