The prospect is described as an eastern geochemical anomaly featuring a large gravity high.
Legend said the RC rig is being used because it is cheaper and quicker than diamond, yet still provides a platform for downhole EM and allows for diamond tails to chase any deeper targets identified.
Legend's discovered Mawson late last year after a number of years of systematic greenfields exploration.
The company raised A$20 million early this month by issuing new shares priced at 14c each.
The raising was cornerstoned by the explorers two major shareholders, Mark Creasy and IGO.
Shares in Legend were down 3.5% to 13.5c in early trade capitalising the company at $320 million.