The Wopmay orogen is a Paleoproterozoic accretionary belt preserved to the west of the Archean Slave craton, northwest Canada. Reworked Archean crystalline basement occurs in the orogen, and new bedrock mapping, U–Pb geochronology, and Sm–Nd isotopic data further substantiate a Slave craton parentage for this basement. Detrital zircon results from unconformably overlying Paleoproterozoic supracrustal rocks also support a Slave craton provenance. Rifting of the Slave margin began at ca. 2.02 Ga with a second rift phase constrained between ca. 1.92 and 1.89 Ga, resulting in thermal weakening of the Archean basement and allowing subsequent penetrative deformation during the Calderian orogeny (ca. 1.88–1.85 Ga). The boundary between the western Slave craton and the reworked Archean basement in the southern Wopmay orogen is interpreted as the rifted cratonic margin, which later acted as a rigid backstop during compressional deformation. Age-isotopic characteristics of plutonic phases track the extent and evolution of these processes that left penetratively deformed Archean basement, Paleoproterozoic cover, and plutons in the west, and “rigid” Archean Slave craton to the east. Diamond-bearing kimberlite occurs across the central and eastern parts of the Slave craton, but kimberlite (diamond bearing or not) has not been documented west of ∼114°W. It is proposed that while the crust of the western Slave craton escaped thermal weakening, the mantle did not and was moved out of the diamond stability field. The Paleoproterozoic extension–convergence cycle preserved in the Wopmay orogen provides a reasonable explanation as to why the western Slave craton appears to be diamond sterile.
↵* Present address: British Columbia Geological Survey, Box 9333, Stn. Prov. Govt., Victoria, BC V8W 9N3, Canada.
↵† Present address: 3126 Westridge Place, Victoria, BC V9E 1C8, Canada.
↵1 Northwest Territories Geological Survey Contribution 0097; Earth Science Sector Contribution 20160164.
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- Received April 18, 2016.
- Accepted September 16, 2016.
- Published on the NRC Research Press Web site at http://cjes.nrc.ca on September 27, 2016.
- Published by NRC Research Press