A large north-south orientated area centred ~45 km north-west of Port Lincoln was taken up to explore for possible buried Archaean komatiite-hosted nickel, volcanic hosted massive sulphides (base metals), orogenic lode gold, BIF-hosted iron ores...
A large north-south orientated area centred ~45 km north-west of Port Lincoln was taken up to explore for possible buried Archaean komatiite-hosted nickel, volcanic hosted massive sulphides (base metals), orogenic lode gold, BIF-hosted iron ores and sedimentary (roll-front redox cell) uranium mineralisation. Regional mapping and new interpretations of aeromagnetic data have indicated that the principal bedrock sequence known to occur in the area, the Hutchison Group, may also include members of the Katunga Dolomite and Middleback Jaspilite, all located within the Cleve Domain, bounded to the east by the Kalinjala Mylonite Zone and to the west by an unnamed shear zone. The Moody Suite, probably emplaced during the ca 1720 Ma Kimban Orogeny, appears to form a pluton, raising the possibility of the presence of skarn type mineralisation in a region about 12 km to 15 km east of Cummins. During the first licence year, all initial work was conducted by Intermet Resources’ joint venture partner Uranoz, and thus was directed at finding Tertiary sedimentary type uranium deposits. A detailed airborne magnetic/radiometric/DTM survey was acquired in September-October 2007, covering the entire tenement area; 11,678 line km were flown along east-west flight lines spaced 100 m apart, using a 50 m mean sensor height above the ground surface. This survey provided high quality data which assisted Uranoz in defining basement structures which it expected could have an influence on the morphology of palaeochannels within the tenement. Next, 64 groundwater samples were collected from water bores and laboratory analysed for a multi-element suite. Results obtained suggested that uranium dissolved in the local groundwater could be sourced both by leaching from felsic igneous basement minerals and also through remobilisation from sediment hosted accumulations previously deposited from these groundwaters. Uranoz' desktop examination of geological and topographic maps, combined with field data collected during sampling of groundwater from water bores, defined areas that were interpreted as likely to be underlain by concealed paleochannels. The most uranium-anomalous groundwater sampled was located in or adjacent to the known Wanilla Palaeochannel. A comparison of the groundwater trace metal geochemistry showed some match against that recorded for the Goulds Dam and Honeymoon deposits in the Frome Embayment. Target areas for further work were chosen where high airborne radiometric counts for uranium aligned with water bore locations showing anomalous uranium in the groundwater. During licence Year 2, Lincoln Minerals performed a review of past exploration data and reports, and acquired a detailed ground gravity survey over two selected areas in the north of the tenement which it thought could hold potential for buried stratabound haematitic iron ore because of some subdued linear magnetic features. 1158 new gravity stations were read during May-June 2008 on 100 m x 400 m regular or offset grids. The resulting gravity data revealed residual anomalies ranging in amplitude from 1.2 mGal to 2.0 mGal, with half-widths of about 250 m to 550 m. Relying on the earlier published advice of geophysical consultant Jim Hanneson, the EL 3702 JV partners assumed that such anomalies can originate from haematite bodies not necessarily associated with magnetite-rich BIF. A field investigation was made of the anomalies to eliminate from drill-targeting those where outcrop and sub-crop evidence showed that they were due to the presence of mafic rock. Those which were chosen for drilling lay in areas of no outcrop where the magnetic response would suggest that bedrock consists of Hutchison Group. The densities of samples of different lithotypes outcropping on the licence area were measured to inform the modelling of the gravity data which was used to make a final selection of drill targets. During licence Year 3, Lincoln Minerals undertook the following work: - aircore and RC drilling to test the Cummins district iron ore targets identified from modelling of its new gravity data; and - RC drilling to test a discrete magnetic anomaly located about 578000 mE, 6197600 mN, in the east of central part of the licence area ~3 km south-west of Yallunda Flat. In April 2009, five gravity targets were tested by combined aircore and RC drilling : three located in an area 10-12 km north of Yallunda Flat, and two located about 4.5 km and 7 km due north-east of Cummins. 31 vertical open holes were completed for a total penetration of 1272.5 m. Another three holes (CMAC001 - CMAC003) for 174 m were drilled to test the magnetic anomaly. Drill traverses were set out at a high angle to anomalies, with collars normally about 100 m apart. No bodies of haematite were encountered, although some ironstone drill chips were recorded. It was not clear from the drilling whether the gravity anomalies are caused by rock type or by variations in weathering. The depth of weathering varies from about 10 m to 40 m. Several amphibolite dykes up to 15 m thick were intersected when drilling the magnetic anomaly. Assaying of selected drill cuttings samples did not return any anomalous values.
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