14 - Very High-Pressure Epidote Eclogite from Ross River Area, Yukon, Canada, Records Deep Subduction

Abstract

High-pressure metamorphic rocks (blueschist and eclogite) are preserved along the length of the North American Cordillera. Occurrences of blueschist and eclogite form part of a discontinuous belt more than 1500 km long. The high-pressure metamorphic rocks occur in coherent units as bodies up to several hundred meters thick. Recent studies have suggested that epidoteeclogite can form at relatively high pressure, overlapping the quartzcoesite PT curve. In addition, there have been recent advances in the study of geothermobarometry of very high-pressure rocks using different calibrations of geothermobarometers and PT pseudosections. The nature and origin of high-pressure metamorphic rock crust have a bearing on the deep crustal geometry of the mountain belt, and thus the understanding of accretionary orogens. The Canadian part of the North American Cordillera was built onto a plate with a long history of contraction and extension prior to orogenic development in the late Paleozoic.