Rates, Conditions, and Scales of Mass Transfer From the Mantle to the Crust: Insights from Earth’s Youngest UHP Terrane
Ultrahigh-pressure (UHP) terranes record the subduction of crustal material to mantle depths as well as the relatively rare exhumation and return of this material to the surface. The rates, scales, and conditions under which these processes have occurred have significantly affected the geochemical evolution of Earth and have great influence on the tectonic evolution of convergent plate margins. On the D’Entrecasteaux Islands, southeastern Papua New Guinea (PNG), a series of domes contain the youngest known ultrahigh-pressure (UHP) eclogites and associated gneisses. The PNG UHP terrane is unique for two reasons: 1) it is exposed within an active, rapidly moving plate tectonic system that includes extension partly due to continental rifting; and 2) of all UHP terranes, this area exposes—by far—the greatest volume of crystallized melt in abundant leucusomes and large granodiorite plutons. In order to understand 1) the UHP metamorphic history; 2) the timing of melt emplacement ,and 3) the complete exhumation and deformational history of the eclogites and surrounding gneisses, a series of leucosomes, dikes, and eclogites were analyzed by U-Pb ID-TIMS zircon geochronology. Establishing the timing of these exhumation and melting processes has provided the framework for a larger seismic and geodetic research program geared to reveal how buoyancy drove the exhumation of subducted crustal material from mantle to crustal depths within ~ 3 myr.
Host: Mike KrawczynskiRegister to attend via Zoom