Oxidation states of mid-ocean ridge basalt glasses

Details Oxidation states of mid-ocean ridge basalt glasses Oxidation states of mid-ocean ridge basalt glasses

Sep 1986

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1986e%26psl..79..397c&link_type=abstract

Earth and Planetary Science Letters, Volume 79, Issue 3-4, p. 397-411.

Physics

118

Scientific paper

Precise new analyses of ferrous and total iron for 78 hand-picked mid-ocean ridge basalt (MORB) glasses constrain the redox states of MORB magmas, and the systematics of those redox states with respect to geography and chemistry. The data indicate that MORB magmas at the point of eruption include some of the most reduced terrestrial lavas yet analyzed. Irrespective of their tectonic setting, geographic setting or chemical type, quench glasses from the outer surfaces of MORB lavas have Fe3+/ΣFe ratios of 0.07 +/- 0.03 (2σ), equivalent to relative oxygen fugacities 1-2 log10 units below the fayalite-magnetite-quartz buffer (FMQ). These reduced values contrast markedly with those of cogenetic whole rocks, even for samples from the same pillow. Pillow cores (including virtually all published whole rock analyses) typically have Fe3+/ΣFe close to 0.15, equivalent to oxygen fugacities close to FMQ. The post-eruptive oxidation responsible for this contrast apparently occurs rapidly, while the lava is still partially molten, most likely as a result of hydrogen loss.
The striking contrast between glass and whole rock data suggests that two common assumptions with respect to treatment of MORB are inappropriate: (1) assumption of Fe3+/ΣFe close to 0.15 for calculating norms and magnesium numbers; and (2) assumption of FMQ conditions for experimental studies of MORB crystallization. Oxygen fugacities in the mantle source regions of MORB have also been assumed to be close to FMQ. It is likely that, redox states determined from wholly or partially crystalline lavas are generally not representative of magmatic values. The new data reported herein define a new and rigid upper limit for the oxidation state of the sub-oceanic mantle.

Affiliated with

Also associated with

No associations

Rating

Oxidation states of mid-ocean ridge basalt glasses does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Oxidation states of mid-ocean ridge basalt glasses, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Oxidation states of mid-ocean ridge basalt glasses will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1294536