1Geological Survey of New South Wales, Department of Regional NSW, Maitland, Australia
During the late 20th century, Australia’s geological survey organisations (GSOs) completed 1:250,000 scale surface geological mapping of the continent. This work provided a framework for mineral exploration that led to the discovery of most of the surface and near-surface deposits in areas of outcropping basement that form the basis of the country’s current mineral production. From the 1970s, geological mapping was augmented by regional geophysical data and from the mid-1990s increased geochronological analysis, which supported a second generation of higher resolution mapping under the National Geoscience Mapping Accord into the early 21st century. However, this second wave of mapping, which often focused on areas of good quality outcrop with known mineral potential, did not lead to many significant discoveries and over 80% of the country’s current mineral production now comes from deposits discovered prior to 1980.
In order to provide a framework for mineral discovery in the 21st century, Australian GSOs need to change the search space and provide the exploration industry with the data they need to successfully explore deeper and step out into the 75% of the Australian continent where prospective basement is buried under younger, non-prospective cover. Essentially, GSOs must map “the geology that matters” – defining the structural architecture, temporal evolution and lithologies of potentially prospective geological terranes, regardless of whether they are exposed at the surface, or not.
This work has already started in New South Wales (NSW), with the NSW Seamless Geology providing an interpreted lithotectonic framework for the state, based primarily on surface mapping and potential field geophysical data. However, further geological data is required to support this model, particularly in undercover terranes. As participants in the ten-year MinEx CRC National Drilling Initiative (NDI), Australia’s GSOs will generate new precompetitive geoscientific data over several underexplored, undercover regions across the continent. Equally importantly, the NDI will support development of cheaper, faster drilling technologies, real-time sensing technologies and new concepts and decision-making tools that will aid mineral exploration in deep and/or covered terranes, thereby making large parts of the continent more accessible to mineral exploration.
Concurrently, Australia’s GSOs are deploying new technologies to augment existing national datasets. The ~55km-spaced stations of the collaborative Australian Lithospheric Architecture Magnetotelluric Project (AusLAMP) is delivering a lithospheric-scale conductivity model that can be used to define areas of anomalous fluid flow for further investigation. Completion of the AusAEM electromagnetic survey across Australia over the next four years will deliver a near-surface conductivity model that can be used to define depth to basement, as well as potential for mineral and groundwater resources. New geochemical and isotopic datasets are also being used to define fluid sources and crustal evolution at a continental scale.
As we enter the third decade of the 21st century, Australia’s GSOs face a watershed moment. We must and are transitioning from mapping the surface geology, to mapping prospective geology and delivering new types of data, to create a framework for the discovery of the new deposits needed to support Australia’s mineral industry into the second half of the century.
Chris was Executive Director of the Geological Survey of NSW from June 2015 to December 2020. Prior to this, he spent 17 years as a researcher and manager at CSIRO, where his work focussed on the formation of and exploration for gold and base metal deposits in ancient and modern terranes.