From melt- to crystal-rich magmatic systems during rift localization: insights from mineral chemistry in Central Afar (Ethiopia)
From melt- to crystal-rich magmatic systems during rift localization: insights from mineral chemistry in Central Afar (Ethiopia)
Magmatism plays a key role in accommodating and localizing extension during continental breakup. However, how the crustal magmatic systems evolve at the continental-ocean transition is poorly understood. We address these questions by studying the evolution of the magmatic system in the rift of Central Afar (Ethiopia), currently marking the transition from continental rifting to oceanic spreading. We focus on the voluminous and widespread Upper Stratoid Series (2.6–1.1 Ma) and the following Central Afar Gulf Series (1.1–0.6 Ma), the latter corresponding to localization of volcanism in narrow magmatic segments. We carried out the first systematic study of major and trace element mineral chemistry for these two Series and integrated it with geothermobarometry estimates and geochemical modeling, to reconstruct the evolution of the magmatic system architecture during rift localization. The Upper Stratoid magmas evolved by fractional crystallization in a melt-rich, moderately zoned, middle-lower crustal (10–18 km) magmatic system, from where they rose directly to the surface. Polybaric plagioclase convection and dissolution of a plagioclase-rich crystal mush is recorded in the phenocryst texture and chemistry. The Central Afar Gulf magmas evolved at similar depth in a more complex and dynamic storage system, with magma rising and mixing through multiple, relatively small, crystal-rich and interconnected reservoirs. Our study documents the transition during the continental breakup, from an overall stable and melt-rich magmatic system feeding the voluminous and homogeneous Upper Stratoid eruptions to a more dynamic, interconnected and crystal-rich situation feeding small-volume eruption while the rift localizes.
Afar, Continental breakup, Magma plumbing system, Plagioclase, Rift evolution, Stratoid series
Tortelli, Gianmaria
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Gioncada, A.
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Pagli, C.
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Braschi, E.
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Gebru, E.F.
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Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Tortelli, Gianmaria
cc85fd6a-8800-413d-8a4d-7d5be239dc28
Gioncada, A.
ba2a4a16-e2f6-45a6-8655-72ccdbdfb731
Pagli, C.
290edb22-712b-4563-a868-af4c21fdb6b0
Braschi, E.
c27793db-0d39-4eca-ac98-ead35b0c9a22
Gebru, E.F.
71d492b8-a8ee-48bd-bf04-fef7d95a888b
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Tortelli, Gianmaria, Gioncada, A., Pagli, C., Braschi, E., Gebru, E.F. and Keir, D.
(2024)
From melt- to crystal-rich magmatic systems during rift localization: insights from mineral chemistry in Central Afar (Ethiopia).
Contributions to Mineralogy and Petrology, 179 (10), [87].
(doi:10.1007/s00410-024-02164-7).
Abstract
Magmatism plays a key role in accommodating and localizing extension during continental breakup. However, how the crustal magmatic systems evolve at the continental-ocean transition is poorly understood. We address these questions by studying the evolution of the magmatic system in the rift of Central Afar (Ethiopia), currently marking the transition from continental rifting to oceanic spreading. We focus on the voluminous and widespread Upper Stratoid Series (2.6–1.1 Ma) and the following Central Afar Gulf Series (1.1–0.6 Ma), the latter corresponding to localization of volcanism in narrow magmatic segments. We carried out the first systematic study of major and trace element mineral chemistry for these two Series and integrated it with geothermobarometry estimates and geochemical modeling, to reconstruct the evolution of the magmatic system architecture during rift localization. The Upper Stratoid magmas evolved by fractional crystallization in a melt-rich, moderately zoned, middle-lower crustal (10–18 km) magmatic system, from where they rose directly to the surface. Polybaric plagioclase convection and dissolution of a plagioclase-rich crystal mush is recorded in the phenocryst texture and chemistry. The Central Afar Gulf magmas evolved at similar depth in a more complex and dynamic storage system, with magma rising and mixing through multiple, relatively small, crystal-rich and interconnected reservoirs. Our study documents the transition during the continental breakup, from an overall stable and melt-rich magmatic system feeding the voluminous and homogeneous Upper Stratoid eruptions to a more dynamic, interconnected and crystal-rich situation feeding small-volume eruption while the rift localizes.
Text
s00410-024-02164-7
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Accepted/In Press date: 16 August 2024
e-pub ahead of print date: 5 September 2024
Keywords:
Afar, Continental breakup, Magma plumbing system, Plagioclase, Rift evolution, Stratoid series
Identifiers
Local EPrints ID: 495371
URI: http://eprints.soton.ac.uk/id/eprint/495371
ISSN: 0010-7999
PURE UUID: 95e05aec-9b15-4038-8cd2-b873f333adf4
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Date deposited: 12 Nov 2024 17:32
Last modified: 13 Nov 2024 02:44
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Contributors
Author:
Gianmaria Tortelli
Author:
A. Gioncada
Author:
C. Pagli
Author:
E. Braschi
Author:
E.F. Gebru
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