Quaternary Geochronology 3 (2008) 196–205 Research Paper In situ cosmogenic 10 Be in olivines and pyroxenes P.-H. Blard a,b,Ã , D. Bourle`s a , R. Pik b , J. Lave´ c a Centre Europe´en de Recherche et d’Enseignement des Ge´osciences de l’Environnement, CNRS-Aix Marseille Universite´, Aix en Provence, France b Centre de Recherches Pe´trographiques et Ge´ochimiques, CNRS, Vandoeuvre-le`s-Nancy, France c Laboratoire de Ge´odynamique des Chaıˆnes Alpines, CNRS-Universite´Joseph Fourier, Grenoble, France Received 6 February 2007; received in revised form 23 August 2007; accepted 26 November 2007 Available online 11 January 2008 Abstract This study proposes an efficient new cleaning procedure for measuring in situ cosmogenic 10 Be in olivines and pyroxenes. This chemical routine is specially designed to decontaminate the abundant meteoric 10 Be 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 10 Be 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 10 Be. Moreover, cross-calibration with cosmogenic 3 He measured within the same samples yielded a sea level high-latitude production rate of 4.570.4 at g 1 a 1 for cosmogenic 10 Be in mafic minerals. This rate is within 1s uncertainty of empirically or model-derived rates for 10 Be on the same targets. Such concordance supports the consistency of the new method. r 2008 Elsevier Ltd. All rights reserved. Keywords: Cosmogenic; Beryllium; Helium; Olivine; Pyroxene; Chemical cleaning routine; Calibration; Lava flows; Production rate; Mt Etna; Mauna Kea 1. Introduction Cosmogenic nuclides produced in terrestrial rocks provide an efficient way to quantify several Earth-surface processes (Gosse and Phillips, 2001). To be reliably interpreted, most terrestrial cosmogenic nuclides (TCN) must be measured within specific pure mineral phases because: (i) the nuclide production rates, which depend on the major elements composition, may vary from one mineral to another (Masarik and Reedy, 1995), and (ii) the crystalline structure governs the capacity of retention of TCN (Trull et al., 1991), and the decontamination of an atmospheric component (when it exists) (Brown et al., 1991). Until now, applications of TCN have been restricted to the following systems: (i) 10 Be, 14 C, 21 Ne and 26 Al in quartz (e.g., Nishiizumi et al., 1986; Lifton et al., 2001; Graf et al., 1991); (ii) 3 He and 21 Ne in olivines, pyroxenes, garnets apatite, zircon and iron oxides (e.g. Kurz, 1986a; Marti and Craig, 1987; Gayer et al., 2004; Kober et al., 2005; Farley et al., 2006); (iii) 36 Cl in Ca- or K-rich phases (e.g. Phillips et al., 1986; Stone et al., 1996). Thus, exposure history applications are limited to a small number of TCN-minerals systems. In particular, mafic environments have been restricted to the stable noble gases 3 He and 21 Ne and to the radioactive nuclide 36 Cl. However, the application of 36 Cl may be limited by half-life considerations (T 1/2 ¼ 301 ka for 36 Cl). Consequently, the capacity to measure a longer-lived radioactive isotope in olivines or pyroxenes may have important implications for geomorphological studies in mafic environments, such as dating of burial events (e.g. Granger et al., 1997), or the determination of successive exposure histories (e.g. Blard et al., 2006a). The major limitation for measuring in situ cosmogenic 10 Be ( 10 Be c ) is the complete removal of the atmospheric contamination from the mineral phase of interest ARTICLE IN PRESS www.elsevier.com/locate/quageo 1871-1014/$ - see front matter r 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.quageo.2007.11.006 Ã Corresponding author. Present address: Geological and Planetary Science Division, California Institute of Technology, MC 100-23, 1200 E. California Boulevard, Pasadena, CA 91125, USA. Tel.: +1 626 395 6177. E-mail addresses: blard@gps.caltech.edu, phb26@yahoo.fr (P.-H. Blard).