New Experimental Data for a Re-Calibration of the Fe-Ti Oxide Thermo-Oxybarometers
type: CreativeWork
description: Despite their modest modal abundances, Fe-Ti oxides are important accessory minerals in igneous rocks. They are major carriers of rock magnetism and petrologic indicators of temperature and redox conditions during the magmatic stage (Buddington & Lindsley, 1964). The titanomagnetite-ilmenitess (Tmt-Ilmss) thermo-oxybarometer has been widely used to retrieve information, e.g. on redox states in the Earth’s mantle, processes in magma chambers, or the crystallisation conditions of lunar or martian basalts. Current thermodynamic formulations of the Tmt-Ilmss thermo-oxybarometer (Andersen & Lindsley, 1988; Ghiorso & Sack, 1991) fail to reproduce experimental results, in particular at the high T relevant for basaltic assemblages. This is shown by applying the formulations to experimental literature data. The shortcomings of the existing models are partly due to the limited T-fO2-range of experiments used for the original calibrations. The effect of small contents of Mg, Al, etc. typical for natural Tmt and Ilmss was only partly evaluated, and non-stoichiometry of the phases (in particular Tmt) was not considered at all. To support a revised version of the Tmt-Ilmss thermo-oxybarometer we have synthesised Tmt+Ilmss assemblages in the system Fe-Ti-Mg-Al-O at 1 bar, 1000-1300°C and under a large range of fO2 (NNO-5 to +5). A large data set has also been provided for Ilmss coexisting with pseudobrookitess (Psbss). This forms the basis for an experimental calibration of a thermodynamic Ilmss-Psbss (thermo-)oxybarometer model. The data base on Tmt coexisting with Ilmss used to calibrate the previous models has now been extended towards higher T (i.e. 1000-1300°C) and to a larger range of fO2. The compositions of coexisting Fe-Ti oxides in the system Fe-Ti-O have been determined by EMP as a function of T and fO2. The experimental data derived within this study has been compared to the existing models. The structural transition within the ilmenite-hematite solid solution series c…
abstract: Despite their modest modal abundances, Fe-Ti oxides are important accessory minerals in igneous rocks. They are major carriers of rock magnetism and petrologic indicators of temperature and redox conditions during the magmatic stage (Buddington & Lindsley, 1964). The titanomagnetite-ilmenitess (Tmt-Ilmss) thermo-oxybarometer has been widely used to retrieve information, e.g. on redox states in the Earth’s mantle, processes in magma chambers, or the crystallisation conditions of lunar or martian basalts. Current thermodynamic formulations of the Tmt-Ilmss thermo-oxybarometer (Andersen & Lindsley, 1988; Ghiorso & Sack, 1991) fail to reproduce experimental results, in particular at the high T relevant for basaltic assemblages. This is shown by applying the formulations to experimental literature data. The shortcomings of the existing models are partly due to the limited T-fO2-range of experiments used for the original calibrations. The effect of small contents of Mg, Al, etc. typical for natural Tmt and Ilmss was only partly evaluated, and non-stoichiometry of the phases (in particular Tmt) was not considered at all. To support a revised version of the Tmt-Ilmss thermo-oxybarometer we have synthesised Tmt+Ilmss assemblages in the system Fe-Ti-Mg-Al-O at 1 bar, 1000-1300°C and under a large range of fO2 (NNO-5 to +5). A large data set has also been provided for Ilmss coexisting with pseudobrookitess (Psbss). This forms the basis for an experimental calibration of a thermodynamic Ilmss-Psbss (thermo-)oxybarometer model. The data base on Tmt coexisting with Ilmss used to calibrate the previous models has now been extended towards higher T (i.e. 1000-1300°C) and to a larger range of fO2. The compositions of coexisting Fe-Ti oxides in the system Fe-Ti-O have been determined by EMP as a function of T and fO2. The experimental data derived within this study has been compared to the existing models. The structural transition within the ilmenite-hematite solid solution series c…
author: Sauerzapf, Ursula
date published: 2006-05-29
date modified: 2026-07-24T02:30:27Z
provider: Universität Heidelberg
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Heidelberg