Rapid magma ascent recorded by water diffusion profiles in mantle olivine

Sylvie Demouchy (1) , Steven D. Jacobsen (1) , Fabrice Gaillard (1, 2) , Charles R. Stern (3)

1 Bayerisches Geoinstitut - Bavarian Research Institute of Experimental Geochemistry and Geophysics
2 ISTO - Institut des Sciences de la Terre d'Orléans
3 Department of Geological Sciences [Boulder]

Mechanisms and rates of magma ascent play a critical role in eruption dynamics but remain poorly constrained phenomena. Water, dissolved in mantle minerals as hydrogen and partitioned into the magma during ascent, may provide clues to quantifying magma ascent rates prior to eruption. We determined the dehydration profiles in olivine crystals from peridotite mantle xenoliths within the Pali-Aike alkali basalt from Patagonia, Chile. The results demonstrate that the amount of water stored in the uppermost mantle has likely been underestimated due to water loss during transport. Using experimental diffusion data for hydrogen, we estimate that the xenoliths reached the surface from 60–70 km depth in several hours, a surprisingly rapid rise comparable to ascent rates for kimberlite magmas.

Keywords: Earth's upper mantle; mantle xenolith; hydrogen; diffusion; olivine; magma ascent rate

Domains: Volcanology

Sylvie Demouchy, Steven D. Jacobsen, Fabrice Gaillard, Charles R. Stern. Rapid magma ascent recorded by water diffusion profiles in mantle olivine. Geology, 2006, 34, pp.429-432. ⟨10.1130/G22386.1⟩. ⟨hal-00091693⟩