2nd Annual report EL 5076 Phillip Creek Project NT

Abstract

The Phillip Creek Project Area encompasses two exploration licences originally granted to Australian Development Limited and now forming part of a joint venture with Newmont Australia Limited. Both licences (EL 5066 and 5076) have a common first anniversary of 29th January, 1988. These licences are part of a larger group of 13 licences within the Tennant Creek district which are the subject of the joint venture. During December 1987 Australian Development Ltd. made application to the Director of Mines to have the 13 licences consolidated into several groups to simplify reporting. Permission was granted during January 1988 for the licences to be consolidated into four (4) project areas with a common anniversary of 29th January.

This project area has been named the Phillip Creek Project as the licences cover parts of the head waters of Phillip Creek and fall within Phillip Creek Station. Geological mapping compiled at 1:12,000 scale by ADL during the 1970's has been converted to 1:10,000 scale. These 1:10,000 scale map sheets are the basic unit of the data base and will be continuously modified and updated as new data becomes available. Reconnaissance geological mapping and systematic annotation of the map sheets has been completed as part of the first pass coverage of the project area. In areas of specific interest more detailed mapping has been completed and the previous mapping has been added to, modified or replaced as the case may be. Detailed geological mapping (1:500) with emphasis on structure has been completed over the Golden Slipper and Bernborough prospects. This work has been based on colour aerial photography flown in May 1988 and presented as 1:25,000 and 1:10,000 scale prints. The aerial photographic survey was flown as a joint venture between. S mining companies with interests in the Tennant Creek field and the NT Department of Lands and Housing and was coordinated by Newmont. A full set of 1:25,000 scale colour prints was acquired to assist with base map preparation and navigation and selected 1:10,000 scale prints have been acquired. Planimetric and cultural base map data with l0 m contour intervals at 1:100,000 has been acquired from ASLIG. The results of the geological mapping programme for year 2 of the project are presented at 1:10,000 scale on map No.1 to No.7 and the geology is discussed under the heading local geology. As an adjunct to the mapping programme four specimens where submitted for petrographic analyses. Final processed digital data for the low level airborne geophysical survey flown by Austirex International Ltd in 1984 was received in April 1988. This data was gridded, enhanced and imaged on Newmont's in house computer image processing system. Images were produced for the aeromagnetic data, the total count radiometric data, the individual Uranium, Thorium and Potassium channels and combinations of these 5 data sets. Following preliminary evaluation of these images the field office was supplied with 35mm slides and A4 size photographic prints of the maximum resolution images of the aeromagnetic data and the potassium channel radiometrics for each 1:10,000 scale sheet area. These products have been used as .aids to the interpretation of geological and geochemical trends in the field. Further analysis of the imaged data has been carried out at the end of the first and second stages of field data collection by interactive interpretation of the images on the image processing facility at Newmont's Perth office. Selected images of the aeromagnetics and radiometric data have been computer film-written and produced at 1:100,000 scale to assist in the assessment of the regional geology and structural history of the field. Inspection of the potassium channel radiometric data shows, as would be expected, a close correlation between areas of strong response and areas of outcropping granite and the larger exposures of acid porphyries. Some what more subtle mid order anomalies are associated with acid intrusive subcrop or areas of shallow residual soil cover. Further mid order anomalism is associated with outcropping and subcropping major sericitic shear zones such as the Mary Lane shear zone and the Nobles Nob - Mt Samuel zone. The Thorium channel data displays somewhat more restricted zones of high response. These zones show semicontinuous halos around the Warrego Granite intrusions as well as highlighting the channels of major drainage systems such as Tennant Creek and Bishop Creek. High response in the Uranium channel is even more restricted than in the other two channels. By far the strongest results come from the tailings dams of the Warrego and Peko concentrators reflecting the uraninite accessory content of the ironstone copper ore. Other zones of anomalous response are associated with the larger outcropping ironstone bodies including Nobles Nob, Mt Sammuel, Skipper, and Northern Star. It was hoped that the Uranium channel data may help to discriminate major mineralized ironstone from barren ironstones however the response seems to be more a function of the surface area of ironstone exposure.

A further feature of note in the radiometric data is the anomalously low response of the major regional quartz veins associated with the later phase of faulting. An interpretation of the regional structure and geology based on geophysical features with emphasis on the aeromagnetic data has been produced by Newmont Senior Geophysicist, Mr M. Flis. This interpretation has identified several major structural features within the four project areas including the Mary Lane shear and the Quartz Hill fault. This interpretation suggests that the granite intrusives are more extensive than depicted on current published maps and supports the observations from the geological mapping programme that many of the granite contacts appear to dip shallowly beneath the Proterozoic sediments. Numerous zones of anomalous magnetic response based not only on magnetic intensity but also on relationships of apparent structural features, where identified. On the Phillip Creek project area two zones of anomalous magnetic response were identified and are designated P1 and P2. Anomaly P1 occurs in the south west corner of the project area 2km NW of the Geopeko Explorer 119 zone. The P1 zone falls over an area of outcropping carbonaceous greywackes and hematitic shales striking ENE and steepening from dips of 35dg in the southern part of the zone to 65dg in the north. It is thought that these exposures represent a stratigraphic level in the upper part of the Black Eye Member. Anomaly P2 corresponds to the Geopeko Explorer 166 zone and lies in the NW corner of the project area. At the surface this zone occurs in a flat area of extensive soil cover that is interpreted to be close to the boundary between the lower Carraman Formation and the Black Eye Member. Subtle trends in the aeromagnetics suggest that the Northern Star ore deposit located 6.5km to the north may be in a marginally higher stratigraphic position.