Deciphering cryptic P-T-d-t histories in the western Thor-Odin dome, Monashee Mountains, Canadian Cordillera: A key to unravelling pre-Cordilleran tectonic signatures

作者：Spalla M Iole^*; Zanoni Davide; Williams Paul F; Gosso Guido

来源：Journal of Structural Geology, 2011, 33(3): 399-421.

DOI：10.1016/j.jsg.2010.11.014

• P-T-d-t paths
• HT exhumation
• HT transposition
• Tectonometamorphic memory

A detailed structural and metamorphic study along a transect from the core of the Thor-Odin dome to its western margin (South-eastern Canadian Cordillera) has allowed the reconstruction of the P-T-d-t history estimating PT changes, during successive fabric development. The dome comprises a recumbently-folded and transposed Proterozoic high-grade basement and Late Proterozoic-Palaeozoic metasedimentary cover, characterised by a regional foliation (S-T). An inferred, nearly-isothermal decompressional path, from a maximum depth of ca. 40 km, transgresses the "maximum relaxed geotherm", consistent with exhumation during lithospheric extension. Contrasting pre-S-T PT conditions indicate that different units followed different PT paths before S-T development. Traces of these early and variable structural and metamorphic re-equilibration steps are preserved in meter-scale boudins and granular-scale domains poorly affected by transposition. The various paths represent events, from Palaeoproterozoic to Proterozoic Rodinia break up, to Jurassic-Cretaceous convergence and final exhumation in the Eocene. Much of the deformational and metamorphic history may have been accumulated before onset of S-T. However, the early structural history is overprinted, and mineral assemblages and their relative ages are mostly obscured by S-T development. A glimpse of the earlier geologic history is possible only by combining micro-structural analysis and PT estimates.

• 出版日期2011-3