Third annual report Ella Creek year ending 25 July 1989.

Abstract

During the third year of tenure CEGBEA drilled eight percussion holes at Lugg's Anomaly and carried out a stream sediment sampling program on EL 4775. At Lugg's Anomaly, eight percussion holes totaling 437m were drilled to test the zone of surface radioactivity to a maximum depth of 62m. No uranium mineralisation was encountered. A fence of five drill holes on Section 1200 E, designed to test the northern radiometric and ROAC anomalies at their intersection with pronounced E-M and magnetic breaks, encountered a sequence of siltstone, chert and carbonaceous shale beneath surface laterite and lateritic rubble. The sediments were variably weathered and silicified, showing similarities in both gross lithology and the degree of silicification with many partially tuffaceous sections of the Mt Bonnie Formation observed elsewhere in the western part of the Pine Creek Geosyncline. Taking the carbonaceous shale as a marker horizon, the sequence appears to be strongly disjointed by a swarm of sub-vertical reverse faults, which probably parallel the jointing observed in a nearby sandstone outcrop (see figure). Pyrite, ex-pyrite skeletons, sericite and limonitic quartz were observed in drill-chips and pan concentrates from all levels. The lateritic profile is best developed on the ridge on which the prospect is located. A silicified and ferruginised surface zone is underlain by bleached clays then strongly weathered rock to a maximum depth of 36m. Towards the base of the hill on it's northern side, the profile elements became progressively thinner and less distinct, although the surface silicification zone seems to expand again at around 1325 N, perhaps as a result of talus accumulation. A second fence of two holes was drilled on Section 1300 E to test the southern line of ROAC and radiometric anomalies near the inferred sandstone contact. The lithologies and weathering profile encountered were similar to those in the previous section, although carbonaceous shale was absent. Drill hole EC6 failed to reach the sandstone contact itself, which appears to dip southwards at this location. A final hole EC8, was sited on the sandstone contact near the northwestern corner of the grid, close to the 250 cps surface radiometric contour. The hole encountered black siliceous ironstone from 31m, apparently intercalated with weathered sandstone. The ironstone was not, however, anomalously radioactive. Slight to moderate water flows were observed in all holes, believed to be associated with fracture seepage. The strongest flow, from drill hole EC8, was estimated by the bucket method after half an hour's flushing, at around 700 to 800 gals/hr. Stream Sediment Sampling As part of a regional survey throughout the Rum Jungle Project area, a number of stream sediment samples were collected for geochemical analysis from EL 4775 during January and February 1989. Site locations are shown on an accompanying Manton Dam 1:100,000 map. At each site a 5kg sample of active channel sand, sieved on site (in most cases wet) to minus 860 micron, was collected for cyanide leach, while a heavy mineral concentrate was panned from the nearest trap. All analyses were carried out by Australian Assay Laboratories (AAL) in Townsville. Results are presented on an accompanying map.