From discordance to discovery: extracting fluid-rock interaction timescales through zircon U-Pb analyses in the Arunta region, Central Australia

Zircon remains a preferred mineral for uranium-lead (U-Pb) geochronology due to its chemical durability. Despite its robustness, zircon is susceptible to isotopic modifications at lower temperatures in the presence of fluids, leading to discordant U-Pb data. These discordant data, through often overlooked, can illuminate the timing of fluid-related disturbance. Here we employ Bayesian modelling via a Monte Carlo approach to investigate the timing of disturbances in the Arunta region of central Australia. Renowned for its complex geological history, marked by multiple episodes of metamorphism and magmatism spanning more than 1.5 Ga, the Arunta region serves as an ideal case setting for understanding the interactions between geological processes and zircon U-Pb system integrity. By analysing discordant U-Pb data we reveal Pb-loss events corresponding to major tectonothermal episodes, notably the Petermann Orogeny and the Alice Springs Orogeny. These insights provide better temporal and spatial constraints on the complex tectonometamorphic history of the Arunta region and underscore the utility of discordant U-Pb data for reconstructing detailed geological histories. These results advocate for a reassessment of discordant U-Pb data, promoting their use as a valuable tool for understanding fluid mobility in the crust.

Citation: Lucy M. Mathieson, C.L. Kirkland, S. Bodorkos, M. Daggitt; From discordance to discovery: extracting fluid–rock interaction timescales through zircon U–Pb analyses in the Arunta region, Central Australia. Journal of the Geological Society 2025;; 182 (4): jgs2024–111. doi: https://doi.org/10.1144/jgs2024-111