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<datestamp>2018-01-11</datestamp>
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<title lang=en>A simple model of Rn-222 accumulation leading to Pb-210 excesses in volcanic rocks</title>
<creator>Condomines, Michel</creator>
<creator>Sigmarsson, Olgeir</creator>
<creator>Gauthier, P. J.</creator>
<contributor>Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<contributor>Laboratoire Magmas et Volcans (LMV) ; Université Blaise Pascal - Clermont-Ferrand 2 (UBP) - Institut national des sciences de l'Univers (INSU - CNRS) - Université Jean Monnet [Saint-Étienne] (UJM) - Centre National de la Recherche Scientifique (CNRS)</contributor>
<source>ISSN: 0012-821X</source>
<source>Earth and Planetary Science Letters</source>
<publisher>Elsevier</publisher>
<identifier>hal-00496398</identifier>
<identifier>https://hal.archives-ouvertes.fr/hal-00496398</identifier>
<source>https://hal.archives-ouvertes.fr/hal-00496398</source>
<source>Earth and Planetary Science Letters, Elsevier, 2010, 293 (3-4), pp.331-338. 〈10.1016/j.epsl.2010.02.048〉</source>
<identifier>DOI : 10.1016/j.epsl.2010.02.048</identifier>
<relation>info:eu-repo/semantics/altIdentifier/doi/10.1016/j.epsl.2010.02.048</relation>
<language>en</language>
<subject lang=en>Radon degassing and accumulation in magmas</subject>
<subject lang=en>(210)pb-Ra-226 disequilibria</subject>
<subject lang=en>Pb-210 excesses in volcanic rocks</subject>
<subject lang=en>Santorini volcano</subject>
<subject lang=en>Surtsey Island</subject>
<subject>[SDU.STU.GC] Sciences of the Universe [physics]/Earth Sciences/Geochemistry</subject>
<subject>[SDE.MCG] Environmental Sciences/Global Changes</subject>
<type>info:eu-repo/semantics/article</type>
<type>Journal articles</type>
<description lang=en>While most rocks from active volcanoes display ((210)pb/Ra-226) activity ratios lower than or close to the equilibrium value of 1, several other have ratios much higher than 1. Transfer of Rn-222 by magmatic volatiles has often been advocated to explain both Pb-210 deficits and excesses. We develop here a model to account for Pb-210 excesses through Rn-222 accumulation. We show that large Pb-210 excesses can be readily obtained, even for moderate ratios of degassing magma over accumulating magma, in a closed-system model where the Rn-222 atoms produced by decay of Ra-226 in the degassing magma are continuously extracted by a gas phase. For a given duration of volatile transfer, relative Pb-210 excesses are expected to be much larger than Pb-210 deficits. This model is applied to samples from Santorini (Aegean arc) and Surtsey (Iceland) both of which show high ((210)pb/Ra-226) ratios of 6.7 and 2.3 respectively at the time of eruption. The agreement with field data suggests that Rn-222 accumulation leading to Pb-210 excesses might be a rather common process in zoned magma chambers as well as in individual lava flows, and that it can be described by a closed-system model.</description>
<date>2010</date>
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