Magma Redox Geochemistry. Группа авторов

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СКАЧАТЬ Laubier et al. (2014), we filter these compilations for 6 wt.% < MgO < 12 wt.% to ensure that we are evaluating compositions that represent liquids (not cumulates) and that magnetite has not yet begun to crystallize (V is compatible in magnetite). We only evaluate compositions with Dy/Yb < 2 to avoid residual garnet in the source (Laubier et al., 2014). With these filters in place, we compile trace element data for 1294 MORB and 225 BABB, as well as 317 basalts from 37 arc‐front volcanoes. We did not include plume‐derived basalts in this comparison because the residual garnet in plume sources complicates interpretation of V/Yb. Yb (and Sc) are highly compatible in garnet, and the relationship between V/Yb (or V/Sc) and fO₂ is poorly defined (Canil, 2002; Davis et al., 2013; Lee et al., 2005).

3.3. RESULTS

      Calculated fO₂ for each sample in this study is available in the data library associated with this publication (Cottrell et al., 2021).

      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 СКАЧАТЬ В начало < 31 32 33 34 35 36 37 38 39 40 > В конец