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The composition of gas emissions at Petite Terre (Mayotte, Comoros): inference on magmatic fingerprints
Author(s)
Language
English
Obiettivo Specifico
1V. Storia eruttiva
2V. Struttura e sistema di alimentazione dei vulcani
4V. Processi pre-eruttivi
5V. Processi eruttivi e post-eruttivi
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
s2/354 (2022)
ISSN
1631-0713
Pages (printed)
275-298
Issued date
2022
Abstract
The Comoros archipelago is an active geodynamic region located in theMozambique Channel
between East continental Africa andMadagascar. The archipelago results from intra-plate volcanism,
the most recent eruptions having occurred on the youngest island of Grande Comore and on the
oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of
the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent
volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite
Terre Island,where twomain and persistent gas seep areas are present (Airport Beach, namely BAS,
and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore;
3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km
offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at
characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential
link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine
activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared
with older datasets acquired between 2005 and 2016 from different research teams. The relation between
3He/4He and 13C-CO2 shows a clear magmatic origin for Mayotte bubbling gases, while the
variable proportions and isotopic signature of CH4 is related to the occurrence of both biogenic and
abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibriumtemperature
steadily decreases since 2018. The increased knowledge on the gas-geochemistry
at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring
programs
between East continental Africa andMadagascar. The archipelago results from intra-plate volcanism,
the most recent eruptions having occurred on the youngest island of Grande Comore and on the
oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of
the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent
volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite
Terre Island,where twomain and persistent gas seep areas are present (Airport Beach, namely BAS,
and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore;
3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km
offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at
characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential
link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine
activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared
with older datasets acquired between 2005 and 2016 from different research teams. The relation between
3He/4He and 13C-CO2 shows a clear magmatic origin for Mayotte bubbling gases, while the
variable proportions and isotopic signature of CH4 is related to the occurrence of both biogenic and
abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibriumtemperature
steadily decreases since 2018. The increased knowledge on the gas-geochemistry
at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring
programs
Type
article
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