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Chemical processes at two artificial recharge sites in South Africa
Published in Peter J. Dillon, Management of Aquifer Recharge for Sustainability, 2002
A strong correlation between electrical conductivity and SO42− concentrations (R2 = 0.93) suggests that the dissolution of sulphate ions has caused the increased salinity. Gypsum is not a major component in the breccia and chloride concentrations have shown no marked increase, so evaporite dissolution is not likely to be responsible. The mineral assemblages of the breccia pipe, and particularly the sulphide minerals, are thermodynamically stable under the naturally reducing conditions below the water table. Dewatering the pipe and injecting treated, surface water has shifted the redox potential of the system, creating disequilibrium and promoting oxidation reactions in the subsurface. The results in Table 2 show that a large proportion of the recovered water is still non-potable natural groundwater that was not removed from the pipe. The decrease in pH and fluoride represent a minor improvement in water quality, but the oxidation of metal sulphides causes additional water quality problems that may hamper the successful operation of the scheme. Arsenic, for example, has been released from the sulphides, increasing the concentrations in solution.
A review of major rare earth element and yttrium deposits in China
Published in Australian Journal of Earth Sciences, 2022
Alkaline-carbonatite deposits vary from stockwork to vein types (e.g. Maoniuping in Sichuan Province), and breccia pipe-hosted and weathered deposits (e.g. Dalucao in western Sichuan Province), to disseminated mineralisation in a carbonatite–syenite complex (e.g. Lizhuang in Sichuan Province), and replacement stratabound mineralisation in carbonates (e.g. Bayan Obo, although this interpretation is still uncertain). The REY minerals in these deposits are niobite, pyrochlore, fergusonite, aeschynite, monazite, bastnäsite, parisite and chevkinite, which are disseminated in the host rocks and in veins, both in economic concentrations. The alkaline-carbonatite deposits have a similar paragenesis, with bastnäsite being the most important REY-bearing mineral, and gangue assemblages consist of calcite–barite–fluorite–quartz–celestite. Ore at Bayan Obo contains LREE–Fe–Nb, and that at Maoniuping contains LREE–F–Ba.
Geochemical characteristics of rehabilitated tailings and associated seepages at Kidston gold mine, Queensland, Australia
Published in International Journal of Mining, Reclamation and Environment, 2019
Mansour Edraki, Thomas Baumgartl, David Mulligan, Warwick Fegan, Ali Munawar
Kidston is a closed gold mine in the semi-arid sub-tropical region of northern Australia (Figure 1) with average annual rainfall of around 700 mm and fourfold higher pan evaporation. Gold mineralisation at Kidston was hosted by a breccia pipe with fragments of granodiorite, felsites, quartz-feldspar porphyry and local metamorphic [13]. Alluvial gold recoveries at Kidston began in the late nineteenth century and there were periods of small-scale hard rock mining in the first half of the twentieth century. However, the main large-scale open-pit mining operation at Kidston started in 1985 and finished in 2001. During this time, about 3.5 million ounces of gold was produced [14] through cyanide leaching, carbon in-pulp and carbon column technology followed by carbon stripping, electrowinning and smelting.
Vanadium as a critical material: economic geology with emphasis on market and the main deposit types
Published in Applied Earth Science, 2022
George J. Simandl, Suzanne Paradis
The spatial association between vanadium mineralisation and nonsulphide Pb-Zn deposits in combination with field observations, textures, and mineral paragenesis led to the conclusion that the vanadium mineralisation in the Otavi Mountainland was supergene in origin, a hypothesis supported by studies from Boni et al. (2007) and Kamona and Gunzel (2007). According to Bannister and Hey (1933) and Palache et al. (1951), the vanadate mineralisation of the Otavi Mountainland commonly consisted of mineral species belonging to the isomorphic series between descloizite [PbZn(VO4)(OH)] and mottramite [PbCu(VO4)(OH)] and to a lesser extent vanadinite [Pb5(XO4)3Cl], where X represents the elements P, As, and V (Figure 5(b); from Boni et al. 2007). Also in the Otavi Land area, the Abenab vanadium deposit, hosted by the carbonate rocks of the Maieberg Formation which belongs to the Tsumeb Supergroup, produced 1.85 million tonnes of ore averaging 1.03% V2O5 (Cairncross 1997). The deposit is described as a cylindrical breccia pipe consisting of descloizite and vanadinite cemented by calcite (Kamona and Gunzel 2007). Other examples of the vanadate-bearing deposits include Kabwe Mine (formerly known as ‘Broken Hill’), Zambia (Skerl 1934; Taylor 1954; Southwood et al. 2019) and Kihabe Zn–Pb–V prospect, Botswana (Mondillo et al. 2020). The Kabwe Mine and related processing plant operated from 1906 to 1994 and produced 0.8 million tonnes of Pb, 1.8 million tonnes of Zn with silver (79 tonnes), V2O5 (7820 tonnes), cadmium (235 tonnes) and copper (64 tonnes) as a byproduct (Kamona and Friedrich 2007). The Kabwe area in Zambia is currently considered as one of the most polluted sites in the world, due largely to wind dispersion of dust from extensive piles of slag (Baieta et al. 2021). Non-African examples are the St. Anthony mine in Arizona (644 tonnes of vanadium, 1934–44; Fischer 1975), and Los Lamentos and San Antonio mines in Mexico (211 tonnes of vanadium, 1938–40; Fischer 1975).