ore reserves and mineral resources 2011 report - Anglo American ...
ore reserves and mineral resources 2011 report - Anglo American ...
ore reserves and mineral resources 2011 report - Anglo American ...
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General<br />
Cut-off grade Merensky Reef <strong>and</strong> UG2 Reef<br />
Amplats takes cognisance of cut-off grades (derived from information on pay limits at the mining operations) <strong>and</strong> of ‘reasonable <strong>and</strong> realistic prospects for<br />
eventual economic extraction’ over a period of 30 to 50 years. The delineation of the Resources that meet the requirements of reasonable expectation of<br />
eventual economic extraction has been defined using the modifying factors as defined in the SAMREC Code. These include, but are not limited to,<br />
mineability, geological complexity, processability <strong>and</strong> economic factors relevant to Amplats. The minimum Resource grades per reef <strong>and</strong> per operation are<br />
in all instances greater than the Cost 4 pay limit.<br />
Resource Cut<br />
Merensky <strong>and</strong> UG2 Reef: The Mineral Resources are estimated over a practical minimum mining width suitable for the deposit known as the ‘Resource<br />
Cut’. The minimum mining width over which Mineral Resources are declared is 90 cm. The ‘Resource Cut’ width takes cognisance of the mining method<br />
<strong>and</strong> geotechnical aspects in the hanging wall or footwall of the reef.<br />
Merensky Reef<br />
The Merensky Mineral Resource tonnage decreased by 1.6% to 1,005.4 Mt (2010: 1,022.2 Mt) <strong>and</strong> the 4E ounce content decreased by 3.8% to<br />
173.0 Moz (2010: 179.8 Moz) mainly as a result of the following:<br />
As per the statement above, previously <strong>report</strong>ed Mineral Resources in areas where the virgin rock temperature is expected to be above 75° Celsius have<br />
been reclassified to Mineral Deposit. This applies mainly to Tumela Mine: -26.6 Mt -6.7 Moz.<br />
Previously <strong>report</strong>ed Mineral Resources of Wesizwe (for 2010 – 26.6% attributable interest) are not <strong>report</strong>ed anym<strong>ore</strong>, see comments on previous page<br />
under “Joint ventures”: - 12.0 Mt -2.4 Moz.<br />
These decreases were in part offset by the increase in Mineral Resources owing to Thembelani Mine: reallocation of Ore Reserves back to Mineral<br />
Resources owing to economic assumptions: +13.8 Mt +3.1 Moz.<br />
UG2 Reef<br />
The UG2 Mineral Resource tonnage decreased by 4.8% to 1,608.2 Mt (2010: 1,689.9 Mt) <strong>and</strong> the 4E ounce content decreased by 9.0% to 271.2 Moz<br />
(2010: 298.1 Moz) mainly as a result of the following:<br />
As per the statement above, previously <strong>report</strong>ed Mineral Resources in areas where the virgin rock temperature is expected to be above 75° Celsius have<br />
been reclassified to Mineral Deposit. This applies to Tumela Mine, Twickenham Platinum Mine <strong>and</strong> Ga-Phasha Project: -101.9 Mt -19.4 Moz.<br />
Previously <strong>report</strong>ed Mineral Resources of Wesizwe are not <strong>report</strong>ed anym<strong>ore</strong>; see comments on previous page: -15.0 Mt -2.2 Moz.<br />
Additional Mineral Resources were converted to Ore Reserves resulting in a decrease of the Mineral Resources at:<br />
– Thembelani <strong>and</strong> Siphumelele mines: -27.1 Mt -4.5 Moz.<br />
– Union Mine: -12.3 Mt -2.1 Moz.<br />
– Twickenham Platinum Mine: 9.1 Mt -1.8 Moz.<br />
The decrease in tonnage is offset by the increase of Mineral Resource from Der Brochen where a change in mining method (from conventional to<br />
mechanised mining) resulted in an increase of the Resource Cut: +81.0 Mt +2.8 Moz.<br />
Securing<br />
our future<br />
Platreef<br />
MSZ<br />
Tailings<br />
The 1.0 g/t 4E cut-off grade that has been used is unchanged from previous <strong>report</strong>ing.<br />
The Mineral Resource tonnage increased by 28% to 2,785.4 Mt (2010: 2,170.5 Mt) <strong>and</strong> the 4E ounce content increased by 38% to 195.0 Moz (2010:<br />
141.6 Moz). The principal reason is as follows:<br />
