Northern Monashee Mountains, Omineca Crystalline Belt, British Columbia: Timing of metamorphism, anatexis, and tectonic denudation

摘要: The northern Monashee Mountains lie at the termination of a north-south zone Eocene extension in southern Omineca Crystalline Belt British Columbia. Isotopic, structural, and petrogenetic studies document middle to Late Cretaceous regional metamorphism, two episodes crustal anatexis, period rapid cooling coincident with extension. Partial melting geochemically isotopically similar pelitic sources produced peraluminous granites during postdating metamorphism 100 Ma 63 Ma, respectively. Rb-Sr muscovite-whole-rock isochrons from younger give an age 62.5 ±2.0 Ma. isochron U-Pb mineral ages are similar, indicating that were emplaced into terrane had cooled 500 °C or less by Hornblende, muscovite, biotite K-Ar apatite fission-track 76.3 ±5.8 ( n = 7), 51.4 ±3.5 6), 55.1 ± 2.7 10), 45.0 ±2.9 3) respectively (mean standard deviation). Accelerated cooling, beginning emplacement ending 45 occurred response ramping along crustal-scale thrust fault followed offset on North Thompson normal fault.