Distribution and characteristics of metamorphic belts in the south‐eastern Alaska part of the North American Cordillera

• Published in: Journal of Metamorphic Geology
• Main Authors: BREW, D. A., HIMMELBERG, G. R., LONEY, R. A., FORD, A. B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1992
• Subjects: Glacier Bay; Stikine; Archipelago; glacier; Alaska
• Online Access: http://dx.doi.org/10.1111/j.1525-1314.1992.tb00097.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1992.tb00097.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1992.tb00097.x

The Cordilleran orogen in south‐eastern Alaska includes 14 distinct metamorphic belts that make up three major metamorphic complexes, from east to west: the Coast plutonic–metamorphic complex in the Coast Mountains; the Glacier Bay–Chichagof plutonic–metamorphic complex in the central part of the Alexander Archipelago; and the Chugach plutonic–metamorphic complex in the northern outer islands. Each of these complexes is related to a major subduction event. The metamorphic history of the Coast plutonic–metamorphic complex is lengthy and is related to the Late Cretaceous collision of the Alexander and Wrangellia terranes and the Gravina overlap assemblage to the west against the Stikine terrane to the east. The metamorphic history of the Glacier Bay–Chichagof plutonic–metamorphic complex is relatively simple and is related to the roots of a Late Jurassic to late Early Cretaceous island arc. The metamorphic history of the Chugach plutonic–metamorphic complex is complicated and developed during and after the Late Cretaceous collision of the Chugach terrane with the Wrangellia and Alexander terranes. The Coast plutonic–metamorphic complex records both dynamothermal and regional contact metamorphic events related to widespread plutonism within several juxtaposed terranes. Widespread moderate‐ P/T dynamothermal metamorphism affected most of this complex during the early Late Cretaceous, and local high‐ P/T metamorphism affected some parts during the middle Late Cretaceous. These events were contemporaneous with low‐ to moderate‐ P , high‐ T metamorphism elsewhere in the complex. Finally, widespread high‐ P–T conditions affected most of the western part of the complex in a culminating late Late Cretaceous event. The eastern part of the complex contains an older, pre‐Late Triassic metamorphic belt that has been locally overprinted by a widespread middle Tertiary thermal event. The Glacier Bay–Chichagof plutonic–metamorphic complex records dominantly regional contact‐metamorphic events that affected rocks of the Alexander ...