The continuation during 2010 of exploration of the Palaeoproterozoic bedrock in a small area located 60 km west-northwest of Cowell has mainly consisted of the conduct of three shallow drilling campaigns and the examination and analysis of...
The continuation during 2010 of exploration of the Palaeoproterozoic bedrock in a small area located 60 km west-northwest of Cowell has mainly consisted of the conduct of three shallow drilling campaigns and the examination and analysis of downhole rock samples. Early in 2010, new Chinese joint venture partner OM (Manganese) Ltd drilled 357 very shallow auger holes for 1201 m to access unweathered Upper Middleback Jaspilite bedrock at the Jamieson Tank prospect, looking for buried manganese mineralisation, but that work revealed none. So this was followed in the period May to August 2010 by the drilling of 18 deeper inclined RC holes for 738.5 m. Still no significant manganese or iron mineralisation was encountered, nor was it detected by the XRF analysis of RAB and aircore cuttings. One sample of possible graphite-bearing foliated rock, taken from the collar of an anonymous abandoned mineshaft, was sent by Archer Exploration to be examined in thin section to try to gauge its graphite content and typical grainsize of any graphite flakes. The host rock was determined to be a fine grained graphite-quartz schist. Its graphite content was estimated at ~15%, with the visually estimated average crystal/grain size, of what are mostly scattered independent flakes, being about 10 microns thick x 100 microns long. During July-August 2010, Archer Exploration drilled 7 vertical RC holes for 376 m into the Pindari magnetic anomaly. The tenor of the nickel geochemical anomalism found by previous explorer's aircore drillholes was not substantiated by the latest drilling results - instead, it appeared to come from weathering of an amphibolite intruded within the Lincoln Complex. This amphibolite and the surrounding quartz-biotite porphyry are in part sheared, with minor pegmatite veins. Traces of copper sulphides and of native copper were observed when logging the amphibolite drill cuttings, but no anomalous assay values were returned from multi-element analysis, including REE analysis, of the drill cuttings. This drilling campaign, which used a new type of rubber track-mounted lightweight multimode drill rig, experienced equipment problems which prevented any of the RC holes from going deep enough (>150 m) to reach the likely source for a previously recorded EM anomaly. In the 2011-2012 reporting year, Archer Exploration experienced impediments to gaining land access on EL 3711 owing to the seasonal high intensity of grain cropping: effectively, exploration was stymied temporarily as it could only occur when the farmers consented. However, in the south-western corner of the tenement some RC drilling was able to be accomplished on three farms covering the Sugarloaf Hill graphite prospect, in two brief sorties made during March-April 2011 and February 2012, when 7 angled holes for 909 m were completed to obtain fresh graphitic schist rock samples for testing. The samples were examined petrographically, and underwent grain size analysis and mineral separation studies to try to ascertain whether an economic graphite product could be produced from selected logged 'lode' material. The early findings were that the graphite is moderately abundant (15 to 25%), but its average grainsize is very fine. During 2012-2013, additional metallurgical samples were collected by drilling two diamond cored holes at Sugarloaf Hill. These holes were drilled 32 m apart along an open track that crosses the crest of the hill. The first hole was terminated at a depth of 47.8 m because of drilling water loss due to fractured ground conditions; therefore the second hole was taken to a shallower total depth of 34 m. Both holes were drilled at minus 70 degrees declination towards 120 degrees True azimuth, and were collared near some historic graphite working shafts. The drill cores were sampled at 1-metre hole depth intervals for multi-element geochemistry to try to understand the anomalous surface gold values previously recorded in this location. The aggregated tenor of significant mineralised intercepts found within the weathered bedrock is: - in hole SLDD12_001, 36 m @ 500 ppm Cu, 0.1 ppm Au, 0.6 ppm Te, 0.4% S, 3.6 ppm Ag and 9.3% C, and - in hole SLDD12_002, 24 m @ 500 ppm Cu, 0.1 ppm Au, 0.8 ppm Te, 0.4% S, 6.3 ppm Ag and 8.7% C. It was suspected by Archer Exploration that the above mentioned suite of gold alloying trace metals had been scavenged by the carbon content in these rocks. Notably, the highest gold values of 0.574 and 1.130 ppm Au were returned from the sample intervals 41-42 m and 42-43 m in hole SLDD12_001. During the 2013-2014 licence year, laboratory metallurgical testwork to determine how best to efficiently liberate the graphite particles from the silicate minerals in the host schist at the Sugarloaf Hill occurrence was continued, in the hope of being able to generate a high purity product which can be marketed. Additional graphite samples were collected to subject to this research treatment. Archer Exploration reprocessed existing airborne EM data from the Pindari and Galaxy EM anomalies to produce various conductivity depth slice images. Petrographic thin sections of 17 samples of the basement lithologies encountered by the 2010 RC drillholes done at Pindari were examined. Both metasedimentary and ultramafic igneous rock types were identified - the latter have elevated niobium and tantalum contents. During the 2014-2015 licence year, Archer Exploration advanced the gathering of background data to support its draft mining lease proposal for EL 4861. Five shallow auger and rotary mud drilled piezometer holes were constructed at Sugarloaf Hill for monitoring local groundwater flow behaviour beneath the proposed site of a mine ore processing plant tailings storage facility, and another four rotary holes were drilled in a search for groundwater supplies to use for this plant and for one planned for Pindari. A 102 m deep water bore and a 121 m deep water table monitoring well were successfully completed at Pindari. An EM anomaly of interest at Galaxy prospect was drilled by 2 RC holes for 116 m, but problems that arose in maintaining integrity of the collar to the vertical, deeper ARGRC14-007 hole caused it to fail to reach its target depth. During the 2015-2016, 2016-2017, 2017-2018 licence years, no field work was done. Archer Exploration collaborated in an ongoing research programme with the University of Adelaide, which is exploring the use of graphite material from the Sugarloaf Hill deposit as an additive to soils to enhance crop performance. The concept of binding the raw material to fertiliser in order to slow the process of chemical release in sandy soils is being examined, as well as the potential for it to be used as a soil conditioner. The research is progressing well and is now advancing towards field trials. Archer is providing graphite samples from its Sugarloaf Hill drill cores, as needs dictate. During the 2018-19 licence year (to 19th February 2019), no on ground activities were performed. Desktop based work included wireframing the Mn units from historical drilling undertaken by Archer and others.
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