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unmelted meteoritic debris in the late pliocene iridium anomaly - evidence for the ocean impact of a nonchondritic asteroidIr-bearing particles have been recovered from two piston cores in the Antarctic Basin in the southeastern Pacific. In core E13-3, the particles closely correspond to the Late Pliocene Ir anomaly and have a fluence of about 100 mg/cm sq. In core E13-4, 120 km to the southwest, the particle fluence is about 4 mg/cm sq. Particles with diameters from 0.5 to 4 mm contain at least 35 percent of the Ir in this horizon. Three types of particles have been identified: (1) vesicular, (2) basaltic, and (3) metal. The vesicular particles appear to be shock-melted debris derived from the oceanic impact of a howarditic asteroid containing a minor metal component. These particles have recrystallized from a melt and impact into the ocean has resulted in the incorporation of Na, K, Cl, and radiogenic Sr from the ocean water target. The basaltic clasts appear to be unmelted fragments of the original asteroid which may have separated from the main body prior to impact. Combined vesicular and basaltic particles are believed to have formed by collisions in the debris cloud. Estimates of the diameter of the projectile range from 100 to 500 m. By many orders of magnitude, this is the most massive achondrite sampled by a single meteorite fall.
Document ID
19850055325
Document Type
Reprint (Version printed in journal)
Authors
Kyte, F. T.
(California, University Los Angeles, CA, United States)
Brownlee, D. E.
(Washington, University Seattle, WA, United States)
Date Acquired
August 12, 2013
Publication Date
May 1, 1985
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 49
ISSN: 0016-7037
Subject Category
LUNAR AND PLANETARY EXPLORATION
Funding Number(s)
CONTRACT_GRANT: NSG-9052
CONTRACT_GRANT: NSF OCE-82-08197
Distribution Limits
Public
Copyright
Other