Paleomagnetic pole from the Yilgarn B (YB) dykes of Western Australia: no longer relevant to Rodinia reconstructions

The paleomagnetic pole from the Yilgarn B (YB) dykes of Western Australia was for many years considered to be the only primary pole for Australia in the interval 1050-700 Ma, and has been used to constrain reconstructions of the Neoproterozoic supercontinent Rodinia. We conducted a detailed paleomagnetic study of one of the YB dykes, resampling the same outcrops from which a positive baked contact test was reported previously. Our results yield a negative baked contact test, and, combined with petrographic and rock magnetic data, indicate that the YB dyke magnetisation is a secondary overprint. The YB dyke pole should no longer be used in testing Rodinia reconstructions. Comparison with the apparent polar wander path for Phanerozoic Australia suggests the YB magnetisation is Mesozoic in age, although rocks along the western margin of the Yilgarn Craton preserve Early Paleozoic Rb-Sr biotite ages. (C) 2001 Elsevier Science B.V. All rights reserved.