Australia’s oldest subduction-like setting? Fingerprinting the 3.1 Ga Whundo Group

Speaker

Dr Eric Vandenburg

Abstract

Understanding how Earth’s early crust was recycled is crucial for explaining interactions between the lithosphere, oceans, and atmosphere, and therefore the planet’s early habitability. Whether subduction-like processes operated during the Archean (>2.8 billion years ago) remains highly debated because very little crust from this period is preserved and most evidence is ambiguous. This seminar focuses on the 3.14-3.11 billion-year-old Whundo Group in the Pilbara Craton, one of the few Archean rock sequences that may preserve evidence of arc-like tectonic activity. The exceptionally well-preserved 8-9 km-thick succession contains volcanic rock types characteristic of modern subduction zones, including calc-alkaline lavas, adakites, high-magnesium volcanic rocks, and the oldest known extensive boninites. Geochemical analyses indicate that these magmas were derived from at least two mantle sources and formed under unusually water-rich conditions. Estimates suggest mantle water contents comparable to those in modern subduction-zone mantle wedges, while zircons record magmas containing up to 9 wt.% water. These features closely resemble those of modern volcanic arcs. I propose that the Whundo Group formed through “dripduction”, a short-lived process in which hydrated lithosphere sank into the mantle without the development of continuous plate boundaries or fully modern plate tectonics. This process could have recycled surface water into the mantle and generated arc-like magmas, creating localized subduction-style activity on the early Earth. The Whundo Group therefore provides compelling evidence that proto-subduction occurred by 3.1 billion years ago, enabling volatile exchange between the mantle, oceans, and atmosphere long before the onset of modern, self-sustaining plate tectonics.

Bio

Dr. Eric Vandenburg is an igneous petrologist and isotope geochemist. After earning a BSc (Honours) from the University of British Columbia and spending a year in mineral exploration, he completed a PhD at Monash University in 2025, combining trace element geochemistry, geochronology, and novel stable isotopes to investigate Earth's early continental crust and the origins of subduction-like processes in the Archean. Eric is now a Postdoctoral Research Fellow at Adelaide University in the ARC Centre in Critical Resources for the Future, with interests spanning Ni-Cu (PGE) and porphyry Au-Cu systems, mantle heterogeneity and stable isotope method development.