Cratonic impact on clastic-dominated base metal deposits in continental rifts

Résumé fourni par la source

Sediment-hosted zinc-lead deposits of the clastic-dominated (CD) type provide much needed metals for the energy transition and global urbanization. There is a spatial correlation between the present-day location of CD-type deposits and craton edges, although it is unclear whether this is a causal relationship. In this paper, we use numerical models of continental rifting to investigate whether proximity to cratonic lithosphere enhances the ore-forming potential during rift basin evolution. Our results show that narrow asymmetric and wide rifts respond differently to the presence of close cratonic edges. The potential for metallogenesis in narrow asymmetric rifts decreases with increasing proximity to the craton edge. In contrast, metal source rock area and ore-forming mechanisms increase when wide rifts form close to a craton edge. We attribute these responses to the increased lithospheric strength on the craton-ward side of the rift that determines not only the initial fault geometry, but also the subsequent fault development and migration direction. This modifies the spatial and temporal overlap of the components of the mineral system required for deposit formation, i.e., source rock, fluid-focussing faults, and deposit host rock. The greatest metallogenic potential is found in the narrow margin of narrow asymmetric rifts formed far from a craton edge; here, the largest area of source rock is concentrated in the main border basin. The link between craton edges and metallogenic potential, therefore, is hypothesized to be due to the preferred initialization of rifts next to, and the preferential preservation of deposits on, the edges of stable cratons.

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