Earth and Planetary Science Letters 392 (2014) 265–278 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Trace element mineral/melt partitioning for basaltic and basaltic andesitic melts: An experimental and laser ICP-MS study with application to the oxidation state of mantle source regions Muriel Laubier a,b,∗ , Timothy L. Grove c , Charles H. Langmuir a a Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, USA b Laboratoire Magmas et Volcans, Université Blaise Pascal – CNRS – IRD, 5 rue Kessler, F-63038 Clermont-Ferrand Cedex, France c Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA article info abstract Article history: Received 30 November 2012 Received in revised form 8 November 2013 Accepted 31 January 2014 Available online xxxx Editor: T. Elliott Keywords: partitioning oxygen fugacity MORB arc magmas mantle trace elements Understanding magmatic processes such as crystallization and melting recorded in natural samples requires calibration of mineral–melt trace element partition coefficients ( D) and their dependence on temperature, pressure, oxygen fugacity ( f O 2 ) and chemical composition. However, few experimental studies have focused on measuring trace element partition coefficients for a large number of trace elements, in the various minerals present in basaltic rocks, and under diverse conditions, particularly of variable f O 2 . Twenty-seven 0.1 MPa experiments provide partition coefficients for major elements and Sc, Ti, V, Mn, Co, Ni, Ga, Sr, Y, Nb, Ba, Ce, Nd, Eu, Gd, and Yb for the mineral phases olivine, plagioclase, orthopyroxene and clinopyroxene. The experimental conditions range from 1150 to 1190 ◦ C with oxygen fugacities from QFM to NNO+2. Run products were analyzed by laser-ablation ICP-MS. The new partition coefficients, combined with previously published data, can be used to model crystallization processes at low pressure. Partitioning of multivalent cations V, Fe and Eu varies as a function of the redox conditions, consistent with previous work, and can be used to constrain oxidation states of magmatic source regions. The V/Yb ratio is shown to be a useful proxy for oxidation state. The V/Yb ratio varies during mantle melting as a function of oxidation state of the mantle source, and it is not modified during fractional crystallization of olivine ± plag ± cpx. V/Yb increases from MORB, BABB to arc lavas, suggesting a progressive increase of f O 2 from QFM to NNO+2. Apparent f O 2 of arc lavas, however, is quite variable. These results demonstrate that sub-arc mantle displays a larger range of redox conditions toward a more oxidized mantle than the MORB mantle.  2014 Elsevier B.V. All rights reserved. 1. Introduction Modeling magmatic processes such as crystallization and melt- ing requires calibration of mineral–melt trace element partition co- efficients ( D) and how they vary with temperature, pressure, oxy- gen fugacity ( f O 2 ) and chemical composition. Despite the develop- ments in in-situ analytical techniques in the past twenty years that make this task achievable, few studies have focused on measuring partition coefficients for a large number of trace elements under diverse conditions, particularly of variable f O 2 (Aigner-Torres et al., 2007; Bindeman et al., 1998). Oxygen fugacity is of particular cur- rent interest because of a debate over how mantle f O 2 may vary in different tectonic environments (Frost and McCammon, 2008). * Corresponding author at: Laboratoire Magmas et Volcans, Université Blaise Pas- cal – CNRS – IRD, 5 rue Kessler, F-63038 Clermont-Ferrand Cedex, France. E-mail address: m.laubier@opgc.univ-bpclermont.fr (M. Laubier). While convergent margin magmas are generally more oxidized at the surface (e.g. Carmichael, 1991) and sub-arc mantle records more oxidizing conditions (Parkinson and Arculus, 1999), there is dispute over the relative oxidation states of ocean ridge and con- vergent margin mantle sources (Dauphas et al., 2009; Kelley and Cottrell, 2009; Lee et al., 2005; Lee et al., 2012; Lee et al., 2010; Mallmann and O’Neill, 2009). Lee et al. (2005) and Li and Lee (2004) suggest that arc magma sources are as reduced as MORB sources. Elements that have variable oxidation states under terrestrial conditions have the potential to constrain the redox state of mag- mas. V, Fe, and Eu can have multiple oxidation states, influenc- ing their partition coefficients. V occurs as V 3+ and V 4+ (Canil, 1999; Gaetani and Grove, 1997). Because V 3+ is preferentially included in igneous minerals, D mineral/melt V decreases as f O 2 in- creases since more of the V is in the incompatible 4+ form. Sim- ilarly, Eu and Fe occur both as 2+ and 3+ ions in magmas, and http://dx.doi.org/10.1016/j.epsl.2014.01.053 0012-821X/ 2014 Elsevier B.V. All rights reserved.