An area centred ~70 km south-southeast of Olary has been explored for buried mineral sands placer deposits that may have formed within the Cainozoic Murray Basin sedimentary cover, as well as for possible economic stratabound iron ore occurrences...
An area centred ~70 km south-southeast of Olary has been explored for buried mineral sands placer deposits that may have formed within the Cainozoic Murray Basin sedimentary cover, as well as for possible economic stratabound iron ore occurrences that might exist in the underlying Adelaidean metasedimentary bedrock. The subject small licence was granted to Iluka Resources and was explored by that company until 2012, when Braemar Iron purchased the ground so that it could evaluate its undercover magnetite iron ore potential. Early work completed by Iluka, targeting Tertiary marginal marine strandline deposits of heavy mineral sands, consisted of the interpretation of filtered airborne magnetic survey data and previous drillhole geological and structural information, followed by the drilling during May 2011 of 19 vertical reverse circulation aircore holes, along two regional traverses laid out to the south of the Anabama Granite pluton, for a total penetration of 1865.5 m. No significant mineralised intercepts were made by this drilling, which had aimed to find embayed beach style marine placer mineralisation. Hole SO1370 returned an intercept of 3.0 m @ 1.3% HM from 61.5 m depth, but all of the other holes had <1.0% HM. When Braemar Iron commenced exploration, they commissioned H and S Consultants in 2013 to perform a regional prospectivity study of the Braemar Iron Formation. On EL 4713, three regional magnetic anomalies, identified as C_4 to C_6, were considered to present some magnetite potential. It was remarked that the magnetic signature of these anomalies is quite different to that of other areas within the Barrata Trough region, being diffused and often consisting of a complex series of sub-anomalies with short strike length. These latter features appeared to be steeply to moderately dipping, and have low to moderate magnetic intensity (0.11 to 0.22 SI). It was thought such signatures could denote the presence of magnetite within shallowly plunging folds occurring in a structural “crumple zone”. However, it was also conceded that the magnetic anomalies might not actually represent the target Braemar Iron Formation, particularly because no trace of this unit had been reported from previous drilling done in the area. At the time, whole rock geochemical analyses of drillhole samples taken from relevant historic SA Mines Department stratigraphic drillholes had returned total iron contents of only 5-7% Fe from material taken near the bottom of each hole. To check the available information, a visit was made in 2015 by Braemar Iron geologists to the SA Government Core Library to inspect stored old drill chips from these particular holes, and that inspection found no evidence of Braemar Iron Formation. So a field reconnaissance was also conducted afterwards, whereupon no such unit could being identified in outcrop, and when preliminary ground magnetic profiles that were read across the C_4 to C_6 anomalies showed little increase in TMI response when compared to background values. Consequently, it was concluded that the subject licence area's perceived iron ore prospectivity had become diminished as a result of carrying out these activities, and it was decided that the tenement should be surrendered.
More +