Paleomagnetism and U-Pb age of the 2.4 Ga Erayinia mafic dykes in the south-western Yilgarn, Western Australia: Paleogeographic and geodynamic implications
We present results from a paleomagnetic study of the previously undated Erayinia dykes intruding thesouth-western Yilgarn Craton. The U–Pb TIMs baddeleyite age of these dykes is now 2401 ± 1 Ma, whichis about 10 m.y. younger than the 2418–2410 Ma Widgiemooltha dyke swarm. The paleomagnetic studyisolated a stable primary remanence with steep downward direction, and the paleomagnetic pole (22.7◦S,150.5◦E, A95= 11.4◦) is similar, but not identical to that of the previously studied Widgiemooltha dykes.We interpret this difference as the result of the movement of the Yilgarn Craton toward the pole at∼1◦/m.y. angular speed, which is comparable with tectonic plates’ velocities during the Phanerozoic.Paleomagnetic polarities of Widgiemooltha and Erayinia dykes suggest that at least one geomagneticreversal occurred between these two magmatic events. The estimated amplitude of geomagnetic secularvariations at c. 2400 Ma is slightly higher than predicted by the existing models for the last 5 m.y. at the c.64◦latitude. The paleomagnetic data and patterns of c. 2.6–2.1 Ga mafic dyke swarms permit the recentlysuggested reconstruction of the Paleoproterozoic supercontinent.
Геолого-географический факультет
Paleomagnetism and U-Pb age of the 2.4 Ga Erayinia mafic dykes in the south-western Yilgarn, Western Australia: Paleogeographic and geodynamic implications