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Incorporating 3-D parent nuclide zonation for apatite ^4He/^3He thermochronometry: An example from the Appalachian Mountains

Fox, Matthew and McKeon, Ryan E. and Shuster, David L. (2014) Incorporating 3-D parent nuclide zonation for apatite ^4He/^3He thermochronometry: An example from the Appalachian Mountains. Geochemistry, Geophysics, Geosystems, 15 (11). pp. 4217-4229. ISSN 1525-2027. http://resolver.caltech.edu/CaltechAUTHORS:20141027-091019893

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Abstract

The ability to constrain km-scale exhumation with apatite ^4He/^3He thermochronometry is well established and the technique has been applied to a range of tectonic and geomorphic problems. However, multiple sources of uncertainty in specific crystal characteristics limit the applicability of the method, especially when geologic problems require identifying small perturbations in a cooling path. Here we present new ^4He/^3He thermochronometric data from the Appalachian Mountains, which indicate significant parent nuclide zonation in an apatite crystal. Using LA-ICPMS measurements of U and Th in the same crystal, we design a 3-D model of the crystal to explore the effects of intra-crystal variability in radiation damage accumulation. We describe a numerical approach to solve the 3-D production-diffusion equation. Using our numerical model and a previously determined time temperature path for this part of the Appalachians, we find excellent agreement between predicted and observed ^4He/^3He spectra. Our results confirm this time-temperature path and highlight that for complex U and Th zonation patterns, 3-D numerical models are required to infer an accurate time-temperature history. In addition, our results provide independent and novel evidence for a radiation damage control on diffusivity. The ability to exploit intra-crystal differences in 4He diffusivity (i.e., temperature sensitivity) greatly increases the potential to infer complex thermal histories.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://onlinelibrary.wiley.com/doi/10.1002/2014GC005464/abstractPublisherArticle
http://dx.doi.org/10.1002/2014GC005464DOIArticle
Alternate Title:Incorporating 3-D parent nuclide zonation for apatite 4He/3He thermochronometry: An example from the Appalachian Mountains
Additional Information:© 2014 American Geophysical Union. Received: Jun 18, 2014; Revised: Oct 07, 2014; Accepted: Oct 14, 2014. We thank P. Tackley for introducing M.F. to the multigrid approach and for sharing part of the code and A. Tripathy-Lang for comments on an early version of this manuscript. This work has been supported by the Swiss National Science Foundation (P2EZP2_148793), the U.S. National Science Foundation grant EAR-1049988 (to D.L.S.) and the Ann and Gordon Getty Foundation. In addition, R.E.M. acknowledges support from several Palmer Research grants from the Earth and Environmental Sciences Department of Lehigh University and to K. Farley at Caltech for help with [U] and [Th] LA-ICPMS analyses.
Funders:
Funding AgencyGrant Number
Swiss National Science Foundation (SNSF)P2EZP2_148793
NSFEAR-1049988
Ann and Gordon Getty FoundationUNSPECIFIED
Palmer Research grantsUNSPECIFIED
Lehigh University, Department of Earth and Environmental SciencesUNSPECIFIED
CaltechUNSPECIFIED
Subject Keywords:Apatite (U-Th)/He thermochronometry; He diffusion; Appalachian Mountains
Record Number:CaltechAUTHORS:20141027-091019893
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20141027-091019893
Official Citation:Fox, M., R. E. McKeon, and D. L. Shuster (2014), Incorporating 3-D parent nuclide zonation for apatite 4He/3He thermochronometry: An example from the Appalachian Mountains, Geochem. Geophys. Geosyst., 15, 4217–4229, doi:10.1002/2014GC005464.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:50829
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:27 Oct 2014 17:04
Last Modified:21 Sep 2016 22:25

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