ROBERTSON RANGE PROJECT - IRON ORE AND MANGANESE
The Robertson Range Project lies 100 - 120km east-northeast of Newman in the East Pilbara of Western Australia. The project comprises three Exploration Licences (E45/3394, E45/3395 and E46/818) covering an area of some 800km2. The two major tenements E45/3395 and E46/818 were recently granted in December 2009.
The tenements adjoin those of FerrAus Ltd and Atlas Iron Ltd where recent exploration has indicated a resource base of some 200Mt of high grade hematite iron ore. In addition, E46/818 lies some 25km SSW along strike from the recently commissioned Nicholas Downs (previously Balfour Downs) major high grade manganese mine estimated to contain a resource exceeding 15Mt.
EXPLORATION LICENCE E45/3395 - IRON ORE
This exploration licence contains two main target areas – outcropping hematite/goethite mineralisation at the Jim Jim hills and potential CID iron ore targets in the north eastern sector. The Jim Jim Hills form a series of low hills and ridges that in several cases are obscured by alluvial and sand dune cover. Reconnaissance rock chip sampling by Legacy, produced very encouraging high grade iron ore assays to 55.7% Fe (Figures 1 and 2).
Figure 1: E45/3395 Satellite Imagery Iron Ore Targets at the Jim Jim Hills and Rock Chip Sample Results
Figure 2: Jim Jim Hills Outcropping hematite rich mineralisation
In the north-eastern sector of the tenement, airborne magnetic data shows the presence of a series of roughly linear magnetic anomalies in the north east sector of the tenement (Figure 3).
Figure 3: Aeromagnetics image of E45/3395 showing magnetic anomalies potentially representing CID mineralisation
These were considered to be potentially extensive channel iron deposits overlain by Quaternary alluvial and dune cover. The magnetic features extend for at least 7km along strike and, if CIDs would likely extend much further to the southwest, the potential source area.
Reconnaissance air core drilling program conducted during 2010 over part of the aeromagnetic features successfully intersected alluvial channels containing strongly ferruginous pisolitic and nodular material of presently unknown provenance. The channels, where intersected by fence drilling, were typically up to 200m wide. The iron rich zones showed a vertical (true) thickness of up to 5m, but on average from 1 - 3m. Assays of up to 42.2% Fe were obtained, with most samples being in the assay range of 25 - 35%. Beneficiation studies are planned to determine the commercial significance of this mineralisation.
EXPLORATION LICENCE E46/818 - MANGANESE
Field mapping has shown that most of the extensive 370km2 tenement is underlain by Balfour Formation manganiferous shales, masked in part by surprisingly thin alluvial cover (Figure 4). The shales are host rocks to the major Nicholas Downs manganese mine located some 25km along strike to the NNE. The Nicholas Downs deposit, previously known as the Balfour Downs deposit, is being developed by a joint venture comprising Hancock Prospecting and PMI (Mineral Resources Ltd). Mining has recently commenced of this high grade manganese orebody, with the first shipment achieved in December 2010. The deposit has an inferred JORC resource of approximately 20Mt, with a targeted production of 540,000 tonnes per annum of 38% manganese ore.
Field work has identified several areas of strongly manganiferous shales, typically lying under thin alluvial wash. At the Narmana prospect, manganese mineralisation occurs over several low hills near a contact with Enacheddong Dolomite represented locally by banded cherts (Figure 5) This association bears similarities with manganese deposits located further to the north within the Manganese Subgroup e.g. Woodie Woodie.
Figure 4: Manganiferous shales of the Balfour Formation, host to manganese mineralisation in the district
Very little exploration is recorded on the tenement probably driven by the presence of masking thin alluvial deposits, and a historic exploration model relying on weathering and supergene enrichment to produce viable manganese deposits on topographic highs. Recent work, e.g. in the Woodie Woodie area to the north, has shown that manganese mineralisation may result from hydrothermal fluids moving and precipitating along fault and fracture systems.
Given the high prospectivity of the ground, and the large shallow alluvial cover, the company is planning to conduct a heliborne EM survey designed to detect substantial manganese mineralisation below cover and to depth. This will be followed up with RC drilling of significant conductors.
Figure 5: Narmana Prospect – large low hill with outcropping manganiferous shales and cherts – prime exploration sequence
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Web page updated on 1 March 2011.