P-T-D-t paths for Mesoproterozoic supracrustal rocks: a new window into the elevated geotherm and intraplate deformation of the ca. 1.4 Ga Picuris Orogeny

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Most of Earth’s mountain belts have formed at the boundaries of tectonic plates, where the stresses from plate motions are powerful enough to fold, break, and pile up rocks. However, a few mountain belts have formed far away from high-stress plate boundaries, and they suggest that tectonic plates are not always entirely strong and rigid. This project will investigate one of these unusual plate-interior mountain belts to better understand how strong tectonic plates can be weakened and deformed from the inside out. The Picuris Mountains of northern New Mexico contain sedimentary and volcanic rocks that were deposited around 1.5 billion years ago and then rapidly deformed and metamorphosed, capturing a record of a rare plate-interior mountain building event. By studying the structures, minerals, chemistry, and radiogenic isotopes of the Picuris rocks, investigators will determine how heat, stress, and time worked together to warp the North American plate interior. This research will use state-of-the-art analytical approaches and instrumentation to address long-standing tectonic mysteries, as well as train up to five graduate and undergraduate students in conducting high-level earth science field and lab research. The investigator and student researchers will also create a field trip for members of the public with mobility challenges highlighting the geology, mineral resources, and landscapes of a plate-interior mountain belt. Intraplate orogenesis challenges the paradigm of rigid tectonic plates and provides clues to the long-term, nonlinear evolution of continents, cratons, and plate strength. This project will focus on the Picuris Mountains of New Mexico, where mountain-building occurred far inboard of the presumed active Laurentian continental margin 1.4 billion years ago. Investigators will extract the Pressure-Temperature-Deformation-time (P-T-D-t) record of the Picuris Orogeny preserved in rare rocks with Mesoproterozoic protoliths as a means to elucidate the mechanism(s) of the ca. 1.4 Ga intraplate orogenesis. The Principal Investigator, two graduate students, and one or more undergraduates will perform field work; construct detailed P-T-D-t paths for Mesoproterozoic supracrustal rocks using modern petrologic and structural approaches; perform U-Pb titanite and zircon dating to establish the absolute timing of Picuris metamorphism and deformation; and use whole-rock and zircon trace-element geochemistry to determine the tectonomagmatic setting of Mesoproterozoic volcanic rocks. Additionally, the Principal Investigator and a graduate student will build a digital field guide to Precambrian outcrops for Wisconsin geoscience-curious community members, especially including those with mobility challenges. Lessons learned from developing this accessible field experience will be shared with UW-Madison faculty to inform efforts toward making field-based geoscience education more inclusive. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.