Witwatersrand

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Witwatersrand

(wĭtwô`tərzrănd') [Afrik.,=white water ridge] or

the Rand,

region, Gauteng prov. (formerly a part of TransvaalTransvaal
, former province, NE South Africa. With the new constitution of 1994, it was divided into Eastern Transvaal (now Mpumalanga), Northern Transvaal (now Limpopo), Pretoria-Witwatersrand-Veereeniging (now Gauteng), and part of North West prov.
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), South Africa. The area, which forms the watershed between the Vaal and Olifants rivers, is c.25 mi (40 km) wide and extends more than 60 mi (100 km) from west to east in a series of parallel ranges 5,000 to 6,000 ft (1,520–1,830 m) above sea level. Major cities of the Rand are JohannesburgJohannesburg
, city, now part and seat of City of Johannesburg metropolitan municipality, Gauteng prov., NE South Africa, on the southern slopes of the Witwatersrand at an altitude of 5,750 ft (1,753 m).
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, BenoniBenoni
, city, Gauteng prov., NE South Africa, on the Witwatersrand, now administratively part of the Ekurhuleni metropolitan municipality. It is the distribution center for a gold-mining district and is part of a large industrial complex known for its iron and steel plants.
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, BoksburgBoksburg
, city, now part of Ekurhuleni metropolitan municipality, Gauteng prov., NE South Africa. It is an important coal-mining center. Some gold mining is still carried on.
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, SpringsSprings,
city, now part of Ekurhuleni metropolitan municipality, Gauteng prov., NE South Africa. It is an industrial center of the Witwatersrand, a gold- and uranium-mining region.
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, and GermistonGermiston
, city, now part and seat of Ekurhuleni metropolitan municipality, Gauteng prov., NE South Africa, on the Witwatersrand. The chief industries are gold mining and processing and the manufacture of liquid oxygen; other chemicals, machinery, textiles, and clothing are
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.

The Rand is one of the world's richest gold-mining regions. The gold occurs in reefs, or thin bands, that are mined at depths of up to 10,000 ft (3,050 m). Development of the Rand dates from the 1880s. Although many of the older mines are now nearly exhausted, the Rand still produces most of South Africa's gold and much of the total world output. Silver and iridium are recovered as gold-refining byproducts, and the region also has coal mines. The Rand also has such industries as engineering, steel milling, metallurgy, machine building, diamond cutting, food processing, and the manufacture of chemicals, cement, furniture, and clothing.

Witwatersrand

 

(also the Rand), the world’s largest deposit of gold ores, which also contain uranium. The Witwatersrand is located on the territory of the Republic of South Africa, in the south of Transvaal Province. It is a mountain ridge, 150-300 m high, on the High Veld Plateau; it forms the divide between the Limpopo and Vaal rivers. The ore-bearing area stretches from Johannesburg to the south-west for 350 km (ranging from 25 to 100 km in width). The deposit was discovered in 1884. From the beginning of exploitation through 1967, about 21,000 tons of gold were mined. In 1965, the output was about 900 tons (about two-thirds of the total output in the capitalist world). The gold content is 8-20 g per ton of merchantable ore. The gold reserves have been estimated at tens of thousands of tons. In addition to gold, the Witwatersrand ores contain from 0.019 to 0.038 percent and rarely 0.1 percent uranium. The uranium reserves in such low-grade ores have been estimated at 300,000 tons. There are deep mines here, reaching a depth of 3,700 m, and the temperature in the mines is 50°-52° C.

Within the ore-bearing area, three stages of rock have developed: the lower, composed of Archean gneisses and crystalline schists; a middle level of folded shales, quartzites, conglomerates, and igneous rock from the Witwatersrand, Ventersdorp, and Transvaal systems of the late Precambrian; and an upper level composed of gently sloping continental deposits from the Upper Paleozoic. The ore bodies consist of bands of Witwatersrandian conglomerates separated by interlayers of barren quartzite. The conglomerates form the so-called reefs, with the industrial varieties of them being called bankets. The thickness of the individual bands of conglomerates is from 2-3 cm to 3 m, and the length is dozens of km to a depth of 3-4 km. The ore-bearing conglomerates are composed of light-colored quartz gravel, cemented together by fine-grained quartz, chlorite, carbonate, carbonaceous matter, and sulfides, predominantly pyrite. Minerals that have been found in the detrital fraction in the cement include chromite, zircon, spinel, garnet, rutile, diamond, apatite, monazite, and aggregates of osmiridium and platinum. The gold is divided into primary gold, which is found in a finely dispersed form in the sulfides, and secondary gold, which runs through the gravel and its mineral cement in thread vein-lets. The uranium minerals are represented by thucholite, uranite, and brannerite.

The problem of the genesis of the Witwatersrand is still debated. Some geologists view this deposit as an ancient delta placer that was later metamorphosed, while others see it as a deposit of hydrothermal origin.

On the basis of the development of gold mining and other ore-extracting sectors, the Witwatersrand has become the chief industrial center of the nation, producing about two-fifths of the output of industry.

REFERENCES

Uran v drevnikh konglomeratakh. Moscow, 1963.
Smirnov, V. I. Geologiia poleznykh iskopaemykh, 2nd ed. Moscow, 1969.

V. I. SMIRNOV

Witwatersrand

a rocky ridge in NE South Africa: contains the richest gold deposits in the world, also coal and manganese; chief industrial centre is Johannesburg. Height: 1500--1800 m (5000--6000 ft.)