25-27 July 2023 | Fremantle, Perth, Western Australia

FT1 – Pilbara Craton: evolving Archean tectonic styles (July 17 – 23)

(Guides: Martin Van Kranendonk, Hugh Smithies) A week-long trip across the beautifully exposed Pilbara Craton, investigating two contrasting litho-stratigraphic terranes. This trip will commence with an exploration of the 3.5-3.2 Ga East Pilbara Terrane, with its classic granite dome-and-greenstone keel geometry indicative of “vertical tectonics”, and sites with traces of early life. It will then move to the western part of the craton, where we will investigate successions and structures that document a drastically different tectonic style, including an arc complex, and crustal-scale shear zones indicative of terrane accretion.

FT2 – Redefining Archean terrane boundaries: A radical update within the Yilgarn Craton (20-22 July)

(Guides: Raphael Quentin de Gromard, Tim Ivanic) The far west and southwest Yilgarn represents perhaps the most geodynamically complex portion of the Yilgarn Craton and has recently become one of Western Australia’s prime new exploration frontiers. Recent work by the Geological Survey of Western Australia has proposed that the boundary between the c. 3010–2635 Ma Youanmi Terrane and the c. 2705–2610 Ma South West Terrane of the Archean Yilgarn Craton be relocated approximately 200 km to the southwest along the southwestern deformation front of the newly defined c. 2665–2635 Ma Corrigin Tectonic Zone (CTZ). This three day excursion will visit key exposures of tectonized greenstones and high-grade gneisses in the well-exposed Toodyay-Northam area (about 100 km from Perth). The field sites will be an ideal platform from which to discuss the geological history of the southwest Yilgarn, the rationale for location of the terrane boundary and implications for Au–Cu, Ni–PGE, Ti–V, VMS, and Fe mineral systems.

Simplified interpreted bedrock geology (IBG) of the southwest Yilgarn produced during the 2020–2021 Accelerated Geoscience Program (AGP) of the Geological Survey of Western Australia (GSWA) showing the location of the old and updated terrane boundary between the South West Terrane and the Youanmi Terrane as well as the fieldtrip area.