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Ideal mixing of divalent cations in mafic magma. II. The solution of NiO and the partitioning of nickel between coexisting olivine and liquid

1987; Elsevier BV; Volume: 51; Issue: 2 Linguagem: Inglês

10.1016/0016-7037(87)90233-x

1872-9533

Christopher D Doyle, A. J. Naldrett,

earthquake and tectonic studies

Using both high- and low-NiO starting materials, a set of aluminosilicate liquids are equilibrated with metallic nickel under controlled oxygen fugacity at 1400°C to contour a Matrix-NiO-MgO ternary system for aNiO. The ternary contains a synthetic analog of standard diabase W-1. The results demonstrate that the relation aternaryNiO = aMg-freeNiO × Ni(Ni + Mg) accounts for the variation of aNiO at constant mole fracti of Matrix (XMatrix = 1 − XNio − XMgO) in the ternary system. This suggests that the divalent cations of Ni and Mg mix ideally on the sites that they occupy in mafic magmas. Using Doyle and Naldrett's (1986) simple mixing model for aluminosilicate liquids, the compositional dependence of aNiO in a wide range of mafic and intermediate magmas is strongly temperature sensitive. The data are consistent with CaAl2Si2O8 being a component of the Matrix and the remaining Ca mixing ideally with the divalent cations of Fe, Mn, Mg and Ni. These findings are used to understand better the controls on the partitioning of Ni between coexisting olivine and mafic or intermediate liquid.