Origin and history of impact-melt rocks of enstatite chondrite parentage

McCoy, T. J.; Keil, K.; Bogard, D. D.; Garrison, D. H.; Casanova, I.; Lindstrom, M. M.; Brearley, A. J.; Kehm, K.; Nichols, R.; Hohenberg, C. M.

doi:10.1016/0016-7037(94)00231-a

Cited by 72 publications

(75 citation statements)

References 23 publications

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“…Elongate, euhedral enstatite prisms have been reported from the impact-melt rock llafegh 009 (McCoy et al, 1995) and the melt breccia Abee (Rubin and Scott, 1997). However, elongate enstatite in these meteorites ranges up to several hundred micrometers in length, whereas the elongate enstatite crystals in RKPA80259 are no more than 5 0 p m long.…”

Section: Comparison With Impact Melts In Other E and 0 Chondritesmentioning

confidence: 99%

“…Elongate enstatite is also intergrown with kamacite in enstatite chondrite whole-rock shock melts Ilafegh 009 (McCoy et al, 1995) and Y-8404 (Lin and Kimura, 1998) …”

Section: Comparison With Impact Melts In Other E and 0 Chondritesmentioning

confidence: 99%

“…Magnesium contents in enstatite chondrite feldspars rarely exceed 0.1 wt% MgO (Keil, 1968;McCoy et al, 1995;Lin and Kimura, 1998). The mean concentration of MgO in RKPA80259 feldspathic glass exceeds this value by an order of magnitude (Table 4).…”

Section: Feldspathic Glassmentioning

confidence: 99%

“…This identification of multiple liquids in the petrogenesis of RKPA80259 in the absence of a whole-rock silicate melt fills a gap in the continuum of shock effects expected for enstatite chondrites between unmelted E chondrites and largely melted rocks like Abee (Rubin and Scott, 1997), Ilafegh 009 (McCoy et al, 1995), and Yamoto (Y)-8404, and paired specimens (Lin and Kimura, 1998), and has implications for the mechanism by which feldspathic glass forms during shock events. Finally, the textural and compositional observations we use to demonstrate the origin of feldspathic glass by shock melting in RKPA80259 may be of use in studies of other shocked materials.…”

Section: Introductionmentioning

confidence: 99%

“…, 1997). Reported shock effects vary from mild solid-state deformation at low-impact pressures to whole-rock melting and generation of shock-melt breccias at higher impact pressures (McCoy et a/., 1995;Lin and Kimura, 1998). At intermediate pressures, monomineralic melting of feldspar, as opposed to whole-rock melting, is expected on theoretical (StoMer et a/., 1988) and experimental (Schaal and Horz, 1977; Schaal et a/., Ostertag, 1983) grounds but has not previously been described in E chondrites.…”

Section: Introductionmentioning

confidence: 99%

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Formation of feldspathic and metallic melts by shock in enstatite chondrite Reckling Peak A80259

Fagan

Scott

Keil

et al. 2000

Meteorit & Planetary Scien

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Abstract-The enstatite chondrite Reckling Peak (RKP) A80259 contains feldspathic glass, kamacite, troilite, and unusual sets of parallel fine-grained enstatite prisms that formed by rapid cooling of shock melts. Metallic Fe,Ni and troilite occur as spherical inclusions in feldspathic glass, reflecting the immiscible Fe-Ni-S and feldspathic melts generated during the impact. The Fe-Ni-S and feldspathic liquids were injected into fractures in coarse-grained enstatite and cooled rapidly, resulting in thin (110 pm) semicontinuous to discontinuous veins and inclusion trails in host enstatite. Whole-rock melt veins characteristic of heavily shocked ordinary chondrites are conspicuously absent. Raman spectroscopy shows that the feldspathic material is a glass. Elevated MgO and Si02 contents of the glass indicate that some enstatite and silica were incorporated in the feldspathic melt. Metallic Fe,Ni globules are enclosed by sulfide and exhibit Nienrichment along their margins characteristic of rapid crystallization from a Fe-Ni-S liquid. Metal enclosed by sulfide is higher in Si and P than metal in feldspathic glass and enstatite, possibly indicating lower 0 fugacities in metal/sulfide than in silicate domains. Fine-grained, elongate enstatite prisms in troilite or feldspathic glass crystallized from local pyroxene melts that formed along precursor grain boundaries, but most of the enstatite in the target rock remained solid during the impact and occurs as deformed, coarsegrained crystals with lower CaO, A1203, and FeO than the fine-grained enstatite. Reckling Peak A80259 represents an intermediate stage of shock melting between unmelted E chondrites and whole-rock shock melts and melt breccias documented by previous workers. The shock petrogenesis of RKPA80259 reflects the extensive impact processing of the enstatite chondrite parent bodies relative to those of other chondrite types.

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Section: Comparison With Impact Melts In Other E and 0 Chondritesmentioning

confidence: 99%

“…Elongate enstatite is also intergrown with kamacite in enstatite chondrite whole-rock shock melts Ilafegh 009 (McCoy et al, 1995) and Y-8404 (Lin and Kimura, 1998) …”

Section: Comparison With Impact Melts In Other E and 0 Chondritesmentioning

confidence: 99%

Section: Feldspathic Glassmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation of feldspathic and metallic melts by shock in enstatite chondrite Reckling Peak A80259

Fagan

Scott

Keil

et al. 2000

Meteorit & Planetary Scien

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Origin of Halogens and Nitrogen in Enstatite Chondrites

Rubin

Choi

2009

Earth Moon Planet

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The EH and EL enstatite chondrites are the most reduced chondrite groups, having formed in nebular regions where the gas may have had high C/O and/or pH 2 /pH 2 O ratios. Enstatite chondrites (particularly EH) have higher CI-and Mg-normalized abundances of halogens (especially F and Cl) and nitrogen than ordinary chondrites and most groups of carbonaceous chondrites. Even relative to CI chondrites, EH and EL chondrites are enriched in F. We have found that literature values for the halogen abundance ratios in EH and EL chondrites are strongly correlated with the electronegativities of the individual halogens. We suggest that the most reactive halogens were the most efficient at forming compounds (e.g., halides) that were incorporated into EH-chondrite precursor materials. It seems plausible that, under the more-oxidizing conditions pertaining to the other chondrite groups, a larger fraction of the halogens remained in the gas.

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Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities

et al. 2020

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Origin and history of impact-melt rocks of enstatite chondrite parentage

Cited by 72 publications

References 23 publications

Formation of feldspathic and metallic melts by shock in enstatite chondrite Reckling Peak A80259

Formation of feldspathic and metallic melts by shock in enstatite chondrite Reckling Peak A80259

Origin of Halogens and Nitrogen in Enstatite Chondrites

Geochemical Constraints on the Origin of the Moon and Preservation of Ancient Terrestrial Heterogeneities

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