V007-0006
Sediment-hosted metal deposits and the billion-year stability of cratonic lithosphere
Tuesday, 8 December 2020
Poster
Mark Hoggard1,2, Karol Czarnota3, Fred Richards4, David Huston3, Lynton Jaques5 and Siavash Ghelichkhan6, (1)Harvard University, Department of Earth and Planetary Sciences, Cambridge, MA, United States, (2)Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY, United States, (3)Geoscience Australia, Canberra, ACT, Australia, (4)Imperial College London, Earth Science and Engineering, London, United Kingdom, (5)Australian National University, Research School of Earth Sciences, Canberra, Australia, (6)Australian National University, Research School of Earth Sciences, Canberra, ACT, Australia
Abstract:
Approximately 70% of known lead, 55% of zinc and 20% of copper has been deposited between 2 Ga and recent by low-temperature hydrothermal circulation in shallow sedimentary basins. Some of these deposits contain more than 10 million tonnes of metal bound up in comparatively high-grade ores, making them desirable targets for mineral exploration. Despite 150 years of research, however, the relationship between deposit locations and local geological structure is enigmatic and there remains no accurate technique for predicting their distribution at continental scales.
Here, we show that modern surface wave tomography and recent parameterisations for anelasticity at seismic frequencies can be used to map lithospheric structure, and that large sediment-hosted base metal deposits occur exclusively along the edges of thick lithosphere. Approximately 90% of the world's sediment-hosted copper, lead and zinc resources lie within 200 km of these boundaries, including all giant deposits (>10 Mt of metal). This important observation implies long-term lithospheric edge stability and a genetic link between deep Earth processes and near-surface hydrothermal mineral systems. We show that rifting of thick, chemically depleted cratonic lithosphere provides the optimal conditions for sediment-hosted mineral systems, due to both larger amplitudes of syn-rift subsidence and lower basal heatflow. Our new maps provide an unprecedented global means to identify fertile regions for targeted mineral exploration.
