Thermotectonic evolution of the Wolverine metamorphic complex, British Columbia: limitations on the use of combined ion exchange and net-transfer reaction geothermobarometry at upper amphibolite-facies metamorphism

Peak metamorphism of the Wolverine metamorphic complex (WMC) occurred at conditions of 770°-830°C and 7.2-10.4 kbars, and was accompanied by partial melting and the development of tight to isoclinal northeast-vergent folds that are axial planar to a transposition foliation. The WMC is modelled as a diffuse northeast-vergent shear zone that formed beneath a southwest-vergent panel of rocks as the orogenic wedge detached and translated northeastward during Mesozoic contraction. Juxtaposition of Middle Jurassic greenschist-facies upper crustal rocks against upper amphibolite-facies rocks of the WMC, which contain Eocene 40Ar/39Ar cooling ages, suggests that the WMC remained at deep crustal levels until it was rapidly exhumed in the Eocene along the normal Wolverine fault. Mineral reaction and disequilibrium textures indicate a near-isothermal decompression path from 7.2-10.4 kbars to below 4 kbars, corresponding to a minimum of 11 km of exhumation prior to cooling below ~650°C.