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Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)

Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)
Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)

During continental rifting, strain and magmatism are believed to localize to narrow magmatic segments, while the rift margin is progressively abandoned. We integrate volcanological, geochemical, petrological and seismic data from the Ma’Alalta volcanic field (MVF) near the western margin of Afar, to show that the MVF is an active magmatic segment. Magmatism in MVF initiated with lava flows and large-volume, caldera-forming ignimbrites from a central edifice. However, the most recent magmatic activity shifted towards mafic lava fields, cinder cones and obsidian-rich silicic domes erupted from vents aligned NNW-SSE, defining a ~ 35-km-long magmatic segment. Along the same area, a NNW-SSE alignment of earthquakes was recorded by two local seismic networks (2005–2009 and 2011–2013). The geochemistry of the mafic rocks is similar to those of nearby axial volcanoes. Inferred magma storage depth from mineral geobarometry shows that a shallow, silicic chamber existed at ~ 5-km depth below the stratovolcano, while a stacked plumbing system with at least three magma storage levels between 9 and 24 km depth fed the recent basalts. We interpret the wide set of observations from the MVF as evidence that the area is an active magmatic segment, showing that localised axial extension can be heavily offset towards the rift margin.

Central volcano, Magma plumbing, Ma’Alalta volcanic field, Rift margin, Rift segment, Tectonic extension
0258-8900
1
Tortelli, Gianmaria
cc85fd6a-8800-413d-8a4d-7d5be239dc28
Gioncada, A.
498799a3-7cf3-469a-89cc-6bdf1c7deaac
Pagli, C.
f2ee8853-c513-419a-ad33-c457dad669ca
Rosi, M.
2ad2297f-69fe-4839-94fd-e9e17bc4ac3d
De Dosso, Laura
ef958f68-81ad-48bd-b889-32055b0bd6d5
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Tortelli, Gianmaria
cc85fd6a-8800-413d-8a4d-7d5be239dc28
Gioncada, A.
498799a3-7cf3-469a-89cc-6bdf1c7deaac
Pagli, C.
f2ee8853-c513-419a-ad33-c457dad669ca
Rosi, M.
2ad2297f-69fe-4839-94fd-e9e17bc4ac3d
De Dosso, Laura
ef958f68-81ad-48bd-b889-32055b0bd6d5
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65

Tortelli, Gianmaria, Gioncada, A., Pagli, C., Rosi, M., De Dosso, Laura and Keir, Derek (2021) Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia). Bulletin of Volcanology, 83 (6), 1, [38]. (doi:10.1007/s00445-021-01461-4).

Record type: Article

Abstract

During continental rifting, strain and magmatism are believed to localize to narrow magmatic segments, while the rift margin is progressively abandoned. We integrate volcanological, geochemical, petrological and seismic data from the Ma’Alalta volcanic field (MVF) near the western margin of Afar, to show that the MVF is an active magmatic segment. Magmatism in MVF initiated with lava flows and large-volume, caldera-forming ignimbrites from a central edifice. However, the most recent magmatic activity shifted towards mafic lava fields, cinder cones and obsidian-rich silicic domes erupted from vents aligned NNW-SSE, defining a ~ 35-km-long magmatic segment. Along the same area, a NNW-SSE alignment of earthquakes was recorded by two local seismic networks (2005–2009 and 2011–2013). The geochemistry of the mafic rocks is similar to those of nearby axial volcanoes. Inferred magma storage depth from mineral geobarometry shows that a shallow, silicic chamber existed at ~ 5-km depth below the stratovolcano, while a stacked plumbing system with at least three magma storage levels between 9 and 24 km depth fed the recent basalts. We interpret the wide set of observations from the MVF as evidence that the area is an active magmatic segment, showing that localised axial extension can be heavily offset towards the rift margin.

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More information

Published date: 19 May 2021
Keywords: Central volcano, Magma plumbing, Ma’Alalta volcanic field, Rift margin, Rift segment, Tectonic extension

Identifiers

Local EPrints ID: 449619
URI: http://eprints.soton.ac.uk/id/eprint/449619
ISSN: 0258-8900
PURE UUID: 006b1a90-ba6f-412c-9be7-532fbb920f34
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

Catalogue record

Date deposited: 09 Jun 2021 16:30
Last modified: 10 Jun 2021 01:42

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Contributors

Author: Gianmaria Tortelli
Author: A. Gioncada
Author: C. Pagli
Author: M. Rosi
Author: Laura De Dosso
Author: Derek Keir ORCID iD

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