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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.

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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
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URLURL TypeDescription DOIArticle
Wernicke, B. P.0000-0002-7659-8358
Farley, K. A.0000-0002-7846-7546
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
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Caltech Tectonics ObservatoryUNSPECIFIED
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Caltech Tectonics Observatory64
Issue or Number:5
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ID Code:20810
Deposited By: Tony Diaz
Deposited On:16 Nov 2010 00:07
Last Modified:03 Mar 2020 13:01

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