Matrix mineralogy of the orgueil CI carbonaceous chondrite

Journal Article · Wed Jun 01 00:00:00 EDT 1988 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(88)90231-1· OSTI ID:5510352

Tomeoka, K; Buseck, P R ^[1]

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1. Arizona State Univ., Tempe (USA)

A petrographic and transmission electron microscopic study of the Orgueil CI carbonaceous chondrite shows that the matrix consists mainly of Fe-bearing, Mg-rich serpentine and smectite (saponite) as well as a poorly crystallized Fe-rich material that contains minor, variable S and Ni; the Fe-rich material is probably ferrihydrite. The ferrihydrite occurs in small particles, and the S and Ni are probably adsorbed on its surfaces. The serpentine and saponite occur in poorly crystallized, fine crystallites that are intimately associated with the ferrihydrite. Coarsely crystallized phyllosilicates occur in clusters relatively free of ferrihydrite. The ferrihydrite is a major matrix constitutent and probably accounts for most of the Fe{sub 3+} as well as the superparamagnetic fraction in the Orgueil matrix. The textures suggest that the fine phyllosilicates resulted from alteration of the coarse phyllosilicates. The alteration probably involved a substantial amount of water and coincided with the period of sulfate vein formation. During the aqueous alteration magnetite grains, disaggregated from framboids, and Fe-(Ni) sulfides were replaces by ferrihydrite. The matrix mineralogy of the Orgueil chondrite suggests that Orgueil experienced considerably different alteration conditions from the CM chondrites. The mineralogical and petrological differences between CI and CM chondrites can not simply be explained as the result of different degrees of aqueous alteration.

• OSTI ID: 5510352
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 52:6; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
CHONDRITES
CHEMICAL COMPOSITION
MINERALOGY
PETROGRAPHY
CARBONACEOUS MATERIALS
GEOCHEMISTRY
GEOLOGIC HISTORY
HYDROTHERMAL ALTERATION
IRON
MAGNESIUM
MAGNETITE
MINERALIZATION
NICKEL
PYRITE
SERPENTINE
SMECTITE
SULFUR
TRANSMISSION ELECTRON MICROSCOPY
ALKALINE EARTH METALS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CHALCOGENIDES
CHEMISTRY
CLAYS
ELECTRON MICROSCOPY
ELEMENTS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
IRON SULFIDES
MATERIALS
METALS
METEORITES
MICROSCOPY
MINERALS
NONMETALS
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STONE METEORITES
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
580400* - Geochemistry- (-1989)
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)