U–Pb zircon crystallization ages determined by isotope dilution – thermal ionization mass spectrometry (ID–TIMS) and laser ablation microprobe – inductively coupled plasma – mass spectrometry (LAM–ICP–MS) for 13 intrusive units in the Neoarchean Snare River terrane (SRT) provide tight constraints on the timing of crust formation and orogenic evolution. Seven metaluminous plutons were emplaced over ~80 Ma from ca. 2674 to 2589 Ma, whereas six peraluminous bodies were emplaced in a ~15 Ma interval from ca. 2598 to 2585 Ma. A detrital zircon study yielded an age spectrum with peaks correlative with known magmatic events in the Slave Province, with the ca. 2635 Ma age of the youngest detrital zircon population providing a maximum estimate for the onset of sedimentation. This age contrasts with evidence for pre-2635 Ma sedimentation elsewhere in the SRT, indicating that sedimentation was protracted and diachronous. Evolution of the SRT can be subdivided into four stages: (i) 2674–2635 Ma — formation of a metaluminous protoarc in a tonalite–trondhjemite–granodiorite (TTG) – granite–greenstone tectonic regime (TR1) and coeval with early turbidite sedimentation; (ii) 2635–2608 Ma — continued turbidite sedimentation, D1/M1 juxtaposition of turbidites and protoarc lithologies prior to ~2608 Ma, and metaluminous granitoid plutonism; (iii) 2608–2597 Ma — onset of TR2, collision of Snare protoarc with Central Slave Basement Complex, D2/M2 crustal thickening and mid-crustal granulite-facies metamorphism, sychronous with metaluminous and peraluminous plutonism; and (iv) 2597–2586 Ma — orogenic collapse, D3/M3 mid-crustal uplift, granulite-facies metamorphism, and waning metaluminous and peraluminous plutonism. The distribution of igneous rocks yields an "orogenic stratigraphy" with an older upper crust underlain by a younger synorogenic mid-crust. These data can be used to provide constraints for the interpretation of the Slave – Northern Cordillera Lithospheric Evolution (SNORCLE) Lithoprobe transect.

New field and U–Pb zircon data from the south-central Wopmay Orogen (south of 65°N) establish crystallization ages of basement and plutonic phases and bring to the forefront questions on the architecture of the orogen. The complex and extensive >3300–2575 Ma basement domain was derived from the adjacent Slave craton. Paleoproterozoic supracrustal rocks, dominated by an extensive pelitic–psammitic sequence with basal arenite, conglomerate, and carbonate, unconformably overlie this basement. Pre- to post-kinematic Paleoproterozoic plutons intrude both basement and overlying strata and crystallized at 1877, 1867–1862, and 1858–1850 Ma. The first pulse of plutonism constrains an early generation of metamorphism and deformation to younger than 1877 Ma and is corroborated by metamorphic zircon in Archean basement. The interval from 1867 to 1862 Ma brackets ductile deformation in granite and granodiorite intrusions; although corresponding structure in the metasedimentary strata is equivocal. Post-kinematic ca. 1858–1850 Ma plutons were coeval with localized high-grade metamorphism and concomitant recrystallization of Archean basement. The absence of older (>1880 Ma) phases of the Hepburn intrusive suite in south-central Wopmay Orogen demonstrates a previously unrecognized north–south plutonic dichotomy and that the historical assignment of Calderian metamorphism to ca. 1885 Ma may be too old. The designation of part of the area to a klippe of Hottah terrane is not compatible with field and zircon age data which shows that basement and the overlying strata can be tied directly to the Slave craton. The study raises questions regarding the tectonic relationship between the Hottah terrane and Slave craton.

We present a U-Pb detrital zircon age and provenance study of a sequence of metasedimentary rocks in the northwestern Thor-Odin high-grade gneiss dome within the Omineca crystalline belt of the Canadian Cordillera. Despite strong overprint by defor mation and metamorphism, we successfully analyzed the age and provenance of six samples collected at various structural levels, using U-Pb detrital zircon laser-ablationinductively coupled plasma-mass spectrometry (LA-ICP-MS) analysis.The Thor-Odin dome consists of Paleoproterozoic basement and a metasedimentary cover sequence of previously unknown age and tectonic signifi cance. Our results indicate that the oldest units of this sequence may be Paleoproterozoic, and some of the oldest known metasedimentary rocks in the Canadian Cordillera, originally deposited on top of Laurentian basement rocks. The youngest rocks are Devonian and deposited shortly before the onset of widespread Late Devonian to early Mississippian igneous activity in the Selkirk Domain or Kootenay arc. The cover sequence of the Thor-Odin dome thus preserves some of both the oldest and the youngest (meta)sedimentary rocks deposited between the formation of supercontinent Columbia and the onset of igneous activity and convergence that marked the beginning of Cordilleran deformation and metamorphism. Parts of as many as ~1.4 b.y. of sedimentary history are preserved in the Thor-Odin dome, implying that much information on the sedimentary history of the Canadian Cordillera may be hidden in other Cordi lleran gneiss domes.

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.

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