Annual report for McArthur River for the year ending 7 June 1991

Abstract

The tenement bounds approximately 220 km2 of Pre~Cambrian McArthur Group sediments, and includes a 20 km strike length of the highly prospective Emu Fault Zone. The fine grained stratiform H.Y.C. lead-zinc deposit, and numerous minor coarse grained lead-zinc prospects are associated with the Emu Fault Zone immediately north of Annexure 314. The ongoing exploration programme is aimed at potential coarse and fine grained lead-zinc and copper deposits. The consulting group Environmental Resources Analysis Ltd. processed satellite Thematic Mapper and airborne magnetic data from the McArthur Basin. The study provided a structural framework for the basin, and an insight into possible ore forming processes that were active during the formation of known mineralisation in the McArthur River area. Results of the study are being used to formulate the broad exploration concepts for Annexure 314. Geological mapping of target areas is currently being carried out. It is confirming and extending existing detailed mapping which was completed during previous exploration programmes. The mapping is providing significant new insights into the geology and defining exploration targets. A total of 5370 soil samples was collected from the tenement, and assayed for lead, zinc and copper. Sampling was concentrated along fault lines and areas which had not been previously sampled. No significant new anomalous zones were delineated, although a low order copper anomaly was outlined along the Lamont Fault in the southern part of the tenement. Geoterrex Pty. Ltd. flew 1329 line kilometres of airborne magnetics and GEOTEM electromagnetics across the tenement, at a line spacing of 200 metres. The magnetics revealed little detail about the tenement. The GEOTEM survey has provided valuable data, which are being incorporated into geological mapping and conceptual target modelling. In addition, the GEOTEM has outlined numerous low order conductors throughout the tenement. The significance of these is being investigated. An induced polarization-resistivity survey (71 line kilometres) was completed by Zonge Engineering and Research Organisation along the major faults of the Emu Fault Zone. The survey was designed to locate coarse grained mineralisation hosted by brecciated dolomitic rocks. Numerous anomalies were delineated, but those which have been drilled are related to minor amounts of pyrite hosted by resistive rocks. Further drilling is planned for the next Period. A total of 6500 metres of percussion and diamond drilling has tested geochemical, geophysical, geological and conceptual targets throughout the tenement. With the exception of the Amelia Prospect, drilling failed to intersect significant mineralisation. Drilling at the Amelia Prospect returned the best result, where Amelia 26RC intersected 24 m averaging 2.17 percent zinc, including 12 m averaging 4.06 percent zinc from the weathered zone. Drill hole Amelia 24RC intersected 30 m averaging 2.31 percent zinc, straddling the weathered-fresh rock interface. The anticipated programme for the second twelve month term is to include ground electromagnetic and magnetic surveys to locate anomalies delineated by the airborne surveys, induced polarization and resistivity, downhole geophysics, geological mapping and diamond and percussion drilling of selected targets .