Name: Argyle mine.

Location: Argyle is located in the remote East Kimberley region of Western Australia.

Holding and Controlling Company: Argyle is wholly owned by Rio Tinto.

Brief Description: Argyle is one of the world's largest suppliers of diamonds and the world's largest supplier of natural coloured diamonds. It is the world's primary source of rare pink diamonds – the company's signature stone.

Brief History: The Argyle deposit was discovered in 1979 by the Ashton joint venture, following 12 years of exploration by various companies in the area. The mine has been operating since 1983.

Products: Diamonds.

Geology/Mineralisation: The Kimberley craton comprises a central core of a thick series of nearly flat-lying sedimentary and volcanic rocks that were deposited between 1.9-billion and 1.6-billion years ago. These rocks form the Kimberley plateau. They are underlain by a basement of crystalline igneous and metamorphic rocks, which are not exposed on the surface of the plateau. Recent investigations have indicated that the basement is of Archean age – more than 2.5-billion years old. This central Archean craton is bounded along its south-eastern margin by the Halls Creek Mobile Zone or the East Kimberleys, and along its south-western margin by the King Leopold Mobile Zone or West Kimberleys.

Diamondiferous kimberlites have been found on the central Archean craton, whereas diamondiferous lamproites have been found in or near the associated mobile zones. This came as a great surprise to geologists at the time, because apart from alluvial deposits, significant quantities of diamonds were known only to occur in kimberlites located on Archean cratons. The diamondiferous rocks of both types occur as volcanic dikes, pipes, and crater deposits, which are typical modes of emplacement for kimberlite and lamproite magmas.

Reserves: Total proven and probable reserves as at December 31, 2016, were estimated at 29-million tonnes grading at 2.3 ct/t.

Resources: Total mineral resources as at December 31, 2016, were estimated at 15-million tonnes grading at 3.2 ct/t.

Mining Method: The Argyle diamond deposit located in the AK1 pipe was mined using conventional alluvial and openpit mining from 1983 to 2013. In 2013, a new era of underground mining of the AK1 pit to access the pipe at further depth got under way.

Block cave mining techniques – where the orebody is undercut, allowing it to break up and ‘cave’ under its own weight – are now being employed to extend the life of the Argyle mine until at least 2020. The block cave is expected to generate on average 20 million carats per year.

Major Infrastructure and Equipment: The Argyle underground mine is a challenge in size and complexity. There are about 40 km of tunnels. The main thoroughfares in the underground network comprise two tunnels to carry vehicles, one for ventilation and one for moving ore. There are two large underground crushers and conveyor belts that transport the ore from deep in the mine to the surface.

When Argyle was first established, it became apparent that purpose-designed processing machinery would be needed to recover and sort the high volume of characteristically small stones produced by the mine. This included the development of sophisticated X-ray sorting technology to assist in the efficient identification and collection of small diamonds.

Today, the Argyle processing plant is one of the most efficient in the world. It is capable of processing up to 11-million tonnes of ore a year.

Prospects: During 2016, mineral resources mineral resources excluding ore reserves, decreased from 44-million tonnes to 15-million tonnes. Previously reported mineral resources included mineralisation that could support a potential extension of the currently planned mine life. As mine life extension options are under ongoing review, the reported mineral resources have now been restricted to those parts of the mineralisation that can potentially be developed, mined and processed during the existing mine-life defined by the current underground operation, which sees production continuing until 2021. As a result, there has been a material reduction in reported mineral resources.

As the change to Argyle’s mineral resources does not impact on reported ore reserves, this reduction has no bearing on the current mine plan.

Contact: Argyle Diamond Mine.

Contact Details:
Argyle Diamond Mine
Tel + 61 8 9168 4900
Email enquiries.argylediamondmine@riotinto.com
Website http://www.riotinto.com