T229 Mineralogy, Geochemistry, Petrology, and Volcanology Student Session

Wednesday, 25 September 2024
8:00 AM - 12:00 PM
207D

THE ATiO2 PROBLEM: CURRENT LIMITATIONS TO Ti-BASED THERMOMETERS IN MAGMATIC SYSTEMS

Paper number: T229-15
Program: Technical Sessions
Time: 11:20 AM – 11:35 AM

Authors

Abstract

Ti-thermometers are currently among of the most widely used methods to estimate crystallisation temperatures in silicic magmatic systems and beyond. Their success stems from their convenience: it is easy, fast, and cheap to measure in-situ Ti in mineral phases by LA-ICP-MS or EPMA, which are available in many institutions. Quartz and zircons, the most commonly used minerals for Ti-thermometers, are frequently present in most high-Si magmatic rocks. Geoscientists can obtain crystallisation temperatures for these mineral phases by applying a relatively easy to use equation derived from experimental calibrations (e.g. Wark and Watson, 2006 for quartz). However, utilisation of Ti thermometers requires a good constraint on aTiO2, an aspect that is largely overlooked when these thermometers are employed. Thus, accurate estimations of aTiO2 are key to obtain reliable temperature through such thermometers.

This presentation will review current methods for estimating aTiO2 and their associated limitations, as well as common errors when utilising and interpreting Ti-based thermometers. Despite being often constrained to a fixed value, aTiO2 must be understood as a dynamic parameter throughout crystallisation, heavily dependent on the TiO2 content of the melt and on the crystallisation temperature, as demonstrated by its basis on thermodynamics and TiO2-solubility models. The goal of this presentation is to provide guidelines for Earth scientists to successfully apply Ti-thermometers, in order to avoid inaccurate calculations and erroneous interpretations. When properly applied, Ti thermometers can be powerful tools for researchers, offering numerous possibilities to address persistent questions in magmatic systems.

Wark, D. A., & Watson, E. B. (2006). TitaniQ: a titanium-in-quartz geothermometer. Contributions to Mineralogy and Petrology, 152(6), 743-754.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-403305

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