P-T-oxygen fugacity relations in the system Fe-O-MgO-SiO 2

Speidel, D. H.; Nafziger, R. H.

doi:10.2475/ajs.266.5.361

Cited by 26 publications

(6 citation statements)

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“…Graphite reduction of metal is a high temperature process, typically achieved at temperatures >1200°C or possibly near 1050°C in an asteroidal setting (e.g., Schmidt and Avery, 1978;Kracher, 1985;Walker and Grove, 1993). Reduction of olivine in olivine-silica-metal assemblages to lower Fa contents during heating from 1100°C to 1300°C has also been shown (Mueller, 1963;Speidel and Nafziger, 1968). Reduction by graphite near peak metamorphic temperature has previously been suggested for the IAB iron meteorites (Wlotzka and Jarosewich, 1977;Kracher, 1985).…”

Section: Oxidation Historymentioning

confidence: 92%

Relict chondrules in primitive achondrites: Remnants from their precursor parent bodies

McCoy

Gardner-Vandy

2017

Geochimica et Cosmochimica Acta

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We studied the petrography, analyzed the chemical compositions, constrained the closure temperatures (via geothermometry), and determined the oxidation states of relict chondrules in Campo del Cielo (IAB iron meteorite), Graves Nunataks (GRA) 98028 (acapulcoite), and Netschaëvo (IIE iron meteorite) to constrain their formation conditions and investigate links to known meteorite groups. Despite having been thermally metamorphosed, mineral phases within relict chondrules retain information about their precursor compositions. The sizes and textures of relict chondrules, and silicate and chromite compositions indicate that Campo del Cielo, GRA 98028, and Netschaëvo had distinct parent bodies that were similar to, but different from, known chondrite groups. To determine the utility of relict chondrule sizes in thermally metamorphosed meteorites, we determined the chondrule size distributions in the LL chondrites Semarkona (LL3.00), Soko-Banja (LL4), Siena (LL5), and Saint-Séverin (LL6), and the H chondrites Clovis (no. 1) (H3.6), Kesen (H4), Arbol Solo (H5), and Estacado (H6). As expected, mean chondrule diameters increase with degree of thermal metamorphism. We find that Campo del Cielo and GRA 98028 were reduced during thermal metamorphism, consistent with previous studies, indicating that their precursors were initially more FeO-rich than their current compositions. In contrast to previous studies, we find no evidence for reduction of silicates in Netschaëvo. Normal zoning of olivine in Netschaëvo is consistent with crystallization and suggests its silicates are near their primary FeO-contents. The presence of elongated chromite grains along olivine grain boundaries in Netschaëvo indicates formation during thermal metamorphism under oxidizing conditions. Due to the absence of reduction and the composition of chromite being distinct from that of metamorphosed H chondrites, we conclude that Netschaëvo, and by extension the IIE iron meteorites, are not from the H chondrite parent body.

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Section: Oxidation Historymentioning

confidence: 92%

Relict chondrules in primitive achondrites: Remnants from their precursor parent bodies

McCoy

Gardner-Vandy

2017

Geochimica et Cosmochimica Acta

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“…Oxygen fugacity is an important intensive variable which controls the ferric-ferrous equilibrium in many magmas (Fudali, 1965;Carmichael and Nicholls, 1967). Furthermore, oxygen fugacity can determine the compositions of crystallizing phases in both magnetite-bearing assemblages and metallic iron-bearing assemblages in the system Fe-O-MgO-Si0 2 (Speidel and Nafziger, 1968). Thus, oxygen fugacity can control not only the phases present but the composition of these phases as well.…”

mentioning

confidence: 99%

Gaseous Buffering for the Control of Oxygen Fugacity at One Atmosphere

Nafziger¹,

Ulmer²,

Woermann³

1971

Research Techniques for High Pressure and High Temperature

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“…High oxygen fugacity and early crystallization of titanomagnetites may also be responsible for reverse zoning in the character of the Fe-Mg ratio in silicates at lower temperatures [Mar tynov and Chubarov, 1982]. There is also some experi mental evidence [Speidel and Nofriger, 1968] for rising MgO content in olivine in paragenesis with magnetite with increasing and decreasing temperature. On the basis of experimental data the concept was formed [Ringwood, 1975] that in the case of high water content in andesite magma melts, more calcic plagio clases crystallize compared with crystallization in anhy drous conditions.…”

Section: The Mineral Compositions Of Volcanic Rocks As An Indication mentioning

confidence: 99%

The evolutionary stages and petrology of the kekuknai volcanic massif reflecting the magmatism in the backarc zone of the kuril-kamchatka island arc system. Part II. petrologic and mineralogical features, petrogenesis model

Колосков

Flerov

Perepelov

et al. 2013

J. Volcanolog. Seismol.

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P-T-oxygen fugacity relations in the system Fe-O-MgO-SiO 2

Cited by 26 publications

References 0 publications

Relict chondrules in primitive achondrites: Remnants from their precursor parent bodies

Relict chondrules in primitive achondrites: Remnants from their precursor parent bodies

Gaseous Buffering for the Control of Oxygen Fugacity at One Atmosphere

The evolutionary stages and petrology of the kekuknai volcanic massif reflecting the magmatism in the backarc zone of the kuril-kamchatka island arc system. Part II. petrologic and mineralogical features, petrogenesis model

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