Polymetamorphic Evolution of theTrans-Hudson Orogen, Baffin Island, Canada: Integration of Petrological, Structural and Geochronological Data

Supracrustal units metamorphosed at mid-crustal conditions within the Paleoproterozoic Trans-Hudson Orogen are preserved within an obliquely exposed continental collision zone on Baffin Island (Canada). Early granulite-facies assemblages yield thermobaro-metric data and phase diagram information that define a steep, com-pressive P^T path segment.These assemblages are bracketed between ca. 1849 and 1835Ma, and are interpreted to result from (1) heat advection by an 1865þ4/^2 to 1848 2Ma Andean-type granitic batholith, and (2) a ca. 1845Ma crustal thickening event associated with accretion of an intra-oceanic arc terrane. A subsequent regional metamorphic event is characterized by the growth of retrograde, upper amphibolite-facies assemblages that define a clockwise, decompres-sive P^T path. Mineral growth is bracketed between 18201 and 1813 2Ma, and is localized within deformation zones associated with the 1820þ4/^3 to 1795 2Ma collision of the Rae and Superior cratons.The metamorphic history of Baffin Island supports a progressive change from plate-margin to intraplate processes within an evolving convergent orogen during the Paleoproterozoic that is similar to those documented in younger collisional belts