The large Kangaroo Dam exploration licence covers the mostly concealed western portion of the Palaeoproterozoic Mount Woods Inlier, a large block of variable magnetic intensity lying to the east and south-east of the Coober Pedy Ridge and the...
The large Kangaroo Dam exploration licence covers the mostly concealed western portion of the Palaeoproterozoic Mount Woods Inlier, a large block of variable magnetic intensity lying to the east and south-east of the Coober Pedy Ridge and the Mabel Creek Inlier. These three basement terranes abut an interpreted Archaean age cratonic area to their south and west. The area contains major regional structures (including the Karari Fault Zone) and is traversed by several prominent north-westwards trending structures along which significant thicknesses of Permian sediments have been deposited. These latter structures show considerable magnetic relief, which was inferred to indicate strong alteration in the buried basement rocks, as is borne out by existing drillhole data for the eastern Mount Woods region. Extensive pre- and post tectonic alteration, in the form of haematite±magnetite±sulphide breccias, iron introduction into metasediments, and calcium-iron silicate alteration, have been reported. Basement outcrop in the subject area is confined to a quarry exposure in its south-west corner, and there are limited outcrops of Gawler Range Volcanics and Archaean gneisses situated further away to the south and south-west, outside of the tenement. From 2001 to 2003, EL 2760 was part of the Mount Woods Joint Venture formed between the tenement holder, Goldstream Mining NL (now IMX Resources Ltd), and project operator, Anglo American Exploration (Australia) Pty Ltd (Anglo). Fieldwork under the joint venture commenced in late 2001, just before the discovery nearby on EL 2563 of the Prominent Hill copper-gold-silver deposit by the Minotaur Resources - BHP Billiton - Normandy Exploration et al. JV consortium, during November 2001. Initial exploration by Anglo involved a comprehensive review and compilation of previous work which identified the potential of the area for hosting craton margin magmatic nickel deposits, besides recognising the presence of a number of aeromagnetic and gravity targets having potential for IOCG style mineralisation and possibly also for Broken Hill style base metal mineralisation. The most interesting geophysical feature was a north-west trending zone of high aeromagnetic relief which it was thought could denote shallowly buried Fe alteration within the buried basement. Aboriginal cultural heritage clearance surveys were completed there with the Antakirinja Mutuntjarra Native Title claimants, to allow the conduct over the period June-August 2002 of a 1402 station ground gravity regional infill survey (read at 200 m x 800 m and 200 m x 1600 m station spacing), and reconnaissance soil sampling above gravity anomalies (221 samples collected on 400 m x 400 m and 400 m x 1600 m grids). Exploratory RC drilling, of 14 vertical and inclined holes for 2030 m, was carried out by Anglo between October and December 2002 and in September 2003 over four selected geophysical targets (MW9, MW11, MW12 and MW15). A total of 517 composite drill cuttings samples were selected from basement portions of these drillholes to be analysed for a multielement suite. Weak PGE-Ni-Cu mineralisation was noted from hole ARC025 located on the MW11 prospect, where up to 0.49 g/t Pd+Pt+Au is associated with pyrrhotite veinlets intersected at the bottom of the hole. No mineralisation was encountered in the other holes. 39 of the RC drill cuttings samples were examined petrographically by consultant Graham Teale, and he also made limited examinations of samples from a nearby historical drillhole. He identified two pyroxene granulites subcropping within the broad drill traverse made over the MW11 prospect, which he thought represent an uncommon rock unit in the Mount Woods Inlier, and he believed they might indicate that this portion of the inlier is in fact more closely related to the Coober Pedy Ridge lithological package. A single 4 km long line of 200 m moving loop ground SMARTEM survey was acquired by Quadrant Geophysics in June 2003 across the MW15 bullseye gravity anomaly, which formed a potential nickel sulphide target, this concept being based partly on geochemical evidence from one existing drillhole. The TEM data were interpreted as showing a lens of saline water within a palaeochannel aquifer, but no other conductive features worthy of drilling. Additional gravity surveying (57 stations) was completed over MW15 early in 2003 to assist with modelling of the IOCG target area. For this purpose also, a 49.7 line km Sirotem survey was completed by Solo Geophysics along 25 lines over the MW11 and MW15 prospects during July 2003, utilising both 200 m and follow-up 100 m loops. Weak TEM anomalism and IP late time effects were detected at the MW15 prospect, but gave no firm indications of a massive sulphide conductor, so this anomaly was then surveyed with ~18 line km of ground magnetic profiles to generate a robust model of the magnetic anomaly as to its extent and depth. Notwithstanding the importance of all this detailed exploration work, when later viewed across the Mount Woods Project tenements as a whole, the regional tenor of the results of its