Investigation of reported radiometric anomalies associated with sub-economic iron mineralisation at the Bob Nob prospect, which is situated approximately 8 miles north-west of Arkaroola Homestead, has comprised ground magnetics and scintillometry with follow-up geological mapping and surface traverse channel rock sampling. This work suggested that the anomalous radioactivity, which rises to a few times background in quartz-feldspar breccias occupying shear zones in schistose basal Adelaidean rocks found adjacent to igneous contacts, is related to potassium-rich granites carrying accessory thorium-bearing rare earth minerals (monazite, xenotime). Multielement assaying of surface chip samples for other trace metals showed that the prospect area in general carries insignificant mineralisation.