Additional b<strong>ore</strong>hole information for Mogalakwena North has confirmed the presence of the Platreef at higher elevation in localised areas to the west <strong>and</strong><br />
below the original pit shell. Until a better underst<strong>and</strong>ing of this structure has been determined, an Inferred classification <strong>and</strong> a 100 m swathe of geological<br />
loss have been applied to these elevated <strong>resources</strong>. Conceptual pit shell evaluations have indicated that the existing pit could extend to the west <strong>and</strong><br />
deeper to exploit these Resources. Consequently, the Mineral Resource <strong>report</strong>ing depth has increased by approximately 200 m to 650 m below surface<br />
elevation (equivalent to 400 m a.m.s.l.). Owing to this increase in <strong>report</strong>ing depth the Mineral Resources exclusive of Reserves increased substantially by<br />
+784.4 Mt + 71.0 Moz. Pit design test work has confirmed that these Resources are potentially open pitable.<br />
The increase in tonnage is offset by the increase of Mineral Resources mainly from the following:<br />
Additional conversion of Mineral Resources to Ore Reserves for Mogalakwena South: -123.6 Mt -13.9 Moz. See notes under Mogalakwena Ore Reserves.<br />
S<strong>and</strong>sloot, where previously <strong>report</strong>ed Mineral Resources are excluded as the limit of surface mining has been reached: -34.6 Mt - 3.2 Moz.<br />
It must be noted that no Mineral Resources applicable to underground mining have been included in the Mineral Resource statement.<br />
The Resource statement includes stockpiled material from the opencast operation that consists of calcsilicate <strong>and</strong> oxidised material with a cut-off of 3 g/t.<br />
That material is currently not part of the business plan.<br />
The Main Sulphide Zone is the <strong>ore</strong> body mined at Unki Platinum Mine. As of 2010, Amplats owns an effective 100% interest in Southridge Limited.<br />
Currently only the Unki Platinum Mine Ore Reserves <strong>and</strong> Mineral Resources have been <strong>report</strong>ed in the relevant Ore Reserve <strong>and</strong> Mineral Resource statement.<br />
During <strong>2011</strong>, a new Resource evaluation was completed covering Unki South, Helvetia <strong>and</strong> Paarl projects (contained within the special mining lease held<br />
by Southridge Limited), however, an independent external review of these Mineral Resources is outst<strong>and</strong>ing <strong>and</strong> will only be completed during the first<br />
quarter of 2012: For this annual <strong>report</strong> the Mineral Resources <strong>report</strong>ed restate the 2010 Unki East <strong>and</strong> West mines’ Resources.<br />
The Mineral Resource tonnage exclusive of Ore Reserves increased by 2.4% to 79.5 Mt (2010: 77.6 Mt) <strong>and</strong> the 4E ounce content increased by 2.3% to<br />
10.5 Moz (2010: 10.3 Moz) owing to some conversion of previously <strong>report</strong>ed Ore Reserves back to Mineral Resources. It must be noted that oxidised<br />
material is not included in the Mineral Resource statement.<br />
Operating tailings dams cannot be geologically assessed <strong>and</strong> theref<strong>ore</strong> are not <strong>report</strong>ed as part of the Mineral Resources. At Rustenburg mines a dormant<br />
dam has been evaluated <strong>and</strong> the tailing forms part of the Mineral Resource statement.<br />
During 2010, the tailings dams at Union Mine were reactivated <strong>and</strong> their Resources were removed from the Mineral Resource statement. However, for<br />
<strong>2011</strong> some of the Union tailings were deactivated <strong>and</strong>, as a consequence, now form part of the Mineral Resource statement.<br />
A dormant tailings dam at Am<strong>and</strong>elbult is currently being drilled <strong>and</strong> its Resources will be evaluated in 2012. Tailings dam Resources are <strong>report</strong>ed<br />
separately as Mineral Resources <strong>and</strong> are not aggregated to the global Mineral Resource.<br />
ANGLO AMERICAN PLATINUM LIMITED <strong>2011</strong><br />
21