@article{fdi:010068347,
  title = {{S}patial distribution of helium isotopes in volcanic gases and thermal waters along the {V}anuatu ({N}ew {H}ebrides) volcanic arc},
  author = {{J}ean-{B}aptiste, {P}. and {A}llard, {P}. and {F}ourr{\'e}, {E}. and {B}ani, {P}hilipson and {C}alabrese, {S}. and {A}iuppa, {A}. and {G}authier, {P}. {J}. and {P}arello, {F}. and {P}elletier, {B}ernard and {G}araebiti, {E}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e report the first helium isotope survey of volcanic gases, hot springs and some olivine phenocrysts along the {V}anuatu island arc, from {T}anna in the south to {V}anua {L}ava in the north. {L}ow {CO}2 content and low {H}e-3/{H}e-4 ratios in thermal fluids of {E}pi (4.0 +/- 0.1 {R}-a), {E}fate (4.5 +/- 0.1 {R}-a) and {P}entecost (5.3 +/- 0.5 {R}-a) islands coherently indicate reduced mantle gas leakage and crustal contamination by radiogenic helium on these extinct volcanic systems of the former ({P}liocene) arc. {I}nstead, presently active {V}anuatu volcanoes display {H}e-3/{H}e-4 and {C}/{H}e-3 ratios typical of subduction-related volcanic arcs: {H}e-3/{H}e-4 ratios range from 6.4 +/- 0.5 {R}a in southernmost {T}anna and 7.23 +/- 0.09 {R}-a in northernmost {V}anua {L}ava to typical {MORE} values in the central islands of {G}aua (7.68 +/- 0.06 {R}-a), {A}mbrym (7.6 +/- 0.8 {R}-a) and {A}mbae (7 2 {R}-a in groundwaters, 7.9 +/- 1.4 {R}-a in olivine phenocrysts, and 8.0 +/- 0.1 {R}a in summit fumaroles of {A}oba volcano). {O}n {A}mbrym, however, we discover that hydrothermal manifestations separated by only 10-15 km on both sides of a major {E}-{W} transverse fault zone crossing the island are fed by two distinct helium sources, with different 3{H}e/4{H}e signatures: while fluids in southwest {A}mbrym ({B}aiap and {S}esivi areas) have typical arc ratios (7.6 +/- 0.8 {R}-a), fluids on the northwest coast ({B}uama {B}ay area) display both higher {H}e-3/{H}e-4 ratios (9.8 +/- 02 {R}-a in waters to 10.21 +/- 0.08 {R}-a in bubbling gases) and lower {C}/{H}e-3 ratios that evidence a hotspot influence. {W}e thus infer that the influx of {I}ndian {MORB} mantle beneath the central {V}anuatu arc, from which {A}mbrym magmas originate, also involves a {H}e-3-rich hotspot component, possibly linked to a westward influx of {S}amoan hotspot material or another yet unknown local source. {T}his duality in magmatic {H}e source at {A}mbrym fits with the bimodal composition and geochemistry of the erupted basalts, implying two distinct magma sources and feeding systems. {M}ore broadly, the wide {H}e isotopic variations detected along the {V}anuatu arc further verify the complex tectonic and magmatic framework of this intra-oceanic island arc.},
  keywords = {{V}anuatu arc ; {V}olcanic fluids ; {H}elium isotopes ; {E}xtinct and active volcanoes ; {M}antle source ; {H}otspot contribution ; {VANUATU}},
  booktitle = {{U}nderstanding volcanoes in the {V}anuatu arc},
  journal = {{J}ournal of {V}olcanology and {G}eothermal {R}esearch},
  volume = {322},
  numero = {{N}o {S}p{\'e}cial},
  pages = {20--29},
  ISSN = {0377-0273},
  year = {2016},
  DOI = {10.1016/j.jvolgeores.2015.09.026},
  URL = {https://www.documentation.ird.fr/hor/fdi:010068347},
}