Press Release Archive - 2009

The San Enrique Monolito (SEM) porphyry copper prospect is located immediately adjacent to Anglo American’s Los Bronces mine, some 50km to the north-east of Santiago in central Chile. Exploration at SEM has been ongoing since 2005 and to date some 60,000m have been drilled. Due to its proximity to Los Bronces, the models of the mineralisation have been combined and some 1.2 billion tonnes (at an average grade of approximately 0.4%Cu) of the SEM mineralisation have already been reported as Mineral Resources that were published for Los Bronces in the 2008 Annual Report. These resources fell within the resources shell that was run to test for reasonable prospects of eventual economic extraction.

A recent preliminary scoping exercise for an underground block cave operation has indicated potential viability of the deeper parts of the SEM mineralisation. As such, there is an additional Inferred Mineral Resource of 900 million tonnes at a grade of 0.81% Cu and 0.02%Mo containing approximately 7.2 million tonnes of copper. The resource estimates are compliant with the Australasian Code for the Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code) and are constrained within the outlines of potential block caves. The SEM deposit is open laterally and vertically and shows increasing grade with depth.

The Chief Executive of Anglo American’s Base Metals business, Brian Beamish, said, "I am pleased to announce the additional resources at San Enrique Monolito, providing us with further significant and high quality development options around our world class Los Bronces mine in Chile."

Location, Geology and Sampling

At Los Bronces a copper-molybdenum bearing multi-phase porphyry stock and breccia complex is mined in the high mountains of central Chile, at an altitude between 3,400m and 4,100m. The south east extension to the Los Bronces mineralisation is known as San Enrique Monolito (SEM) located under the Monolito peak which is one kilometre from the current mining site.

The near surface geology is characterised by relatively small mineralised tourmaline breccia bodies encompassing a large, late stage weakly mineralised porphyry intrusive. With depth the mineralisation gives way to largely disseminated copper mineralisation hosted mainly in the San Francisco quartz monzonite and locally in inter-mineral porphyries and breccia bodies.

Whilst the near the surface hydrothermal breccias exhibit some secondary copper enrichment resulting in locally elevated copper grades, the deeper disseminated mineralised zone is characterised by chalcopyrite, pyrite with minor bornite sulphide mineralisation. The mineralisation shows a clear depth transition towards larger and richer copper and molybdenum concentrations. Mineralisation below the currently recognised deposit remains open and is a target for further exploration.

The mineralisation at SEM has been determined through drilling of some 60,000m reaching depths of approximately 1.5 km below surface. Two of the drill holes that demonstrate increasing grade with depth in parts of the deposit are: Mo-115 from 12 to 1,559m, 1,547m @ 0.73%Cu, 0.017%Mo (including from 895 to 1,559m, 664m @ 0.94%Cu, 0.029%Mo), and Mo- 116B from 410 to 1,561m, 1,151m @ 0.83%Cu, 0.034%Mo (including from 1,145 to 1,445m, 300m @ 1.2%Cu, 0.035%Mo). Some 28,000m of drilling in 56 holes supports the area below the current resources shell. Data gathering and quality control has been carried out to the same high standards as those applied at the Los Bronces mine.

Mineral Resource Estimation

Based on the drilling information, lithology, alteration and mineralisation models were developed on cross sections and plans and used as a basis for grade interpolation into blocks using ordinary kriging. Validation of the block grade estimates was carried out visually on plan and on section by comparing them with the sample grades and no obvious errors were noted. In addition, average grades of samples and blocks compare well within the various units used in the resource estimation.

The current block model below the current resources shell indicates that the SEM body of mineralisation (exploration target) could contain between 2.5 and 3.5 billion tonnes at grades of between 0.65%Cu and 0.75%Cu at a cut-off of 0.5%Cu.

As part of the strategic planning for the Los Bronces district, preliminary scoping studies have been carried out to mine part of this mineralisation by underground block caving. This exercise indicates that an underground block cave operation is viable and therefore the mineralisation contained therein passes the test for reasonable prospects for eventual economic extraction and may be quoted as a Mineral Resource.

Therefore, at SEM there is an additional Inferred Mineral Resource of 900 million tonnes at a grade of 0.81%Cu and 0.02%Mo containing approximately 7.2 million tonnes of copper. The resource estimates are compliant with the Australasian Code for the Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code) and are constrained within the outlines of potential block caves.

The mineralisation remains open both laterally and vertically and 56,000m of drilling has been proposed for 2010 with the purpose of increasing the Mineral Resources and improving the classification.

Competent Person Statement

The information in this press release that relates to Resources is based on information compiled by Sergio Godoy, who is a member of the Australasian Institute of Mining and Metallurgy. Mr. Godoy is a full-time employee of Anglo American Chile and has experience which is relevant to the style of mineralisation and type of deposit under consideration and is qualified as a Competent Person as defined in the 2004 Edition of the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves. Sergio Godoy consents to the inclusion in this press release of the matters based on his information in the form and context in which it appears.

This mineralisation is defined as Resources under the JORC Code and therefore is considered to have a reasonable prospect of being economically extracted in the foreseeable future. Estimates of such mineralisation are based largely on geological information with only preliminary consideration of mining, economic and other factors and are not yet classified as Proved or Probable Reserves. While in the judgment of the Competent Person there are reasonable expectations that all or part of the Resources will eventually become Proved or Probable Reserves, there is no guarantee that this will occur as the result depends on further technical and economic studies and prevailing economic conditions in the future.