Fe/Mg–Fe/Mn relations of meteorites and primary heterogeneity of primitive achondrite parent bodies

Goodrich, C. A.; Delaney, J. S.

doi:10.1016/s0016-7037(99)00107-6

Cited by 106 publications

(107 citation statements)

References 56 publications

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“…The Fe/Mg versus Fe/Mn trend of the olivine-pigeonite ureilites, which is characterized by nearconstant, chondritic Mn/Mg ration (Fig. 6) suggests that they are residues (from <30% melting of material with chondritic Mn/Mg ratio) and are related to one another principally by various degrees of reduction of common precursor material (Goodrich and Delaney 2000). This reduction relationship is thought to be due to carbon redox control, or smelting (Fig.…”

Section: Structure Of the Ureilite Parent Bodymentioning

confidence: 99%

Northwest Africa 1500: Plagioclase-bearing monomict ureilite or ungrouped achondrite?

Goodrich

Wlotzka

Ross

et al. 2006

Meteoritics &Amp; Planetary Science

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Abstract-Northwest Africa (NWA) 1500 is an ultramafic meteorite dominated by coarse (∼100-500 μm) olivine (95-96%), augite (2-3%), and chromite (0.6-1.6%) in an equilibrated texture. Plagioclase (0.7-1.8%) occurs as poikilitic grains (up to ∼3 mm) in vein-like areas that have concentrations of augite and minor orthopyroxene. Other phases are Cl-apatite, metal, sulfide, and graphite. Olivine ranges from Fo 65-73, with a strong peak at Fo 68-69. Most grains are reversezoned, and also have ∼10-30 μm reduction rims. In terms of its dominant mineralogy and texture, NWA 1500 resembles the majority of monomict ureilites. However, it is more ferroan than known ureilites (Fo ≥75) and other mineral compositional parameters are out of the ureilite range as well. Furthermore, neither apatite nor plagioclase have ever been observed, and chromite is rare in monomict ureilites. Nevertheless, this meteorite may be petrologically related to the rare augite-bearing ureilites and represent a previously unsampled part of the ureilite parent body (UPB). The Mn/Mg ratio of its olivine and textural features of its pyroxenes are consistent with this interpretation. However, its petrogenesis differs from that of known augitebearing ureilites in that: 1) it formed under more oxidized conditions; 2) plagioclase appeared before orthopyroxene in its crystallization sequence; and 3) it equilibrated to significantly lower temperatures (800-1000 °C, from two-pyroxene and olivine-chromite thermometry). Formation under more oxidized conditions and the appearance of plagioclase before orthopyroxene could be explained if it formed at a greater depth on the UPB than previously sampled. However, its significantly different thermal history (compared to ureilites) may more plausibly be explained if it formed on a different parent body. This conclusion is consistent with its oxygen isotopic composition, which suggests that it is an ungrouped achondrite. Nevertheless, the parent body of NWA 1500 may have been compositionally and petrologically similar to the UPB, and may have had a similar differentiation history.

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Section: Structure Of the Ureilite Parent Bodymentioning

confidence: 99%

Northwest Africa 1500: Plagioclase-bearing monomict ureilite or ungrouped achondrite?

Goodrich

Wlotzka

Ross

et al. 2006

Meteoritics &Amp; Planetary Science

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“…4e) are major lines of evidence indicating that these three phases crystallized from a melt. In contrast, the olivine inclusions are characterized by well-developed 120° triple junction when in Goodrich and Delaney (2000) and Goodrich and Righter (2000). b) Fa versus Fs in olivine and orthopyroxene, respectively.…”

Section: Petrogenetic Constraints From Petrographic Analysesmentioning

confidence: 99%

Frontier Mountain 93001: A coarse-grained, enstatite-augite-oligoclase-rich, igneous rock from the acapulcoite-lodranite parent asteroid

Folco

D’Orazio

Burroni

2006

Meteoritics &Amp; Planetary Science

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Despite some similarities, the silicate igneous component of FRO 93001 (i.e., the pyroxeneplagioclase mineral assemblage) differs in being coarser-grained and containing abundant enstatite. Melting-crystallization modeling suggests that FRO 93001 formed through high-degree partial melting (≥35 wt%; namely, ≥15 wt% silicate melting and ~20 wt% metal melting) of an acapulcoitic source rock, or its chondritic precursor, at temperatures ≥1200 °C, under reducing conditions. The resulting magnesium-rich silicate melt then underwent equilibrium crystallization; prior to complete crystallization at ~1040 °C, it incorporated lodranitic xenoliths.FRO 93001 is the highest-temperature melt from the AL parent-body so far available in laboratory. The fact that FRO 93001 could form by partial melting and crystallization under equilibrium conditions, coupled with the lack of quench-textures and evidence for shock deformation in the xenoliths, suggests that FRO 93001 is a magmatic rock produced by endogenic heating rather than impact melting.

