Bingham open pit mine

BINGHAM (EN: Bingham; RU: Бингем) is one of the largest within the world copper-porphyry deposits within the USA (Utah state). It is being developed since the 80-ies of the 19th century. During the 1904, there has been commissioned the "Bingham Canyon" copper ore open pit mine of the "Kennecoff Copper Corp." company.

There participate in the geological structure of the ore field the Upper Carboniferous quartzites and limestones, which are crumpled into the folds, and are broken by the faults of the north-eastern and north-western strike, and the stocks of the Upper Eocene granitoids, which are breaching the previously mentioned rocks. The molybdenum-copper mineralization is confined to one of them, namely, to the Bingham stock, which is formed mainly by the monzonite-porphyries. This stock has tubular shape and steep, almost vertical dip. Its dimensions in the horizontal plane are 1800x2700 metres.

The industrial concentration of copper and molybdenum is attracted to the places with increased crackedness and brecciation within the hydrothermally altered (silicified, K-feldspatized, and sericitized) monzonite-porphyries. The mineralization is represented by the small venules and interspersion of pyrite, chalcopyrite, and molybdenite, which are forming the stockwork, which is having the shape of the inverted bowl, inside of which is located the slightly mineralized core. The size of the projection of the stockwork onto the horizontal plane is 1200-1500 x 1800-2100 metres, the size along the vertical direction is more than 1000 metres, and the molybdenum mineralization in comparison with the copper one is slightly shifted downwards. The stockwork is mainly (75%) situated within the monzonite-porphyries, and to the lesser extent within the quartzites and limestones, which are enclosing the previously mentioned rocks. Within the deposit, up to the depth of 10-50 metres, there was developed the zone of the leaching, and up to the depth of 250-300 metres, there was developed the zone of the secondary sulfide beneficiation (cementation) with chalcocite. The zone of the primary ores extends to the depth of more than 1000 metres. Along the periphery of the Bingham stock, in the form of the semicircle, at the distance of up to 3 kilometres from its centre, within the quartzites and limestones, there is developed the zone of the "non-porphyric" polymetallic ores, which are forming the conformal depositions of the "shoulder coat" type, and the transverse vein-shaped bodies of different sizes. The main ore minerals are sphalerite, galena, and chalcopyrite; the impurities are pyrrhotite, bornite, covellite, chalcocite, and others.

The copper-porphyry deposit is unsealed by the trench with single entrance, three railway tunnels with the length of 1.1, 1.9 and 5.2 kilometres, and also by the automotive ramps. The system of development is with the transportation of the waste rocks, with the removal of the overburden rocks (112 million tonnes per year) into the external dumps for the waste rocks. The depth of the open pit mine is approximately 800 metres (the area is 730 hectares). The overburden rocks are transported by the railway transport. The railway transport serves 21 overburden stripping benches. The length of the railway tracks within the open pit mine is more than 160 kilometres. The ore from the stopes is delivered by the heavy load dump trucks to the places for the load transfer, and later by the railway (25 kilometres) to the "Arthur" and "Magna" beneficiation plants.

The rich ores of the cementation zone with 1.6-1.8% content of copper have been exhausted. There are being extracted the ores, which are containing 0.6-0.8% of copper and 0.025% of molybdenum. Since the start of the operation till the 1971, there have been removed from the open pit mine more than 4 billion tonnes of the rock mass, there have been extracted approximately 1.5 billion tonnes of the ore, from which there have been extracted 10 million tonnes of copper, 260 thousand tonnes of molybdenum, 350 tonnes of gold, 3000 tonnes of silver, and also the significant amount of rhenium (its content within the molybdenite is 360 grams per tonne) and platinoids. The reserves of the remaining part of the deposit are estimated at 1.5 billion tonnes of the ore (1978). By the underground method (the depth of the underground mines is up to 1.5 kilometres), by the end of the 70-ies, there have been extracted more than 400 million tonnes of the "non-porphyric" polymetallic ores, from which there have been obtained 375 thousand tonnes of copper, 1920 thousand tonnes of lead, 785 thousand tonnes of zinc, 55 tonnes of gold, and 3860 tonnes of silver.

The productive capacity of the open pit mine is approximately 30 million tonnes of ore per year; they extract from it 200-230 thousand tonnes of copper, and 5-6 thousand tonnes of molybdenum. The extraction of copper has decreased to 167-177 thousand tonnes (1977). There is prescribed by reconstruction the transition to the underground extraction. The total productive capacity of the beneficiation plants is approximately 100 thousand tonnes of the ore per day (1978). The beneficiation is performed by the flotation method. The extraction of copper into the concentrate is 92-93%, of molybdenum is 80%. There works the installation for the leaching of copper (approximately 13% of the extraction) from the dumps for the waste rocks of the open pit mine by the method of their irrigation with the sulfuric acid.