Title

How Hot Is “Hot”?: Comparison of Crystallization Thermometers in Metamorphic Garnets

Document Type

Student Presentation

Presentation Date

4-16-2018

College

College of Arts and Sciences

Department

Geosciences

Faculty Sponsor

Matthew Kohn

Abstract

Metamorphic rocks encode a history of Earth geodynamics through growth of their constituent metamorphic minerals. As pressure and temperature evolve, metamorphic minerals such as garnet grow, and the garnet’s chemistry and inclusion minerals change. By analyzing inclusion minerals in metamorphic garnets, we can in principle obtain that rock’s pressure-temperature history, and infer the geodynamic processes by which the rock formed.

The goal of this study is to quantify temperatures that are recorded by mineral inclusions that are distributed throughout single metamorphic garnet crystals. By studying rocks whose temperature histories are already inferred from chemical zoning in garnets, we can cross-check different methods of obtaining these histories. The two methods we are comparing to chemically-based temperature histories are: (1) the Zr-content of rutile (TiO2) inclusions as determined from trace element measurements using laser-ablation, inductively-coupled plasma mass spectrometry, and (2) the temperature-dependent differential elastic response of inclusions of zircon (ZrSiO4) in garnet and the surrounding garnet crystal, as determined using Raman spectroscopy.

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