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By Batric Pesic

Gold dissolution with bromine was studied by using the rotating disc technique. Geobram TM 3400 was used as a source of bromine. The parameters studied were: rotating speed, Geobrom 3400 concentration, pH, temperature, sulfuric and hydrochloric acid concentration, and the concentration of various cations (copper, iron, zinc, aluminum, manganese, potassium and sodium) and anions (chloride, bromide, sulfate, nitrate, and iodide) According to the Levich plot and activation energy, gold dissolution was controlled by a chemical reaction rate. Copper, iron, and manganese in their highest oxidation states, aluminum, zinc, sodium and potassium did not have any effect on gold dissolution rate. The presence of manganous ion dramatically decreased the gold dissolution rate. Kinetic performance of bromine, in the form of Geobram TM 3400, was compared with performance of cyanide and thiourea.

Jan 1, 1990

Basic premises for evaluating special characteristics of gold-bearing porphyry metal systems stem from their contrasts with properties of the class as a whole. Included features are differences in geologic, thus tectonic, environments, subtle but real differences in the proportions of accessory metals Mo-Ag-Au that are regionally and within some regions, tempo-rally distinct, contrasts in the Ag:Au ratios, petrological-geo-chemical as well as isotopic differences between intrusive suites, the age and nature of host terranes, contrasts in alter-ation style, and zoning variations of mineralogical and physical properties of rocks. These properties are linked in various ways in different regions and suggest that in large gold-bearing systems where gold may be uniformly distributed, environ-ments of emplacement, and compositions or sources of igneous "progenitors" may dominate in importance over processes, and that systems in which gold is zoned are processes-dominant.

Jan 1, 1990

By M. Stefanakis, M. Errington, A. Kontopoulos, J. M. Prevosteau, K. Adam

The Olympias arsenical pyrite concentrate assaying 25 g/t Au, 40% S, 40% Fe and 12% As is highly refractory in nature; an oxidation pretreatment step is required to liberate gold and render it amenable to cyanidation. In the present study mineralogical analysis techniques including Image Analysis, SEM, EPMA, SIMS, Mossbauer, ICP/MS, etc., have been employed in order to investigate the mode of gold occurrence within the Olympias pyrites. Bacterial oxidation was used as a case pretreatment route and bacterially leached products were examined under SEM. The mineralogical observations and the relevant metallurgical and cyanidation test data were combined to establish a correlation between the mineralogical characteristics of the raw and oxidised products and conditions prevailing over the oxidative pretreatment step and the gold liberation achieved.

Jan 1, 1990

By Thomas P. Meloy

As the importance of particle shape in mineral processing is increasingly recognized as an major variable in predicting the behavior of both individual particles and particle systems, whether it be in dense media, froth flotation, comminution or the flow of particles, new method of shape characterization are being developed, particularly for use on image analyzers. These shape characterization methods may be broadly classified into the analytical, empirical and physical formation methods. Discussed are approaches and the strengths and weakness of each of these methods. Moreover old and new shape measuring techniques are reviewed, particularly the new image analysis methods techniques such as Fourier, Haar, Fractal, Walsh and Delta as well as a variety of other techniques such as tabling, the Cascadograph, settling and L/D ratios. Also discussed are the problems of doing shape research, current progress and the future of the field.

Jan 1, 1990

By Till M, McGee WA

The Hermit Islands are situated at 145¦ E 1 30'S in the Bismarck Sea approximately 200km WNW of Manus Island. They are dominated by basalt flows, one of which yielded a K/Ar isotopic date of 3.4 + 0.05Ma. All basalts examined were olivine-bearing, but one sample also contained hornblende. Although many outcrops were weathered, no evidence of pervasive hydrothermal alteration was observed on any islands and non-weathered rocks are petrographically fresh and many retain glass.

