Earth and Planetary Science Letters 384 (2013) 178–187 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Constraints on light noble gas partitioning at the conditions of spinel-peridotite melting Colin R.M. Jackson a,∗ , Stephen W. Parman a , Simon P. Kelley b , Reid F. Cooper a a Geological Sciences, Brown University, Providence, RI, United States b Department of Environment, Earth & Ecosystems, The Open University, Milton Keynes, United Kingdom article info abstract Article history: Received 19 April 2013 Received in revised form 11 September 2013 Accepted 28 September 2013 Available online 1 November 2013 Editor: B. Marty Keywords: noble gas solubility mineral–melt partitioning basalt genesis Helium partitioning between olivine, orthopyroxene, clinopyroxene, and spinel and basaltic melt has been experimentally determined under upper mantle melting conditions (up to 20 kbar and 1450 ◦ C). Under the conditions explored, helium partition coefficients are similar in all minerals investigated ( K He d ∼ 10 −4 ), suggesting He is evenly distributed between the minerals of spinel peridotite. This is in contrast to most incompatible elements, which are concentrated in clinopyroxene in spinel peridotite. The studied minerals have different concentrations of point defects, but similar He solubility, providing no evidence for He partitioning onto specific defects sites (e.g. cation vacancies). Upper limits on the partition coefficients for Ne and Ar have also been determined, constraining these elements to be moderately to highly incompatible in olivine at the conditions of spinel peridotite melting (<10 −2 and <10 −3 , respectively). Helium partitioning in peridotite minerals varies little within the range of temperatures, pressures, and mineral compositions explored in this study. Reported partition coefficients, in combination with previous work, suggest that moderate to high degree mantle melting is not an efficient mechanism for increasing (U+Th)/He, (U+Th)/Ne, or K/Ar of the depleted mantle (DMM) through time, and consequently, supports the argument that recycling of oceanic crust is largely responsible for the relatively strong radiogenic noble gas signatures in the depleted mantle. Mantle residues with lowered (U+Th)/He, (U+Th)/Ne, and K/Ar may be produced through large extents of melting, but concentrations of noble gases will be low, unless noble gas solubility in solids deviate from Henry’s Law at high fugacity.  2013 Elsevier B.V. All rights reserved. 1. Introduction Noble gas isotope and elemental variations in mantle-derived material are records of the Earth’s volatile element evolution. Inter- preting this record requires an understanding of noble gas behavior at conditions relevant to upper mantle melting. Given the inert na- ture of noble gases, models of noble gas evolution often assume that they are perfectly incompatible (C α i /C liq i = 0) during mantle melting, resulting in rapid and uniform extraction from the residue (e.g. Allegre et al., 1996; Onions and Oxburgh, 1983). Early experi- mental work, however, did not support these predictions. Multiple studies have reported compatible (C α i /C liq i > 1) behavior, especially for heavier noble gases (Broadhurst et al., 1990, 1992; Hiyagon and Ozima, 1982, 1986; Shibata et al., 1994). Refinements in experimental and analytical methods have gen- erally yielded lower noble gas partition coefficients, although with variable accuracy and precision. Significantly, the development of combined UV laser ablation and noble gas mass spectrometry al- lows for analysis of small volumes of material with fine spatial * Corresponding author. control (Brooker et al., 1998). This approach limits the inadver- tent incorporation of secondary, gas-rich phases that can pro- duce apparently high noble gas solubilities for solids. A series of studies utilizing simple system compositions (formulated to re- duce the density of fluid inclusions in synthesized crystals and co-existing glasses) and UV laser analysis yielded noble gas (He– Xe) partition coefficients between 10 −3 and 10 −4 for olivine and clinopyroxene (Brooker et al., 2003, 1998; Chamorro et al., 2002; Heber et al., 2007). Somewhat higher (∼10×) partition coefficients for He have been reported by Parman et al. (2005) using an alter- native approach. This study prepared samples by gas-soaking cubes of olivine in 0.5 bar of He using a 1 atm furnace. These cubes of olivine were then crushed and melted in the extraction line of a mass spectrometer. Partition coefficients were calculated only us- ing the gas extracted by melting. In contrast, more recent work utilizing Rutherford backscatter- ing (RBS) analysis suggests that Ar is highly compatible in both olivine and pyroxene, with partition coefficients up to ∼10 4 (as- suming literature values for noble gas solubility in melts, Watson et al., 2007; Thomas et al., 2008). These studies employed a con- stant source diffusion approach to defining Ar solubility in miner- als, using Ar as the pressure medium and ranging Ar fugacity ( f Ar) 0012-821X/$ – see front matter  2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.epsl.2013.09.046