Download Application of Thermochronology and Thermobarometry to the Ruby

Application of Thermochronology and Thermobarometry to the Ruby Mountains
Metamorphic Core Complex
Peter Nauffts, ‘15
The Basin and Range Province, which spans much of the western United States, formed as a
result of crustal extension and subsequent normal faulting approximately 10 million years
ago—relatively recently on the geologic timescale. Many of the mountain ranges in this
province are classified as metamorphic core complexes, in which the core of the mountain is
comprised of high-temperature and -pressure metamorphic and igneous rocks that have been
brought into contact with lower-grade rocks at the surface due to faulting. Located in the
northeast corner of Nevada, the Ruby Mountains are one of these metamorphic core
complexes. There is a nonconformity that signals a missing piece of the geologic history;
rocks that are 500 million years old have been dragged next to rocks only 20 million years
old. Our research focuses on refining the timescale of this process.
To do this, we traveled to the Ruby Mountains, where we sampled a host of different rock
types from various structural levels and locations. We focused on two rock types in
particular: the titanite-bearing marble of Verdi Peak, and the more infrequent garnet-bearing
schist outcrops. With this suite of rocks, we hope to be able to use their U-Pb half-lives to
constrain the timing of the tectonic events that juxtaposed these rocks, thereby refining age
estimates regarding the timing and tempo of the evolution of the metamorphic core complex.
Titanite itself can be dated, while garnet is particularly interesting in that it generally traps
other minerals. In this case, we hope to find monazite and zircon inside of the garnets, again
for their radioactive footprint.
Furthermore, we will be looking at peak mineral assemblages and textures in detail under the
petrographic microscope. With this information, we can produce preliminary estimates of
peak temperature and pressure conditions. Lastly, we will use an electron microprobe to
measure compositional changes within minerals to determine more precisely the peak
temperature and pressure conditions. For this project, key minerals include garnet, biotite,
muscovite, hornblende, and plagioclase feldspar.
Faculty Mentor: Emily Peterman
Funded by the Kibbe Science Fellowship