Experimental Evaluation of Stress Relaxation of Quartz Inclusions in Garnet

Date of Award

Winter 12-22-2021

Degree Type


Degree Name

Master of Science (MS)


Earth Sciences


Thomas, Jay


Experimental, Garnet, Inclusion, Quartz, Stress-Relaxation, Thermobarometry

Subject Categories

Earth Sciences | Geology | Physical Sciences and Mathematics


Host-inclusion elastic thermobarometers are widely used to determine the pressure and temperature (P–T) conditions of formation and deformation, and histories of metamorphic rocks. Metamorphic P–T paths may be complex, and this complexity can affect the stress state of mineral inclusions. Previous experimental studies for host-inclusion thermobarometry have only included static P–T conditions. Further refinement and experimentation are necessary to better understand how host-inclusion systems behave, and the tectonic processes that drive our planet. This study is the first to apply dynamic experimental pressure-temperature-time (P–T–t) conditions for host-inclusion thermobarometers. Quartz inclusions in garnet hosts were grown hydrothermally from powdered oxide materials in a piston-cylinder device in isothermal experiments at 600, 700, and 800°C. Pressurization and depressurization experiments were conducted in two stages of pressure ranging from 1.0–3.2 GPa. Pressure in the first stage was held constant for 48 hours before changing pressure. Second-stage experimental pressures were held constant for 0–912 hours. Changes in experimental pressures ranged from 0.5–1.2 GPa. Individual quartz inclusions were measured for changes to the 128, 206, and 464 cm-1 Raman bands to determine the entrapment pressures (Ptrap). Over 200 individual inclusion measurements on each experiment indicate that the majority of inclusions reequilibrated towards the new experimental P–T conditions. Average Ptrap values for all experiments are between the two pressure stages. There is no evidence suggesting that significant numbers of inclusions were entrapped after adjusting pressure to the second-stage condition. This study predicts that host-inclusion system to have an initial elastic reaction upon changes to P–T conditions with a gradational change to viscous creep. Results indicate that changes to the pressure of a metamorphic rock at T>600C will modify the stress state of quartz inclusions in garnet. The final stress state of quartz inclusions provides information on the final metamorphic PT conditions.


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