This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The project investigates the role of deformation in the distribution of titanium (Ti) and other trace elements in quartz over a wide range of temperature and deformation conditions in nature and experiments. The mobility of Ti in deforming quartz is addressed by high-pressure/high-temperature experiments that test the role of dynamic recrystallization on Ti migration in quartz. In parallel, this research uses natural quartz rocks to investigate two tectonic settings: (1) contractional (thrust) systems, in which rocks deformed during heating and burial; quartz microstructures locked in over a narrow range of temperatures but display a wide range of microstructures; and (2) extensional (detachment) systems, in which rocks deformed over a wide temperature range but developed similar microstructures as hot rocks exhumed towards the Earth's surface. In experiments and natural rocks from detachment and thrust systems, this project examines how inherited Ti is redistributed as a function of deformation and temperature conditions. Natural samples are from the Heavitree Quartzite in the Ruby Gap Duplex, central Australia (thrust); the Siviez-Mischabel nappe in the western Alps, Switzerland (thrust); and the Kettle and Snake Range extensional detachment systems, western United States. Research methods include petrographic and electron backscatter diffraction characterization of quartz microstructure, types of recrystallization, and crystallographic preferred orientation; cathodoluminescence imaging of trace element zoning in quartz; and ion microprobe analysis of Ti in quartz in experimental and natural samples.
Quartz is silicon dioxide (SiO2) but may contain trace amounts of other elements, such as titanium and aluminum. The abundance of these trace elements may correlate with temperature, thereby providing a means to calculate the temperature at which quartz-bearing rocks locked in their composition when they formed during tectonic events. Documenting the thermal evolution of the crust in different tectonic settings (contraction, extension) is important for understanding how tectonic processes operate over time. Although the Ti content of quartz is increasingly used to calculate paleo-temperatures of quartz-rich rocks, the role of deformation in the distribution of trace elements in quartz must be understood. A combined field and experimental study of the effect of deformation in different thermal and tectonic settings can evaluate the effect of deformation on trace element distribution in quartz.
