1,2,3,- 1School of Geography, Earth and Environmental Sciences, University of Birmingham, United Kingdom (m.capriolo@bham.ac.uk)
- 2Department of Biological, Geological and Environmental Sciences, University of Bologna, Italy
- 3Njord Centre, Departments of Physics and Geosciences, University of Oslo, Norway
- 4Lithosphere Fluid Research Laboratory, Institute of Geography and Earth Sciences, Eötvös Loránd University, Budapest, Hungary
- 5Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington DC, USA
- 6Department of Geosciences, University of Oslo, Norway
Interactions between magmas and organic matter from host sedimentary rocks may lead to ore mineralization [1], hydrocarbon cracking [2] and thermogenic gas emissions [3], potentially disrupting the global carbon cycle. We reconstructed magma–hydrocarbon interaction processes by studying basaltic melts intruding bitumen- and oil-bearing sandstones in a continental rift setting, combining detailed field observations with geochemical analyses, melt and fluid inclusions study [4]. Our case study is Bile Island in the Oslo Fjord (Norway), where Upper Silurian sandstones are crosscut by a pyrobitumen-bearing sill and several dykes, which date back to the Oslo Rift activity, the northernmost branch of the 300 Myr-old Skagerrak Large Igneous Province [5]. These intrusions represent the magma plumbing system of an adjacent basaltic volcano from the earliest phase of the Oslo Rift, and the sedimentary succession in this area contains oil and bitumen mainly sourced from Cambrian–Ordovician organic-rich shales. Our multi-technique approach characterized the transformation of bitumen and oil into pyrobitumen along with abundant methane (CH4) and ethane (C2H6) emissions. Our geochemical dataset described element exchange and mass transfer between melts, fluids and host rocks, from magmatic to hydrothermal stages, depicting a scenario with magmatic intrusions of a large mafic complex intersecting a pre-existing petroleum system. Bile Island yields an extraordinary record, where magmatic and sedimentary carbon is synchronously released via the same volcanic vent(s), providing a viable explanation for methane emissions in volcanic areas and offering a new paradigm for degassing in the context of Large Igneous Provinces.
[1] Hoggard et al. (2020), Nat. Geosci. 13, 504–510.
[2] Senger et al. (2017), First Break 35, 47–56.
[3] Svensen et al. (2004), Nature 429, 542–545.
[4] Capriolo et al. (2026), J. Geol. Soc. https://doi.org/10.1144/jgs2025-094.
[5] Torsvik et al. (2008), Earth Planet. Sci. Lett. 267, 444–452.
How to cite: Capriolo, M., Callegaro, S., Aradi, L., Ackerson, M., Karlsen, D., and Svensen, H.: Magmatic and sedimentary carbon release from a mafic complex intersecting a petroleum system in the Oslo Rift (Norway), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13564, https://doi.org/10.5194/egusphere-egu26-13564, 2026.