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“…Iron-Manganese-Magnesium Relations Goodrich and Delaney (2000) have shown that the groups of meteorites commonly classified as primitive achondrites can be characterized by MnlMg (MnO/MgO) ratios, of either their bulk compositions or their olivine.…”

Section: Olivine and Chromite Compositionsmentioning

confidence: 99%

“…Ureilites, lodranites, and winonaites/IAB silicate inclusions each show a near-constant MnO/MgO ratio over large ranges of FeO/MgO ratio (Goodrich et al, 1987;Goodrich, 1998b;Goodrich and Delaney, 2000). distinction arises primarily because the primitive achondrites are residues from low degrees of melting (less than -30%) of materials with chondritic MnO/MgO ratios and heterogeneous FeO contents; whereas the HEDs, SNCs, and lunar basalts represent melts and the products of melts (cumulates and fractionated melts).…”

Section: Olivine and Chromite Compositionsmentioning

confidence: 99%

Petrology of unique achondrite Queen Alexandra Range 93148: A piece of the pallasite (howardite‐eucrite‐diogenite?) parent body?

Goodrich¹,

Righter²

2000

Meteorit & Planetary Scien

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Abstract-Queen Alexandra Range (QUE) 93148 is a small (1.1 g) olivine-rich achondrite (mg 86) that contains variable amounts of orthopyroxene (mg 87) and kamacite (6.7 wt% Ni), with minor augite. Olivine in QUE 93 148 contains an unusual suite of inclusions: (1) 5 x 100 p m sized lamellae with a CaO-and Cr203-rich (-10 and 22 wt%, respectively) composition that may represent a submicrometer-scale intergrowth of chromite and pyroxene(s); (2) 75 x 500 p m sized lamellar symplectites composed of chromite and two pyroxenes, with minor metal; (3) 15-20 p m sized, irregularly-shaped symplectites composed of chromite and pyroxene(s); (4) 100-150 p m sized, elliptical inclusions composed of chromite, two pyroxenes, metal, troilite, and rare whitlockite. Type 1, 2, and 3 inclusions probably formed by exsolution from the host olivine during slow cooling, whereas type 4 more likely resulted from early entrapment of silicate and metallic melts followed by closed-system oxidation.Queen Alexandra Range 93 148 can be distinguished from most other olivine-rich achondrites (ureilites, winonaites, lodranites, acapulcoites, brachinites, Eagle-Station-type pallasites, and pyroxene pallasites), as well as from mesosiderites, by some or all of the following properties: 0-isotopic composition, Fe-Mn-Mg relations of olivine, CaO and Cr2O3 contents of olivine, orthopyroxene compositions, molar Cr/(Cr + Al) ratios of chromite, metal composition, texture, and the presence of the inclusions. In terms of many of these properties, it shows an affinity to main-group pallasites. Nevertheless, it cannot be identified as belonging to this group. Meteorite QUE 93 148 appears to be a unique achondrite. Possibly it should be considered to be a pyroxene pallasite that is genetically related to main-group pallasites. Alternatively, it may be derived from the mantle of the pallasite (howardite-eucrite4iogenite?) parent body.

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Fe/Mg–Fe/Mn relations of meteorites and primary heterogeneity of primitive achondrite parent bodies

Cited by 106 publications

References 56 publications

Northwest Africa 1500: Plagioclase-bearing monomict ureilite or ungrouped achondrite?

Northwest Africa 1500: Plagioclase-bearing monomict ureilite or ungrouped achondrite?

Frontier Mountain 93001: A coarse-grained, enstatite-augite-oligoclase-rich, igneous rock from the acapulcoite-lodranite parent asteroid

Petrology of unique achondrite Queen Alexandra Range 93148: A piece of the pallasite (howardite‐eucrite‐diogenite?) parent body?

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