AN EXPERIMENTAL STUDY OF THE EFFECT OF AL CONCENTRATION IN CLINOPYROXENE ON PARTITION COEFFICIENTS OF THE FIRST-ROW TRANSITION ELEMENTS

Chemical data of mid-ocean ridge basalts (MORB) and ocean islands basalts (OIB) suggest that the mantle is lithological heterogeneous in composition [1]. Heterogeneity is introduced into the mantle through subduction of oceanic crust which is then altered into eclogite under mantle conditions. These eclogites may then be recycled through basalt source regions contributing melts that are distinct from partial melts of peridotite. Previous work has suggested that these different source lithologies can be identified by measuring the systematics of trace elements, specifically the first row transition metals (FRTE) (i.e. Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn) and Ga, Ge, Hf, Nb, Ta, and Zr are particularly useful for tracing source lithology [2,3,4]. Partitioning of these elements between minerals and melts is composition-sensitive [4]. In this study we looked at how aluminum concentration in clinopyroxene affects the partitioning of these key elements. We performed piston cylinder experiments to stabilize clinopyroxenes with varying Al-concentrations with a melt phase at a pressure of 1 GPa and temperatures from 1175-1280 °C. We plan to present scanning electron microscope (SEM) images used to identify crystals large enough for trace element analysis, major element analysis by electron probe microanalysis (EPMA), and trace element analysis by laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS). These data will be used to calculate partition coefficients which will allow for better model of melts derived from heterogeneous sources in the upper mantle.

[1] Zindler and Hart 1986. Ann. Rev. Mineral. Planet. Sci.; [2] Humayun et al. 2004. Science.; [3] Le roux et al. 2011. Earth Planet. Sci. Lett.; [4] Davis et al. 2013. Geochim. Cosmochim. Acta.