EL 3106 Annual report for period 17 April 2004 to 16 April 2005

Abstract

Exploration for unconformity style uranium deposits in the second year of tenure consisted of: integration of new geophysical data with interpretation of mapping data and rock chip geochemistry data from work conducted in 2003 to identify new anomalies and target areas for ongoing work; drilling of 314 regional-scale RAB holes for 4341 m throughout the tenement to determine bedrock geology, identify blind anomalies and alteration systems, and to geochemically characterise existing prospects with a modern multi-element suite; geological reconnaissance and prospecting around established prospects and anomalies; infill outcrop sampling to study clay mineralogy and geochemistry; and ground follow-up and sampling of radiometric anomalies identified in 2003. Logistical, access and environmental tasks undertaken to achieve these aims included: an upgrade of access tracks and clearing of 100 km of RAB routes; an extensive archaeological site clearance of all RAB routes; establishment of a temporary base camp for the drilling phase of work; and creation and population of an environmental database for the tenement. Based on exploration work carried out in 2004, the interpretation of Cahill Formation in the Arrarra Project tenement area is considered unlikely and all outcrops formerly assigned to this formation are now correlated to the Nourlangie Schist. This does not greatly alter the uranium potential of the tenement, as this unit is known to contain carbonaceous lithologies. It may also partly correlate to the South Alligator Group, which contains iron and carbonate rich lithologies in the central Pine Creek Orogen. Further stratigraphic studies are important to future exploration in this area. Interpretation of airborne magnetic and Tempest data has led to the development of a bedrock geology map and a working structural interpretation map. Both these maps will be tested and refined using other datasets and drilling during 2005. A number of areas of interest have been identified for follow up. RAB drilling and outcrop sampling conducted in 2004 were successful in establishing, more accurately, the bedrock lithology distribution at tenement scale, which will lead to the future development of a solid geology map. The eastern half of the tenement appears to be amphibolite facies Myra Falls Metamorphics, composed of muscovite-quartz-biotite-feldspar-garnet schist and quartz sweats. This is bounded from the greenschist facies muscovite-major terrain-bounding fault. Zamu Dolerite (now amphibolite) dykes and sills are common on both sides of the inferred fault. Oenpelli Dolerite is more prolific than first interpreted and probably encompasses 40% of the near-surface Proterozoic geology of the tenement. A thin capping of Mamadawerre Sandstone is also present in some regolith-covered areas. RAB drilling essentially confirmed the distribution pattern for the Mamadawerre Sandstone as determined from Tempest interpretation. RAB drilling also confirmed mineralisation at historic prospects and determined the lithologic, alteration, geochemical, Pb isotopic, spectral and petrographic characteristics. However, structural data are still lacking in these areas. Highest results include: 377 ppm U and 27 ppb Au at Mamurri Hill, 79 ppm U and 97 ppb Au at Two Knobs, 35 ppm U and 25 ppb Au at Arrarra west, and 38 ppm U over 12 m at Injardil. Unusual talc rocks at Two Knobs contain up to 1380 ppm Ni and 10 ppb Pd. Follow up of many airborne radiometric anomalies proved to be disappointing. Most were related to regolith or could not be found in the field. However, new geochemical and alteration anomalies have been identified in several areas from RAB drilling and outcrop sampling. These include Running Creek, Bagoose, Redstar, RAB79 and Blob. The best results from these areas include: 122 ppb Pt and 54 ppb Pd at RAB79, 10 ppm U and elevated PGE at Redstar, and 8 ppm U at Bagoose. Thorium anomalies associated with the Mamadawerre Sandstone are still the subject of microprobe studies, but present data suggest it is contained in a number of different heavy mineral grains at specific stratigraphic levels, not necessarily palaeoplacers. Intense chlorite and sericite alteration has been identified at several prospects and at discrete RAB sites, including Running Creek, Arrarra, Mamurri Hill, Injardil and Yibulin. This alteration is typically spatially associated with uranium, basemetal and PGE anomalism. However, some uranium anomalies are not obviously associated with alteration, apart from bleaching or reddening of the host rock. The main elemental association in the Arrarra tenement appears to be: U, Au, Pd, Pt, K, Mg, Cu, Co, Ni, Zn, As, Be, Li, V, W and Rare Earth Elements (in particular those with middle atomic weight). This is probably an over simplification, as there may have been several overlapping mineral systems active in this tenement.