Precise dating of large flank collapses by single-grain 40Ar/39Ar on pyroclastic deposits from the example of Flores Island (Azores) - Laboratoire des Sciences du Climat et de l’Environnement Accéder directement au contenu
Article Dans Une Revue Scientific Reports Année : 2024

Precise dating of large flank collapses by single-grain 40Ar/39Ar on pyroclastic deposits from the example of Flores Island (Azores)

A. Hildenbrand
F O Marques
  • Fonction : Auteur
A. Pereira
  • Fonction : Auteur
F. Hevia-Cruz
  • Fonction : Auteur

Résumé

Abstract Large-scale flank collapses are one of the main hazards associated with the evolution of volcanic islands. Precisely dating such events is critical to evaluate the frequency of destabilization episodes and further assess the triggering mechanism(s) associated with internal and/or external factors, such as volcano dynamics, regional tectonics, and global paleoclimatic changes. Here, we constrain the age of a pumice-rich pyroclastic deposit exposed on the eastern flank of Flores Island (Azores), which we interpret as a co-blast deposit generated by a major flank collapse that destroyed the whole western flank of the former volcanic edifice. Twelve single-grain 40 Ar/ 39 Ar analyses, performed on 250–500 µm anorthoclase feldspars (mean K/Ca close to 5) with our high-sensitivity multi-collector NGX mass spectrometer, provide a robust weighted mean age of 1.32 ± 0.01 Ma for this eruption. This new age is consistent with previous K/Ar data bracketing the flank collapse between 1.30 ± 0.04 and 1.18 ± 0.09 Ma, and indicates that this event occurred at the end of the main construction phase of the volcano. The explosion produced pumice-rich layers preceded by a lahar as attested by a polygenetic mudflow deposit underlying the dated deposit. From the geochemistry of lavas erupted just before and after the collapse, we speculate upon the possible role of magmatic processes on flank destabilization. We propose a first hypothesis where differentiation in a shallow magma reservoir could have favored edifice inflation, ground shaking, and flank failure, triggering a decompression-induced violent eruption. Overall, our study shows that high-sensitivity mass spectrometers have now reached analytical performances allowing to measure precisely and accurately ages on relatively small and moderately K-rich single feldspars, which is of the utmost importance for dating heterogeneous blasts and tephra deposits that may have been induced by large-scale flank collapses during the late Quaternary.
Fichier principal
Vignette du fichier
s41598-024-62583-1.pdf (2.45 Mo) Télécharger le fichier
Origine Fichiers éditeurs autorisés sur une archive ouverte

Dates et versions

hal-04597540 , version 1 (03-06-2024)

Identifiants

Citer

A. Hildenbrand, F O Marques, A. Pereira, S. Nomade, F. Hevia-Cruz. Precise dating of large flank collapses by single-grain 40Ar/39Ar on pyroclastic deposits from the example of Flores Island (Azores). Scientific Reports, 2024, 14 (1), pp.11905. ⟨10.1038/s41598-024-62583-1⟩. ⟨hal-04597540⟩
0 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Mastodon Facebook X LinkedIn More