@article{fdi:010088218,
  title = {{M}agma storage and degassing beneath the youngest volcanoes of the {M}assif {C}entral ({F}rance) : {L}essons for the monitoring of a dormant volcanic province},
  author = {{B}oudoire, {G}. and {P}asdeloup, {G}. and {S}chiavi, {F}ederica and {C}luzel, {N}. and {R}afflin, {V}. and {G}rassa, {F}. and {G}iuffrida, {G}. and {L}iuzzo, {M}. and {H}arris, {A}. and {L}aporte, {D}. and {R}izzo, {A}. {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{D}eveloping appropriate monitoring strategies in long-quiescent volcanic provinces is challenging due to the rarity of recordable geochemical and geophysical signals and the lack of experienced eruptive phenomenology in living memory. {T}his is the case in the {M}assif {C}entral ({F}rance) where the last eruptive sequence formed the {P}avin's {G}roup of {V}olcanoes, about 7 ka ago. {T}here, current evidence of a mantle activity reminiscence is suggested by the presence of mineral springwaters, mofettes, and soil degassing. {I}t appears fundamental as a prerequisite to decipher the evolution of the gas phase in the magmatic system at the time of the eruptive activity to understand the meaning of current local gas emissions. {I}n this study, we develop an innovative approach coupling {CO}2 densimetry and geochemistry of fluid inclusions from products erupted by the {P}avin's {G}roup of {V}olcanoes. 3{D} imagery by {R}aman spectroscopy revealed that carbonate forming in fluid inclusions may lead to underestimation of {CO}2 density in fluid inclusions by up to 50% and thus to unreliable barometric estimates. {F}ortunately, we found that this effect may be limited by focusing on fluid inclusions with a small diameter (<4 & mu;m) and where no solid phase is detected on {R}aman spectra. {T}he time evolution of the eruptions of the {P}avin's {G}roup of {V}olcanoes shows a progressive decrease of the pressure of magma storage (from more than 9 kbar down to 1.5-2 kbar) in parallel to magma differentiation (from basanites at {M}ontcineyre to benmoreites at {P}avin). {T}he analysis of the noble gases entrapped in fluid inclusions yielded two main conclusions: (1) the helium isotope signature ({R}c/{R}a = 6.5-6.8) is in the range of values obtained in fluid inclusions from mantle xenoliths in the {M}assif {C}entral ({R}c/{R}a = 5.6 & {PLUSMN}; 1.1, on average) suggesting partial melting of the subcontinental lithospheric mantle, and (2) magma degassing (4{H}e/40{A}r* from 4.0 to 16.2) mirrors magma differentiation and the progressive rise of the magma ponding zones of the {P}avin's {G}roup of {V}olcanoes. {A}ccording to our modelling, about 80% of the initial gas phase would be already exsolved from these magmas, even if stored at mantle depth. {B}ased on the results obtained from fluid inclusions, we propose a model of the evolution of the signature of noble gases and carbon isotopes from mantle depth to crustal levels. {I}n this frame, gas emissions currently emitted in the area ({R}c/{R}a = 6.1-6.7 and 4{H}e/40{A}r* = 1.7) point to an origin in the lithospheric mantle. {T}his study strongly encourages the establishment of a regular sampling of local gas emissions to detect potential geochemical variations that may reflect a change from current steady-state conditions.},
  keywords = {{F}luid inclusions ; {B}arometry ; {N}oble gases ; {M}agma degassing ; {M}onitoring ; {FRANCE}},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {634},
  numero = {},
  pages = {121603 [ p.]},
  ISSN = {0009-2541},
  year = {2023},
  DOI = {10.1016/j.chemgeo.2023.121603},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088218},
}