drilling and of all of its geophysical and geochemical surveys was considered by Anglo to downgrade the potential for finding an economic IOCG deposit, and the company subsequently withdrew from the joint venture on 11/2/2004, whereupon management of the subject Kangaroo Dam licence was returned to Goldstream. In 2004, Ian Garsed of Garsed & Associates was contracted by Goldstream to conduct a detailed assessment of exploration conducted over its entire Mount Woods Project acreage, which included the Kangaroo Dam area. Five geophysical targets were identified here using gravity grids and interpreted geology. During late September 2004, a single inclined 248 m deep RC percussion drillhole, KDRC001, was drilled by Goldstream to test the basement rocks at MW11 prospect beneath the bottomhole anomalous Pt-Pd-Au intercept that had been encountered by Anglo. The hole was inclined at 63 degrees and drilled towards azimuth magnetic north. From it a total of 114 drill cuttings samples were submitted for assaying, and encouraging results were received, with a best reported intercept of 2 m @ 1.78 g/t Pd+Pt+Au recorded within an 18 m wide interval assaying 0.53 g/t from below a downhole depth of 202 m. The Pd:Pt ratio is of the order of 5:1. The intercept is associated with an ~20 km long geophysical feature that is interpreted to be a metagabbro body. The attitude of the mineralisation was not known at this stage, and therefore lay open in all directions. Following this intersection of anomalous PGE mineralisation in KDRC001, a check was made of the analytical results from all of Anglo's drillholes ARC001 to ARC029 to see if in fact they had been sufficient analysed for PGE, and it was found that less than 20% of the 1074 samples submitted by Anglo had been assayed for these trace metals. Subsequently, a selection of old sample pulps from the RC holes were submitted for a more thorough PGE analysis. Goldstream stated that the KDRC001 mineralisation is an important and exciting PGE discovery within a region otherwise well known for IOCG mineralisation, and will much enhance the known mineral potential of the highly prospective Mount Woods Domain. Exploration activities undertaken during the fifth and final year of EL 2760, prior to its renewal for another 5-year term, consisted of the completion of one exploratory RC percussion drillhole, gridding and ground magnetic surveying over three prospect areas, and geophysical modelling of historic Western Mining Corp. prospect-related IP data. 401 archived drill cuttings samples from Anglo's previous drillholes on this licence were re-analysed for Au, Pd, and Pt, and the returned results showed that the content of these particular elements is mostly low, with weakly anomalous values recorded in a few holes. The best results were obtained from ARC019 which contains 99 ppb Pd from 75 to 78 m depth (within a zone 66 to 87 m @ 47.6 ppb Pd), and ARC020 which contains 3 m @ 123 ppb Au from 37 m depth. Eleven ground magnetic survey lines (for a total of 12.5 line km) were completed over the KD1, Anomaly 9 and Snaefell prospects during May 2005, with readings taken at 5 m intervals along them, in order to accurately locate targeted aeromagnetic anomalies. These surveys confirmed the presence of the aeromagnetic features, and modelling of their magnetic data indicated that they were easily testable drill targets. Previous WMC dipole-dipole IP data gathered over the Cetus, Snaefell, and Aquilla prospects were acquired in digital form from PIRSA by Goldstream and were reprocessed in June 2005 by Zonge Engineering, using 2D smooth-model inversions, to determine if any untested targets were present. The work identified strong chargeability anomalies on all of the original IP survey lines. A combined percussion and diamond drillhole program was initiated to follow up the anomalous PGE mineralisation intersected in drillhole KDRC001. During October 2005, a single inclined RC percussion hole, KDRC002, was completed to 94 m depth, to test a subtle magnetic anomaly seen to the north of KDRC001. Minor amounts of magnetite were intersected, but the assay results were low for base metals and PGE. Nickel sulphide fire assay analyses were carried out on re-sampled anomalous 4m composite drill cuttings from hole KDRC001 for the depth interval 190 to 248 m. The 20 samples sent off contained anomalous PGE values with maxima of 0.38 ppm Pd (201 to 202 m), 1.26 ppm Pd (207 to 208 m), and 3.28 ppm Pd (213 to 214 m). Another 34 samples from this hole were assayed with conventional ICP methods to provide continuous 1 metre assay coverage across three intervals: 56 to 68 m, 190 to 202 m, and 204 to 214 m. The more precise sampling confirmed the anomalous PGE mineralisation contained in the original 4 metre composite samples. The uppermost interval, in the basement weathered zone, contains 0.19 ppm Pd from 60 to 65 m depth. 5 samples of the mineralised rock from KDRC001 were sent to Pontifex for mineragraphic and petrological examination. Their studies showed that the Pd and Pt sulphide mineralisation, consisting of pyrrhotite and pyrite with a maximum concentration of about 2.5%, is present in a hornblende-pyroxene rich zone that may represent skarn-type alteration of metasediments or metapyroxenite. This occurs within a sequence of quartz-plagioclase-garnet gneisses.