The influence of magmatic differentiation on the oxidation state of Fe in a basaltic arc magma

The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

“…magma chemistry similar to that observed at Agrigan volcano [Kelley and Cottrell, 2012]. This would mean that the undegassed Fina Nagu magmas have Fe 31 / P Fe ratios near 0.227-0.273, similar to that observed for the large subaerial and submarine edifices in Mariana arc.…”

“…Although we believe S degassing to be an unlikely explanation for the low S contents of Fina Nagu submarine glasses (see above), if S degassing did take place it is possible that the undegassed magmas had higher Fe 31 / P Fe ratios than those measured in the final erupted glasses. The reducing effects of S degassing have been observed at Agrigan, Erebus, and Kilauea volcanoes [Kelley and Cottrell, 2012;Moussallam et al, 2014Moussallam et al, , 2016, and could account for a change in Fe 31 / P Fe ratios of 0.05 units (absolute), for a Geochemistry, Geophysics, Geosystems…”

“…There is a simple relationship between trace element enrichment (e.g., Ba/La ratios) and oxidation in Mariana backarc basin and arc glasses, suggesting that aqueous slab fluids are oxidized and generate variably oxidized mantle melts, dependent on the ratio of fluid to mantle involved in melt generation (Figures 6b and 6e) [Brounce et al, 2014[Brounce et al, , 2015Kelley and Cottrell, 2012]. This is true of the Fe 31 / P Fe ratios and also of the calculated magmatic fO 2 values, the latter of which takes into consideration the effects of pressure, temperature, and anhydrous major element chemistry on the relationship between the oxidation state of Fe of fO 2 (Figure 6e).…”

NanoSIMS results from olivine-hosted melt embayments: Magma ascent rate during explosive basaltic eruptions

“…Given these uncertainties in sulfur behavior, and the likely changes in fluid-melt partitioning (Fiege et al, 2014) or speciation (Kelley and Cottrell, 2012) that could affect diffusion during degassing, we consider these fits successful in matching both H 2 O and S profiles with the same decompression rate. This is especially notable given the greater than two orders of magnitude difference in their diffusivities.…”

2.24 Ga mafic dykes from Taihua Complex, southern Trans-North China Orogen, and their tectonic implications

“…15a, the Zhaiwa mafic dykes are plotted in the transition fields between MORB and IAB, indicating a back arc setting more probable. Moreover, island arc basaltic rocks are more oxidized than basalts of other settings and will generate higher V contents and lower Ti/V ratios (Kelley and Cottrell, 2012;Shervais, 1982). Therefore, the relative lower V contents and higher Ti/V ratios, distinct from arc basalts, show that the Zhaiwa mafic dykes are in a back arc setting (Fig.…”