Tracking the Late Jurassic apparent (or true) polar shift in U-Pb-dated kimberlites from cratonic North America (Superior Province of Canada)

Different versions of a composite apparent polar wander (APW) path of variably selected global poles assembled and averaged in North American coordinates using plate reconstructions show either a smooth progression or a large (∼30°) gap in mean paleopoles in the Late Jurassic, between about 160 and 145 Ma. In an effort to further examine this issue, we sampled accessible outcrops/subcrops of kimberlites associated with high-precision U-Pb perovskite ages in the Timiskaming area of Ontario, Canada. The 154.9 ± 1.1 Ma Peddie kimberlite yields a stable normal polarity magnetization that is coaxial within less than 5° of the reverse polarity magnetization of the 157.5 ± 1.2 Ma Triple B kimberlite. The combined ∼156 Ma Triple B and Peddie pole (75.5°N, 189.5°E, A95 = 2.8°) lies about midway between igneous poles from North America nearest in age (169 Ma Moat volcanics and the 146 Ma Ithaca kimberlites), showing that the polar motion was at a relatively steady yet rapid (∼1.5°/Myr) pace. A similar large rapid polar swing has been recognized in the Middle to Late Jurassic APW path for Adria-Africa and Iran-Eurasia, suggesting a major mass redistribution. One possibility is that slab breakoff and subduction reversal along the western margin of the Americas triggered an episode of true polar wander

A precise U-Pb zircon/baddeleyite age for the Jasra igneous complex, Karbi-Analong district, Assam, NE India

Five Cretaceous alkaline-carbonatite igneous complexes are reported from the Assam-Meghalaya Plateau, These alkaline intrusions have been interpreted to be coeval and associated with the 117-105 Ma Ra­jmahal-Sylhet flood basalt province. With the existing age information it is possible that this alkaline magmatism may be a late magmatic stage of the Ra­jmahal-Sylhet large igneolls province. Therefore, it is essential to determine high.precision ages for these alkaline complexes in order to understand the de­tailed temporal evolution and genesis of this basaltic and alkaline magmatism. Out of five igneous complexes, Sung Valley, Swangkre and Samchampi have been dated, but tbe emplacement ages of the other two, i.e, Jasra and Barpung, are poorly constrained. The present communication reports a new, high­ precision U-Pb zircon/baddeleyite age for a djfferentiated portion of gabbro phase of the Jasra igneous complex

Long-lived deformation history recorded along the Precambrian Thelon and Judge Sissons faults, northeast Thelon Basin, Nunavut

The ENE-striking Thelon and Judge Sissons faults of south-central Nunavut are well-preserved, and record long-lived dextral transcurrent movement with complex reactivation and fluid flow histories. The faults cut across Archean gneisses, Paleoproterozoic plutons, and a Mesoproterozoic sedimentary basin in the Rae domain of the western Churchill Province. They formed and were reactivated during multiple deformation events beginning with an initial faulting event at 1830-1760 Ma, followed by an epithermal faulting event at 1760-1750 Ma and late reactivation events at 1600-1300 Ma. The initial faulting event produced the core-damage zone architecture of the faults. Damage zones are characterized by multiple fracture sets, quartz veins and hydrothermal crackle breccias, surrounding core zones defined by multiple mosaic to chaotic breccias and cataclasites with dextral slip indicators. The epithermal faulting event is expressed by the presence of crosscutting comb, crustiform-cockade and lattice-bladed quartz hematite carbonate veins, and is likely associated with a magmatic event of similar age. The late reactivation events resulted in the formation of irregular, non-cohesive crackle to mosaic breccias and gouges, which became the primary pathways for uranium-bearing hydrothermal fluids and the formation of unconformity-type uranium deposits. The Thelon and Judge Sissons faults are similar to other major continental faults in the Rae domain (e.g. McDonald fault, Wager Bay shear zone), which formed during the Paleoproterozoic Taltson-Thelon and Trans-Hudson orogenies, and to modern analogues, such as the Karakorum, Altyn Tagh, and Hunan-Jaingxi faults, which formed during the Himalayan-Tibetan orogeny and experienced prolonged hydrothermal and even hot spring activity.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author