β-Factors of Titanite and Oxygen Isotope Fractionation in the Titanite–Ilmenite–Rutile System

New 18 O/ 16 O β-factors have been calibrated against temperature for titanite (considering the principal isomorphic substitutions Al + F ⇔ Ti + O, Ti + O ⇔ Al + OH, Ti + O ⇔ Fe 3+ + OH) and ilmenite (accounting for Fe ⇔ Mg substitution) for the first time using the frozen-phonon approach of the den...

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Bibliographic Details
Published in:Petrology 2021-11, Vol.29 (6), p.686-694
Main Author: Krylov, D. P.
Format: Article
Language:English
Subjects:
Aluminum
Density functional theory
Earth and Environmental Science
Earth Sciences
Fractionation
Geochemistry
Ilmenite
Iron
Isotope fractionation
Isotopes
Mineralogy
Oxygen
Oxygen isotopes
Rutile
Silicates
Titanite
Titanium
Titanium dioxide
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Summary:New 18 O/ 16 O β-factors have been calibrated against temperature for titanite (considering the principal isomorphic substitutions Al + F ⇔ Ti + O, Ti + O ⇔ Al + OH, Ti + O ⇔ Fe 3+ + OH) and ilmenite (accounting for Fe ⇔ Mg substitution) for the first time using the frozen-phonon approach of the density functional theory. The equilibrium oxygen isotope fractionation factors between titanite (CaTiSiO 5 ), ilmenite (FeTiO 3 ), and rutile (TiO 2 ) are expressed as: 1000 ln α ttn–ilm = 1000 ln β ttn – 1000 ln β ilm = 1.96836 x – 0.10514 x 2 + 0.00319 x 3 , 1000 ln α ttn–rt = 1000 ln β ttn – 1000 ln β rt = 1.80155 x – 0.09262 x 2 + 0.00288 x 3 , x = 10 6 / T 2 (K –2 ). The results can be applied to geothermometry, particularly in calc–silicate and calc–alkaline rocks of magmatic, metamorphic, and metasomatic origins.
ISSN:0869-5911
1556-2085
DOI:10.1134/S0869591121050040