Extraterrestrial spherules in glacial sediment from the Transantarctic Mountains, Antarctica: Structure, mineralogy, and chemical composition

Journal Article · Sat Apr 01 04:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90039-2· OSTI ID:5127110

Koeberl, C ^[1]; Hagen, E H ^[2]

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1. Univ. of Vienna (Austria) Lunar and Planetary Institute, Houston, TX (USA)
2. Ohio State Univ., Columbus (USA)

Silicate and glassy spherules of probably extraterrestrial origin have been discovered in glacial till from localities in the Beardmore glacier region, Transantarctic Mountains, Antarctica. These spherules are similar in structure, appearance, and composition to spherules found in deep-sea sediments and in Greenland. Most spherules have a shiny and smooth dark surface, while some show a characteristic brickwork pattern composed of intergrown olivine crystals and magnetite dendrites. Several spherules have been sectioned after trace element analysis by INAA. The interiors of the spherules contain olivine crystals of varying size (predominantly of forsteritic composition) set in a glassy Fe-rich and Mg-poor matrix. The matrix contains very fine-grained dendritic magnetite crystals and rare accessory wustite. SEM and microprobe studies show that most of the spherules have not experienced significant weathering. Trace element analyses for individual particles confirm the extraterrestrial nature of the spherules. They have undifferentiated chondritic rare earth element (REE) patterns and are enriched in Ir and other siderophile elements (with Ir contents between 10 and > 1,000 ppb). Some spherules have experienced loss of volatile elements and some differentiation of siderophile elements (e.g., Ni). The Antarctic spherules--which might be micrometeorites that melted during passage through the atmosphere, or ablation spherules--are a significant addition to the collection of extraterrestrial microparticles. Of key importance is their high abundance in the sediment and the fact that they have been concentrated by glacial action.

• OSTI ID: 5127110
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:4; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ABUNDANCE
ALKALINE EARTH METAL COMPOUNDS
AMORPHOUS STATE
ANTARCTIC REGIONS
ANTARCTICA
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
CHONDRITES
CRYSTAL STRUCTURE
ELEMENT ABUNDANCE
GEOCHEMISTRY
GLACIERS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
IRON SILICATES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
MAGNETITE
METEORITES
MINERALOGY
MINERALS
OLIVINE
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
POLAR REGIONS
QUANTITATIVE CHEMICAL ANALYSIS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STONE METEORITES
TRACE AMOUNTS
TRANSITION ELEMENT COMPOUNDS