Ptarmigan Fiord basement-cover thrust imbricates, Baffin Island, Nunavut

Chadwick, T C and St-Onge, Marc R. and Weller, O. M. and Carr, S D and Dyck, B J (2015) Ptarmigan Fiord basement-cover thrust imbricates, Baffin Island, Nunavut. Summary of Activities, 2015. pp. 61-72. ISSN 2291-1235, on-line 2291-1243

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The rocks at Ptarmigan Fiord on the Hall Peninsula of Baffin Island underwent midcrustal deformation during the formation of the Paleoproterozoic Trans-Hudson Orogen. The structural style in the region is dominated by imbricate panels of Archean basement orthogneiss and Paleoproterozoic supracrustal strata, interpreted to have been deformed by thick- skinned ductile thrusting. Basement rocks comprise amphibolite-facies metatonalite, metagranodiorite, metaquartz-diorite and metamonzogranite, and cover rocks comprise amphibolite-facies migmatitic pelitic and semipelitic schist, psammitic schist, amphibolite, calcsilicate and quartzite. The S 1a penetrative foliation is variably present in basement rocks and consis- tently present in cover rocks, and is defined by alignment of biotite, sillimanite and leucogranite that formed before and dur- ing the thermal metamorphic peak. The S 1a foliation was deformed by F 1b isoclinal folds with an amplitude of 100 m. These structures are interpreted as forming during a D 1 east-west crustal shortening event. Basement and cover imbrication oc- curred after the thermal metamorphic peak and is interpreted as D 2 thick-skinned ductile thrusting. Ductile thrust faults at the base of seven basement-cover slices are identified on the basis of repetition of units and strain localization, and are inter- preted as predominantly south-to-southeast verging on the basis of shear-sense indicators. There are two structural panels of D 2 thrust imbricates, one in the northwestern part of the map area and one in the eastern part of the map area. Map-scale crosscutting relationships indicate that the northwestern panel overthrusted the eastern panel on a southeasterly T 2c -di- rected thrust fault, following a F 2b folding event that folded the T 2a basement-cover thrust imbricates in the eastern panel. The Ptarmigan Fiord area contains a world-class exposure of thick-skinned structures as they are spectacularly delineated by belts of distinctive grey-weathering Archean basement rocks and brown- to black-weathering Paleoproterozoic supra- crustal rocks.

Item Type: Article
Uncontrolled Keywords: NILAREP
Subjects: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
Divisions: 05 - Petrology - Igneous, Metamorphic and Volcanic Studies
07 - Gold Open Access
Journal or Publication Title: Summary of Activities
Volume: 2015
Page Range: pp. 61-72
Depositing User: Sarah Humbert
Date Deposited: 04 Apr 2017 11:35
Last Modified: 04 Apr 2017 16:31

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