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Amoeboid olivine aggregates in the Allende meteorite
- Source :
- Geochimica et Cosmochimica Acta. 40:149-155
- Publication Year :
- 1976
- Publisher :
- Elsevier BV, 1976.
-
Abstract
- Greyish-brown irregularly-shaped aggregates composed predominantly of olivine make up nearly 2% of the Allende meteorite by volume. Many of the aggregates are constructed of subspherical lumps of micron-sized crystals of olivine, pyroxene, nepheline and sodalite surrounded by coarser-grained olivine. Rarely, anorthite, spinel and perovskite are also present. The olivine ranges in composition from Fo64 to Fo99. Pyroxenes range from aluminous diopside to hedenbergite to very Al-rich and Ti-Al-rich varieties. The nepheline contains 1.6-2.4% K2O and 1.6-5.2% CaO but the sodalite is significantly poorer in these elements. The spinel contains 2.1-13.4% FeO. Textural information and oxygen isotopic data suggest that the aggregates are composed of primary, solid condensates from the solar nebula. The perovskite, spinel and Ti-Al-rich pyroxenes are the remains of high-temperature condensates, but the olivine compositions and the presence of feldspathoids indicate that some of the grains continued to react with the solar nebular vapor in the temperature range 500-900 K.
Details
- ISSN :
- 00167037
- Volume :
- 40
- Database :
- OpenAIRE
- Journal :
- Geochimica et Cosmochimica Acta
- Accession number :
- edsair.doi...........4b97700cee5cb3159d71df7116761223