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

R. M. Flowers, D. L. Shuster, B. P. Wernicke and K. A. Farley
Radiation damage control on apatite (U-Th)/He dates from the Grand Canyon region, Colorado Plateau
Geology (Boulder) (May 2007) 35 (5): 447-450


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 criteria. 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.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 35
Serial Issue: 5
Title: Radiation damage control on apatite (U-Th)/He dates from the Grand Canyon region, Colorado Plateau
Affiliation: California Institute of Technology, Division of Geological and Planetary Science, Pasadena, CA, United States
Pages: 447-450
Published: 200705
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 17
Accession Number: 2007-045061
Categories: Geochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2007105
Illustration Description: illus. incl. geol. sketch map
N34°10'00" - N37°00'00", W114°45'00" - W112°34'60"
N34°15'00" - N37°00'00", W113°19'60" - W110°45'00"
Secondary Affiliation: Berkeley Geochronology Center, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200724
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