Controls of magma chamber zonation on eruption dynamics and deposits stratigraphy: The case of El Palomar fallout succession (Tenerife, Canary Islands)
Résumé
Anticipating volcanic eruptions at central volcanoes require knowing how magma chambers prepare for new eruptions. Pre-eruptive processes that occur in such magma chambers are recorded in the products of these eruptions, so their characterisation in terms of magma composition and physics offers the clues to understand past eruptions and predict future ones. Here, we study the very well preserved pyroclastic succession of El Palomar Member (712 ± 41 ka), in Las Cañadas caldera, Teide, Canary Islands. This deposit resulted from a single explosive eruption of a phonolitic magma that started with a sustained eruption column (sub-plinian or plinian) that formed a massive, 40 m thick non-welded fallout deposit, progressively changing into a lower intensity fire fountain that deposited a 25 m thick fallout succession of non-welded to strongly welded pumices. Stratigraphic and petrological data suggest that this eruption was related to a thermally-compositionally zoned and relatively shallow magma chamber in which the arrival of a hotter and more mafic magma rapidly triggered the eruption. The studied deposit shows how this zoned structure was maintained during the whole process, which allows one to reconstruct what happened during the eruption. Comparison of this eruption with the current situation at Teide volcano alerts on the potential rapid preparation for new eruptions in the case that sufficient phonolitic magma was available in the shallow plumbing system of this active volcano if new inputs of deeper magma take place.
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