@article{PAR00013615,
  title = {{E}scape of unradiogenic osmium during sub-aerial lava degassing : evidence from fumarolic deposits, {P}iton de la {F}ournaise, {R}eunion {I}sland},
  author = {{G}announ, {A}. and {V}lastelic, {I}. and {S}chiano, {P}ierre},
  editor = {},
  language = {{ENG}},
  abstract = {{T}his study presents new {R}e-{O}s isotope and elemental data in gas condensates and corresponding lavas in order to examine the geochemical behavior of these two elements during magma degassing at {P}iton de la {F}ournaise, {R}eunion {I}sland. {G}as sublimates formed between 2007 and 2011 at temperature ranging from 400 to ca. 100 degrees {C} include {N}a-{K} sulfate (aphthitalite), {N}a sulfate (thenardite), {C}a-{C}u sulfate (e.g. gypsum), {C}a-{M}g-{A}l-{F}e fluoride (e.g. ralstonite) and native sulfur. {T}he high temperature deposits show trace element typical of volcanic gas with high enrichment in {R}e (24 to 79 ppb), almost two order of magnitude higher than the corresponding lavas but with {O}s abundances similar to those of the lavas (14-132 ppt). {I}n contrast the {O}s contents of the low temperature fluoride deposits (13-77 ppb) are higher than any of the other condensates. {T}he fluorides are also enriched in {R}e, albeit to lesser extent than {O}s (2.9-15.3 ppb). {B}ased on high-temperature samples, the fluid/melt partition coefficients estimated for {R}e and {O}s are 100 +/- 80 and 1 +/- 2, respectively. {C}onsidering 1% of fluid loss, these partition coefficients translate into emanation coefficients of 0.50 (0.17-0.65) for {R}e and 0.01 (0-0.03) for {O}s. {T}hese results indicate that {R}e, unlike {O}s, is highly volatile at {P}iton de la {F}ournaise. {O}smium isotopic compositions of samples collected at medium and low temperature (<350 degrees {C}) are very uniform and unfractionated ({O}s-187/{O}s-188 between 0.130-0.135) and plot within the range of the {A}pril 2007 lava flow and the historical lavas of {P}iton de la {F}ournaise (i.e. 0.130-0.137). {H}owever the highest temperature condensates ({N}a-{K} sulfates with {T} of 384-400 degrees {C}) yield lower {O}s-187/{O}s-188 ratios (i.e. 0.124-0.129) within the field of mantle signal. {S}uch unradiogenic compositions are best explained if old mantle sulfides occur in lavas and contribute to volcanic gases. {W}ithin the general frame of osmium mantle geochemistry, loss of unradiogenic {O}s during magmas degassing could help to explain osmium isotope disequilibrium between lavas and melting residues.},
  keywords = {{REUNION} ; {PITON} {DE} {LA} {FOURNAISE} {VOLCAN}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {166},
  numero = {},
  pages = {312--326},
  ISSN = {0016-7037},
  year = {2015},
  DOI = {10.1016/j.gca.2015.06.039},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00013615},
}