PHD Defense of Sandrine Peron ” Origin of terrestrial volatile elements: contribution of rare gas geochemistry”

Sandrine Peron, doctoral student of the team I6 : De la poussière aux planètes, is pleased to invite you to her thesis defence entitled :

Origin of terrestrial volatile elements: contribution of rare gas geochemistry.

The defense will take place on Tuesday, December 4 at 14:00 in the IPGP amphitheatre in front of the jury composed of :

  • Sujoy Mukhopadhyay – Rapporteur (UC Davis)
  • Philippe Sarda – Rapporteur (University of Paris Sud)
  • Catherine Chauvel – Examiner (IPGP)
  • Evelyn Füri – Examiner (CRPG)
  • Manuel Moreira – Thesis Director (University of Paris Diderot)


The origin of volatiles, elements with low condensation temperatures such as water, nitrogen, carbon and noble gases, on Earth and other terrestrial planets is still misunderstood. Determining how these elements were delivered to the Earth will allow a better understanding of the processes of solar system formation.

Due to their inertness, noble gases (He, Ne, Ar, Kr, Xe) constitute unique tracers of  volatiles sources. Studying the noble gas composition of the Earth’s mantle is hence critical to unravel volatile origin. The aim of this PhD was to measure precisely the composition of non-radiogenic, stable noble gas isotopes in the mantle from basaltic glasses. The latter being very often contaminated by air, analytical techniques were thus set up to overcome this contamination.

Samples from Fernandina volcano from the Galápagos hotspot were studied with laser ablation. The results show that the mean 20Ne/22Ne ratio in the vesicles is 12.65 +/- 0.04 (1sigma), close to the estimated value of the solar wind implanted end-member (about 12,7). This study suggests that light volatiles in the mantle would originate from  implantation of solar wind on the Earth’s precursors grains.

Data from popping rock samples, also analyzed with this technique, indicate that the upper mantle is heterogeneous at small scale and that noble gases, included He, Ne, could be recycled into the mantle in subduction zones.

A new protocol to analyse Kr and Xe was set up. The results show the highest measured excess in 124Xe, 126Xe and 128Xe for the mantle and suggest a chondritic source. The xenon fissiogenic isotopes allowed us to constrain the onset of volatile recycling in the mantle to around 3 Ga.