WYOMING-KAAPVAAL LINK CA. 2.7 GA AND EVIDENCE FOR A LATE ARCHEAN SUPERCONTINENT

New U-Pb baddeleyite geochronology on mafic dikes exposed in the Bighorn and Beartooth Mountains of the Wyoming craton establish several pulses of late Archean mafic magmatism ca. 2.71 Ga, ca. 2.69 Ga, and ca. 2.67 Ga. Crystallization ages are based on both ID-TIMS and in-situ SIMS U-Pb methods. The orientations of these dikes, along with those of previously dated swarms, suggest at least two possible mantle plume heads: an older, ca. 2.71 Ga center located in southern Montana, potentially related to the Stillwater layered mafic complex, and a younger, ca. 2.69 Ga center near the Rendevous metagabbro in the Teton Range of western Wyoming. Dike swarms with similar pulses in ages have been reported from Kaapvaal craton, including a radiating swarm and 2.67 Ga center that may have fed the scarce 2.67 Ga dikes in Wyoming. Additional evidence for a Wyoming-Kaapvaal connection comes from the coexistence of high-pressure (12 kbar) metamorphism ca. 2.7 Ga on both cratons. Linking these metamorphic belts places north-eastern Kaapvaal along present-day western Wyoming, which is consistent with the mafic dike trends on both cratons. Preliminary paleomagnetic data from the newly dated swarms in Wyoming establish paleolatitudes that are similar to those for Archean Kaapvaal craton. By 2.2 Ga, the paleopoles diverge however, so rifting of Wyoming-Kaapvaal must have occurred between 2.7 and 2.2 Ga. Paleomagnetic data from Pilbara, Yilgarn, Zimbabwe and Superior and geologic similarities with Slave permit reconstruction of these cratons to the proposed Wyoming-Kaapvaal continent. All of these cratons further share derivation from Hadean, high-µ (²³⁸U/²⁰⁴Pb) mantle reservoir(s), so they may have had previous and/or long-lived associations.