Comparison of Ore Reserve Grades with Mill Head Grades Using Statistics in Two Gold Mines, Sudbury District, Ontario

Abstract The Orostar and Scadding were two small gold mines owned and operated by Orofino Resources Limited. Conventional statistical treatment indicates an identical arithmetic mean grade of 0.22 oz/T Au for both mineable reserves. Further, the deposits are both shown to have cut weighted average reserve grade of 0.21 oz/T. Orostar mined out at 0.206 oz/T and Scadding at 0.156 oz/T Au. The combined exploration and development database contained 1394 fire assays, more than enough for statistical confidence in a normal distribution. Therefore this study was initiated to determine, if possible, why the mill head grades were lower than the averages and to experiment with several methods to determine whether a reliable statistical mill head grade estimation method would emerge. Despite the identical reserve grades, distinct differences in the grade distribution histograms are present. By studying the arithmetic and log-normal grade distributions, with some attention to South African practices, this paper reports on those differences which may account for the considerable divergence in the mill head grades. Furthermore, this study casts considerable doubt on the industry standard method of cut weighted averages.
The global mill head grades of the two deposits have been derived from the arithmetic average grades by graphic means. This precise method of mill head grade prediction, if applied to complex orebodies, could permit selective grade control and result in direct cost savings by allowing the operator to detect false value stopes, benches or levels and emphasize reliable regions of not only gold mines, but also uranium or base metal deposits.
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Summary: A well-defined approach is essential to ensure the long-term success of a regional exploration program. Teck's approach in eastern Canada is designed to fulfill corporate objectives while recognizing certain unique parameters for exploration in the area. The elements of this approach include clearly defined objectives, technical considerations and personnel policies, all of which are equally important. The goal is a significant discovery before the mid-1990s and the company is confident that...
Publication: Exploration & Mining Geology
Author(s): BARRY D. SIMMONS
Issue: 3
Volume: 1
Year: 1992
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Summary: Perhaps the single most significant variable in the evaluation of a mining project is the reserve estimate. Many parameters are considered when estimating reserves, among them geology. This paper examines the link between the quality of a reserve estimate and a good understanding of the geological controls for the deposit. A clear understanding of the geometry is essential to the accurate definition of the shape and size of the deposit. This includes the definition of any structural controls...
Publication: Exploration & Mining Geology
Author(s): CHRIS M. HEALEY
Issue: 3
Volume: 1
Year: 1992
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Summary: Detailed sampling using a portable diamond drill, and interlaboratory comparison of selected samples have been combined with statistical studies of truncated populations to establish the gold content of several outcrops in the Val d'Or area. The outcrops chosen are non-mineralized. The background gold concentration in the rocks of the region is 5 ppb or less. Gold is distributed relatively homogeneously within the outcrops studied except for slightly increased concentrations within quartz-tou...
Publication: Exploration & Mining Geology
Author(s): TYSON BIRKETT, FRANCOIS ROBERT, DAN RICHARDSON, STEVE GREEN
Issue: 3
Volume: 1
Year: 1992
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Summary: The rare-earth elements (REE) form a significant part of the group of so-called "high-technology" metals whose glamour has attracted both the scientific community and the mining industry. Despite this attraction, world production of REE declined abruptly in 1985 and only recently has begun to approach production levels of 1984. The decline in 1985 was primarily due to decreased demand for light REE used as catalysts in the production of lead-bearing gasoline. Incorporated within the current...
Publication: Exploration & Mining Geology
Author(s): W.D. SINCLAIR, J.L. JAMBOR, T.C. BIRKETT
Issue: 3
Volume: 1
Year: 1992
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Summary: The Orion gold mine, located 7 km northeast of the town of Malartic, Quebec, was discovered in mid-1985. Underground exploration was undertaken in 1986 leading to commercial production in 1988. The upper part of the orebody was exploited above the 125 m level and a total of 131 090 t at an average grade of 5.31 g/t gold were extracted.
This paper describes the authors' current knowledge and interpretation of the geology, gold distribution, and structure of the Orion No. 8 ore zone deposit....
Publication: Exploration & Mining Geology
Author(s): YVON TRUDEAU, DENIS RAYMOND SOQUEM
Issue: 3
Volume: 1
Year: 1992
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Summary: The Kipawa yttrium-zirconium prospect is located about 150 km south of Noranda, , Quebec. Yttrium-zirconium mineralization occurs in an elongate, regionally metamorphosed and deformed peralkaline complex in the Grenville terrain. The mineralized zone, as defined by >0.10% Y2O3, is 1300 m long and 10 m to 30 m wide. Zirconium content typically ranges from 0.50 to 1.20% ZrO2. The mineralized zone strikes northwest and dips 20 degrees to 35 degrees to the southwest. It occurs at the structural...
Publication: Exploration & Mining Geology
Author(s): JAMES F. ALLAN
Issue: 3
Volume: 1
Year: 1992
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Summary: Since the 1957 initiation of deposition of mill tailings at the Heath Steele mine, New Brunswick, periodic detailed studies of the tailings geochemistry and mineralogy have been conducted, thereby providing a unique opportunity to examine the geochemical evolution of a sulfide-rich mine-tailings impoundment. When deposited, the tailings contained about 85 wt sulfide minerals, 1 wt to 3 wt carbonate minerals, and 12 wt to 14 wt aluminosilicate minerals. Mineralogi-cal examination of samples of...
Publication: Exploration & Mining Geology
Author(s): D.W. BLOWES, J.L. JAMBOR, B.C. APPLEYARD
Issue: 3
Volume: 1
Year: 1992
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Summary: Biotite from aplite that appears to have crystallized simultaneously with disseminated Cu-Mo mineralization at MacLeod Lake in northern Quebec yields K-Ar dates in the range 2032 ± 44 Ma to 2097 ± 47 Ma. The mean value, 2065 Ma, is some 400 Ma younger than the 2485 ± 64 Ma date obtained from a hornblende concentrate separated from a granodiorite sill that is spatially, but apparently not genetically, associated with the disseminated Cu-Mo deposit. The mean biotite date of 2065 Ma at MacLeod...
Publication: Exploration & Mining Geology
Author(s): J.F. DAVIES, G.J. PRIOR
Issue: 3
Volume: 1
Year: 1992
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