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Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions
Yuri Amelin,1*Alexander N. Krot,2Ian D. Hutcheon,3Alexander A. Ulyanov4
The lead-lead isochron age of chondrules in the CR
chondrite Acfer 059 is 4564.7 ± 0.6 million years ago (Ma),
whereas thelead isotopic age of calcium-aluminum-rich inclusions
(CAIs) inthe CV chondrite Efremovka is 4567.2 ± 0.6 Ma. This
gives an intervalof 2.5 ± 1.2 million years (My) between
formation of the CV CAIsand the CR chondrules and indicates that CAI-
and chondrule-formingevents lasted for at least 1.3 My. This time
interval is consistentwith a 2- to 3-My age difference between CR CAIs
and chondrulesinferred from the differences in their initial
26Al/27Al ratios and supports the chronological
significance of the 26Al-26Mg systematics.
1 Department of Earth Sciences, Royal Ontario
Museum, Toronto, ON M5S 2C6, Canada.
2 Hawaii
Institute of Geophysics and Planetology, School of Ocean and Earth
Science and Technology, University of Hawaii, Honolulu, HI 96822, USA.
3 Lawrence Livermore National Laboratory, Livermore,
CA 94451, USA.
4 M. V. Lomonosov Moscow State
University, Moscow 117999, Russia.
*
Present address: Geological Survey of Canada, 601 Booth Street,
Ottawa, ON K1A 0E8, Canada.
To whom correspondence should be addressed. E-mail:
yamelin{at}NRCan.gc.ca
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