McDowell, Fred W. and McIntosh, William C. and Farley, Kenneth A. (2005) A precise ^(40)Ar–^(39)Ar reference age for the Durango apatite (U–Th)/He and fission-track dating standard. Chemical Geology, 214 (3-4). pp. 249-263. ISSN 0009-2541. http://resolver.caltech.edu/CaltechAUTHORS:20121120-130529682
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The distinctive Durango apatite is widely distributed as a reference material for mineralogy, geochemistry and thermochronology. The apatite occurs within the Cerro de Mercado open-pit iron mine, located in the northern portion of Durango City, Mexico. It is largely confined to vugs and open fractures within the lower portion of the ore deposit. Apatite and iron ore formed in situ and concurrently along with emplacement of small felsic intrusions along the southern margin of the Chupaderos caldera complex. This activity occurred between eruptions of two major ignimbrites from the caldera complex. Four single-crystal sanidine-anorthoclase ^(40)Ar–^(39)Ar ages from these ignimbrites and from a conformable older unit have been used to compute a reference age of 31.44±0.18 Ma (2σ) for the apatite itself. Four additional multi-crystal measurements are in general agreement with this age. Also in agreement are a set of 24 (U–Th–Sm)/He ages recently determined directly on the apatite, which have a mean of 31.02±1.01 Ma 1σ, with a standard error (S.E.) of ±0.22 Ma.
|Additional Information:||© 2004 Elsevier B.V. Received 31 March 2004; accepted 7 October 2004. It is obvious that this contribution would not have been possible without heavy reliance upon the research projects of three Masters students. Although the essence of those studies has been published previously, Richard Keizer, James Lyons and Eric Swanson are deserving of renewed recognition for their fine work. Keizer and Paul Guenther also provided help with the K–Ar dating. The (U–Th)/He age determinations were supported by NSF EAR 0105981. Comments by Lyons, Swanson, Mark Cloos, Todd Housh and Richard Ketcham have greatly improved this manuscript. Lyons also provided help in preparing Fig. 1. We thank Mike Villenueva and Joann Wartho for their helpful reviews. [PD]|
|Subject Keywords:||Geochronology; ^(40)Ar–^(39)Ar; (U–Th)/He; Apatite; Durango, Mexico|
|Official Citation:||Fred W. McDowell, William C. McIntosh, Kenneth A. Farley, A precise ^(40)Ar–^(39)Ar reference age for the Durango apatite (U–Th)/He and fission-track dating standard, Chemical Geology, Volume 214, Issues 3–4, 25 January 2005, Pages 249-263, ISSN 0009-2541, 10.1016/j.chemgeo.2004.10.002. (http://www.sciencedirect.com/science/article/pii/S0009254104004218)|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||20 Nov 2012 21:34|
|Last Modified:||20 Nov 2012 21:34|
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