EGU22-12452
https://doi.org/10.5194/egusphere-egu22-12452
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Mantle-derived xenoliths from the Cumbre Vieja 2021 lava flows: insights on the composition of the lithosphere beneath La Palma (Canary Islands)

Theodoros Ntaflos1, Federico Casetta1, Andrès Sandoval-Velasquez2, Andrea Luca Rizzo3, Alessandro Aiuppa2, Mar Alonso4, Eleazar Padron4, Matthew Pankhurst4, and Nemesio Perez4
Theodoros Ntaflos et al.
  • 1University of Vienna, Dept. für Lithosphärenforschung, UZA II, Vienna, Austria
  • 2DiSTeM, Università di Palermo, Via Archirafi 36, 90123 Palermo, Italy
  • 3Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Milano, Via Alfonso Corti 12, 20133 Milano, Italy
  • 4Instituto Volcanológico de Canarias (INVOLCAN), 38320 San Cristóbal de La Laguna, Tenerife, Canary Islands

Small, cm-sized ultramafic xenoliths have been reported from the opening phase of the 2021 eruption at Cumbre Vieja, where clinopyroxene aggregates, sometimes amphibole, olivine and/or magnetite-bearing (Pankhurst et al., 2021), likely represent early fractionation products and/or relics of mush-like systems located beneath the volcanic edifice.

Detailed sampling of the lavas produced during the intermediate-late eruptive phase (November 9th) revealed the existence, in the massive portion of the flows, of a 1 cm sized dunitic xenolith with protogranular to partly recrystallized texture. The internal portion of the xenolith is composed of Fo88-89 olivine (0.33-0.34 wt% NiO), Ti-Al-poor clinopyroxene (Mg# = 87-92; Al2O3 <1.7 wt%; TiO2 <0.5 wt%), Cr-rich spinel and rare Mg-rich orthopyroxene (Mg# = 88-91; Al2O3 from 0.4-0.5 to 1.7-1.9 wt%). Textural and chemical data (Fe-Mg distribution) indicate that olivine, orthopyroxene and clinopyroxene are not far from equilibrium. Preliminary calculations show that the equilibrium T recorded by the xenolith ranges from 950 to 1070°C, with good consistency between results obtained from olivine-spinel and orthopyroxene-clinopyroxene pairs. Silica oversaturated interstitial glasses (SiO2= 67 wt%) were found in the partly recrystallized part of the xenolith.

Part of the coarse-grained xenolith forms a corona of fine-grained and worm-like association of, olivine, orthopyroxene, clinopyroxene and spinel. Both parts are surrounded by a continuous narrow external zone consisting of Ti-magnetite and sub-euhedral greenish Ti-augite, which is in contact with the host basalt. The composition of olivine and orthopyroxene in the corona keeps getting more Fe-rich towards the external zone whereas the clinopyroxene changes gradually from Ti-free to Ti-bearing diopside.

The small xenolith recovered from the November 9th lava flow is apparently a mantle-derived xenolith similar to those from the Duraznero 1949 eruption described by Klügel (1998), and those from the San Antonio 1677 eruption described by Neumann & Wulff-Pedersen, 1997.  On the way to surface, the mantle xenolith likely reacted with basaltic melts to form the first corona. These processes presumably took place in depths between 0.10-0.12 GPa as can be inferred by the presence of silica oversaturated glasses (Neumann & Wulff-Pedersen, 1997). The external zone probably formed as the result of a late-stage stagnation of the host magma at sub-crustal depths, as suggested by the compositional similarity between the clinopyroxene-spinel assemblage and the phenocrysts in the matrix.

               

Klüger, A. (1998). Reactions between mantle xenoliths and host magma beneath La Palma (Canary Islands: constraints on magma ascent rates and crustal reservoirs. Contrib Mineral Petrol 131:238-257

Neumann, E.-R. and E. Wulff-Pedersen (1997). The Origin of Highly Silicic Glass in Mantle Xenoliths from the Canary Island. Journal of Petrology 32: 1515-1539

Pankhurst, M. J., et al., (2021). Petrology of the opening eruptive phase of the 2021 Cumbre Vieja eruption, La Palma, Canary Islands. Volcanica: 5(1), 1–10

How to cite: Ntaflos, T., Casetta, F., Sandoval-Velasquez, A., Rizzo, A. L., Aiuppa, A., Alonso, M., Padron, E., Pankhurst, M., and Perez, N.: Mantle-derived xenoliths from the Cumbre Vieja 2021 lava flows: insights on the composition of the lithosphere beneath La Palma (Canary Islands), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12452, https://doi.org/10.5194/egusphere-egu22-12452, 2022.