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Juras S.,Eldorado Gold Corporation
8th International Mining Geology Conference 2011, Proceedings | Year: 2011

The terms measured resources and proven reserves denote the highest level of estimation confidence in all of the major classification schemes. But what do they really bring to today's project or mine with respect to production planning and expectations? Initial reserve declaration does not need measured resources, just indicated resources. Economic viability of a project is assessed on total reserves with nary a bonus for the amount of proven reserves. Production plans are based on grade and tonnage goals that may only coincidently correspond to proven reserves. So are the measured and proven categories still relevant? Historically, and almost exclusively in underground mines, companies only allowed mining in areas of proven reserves. Some companies still follow that philosophy. But many others will mine a mixture of probable and proven reserves without hesitation. Also what of the undeveloped project in a new district - what is to be made of their declared measured resources and proven reserves? Measured resources are commonly set either by some type of proximity to data scheme or a matter of 'feel' based on the qualified person's experience. The parameters for reserve conversion focus on the project as a whole and then a portion becomes classified as proven reserves almost solely based on whether the resource category is measured. So should the mining industry continue to use these categories of resource and reserve classification? This paper will present arguments about making these categories once again more relevant. A more disciplined usage of these categories may re-introduce their relevancy in public disclosures of resources and reserves. As well a more consistent usage in operations may lead to increased confidence in managing production targets and costs.

Chan T.,Fort Technologies | Collins M.,Fort Technologies | Dennett J.,Fort Technologies | Stiksma J.,Fort Technologies | And 3 more authors.
Canadian Metallurgical Quarterly | Year: 2015

A pilot plant campaign has been conducted by Sherritt Technologies in support of Eldorado Gold Corporation's evaluation of pressure oxidation (POX) technology for the treatment of refractory gold concentrates from the Certej deposit in Romania. Preliminary batch tests indicated that gold extraction from the oxidised concentrates in subsequent cyanide leaching was adversely affected by the presence of organic carbon in the POX feed when chloride in solution was at an elevated level. As such, the process conditions tested were selected to either counteract the negative impact of the organic carbon, or to deactivate it during POX. Both routes proved feasible, yielding gold extraction of 95-98% in cyanide leaching of the oxidised concentrates. Silver extraction was typically in the range of 80-90%, provided that the oxidised concentrates were also processed in a lime boil step before cyanide leaching. © 2015 Canadian Institute of Mining, Metallurgy and Petroleum.

Reid A.,Geological Survey of Western Australia | Smith R.N.,Tasman Resources Ltd | Baker T.,Eldorado Gold Corporation | Jagodzinski E.A.,Geological Survey of Western Australia | And 3 more authors.
Economic Geology | Year: 2013

The Vulcan prospect is a newly discovered Cu-Au prospect located within the eastern Gawler craton, South Australia. The prospect is entirely subsurface and defined by a geophysical anomaly intersected by diamond drilling. Eight drill holes have all intersected hematite-rich alteration and Cu-Au mineralization within a variety of breccia types ranging from those composed entirely of hydrothermal hematite + sericite + chlorite to those dominated by altered rock in which clasts of protolith rock are preserved. The highest-grade zones of mineralization at Vulcan occur within hematite-dominant breccias. Molybdenite within hematite-rich brecciated granite samples has been dated via the Re-Os method and yields a crystallization age of 1586 ± 8 Ma (including decay constant uncertainties). SHRIMP zircon U-Pb analyses show that a sample of hematitesericite- chlorite-altered and brecciated granite was emplaced at 1743 ± 7 Ma. The new data from Vulcan confirm that hematite breccia-related Cu-Au mineralization formed during a widespread alteration and mineralization event between ca. 1600 and 1570 Ma, broadly coeval with the voluminous felsic large igneous province of the Gawler Range Volcanics/Hiltaba Suite, and are consistent with most interpretations of the geology of the Olympic Cu-Au province. © 2013 Society of Economic Geologists, Inc.

Deschenes G.,CanmetMINING | Guo H.,Eldorado Gold Corporation | Xia C.,CanmetMINING | Pratt A.,CanmetMINING | And 3 more authors.
Minerals | Year: 2012

The high solubility of copper sulphide minerals is an issue in the cyanidation of gold ores. The objective of this study was to quantify the effect of individual copper sulphide minerals on the Hunt process, which showed advantages over cyanidation. High purity djurleite, bornite and chalcopyrite, with a P70 of 70–74 microns, were mixed with fine quartz and gold powder (3–8 micron) to obtain a copper concentration of 0.3%. The ammonia-cyanide leaching of slurry with djurleite proved to be more effective than cyanidation; producing comparable extraction of gold (99%), while reducing the cyanide consumption from 5.8 to 1.2 kg/t NaCN. Lead nitrate improved the Hunt leaching. The lower cyanide consumption is associated to a significant reduction of copper dissolved. XPS surface analysis of djurleite showed that lead nitrate favored the formation of Cu(OH)2 species. Lead was also detected on the surface (oxide or hydroxide). Sulphide and copper compounds (cyanide and sulphide) were reaction products responsible for inhibiting the dissolution of gold. Lead nitrate added in the Hunt leaching of bornite produced 99% gold extraction. Surface reaction products were similar to djurleite. The cyanide consumption (~4.4 kg/t NaCN) was not reduced by the addition of ammonia. Cyanidation of chalcopyrite showed a lower consumption of cyanide 0.33 kg/t NaCN compared to 0.21 kg/t NaCN for Hunt. No significant interferences were observed in gold leaching with a slurry containing chalcopyrite. © 2012 by the authors; licensee MDPI, Basel, Switzerland.

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