| Title: |
Magma Paths of the Karthala and La Grille Volcanoes (Grande Comore) Revisited: New Evidence From Geomorphology and Geochemistry |
| Authors: |
Lötter, Francois, J. P.; Villeneuve, Nicolas; Di Muro, Andréa; Lenhardt, Nils; Michon, Laurent; Besson, Pascale; Soulé, Hamid |
| Contributors: |
Laboratoire GéoSciences Réunion (LGSR); Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris); Institut de Physique du Globe de Paris (IPG Paris); Observatoire Volcanologique du Piton de la Fournaise (OVPF); Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE); École normale supérieure de Lyon (ENS de Lyon); Université de Lyon-Université de Lyon-Université Claude Bernard Lyon 1 (UCBL); Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS); University of Pretoria South Africa (UP); Laboratoire Magmas et Volcans (LMV); Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Clermont Auvergne (UCA); Institut de Physique du Globe de Paris (IPGP - UMR_7154); Institut national des sciences de l'Univers (INSU - CNRS)-Institut National de l'Information Géographique et Forestière IGN (IGN)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité); Centre national de documentation et de recherche scientifique (CNDRS) |
| Source: |
EISSN: 1525-2027 ; Geochemistry, Geophysics, Geosystems ; https://uca.hal.science/hal-05558296 ; Geochemistry, Geophysics, Geosystems, 2026, 27, ⟨10.1029/2025GC012529⟩ |
| Publisher Information: |
CCSD; AGU and the Geochemical Society |
| Publication Year: |
2026 |
| Collection: |
Université Jean Monnet – Saint-Etienne: HAL |
| Subject Terms: |
[SDU]Sciences of the Universe [physics] |
| Description: |
International audience ; Grande Comore, the westernmost island within the Madagascar Comoros Volcanic (MCV) chain, hosts two juxtaposed basaltic volcanoes, Karthala and La Grille, with contrasting lava geochemical signatures and eruption frequencies. Their formation and dynamics have been explained either by a mantle plume or, more recently, as part of a transtensional volcano-tectonic system. Understanding their individual development is key to resolving persistent geodynamic contradictions within the Comoros and improving volcanic hazard assessment. We integrate the morphology and spatial distribution of scoria cones with a new database of lava, and, for the first time, tephra compositions to constrain magma pathways. We classify cone-dense regions into four main clusters (SGC, KAR, CGC, and LAG) and four sub-clusters (KARa, KARb, KARc, and LAGa). Within Karthala, cone size weakly correlates with primitive mafic magma compositions, whereas no such relationship occurs at La Grille clusters. This indicates a developed, shallow plumbing system beneath Karthala and its absence beneath La Grille. Cone base orientation reveals that Karthala and La Grille volcanism is influenced by regional rifting, but only Karthala is influenced by edifice loading. Edifice-induced compositional filtering promotes lateral migration of primitive magmas and vertical ascent of evolved magmas, while regionally controlled rift zones channel evolved magmas to the center of the island. Recent eruption convergence/resurgence cycles suggest that future eruptions at Karthala will likely be constrained to the edifice of Karthala while La Grille's rare eruptions have only tectonic triggers. Active areas on Grande Comore are thus well constrained and more widespread than previously thought. Plain Language Summary Grande Comore, a volcanic island in the Mozambique Channel, consists of two volcanoes: Karthala, which erupts frequently, and La Grille, which erupts infrequently. These volcanoes are additionally contrasted in compositional-and ... |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| DOI: |
10.1029/2025GC012529 |
| Availability: |
https://uca.hal.science/hal-05558296; https://uca.hal.science/hal-05558296v1/document; https://uca.hal.science/hal-05558296v1/file/2026-G3-Lotter.pdf; https://doi.org/10.1029/2025GC012529 |
| Rights: |
https://creativecommons.org/licenses/by/4.0/ ; info:eu-repo/semantics/OpenAccess |
| Accession Number: |
edsbas.87D072C2 |
| Database: |
BASE |