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The Oaks |
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Limpopo (Northern) Province, South Africa |
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Diamonds
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Oaks kimberlite and mine is located in the Potgietersrus/Mokopane District, ~15 km southeast of Swartwater and 350 km due north of Johannesburg in the Limpopo Province of South Africa. It is developed on kimberlites within the Marnitz Kimberlite cluster (#Location: 22° 57' 16"S, 28° 19' 4"E).
The Oaks kimberlite was discovered by De Beers in 1986. Three kimberlite occurrences are known, all of which are Group I type and are intrusive into quartzo-feldspathic and amphibolitic gneisses of the Limpopo Mobile Belt/Province. The Oaks is a kimberlite pipe with a surface area of approximately 1 ha. It has both hypabyssal and diatreme facies. The Mooikloof kimberlite is a pipe of 2.5 ha, composed exclusively of hypabyssal facies with a very low diamond content, while the Dartmouth body is a barren dyke.
The Oaks Kimberlite has been dated (Phillips et al., 1999) at 509 Ma (Rb-Sr model age) and 503 ±6.2 Ma (40Ar/39Ar). It occurs as two separate and geologically distinct lobes that are separated by a neck consisting of a mixture of country-rock breccias and kimberlite. The distinctly different geology of the two lobes is reflected in the diamond population, with higher grades and higher values being mined from the North lobe compared to the South lobe.
A feasibility study was initiated in 1997 and production officially commenced in January 1999. The estimated mine life was only 8 years to a final pit depth of 200 m.
The total estimated resource in 2000 was 2.6 Mt @ 53.8 cpht (carats per hundred tonnes) for 1.4 million carats of diamonds. Production in the same year was 0.212 Mt @ 54.7 cpht for 0.116 million carats of diamonds at an average value of USD 165 per carat.
The mine treated 250 000 tonnes of ore in 2005 and recovered 85 766 carats at an average grade of 34 cpht (Damarupurshad, 2006) after having produced 290 000 tonnes in 2004 to recover 68 943 carats at a grade of 23.8 cpht; and 312 000 tonnes in 2003 for 100 123 carats at a grade of 32.1 cpht (South African Diamond Handbook, 2005).
All mining activities ceased in 2008, after a total of ~2.4 Mt of kimberlite ore had been extracted and treated (Botham et al., 2011).
The most recent source geological information used to prepare this decription was dated: 2004.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
The Oaks
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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