A New Key Paleomagnetic Pole for the 1.8 Ga Kaapvaal Craton: Implications for Paleoproterozoic Apparent Polar Wander and Paleogeographic Reconstruction.

Dykes are ideal targets for paleomagnetic studies because (i) they experienced a rapid cooling and represent snapshots of the Earth's magnetic field, (ii) they contain minerals which can be dated to establish their precise crystallization ages, (iii) they represent excellent time indicators of paleostress to infer plume-head impact on the crust which is pivotal for supercontinent reconstructions, (iv) individual dyke represents a single cooling unit, which limit site duplication like it can be the case for a single massive intrusion. In this study, two N-trending, one SE-trending and twenty-four NE-trending dolerite dykes intruding the Archean granitoid basement over an area of 55 000 km² in the northeastern Kaapvaal craton were paleomagnetically sampled. High-stability magnetizations were isolated from twenty-seven dykes; seven of which yield precise baddeleyite U-Pb ages between 1.88 and 1.83 Ga. These remanences, which mostly occurred as positively inclined directions are interpreted as primary based on antipodal groupings as well as several positive baked contact tests. The existence of dual polarity primary remanence directions recorded by distant dykes, combined to available ages suggest that the 1.8 Ga magmatism is a widespread event in the Kaapvaal craton and involved multiple magma pulses. Combining the primary magnetization among sites and existing radiometric ages further allow us to evaluate the reversal rates of the Earth's magnetic field at the time interval spanned by the studied dykes and to constrain the existing magnetic barcode for the Kaapvaal craton. Slight grouping differences of mean sites confirm that the paleosecular variation has been adequately averaged out. Large groupings differences, however, cannot be explained by paleosecular variations and are interpreted in the context of the 1.8 Ga true polar wander path previously reported from other cratons. Our primary directions are compiled with reliable existing results to provide the best-constrained yet developed 1.8 Ga key paleomagnetic pole for the Kaapvaal craton. Our new key paleopole provides additional constraints for Kaapvaal craton's latitudinal drift in Paleoprotezoic, with which test the existing paleogeographic reconstructions for the Columbia/Nuna supercontinent.