ore reserves and mineral resources 2011 report - Anglo American ...

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SECURING OUR FUTURE ORE RESERVES AND MINERAL RESOURCES Exploration on prospecting permits awarded in 2007 is progressing in line with the work-programme schedules and the environmental management programmes submitted to the Government’s Department of Mineral Resources. Most of these programmes are in the fifth year of the five-year completion time frame and a three-year extension will be sought on several of the prospects. Foreign exploration continued in 2011, with the ongoing objective of finding and defining projects of value to the Group. This included projects in Brazil and Zimbabwe, with watching briefs in a number of other promising geological provinces. Options to dispose of the Company’s interests in Russia are being investigated. Greenfield exploration in Brazil is ongoing, with the investigation of a number of promising platinum prospects. Extensive exploration continues on the Great Dyke in Zimbabwe in order to obtain information on Mineral Resources, specifically in support of the mine extraction strategy for the Unki Project. MINERAL RESOURCES No changes in terms of the basic principles relating to determining Mineral Resource estimates were implemented during 2011. The Mineral Resource evaluation and classification are reviewed and signed off by a team of competent persons. Changes to further align the minimum Mineral Resource widths with changes in stopesupport methodology and mining equipment are envisaged for 2012. Over the past two years exploration drilling results on the Platreef have indicated a localised down-dip shallowing of the dip of the orebody in the northern part of Mogalakwena. A conceptual pit design has demonstrated that these Resources lying below the current pit shell are economically viable to extract via an expanded opencast operation. This has justified the extension of the reporting depth from 450 m to 650 m below surface and results in an increase of 71 million 4E ounces of Mineral Resources exclusive of Ore Reserves. A significant proportion of these additional Resources is classified as Inferred and additional drilling in 2012 is planned to confirm structural and mineralisation continuity. Investigations conducted in 2011 to determine maximum mining depths related to virgin rock temperatures have been concluded. A virgin rock temperature of 75° Celsius is currently considered to be the limit to mining given anticipated technology, metal prices and energy costs. Altogether 26.1 million 4E ounces of the affected portions of the Inferred Mineral Resources within the mining rights of Tumela Mine, Twickenham Platinum Mine and Ga-Phasha Project are therefore reclassified as Mineral Deposit within the Amplats portfolio. Amplats will review these deposits with changing geological information, mining technology and metal prices. As part of its ongoing management process, the Mineral Resource Management (MRM) Department at Amplats has developed the Basic Resource Equation to establish a consistent and auditable 6 ANGLO AMERICAN PLATINUM LIMITED 2011
process for tracking and reconciling movements in Mineral Resources and Mineral Inventories. This equation encompasses processes from all the MRM disciplines, in order to ensure that the publication of Mineral Resource and Ore Reserve data is aligned with the Company’s business plan, and with technical and economic considerations. CONVERTING MINERAL RESOURCES TO ORE RESERVES The process of defining the Ore Reserves from the Mineral Resource has undergone further refinement and has been reviewed and approved within Anglo American. It adheres to approved Amplats policy and procedures encompassing the following: Merensky and UG2 underground operations Only current operations, approved projects in execution and projects in feasibility study included in the business plan are included as Reserves. Appropriate mine design and layouts are applied to the Resource areas as dictated by current mining methods to derive a Mineable Resource. Note: the Mineable Resource excludes material contained in regional or bracket pillars that comprise part of the overall mine design. The Mineable Resource is scheduled according to the relevant mine’s production requirements to develop a Scheduled Resource. The application of modifying (technical; mining; geotechnical; processing and recovery; legal; market; and social/governmental) factors is implemented in three distinct phases: – Mine design and scheduling. Modifying factors that have an impact on dilution of the Resource (ie stope width vs Resource width, tertiary development and other waste mining done on the reef horizon, etc) and modifying factors that define mining losses (ie non-mineable pillars and RIH/RIF mining inefficiencies, etc) are applied to the criteria included in establishing the mine design and scheduling. – Processing. Those modifying factors that influence the efficiency of processing and recovery are applied to the Scheduled Resource. The result is a Mineable Reserve. – The economic phase. The subsequent application of modifying factors that influence the economic aspects of the mining operation results in a portion of the scheduled Resource not being converted into Reserve (ie in the “uneconomic tail”). This uneconomic tail reverts to Mineral Resources, to be considered in subsequent planning processes. Its exclusion results in a Scheduled Reserve that is equivalent to the operation’s business plan (life-of-mine). The Scheduled Reserves are peer-reviewed and signed off by the competent person(s). Securing our future ANGLO AMERICAN PLATINUM LIMITED 2011 7
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