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Boron concentrations in carbonaceous chondrites

Weller, Martha Riherd and Furst, Marian and Tombrello, T. A. and Burnett, D. S. (1978) Boron concentrations in carbonaceous chondrites. Geochimica et Cosmochimica Acta, 42 (7). pp. 999-1009. ISSN 0016-7037. https://resolver.caltech.edu/CaltechAUTHORS:20150211-124825676

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Abstract

We have analyzed B in carbonaceous chondrites in order to clarify a factor of 100 difference between the solar system B abundance derived from the solar photosphere and that inferred from previous meteorite data. Consistent results were obtained from two instrumental methods for B analysis: (a) counting of the high energy betas from ^(12)B produced by the ^(11)B(d,p) reaction, and (b) measurement of particle track densities from ^(10)B(n,α)^7Li in a plastic track detector affixed to a homogenized meteorite sample. Contamination is a major problem in B analyses, but extensive testing showed that our results were not seriously affected. Our B concentrations are typically 1–2 ppm and are a factor of 2–6 lower than previous carbonaceous chondrite measurements. Our data for the Cl chondrites Ivuna and Orgueil would indicate a solar system B/Si atomic abundance ratio of 58 × 10^(−6), but this is still a factor of 2–10 higher than the photospheric estimates. It may be that B is depleted in the sun by thermonuclear processes; however, the similarity of photospheric and meteoritic Be abundances is a problem for this point of view. Alternatively, B may be enhanced in carbonaceous chondrites, but this would make B a cosmochemically unique element. A mm-sized (Fe,Mn,Mg)CO_3 crystal from Orgueil shows no B enrichment. We find ^(10)B ≤ 10^(16) atoms/g in two Allende fine-grained inclusions suggesting that B is not a refractory element under solar nebula conditions. This ^(10)B limit, when taken as a limit on ^(10)Be when the inclusion formed, puts constraints on the possibility of a solar system synthesis of ^(26)Al. For a proton spectrum of E^(−a), a must be ≥ 3 if a solar gas is irradiated or a ≥1.5 if dust of solar composition is irradiated.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0016-7037(78)90289-2DOIArticle
http://www.sciencedirect.com/science/article/pii/0016703778902892PublisherArticle
ORCID:
AuthorORCID
Burnett, D. S.0000-0001-9521-8675
Additional Information:© 1978 Published by Elsevier Ltd. Received 26 October 1977; accepted in revised form 24 February 1978. Meteorite samples for this study were generously supplied by R. CLARKE (U.S. National Museum), E. OLSEN (Field Museum, Chicago), C. MOORE (Arizona State), G. J. WASSERBURG (Caltech) and J. WASSON (U.C.L.A.). We profited greatly from a discussion with D. HEYMANN on ^(10)Be production. The co-operation of the U.C.L.A. Nuclear Energy Laboratory in arranging reactor irradiations is acknowledged. This work was supported by NSF Grants EAR 76-84402 (D. S. Burnett) and PHY 76-83685 (T. Tombrello).
Funders:
Funding AgencyGrant Number
NSFEAR 76-84402
NSFPHY 76-83685
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences2983
Issue or Number:7
Record Number:CaltechAUTHORS:20150211-124825676
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150211-124825676
Official Citation:Martha Riherd Weller, Marian Furst, T.A. Tombrello, D.S. Burnett, Boron concentrations in carbonaceous chondrites, Geochimica et Cosmochimica Acta, Volume 42, Issue 7, July 1978, Pages 999-1009, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(78)90289-2. (http://www.sciencedirect.com/science/article/pii/0016703778902892)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:54730
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:11 Feb 2015 21:54
Last Modified:09 Mar 2020 13:18

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