Translithospheric fault targeting for giant magmatic (-hydrothermal) ore deposit discoveries: recent advances and leading practices

Abstract

Improving discovery rates for Tier 1 magmatic ore deposits requires more accurate prediction of camp-scale structural targets and mapping of (trans-)lithospheric fault zones (LFZs). Here we review LFZ architecture, evolution and behaviour, and their spatial correlation with large ore deposit clusters based on >120 global case studies of magmatic Ni-Cu (-PGE) and porphyry Cu (-Au,Mo) deposits. At belt-scale, the most prospective LFZs are the longest and deepest ones formed at lithospheric domain boundaries (“primary strike-parallel”). At district- to camp-scales, the strongest structural predictor for giant Ni and Cu discoveries is proximity to secondary transverse LFZ intersections that provided long-lived, subvertical, pipe-like, mantle-tapping conduits. The transverse LFZ correlation is stronger for large porphyry Cu deposits (∼90% within 5 km) than for large magmatic Ni-Cu (-PGE) deposits (∼82% within 25 km).

Magmatic-hydrothermal mineral systems are driven bottom-up by transfer of mechanical stress, heat, fluid, and metals from upwelling asthenosphere or slab subduction. Positive feedback from thermal, reaction, and strain softening partitions these drivers first into translithospheric fault zones, which evolve at the expense of transcrustal fault zones to efficiently channel the extreme energy, fluid and metal fluxes required to form giant magmatic-hydrothermal deposits. The dynamic fault-valve behaviour of LFZs, triggered by intermittent coupling across transient rheological barriers, enhances system self-organization and drives both exceptional fertility enhancement (when stalled) and extreme fluid fluxes (when released).

From our results, we identify key knowledge gaps and future research priorities, and propose a refined, systems-based approach to mapping LFZs aimed at enhancing the targeting of giant ore systems and mineral resource discovery performance.