Exploration Licence 2704 covering 23 square km surrounding the historic abandoned Mutooroo copper mine, located ~55 km east of Olary, was granted to Havilah Resources NL so that the company could assess the economic potential of the remaining...
Exploration Licence 2704 covering 23 square km surrounding the historic abandoned Mutooroo copper mine, located ~55 km east of Olary, was granted to Havilah Resources NL so that the company could assess the economic potential of the remaining sulphide copper resource at the mine, estimated to be in the vicinity of 8.7 Mt @ 1.8% Cu (Horn, 1973). Some of this resource, as yet unquantified, occurs within a 16 Ha mining lease (ML 4211 / 5678) held by another party, that lies within Havilah’s tenement. Copper was mined at Mutooroo between 1887 and 1914, for a recorded production of approximately 6000 tonnes of 6% copper. The generally secondary copper ore was exploited by more than 15 shafts and shallow pits aligned along a roughly 1.5 km long gossanous lode zone hosted by Palaeoproterozoic amphibolites of the Willyama Supergroup. The primary lode(s) consists of coarse-grained pyrite, pyrrhotite, quartz and lesser chalcopyrite developed in a sericitic altered shear / fracture system that is mostly confined to the amphibolite or near its footwall contact with sillimanite gneiss. In places there are up to three subparallel lodes 0.5–2 m thick within the shear structure. Past drilling had established that overall the mineralised lode / shear zone dips generally at 45 degrees towards the west and strikes towards 014 degrees off magnetic north. While the most recent previous investigation done in the mid-1990s by CRA Exploration had concluded that the remnant Mutooroo copper resource was uneconomic, Havilah’s initial strategy was to carry out a thorough assessment of the previous drilling data using Vulcan 3D mine modelling software. The main objective was to better understand the nature and controls on the Mutooroo lode / shear system in 3D, and to identify any inadequately tested portions of it that with additional strategic drilling could potentially increase the resource base. As the company learned during the first licence year, digital versions of relevant open file reports, mine plans and sections, and all earlier RAB, percussion and diamond drilling data were not available to it to enter into the Vulcan database, so a manual conversion process to digitise these data was begun. Two field trips were made to the area during Year 1 in order carry out reconnaissance mapping and sampling. Observations showed that the local host rock is a massive to weakly foliated medium- grained dolerite. The lode is essentially a coarse-grained quartz-rich pegmatite that is variably greisensed, with the feldspathic matrix mainly replaced by pyrite and minor chalcopyrite. When weathered, this rock resembles a peculiar-looking ironstone with large quartz “eyes”. Unmineralised quartz – muscovite schist commonly seen on the mine dumps probably represents sheared, altered host rock from the fracture / shear zone. A few representative dump samples were assayed and returned anomalous levels of copper and gold. By the end of licence Year 2, Havilah had digitised all available data for the Mutooroo mine prospect, including the past drilling data. Many errors and inconsistencies were found in those, so it was necessary to carefully check all original data sources such as log sheets in order eliminate the uncertainties as much as possible. A final 3D model of the lode zone could not be completed at this time owing to some missing drillholes and to spatial mismatch problems with the variety of surveyed grids that had been used over the years. This necessitated making a field trip to the area to georeference geographical features, plus the locations of old drill collars and lease boundaries, so that a new AMG - based grid system could be used for the database. Havilah's preliminary 3D modelling showed that the Mutooroo mine lode system occupies a steeply dipping bifurcating shear, consequently limiting its potential to contain a low grade copper resource. However, it was thought that the nature of the lode system is analogous to those of many currently successfully mined shear-hosted gold deposits, and so the search strategy was changed towards addressing the possible discovery of a high grade gold zone either within or parallel to the known shear zone. Cobalt-rich sulphide mineralisation was also a plausible secondary target. During licence Year 3, Havilah undertook geochemical resampling of the available Mutooroo drill core, which replicated the generally low gold values in the lode system that had been reported by previous explorers. It was decided to incorporate additional data from the earlier comprehensive electrical geophysical surveys acquired on the prospect into the 3D drillhole / geological model, in order to identify any previously overlooked drill targets that might offer the chance to expand the resource. During licence Year 4, it was found that five earlier holes (MU1 to 5) drilled by Moonta Mining Ltd in 1990 at locations relatively close to the outcrop of mineralisation and the line of old workings had indicated that some potential existed for shallow open pittable copper ore below the level of the old workings, which generally had terminated at the water table and base of oxidation. Therefore, in order to test the potential for shallow open pittable copper ore and/or the occurrence of a high grade gold zone, Havilah drilled 4 new inclined RC holes for 276 m during February-March 2005 at collar positions in between those of the former five 100 m spaced holes. Two of these holes, namely MTRC001 and MTRC004, returned significant intercept widths of massive sulphide that contain potentially economic levels of copper and cobalt (assay maxima 2.2% Cu over 13 m and 2.1% Co over 10 m). During the 2005-2006 reporting period (covering 16 months), work included: - Further 3D modelling of the Mutooroo prospect geology and mineralisation, continuing to integrate new data; - drilling of 43 inclined RC holes (MTRC005 to 047) totalling 4269 m to test the potential for relatively shallow, open pittable, copper-cobalt mineralisation below the level of the old workings. The drilling was completed on traverses spaced 100 m apart with hole azimuths oriented at 90 degrees to the local lode strike. All holes were declined at -60 degrees towards the south-east. Best intersections included 31 m @ 1.71% Cu + 0.18% Co (MTRC044) and 