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Merensky Reef The application of modifying factors to the Merensky Reef and UG2 Chromitite Layer, Bushveld Complex Ken Lomberg SAMREC Working Group CRIRSCO Annual Meeting: Modifying Factors Workshop Ulaanbaatar, Mongolia 18 October 2014 Mineral Reserve Estimation Requirements • Reliable • Ore quantity and quality • In order to: • Make sound investment decisions • Successfully manage and operate a mine Aim of paper • Technical aspects or parameters • Conversion of mineral resource Merensky Reef • Special reference to UG2 Chromitite Layer - Merensky Reef and - UG2 Chromitite Layer Breast Mining Method Bushveld Complex Project Existing Mines m 8 000 - Magnetite layers Gabbro UPPER Olivine diorite 7 000 - ZONE Anorthosite 6 000 - Pyroxenite Marker 5 000 - metres 8000 Bushveld m above and Magnetite UPPER Gabbro Olivine diorite below the LG6 Layers ZONE Complex Anorthosite Merensky Reef 1 189 4 000 - Gabbro StratigraphyMAIN Anorthosite UPPER 776 UG2 ZONE Norite GROUP 656 UG1 6000 Pyroxenite Pyroxenite3 000 Marker - 407 MG4 5000 Gabbro MAIN Anorthosite ZONE Norite 357 Merensky Reef Pyroxenite MG3 MIDDLE Upper Group Anorthosite UPPER CRITICAL GROUP Chromitites Norite ZONE 156 MG2 3000 2 000 - Pyroxenite Middle Group Chromitites 122 MG1 Merensky Reef Pyroxenite Upper Group Lower Group Anorthosite UPPER CRITICAL NoriteLOWER CRITICAL Harzburgite Chromitites Chromitites 2000 ZONE Pyroxenite ZONE Dunite Middle Group Chromitites1 000 - 20 LG7 Lower Group LOWER CRITICAL Pyroxenite Chromitites Harzburgite ZONE Dunite Pyroxenite LOWER LOWER GROUP 0 LG6 & LG6A 1000 Harzburgite ZONE Dunite 15 LG5 Pyroxenite 0 - LOWER ZONE Harzburgite Dunite MARGINAL ZONE Norite 0 MARGINAL ZONE Chromitite Anorthosite Norite Pyroxenite Modifying factors • Legal/ Tenement • Environmental and Social • Geological Knowledge • Type of mineralisation/ Grade distribution • Mine design • Metallurgy • Infrastructure • Revenue • Costs Aspects of Viability • Commodity Marketing • Environmental requirements • Mineral Tenement • Legal framework • Social and Labour plans • Government / Politics Approach to Reserve estimation Important aspects to consider What to avoid Application of specialist x Application of a procedure (Black Box knowledge Approach) Understanding of each parameter applied to a mineral resource Removes uncertainties Merensky Reef Histograms Figure 1 Schematic Grade Histgrams of the Merensky Reef 1m 1m Feldspathic Pyroxenite Feldspathic reef Pyroxenite Pegmatoidal Feldspathic Pyroxenite reef Merensky Merensky Chromitite Cr Mottled Anorthosite FW1a Mottled AnorthositeFW1a 0 Merensky FW1b Leuconorite FW1b FW2 1m Leuconorite PGE 1m Concentration FW2 PGE Concentration 1m Merensky Reef at Western Platinum Mine, Western Bushveld Feldspathic Pyroxenite reef Cr Pegmatoidal Feldspathic Pyroxenite Merensky FW2 PGE Concentration Leuconorite 1m Photograph Source: Dept of Geological Sciences, University of Cape Town Mining Cut – UG2 Chromitite Layer • Grade concentrated in chromitite • Interstitial pyroxenites - low grade • Footwall mineralised • Grade histogram • Ability to undermine the leaders • Nature of upper and lower contacts UG2 Chromitite Layer Histograms Figure 1 Schematic Grade Histograms of the UG2 Chromitite Layer UG2 Chromite Layer, with PGE mineralisation grade profile, Western Olivine bearing Pyroxenite/ Platinum Mine, Western Bushveld Feldspathic Harzburgite Pyroxenite Leaders 100 cm Chromitite Main Chromitite Chromitite Layer 0 cm Pegmatoidal Feldspathic Grade Pyroxenite Source: Dept of Geological Sciences, University of Cape Town Normal UG2 Chromitite Normal UG2 Chromitite Bifurcated UG2 Bifurcated UG2 Layer with footwall Layer Chromitite Layer Chromitite Layer Mineralization Histograms examples courtesy of Anglo Platinum Corporation Limited Geological Losses • No Reef present • Reef Undeveloped • Not a realistic chance of extraction e.g. base of a pothole Mining losses Result of implementation of a mine design • In stope pillars • Clamping pillars • Regional Pillars • Inefficient mining due to geology • Underbreak due to mining practice • Falls of Ground Marginal Cut-offs • Are all reefs payable? • Tailings grade 0.5 – 0.7g/t • Stope width/Grade relationship Metallurgical Typically excluded for Bushveld • Nature of testwork • Applicability of process • Concentrator/ Smelter/Refiner? • Toll Treatment • Penalties due to excessive chrome • Base metal analytical technique Mine Design - Conventional October Modifying Factors 18 2014 Conventional Mine Design • Planned Dilution • Minimum stope width • Account for all on reef excavations • Unplanned dilution • Overbreak • Falls of Ground • Cross tramming • Skills eg rock drill operators • Maximum Mining Depth • Legislative requirements e.g. ventilation Mine Design Mechanised Mechanised Mining • Minimum excavation dimensions • How low is low profile? • Slipping for infrastructure e.g. belts • Waste and Reef handling • Suitability of mining fleet Mine Design - Open Pit Mining Open Pit • Highwall slope • Stripping ratios • Suitability of Mining Fleet • Potential for optimisation • Ability to mine potholes • Metallurgical recovery Infrastructure • Water • Permit • Allocation • Power • Availability • Cost of getting to site • Transport • Rail • Road • Port 24 PGE Proportions • Basket Price • Ratios of metals and volatility of price Base Metals and Minor PGEs • Influence of base metals e.g. Ni • Type of Ni and Cu Assay • Potential for influence of other metals e.g. Ru Grade Control • New Projects may be grade sensitive • Feasibility includes systems and staff appropriate to grade Feasibility • Mining method and mine design • Mining equipment, staffing levels, operational protocols etc. • Social and Labour Plan • Environmental • Capital and operating costs • Processing methodology (recovery) • A reconciliation of mine to mill production • A reconciliation mine production to mineral resource/mineral reserve estimates Conclusions • UG2 Chromitite Layer and Merensky Reef are unique ore bodies • Specialist treatment by Competent Person • Lower grade material in HW and FW • Re-estimate the mineral resource • Apply the selected mine design Declaration of the mineral reserve Legal Mineral Tenement Social Mineral Reserve Environmental Mine Geology Design and Mining Engineering Scheduling Infrastructure Metallurgical Economic The application of modifying factors to the Merensky Reef and UG2 Chromitite Layer, Bushveld Complex Ken Lomberg SAMREC Working Group CRIRSCO Annual Meeting: Modifying Factors Workshop Ulaanbaatar, Mongolia 18 October 2014 .
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