Report of activities on 03-1961 to 03-1962 and assessment status of prospect ATP 845

Abstract

Work in the Tanami Authority to Prospect during 1961 was confined to the drilling of one hole in the Black Hills district, some 12 miles northeast of the Tanami bore. This hole was collared at an angle of 55' and stopped at 1,063' 6' at an angle of 30 degrees. Expenditure on the Authority to Prospect from 1st January, 1961, to 31st December, 1961, amounted to $15,967 (pounds) of which $11,552 (pounds) is chargeable to diamond drilling. The balance of $4,415 (pounds) covers administrative costs, interpretation of geological, geochemical and drilling data accumulated during 1960 and 1961 and a carryover of expenditure from 1960. Field investigations conducted during 1960 outlined several areas within the AP in which substantial tonnages of siliceous ferruginous bodies and apparently gossanous ferruginous bodies outcropped. One of these areas, the Black Hills 12 to 15 miles northeast of Tanami, contained 43 ferruginous gossanous bodies with an estimated aggregate tonnage of 225,000 tons per vertical foot outcropping over a linear distance of 40,000 feet. Only trace quantities of copper, gold, zinc and silver were detected in outcrop or associated soils but in view of the considerable aggregate tonnage of the ferruginous bodies one drill hole was designed to intersect one of them below the base of oxidation. In view of the extreme contortion (slumping) and random pitch directions of these bodies at outcrop it was deemed expedient to select the target body on the basis of sufficient length to ensure that the hole would not miss the target at the uppermost point at which intersection was desired (400 feet vertical). Some smaller bodies may have had preference on the basis of greater trace metal content at outcrop if the question of pitch could have been resolved. Under the circumstances, however, drilling of these smaller targets would have been an unwarranted risk as the primary objective of the drilling was to determine the nature of the outcropping bodies in their unaltered state. The body selected for drilling lies at the northwestern end of the line of gossans in the South Black Hills . 2,000 feet in length and a maximum of 240 feet in width and was estimated to contain 22,500 tons per vertical foot assaying at outcrop 17.6% Fe, nil-trace Cu, 0.05 - 0.1% Zn, trace Au. Drilling showed these bodies to be pyritic black shale in the primary zone similar to that occurring at White's Rum Jungle. The black shale section was first entered at 430' 3' and ended at 659' 9. Pyrite, and possibly arsenopyrite, up to 10% to 15% occurs throughout this section which comprises black, carbonaceous, severely crumpled shale with occasional inter-beds of a white sandy tuff or quartz-felspar porphyry, which is also pyritic. These latter are correlated with the pods of quartz-felspar porphyry observed in outcrop. Although pyrite is common enough, that encountered in the black shale section of the core is neither sufficiently abundant nor of sufficient crystal size to account for the number and magnitude of the voids observed in outcrop which give these bodies their goasanons appearance. Assay of the black pyritic shale gave contents of 0.35 Zn, nil trace Cu, trace - 1 dwt./ton Ag, trace Au over 166' 1' core length representing about 146 feet true thickness. A positive spot test reaction in the black shale was obtained with an acid solution of ammonium molybdate but this more probably represents arsenate (from arsenopyrite) than phosphate. The footwall of the black pyritic shale was entered at 659' 9' and proved to be strongly laminated talc phyllite which contains sporadic pyrite mineralisation. This lithology persisted to the bottom of the hole at 1,063' 6' except for a fine-grained basic igneous rock, or a metamorphosed calcareous sediment, which can only be described as 'greenstone' and which appears sporadically between 898' and 1,057'. Carbonate occurs as thin bands throughout this talc-phyllite section.