1973 Annual report for EL 744 Lilla Creek

Abstract

Activity in EL 744 during 1973 was aimed at defining the structure and the geological setting of the area, and assessing the uranium potential. The first step was a photo-geological study and preparation of a base map. A radiometric and magnetic airborne survey was undertaken by McPhar Geophysics Pty Ltd but no uranium anomalies were detected. Finally, a geological reconnaissance was carried out, mostly aimed at checking the existing BMR geological map. EL 744 is located in the southern part of the Finke Basin which was filled with fluviatile sediments during the Devonian-Carboniferous time, and thus could be an environment favorable for uranium mineralization. A photo-geological study was undertaken over the whole Finke Basin but unfortunately in EL 744, little information was obtained because the area was small and covered by sand and rubble. A base map was prepared on a scale of 1:8o,ooo (photo scale). Radiometric survey - The survey was carried out by McPhar Geophysics Pty. Ltd. using a single engine Cessna 206 aircraft and an AV-4 four threshold spectrometer with thresholds set to allow discrimination between potassium, uranium and thorium. Ancillary equipment in the aircraft consisted of a radar altimeter, a vertical tracking camera and a six channel light beam recorder. The detector was composed of four 6' x 4' crystals. The ground clearance was 75 m and the spacing 1 km. Total flight lines amounted to 120 km. The data output was of analog form and immediately available to the geologist. The tracking film was developed every day and the flight line path plotted on the photomosaic. The final data was checked in Adelaide by a McPhar geophysicist. Interpretation of the data was made by a company geologist who selected the anomalies on the basis that they were greater than 26 where 6 = N/2 , N is the number of 20 counts per second and is the time constant; Unfortunately no anomaly met this criterion, although high background exists wherever the Horseshoe Bend shale crops out. A magnetic survey was carried out at the same time as the radiometric survey, and used a Geometrics Proton procession magnetometer. The ground clearance was 300 m and spacing 5 km. Total flight lines amounted to approx 30km. The final result was a magnetic contour map prepared by a McPhar geophysicist. A geological reconnaissance of EL 744 was made by two geologists to check the 1:250,000 BMR geological map. This map proved to be accurate and the only formations encountered in the area were the Horseshoe Bend shale and the Crow Point Formation. CONCLUSIONS - No significant uranium anomaly was detected by the airborne radiometric survey of E.L. 744 nor by the field geological reconnaissance. In view of these facts and the smallness of the area, further exploration is not warranted and it is recommended that the area be relinquished.