Exploration summary report Hidden Mystery South.

Abstract

The area was geologically mapped by D. Tonkin as part of a project covering MCC's 622 to 624 and the surrounding mineral claims. Mudstones of the Carraman Formation outcrop or subcrop over most of the area. Quartz veining is ubiquitous in these sediments. Ironstone lenses, aligned along the Mary Lane shear zone, consist principally of massive black hematite, micaceous hematite and quartz. Shearing is evident in most places. Most ironstones are weakly to moderately magnetic. Away from the Hidden Mystery workings the ironstones tend to become jasperlitic and more siliceous. Abundant ironstone float is common in many places, possibly reflecting more substantial lenses at depth. Small intrusions of lamprophyre were observed in places, but drilling at the Hidden Mystery workings suggest these may be more common than is evident from surface mapping. Laterite crops out along some stream channels. Eleven roch chip samples were taken, the locations are shown on the Soil Geochemistry map. A geophysical interpretation was made on the data that was purchased by Metana from Austirex International Limited. An airborne geophysical survey was conducted by Austirex between June & July 1984. The flight lines were spaced by 200 metres, with tie lines separated by 4000 metres. A proton precession magnetometer was used for data collection. This had a resolution of 0.1 nano Tesla, a cycle rate of 0.5 seconds and a sample interval of 30 metres. The interpretation, indicates that the lease is located on east west striking magnetic units of the Carraman Formation and straddles a splay of the Mary Lane Shear Zone. A ground magnetic survey was carried out by Solo Geophysics. Readings were taken at a height of 8 feet at 5 metre intervals along 40 metre spaced grid lines. Soils are mostly thin and residual and should reflect accurately the geochemistry of the underlying bedrock. From orientation work carried out elsewhere in the Tennant Creek Field, the optimum size fraction for sampling soils was found to be -180 microns. Samples of this fraction were taken over MCC 622 as part of a larger soil sampling programme which covers the Hidden Mystery workings itself. The samples were collected on a 80 x 40 metre spaced grid and submitted for aqua regia/GTA gold analysis. The results are shown on figure 6. There are no significant results within the lease sampled. The highest assay was a spot high of 9 ppb situated on a small massive ironstone outcrop. The structural break interpreted from the aeromagnetic interpretation is not obvious on the ground magnetic contours. Future exploration should include bedrock drilling traverses, to determine the underlying lithology and to investigate the potential for shallow level oxidised or non magnetic mineralisation, especially in the vicinity of the Mary Lane Shear Zone.