Rock Magnetic properties of Proterozoic mafic dykes from the Southern margin of Cuddapah Basin

Abstract

Seventeen basic dykes of Proterozoic age intruding the Archaean basement from the Southern margin of the Cuddapah Basin were studied from five sites for their magnetic characters. NRM intensity (J_n) of the dykes range between 1793 and 57×10⁻³ Am⁻¹ while magnetic susceptibility (χ) ranges from 31 to 303×10⁻⁶ CGS units. Koenigsberger's ratio (Q_n) varies from 1 to 55 for most of the specimens. All the above parameters are indicative of retaining the original magnetization in most of the dykes sampled. Based on the above mentioned rock magnetic properties along with hysterisis studies and low temperature (−196°C) magnetic studies, it is inferred that the main magnetic carrier in these dykes is magnetite in multi domain and mixed domain states. Dykes from Tirupati area seems to be magnetically altered.