** Please join us for coffee and cookies in the GeoCorner Undergraduate lounge (bldg. 320, rm 114) before the talk, at 11:30am! - Seminar will be in room 220~
Extracting the metamorphic record from zircon at the atomic scale
Zircon has been widely used across the geosciences to determine provenance and quantify the nature, timing, and rates of tectonic, magmatic, impact, and metamorphic processes. In many cases, multiple geologic events are preserved within a single grain, such as metamorphic rims on detrital zircon grains. This presentation focuses on the atypical, yet characteristic interface domain observed between igneous cores and younger metamorphic rims in zircon metamorphosed at extreme conditions. Until recently, the small scales of these domains have precluded detailed study. However, recent advances in atom probe tomography now permit 3-D reconstructions of the position and composition of each atom within a specimen. These data reveal nanoscale clusters, planar features and decorated dislocations--each with a unique geochemical fingerprint--that formed along the interface between the zircon core and rim. The spatial distribution and geochemical profiles of these nanoscale features show that each set is produced by different mechanisms that occurred during metamorphism at very-high-grade conditions. These nanoscale features in zircon may provide a new, robust marker for the identification of metamorphism at extreme conditions.
Emily Peterman studies the deep crustal processes that control the evolution of mountain belts in time and space. She is particularly interested in the role of disequilibrium and rheological contrasts during metamorphism and anatectic melting and uses petrology, mineralogy, geochronology, and geochemistry to quantify the timing and rates of metamorphic recrystallization, deformation, and melting at the nano- to kilometer scale. Dr. Peterman received her BA in Geology and Spanish at Middlebury College and her PhD at the University of California, Santa Barbara. She joined Bowdoin College in 2012 where she is presently an Associate Professor in the department of Earth and Oceanographic Science.