Oxygen isotopes in 2021 La Palma lavas reveal pre-eruptive magma storage and primitive mantle values
- 1Department of Earth Sciences, Uppsala University, Uppsala, Sweden (frances.deegan@geo.uu.se)
- 2Department of Earth Sciences, University of Oregon, Eugene, Oregon, USA (bindeman@uoregon.edu)
- 3Department of Geological Sciences, University of Cape Town, Cape Town, South Africa (Chris.Harris@uct.ac.za)
- 4Geochemistry, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA (jmdday@ucsd.edu)
- 5Departamento de Mineralogia, Petrologia i Geologia Aplicada, University of Barcelona, Barcelona, Spain (halbert@ub.edu)
- 6Institute of Earth and Environmental Sciences, University of Freiburg, Freiburg im Breisgau, Germany (harri.geiger@minpet.uni-freiburg.de)
- 7Instituto de Estudios Ambientales y Recursos Naturales (i-UNAT), University of Las Palmas de Gran Canaria (ULPGC), Las Palmas de Gran Canaria, Spain (jcarracedo@proyinves.ulpgc.es)
- 8IPNA, CSIC, La Laguna, Tenerife, Spain (vsjavaloyes@gmail.com)
Magma production, storage, and migration beneath volcanic ocean islands has been a matter of controversy and a multitude of methods are currently used to unravel magma evolution, storage and migration processes. Here we report on a temporal sequence of lava samples1, 2 spanning the entirety of the 2021 La Palma eruption (19/09 to 13/12) for which time-series seismic information is also available. Based on the seismic data, initial tephrite lavas were likely drawn from a storage level at or just above the Moho (10-15 km depth), with increasing contributions from a deeper reservoir (>20 km depth) that delivered more primitive basanite lava as the eruption progressed. Early tephrite lava compositions changed rapidly during the first few weeks of the eruption and show significant oxygen isotopic variability (δ18O = +4.9 to 5.8‰), with some samples requiring a low-δ18O component. Later basanite lavas are compositionally less variable after day 20 of the eruption and show a narrower range in oxygen isotopes (δ18O = +5.3 to 5.7‰), close to Atlantic MORB values and similar to values from other historical eruptions and to earlier values recorded from the Cumbre Vieja volcanic system. The larger variability in δ18O in the early lavas is associated with significantly more radiogenic 187Os/188Os and the presence of amphibole and frequent gabbroic micro-xenoliths. Interaction with high-T altered Jurassic oceanic crustal gabbros and basalts with high-time-integrated Re/Os and variable δ18O could be an explanation for the initially wider variations in oxygen isotopes. This is in line with the seismic evidence that indicates the early lavas had been stored at (sub-)Moho levels within the Jurassic oceanic crust at ca. 8-15 km below the island prior to eruption. Later erupted magmas derive from a deeper, upper mantle storage level (>20 km depth) and have had little to no interaction with the igneous and sedimentary portions of the Mesozoic ocean crust, thus providing a useful estimate of primitive mantle δ18O values for the Western Canary Islands.
1Carracedo J.C., Troll V.R., Day J.M.D., Geiger H., Aulinas Junca, M., Soler V., Deegan F.M., Perez-Torrado F.J., Gisbert G., Gazel E., Rodríguez-González, A., and Albert H. (2022) The 2021 eruption of the Cumbre Vieja Volcanic Ridge on La Palma, Canary Islands. Geology Today 38: 94-107.
2Day J.M.D., Troll V.R., Aulinas M., Deegan F.M., Geiger H., Carracedo J.C., Pinto G.G., and Perez-Torrado F.J. (2022) Mantle source characteristics and magmatic processes during the 2021 La Palma eruption. Earth and Planetary Science Letters 597: 117793.
How to cite: Troll, V., Deegan, F., Bindeman, I., Harris, C., Day, J., Aulinas, M., Geiger, H., Perez Torrado, F., Carracedo, J. C., Soler, V., Pinto, G., and Albert, H.: Oxygen isotopes in 2021 La Palma lavas reveal pre-eruptive magma storage and primitive mantle values, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6518, https://doi.org/10.5194/egusphere-egu23-6518, 2023.
