Reactive Transport Modelling of Ore Formation in Sedimentary Basins

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Sediment-hosted ore deposits are major resources for base metals like Zn, Pb, Cu and many other mass and critical metals (e.g. In, Ge, Ga) that are of strategic importance for the transition towards a carbon-neutral society. Ore metal enrichment in basin-scale hydrothermal systems results from a perfect convergence of chemical and physical processes on different temporal and spatial scales, and these systems can only be quantitatively understood by observations and studies beyond the deposit scale. Numerical process models have the potential to identify first-order controls on ore formation and provide physical and chemical constraints on the feasibility and efficiency of hydrothermal systems to generate world-class deposits, which may help guiding future exploration. Major advances in modelling in recent years have either focused on thermodynamic-geochemical fluid-rock interaction or on physical hydrology, while full reactive transport modelling of hydrothermal systems was limited to simplified systems. In the proposed project, we will develop and apply a reactive transport model for ore formation in sedimentary basins, using the geochemical model GEMS3 and the fluid flow model CSMP++. The resulting fully coupled numerical model will be able to 1) capture the interplay between the chemical and physical processes relevant for metal mobilization, transport and precipitation, and 2) constrain the temporal and spatial scales required for metal enrichment to economic grades. With this model, we will quantitatively investigate the respective roles of key parameters like fluid salinity, oxidation state, pH, metal and sulfur availability, basin-scale heat flux, topography, basin strata, pore space and permeable fluid pathways on the dynamics of ore metals enrichment. The project will begin with simple generic settings and then successively increase the geological complexity. The geochemical model GEMS3 can incorporate internally consistent databases for the main rock-forming and ore elements provided by a global-regression approach. The fluid flow model CSMP++ can incorporate geologically realistic constraints on heat flux, rock units and faults provided by a geodynamic model. We will mainly address first-order processes forming sediment-hosted Pb-Zn deposits, but the model will provide much wider potential for applications to other hydrothermal systems. The project will contribute to the overarching goal of the priority programme DOME by addressing key mechanisms of ore formation in a trans-disciplinary approach, where we advance numerical methods that use fluid and rock properties determined by experimental and analytical data and aim at explaining the key features of Pb-Zn deposits. The collaborative project has evolved from the combination of two modelling projects of the first phase of the DOME programme and will have great potential for further collaborations with projects addressing sediment-hosted and other low-temperature ore deposits.