The project area covers the Youanmi, Narryer, and South West Terranes in the western half of the Yilgarn Craton. The work includes the boundaries where these terranes meet the surrounding tectonic units.
Since the late 1990s, we have been conducting 1:100 000-scale mapping, resulting in updated digital map packages, explanatory notes for geological units, and numerous reports on the region’s complex tectonic history. This adds to earlier 1:250 000-scale mapping from the 1970s and 1980s.
Mapping of the western Yilgarn Craton is still ongoing, with new bedrock geology layers being created and older interpretations refined in areas that are difficult or poorly studied. The area has been surveyed with aeromagnetic and radiometric surveys (25–400 m line spacing), gravity surveys at 2.5 km spacing, and satellite imagery.
Complimentary crustal-scale geophysical datasets, such as seismic reflection, magnetotelluric (MT) data, have enabled construction of 3D geological models. Data from SHRIMP U–Pb (Uranium–lead) zircon geochronology, novel isotope geochronology, whole-rock geochemistry, structural analysis, and other methods help uncover the tectonic, magmatic, stratigraphic, and mineralisation history of the western Yilgarn Craton.
The (GIS) package is the most up-to-date resource for this project. It includes digital geology layers, cross-sections, geophysical images, satellite data, geochemistry results, and field observations. This package brought together bedrock geology interpretations from the Youanmi 2020 GIS package and the Southwest Yilgarn 2021 Geological Exploration Package. To finish combining these datasets, we are focusing on collecting and interpreting data along the western edge of the Yilgarn Craton over the next few years.
See this map of the West Yilgarn project area and simplified geological map showing available interpreted bedrock geology, 1:100 000 Geological Series maps and digital updates. The yellow outline identifies the knowledge gap of the western margin of the Yilgarn Craton.
Current fieldwork is focusing on regions that will help to better understand key geological features. These include major shear zones such as the Corrigin Tectonic Zone and the Darling Fault, and the boundary between the Narryer and Youanmi Terranes.
Current projects
Collaborative projects with universities are continuing, including geochemical, metamorphic, and structural studies, 3D modelling and multiple isotopic studies.
Much of this work is supported by the Exploration Incentive Scheme (EIS).
Geological evolution of the western Yilgarn Craton
The western Yilgarn Craton comprises ancient granite-greenstones and high-grade gneisses. These rocks host important deposits of metals like gold, iron ore, nickel, copper, lead, zinc, tungsten, molybdenum, bismuth, vanadium, titanium, beryllium, lithium, tin, tantalum, and uranium. There is potential to discover many more mineral deposits in the region.
The Youanmi Terrane makes up 58 percent of the 850 by 1000 km Yilgarn Craton, the Narryer Terrane forms 1.5 percent, and the South West Terrane makes up 5 percent. These terranes have a long and complicated geological history involving protocratonic crustal components that become reworked by tecto-magmatic processes. Understanding these processes and where they occurred helps scientists track the traces of major mineral systems throughout geological history.
See this updated stratigraphic framework for the Murchison and Southern Cross Supergroups showing relative probability curves for volcanic, plutonic and detrital zircon ages.
Narryer Terrane
The Narryer Terrane, located in the northwest of the Yilgarn Craton, contains the oldest rocks in Australia and has a poorly understood boundary with the Youanmi Terrane to the southeast. Migmatitic gneisses and layered mafic rocks have been dated at 3.73 Ga and zircon crystals in quartzite and conglomerate at Mount Narryer and Jack Hills have been dated at 4.404 Ga, older than the oldest rocks on Earth, which has attracted a lot of scientific interest in the region.
The geology of the wider Narryer Terrane is not well understood, so it is a focus of our current work.
Youanmi Terrane
The Youanmi Terrane, includes the older Southern Cross Supergroup, as well as more voluminous Murchison Supergroup deposited between 3.02 and 2.71 Ga. During and after these depositional periods, a variety of granitic rocks intruded, and were variably involved with later shear zones between 2.73 and 2.60 Ga.
South West Terrane
The 2020–21 Southwest Yilgarn Accelerated Geoscience Program (AGP) led to new interpretations that shifted the boundary between the Youanmi and South West Terranes about 200 km further southwest.
Immediately northeast of the updated terrane boundary, we identified the Corrigin Tectonic Zone (CTZ). The CTZ is between 50 and 150 km wide, comprising multiple shear zones that formed under high-pressure, high-temperature conditions between 2.66 and 2.63 Ga. This newly defined terrane boundary region is an exciting and developing area for current mineral exploration.
Data and publications on the West Yilgarn Craton
Detailed descriptions of all lithological units in the Youanmi Terrane can be accessed through the Explanatory Notes System (ENS) in GeoVIEW.WA.
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