Synconvergent exhumation of metamorphic core complexes in the northern North American Cordillera: COMMENT

Evolution of the North American Cordillera

■ Abstract The Cordilleran orogen of western North America is a segment of the Circum-Pacific orogenic belt where subduction of oceanic lithosphere has been underway along a great circle of the globe since breakup of the supercontinent Pangea began in Triassic time. Early stages of Cordilleran evolution involved Neoproterozoic rifting of the supercontinent Rodinia to trigger miogeoclinal sedime...

Tectonomagmatic evolution of Cenozoic extension in the North American Cordillera

The metamorphism and exhumation of the Himalayan metamorphic core, eastern Garhwal region, India

[1] Geothermobarometric together with microand macro-structural data indicate ductile flow in the metamorphic core of the Himalaya in the Garhwal region of India. Peak metamorphic pressure and temperature increase dramatically across the Main Central Thrust (MCT) from !5 kbar and !550°C in the Lesser Himalayan Crystalline Sequence (LHCS) to !14 kbar and !850°C at !3 km above the MCT in the Grea...

Fast Cooling and Exhumation of the Valhalla Metamorphic Core Complex, Southeastern British Columbia

High-grade, migmatitic paragneisses (820°C, 8 kbar peak conditions) of the Valhalla metamorphic core complex experienced the retrograde net transfer reaction (ReNTR): garnet + melt + K-feldspar = sillimanite + biotite + plagioclase during cooling and crystallization of the melt, resulting in an increase in the Fe/(Fe + Mg) of both garnet and biotite at their margins. Diffusion profiles generate...

Tertiary metamorphic core complexes in Sonora, northwestern Mexico

Several ranges encompassing more than 35,000 km 2 of Sonora, Mexico, contain distinctly lineated and foliated granitic and metamorphic rocks that constitute the lower plates of metamorphic core complexes. Penetrative deformation is characterized by gently dipping mylonitic foliation across which northeast trending stretching lineation is everywhere developed. Prominent northwest trending fractu...