GEODYNAMIC EVOLUTION AND THERMAL HISTORY OF THE CENTRAL FLIN-FLON DOMAIN, TRANS-HUDSON OROGEN - CONSTRAINTS FROM STRUCTURAL DEVELOPMENT, AR-40 AR-39 AND STABLE-ISOTOPE GEOTHERMOMETRY/

Shear zones in the Flin Flon area record five episodes of development. These have been studied using structural analysis and Ar-40/Ar-39 the rmochronology. Deformation occurred as a result of collision between t he Archean RaeHearne and Archean Superior plates during the Trans-Huds on Orogeny (1900 to 1700 Ma). The geodynamic evolution encompasses a t ransition from island are supracrustal development (similar to 1900 Ma ) to tectonic mountain building under brittle-ductile conditions (>186 0 Ma), two episodes of ductile lineation-schistosity (L-S) shear zones on the prograde metamorphic path (1860-1810 Ma), and two episodes of retrograde displacement between 1790 and 1690 Ma, during final suturin g of the Archean cratons with Paleoproterozoic assemblages. Metamorphi sm evolved in three stages. Contact aureoles to granitoid bodies forme d at 1860-1840 Ma. Hornblende hornfels facies Ar-40/Ar-39 ages indicat e cooling through 500 degrees C at similar to 1840 Ma. This was follow ed by regional heating (burial), which produced regional peak thermal recrystallization at similar to 1820-1790 Ma, under lower greenschist to lower amphibolite conditions. Lastly, retrograde metamorphism took place during unroofing between 1790 and 1690 Ma, with a regional cooli ng rate of 2 degrees C/m.y.