Elemental fractionations among enstatite chondrites

Baedecker, P. A.; Wasson, J. T.

doi:10.1016/0016-7037(75)90013-7

Cited by 123 publications

(75 citation statements)

References 69 publications

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“…According to Kennedy et al, if the iodine isotopic compositions are reflecting real age differences in meteorites whch originated from a common reservoir, h s could be dating the agglomeration of metal and silicate. In this case, the difference in both chemical compositions and I-Xe ages would be consistent with the model of Baedecker and Wasson (1975) in whch agglomeration of the metal-rich EH chondrites would precede that of the silicaterich EL chondrites.…”

Section: Implications For the Origin Of The Eh And El Chondritessupporting

confidence: 60%

Properties of chondrules in EL3 chondrites, comparison with EH3 chondrites, and the implications for the formation of enstatite chondrites

Schneider

Symes

Benoit

et al. 2002

Meteorit & Planetary Scien

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Abstract-The study of chondrules provides information about processes occurring in the early solar system. In order to ascertain to what extent these processes played a role in determining the properties of the enstatite chondrites, the physical and chemical properties of chondrules from three EL3 chondrites and three EH3 chondrites have been examined by optical, cathodoluminescence (CL), and electron microprobe techniques. Properties examined include size, texture, CL, and composition of both individual phases and bulk chondrules. The textures, distribution of textures, and composition of silicates of the EL3 chondrules resemble those of EH3 chondrules. However, the chondrules from the two classes differ in that (1) the size distribution of the EL chondrules is skewed to larger values than EH chondrules, (2) the enstatite in EL chondrules displays varying shades of red CL due to the presence of fine-grained sulfides and metal in the silicates, and (3) the mesostasis of EH chondrules is enriched in Na relative to that of EL chondrules. The similarities between the chondrules of the two classes suggest similar precursor materials, while the differences suggest that there was not a single reservoir of meteoritic chondrules, but that their origin was fairly local. The differences in the size distribution of chondrules in EH and EL chondrites may be explained by aerodynamic and gravitational sorting during accumulation of the meteoric material, while differences in CL and mesostasis properties may reflect differences in formation conditions and cooling rate following chondrule formation. We argue that our observations are consistent with the formation of enstatite chondrites in a thick dynamic regolith on their parent body.

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Section: Implications For the Origin Of The Eh And El Chondritessupporting

confidence: 60%

Properties of chondrules in EL3 chondrites, comparison with EH3 chondrites, and the implications for the formation of enstatite chondrites

Schneider

Symes

Benoit

et al. 2002

Meteorit & Planetary Scien

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“…Two principal models to explain reduction of nebular gas have been proposed: 1) addition of C-rich dust (Larimer and Bartholomay 1979); and 2) removal of oxygen (Baedecker and Wasson 1975). Local fluctuation of these components could explain variation of oxygen fugacity in the reservoir.…”

Section: Reservoir Of Feo-rich Pyroxene Formationmentioning

confidence: 99%

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

Kimura

Hiyagon

Lin

et al. 2003

Meteorit & Planetary Scien

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“…Depleting the water content of a gas, as might be expected sunward of the water condensation front (Morfill, 1985;Stevenson and Lunine, 1988;Cyr et al, 1998), has the effect of increasing the C/O ratio of the gas (e.g., Baedecker and Wasson, 1975). An increase in the C/O ratio has been proposed as the most likely way to create minerals such as CaS and MgS in the solar nebula (e.g., Larimer and Bartholomay, 1979;Lodders and Fegley, 1993).…”

Section: Water Depletionmentioning

confidence: 99%

“…Several models to account for the origin of the enstatite chondrites have been proposed, including: ( I ) condensation with slow nucleation kinetics (Blander, 1971); (2) condensation at high pressures (>I bar) (Herndon and Suess, 1976;Sears, 1980); (3) formation in a region of the nebula with low H20/H2 ratio (Baedecker and Wasson, 1975) or high C/O ratio (Larimer and Bartholomay, 1979;Lodders andFegley, 1993, 1997); (4) increasing the amount of a "tar" component in the nebula (Wood and Hashimoto, 1993); and (5) condensation with partial isolation of solids (Petaev and Wood, 1998). None of these models have successfully replicated the observed modal mineralogy and bulk compositions of type 3 enstatite chondrites.…”

Section: Introductionmentioning

confidence: 99%

A multi‐step model for the origin of E3 (enstatite) chondrites

Hutson¹,

Ruzicka²

2000

Meteorit & Planetary Scien

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Abstract-It appears that the mineralogy and chemical properties of type 3 enstatite chondrites could have been established by fractionation processes (removal of a refractory component, and depletion of water) in the solar nebula, and by equilibration with nebular gas at low-to-intermediate temperatures (approximately 700-950 K). We describe a model for the origin of type 3 enstatite chondrites that for the first time can simultaneously account for the mineral abundances, bulk-chemistry, and phase compositions of these chondrites by the operation of plausible processes in the solar nebula. This model, which assumes a representative nebular gas pressure of 10-5 bar, entails three steps: (1) initial removal of 56% of the equilibrium condensed phases in a system of solar composition at 1270 K; (2) an average loss of 80-85% water vapor in the remaining gas; and (3) two different closure temperatures for the condensed phases. The first step involves a "refractory element fractionation'' and is needed to account for the overall major element composition of enstatite chondrites, assuming an initial system with a solar composition. The second step, water-vapor depletion, is needed to stabilize Si-bearing metal, oldhamite, and niningerite, which are characteristic minerals of the enstatite chondrites. Variations in closure temperatures are suggested by the way in which the bulk chemistry and mineral assemblages of predicted condensates change with temperature, and how these parameters correlate with the observations of enstatite chondrites. In general, most phases in type 3 enstatite chondrites appear to have ceased equilibrating with nebular gas at approximately 900-950 K, except for Fe-metal, which continued to partially react with nebular gas to temperatures as low as -700 K.

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Elemental fractionations among enstatite chondrites

Cited by 123 publications

References 69 publications

Properties of chondrules in EL3 chondrites, comparison with EH3 chondrites, and the implications for the formation of enstatite chondrites

Properties of chondrules in EL3 chondrites, comparison with EH3 chondrites, and the implications for the formation of enstatite chondrites

FeO‐rich silicates in the Sahara 97159 (EH3) enstatite chondrite: Mineralogy, oxygen isotopic compositions, and origin

A multi‐step model for the origin of E3 (enstatite) chondrites

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