Date of Graduation

Summer 2022


Master of Natural and Applied Science in Geography, Geology, and Planning


Geography, Geology, and Planning

Committee Chair

Matthew McKay


The Salmon River suture zone in west-central Idaho, USA records the tectonic processes where island arcs, similar to modern-day Japan, were accreted to the North American continent in the Jurassic and Cretaceous periods (160-90 million years ago). This suture zone contains metamorphic rocks that were buried deep within the crust at depths of 20 kilometers or more and have subsequently been brought to the surface. The exhuming processes responsible for the metamorphic rocks in the Salmon River suture zone remains unclear. Two competing hypotheses have been proposed to explain the transport of the rocks from the Salmon River suture zone to the surface: (1) buoyancy changes in the crust from lithosphere delamination or (2) thrust faults bringing rocks to the surface. I present apatite closure temperature estimates with apatite, zircon, and rutile ages to test the two competing hypotheses that have been proposed to explain the transport of the rocks from the Salmon River suture zone to the surface. U-Pb radiometric ages and closure temperature estimates have been collected from the mineral's apatite, zircon, and rutile to investigate age and cooling trends in deformed igneous intrusions. U-Pb apatite ages record cooling temperatures from a 350-500 °C cooling window, this can be refined depending on the grain size of apatite. When combined with garnet, hornblende, muscovite and biotite ages and closure temperatures, a full multi-mineral temperature time path can be created to give insight on the exhumation processes of the region.


closure temperature, U-Pb, apatite, zircon, geochronology, island-arc terranes, exhumation, salmon river suture zone

Subject Categories

Geochemistry | Geology | Tectonics and Structure


© Colleen Grace Rankin

Open Access