Magnetic Investigation and 2½ D Gravity Profile Modelling across the Beattie Magnetic Anomaly in the Southeastern Karoo

Abstract

The southeastern Karoo Basin is considered to be one of the most prospective area for shale gas exploration in South Africa. The basin has several igneous intrusions and an interesting magnetic anomaly, the Beattie magnetic anomaly (BMA) is seen on the magnetic map of South Africa crossing the basin in a NE-SW direction. To date, the source of the BMA and interconnectivity of the igneous intrusions are not well understood. In this study, we investigate the interconnectivity of the igneous intrusions and possible location of the source of the BMA using magnetic and gravity methods. The gravity model results showed that the igneous intrusions are interconnected at depth, which probably pose threat by increasing the risk of fracking the Karoo for shale gas exploration. The modelling result reveals that the BMA tends to divide into two anomalies and continue to trend in an NE-SW direction. The anomaly become stronger and or broader with depth which could be an indication that the source(s) is deep, possibly a buried magnetic body in the basement. The average depth to the top of the shallow and deep magnetic sources was estimated to be approximately 0.6 km and 15 km, respectively.