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Direct measurement of neon production rates by (α,n) reactions in minerals

Cox, Stephen E. and Farley, Kenneth A. and Cherniak, Daniele J. (2015) Direct measurement of neon production rates by (α,n) reactions in minerals. Geochimica et Cosmochimica Acta, 148 . pp. 130-144. ISSN 0016-7037.

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The production of nucleogenic neon from alpha particle capture by ^(18)O and ^(19)F offers a potential chronometer sensitive to temperatures higher than the more widely used (U-Th)/He chronometer. The accuracy depends on the cross sections and the calculated stopping power for alpha particles in the mineral being studied. Published ^(18)O(α,n)^(21)Ne production rates are in poor agreement and were calculated from contradictory cross sections, and therefore demand experimental verification. Similarly, the stopping powers for alpha particles are calculated from SRIM (Stopping Range of Ions in Matter software) based on a limited experimental dataset. To address these issues we used a particle accelerator to implant alpha particles at precisely known energies into slabs of synthetic quartz (SiO_2) and barium tungstate (BaWO_4) to measure ^(21)Ne production from capture by ^(18)O. Within experimental uncertainties the observed ^(21)Ne production rates compare favorably to our predictions using published cross sections and stopping powers, indicating that ages calculated using these quantities are accurate at the ∼3% level. In addition, we measured the ^(22)Ne/^(21)Ne ratio and (U-Th)/He and (U-Th)/Ne ages of Durango fluorapatite, which is an important model system for this work because it contains both oxygen and fluorine. Finally, we present ^(21)Ne/^4He production rate ratios for a variety of minerals of geochemical interest along with software for calculating neon production rates and (U-Th)/Ne ages.

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Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2014 Elsevier B. V. Received 2 April 2014, Accepted 27 August 2014, Available online 21 September 2014. We thank Don Burnett for extensive discussion about nuclear chemistry and implantation techniques. We also thank Cécile Gautheron and Samuel Niedermann for their thoughtful signed reviews, as well as an anonymous reviewer for a third review, and we thank Associate Editor Pete Burnard for his attentive handling of the manuscript. This research was supported by the National Science Foundation through grant NSF-EAR-1144500 to KAF and through a Graduate Research Fellowship to SEC.
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NSF Graduate Research FellowshipUNSPECIFIED
Subject Keywords:Noble gas; Geochronometry; Neon; (U-Th)/Ne; Nucleogenic
Record Number:CaltechAUTHORS:20140929-123551053
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Official Citation:Stephen E. Cox, Kenneth A. Farley, Daniele J. Cherniak, Direct measurement of neon production rates by (α,n) reactions in minerals, Geochimica et Cosmochimica Acta, Volume 148, 1 January 2015, Pages 130-144, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50098
Deposited By: Ruth Sustaita
Deposited On:29 Sep 2014 21:05
Last Modified:03 Mar 2020 13:01

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