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Jwaneng |
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Botswana |
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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 Jwaneng diamond mine, is located approximately 170 km south west of Gaborone in the south-central part of Botswana.
Detailed exploration by De Beers in the 1960s, found a number of diamondiferous kimberlites, including Orapa and Letlhakane. Jwaneng, also discovered during this campaign, commenced operation in 1981-2.
Jwaneng, is said to be the world s richest diamond mine and produced 14.3 million carats of diamonds in 2003. At current mining rates the open pit alone is expected to continue production until 2029. In 2002 Jwaneng recovered 13.035 million carats of diamonds from 9.3 Mt of ore at a recovered grade of 124.7 cpht. Some 36.6 Mt of waste were also stripped. In 2000 the average value of stones recovered was USD 108 per carat. Reserves + resources in 2000 totalled 288 Mt @ 143.5 cpht diamonds (=413 million carats).
The Jwaneng diamond mine is based on three pipes, which coalesce near the current land surface to form a single body with a surface expression of 52 ha. Together, these three pipes form the largest of the kimberlites discovered in the area. These pipes are part of a larger cluster of 11 kimberlites that were emplaced at about 235 ±4Ma on the NW rim of the Kaapvaal block.
The kimberlites intruded shales of the Transvaal Supergroup during a period of active erosion of the sandstones and conglomerates of the Waterberg Group. All three pipes exhibit a steep sided shape, although, unlike more typical kimberlites, the Jwaneng pipes are filled with crater facies material to a depth of 600 m. No in situ diatreme or hypabyssal facies kimberlite has been exposed to date. The dominant infill in all three Jwaneng pipes consists of reworked volcaniclastic kimberlite and do not contain any evidence to suggest they were post-eruptive depositional centres with crater lakes as at Orapa and Mwadui. Each pipe has a distinct geology and diamond grade signature, the broad features of which are briefly summarised below.
The North Pipe comprises a central core of primary pyroclastic kimberlite, surrounded by a peripheral zone of pale brown to brown volcaniclastic material which have been interpreted as representing reworked volcaniclastic debris from the tuff rings.
The Central Pipe is filled with brownish green to grey (when fresh) massive to well-bedded, graded deposits, predominantly representing reworked volcaniclastics, although the characteristic pyroclastics seen in the North Pipe are absent.
The South Pipe has a very similar structure and appearance to the Central Pipe, but is characterised by more internal variation and more distinct internal facies than that pipe.
For detail consult the reference(s) listed below.
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.
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Richardson S H, Shirey S B and Harris J W 2004 - Episodic diamond genesis at Jwaneng, Botswana, and implications for Kaapvaal craton evolution: in Lithos v77 pp 143-154
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Stachel, T., Viljoen, K.,S., McDade, P. and Harris, J.W., 2004 - Diamondiferous lithospheric roots along the western margin of the Kalahari Craton - the peridotitic inclusion suite in diamonds from Orapa and Jwaneng: in Contrib. to Mineralogy & Petrology v.147, pp. 32-47.
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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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