Tropicana Gold Project, Australia

The Tropicana gold project is located in Western Australia on the edge of the Great Victoria Desert, approximately 330km east-north-east of Kalgoorlie.

Discovered in 2005, the project includes over 13,000km² of tenements extending over 300km of the historic contact zone between the Yilgarn Craton and the Albany Fraser provinces.

The project is a joint venture between AngloGold Ashanti Australia (70%) and the Independence Group (30%). It is expected to produce up to 430,000oz of gold annually over its life time of 15 years.

The mine will be developed at an estimated cost of A$500m to A$540m.

The project was approved by the Environmental Protection Authority (EPA) in July 2010.

A feasibility study initiated in July 2009 is in progress for completion in the last quarter of 2010. A decision on mining operations will depend on the results of the study. Mining is expected to begin in 2013.

Reserves

The mine holds an estimated 45mt of proved and probable reserves that are graded at 2.3g/t. The measured, indicated and inferred mineral resources have been estimated at 75.3mt grading at 2.07g/t.

Geology

The Tropicana deposit is geologically different from other Archaean-aged, greenstone-hosted gold deposits found in the Yilgarn Craton. The Yilgarn Craton was formed following a period of intense tectonic and magmatic activity.

It is dominated by granitic igneous, volcanic and gneiss metamorphic rocks, significant faults and intrusive basic dykes. The area is regionally characterised by the extreme weathering that resulted in the formation of a 100m thick regolith.

Towards the west, the deposit is dominated by Archaean and Proterozoic aged granitic, volcanic and metamorphic rocks of the Yilgarn Craton. Younger sedimentary deposits that unconformably lie over the Archaean and Proterozoic rocks dominate the geology of the deposit towards the east.

A north-south trough hosts the deposits that also include alluvial, lacustrine and Aeolian deposits. These deposits, ranging in thickness between 600m and 4,300m, have been formed due to rock erosion and weathering, and stages of marine incursion.

The deposit is comparatively featureless and extends over a strike length of 4km. The three main physiographic units of the deposit include sediment dominant zones, ferruginous and siliceous duricrusts, weathered bedrock and colluvial materials.

The sediment dominant zones are characterised by Aeolian sands that form extensive areas of plains and longitudinal dunes that are on an average 10m in height and between 1.5km and 5km in length. The width of the east-west oriented dunes ranges between 100m and 200m. The interdune areas are between 250m and 800m wide.

Due to their symmetrical shape and presence of well developed vegetation, the dunes and sand plains are considered to be relatively stable and mature. Between 1961 and 1970, the dunes exhibited no significant movement or modifications, confirming the maturity of the landscape.

The sediment dominant zones also host fluvial silts, halite deposits, and marine silts and clays that correspond to the existing and palaeo drainage systems.

Regional zones of rock exposure are observed across the project area, typically along the ridge surface and low breakaway features. These zones of exposure have developed due to physical and chemical weathering of the less strong kaolinitic areas.

Mineralisation

Mineralisation is found within Archaean aged high grade quartzofeldspathic gneiss rocks that are associated with late biotite and pyrite alteration. It occurs as one or two laterally extensive planar lenses with a moderate dip.

Mineralisation is up to 63m thick and has been drilled to a down-dip length of 600m. It remains open at depth.

Mining and processing

The deposit will be mined using open pit methods including a traditional drill and blast, truck and excavator operation. The proposed open pit will be 6km in length, 1.5km in width and up to 400m in depth.

Ore processing will be carried out at a rate of 6mtpa. It will involve a comminution circuit including two-phase crushing, high-pressure grinding rolls and ball milling together with a standard CIL circuit.