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The identification of early condensates from the solar nebula

Gray, C. M. and Papanastassiou, D. A. and Wasserburg, G. J. (1973) The identification of early condensates from the solar nebula. Icarus, 20 (2). pp. 213-239. ISSN 0019-1035. doi:10.1016/0019-1035(73)90052-3.

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Calcium-aluminum-rich chondrules which are highly deficient in alkalis were extracted from the carbonaceous chondrite Allende and yield a range of compositions with the lowest measured isotopic composition of (⁸⁷Sr/⁸⁶Sr)_(ALL) = 0.69877 ± 0.00002 and identify this material as the earliest known condensate from the solar nebula. Other chondrules suggest the possible presence of even more primitive Sr in this meteorite. This result also shows that some chondritic material formed very near the earliest part of the condensation sequence. Using alkali-deficient planetary objects (Moon, basaltic achondrites, Angra dos Reis, Allende), the Sr data indicate a time interval for condensation of 10 m.y. (from ALL to BABI) if condensation occurred in a solar Rb/Sr environment. A variety of alkali-rich olivine chondrules and Ca-Al-rich aggregates from Allende fail to determine an isochron and indicate that the element distribution in this meteorite was disturbed later than 3.6ae, possibly recently, in a cometary nucleus. This disturbance requires that the determination of initial ⁸⁷Sr/⁸⁶Sr be done on essentially Rb-free phases. Strontium data from equilibrated chondrites and from an iron meteorite establish an interval for metamorphism or differentiation in protoplanetary objects which followed the condensation process by ≈80 mm.y. The chronology for condensation and early planetary evolution obtained for Sr is in disagreement with the ¹²⁹I chronology but can be brought into agreement, if it is assumed that the high temperature iodine containing phases have not been affected by the metamorphic events determined by Sr.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:This work was carried out through the support of the National Science Foundation (Grant GP-28027). Samples were obtained within a few weeks after the fall through a joint venture with D. Elston after initial prompting and guidance by Eugene Shoemaker and Elbert King. Some critical samples were provided to us through the generous aid and cooperation of Brian Mason and A. L. Graham i)f the Smithsonian Museum, and bv Elbert King, University of Houston. The sample of Peace River was provided generously by R. E. Folinsbee, The University of Alberta. We are pleased to acknowledge discussion with F. A. Podosek and J. C. Huneke about some of the xenophilic problems.
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Caltech Division of Geological and Planetary Sciences2283
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ID Code:117978
Deposited By: Tony Diaz
Deposited On:28 Nov 2022 19:10
Last Modified:28 Nov 2022 19:10

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