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He diffusion and (U–Th)/He thermochronometry of zircon: initial results from Fish Canyon Tuff and Gold Butte

Reiners, Peter W. and Farley, Kenneth A. and Hickes, Hunter J. (2002) He diffusion and (U–Th)/He thermochronometry of zircon: initial results from Fish Canyon Tuff and Gold Butte. Tectonophysics, 349 (1-4). pp. 297-308. ISSN 0040-1951. https://resolver.caltech.edu/CaltechAUTHORS:20121121-093240494

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Abstract

To evaluate the potential of (U–Th)/He geochronometry and thermochronometry of zircon, we measured He diffusion characteristics in zircons from a range of quickly and slowly cooled samples, (U–Th)/He ages of zircons from the quickly cooled Fish Canyon Tuff, and age-paleodepth relationships for samples from 15 to 18 km thick crustal section of the Gold Butte block, Nevada. (U–Th)/He ages of zircons from the Fish Canyon Tuff are consistent with accepted ages for this tuff, indicating that the method can provide accurate ages for quickly cooled samples. Temperature-dependent He release from zircon is not consistent with thermally activated volume diffusion from a single domain. Instead, in most samples apparent He diffusivity decreases and activation energy (E_a) increases as cycled step-heating experiments proceed. This pattern may indicate a range of diffusion domains with distinct sizes and possibly other characteristics. Alternatively, it may be the result of ongoing annealing of radiation damage during the experiment. From these data, we tentatively suggest that the minimum E_a for He diffusion in zircon is about 44 kcal/mol, and the minimum closure temperature (T_c, for a cooling rate of 10 °C/myr) is about 190 °C. Age–paleodepth relationships from the Gold Butte block suggest that the base of the zircon He partial retention zone is at pre-exhumation depths of about 9.5–11 km. Together with constraints from other thermochronometers and a geothermal gradient derived from them in this location, the age–depth profile suggests a He T_c of about 200 °C for zircon, in reasonable agreement with our interpretation of the laboratory measurements. A major unresolved question is how and when radiation damage effects become significant for He loss from this mineral.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/S0040-1951(02)00058-6DOIUNSPECIFIED
http://www.sciencedirect.com/science/article/pii/S0040195102000586PublisherUNSPECIFIED
ORCID:
AuthorORCID
Reiners, Peter W.0000-0001-7240-2373
Farley, Kenneth A.0000-0002-7846-7546
Additional Information:© 2002 Elsevier Science B.V. Received 20 June 2000; accepted 27 July 2001. Thanks to Barry Kohn for the FCT samples, Matt Heizler for the Chain of Ponds sample, Mark Garcia for mineral separations, Lindsey Hedges for help with zircon dissolutions at Caltech, Charles Knaack for technical and analytical help at WSU, Scotty Cornelius for microprobe help, and Rob Brady for help in the field at and with geologic interpretation of Gold Butte. We appreciate constructive and thoughtprovoking reviews from Fin Stuart and Mark Harrison. This work was supported in part by NSF EAR 0073576 to PWR and NSF grants to KAF.
Funders:
Funding AgencyGrant Number
NSFEAR 0073576
NSFUNSPECIFIED
Subject Keywords:Thermochronology; (U–Th)/He; Geochronology; Zircon; Helium
Issue or Number:1-4
Record Number:CaltechAUTHORS:20121121-093240494
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121121-093240494
Official Citation:Peter W. Reiners, Kenneth A. Farley, Hunter J. Hickes, He diffusion and (U–Th)/He thermochronometry of zircon: initial results from Fish Canyon Tuff and Gold Butte, Tectonophysics, Volume 349, Issues 1–4, 6 May 2002, Pages 297-308, ISSN 0040-1951, 10.1016/S0040-1951(02)00058-6. (http://www.sciencedirect.com/science/article/pii/S0040195102000586)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35598
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 Nov 2012 17:50
Last Modified:09 Mar 2020 13:19

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