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SmNd systematics of a silicate inclusion in the Caddo IAB iron meteorite
We report the first SmNd data from an iron meteorite silicate inclusion. Mineral separates from an inclusion in the Caddo IAB iron define a 147Sm 143Nd age of 4.53±0.02 Ga, and an initial 146Sm 144Sm of 0.0086±0.0021. A plagioclase separate from the inclusion yields the lowest 142Nd 144Nd ratio me...
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Published in: | Earth and planetary science letters 1996-09, Vol.143 (1), p.1-12 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | We report the first SmNd data from an iron meteorite silicate inclusion. Mineral separates from an inclusion in the Caddo IAB iron define a
147Sm
143Nd age of 4.53±0.02 Ga, and an initial
146Sm
144Sm
of 0.0086±0.0021. A plagioclase separate from the inclusion yields the lowest
142Nd
144Nd
ratio measured to date, which provides an absolute maximum initial solar sysem
ϵ
142 of −2.1 ± 0.4. When the
146Sm
142Nd data are combined with the
147Sm
143Nd data, we obtain our preferred initial solar system
ϵ
142 value of −3.2 ϵu, which corresponds to an initial
146Sm
144Sm
of 0.009. Rare earth element data from the Caddo silicate inclusion suggest that it was derived by partial melting of a chondritic source prior to incorporation into the metal. Therefore, differentiation of the silicate portion of the parent body must have started approximately within the first 30 Ma of solar system history. The data reported here clearly show that IAB meteorites preserve a record of very early planetary differentiation processes. Modeling of element diffusion indicates that, if the silicate material was incorporated into its FeNi host at a time much later than 4.53 Ga, then the mixing must have taken place at shallow levels (i.e., < 50 m) in the parent body, in order to preserve the SmNd systematics. It is more likely that incorporation of the silicate took place at depths greater than 2 km, and that it occurred within the first ∼ 30 Ma of solar system history. This is consistent with estimates of cooling rates determined for IAB irons. |
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ISSN: | 0012-821X 1385-013X |
DOI: | 10.1016/0012-821X(96)00124-0 |