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Revisiting Tajao: using banded pumices to untangle magma dynamics in an intra-cycle eruption from the Las Cañadas volcano, Tenerife (Canary Islands)

Diego González-García1,2, Maurizio Petrelli3, Helena Albert4, Renat Almeev1, Olaya Dorado5, Joan Marti6, François Holtz1

  • Affiliations: 1Institute of Earth System Sciences, Leibniz Universität Hannover, Germany; 2Department of Mineralogy and Petrology, Universidad Complutense de Madrid, Spain; 3Department of Physics and Geology, Università degli Studi di Perugia, Italy; 4Department of Mineralogy, Petrology and Applied Geology, Universitat de Barcelona, Spain; 5GEO3BCN, CSIC, Barcelona, Spain; 6IDAEA, CSIC, Barcelona, Spain

  • Presentation type: Talk

  • Presentation time: Monday 14:45 - 15:00, Room R280

  • Programme No: 1.7.7

  • Theme 1 > Session 7

Abstract

Banded pumices are widespread among explosive eruptions and are frequently regarded as evidence of pre- and syn-eruptive magma interactions in the plumbing system. Therefore, their study provides detailed information on the magma dynamics preceding and/or triggering eruptions. We present a petrological and geochemical study of banded pumices from the 320 ka Tajao eruption, a small (~3 km3 DRE), intra-cycle event belonging to the Diego Hernandez Formation (DHF), Las Cañadas edifice (Tenerife, Canary Islands). Although the Tajao banded pumices resemble those from other DHF ignimbrite bodies (e.g. El Abrigo [1]), major and trace element glass and mineral chemistry suggest different magma dynamics and end-member compositions. Compared to El Abrigo banded pumices, Tajao groundmass glass chemistry is more complex, with a trimodal distribution and more restricted composition range. Their trace element concentrations suggest a lesser contribution of evolved feldspar-rich magma mushes. In contrast, mafic glasses are tephritic-phonotephritic in composition and suggest the involvement of a Cpx-Krs-Pl bearing component, similar to El Abrigo mafic endmember. Complex mixing and mingling textures between mafic and silicic melts are ubiquitous. Furthermore, thermobarometric estimates on zoned Na-rich pyroxenes indicate significant heating of the phonolitic reservoir before the eruption. Our results expand previous work [2] and improve our knowledge on the long-term evolution of the DHF shallow phonolitic reservoir, which eventually led to the large-volume El Abrigo eruption at ca. 170 ka, the last caldera-forming eruption on Tenerife. [1] González-García et al. (2022). J. Petrol. 63(3), egac009   [2] Wolff, J. A. (1985). Geol. Mag. 122(6), 623--640