Annual report for year ending 24-05-1974 on EL 402 Djumburla West

Abstract

As no major gamma-ray anomalies were recorded, no samples of the core were assayed. Bleaching has been recognized in all three holes drilled. This bleaching appears to be correlated from carnotite-bearing sandstones on surface down-dip through all three holes. The bleaching recognized in the core could be indicative of the barren interior of roll-front type uranium mineralization when considering the percolation of mineralized solutions in a roll-type minero-genetic context (Brondi and Carrara, 1973). The presence of the unconformity at the base of the Mt. Eclipse Sandstone along with faulting and fracturing observed in all three' holes, suggests that structure may play an important part in the localization of uranium. Within the Patmungala Syncline three diamond drill holes were drilled between 8th November and 21st November, 1971, each hole was terminated at a maximum depth of 182.88m bringing the total accumulated depth to 548.64m. In preparation for a further drilling programme, the cores were relogged in detail using the same parameters and standard controls as in Section A of this report. Since the object of the drilling programme within the Patmungala Syncline was to obtain stratigraphic information of the Mt Eclipse Sandstone, all these holes were collared and terminated in this formation. Drill sites were selected in order to enable a considerable overlap of the holes. This aim was not accomplished. Nevertheless, the Mt. Eclipse Sandstone was penetrated in an almost continuous section approximately 1,240 to 550in above its base. The prevailing rock type is a uniform, coarse grained feldspathic sandstone. Iriterbeds of shales and siltstones are frequent in the core of NC-DD) 4 and to a lesser extent in NC-DD 5 and 6. Within the total penetrated sequence, the amount of coarse grained sandstone increases from top to bottom. Thin but striking conglomeratic beds were observed in all three holes and quartz pebbles and cobbles occur remarkably frequently. The predominant rock colours in all three holes are pale to moderate grayish-red. Light grey colours are to be found at a depth of 110.64 to 129.50 m only in NC-DD 4. In the fine-grained core sections, red and greenish clay pellets cause a speckled appearance. Compared with the values of Dingo's Rest South drill holes, the ratios are relatively low. The high proportion of coarse sandstone penetrated in holes NC-DD 5 and 6 in the basal portion of the Mt Eclipse Sandstone is obvious. The values correlate with the sandstone/shale ratio. The almost identical values are noteworthy. An average value of 4.3 for the above three holes seems to represent the original Mt Eclipse Sandstone colour.