Jump to content

Calcium–aluminium-rich inclusion

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Basilicofresco (talk | contribs) at 12:11, 24 July 2011 (+iw). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

CAIs (white specks) in chondrite meteorite in the collection of the American Museum of Natural History

A calcium-aluminium-rich inclusion or Ca-Al-rich Inclusion (CAI) is a submillimeter to centimeter-sized light-colored calcium- and aluminium-rich inclusion found in carbonaceous chondrite meteorites. They are among the oldest substances in the solar system, forming approximately 4567 to 4571 Ma.

Description

CAIs consist of minerals that are among the first solids condensed from the cooling protoplanetary disk. The most common and characteristic minerals in CAIs include anorthite, melilite, perovskite, aluminous spinel, hibonite, calcic pyroxene, and forsterite-rich olivine. CAIs were formed at much higher temperatures than the associated chondrules, and may have survived many high-temperature events, whereas most chondrules are the product of a single transient melting event.

The isotopic anomalies of CAIs give valuable clues about the solar system's formation, suggesting that the solar nebula collapsed shortly after a nearby supernova; radiometric dating shows that the CAIs formed about 2 million years before the chondrules formed.

Using lead isotopic data determined on CAIs, an age of 4567.2±0.6 million years can be calculated which can be interpreted as the beginning of the formation of the planetary system.[1] However, due to possible disturbances of the lead isotopic system within the CAIs, this age is possibly only a lower limit of the true age. Also an age of 4571 Ma for CAIs has been given, based on Mn–Cr and Mg–Al isotopic data.[2]

References

  1. ^ Amelin Y., Krot A. N., Hutcheon E. D., and Ulyanov A. A. (2002) Lead isotopic ages of chondrules and calcium-aluminum-rich inclusions Science, 297, 1678-1683.
  2. ^ Gilmour J. (2002) The Solar System's First Clocks Science 297, 1658-1659.

Bibliography

  • MacPherson, G. J. (2004) Calcium-aluminum-rich inclusions in chondritic meteorites. In Treatise on Geochemistry, Volume I, Meteorites, Comets, and Planets, A. M. Davis, edt., Elsevier, New York, p. 201-246. ISBN 0-08-043751-6
  • Krot, A. N. (September 2002) Dating the Earliest Solids in our Solar System. Planetary Science Research Discoveries. http://www.psrd.hawaii.edu/Sept02/isotopicAges.html
  • Shukolyukov A., Lugmair G.W. (2002) Chronology of Asteroid Accretion and Differentiation 687-695, in Asterois III, Bottke W.F., Cellino A., Paolicchi P., Binzel R.P., eds., University of Arizona Press (2002), ISBN 0-8165-2281-2
Retrieved from "https://en.wikipedia.org/w/index.php?title=Calcium–aluminium-rich_inclusion&oldid=441161367"