Redox state of Earth's upper mantle from kimberlitic ilmenites

Haggerty, Stephen E.; Tompkins, Linda A.

doi:10.1038/303295a0

Cited by 95 publications

(21 citation statements)

References 31 publications

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“…We note, however, that both methods suggest that these xenoliths equilibrated near the fayalite-magnetite-quartz buffer at elevated pressure, not near or below the iron-wiistite buffer as indicated by the "intrinsic" /0 2 measurements of Arculus and Delano (1981). In addition, a recent investigation of discrete ilmenite-bearing nodules from kimberlites of western Mrica yields log/0 2 ' s within ± 1 log unit of FMQ over a temperature range of 600° to l200°C (Haggerty and Tompkins 1983). This study also confirms the generally oxidized nature of the shallow upper mantle.…”

Section: Discussionmentioning

confidence: 99%

Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Mattioli¹,

Baker

Rutter

et al. 1989

The Journal of Geology

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We have calculatedf0 2 's and temperatures of various mantle environments worldwide using published analyses of coexisting olivine, orthopyroxene, clinopyroxene, and Fe 3 +-bearing spinel from 280 peridotites. Most calculated /0 2 's fall within ± 2 log units of the Fayalite-Magnetite-Quartz (FMQ) buffer at 15 kbar. Our data set defines a general trend in/Or T space that is not related to FMQ or to other Fe-bearing buffers. Variations in major-element, trace-element, and oxygen isotopic composition of xenoliths correlate with variations in calculated/0 2 • Rare "fertile" xenoliths record/0 2 's close to WM (Wiistite-Magnetite) buffer at 15 kbar and 900°C. Xenoliths with both cryptic and/or modal metasomatic overprinting are generally oxidized relative to xenoliths without evidence of such open system processing. Based on trace element and oxygen isotopic data, the best candidate for the metasomatic agent is a C0 2 -H 2 0-rich fluid. We suggest that metasomatic fluids are derived from oxidized, hydrated material subducted at convergent margins and that this process may have led to progressive oxidation of the earth's upper mantle through much of geologic time. This is consistent with the observation that xenoliths from Hawaii and Tahiti record/0 2 's higher than mantle array's average, as do some xenoliths from the circumpacific region.

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Section: Discussionmentioning

confidence: 99%

Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Mattioli¹,

Baker

Rutter

et al. 1989

The Journal of Geology

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“…6). Haggerty & Tompkins (1983) suggest that the early mantle may well have been reduced, with oxygen fugacities close to those defined by the synthetic oxygen buffer magnetite-wustite (MW), and that some xenolith suites brought to the surface in kimberlites reflect this primitive condition. They consider that, with time, the mantle has become progressively more oxidized, resulting largely from the preferential loss of hydrogen and carbon.…”

Section: Volatile Contents and Redox Statementioning

confidence: 97%

Igneous Petrogenesis

Wilson

2000

329

383

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“…However, an explanation may lie in the systematic variations seen in the redox conditions of terrestrial igneous rocks. On Earth, the oxidation state of a particular suite of rocks correlates strongly with the tectonic environment (31)(32)(33). In particular, redox conditions for all but subduction-related magmas lie between wüstite-magnetite and QFM, whereas magmas crystallizing in the more hydrated subduction terrains are more oxidized and lie between nickel-nickel oxide and magnetitehematite.…”

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confidence: 99%

Redox State of Mars' Upper Mantle and Crust from Eu Anomalies in Shergottite Pyroxenes

Wadhwa

2001

Science

233

240

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The oxidation state of basaltic martian meteorites is determined from the partitioning of europium (Eu) in their pyroxenes. The estimated redox conditions for these samples correlate with their initial neodymium and strontium isotopic compositions. This is interpreted to imply varying degrees of interaction between the basaltic parent melts, derived from a source in the martian mantle, and a crustal component. Thus, the mantle source of these martian basalts may have a redox state close to that of the iron-wüstite buffer, whereas the martian crust may be more oxidized (with a redox state higher than or equal to that of the quartz-fayalite-magnetite buffer). A difference in redox state of more than 3 log units between mantle and crustal reservoirs on Mars could result from oxidation of the crust by a process such as aqueous alteration, together with a subsequent lack of recycling of this oxidized crust through the reduced upper mantle.

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Redox state of Earth's upper mantle from kimberlitic ilmenites

Cited by 95 publications

References 31 publications

Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Upper Mantle Oxygen Fugacity and Its Relationship to Metasomatism

Igneous Petrogenesis

Redox State of Mars' Upper Mantle and Crust from Eu Anomalies in Shergottite Pyroxenes

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