Jan 1, 1990

By Milner SC

Four quartz latite rheoignimbrite units (units I to IV) mapped in the Goboboseb Mountains have been traced to their eruptive source, the Messum intrusive complex; this is a complex multistage ring structure (18 km diameter) with well defined gabbroic, monzonitic, and syenitic intrusive phases, and a central ring zone containing mixed rhyolitic to latitic agglomerates. Three of the four quartz latite units are correlated with the upper and lower (2 units) Springbok quartz latites outcropping some 90-130 km north of McIsum. This implies minimum volumes of 300-500 km for wits I and III (Lower Springbok) and 2200-2600 km for unit IV (Upper Springbok). This latter unit is still ti 300 m thick at its outcrop limit, some 130 km from Messum. Each of the four units represents single cooling units. Lithologically, each can be divided into three zones: A basal, dark grey to black flinty or glassy zone, often with highly attenuated fiamme (ressembling flow banding); a central massive and strongly recrystallised zone; and an upper variable zone which exhibit breccias, contorted flow banding, and amygdaloidal to pumiceous clasts. Their overall characteristics tend to be intermediate between ash flows and lava flows. The rheoignimbrites are interpreted as the oproducts of dense, high temperature (950¦-1100 C) ash flows which underwent rheomorphism and lava-like flow prior to their final cooling.These large scale eruptions are related to the initial rifting of Africa and S. America, possiby in response to a major hot spot.

Jan 1, 1990

By C. W. Armbrust

At FHC Gold Company's Paradise Peak Mine gold and silver are produced. Precious metals recovery rates are very satisfactory along with the recovery and production of a relative high volume of mercury. At Paradise Peak precious metals are recovered via the Merrill-Crowe process and delivered to the refinery area as a mercury-bearing precipitate cake. The recovery of mercury is then obtained through a vacuum retort system. The balance of the material is mixed with fluxes and then melted and cast into dore' bars for shipping. Issues of retort capacity and concerns over efficiency led to research into the retort process itself.

Jan 1, 1990

By Windsor C. R, Thompson A, Bywater S

A new high tensile strength, steel cable, that may be grouted into boreholes has been developed for use as rode reinforcement. The manufacturing technique produces a birdcage pattern in which the cross section varies along the length of the cable. The load transfer from cement grouts to birdcage cables has been demonstrated in laboratory tests to be better than that of standard 15.2 mm diameter seven wire cables. The manufacturing process also allows for a wide range of capacities which may be specified by design engineers. The various birdcage cable configurations have been applied as rock reinforcement in a number of Australian underground and surface mines.

Jan 1, 1990

By Hutchinson H

Froth flotation is applied to mineral sand concentrates in order to produce commercially viable xenotime concentrates. Experiments indicate that a xenotime product containing 38% Y203 at 47% recovery or 34% Y203 at 83% recovery can be obtained from a 27% Y203 feed. The process involves a primary stage of reverse flotation at which oxide and silicate gangue is floated, and secondary stage of direct flotation at which xenotime is floated. Of the various collectors screened an amphoteric compound was found to be effective at both stages. This was made possible by the addition of sodium silicate at the second stage, which acted as depressant for the remainder of the gangue. Similar studies on a low grade feed material were somewhat unsatisfactory as the grade achieved fell short of what was targeted.

Jan 1, 1990

By Robert Voisey, Robert J. Spencer

"LynnGold's MacLellan Mine is located about 8 km south east of Lynn Lake immediately to the east of the Keewatin River (Fig. I). The property is accessible by an all-weather road, leading north from the provincial highway 391, which links with the Town of Leaf Rapids and the City of Thompson to the south.The ore body, as outlined in the original feasibility study, is expected to produce in excess of 9.3 x IQ6 gm of gold and silver over the next 5 years. However, the deposit is open to depth and exploration is continuing on and around the main zone and the many satellite deposits.The start of construction of the MacLellan Mine and mill was scheduled to phase in with the closure of the Fox copper-zinc mine located 48 km west of Lynn Lake. The majority of the employees from the Fox Operation were either employed at the MacLellan Mine or relocated to Sherrin's Ruttan Operation.GeologyThe MacLellan gold ore deposit is located on the northern section of the Lynn Lake Greenstone Belt known as the Rainbow Trend. This Trend is a 40 km gold bearing rock sequence extending both east and west from the MacLellan Mine. The southern section of these two east-west trending structures is known as the Johnson Shear, this is also gold bearing."

