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Radiation damage control on apatite (U-Th)/He dates from the Grand Canyon region, Colorado Plateau

Flowers, R. M. and Shuster, D. L. and Wernicke, B. P. and Farley, K. A. (2007) Radiation damage control on apatite (U-Th)/He dates from the Grand Canyon region, Colorado Plateau. Geology, 35 (5). pp. 447-450. ISSN 0091-7613. http://resolver.caltech.edu/CaltechAUTHORS:20101115-112300013

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Abstract

Individual detrital apatite grains from the Esplanade, Coconino, and Moenkopi Formations in the Grand Canyon region of the Colorado Plateau yield (U-Th)/He dates from 104 to 5 Ma. The range of dates within each unit far exceeds analytical uncertainty, but correlates with both He concentration [He] and effective U concentration [eU]. These dates are all significantly younger than the sandstone units, indicating partial to complete He loss following deposition. Recently published laboratory diffusion data suggest that He retentivity in apatite increases with radiation damage. Forward models predict that the consequences of this effect will be manifested most clearly as a correlation between (U-Th)/He dates and the [He] and [eU] in suites of apatites that (1) are characterized by a large span of [eU], and (2) had thermal histories in which sufficient time elapsed for the apatite He diffusion kinetics to diverge prior to reheating and partial resetting. Apatites in the sedimentary units investigated fit these cri teria. Using geologically reasonable deposition, burial, and unroofing histories, simulations that include the effect of radiation damage on apatite He retentivity can reproduce the observed distributions of apatite dates and correlations with parent and daughter concentrations. These results suggest that a span of (U-Th)/He dates positively correlated with [eU] may provide important information regarding a sample's thermal history.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1130/G23471A.1 DOIArticle
http://geology.geoscienceworld.org/cgi/content/abstract/35/5/447PublisherArticle
http://geology.gsapubs.org/content/35/5/447PublisherArticle
ORCID:
AuthorORCID
Wernicke, B. P.0000-0002-7659-8358
Additional Information:© 2007 Geological Society of America. Manuscript received 22 October 2006. Revised manuscript received 21 December 2006. Manuscript accepted 29 December 2006. This work was supported by The Caltech Tectonics Observatory and National Science Foundation grants EAR-0610115 and EAR-0408526. Constructive reviews by Trevor Dumitru, Shari Kelley, Jon Spencer, and Daniel Stockli helped to clarify the manuscript.
Group:Caltech Tectonics Observatory
Funders:
Funding AgencyGrant Number
Caltech Tectonics ObservatoryUNSPECIFIED
NSFEAR-0610115
NSFEAR-0408526
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Caltech Tectonics Observatory64
Record Number:CaltechAUTHORS:20101115-112300013
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20101115-112300013
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:20810
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:16 Nov 2010 00:07
Last Modified:01 Feb 2017 21:13

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