EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Voluminous crustal degassing and immiscible sulfide genesis caused by magma-shale interaction in Large Igneous Provinces

Frances Deegan1,2, Jean Bédard3, Valentin Troll1,2, Keith Dewing4, Harri Geiger1, Steve Grasby4, Valeria Misiti2, and Carmela Freda2
Frances Deegan et al.
  • 1Department of Earth Sciences, Uppsala University, Uppsala, Sweden (
  • 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy
  • 3Geological Survey of Canada (GSC), GSC-Québec, Québec, Canada
  • 4Geological Survey of Canada (GSC), GSC-Calgary, Calgary, Canada

Large Igneous Province (LIP) activity is hypothesized to impact global volatile cycles causing climate changes and environmental crises deleterious to the biosphere. Recent work suggests that the potential of LIPs to impact climate is magnified where they intrude organic-rich (i.e. shale-bearing) sedimentary basins. However, the chemical and degassing dynamics of magma-shale interaction are not well understood. Here we present the first experimental simulations of disequilibrium interaction between LIP magma and carbonaceous shale during upper crustal sill intrusions in the Canadian High Arctic LIP (HALIP), the latter of which were co-eval with oceanic anoxic event 1a. Experiments show that magma-shale interaction results in intense syn-magmatic degassing and simultaneous precipitation of sulfide droplets at the ablation interface. Magma-shale interaction on a basin-scale can thus generate substantial amounts of climate-active H-C-S volatiles, while the presence of strongly reducing volatiles may also increase the likelihood of magma to segregate a sulfide melt. These findings have fundamental consequences for our understanding of both large-scale Earth outgassing and metal prospectivity in sediment-hosted LIPs.

How to cite: Deegan, F., Bédard, J., Troll, V., Dewing, K., Geiger, H., Grasby, S., Misiti, V., and Freda, C.: Voluminous crustal degassing and immiscible sulfide genesis caused by magma-shale interaction in Large Igneous Provinces, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14578,, 2020

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