Journal article
Deformation and exhumation of the Mount Igikpak region, central Brooks Range, Alaska
Special papers (Geological Society of America), Vol.360, pp.111-132
2002
DOI: 10.1130/0-8137-2360-4.111
Abstract
The Mount Igikpak-Arrigetch region exposes a crustal section more than 15 km thick that includes the highest-grade metamorphic rocks in the central Brooks Range. We carried out detailed field mapping and thermochronologic analyses along a north-south transect from the deepest part of the crustal section, near Mount Igikpak, to its northern flank. Metamorphic grade along the transect ranges from upper greenschist grade around the Mount Igikpak orthogneiss to very low grade in the Endicott Mountains allochthon to the north. Evidence of two foliations is found throughout the metasedimentary section. The S (sub 2) fabric controls the metamorphic layering and the distribution of map units. (super 40) Ar/ (super 39) Ar analyses from white mica in the lowest-grade rocks indicate that peak metamorphism associated with the development of the S (sub 1) foliation occurred before 112 Ma, probably owing to crustal thickening caused by collision of an island arc against the Arctic Alaska margin. The dominant foliation (S (sub 2) ) formed during rapid cooling from hornblende closure temperature (500+ or -50 degrees C) ca. 98 Ma to biotite closure temperature ( approximately 300+ or -50 degrees C) by ca. 90 Ma. Mineral and elongation lineations associated with S (sub 2) plunge to the north, and associated kinematic indicators show top-to-the-north shear, reflecting north south extension of the crust in mid-Cretaceous time. The episode of extensional deformation took place on a crustal scale and resulted in tectonic exhumation of the core of the orogen. The driving mechanism may have been gravitational collapse of crust that was overthickened during the preceding collision.
Details
- Title: Subtitle
- Deformation and exhumation of the Mount Igikpak region, central Brooks Range, Alaska
- Creators
- Jaime Toro - West Virginia UniversityP. B GansWilliam C McClellandTrevor A Dumitru
- Contributors
- Elizabeth L Miller (Editor) - Stanford UniversityArthur Grantz (Editor)Simon L Klemperer (Editor)
- Resource Type
- Journal article
- Publication Details
- Special papers (Geological Society of America), Vol.360, pp.111-132
- Publisher
- Geological Society of America (GSA)
- DOI
- 10.1130/0-8137-2360-4.111
- ISSN
- 0072-1077
- eISSN
- 2331-219X
- Alternative title
- Tectonic evolution of the Bering Shelf-Chukchi Sea-Arctic margin and adjacent landmasses
- Language
- English
- Date published
- 2002
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984229300702771
Metrics
24 Record Views