Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Mattioli, G. S.; Baker, M. B.; Rutter, Michael J.; Stolper, Edward M.

doi:10.1086/629332

Cited by 65 publications

(16 citation statements)

References 61 publications

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“…Olivine deformation is influenced by the chemical environment in which it occurs. Subduction carries down volatiles that promote magma genesis (Anderson, Uyeda & Miyashiro 1976;Tatsumi 1986), metasomatize the sub-arc mantle (Maury, Defant & Joron 1992), and locally oxidize it (Mattioli et al 1989;Wood, Bryndzia & Johnson 1990). Oxidizing conditions make olivine more deformable (Kohlstedt & Hornack 1981;Ryerson et al 1989).…”

Section: Discussionmentioning

confidence: 99%

Shear-wave splitting variation over short spatial scales on continents

Helffrich

Silver

Given

1994

Geophysical Journal International

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SUMMARY We have analysed broad‐band SKS, SKKS, PKS and S data from 12 stations of the IRIS/IDA network for shear‐wave splitting parameters, fast polarization direction ø and delay time δt. These include several stations in the Former Soviet Union (FSU) (GAR, ARU, KIV, TLY, AAK, OBN), as well as SUR (Sutherland, South Africa), ESK (Eskdalemuir, UK), ALE (Alert, NWT, Canada), NNA (Naña, Peru), PFO (Piñon Flat, CA, USA), and ERM (Erimo, Japan). We compare observations from these stations with those from other nearby stations to gain insight into the mechanisms by which the anisotropy registered by split shear waves may arise. Intraplate comparisons exclude absolute plate motion as an orienting mechanism. Alternatively, the anisotropy may be linked to either fossil deformation within the continental lithosphere or to small‐scale convection. The close correspondence with geologic fabric supports the former interpretation. Commonly, the fast polarization direction is oriented parallel to the deformational axes of compressional tectonic regions. In regions of presently active tectonics, we also see fast polarization directions orthogonal to the maximum horizontal stress in the crust. Deformation localized in the margins of tectonic blocks may account for the spatial splitting variability, and can be facilitated by volatile fluxing of the continental lithosphere during the preceding subduction event.

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Section: Discussionmentioning

confidence: 99%

Shear-wave splitting variation over short spatial scales on continents

Helffrich

Silver

Given

1994

Geophysical Journal International

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“…The distribution of Fe 2+ and Fe 3+ in spinel was inferred from stoichiometry. The mantle fugacity values obtained by this method (Ballhaus, 1993;Mattioli et al, 1989) differ little from those obtained by direct determinations of Fe 3+ .…”

Section: Oxygen Fugacitymentioning

confidence: 63%

Composition of the mantle lithosphere beneath south-central Laurentia: Evidence from peridotite xenoliths, Knippa, Texas

et al. 2011

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Mantle xenoliths in ~83 Ma basanites from south-central Texas provide a rare opportunity to examine the lithospheric mantle beneath southern Laurentia. These peridotites represent lithosphere at the boundary between Mesoproterozoic continental lithosphere and transitional Gulf of Mexico passive margin. Here we report petrographic, mineral, and major element data for 29 spinel peridotite xenoliths from Knippa and use these to characterize the lithospheric mantle beneath south central Texas. The xenoliths comprise spinel-bearing lherzolites and harz burgites with coarse, equigranular textures. Some perido tites contain veins of lizardite . There are no pyroxenites or eclogites . The peridotites contain olivine (Fo 89-92 ), orthopyroxene (En 89-92 ), clinopyroxene (Wo 40-45 En 45-49 Fs 3-5 ), and spinel . Spinel Cr# (Cr/(Cr+Al)) distinguishes lherzolites (Cr# = 0.14-0.21) and harz burgites (Cr# = 0.25-0.36). Mineral and major element compositions indicate that the lherzolites are residues after <10% melt extraction from primitive upper mantle and the harzburgites formed by <15% melt extraction. Calculated oxygen fugacities indicate equilibration of the harzburgites at -1 to +0.61 and lherzolites at 0 to -2.6 log units with respect to fayalite-magnetite-quartz (FMQ) buffer, simi lar to lightly metasomatized spinel perido tites elsewhere. The degree of melt depletion and oxidation of the Knippa peridotites are consistent with present data sets for slightly metasomatized lithospheric mantle and/or backarc samples rather than forearc settings. Equilibration temperatures range from 824 to 1058 °C (mean= 916 °C), calculated at reference pressure of 2.0 GPa. Calculated mean seismic velocities Vs = 4.44 km/sec and Vp =7.87 km/sec show no systematic difference between lherzolites and harz burgites, and agree with present geophysical measure ments of upper mantle velocity beneath Texas. The seismic velocities calculated for these samples will provide important constraints for interpretation of EarthScope and other geophysical data sets.

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“…In comparison, the studied megacrysts and kaersutite sample Fr-12 from the Massif Central, France (Dyar et al 1993) are among the most ferricrich compositions recorded. Mattioli et al (1989) suggested that patent metasomatism, which introduces ferric-rich amphibole, might lead to greater enrichment of bulk Fe 3+ and an apparent greater metasomatic redox effect. Redox conditions (f O 2 and Fe 3+ /FeO tot ) determine the stability of C-O-H-S fl uid and solid phases in the mantle.…”

Section: Oxygen Fugacitymentioning

confidence: 99%

Mossbauer characterization of upper mantle ferrikaersutite

Nasir

Al-Rawas

2006

American Mineralogist

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Mössbauer spectroscopy, H 2 O, and microprobe analysis techniques have been used to study upper mantle ferrikaersutite megacrysts from the scoria cones of the Ash Sham alkaline volcanic fi eld, northeastern part of the Arabian plate. Mössbauer spectra, collected at 298 K, indicate that the kaersutites are highly oxidized and all iron occurs as Fe 3+ . Two components were detected within the Fe 3+ quadrupole splitting distribution of the C-type sites and were assigned to M1 and M2-3 sites. The quadrupole splitting (QS) varies between 0.73-0.87 mm/s (Fe 3+ M1) and 1.28-1.45 mm/s (Fe 3+ M2-3). The kaersutite has a large oxy component in the amphibole OH-site (1.49-1.85 O 2-apfu) similar to the mantle-derived kaersutites. The very high ferric concentration in the kaersutites would suggest crystallization from a relatively oxidizing magma, perhaps with f O 2 close to the fayalite-magnetitequartz (FMQ), and may be a function of the high Fe 3+ /Fe tot of the metasomatic fl uid that crystallized these amphiboles.

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Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Cited by 65 publications

References 61 publications

Shear-wave splitting variation over short spatial scales on continents

Shear-wave splitting variation over short spatial scales on continents

Composition of the mantle lithosphere beneath south-central Laurentia: Evidence from peridotite xenoliths, Knippa, Texas

Mossbauer characterization of upper mantle ferrikaersutite

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