Jan 1, 1990

By Adams. M. D.

Most of the cyanide lost in carbon-In-pulp plants is due to the reaction of cyanide with base metals and sulphides during leaching. Some cyanide is also lost in the adsorption tanks as a result of oxidative and adsorption reactions with the activated carbon. The high rates of cyanide loss in the elution and electrowinning stages are atributable to hydrolytic decomposition and anodic oxidation, respectively. However, the relative amount of cyanide lost during these two stages is small for a given amount of ore treated.

Jan 1, 1990

Milling Practices Ore is direct tipped into a gyratory crusher and crushed to minus 209mm and fed to stockpiles for the blending of grade into the mills. Secondary and tertiary crushing reduces the mill feed to minus 12mm. Mill feed is a blend of breccia and porphyry ore into two primary mills with the overflow to a regrind mill and then into the leach tanks, followed by a conventional counter current carbon in leach circuit. Underflow from the cyclones feeds back into the primary mills for additional grind. An unusual feature of the Mt Leyshon milling circuit is a desire to produce scatts. The scatt by product is the polished base rock of the Mt Leyshon Breccia clast and contains little grade. These scatts are produced because of the additional time and energy required to produce a proportionally small quantity of gold. The residence of these scatts in the mills decreases the mill feed rate. Scatts account for twenty percent of the mill feed and are screened from the discharge of the primary mills.

Jan 1, 1990

By P. G. Semple, K. W. Major, R. M. Nendick

As free milling oxide gold ore reserves are depleted, more mining companies are having to evaluate the available alternatives for treating refractory deposits. The selection of a treatment process can be very difficult; and, despite the claims of their respective proponents, there is no one process that will continuously prove superior. Selection of the optimum process for an individual deposit is contingent on the size of the deposit, the grade of the deposit and the refractory nature of the ore. Since extensive metallurgical test programs are usually required to determine the optimum extraction process, an inappropriate initial selection may prove costly and time consuming. This paper discusses the steps involved in evaluating a refractory ore in order to expedite the evaluation of the required process through the feasibility study stage.

Jan 1, 1990

By B. Madelin

Over the last ten years, Minemet Recherche and Metaleurop have used an approach in order to investigate and improve the operation of its Smelting furnace and its lead blast furnaces. This approach gives importance- to three complementary means of investigation : - Probing campains in the industrial furnace (temperature and gas analysis profiles), - Chemical and physical modeling (coke combustion, sinter reduction modes, flows patterns, ?.) , - Staged mass and heat balances or kinetic model. This allows to define the limits of operation of each blast furnace and to predict the influence of operating parameters on the furnace performances. For the zinc Imperial smelting furnace, the probing results show the existence- of both an Isothermal reserve zone at 1015ºc and a chemical equilibrium between ZnO and gas which makes possible the use of a practical model for heat and material balances. In particular, very good prediction on the influences of operating parameters can be made. On the contrary, for lead blast furnaces, the probing results show that the thermal and chemical equilibria are not reached. Consequently, classical models for staged heat and mass balances are not sufficient. The use of the other means allows then to characterize the specific influences of operating parameters on the thermal instabilities of these furnaces and their allowed limits.

Jan 1, 1990

By Frank J. Susko

The U.S. Bureau of Mines is developing a process for removing metals from mining and mineral processing waste streams by precipitation. The precipitation process is accelerated by flocculation when a high molecular weight polymer is added. Infrared (IR) studies were performed on zinc hydroxide [Zn(OH);J, copper hydroxide [Cu(OH);J, and zinc sulfide (ZnS) flocculated with both non ionic and anionic polyacrylamide (PAM) and polyethylene oxide (PEO). The IR data were compared with general trends in the performance of the polymers observed during flocculation. These studies will help to understand the bonding between the precipitate and polymer and indicate the effectiveness of a flocculant for dewatering. Two types of bands showed up on the IR spectra; one type described the interlayer water of the flocs, the other described the organic bonds of the polymers. A general decrease in the areas of the three water bands, hydroxyl (O-H) stretching (3,200-3,500 cm-1), water bending (1,610-1,630 cm-1), and torsional oscillations (600-700 cm-1), indicate interlayer water being driven off, which is a favorable condition in flocculation. Shifts in the O-H stretching band indicate water bridging between the precipitate and polymer. Shifts in the amine (N-H) deformation, carbon-nitrogen (C-N) stretch band (1,600-1,610 cm-1) indicate the amine group of the PAM is involved in the bonding. Evidence suggests that ether oxygen of PEO is also involved in the bonding process.

