Geodynamic controls on clastic-dominated base metal deposits

To meet the growing global demand for metal resources, new ore deposit discoveries are required. However, finding new high-grade deposits, particularly those not exposed at the Earth's surface, is very challenging. Therefore, understanding the geodynamic controls on the mineralizing processes can help identify new areas for exploration. Here we focus on clastic-dominated Zn–Pb deposits, the largest global resource of zinc and lead, which formed in sedimentary basins of extensional systems. Using numerical modelling of lithospheric extension coupled with surface erosion and sedimentation, we determine the geodynamic conditions required to generate the rare spatiotemporal window where potential metal source rocks, transport pathways, and host sequences are present. We show that the largest potential metal endowment can be expected in narrow asymmetric rifts, where the mineralization window spans about 1–3 Myr in the upper ∼ 4 km of the sedimentary infill close to shore. The narrow asymmetric rift type is characterized by rift migration, a process that successively generates hyper-extended crust through sequential faulting, resulting in one wide and one narrow conjugate margin. Rift migration also leads to (1) a sufficient life span of the migration-side border fault to accommodate a thick submarine package of sediments, including coarse (permeable) continental sediments that can act as source rock; (2) rising asthenosphere beneath the thinned lithosphere and crust, resulting in elevated temperatures in these overlying sediments that are favourable for leaching metals from the source rock; (3) the deposition of organic-rich sediments that form the host rock at shallower burial depths and lower temperatures; and (4) the generation of smaller faults that cut the major basin created by the border fault and provide additional pathways for focused fluid flow from source to host rock. Wide rifts with rift migration can have similarly favourable configurations, but these occur less frequently and less potential source rock is produced, thereby limiting potential metal endowment. In simulations of narrow symmetric rifts, the conditions to form ore deposits are rarely fulfilled. Based on these insights, exploration programmes should prioritize the narrow margins formed in asymmetric rift systems, in particular regions within several tens of kilometres from the paleo-shoreline, where we predict the highest-value deposits to have formed

(D)rifting in the 21st century: key processes, natural hazards, and geo-resources

Rifting and continental break-up are major research topics within geosciences, and a thorough understanding of the processes involved as well as of the associated natural hazards and natural resources is of great importance to both science and society. As a result, a large body of knowledge is available in the literature, with most of this previous research being focused on tectonic and geodynamic processes and their links to the evolution of rift systems. We believe that the key task for researchers is to make our knowledge of rift systems available and applicable to face current and future societal challenges. In particular, we should embrace a system analysis approach and aim to apply our knowledge to better understand the links between rift processes, natural hazards, and the geo-resources that are of critical importance to realise the energy transition and a sustainable future. The aim of this paper is therefore to provide a first-order framework for such an approach by providing an up-to-date summary of rifting processes, hazards, and geo-resources, followed by an assessment of future challenges and opportunities for research. We address the varied terminology used to characterise rifting in the scientific literature, followed by a description of rifting processes with a focus on the impact of (1) rheology and stain rates, (2) inheritance in three dimensions, (3) magmatism, and (4) surface processes. Subsequently, we describe the considerable natural hazards that occur in rift settings, which are linked to (1) seismicity, (2) magmatism, and (3) mass wasting, and provide some insights into how the impacts of these hazards can be mitigated. Moreover, we classify and describe the geo-resources occurring in rift environments as (1) non-energy resources, (2) geo-energy resources, (3) water and soils, and (4) opportunities for geological storage. Finally, we discuss the main challenges for the future linked to the aforementioned themes and identify numerous opportunities for follow-up research and knowledge application. In particular, we see great potential in systematic knowledge transfer and collaboration between researchers, industry partners, and government bodies, which may be the key to future successes and advancements

Rift-inversion orogens are the place to be for natural hydrogen gas (H2) exploration

International audienceNaturally occurring hydrogen gas (H2) represents a potentially major source of clean energy. It has been relatively overlooked so far but has gained more attention recently. The most promising mechanism for large-scale generation of such natural H2 is the serpentinization of mantle material as it reacts with water while it is brought into the "serpentinization window" (i.e., T = 200-350˚C) during mantle exhumation. We study such serpentinization-related natural H2 generation during rifting and subsequent rift inversion by means of numerical geodynamic models. In these numerical models we trace how, when, and where mantle material enters the serpentinization window, as well as when active, large-scale faults penetrate exhumed mantle bodies allowing for water circulation and serpentinization to occur.Although serpentinization-related natural H2 generation is a phenomenon best known from magma-poor rifted margins and slow spreading ridges, we find that volumes of natural H2 generated during inversion may be up to 20 times higher than during rifting, due to the colder thermal regime in rift-inversion orogenic environments. Moreover, suitable reservoirs and seals required for natural H2 accumulation are readily available in rift-inversion orogens, whereas they may not be present when serpentinization occurs in rift or drift settings. Our model results thus provide a first-order motivation to turn to rift-inversion orogens, rather than rifts and rifted margins, for natural H2 exploration. These model-derived insights are supported by indications of natural H2 generation in rift-inversion orogens such as the Western Alps, Pyrenees, and Caucasus