Whitehorse 2016
Technical Program

SS9:  Tectonic controls on northern Canada’s mineral and petroleum resources 
Organizers / Organisateurs:  Suzanne Paradis & Peter Hannigan
Room / Salle:  T1023
Date:  June-01-16
Time:  10:20 AM
Presenter:  Rosie N. Cobbett

Devonian-Mississippian rifting in Yukon and northern BC;  Implications for exploration of syngenetic and epigenetic mineralization

Cobbett, R.N., Rosie.Cobbett@gov.yk.ca, Yukon Geological Survey, Whitehorse, YT  Y1A 5B7, Crowley, J., Boise State University, Boise, ID, USA  83725-1535, and Berenak, L., Memorial University, St. John's, NL  A1B 3X5

The Devonian-Mississippian Earn Group is a predominantly sedimentary succession that was deposited in extensional basins along the continental margin of Ancestral North America.  This sequence marks the end of passive margin style sedimentation that characterized the deposition along the continental margin from Neoproterozoic until late Paleozoic.

Volcanic rocks (ca. 365 to 363 Ma), laterally discontinuous coarse clastic rocks and locally variable stratigraphy of the Earn Group are all interpreted as evidence of Devonian-Mississippian rifting.  This rifting resulted in normal faulting characterized by horst and graben geometries, with uplifted blocks providing the source for Earn Group sediment.  New mapping northwest of the Anvil District in central Yukon shows that rift-related coarse-clastic and volcanic rocks of the Earn Group are more extensive than previously indicated.  This new mapping also provides additional constraints on the structural framework of the northern Cordillera in the Devonian-Mississippian.  Influx of chert-rich clastic rocks beginning in the Middle Devonian occurs throughout east central Yukon and parts of northern British Columbia and is inferred to be a response to rifting of the Yukon-Tanana arc terrane away from the Laurentian continental margin and subsequent opening of the Slide Mountain ocean.

Major rift-related Devonian-Mississippian faults controlled the distribution of syngenetic mineralization.  They were later reactivated (or inverted) in the Jurassic-Cretaceous and controlled the emplacement of late Mesozoic intrusions and the distribution of epigenetic mineralization.  These compound structures therefore constitute major regional metallotects.