Trace element partitioning between clinopyroxene, magnetite, ilmenite and ferrobasaltic to dacitic magmas: an experimental study on the role of oxygen fugacity and melt composition

Abstract

Ilmenite-, magnetite-and clinopyroxene−melt trace element partition coefficients were investigated experimentally as a function of oxygen fugacity and melt composition in a range of synthetic ferrobasaltic bulk compositions. The experiments were performed at a constant temperature (1080 °C) and pressure (1 atm) over a range of oxygen fugacity (fO 2 ) conditions from ca. 2 log units below to ca. 2 log units above the FMQ buffer. The partitioning behaviour of the divalent cations Zn, Mn, Co and Ni are found to be controlled by the degree of polymerisation of the coexisting melt; the partitioning behaviour of rare earth elements, Y and Sc can be explained well by the lattice strain model and the partitioning of the high-field strength elements Zr, Hf, Ta and Nb is influenced by the TiO 2 content of the melt. Vanadium partitioning is strongly influenced by oxygen fugacity and a series of linear regression equations are presented to express the dependence of the mineral−melt partitioning behaviour of the multivalent cation V on oxygen fugacity. Furthermore, calibration of the partitioning of vanadium between magnetite-ilmenite pairs as an oxybarometer is proposed and applied to a ferrobasaltic layered intrusion-the Skaergaard intrusion-to provide an estimate of oxygen fugacity.

Trace element partitioning in basaltic systems as a function of oxygen fugacity

“…Titanium is the most abundant High Field Strength Element (HFSE) on the clinopyroxene M1 site (Hill et al 2011 ) and serves as a proxy for other HFSE (Blundy and Wood 2003 ). We confirm observations by Forsythe et al ( 1991 ), Skulski et al ( 1994 ) and Shepherd et al ( 2022 ) who reported linear correlations between D Ti and D HFSE values for clinopyroxene in basalts at 1 atm and 1–2.8 GPa. In our experiments, we see only subtle positive correlation between Al IV and D Zr , D Nb and D Hf , in contradiction with the strong increases described in Lundstrom et al ( 1998 ) and Wood and Trigila ( 2001 ).…”

“…Moreover, D Sc is typically independent of temperature, f O 2 and crystal composition in other experimental series on basalts, e.g. 1.51 ± 0.13 (Mallmann and O’Neill 2009 ), 4.97 ± 0.45 (Shepherd et al 2022 ), 1.23 ± 0.16 (Karner et al 2008 ). The expression for D V /D Sc , adapted from Eq.…”

“…However, studies focusing on the effect of f O 2 on clinopyroxene/basalt Fe, Cr and V partition coefficients under conditions prevailing on Earth are rare (e.g. Mallmann and O’Neill 2009 ; Bédard 2014 ; Shepherd et al 2022 ) and the present study is the first to explore systematically the effect of f O 2 on D REE .…”

Titanite Petrochronology Records Secular Temperature and Fluid Evolution During Ductile Deformation: An Example From Late Cretaceous Shear Zones in the Eastern Transverse Ranges

“…The only textural distinction between the sub‐euhedral grains and the aggregates is that the aggregates are consistently associated with ilmenite and/or magnetite. If the growth of titanite aggregates from ilmenite and/or magnetite was the overarching control on the chemical differences between the titanite textures, then the titanite aggregates should be REE depleted when compared to the rim compositions (as the REE concentrations are negligible in both ilmenite and magnetite, e.g., Shepherd et al., 2022). However, the LREEs are enriched in the aggregates compared to the rims, and M–HREE concentrations are comparable between aggregates and rims (Figure 9a).…”

Trace element partitioning in silica-undersaturated alkaline magmatic systems

“…The partitioning behaviour of trace elements between melt and minerals has been studied for decades (e.g., Jensen 1973;Hart and Dunn 1993;Blundy and Wood 2003;Dubacq and Plunder 2018), either through the use of glass/groundmass-mineral pairs in rapidly quenched rocks (Onuma et al, 1968(Onuma et al, , 1981Fujimaki, 1986;Minissale et al, 2019), (Hart and Dunn, 1993;Dygert et al, 2014), or theoretical methods (Blundy and Wood, 1994;Van Westrenen et al, 2000;Dubacq and Plunder, 2018). Extensive literature is therefore available on partitioning behaviour for minerals commonly crystallizing from tholeiitic magmas such as clinopyroxene (e.g., Skulski et al, 1994;Johnson, 1998;Green et al, 2000;Hill et al, 2011;Bédard, 2014;Dygert et al, 2014;Shepherd et al, 2022), olivine (e.g., Irving, 1978;Beattie et al, 1991;Beattie, 1993;Taura et al, 1998;Bédard, 2005;Evans et al, 2008) and plagioclase (e.g., Bédard, 2006;Aigner-Torres et al, 2007;Tepley et al, 2010;Sun et al, 2017;Dygert et al, 2020), but data remain limited for minerals solely formed from silica-undersaturated magmas (e.g., leucite, melilite, nepheline). Published partition coefficients between feldspathoids and melt are based mainly on phenocryst-matrix observations (Onuma et al, 1981;Ewart and Griffin, 1994;Foley and Jenner, 2004;Arzamastsev et al, 2009;…”