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Chlorine, fluorine, and water in contact metamorphic environments

English title Chlorine, fluorine, and water in contact metamorphic environments
Applicant Baumgartner Lukas P.
Number 172513
Funding scheme Project funding (Div. I-III)
Research institution Institut des sciences de la Terre Université de Lausanne
Institution of higher education University of Lausanne - LA
Main discipline Geochemistry
Start/End 01.04.2017 - 30.09.2018
Approved amount 312'790.00
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All Disciplines (4)

Discipline
Geochemistry
Other disciplines of Earth Sciences
Geology
Mineralogy

Keywords (7)

fluid-rock interaction; thermodynamics; chlorine; SIMS; experimental petrology; contact metamorphism; hydrous minerals

Lay Summary (German)

Lead
Die Chlor, Fluor und Wasserkonzentration in wasserhaltigen Mineralien wird durch Sekundäre Ionenmassenspektrometrie bestimmt, um Wasseraktivität, und Chlor/Fluor Konzentrationen in der Fluiden Phase abzuschätzen. Die Kinetik und Gleichgewichtsfaktoren für Wasser-Apatite Austausch werden bestimmt mit 1atm und Hydrothermalexperimente.
Lay summary

Das Mineralwachstum in Gesteinen der Erdkruste ist dominiert durch Wasser-Gesteinsinteraktion. Wasser-Gesteins Interaktionen sind auch wichtig für „deep carbon storage“, oder das Abschotten von chemischen und radiogenen Abfällen. fokussiert auf die Bestimmung der Zusammensetzung von wässerigen Fluiden, welche im chemischen Gleichgewicht mit den Gesteinen sind. Die Fähigkeit der Fluide mit Mineralien zu reagieren ist nun wesentlich von den Konzentrationen der Anionen (wie z.B. Chlor, Fluor, etc.) abhängig. Da die Fluide Phase nach Abschluss der Reaktionen das Gestein typischerweise verlässt, kann das Fluid nicht mehr direkt analysiert werden. Durch die Analyse von Cl, Fluor und Wassergehalt in wasserhaltigen Mineralien können die Konzentrationen dieser Anionen abgeschätzt werden.

Die Zusammensetzung von wasserhaltige Mineralen, wie z.B.  Glimmer, Turmalin, und Apatite hängt von den Konzentrationen der Anionen im Wasser ab. In diesem Projekt verbessern wir einerseits die Analytischen Methoden zur Messung von OH-,und F- mit der Sekundären Ionenmassenspektrometrie in diesen wasserhaltigen Mineralien, anderseits analysieren wir diese Mineralien in kontaktmetamorphen Gesteinen der Little Cottonwood Stock Intrusion in Utah (Salt Lake). Ergänzt werden diese Studien durch gepufferte Hydrothermalexperimente zum Wasser-Chlor-Fluor Austausch zwischen Apatit und salinen Fluid (1000-2000bar; 400°C-800°C) sowie durch 1atm Experimente zur Bestimmung der diffusiven Austauschkinetik von Wasser, Chlor und Fluor in Apatit.


Direct link to Lay Summary Last update: 04.04.2017

Responsible applicant and co-applicants

Employees

Publications

Publication
Oxygen isotope disequilibrium during serpentinite dehydration
Lafay Romain, Baumgartner Lukas P., Putlitz Benita, Siron Guillaume (2019), Oxygen isotope disequilibrium during serpentinite dehydration, in Terra Nova.
Accurate Measurements of H 2 O, F and Cl Contents in Biotite Using Secondary Ion Mass Spectrometry
Siron Guillaume, Baumgartner Lukas P., Bouvier Anne-Sophie, Vennemann Torsten (2018), Accurate Measurements of H 2 O, F and Cl Contents in Biotite Using Secondary Ion Mass Spectrometry, in Geostandards and Geoanalytical Research, 42(4), 523-537.
Significance of OH, F and Cl content in biotite during metamorphism of the Western Adamello contact aureole
Siron Guillaume, Baumgartner Lukas, Bouvier Anne-Sophie (2018), Significance of OH, F and Cl content in biotite during metamorphism of the Western Adamello contact aureole, in Contributions to Mineralogy and Petrology, 173(8), 63-63.

Collaboration

Group / person Country
Types of collaboration
Lluis Fontboté Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Prof. Andrea Dini Italy (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
prof. Peter Nabelek United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
prof. Daniela Rubatto Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
prof. Barbara Dutrow United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Associated projects

Number Title Start Funding scheme
153094 Case studies of halogen behaviour during prograde and retrograde contact metamorphism 01.04.2014 Project funding (Div. I-III)
171722 Boron isotope fractionation in crustal granite systems 01.01.2017 International short research visits
165756 Kinetic versus mechanical control of petrological pressure record of the Monte Rosa nappe: a combined geomechanical and petrological approach 01.04.2016 Project funding (Div. I-III)

Abstract

We study the F, Cl and hydrogen contents of biotite, white mica, apatite, and tourmaline in meta-pelites from the Little Cottonwood aureole (Utah, USA). This field-based study will be complemented by 1 atm diffusion experiments and hydrothermal experiments investigating the response of apatite to H2O-HCl-HF fluids. We have developed measurement techniques and standards for OH-, Cl-, and F- in biotite, and published papers on oxygen isotope standards for biotite and quartz; furthermore, standards are currently being developed for white mica. Our current work highlights the possibility that the above-mentioned minerals might have significant amounts of an oxy-component on the hydroxyl site. Our work on biotite suggests that the reaction 2 OH-biotite => oxy-biotite +H2O reduces the H2O activity in biotite, and hence that the water content is indeed a sensor for water fugacity. The exchange in biotite might be masked by a coupled Ti-oxy biotite substitution. Apatite, on the other hand, does not suffer from this and might thus prove to be an easier candidate for which to develop a practical water fugacity sensor.Our work on biotite seems to suggest that this mineral is capable of retaining chlorine incorporated into its crystal structure during prograde biotite formation. This is surprising, since biotite is known for fast diffusion of cations such as Fe + Mg. A similar discrepancy has been found for apatite: while field studies suggest that Cl in apatite is resilient to re-equilibration even at high temperatures, the existing experimental diffusion data suggest it would readily exchange Cl with adjacent phases down to temperatures as low as 400°C. Brenan (1993a) suggested that significant O2- in apatite might slow down diffusion considerably. Since water fugacity decreases upon cooling due to hydration of high-T phases (Markl and Bucher 1998) this could lead to sluggish diffusion of halogens in many natural apatites. The Little Cottonwood granodiorite stock (Utah, USA) intruded into a thick sequence of late Proterozoic anchizone metamorphic quartzites and pelites. The highest-grade rocks are magnetite-cordierite-sillimanite-biotite rocks showing abundant partial melting. Intrusion depth is estimated at ca. 10-12km. Crystallization of partial melts resulted in locally abundant retrograde muscovite. The overall aim is to establish 1) a comprehensive inventory of halogens in contact metamorphic pelites; 2) develop and test the water fugacity sensors; 3) provide the petrologic community with robust experimental data on apatite-fluid equilibrium and kinetic exchange parameters.
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