Hematite geochronology reveals a tectonic trigger for iron ore mineralization during Nuna breakup

Abstract

Hematite and goethite deposits hosted in banded iron formations (BIFs) in the Pilbara craton (Western Australia) represent one of Earth’s most significant Fe reserves; however, the timing and tectonic triggers underpinning deposit genesis remain contentious. Uncertainty in ore genesis stems from a lack of direct age measurements, which could aid in correlating periods of BIF mineralization with tectono-thermal events observed elsewhere. Archean–Paleoproterozoic BIFs in the Hamersley Province host extensive martite–microplaty hematite orebodies that formed at 2.2–2.0 Ga, based on indirect constraints. In contrast, combined hematite in situ U-Pb geochronology and (U-Th)/He thermochronology demonstrate that martite–microplaty hematite ores in the Chichester Range crystallized ca. 1.26–1.22 Ga and underwent cratonic denudation between ca. 0.57 and 0.38 Ga. Nanoscale imaging of dated hematite indicates that U-Th-Pb is lattice bound and not hosted in inclusions. New U-Pb hematite ages overlap with other mineral ages reported at the margins of the Pilbara and Yilgarn cratons (1.3–1.1 Ga), where mineral formation was driven by plate reorganization following breakup of the Nuna supercontinent. This age correlation suggests that a combination of increased orogenic (+diagenetic) and heat (+fluid) generative processes resulting from supercontinent reconfiguration was a key trigger for iron ore formation in the Pilbara craton