3.3.1. Fe‐Based Oxybarometry
Mid‐Ocean Ridges.
Mid‐ocean ridges sample Earth’s convecting mantle and represent the majority of volcanism on the planet. Both melts and mantle lithologies offer opportunities for oxybarometry. We begin with the volcanics.
Table 3.1 Results and Method Summary.
| Tectonic setting | δQFM (s) | Lithology | n | Method | Activity‐composition models and other method notes | Method error in fO2 in log units | Notes | Data included |
|---|---|---|---|---|---|---|---|---|
| mid‐ocean ridge | –0.17 (0.15) | basalt pillow glass | 160 | XANES | At 1atm. Kress & Carmichael, 1991; parameterization of fO2 as a function of composition | 0.27 | Fe oxidation state determined using the Mössbauer calibration of Zhang et al., 2018 | Cottrell & Kelley, 2011; Le Voyer et al., 2015 (except the 6 analyses of hydrothermally altered dredge 16D); Birner et al., 2018 |
| mid‐ocean ridge | 0.19 (0.36) | basalt pillow glass | 42 | XANES | At 1atm. O’Neill et al., 2018; parameterization of fO2 as a function of composition | 0.52 | Fe oxidation state determined using the Mössbauer calibration of Berry et al., 2018 | O’Neill et al., 2018 |
| mid‐ocean ridge | 0.16 (–) | lava | 1 | mag‐ilm pairs | fO2 at T recorded and 1 atm. Ghiorso & Evans 2008 | 0.25** | passes Bacon & Hirschmann, 1988, test for equilibrium | Mazzullo & Bence, 1976 |
| mid‐ocean ridge | 0.31 (0.73) | peridotite | 72 | sp‐oxybarometry | fO2 at T and 0.6GPa. Mattioli & Wood, 1988; and Wood & Virgo, 1989; with aFe3O4 from Sack & Ghiorso, 1991a, 1991b; http://melts.ofm‐research.org/CalcForms/index.html; Temperature from spinel‐olivine Fe‐Mg exchange thermometer of Li et al., 1995 | Between about +0.6/–1.0 and ±0.2 depending on spinel Fe3+/∑Fe ratio of spinel (see Methods Appendix and Davis et al., 2017)*** | see Davis et al., 2017; and Birner et al. 2017; for discussions of a‐X model choices | Bryndzia & Wood, 1990; Birner et al., 2018 |
| back arc basin spreading center | 0.22 (0.30) | submarine lava | 37 | XANES | at 1atm and 1200°C. Kress & Carmichael, 1991 | 0.27 | Kelley & Cottrell, 2009; Brounce et al., 2014 | |
| arc front | 0.96 (0.39) | basalt glass in olivine‐hosted inclusions, basalt pillow glass | 119 | XANES | at 1atm and 1200°C. Kress & Carmichael, 1991 | 0.27 | Bonnin‐Mosbah, 2001; Kelley & Cottrell, 2009; Kelley & Cottrell, 2012; Brounce et al., 2014; Brounce et al., 2016 (data from Gaetani et al., 2012, excluded from average due to oxidative beam damage) | |
| arc front | 1.28 (0.64) | volcanics (lavas and tephra) | 114 | mag‐ilm pairs | fO2 at T recorded and 1 atm. Ghiroso & Evans, 2008 | 0.25** | passes Bacon & Hirschmann, 1988, test for equilibrium | Carmichael, 1967; Luhr & Carmichael, 1980; Wallace & Carmichael, 1994; Rutherford & Devine, 1996; Mandeville et al., 1996; Luhr, 2000; Coombs & Gardner, 2001; Devine et al., 2003; Costa et al., 2004; Grove et al., 2005; Larsen, 2006; Toothill et al., 2007; Izbekov et al., 2002; Browne et al., 2010; Baggerman & Debari, 2011; Crabtree & Lange, 2011; Stelten & Cooper, 2012; Arce et al., 2013; Waters & Lange, 2013; Howe et al., 2014; Frey & Lange, 2011; Muir et al., 2014; Waters et al., 2015; Grocke et al., 2016; Crabtree & Waters, 2017; Waters & Frey, 2018 |
| arc front | 0.96 (0.81) | peridotite xenoliths | 47 | sp‐oxybarometry | fO2 at T and 0.6GPa. Mattioli & Wood, 1988; and Wood & Virgo, 1989; with aFe3O4 from Sack & Ghiorso, 1991a, 1991b; http://melts.ofm‐research.org/CalcForms/index.html; Temperature from spinel‐olivine Fe‐Mg exchange thermometer of Li et al., 1995 | Between about +0.6/–1.0 and ±0.2 depending on spinel Fe3+/∑Fe ratio of spinel (see Methods Appendix and Davis et al., 2017)*** | see Davis et al., 2017; and Birner et al., 2017; for discussions of a‐X model choices | Wood & Virgo, 1989; Canil, 1990; Brandon & Draper, 1996; Parkinson et al., 2003; Bénard et al., 2018 |
| forearc | 0.22 (0.75) | trench wall peridotite and peridotite xenoliths | 64 | sp‐oxybarometry | fO2 at T and 0.6GPa. Mattioli & Wood, 1988; and Wood & Virgo, 1989; with aFe3O4 from Sack & Ghiorso, 1991a, 1991b; http://melts.ofm‐research.org/CalcForms/index.html; Temperature from spinel‐olivine Fe‐Mg exchange thermometer of Li et al., 1995 | Between about +0.6/–1.0 and ±0.2 depending on spinel Fe3+/∑Fe ratio of spinel (see Methods Appendix and Davis et al., 2017)*** | see Davis et al., 2017; and Birner et al., 2017; for discussions of a‐X model choices | Parkinson & Pearce, 1998; Pearce et al., 2000; Birner et al., 2017 |
| plume | 0.10* (0.71) | basalt pillow glass |
|