The oxidation state of Fe in MORB glasses and the oxygen fugacity of the upper mantle

Cottrell, Elizabeth; Kelley, K. A.

doi:10.1016/j.epsl.2011.03.014

Cited by 412 publications

(260 citation statements)

References 58 publications

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“…Coexisting Fe-Ti oxides in dolerites and in one grain of basalt give more reducing ΔNNO values of -0.80 and -1.26 (ΔFMQ of 0.91 and -1.44), respectively. These values are in agreement with those obtained for coexisting magnetite and ilmenite in one sample of the Hole 1256D lava pond Koepke et al, 2008) and are within the range observed in MORB glasses (Christie et al, 1986;Bézos and Humler, 2005;Cottrell and Kelley, 2011).…”

Section: Redox Conditionssupporting

confidence: 80%

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

Abily¹,

Python²

2016

Proceedings of the IODP

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This data report presents an uncommon study of fine drill cuttings (sand and gravels) recovered from hole maintenance operations in Ocean Drilling Program/Integrated Ocean Drilling Program (IODP) Hole 1256D (East Pacific Rise) during Expedition 335. Drill cuttings represent an integrated sampling of the entire hole and offer the opportunity to study the petrological characteristics of the various lithologies making up the upper oceanic crust. We selected the fine-grained fraction of cuttings coming from 12 pipe deployments (runs) and conducted microscopic observations (mineralogy and texture), image processing, electron microprobe analyses (~4400 analyses), and oxythermobarometry calculations on 16-25 grain-mount thin sections.This study shows that drill cuttings sample all of the lithologies in the hole (glass, aphyric and phyric basalts, dolerite, gabbro, diorite, gabbronorite, albitite, and three kinds of granoblastic basalt) but overrepresent non-or poorly recovered materials like albitites and granoblastic basalts. Drill cuttings are thus a good alternative to study these "rare" lithologies. Based on the composition of the main minerals and the oxythermobarometry calculations, two major lithologic groups were defined in the cuttings: a basaltic lavas-dolerites group and a gabbroic lithologies-granoblastic basalts group. Basaltic lavas (glass and basalts) and dolerites are characterized by Mg-augites rich in Al 2 O 3 , Cr 2 O 3 , and TiO 2 ; MgO-rich plagioclases with a mean composition of An 60-70 ; and titanomagnetites. Their Fe-Ti oxides (magnetite and ilmenite) indicate relatively reducing conditions (ΔNNO = -1.26 to -0.80), and clinopyroxenes in dolerites give a mean equilibrium temperature of 1017°C. Gabbroic lithologies and granoblastic basalts are characterized by Ca-rich clinopyroxenes (augites and diopsides) depleted in Al 2 O 3 , Cr 2 O 3 , and TiO 2 ; MgO-poor plagioclases with a mean composition of An 50-60 ; and Ti-poor magnetites. Oxybarometers give oxidizing (ΔNNO = -0.08 to +0.58) to very oxidizing (ΔNNO = +1.97 to +2.38) conditions for these lithologies, and their pyroxenes indicate high (909°C-985°C) to relatively high (783°C-888°C) mean temperatures according to the thermometer considered. Albitites show equivalent mineral compositions and temperature and redox conditions to gabbroic lithologies and granoblastic basalts. They are, however, characterized by albitic plagioclases (An 0-20 ) and usually display slightly lower temperatures (780°C) and higher ΔNNO values (+2

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Section: Redox Conditionssupporting

confidence: 80%

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

Abily¹,

Python²

2016

Proceedings of the IODP

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“…Implicit in this assessment is the assumption that fractional crystallization proceeds in a system closed to oxygen. Evidence from a global study of MORB glass suggests that closed system fractionation of olivine ± plagioclase ± clinopyroxene explains variations in Fe 3+ /∑Fe ratios (Cottrell & Kelley, 2011). In our present study, each modeled LLD assumes a D Fe3+ = 0 and a D Fe2+ that varies according to the mineral-melt models chosen, for olivine ± clinopyroxene ± plagioclase fractionation.…”

