Open AccessEvidence for an Active, Transcrustal Magma System in the Last 60 ka and Eruptive Degassing Budget (H 2 O, CO 2 , S, F, Cl, Br): The Case of Dominica
Author(s) -
d'Augustin T.,
BalconeBoissard H.,
Boudon G.,
Martel C.,
Deloule E.,
Bürckel P.
Publication year - 2020
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2020gc009050
Subject(s) - geology , magma , volcano , geochemistry , outgassing , melt inclusions , magma chamber , atmosphere (unit) , igneous rock , petrology , earth science , chemistry , thermodynamics , physics , organic chemistry
The Morne Trois Pitons‐Micotrin volcanic complex on the island of Dominica (Lesser Antilles) emitted a series of plinian eruptions between 18 and 9 ka BP. We studied it to constrain magma storage conditions and volatile degassing balances, by comparison with the three previous ignimbrites (~60–24 ka BP). Volatile concentrations in glass inclusions and mineral‐melt thermobarometry indicate storage at ≤200 MPa (~6–8 km) and 860–880°C. The magmas feeding these plinian eruptions were stored at a shallower depth than those that older ignimbrites from the same volcanic complex and stored at ~16 km. Close magma composition and similar halogen ratios, however, suggest a common source for the magmas feeding both the plinian eruptions and the ignimbrites. The large eruptive fluxes of F, Cl, and Br to the atmosphere (up to 1.4–2.8 × 10 −1 Mt/km 3 , 1.5–4.0 Mt/km 3 , and 2–4 × 10 −2 Mt/km 3 , respectively), estimated by the petrological method, support the potentially important role of volcanic halogens in modifying the chemistry of the atmosphere, though Cl is underestimated here because of buffering in a fluid phase. The behavior of S, potentially partitioned in the same fluid phase, prevents here the calculation of an eruptive outgassing budget.