Geodynamic controls on sediment-hosted metal deposits in continental rifts

Many large sediment-hosted clastic-dominated (CD) base metal deposits occur in failed continental rifts and the passive margins of successful rifts, e.g., in the MacArthur Basin, Australia, and in the Selwyn Basin in Canada. Continental rifts and their margins provide a specific mix of higher temperatures and heat flows, fault networks facilitating fluid flow, sediment input from the generated topography, and ocean water contributing pelagic sediments and sulfates. The large-scale geodynamics thus provide the necessary ingredients for metal leaching, with metal deposition then occurring on much smaller spatial and temporal scales.

To identify the specific geodynamic conditions conducive to large CD-type deposit formation, we numerically model 2D rift systems from inception to break-up with the geodynamic code ASPECT (Heister et al. 2017) coupled to the landscape evolution model FastScape (Braun and Willett 2013; Neuharth et al. 2022). With high-resolution (~300 m) simulations, we investigate how rift type (e.g., wide versus narrow), the presence of a craton, and the efficiency of erosional and depositional processes affect the formation of potential source and host rock domains. We subsequently analyse the optimal alignment of these regions where metals are leached and deposited, respectively, with faulting events providing fluid pathways between them. For these favorable co-occurrences, we estimate the potential size of metal deposits and identify those conditions that predict the largest deposits.

Braun and Willett. 2013. Geomorphology 180–181. 10.1016/j.geomorph.2012.10.008.

Heister et al. 2017. Geophys. J. Int. 210 (2): 833–51. 10.1093/gji/ggx195.

Neuharth et al. 2022. Tectonics 41 (3): e2021TC007166. 10.1029/2021TC007166.