In situ cosmogenic 10Be in olivines and pyroxenes

P.-H. Blard (1, 2) , D. Bourles (2) , R. Pik (1) , J. Lavé (3)

1 CRPG - Centre de Recherches Pétrographiques et Géochimiques
2 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
3 LGCA - Laboratoire de Géodynamique des Chaines Alpines

This study proposes an efficient new cleaning procedure for measuring in situ cosmogenic 10Be in olivines and pyroxenes. This chemical routine is specially designed to decontaminate the abundant meteoric 10Be from these minerals. The method was tested on mafic minerals from basaltic flows of Mt. Etna volcano and from Hawaiian flows and moraines. A sequential dissolution test shows that 10Be concentrations decrease with the number of cleaning steps until reaching a constant value. This is a necessary condition to demonstrate the efficiency of the method in properly decontaminating samples of meteoric 10Be. Moreover, cross-calibration with cosmogenic 3He measured within the same samples yielded a sea level high-latitude production rate of 4.5±0.4 at g−1 a−1 for cosmogenic 10Be in mafic minerals. This rate is within 1σ uncertainty of empirically or model-derived rates for 10Be on the same targets. Such concordance supports the consistency of the new method.

Mots clés: Cosmogenic; Beryllium; Helium; Olivine; Pyroxene; Chemical cleaning routine; Calibration; Lava flows; Production rate; Mt Etna; Mauna Kea

P.-H. Blard, D. Bourles, R. Pik, J. Lavé. In situ cosmogenic 10Be in olivines and pyroxenes. Quaternary Geochronology, 2008, 3 (3), pp.196 à 205. ⟨10.1016/j.quageo.2007.11.006⟩. ⟨insu-00354494⟩