Bor (copper ore region)

The cross-section of the Bor deposit

BOR (SR: Bor; RU: Бор) is the copper ore region within Yugoslavia. It is located within Serbia, at the distance of 200 kilometres to the south-east of Belgrade, within the limits of the eponymous metallogenic zone.

It has been discovered during the end of the 19th century, and is being developed since the 1902 by the opencast and underground methods. The mineralization (of the Upper Cretaceous - Miocene age) is confined to the complex of the Upper Cretaceous andesites, dacites, and porphyrites; this mineralization has been traced along the length of up to 3 kilometres, with the width of up to 1 kilometre. There have been identified within the ore field several deposits: the Bor proper, Brezanik, X and B. The Bor deposit includes depositions of massive sulfidic ores, which are formed by pyrite, covellite, chalcocite, bornite, chalcopyrite, enargite. Certain minerals, especially enargite, are enriched with selenium and germanium, and there is characteristic the presence of gold (up to 4 grams per tonne), silver (up to 10 grams per tonne), and platinum. Pyrite within certain places is enriched with nickel (approximately 1%). The depositions of the massive ores are often surrounded by the zones of the venulous-interspersed mineralization, sometimes of considerable sizes. The transition from the massive ores to the venulous-interspersed ores is gradual. The area of such stockworks in horizontal cross section is up to 10 thousand square metres, and vertical thickness is 150-200 metres.

During the end of the 1970-ies, at 400-450 metres deeper than the known ore bodies, there has been unsealed by boreholes the large deposition of the copper-porphyric ores, which is confined to the apophyses of diorites. Its thickness exceeds 500 metres, the lower boundary has not been identified (see the Figure).

The main ore minerals are chalcopyrite and pyrite, but, with the increase of the depth, also molybdenite. In subordinate quantity, there also exist magnetite, enargite and bornite, sometimes also chalcocite and covellite. During the 1978, on the southern edge of the open pit mine, there has been unsealed the copper ore deposition of stratiform type (the "Novo Okno" ore body). The flatly-embedded ore-bearing horizon, with the thickness of more than 20 metres, represents by itself the mineralized volcanic breccia. The mineral associations are the same, as within the massive ores, the country rocks are almost not changed, the texture of the ores is typical for the volcanogenic-sedimentary deposits. The reserves of the Bor deposit are approximately 100 million tonnes of ore, or more than 0.8 million tonnes of copper (in terms of the metal, which is being extracted), the reserves of the ore field are up to 2.6 million tonnes of copper (1980). The mineralization at the deposit has been traced to the depth of 1300 metres. The deposit is operated by the "Rudarsko Topionicarski Basen Bor" governmental enterprise. The annual extraction of the ore is approximately 5 million tonnes, including 3-3.5 million tonnes within the open pit mine. The ore, which has been extracted, is processed at the beneficiation plant by direct selective flotation, with the obtainment of concentrates of copper (21-23% of Cu), with the extraction of 84-85%, and with the obtainment of pyritic concentrate (300-400 thousand tonnes per year). Copper concentrates are processed at the plant within the Bor city (has been built during the 1922), where are the main produce of which electrolytic copper, gold, silver, selenium, sulfuric acid, germanium, rhenium, vanadium, and so on. Near the Bor deposit, within the same metallogenic zone, there are situated the Majdanpek (is operated by opencast method since the 1961) and Veliki Krivel (is operated since the 1980) deposits of copper.