Palaeomagnetism of Mafic Dykes from the Eastern Bushveld Complex (South Africa)

A palaeomagnetic study has been conducted on dykes that intrude the c. 2 Ga eastern Bushveld Igneous Complex (BIC). The dykes have previously been assumed to be of Karoo (Jurassic) age based on their NE-SW orientation. Palaeomagnetic data, however, demonstrate that these dykes are Precambrian in age (1800-2050 Ma) and perhaps close to the Early Proterozoic Bushveld age. Both normal (three dykes) and reverse (two dykes) polarity directions are identified, and a positive reversal test attests to a primary magnetisation where secular variation has been averaged out. 40Ar/39Ar dating is currently in progress to verify this age.