Continental subduction, deep crustal melting

and exhumation of ultrahigh-pressure rocks

 

 

 

Continental crust can subduct to, and return from, mantle depths. The record of this deep subduction (and return) is in ultrahigh-pressure (UHP) metamorphic complexes, some of which seem to have been exhumed very rapidly. Our group is investigating highly deformed migmatites (containing crystallized melt) in the Western Gneiss Region of Norway to determine their pressure-temperature-time-deformation history relative to the pods and lenses of metabasaltic UHP rocks (eclogite) that occur within the migmatite. We are interested in determining whether (and if so, how) partially molten crust is important in the metamorphic and tectonic history of subducted continental crust, and in evaluating the conditions of deformation in mylonite zones that host some of the (U)HP rocks. The first results of this work are published in Gordon et al. (2013) – Lithos. Current work focuses on the conditions of deformation recorded in high-strain zones in coexisting migmatite and eclogite.
 

Field photograph of a metabasaltic eclogite (partially retrogressed to garnet amphibolite) in migmatite.

 

 

 

This research involves current PhD students Roxanne Renedo and Megan Korchinski, former PhD student Stacia Gordon (PhD - 2009), colleague Haakon Fossen (Univ of Bergen), and UMN faculty Christian Teyssier and Donna Whitney.