mentioning

confidence: 98%

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Brounce

Kelley

Cottrell

2014

Journal of Petrology

221

145

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When collecting Fe-µ-XANES spectra on olivine-hosted melt inclusions, it is important to avoid hitting the olivine crystal with the beam during analysis. Olivine contains several weight percent of Fe 2+ and even a very small amount of olivine interference will "contaminate" the pre-edge structure of Fe-µ-XANES spectra collected for melt inclusions and bias the result towards more reduced values. The region of XANES spectra at higher energies than the Fe-Kα absorption edge contains information related to Fe-coordination and can be used to distinguish glass structure (random and on average, uncoordinated) from olivine signal (strong coordination, Fig. A1). All melt inclusion and seafloor glass spectra were visually inspected and compared to spectra taken on San Carlos olivine and standard glasses from Cottrell et al. (2009) in order to screen for crystal contamination. Any spectra demonstrating signs of spectral features similar to those observed in San Carlos olivine were not considered in this study and additional spectra were collected to accommodate for this elimination. Model liquid lines of descentTo constrain the effects of fractional crystallization on magmatic Fe 3+ /∑Fe ratios, model liquid lines of descent that match the observed major element variations were generated using PetroLog3 (Danyushevsky & Plechov, 2011). The mineral-melt models that most closely replicate the natural data were chosen for each location, resulting in some variation in the models used from volcano to volcano. Individual model parameters

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“…The breakdown of an oxidizing assemblage could potentially oxidized slab components to fluid-mobile agents of oxidation (e.g., S 22 to SO 3 ) [Gaillard et al, 2015]. The fluid that contributes to Fina Nagu volcanism, unlike the rest of the arc, may have oxygen fugacity similar to the ambient upper mantle (i.e., near the quartz-fayalite-magnetite oxygen buffer) [Cottrell and Kelley, 2011], or may not have significant concentrations of species capable of producing oxidized mantle melts (e.g., S, Fe) [Mungall, 2002]. That magmatic fO 2 remained relatively low from mantle melting through to eruption is supported by the lack of magnetite fractionation from melts with higher than 3-4 wt.…”

Section: Geochemical Constraintsmentioning

confidence: 99%

“…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). Surprisingly, Fina Nagu glasses do not follow the relationship between increasing Ba/La and Fe 31 / P Fe ratios that is defined by >150 submarine glass chips and olivine hosted melt inclusions from Mariana arc volcanoes, the Mariana Trough, and global MORB, including submarine glass chips that record the initiation of subduction along the Izu-Bonin-Mariana convergent margin (Figures 6b and 6e) [Brounce et al, 2014[Brounce et al, , 2015Cottrell and Kelley, 2011;Kelley and Cottrell, 2009].…”

Section: Geochemical Constraintsmentioning

confidence: 99%

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

Brounce

Kelley

Stern

et al. 2016

Geochem Geophys Geosyst

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In the Mariana convergent margin, large arc volcanoes disappear south of Guam even though the Pacific plate continues to subduct and instead, small cones scatter on the seafloor. These small cones could form either due to decompression melting accompanying back-arc extension or flux melting, as expected for arc volcanoes, or as a result of both processes. Here, we report the major, trace, and volatile element compositions, as well as the oxidation state of Fe, in recently dredged, fresh pillow lavas from the Fina Nagu volcanic chain, an unusual alignment of small, closely spaced submarine calderas and cones southwest of Guam. We show that Fina Nagu magmas are the consequence of mantle melting due to infiltrating aqueous fluids and sediment melts sourced from the subducting Pacific plate into a depleted mantle wedge, similar in extent of melting to accepted models for arc melts. Fina Nagu magmas are not as oxidized as magmas elsewhere along the Mariana arc, suggesting that the subduction component responsible for producing arc magmas is either different or not present in the zone of melt generation for Fina Nagu, and that amphibole or serpentine mineral destabilization reactions are key in producing oxidized arc magmas. Individual Fina Nagu volcanic structures are smaller in volume than Mariana arc volcanoes, although the estimated cumulative volume of the volcanic chain is similar to nearby submarine arc volcanoes. We conclude that melt generation under the Fina Nagu chain occurs by similar mechanisms as under Mariana arc volcanoes, but that complex lithospheric deformation in the region distributes the melts among several small edifices that get younger to the northeast.

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The oxidation state of Fe in MORB glasses and the oxygen fugacity of the upper mantle

Cited by 412 publications

References 58 publications

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

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

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