26 m @ 1.55% Cu + 0.18% Co (MTRC045); - flying a trial helicopter-borne 25Hz Hoist EM survey over Mutooroo during August 2005 along two lines totalling 6 line km, using a nominal 30 m mean terrain clearance and 8-10 m sampling interval, to try to detect known mineralisation; and - undertaking a preliminary mining scoping study which indicated an estimated optimized open pit resource to 250 m depth of 11.5 Mt @ 1.1% Cu and 0.096% Co. This is sufficient to maintain a mining operation for a period of at least 11.5 years at an annual throughput of 1 Mt, to produce approximately 10,000 t of copper and 1,000 t of cobalt per annum. Based on the above indications of a profitable mining project, Havilah pegged two Mineral Claims over the prospect, MCs 3565 and 3566. During licence Year 7, a joint venture Memorandum of Understanding was signed in October 2006 between Havilah and Heilongjiang Resources Limited to carry out a mining feasibility study on the Mutooroo deposit. To inform that study, an additional 61 inclined RC percussion holes (MTRC048 to 108) plus extensions to earlier RC holes MTRC004 to 007 were drilled that together totalled 8278 m, with the aim of delineating the deposit's open pittable, copper-cobalt mineralisation down to approximately 200 m below surface over an 800 m x 200 m area within the prospect. The new holes were sited along traverses spaced 50 m apart, at 25 m intervals, and were oriented at 90 degrees to the local lode strike and declined at -60 degrees to the south-east. One-metre bulk samples (10-20 kgs) of drill cuttings were were collected for metallurgical testing, and magnetic susceptibility readings of the cuttings were made every metre from 30 m hole depth (average base of weathering). During licence Year 8, a total of 117 drillholes (MTRC/MTDD 109-225) for 12,078.5 m were completed on a close spaced 50 m x 25 m pattern as part of the ongoing feasibility study. This included mostly RC drilling plus various size diamond core drilling of selected depth intervals in 21 of the holes to collect samples for metallurgical and geotechnical testing and to provide ore distribution data to help plan further depth testing of the mineralisation. The appraisal RC drillhole coverage was extended towards the north-east, into the historically worked current mining lease area enclosed within Havilah's MC 3566. Intersections of significance which were encountered included: 2.26% Cu + 2483 ppm Co over 27 m in hole MTDD113; 1.3% Cu + 1280 ppm Co over 24 m in hole MTRC115; and 2.1% Cu + 2246 ppm Co over 22.1 m in hole MTDD128. The top 30-40 m section of the mineralisation is oxidised to an iron oxide-quartz fragment gossan/ironstone with local malachite/atacamite/chrysocolla, which is underlain by a vuggy supergene pyrite(after pyrrhotite)-quartz dominant zone overlying the pyrrhotite dominant, primary sulphide mineralisation. The high grade primary sulphide milled breccia mineralisation is composed of pyrrhotite (60%)-quartz fragments (25%)-pyrite (5%) -chalcopyrite (5%) with local fragments of country rock and associated local green (sericite) altered feldspar ± gedrite ± biotite ± magnetite alteration. Preliminary metallurgical testwork was done on composited drill core samples of the oxidised and fresh mineralised rock material. Key findings were that: • the sulphides can be separately relatively easily from the quartz rich gangue. • the sulphide rich material should be suitable as feed stock for a roasting plant to produce sulphuric acid. • a high grade copper concentrate can be separated from the sulphide concentrate. • preliminary leach testing of the oxidised material has shown that only 40% of the copper is readily leachable. Further test work will be carried out to better identify the secondary copper minerals and to improve potential recoveries. A vegetation survey was conducted in October 2007 by Frank Badman of Badman Environmental. The survey covered the two MCs, 3565 and 3566, plus EL 3382 and parts of the adjoining EL 3448. Data from 20 sites identified 3 main vegetation groups. One threatened species, Acacia carneorum (Purple-wood wattle) was recorded at two sites away from the mine area. 16 introduced species were also recorded, 4 of which are proclaimed species under South Australian legislation. During licence Year 9, a total of 9 drillholes (MTRC226 - 228, and MTWB01 - 06) for 1341 m were completed as part of the ongoing feasibility study. This work comprised both inclined RC orebody appraisal/delineation drilling and vertical open hole rotary mud water bore drilling. The 3 RC holes were located on two of the southern drill traverses on MC 3565 to probe for deeper mineralisation that might extend down to 250 m vertical depth, and the 6 water bores were situated in this vicinity also. For the latter, air lift groundwater yields from the unconfined aquifer were calculated, a number of groundwater samples were collected and analysed, and water table depths were measured. During licence Year 10, Mutooroo Mines Pty Ltd, a new subsidiary of Havilah Resources, began operating the EL 3382 work programme. The only field work conducted was the completion of drill site rehabilitation commenced in the previous year, such that now only a few capped drill collars reserved for possible later re-entry remain unrehabilitated. Offsite - based studies included the following: • Detailed modelling of mineralised lodes and other geological domains. • Further metallurgical testwork including magnetic separation testwork. • A scoping study was completed on the options available for the roasting of Mutooroo sulphides, production of sulphuric acid and leaching and electrowinning of resultant calcines for copper and cobalt. Preliminary costings of a roaster, acid plant and associated infrastructure and power and water requirements were also determined. During licence Year 11, no new work with results worthy of reporting was done. Mutooroo Mines continued compiling data needed for the preparation of the joint venture's Mining Lease Proposal (MLP) and Mining and Rehabilitation Plan (MARP) documents. During licence Year 12, various components of the MLP/MARP compilation process continued in conjunction with Native Title negotiations. A baseline survey of local fauna habitats was performed in December 2011. During license Year 13, no new scientific data worth reporting was generated for the exploration licence. Work continued on the feasibility study, mine planning, Mining Lease Proposal compilation. Native title negotiations continued.