Synthesizing EarthScope data to constrain the thermal evolution of the continental U.S. lithosphere

Abstract

In this work, we compile several seismic velocity models publicly available from the Incorporated Research Institute for Seismology (IRIS) Earth Model Collaboration (EMC) and compare subcrustal mantle velocities in the models to each other and to the timing of tectonism across the continent. This work allows us to assess the relationship between the time elapsed since the most recent thermotectonic event and uppermost mantle temperatures. We apply mineral- and physics-based models of velocity-temperature relationships to calculate upper-mantle temperatures in order to determine cooling rates for the lower-crust and uppermost mantle following thermotectonic activity. Results show that most of the cooling occurs in the ∼300–500 million years following orogeny. This work summarizes current estimates of upper-mantle shear velocities and provides insights on the thermal stabilization of continental lithosphere through time.

Geophysical and Geochemical Constraints on Neogene‐Recent Volcanism in the North American Cordillera

“…LAB, lithosphere-asthenosphere boundary. Currie & Hyndman, 2006;Porter et al, 2019;Sleep, 2009;Vitorello & Pollack, 1980). Following the termination of subduction, the start of cooling may be delayed 10 s of m.y.…”

Mapping the Thermal Lithosphere and Melting Across the Continental US

“…Geotherms colors are based on thermotectonic age for their location using the model of R. C. Porter et al. (2019). Orange diamond are basalt melt equilibrium P‐T conditions from this study.…”

“…To produce a velocity contrast of this magnitude between a solid and partially molten rock, a melt fraction, φ > 0.2 is required (Kohlstedt & Hansen, 2015). Such a melt fraction, PORTER AND REID 10.1029/2020GL092197 7 of 10 Porter et al (2019). Orange diamond are basalt melt equilibrium P-T conditions from this study.…”

“…While attributing all mantle seismic variations to temperature and assuming a constant grain size are simplifications of upper mantle conditions, this allows for a baseline estimate of thermal conditions under the continent. For a more detailed discussion of these compositional assumptions and the methodology refer to R. C. Porter et al (2019).…”

“…Dotted lines are seismically derived geotherms for the continental US at 1° intervals. Geotherms colors are based on thermotectonic age for their location using the model of R. C Porter et al (2019)…”