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Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan

Kidder, S. and Avouac, J.-P. and Chan, Y.-C. (2013) Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan. Solid Earth, 4 (1). pp. 1-21. ISSN 1869-9510 . http://resolver.caltech.edu/CaltechAUTHORS:20130523-092356435

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Abstract

The accuracy, reliability and best practises of Ti-in-quartz thermobarometry (TitaniQ) in greenschist facies rocks have not been established. To address these issues, we measured Ti concentrations in rutile-bearing samples of moderately deformed, partially recrystallized quartzite and vein quartz from the Hsüehshan range, Taiwan. The spread of Ti concentrations of recrystallized grains in quartzite correlates with recrystallized grain size. Recrystallized quartz (grain size ~100–200 μm) that formed during early deformation within the biotite stability field shows a marked increase in intermediate Ti-concentration grains (~1–10 ppm) relative to detrital porphyroclasts (Ti ~0.1–200 ppm). Fine recrystallized quartz (~5% of the samples by area, grain size ~10–20 μm) has a further restricted Ti concentration peaking at 0.8–2 ppm. This trend suggests equilibration of Ti in recrystallized quartz with a matrix phase during deformation and cooling. Unlike previously documented examples, Ti concentration in the quartzite is inversely correlated with blue cathodoluminescence. Deformation was associated with a minimum grain boundary diffusivity of Ti on the order of 10^(−22)m^2 s^(−1). Vein emplacement and quartzite recrystallization are independently shown to have occurred at 250–350 °C and 300–410 °C, respectively, with lithostatic pressure of 3–4 kbar (assuming a geothermal gradient of 25° km^(−1)), and with hydrostatic fluid pressure. Estimates of the accuracy of TitaniQ at these conditions depend on whether lithostatic or fluid pressure is used in the TitaniQ calibration. Using lithostatic pressure and these temperatures, the Thomas et al. (2010) calibration yields Ti concentrations within error of concentrations measured by SIMS. If fluid pressure is instead used, predicted temperatures are ~30–40 °C too low. TitaniQ has potential to yield accurate PT information for vein emplacement and dynamic recrystallization of quartz at temperatures as low as ~250 °C, however clarification of the relevant pressure term and further tests in rutile-present rocks are warranted.


Item Type:Article
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http://dx.doi.org/10.5194/se-4-1-2013 DOIArticle
http://www.solid-earth.net/4/1/2013/se-4-1-2013.htmlPublisherArticle
Additional Information:© 2013 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 23 May 2012 – Published in Solid Earth Discuss.: 8 June 2012; Revised: 22 October 2012 – Accepted: 27 October 2012 – Published: 7 January 2013. The manuscript directly benefited from interactions with Michel Bestmann, Jeremy Boyce, John Eiler, Aaron Martin, Mike Palin, Jason Saleeby, Martine Simoes, James Scott, Joann Stock, Marion Le Voyer, and Brian Wernicke. Chih-Tung Chen, Chung Huang, Aaron Martin, Shiao An-Yu, and Yong Chi-Kai are thanked for their assistance in the field. Yunbin Guan, Chi Ma, Jeremy Boyce, and Marion Le Voyer provided helpful assistance with the SEM and SIMS. Robin Kidder helped with illustrations and many other aspects of the work. John Platt and the Pasadena Rheological Society are thanked for providing a forum for discussing all things microstructural. Jay Thomas provided us with an experimental sample that aided in SIMS calibration. Reviews by Frank Spear and Whitney Behr significantly improved the manuscript. Financial support was provided by the Gordon and Betty Moore Foundation via Caltech’s Tectonics Observatory. This is Caltech Tectonic Observatory contribution 217.
Group:Caltech Tectonics Observatory, Seismological Laboratory
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Gordon and Betty Moore FoundationUNSPECIFIED
Caltech Tectonics ObservatoryUNSPECIFIED
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Caltech Tectonics Observatory217
Record Number:CaltechAUTHORS:20130523-092356435
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130523-092356435
Official Citation:Kidder, S., Avouac, J.-P., and Chan, Y.-C.: Application of titanium-in-quartz thermobarometry to greenschist facies veins and recrystallized quartzites in the Hsüehshan range, Taiwan, Solid Earth, 4, 1-21, doi:10.5194/se-4-1-2013, 2013
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38653
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:25 Jun 2013 15:41
Last Modified:11 Jun 2015 13:57

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