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(U–Th)/He thermochronometry: Mapping 3D geometry using micro-X-ray tomography and solving the associated production–diffusion equation

Herman, Frédéric and Braun, Jean and Senden, Tim J. and Dunlap, William J. (2007) (U–Th)/He thermochronometry: Mapping 3D geometry using micro-X-ray tomography and solving the associated production–diffusion equation. Chemical Geology, 242 (1-2). pp. 126-136. ISSN 0009-2541. https://resolver.caltech.edu/CaltechAUTHORS:20170412-064434901

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Abstract

(U–Th)/He ages reflect the combined effects of He (α particles) loss due to diffusion and He ingrowth due to radioactive decay of U and Th series. Furthermore, the α particles are emitted with sufficient kinetic energy that they can travel, in theory, up to 20 μm and as a result, α particles may be ejected beyond the crystal edges. To circumvent this problem a correction factor must be applied, which is essentially based on the geometry of the crystals [Farley, K. A., Wolf, R., and Silver, L. (1996). The effect of long alpha-stopping distances on (U–Th)/He dates. Geochimica et Cosmochimica Acta, 60:4223–4229]. This strongly limits the application of the technique to crystals of appropriate geometries. We present here a method to compute the effects of α-ejection for (U–Th)/He dating by taking into account the 3D morphology of individual crystals determined with micro-X-ray tomography. We also develop a model which solves the diffusion equation for the crystals that have been imaged. We then couple this model with an inversion algorithm to extract the range of thermal histories that the rocks may have experienced. This technique is applied to detrital samples from rocks collected in the Southern Alps of New Zealand, a region of high exhumation rate.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://doi.org/10.1016/j.chemgeo.2007.03.009DOIArticle
http://www.sciencedirect.com/science/article/pii/S000925410700126XPublisherArticle
Additional Information:© 2007 Elsevier B.V. Received 10 April 2006, Revised 27 February 2007, Accepted 7 March 2007, Available online 27 March 2007. Editor: R.L. Rudnick. We thank Charlotte Allen for her help for the LA-ICP-MS, Xiaodong Zhang for technical assistance with the vacuum line and Mark Harrison for stimulating discussions. This work was carried out at the Australian National University. Some of the computations presented here were performed on the Terrawulf facility of the Centre for Advanced Data Inference at the Research School of Earth Sciences, Australian National University. The segmentation of the micro-X-ray tomography was done on 128-cpu cluster facility at the Department of Applied Mathematics, Australian National University. This research was supported by the Australian Research Council (ARC discovery grant DP0342909). TJS is a recipient of an Australian Research Council Fellowship. We thank two anonymous reviewers.
Funders:
Funding AgencyGrant Number
Australian Research CouncilDP0342909
Subject Keywords:(U–Th)/He dating; X-ray tomography; Helium diffusion; Genetic Algorithm
Issue or Number:1-2
Record Number:CaltechAUTHORS:20170412-064434901
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170412-064434901
Official Citation:Frédéric Herman, Jean Braun, Tim J. Senden, William J. Dunlap, (U–Th)/He thermochronometry: Mapping 3D geometry using micro-X-ray tomography and solving the associated production–diffusion equation, Chemical Geology, Volume 242, Issues 1–2, 30 July 2007, Pages 126-136, ISSN 0009-2541, http://doi.org/10.1016/j.chemgeo.2007.03.009. (http://www.sciencedirect.com/science/article/pii/S000925410700126X)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:76525
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 Apr 2017 15:56
Last Modified:03 Oct 2019 17:02

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