Application of UAV-borne Magnetic Survey in Diamond Exploration: A Case Study over Kimberlite-Carbonatite Intrusion from Khaderpet, Eastern Dharwar Craton, South India

ABSTRACT Application of drone/unmanned aerial vehicle (UAV)-borne magnetometer (MagArrow) survey in diamond exploration is presented as a case study over diamondiferous kimberlite pipe intruded with carbonatite at Khaderpet within the Wajrakarur Kimberlite Field (WKF), south India. The kimberlite clan rock (KCR) of Kaderpet is expressed as a chloritised kimberlite- granite breccia that shows characteristics of an ultramafic lamprophyre. Owing to good response given by WKF kimberlites for magnetic surveys, a magnetic sensor is chosen in this investigation. Ten E-W traverses covering a total of 15- line km were conducted over an area admeasuring 1.8 sq. km in 35 minutes which may consume a week’s time in traditional ground magnetic survey. The acquired magnetic data revealed a strong magnetic ‘low’ of the order of -130nT in the reduced to the pole (RTP) image where carbonatite amidst granitoid- kimberlite breccia crops out. The magnetic ‘low’ anomaly of this survey matches with the KCR outline interpreted by earlier workers. The results of this survey have been verified with conventional ground magnetic survey which confirmed the presence of the anomaly (magnetic ‘low’) representing kimberlite granite breccia- carbonatite against a ‘high’ magnetic area represented by granitic/gneissic country rock in the surroundings. In this investigation, it is interpreted that the diamondiferous carbonatite hosted by granite chloritised kimberlite breccia is observed to extend to a depth of 7.3 to 41 m from the ground surface, which is consistent with the drilling results of previous exploration. This investigation showed that the drone-borne magnetic surveys can differentiate the anomaly/causative body within a background of country rock to locate anomalies corresponding to possible kimberlites and related rocks elsewhere in the cratonic terrains, provided other geological, geochemical and indicator mineral evidences also support.