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Toronto, Canada

Merriman J.D.,University of Missouri | Whittington A.G.,University of Missouri | Hofmeister A.M.,Washington University in St. Louis | Nabelek P.I.,University of Missouri | Benn K.,Kinross Gold Corporation
Precambrian Research

The thermal structure of Archean terranes depends in part on the thermal transport properties of their distinctive rock types. We determined thermal diffusivity (D) of a suite of 14 greenstone, mafic granulite and tonalite-trondhjemite-granodiorite (TTG) rocks at temperatures up to 1000°C at atmospheric pressure using laser flash analysis, which lacks systematic errors associated with conventional contact techniques. At room temperature, D ranges from ~3.8mm2s-1 for banded iron formation to ~0.8mm2s-1 for a quartz-poor trondjhemite. For all samples thermal diffusivity decreases with increasing temperature, such that D for the suite converges around ~0.7±0.1mm2s-1 at ~700°C. Combining these results with measured density and heat capacity calculated from modal mineralogy provides thermal conductivity as a function of temperature for each rock suite. Whereas near-surface thermal conductivity varies from 2.7 to 4.2Wm-1K-1 depending on rock type, thermal conductivity of the lower crust is ~2Wm-1K-1 and only weakly dependent on lithology, which is more thermally resistive than the uppermost mantle (~3.5Wm-1K-1).Use of temperature-dependent thermal transport properties in numerical models reveals that surface geotherms can be relatively insensitive to crustal heat production, because high heat-producing TTG rocks typically have high thermal diffusivity and conductivity at low temperatures and, consequently, are more efficient conductors of the heat they produce. This finding implies that calculations of crustal heat production from surface borehole measurements may entail significant uncertainties. © 2013 Elsevier B.V. Source

Roos C.J.,Kinross Gold Corporation | Conrad P.W.,Montana Tech of the University of Montana | Rosenthal S.D.,Newmont Mining
Mining Engineering

Ground-engaging tools are used to prevent damage to the main components of earth-moving equipment. These tools consist of everything from shovel teeth to replaceable drill bits to dozer wear plates. The costs of these "consumable" items are increasing with the costs of raw materials. This project developed a tool to be used by Newmont Mining Corp. to predict the consumption of excavator teeth at a particular mine site. This paper presents the results of the Montana Tech research project in which an equation was developed to predict excavator teeth consumption based on production rates and rock properties. Source

Deschenes G.,Natural Resources Canada | Fulton M.,Natural Resources Canada | Rajala J.,Kinross Gold Corporation | Guo H.,Wardrop Engineering Inc.
Minerals and Metallurgical Processing

In an earlier study (Deschênes et al, 2009), gold and silver were shown to be efficiently extracted from samples taken from the Kupol Mine in Russia using lead nitrate in a cyanide leach system. In the current study, a comparison of the technical and economic merits of a new technology called CANMET enhanced leaching process (CELP) was made with the cyanidation/ acidification-volatilization-recycling (AVR) process using eight metallurgical variability samples, as well as a large composite sample, which was to represent the initial two years of Kupol mill feed. The composite sample leach feed assayed 33.4 g/tAu and 289 g/tAg. The metallurgical results from the large composite sample demonstrated that CELP produced very similar gold and slightly higher silver leach extractions compared to the conventional cyanidation/AVR leach conditions at 1/2 the cyanide concentration (1,000 ppm NaCN in CELP vs. 2,000 ppm for cyanidation/AVR leach conditions). It was estimated that the total cost per ton was approximately the same for the two technologies (total cost of CELP with the use of Merrill-Crowe at $46.48/t, with cyanidation/AVR at $46.13/t). However, the implementation of CELP would eliminate a capital expenditure of approximately $5 million for an AVR system based on a 2005 feasibility level cost estimate. Eight variability samples used to confirm the composite sample results showed that, on average, the gold leach extractions with CELP and the conventional leach conditions were very similar, but the average silver leach extraction was 2.1% higher for CELP. Furthermore, CELP silver leach extraction was 4.6% higher on average compared to conventional cyanidation for the four mid-grade variability samples evaluated. The decision was made to remove AVR cyanide recovery from the flowsheet and implement CELP at Kupol. The ability to use the conventional leach equipment with CELP and simplify the flowsheet was also a factor, given the remote location of the Kupol Mine. Copyright 2010, Society for Mining, Metallurgy, and Exploration, Inc. Source

Colangelo D.,Kinross Gold Corporation
AACE International Transactions

This article will attempt to discuss the important items to consider when presenting an estimate to a client. Those that have never presented to clients, or perhaps find it challenging to do so will hopefully find value in this article. When presenting an estimate, one may wish to consider the following; preparing an agenda, preparing printed handouts which may include various estimate summaries, use of visual aids, and preservation of backup documents. The single item which is undoubtedly the most important is the basis of estimate document, it is simply not possible to present any estimate without this document. The importance of historical references, benchmarks and a full internal review of the estimate are also critical elements that should not be overlooked. Regardless of the class of estimate and level of detail being presented, the overall fundamentals in documenting the estimating process in a clear, concise manner still apply. Presenting a well-documented estimate is an essential part in delivering a successful project. Source

Mulcahy S.R.,University of California at Berkeley | Roeske S.M.,University of California at Davis | McClelland W.C.,University of Iowa | Ellis J.R.,Kinross Gold Corporation | And 5 more authors.

The Famatina margin records an orogenic cycle of convergence, metamorphism, magmatism, and extension related to the accretion of the allochthonous Precordillera terrane. New structural, petrologic, and geochronologic data from the Loma de Las Chacras region demonstrate two distinct episodes of lower crustal migmatization. The first event preserves a counterclockwise pressure-temperature path in kyanite-K-feldspar pelitic migmatites that resulted in lower crustal migmatization via muscovite dehydration melting at ∼12 kbar and 868°C at 461 ±1.7 Ma. The shape of the pressure temperature path and timing of metamorphism are similar to those of regional midcrustal granulites and suggest pervasive Ordovician migmatization throughout the Famatina margin. One-dimensional thermal modeling coupled with regional isotopic data suggests Ordovician melts remained at temperatures above their solidus for 20-30 Ma following peak granulite facies metamorphism, throughout a time period marked by regional oblique convergence. The onset of synconvergent extension occurred only after regional migmatites cooled beneath their solidus and was synchronous with the cessation of Precordillera terrane accretion at ∼436 Ma. The second migmatite event was regionally localized and occurred at ∼700°C and 12 kbar between 411 and 407 Ma via vapor saturated melting of muscovite. Migmatization was synchronous with extension, exhumation, and strike-slip deformation that likely resulted from a change in the plate boundary configuration related to the convergence and collision of the Chilenia terrane. ©2013. American Geophysical Union. All Rights Reserved. Source

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