The systematics of Cr3+ and Cr2+ partitioning between olivine and liquid in the presence of spinel

Abstract

The partitioning behaviour of Cr into olivine in basaltic systems has been parameterized and can now be modified over a wide range of redox conditions and liquid compositions. The Cr2+/Cr3+ in spinel-saturated experimental systems can be estimated based on a simple model of Cr solubility in basalt. Fe3+ appears to suppress the presene of Cr2+ in basaltic systems. We predict that, in Fe-free systems, all Cr is trivalent at log ∫o2 = -3 (ie QFM+3 to QFM+4), whereas all Cr is trivalent at approximately Ni-NiO(QFM+1) in Fe-bearing systems. Cr2+ predominates under redox conditions