Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff

Fu, Roger R. and Weiss, Benjamin P. and Lima, Eduardo A. and Kehayias, Pauli and Araujo, Jefferson F.D.F. and Glenn, David R. and Gelb, Jeff and Einsle, Joshua F. and Bauer, Ann M. and Harrison, Richard J. and Ali, Guleed A.H. and Walsworth, Ronald L. (2017) Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff. Earth and Planetary Science Letters, 458. pp. 1-13. ISSN 0012-821X DOI 10.1016/j.epsl.2016.09.038

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Official URL: http://doi.org/10.1016/j.epsl.2016.09.038

Abstract

Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the history of the earliest geodynamo, which would hold broad implications for the early Earth's interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been demonstrated. Here we conduct thermal and alternating field (AF) paleointensity experiments on 767.1 thousand year old (ka) zircons from the Bishop Tuff, California. The rapid emplacement of these zircons in a well-characterized magnetic field provides a high-fidelity test of the zircons' intrinsic paleomagnetic recording accuracy. Successful dual heating experiments on eleven zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of View the MathML source54.1±6.8μT (1σ ; View the MathML source42.6±5.3μT after excluding possible maghemite-bearing zircons), which is consistent with high-precision results from Bishop Tuff whole rock (View the MathML source43.0±3.2μT). High-resolution quantum diamond magnetic (QDM) mapping, electron microscopy, and X-ray tomography indicate that the bulk of the remanent magnetization in Bishop Tuff zircons is carried by Fe oxides associated with apatite inclusions, which may be susceptible to destruction via metamorphism and aqueous alteration in older zircons. As such, while zircons can reliably record the geomagnetic field, robust zircon-derived paleomagnetic results require careful characterization of the ferromagnetic carrier and demonstration of their occurrence in primary inclusions. We further conclude that a combination of quantum diamond magnetometry and high-resolution imaging can provide detailed, direct characterization of the ferromagnetic mineralogy of geological samples.

Item Type: Article
Uncontrolled Keywords: 2016AREP; IA72;
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 458
Page Range: pp. 1-13
Identification Number: 10.1016/j.epsl.2016.09.038
Depositing User: Sarah Humbert
Date Deposited: 02 Mar 2017 21:40
Last Modified: 09 Apr 2017 01:23
URI: http://eprints.esc.cam.ac.uk/id/eprint/3835

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