Annual report for EL 247 Keep River for the year ending 29-6-1974

Abstract

Exploration activity at the SE margin of the Bonaparte Gulf Basin was intensified in 1973/74 but field work had to be confined to EL's held by AAM because the joint venture between AAM and Placer-Conwest had not been approved by the Government at that stage. Previous work on this EL, carried out before June 1973, included mapping and drilling. Results of exploration elsewhere in the Bonaparte Gulf Basin convinced AAM to carry out an airborne magnetometer survey over large parts of the basin. This survey was flown by Geometrics early in 1974. A total force G-803 Proton Magnetometer was used. Flying height was 100m above mean terrain; line spacing was 500m. The attached Residual Magnetic Intensity contour map at a scale of 1:25,000 shows the area of the EL which was covered by the survey. The NNE trending magnetic contours on the E side of the EL represent the E flank of the extended Burt Range Syncline. The steepening of the magnetic gradient in the S of the EL coincides with the flank of a basement high which occurs just outside the EL. A steep magnetic gradient is always of interest because it could mean that stratigraphical traps could have developed which might have caused precipitation of Pb-Zn from metal-bearing brines moving from the Bonaparte Gulf Basin during compaction of sediments. The magnetic contour map shows numerous minor flextures of contour lines whose significance is not readily understood. They could coincide with faults. Field work in 1974/75 will make use of the valuable magnetic data and IP work and drilling will be to a certain extent guided by this information.