Document Type


Date of Degree Completion

Spring 2014

Degree Name

Master of Science (MS)


Geological Sciences

Committee Chair

Chris Mattinson

Second Committee Member

Audrey Huerta

Third Committee Member

Jeff Lee


The Dulan ultrahigh-pressure (UHP) terrane exposes 449-422 Ma eclogites in the east and 449-418 Ma high-pressure granulites to the west, but the relationship between the units is poorly understood. Zirconium-in-rutile temperatures show an east-west 3- 5°C/km gradient in four UHP eclogites: 662-716±10°C; garnet-omphacite-phengite thermobarometry of peak conditions yields 659-730±82°C, 25.3-27.1±3.2 kbars. Zircon U-Pb ages of four eclogites are the same within uncertainty, averaging 434±2.9 Ma. Tiin- zircon thermometry and rare earth element patterns indicate these ages represent eclogite facies metamorphism. One high-pressure/high-temperature (HP/HT) granulite yields a minimum rutile temperature of 773±4°C. Previous thermobarometry of highpressure granulites yields ≥800°C and 14-17 kbars. Both eclogites and high-pressure granulites share an amphibolite facies retrogression texture. The evidence presented here supports either of two pressure-temperature models: 1) a melt-weakened slab exhumes, placing HP/HT granulites in a UHP terrane or 2) that HP/HT granulites formed in thickened overriding crust and were tectonically juxtaposed with UHP eclogites later.