FEBRUARY 2024 LUNCHEON MEETING
Liane M. Stevens, Ph. D.
presents
Revisiting the Timing of Metamorphism and Deformation During the Grenville Orogeny in the Llano Uplift, Texas
11:30 AM Wednesday, February 21, 2024
at Willow Brook Country Club
3205 W Erwin St.
Tyler, TX 75702
Cost: $25 if you RSVP
$30 at the door if you do NOT reserve
Abstract
Previously published research in the Llano uplift established a 1.3-1.1 Ga timeframe for the Mesoproterozoic Grenville orogeny in Texas based on the timing of igneous crystallization and metamorphism. However, currently available data on the timing of metamorphism in the Packsaddle domain are limited, do not clearly distinguish the first two (of three) recorded metamorphic events, are imprecise and/or ambiguous, and are often not formally published. Advances in analytical methods now allow for high-resolution, in situ monazite and zircon petrochronology, in which U-Th-Pb isotopes and trace elements are analyzed simultaneously from single spot analyses, and geochronologic data, geochemical data, and petrographic observations are integrated. Advances in thermodynamic modeling allow pressure-temperature (P-T) conditions to be determined for metamorphic rocks with evidence of multiple equilibrium assemblages, but that may not produce accurate P-T estimates through traditional geothermobarometry due to high-temperature diffusion or fluid flux during metamorphism. These updated methods provide the opportunity to build knowledge that may lead to greater insights into the Grenville orogeny and Mesoproterozoic tectonics in general.
Biography
Liane Stevens is a metamorphic geologist with research interests in metamorphic petrology, geochronology, and microstructures. She has a B.A. in Geology from Wellesley College, an M.S. in Geology from the University of Massachusetts Amherst, and a Ph.D. in Geosciences from the University of Montana, where she worked on the evolution of the Priest River metamorphic core complex in northern Idaho. Prior to starting as an assistant professor at Stephen F. Austin State University in 2016, Stevens lectured at Bentley University, University of Montana, and Montana State University. She is the 2022 recipient of SFA’s Teaching Excellence Award for the College of Sciences and Mathematics. Current research with SFA graduate and undergraduate students focuses on metamorphic and igneous petrology in the Llano uplift of Texas, and volcanology in southwestern New Mexico.