Jan 1, 1990

By J. A. Ryder, M. U. Ozbay

An ERR-based methodology is presented for use in the re-assessment of the performance of stabilizing pillars, taking into account the effects of fracturing that can occur in pillar foundations under conditions of high stress. It is shown that the damage in the foundations of under-designed pillars can cause up to 30 per cent increases in ERR compared with the ERR for pillars with unfractured foundations. Despite this reduction in assessed performance, stabilizing pillars are still generally found to result in substantially lower ERR levels than alternative methods of reducing ERR, such as the use of stiff backfill or backfill ribs.

Jan 1, 1990

Fission track thermochronology is a well established method for reconstructing the thermal histories of rocks with particularly important applications in tectonic studies, detecting low-grade thermal events, sedimentary basin analysis and resource exploration. These applications take advantage of the limited stability of fission tracks, especially in apatite, when exposed to the temperatures found in the upper 3-4 km of the crust. Apparent fission track ages in apatites can define an invisible 'stratigraphy' in otherwise homogeneous rock masses that can give valuable information on thermal, tectonic and erosional events. Quantitative modelling of the thermal annealing of tracks in apatite shows that distinctive profiles of apparent fission track age can be related to a number of simple thermal history styles. The main types of profile observed tend to be either an essentially linear decrease of apparent age with increasing depth, which relates to continuous uplift and denudation, or a concave-upwards profile produced by partial annealing in environments of tectonic stability or burial. More complex thermal histories produce compound profiles which are essentially just combinations of these two elements. Track length information allows the apparent age profiles to be interpreted in much greater detail. Examples of the major profile types have now been identified in various geological environments and can be analysed to give information about, for example, uplift and denudation rates, the timing of uplift or low-grade thermal events and maximum palaeotemperatures experienced during burial.

Jan 1, 1990

By Yve Fourmanoit

"This paper discusses the exploitation of shallow underground deposits in a very altered geological environment. The methods, their adaptation to local conditions, their evolution, dilution control and recovery of mineral reserves will all be dealt with.The recovery of the B zone crown pillar under 40 m of till that was originally saturated with water, is of particular interest.Future underground development and production start-up of the A-2 zone, organization of mining operations, mechanical services, group incentives and safety practices will also be given.IntroductionThe underground deposit of B zone is not very deep. A 300 m shaft provides access to the mine. In addition , exploitation sublevels are developed every 20 m and are linked by a service ramp. The overburden located on top of the deposit is 40 m thick and is composed of a very dense till.A detailed work plan was initiated to permit mining under the overburden. To do so, it was imperative that efficient methods be developed. At a time when an accident at the Belmoral Mine shook the mining world , it was a task to convince provincial authorities that it was safe.While B zone was being mined , development began in the A-2 zone deposit which has recently been put into production (Figs. 1 and 2).The intention of this paper is to provide an outline of the mining method s and their particular aspects. To do so, some of the mine services are described and a brief outline of the under ground department is provided."

Jan 1, 1990

The movements of the major continental cratons and the distribution of the principal tectonostratigraphic terranes are reviewed in the Circum-Pacific region during Phanerozoic time. It is concluded that major periods of orogeny and consolidation of accreted terranes in the Circum-Pacific region is best correlated with periods of advance of cratonic blocks over the Pacific Ocean basin combined with relative convergent to transpressive motions between the cratons and the Pacific Ocean plates. Continental collisions and collision of terranes with continental margins has not been a significant geodynamic process in Circum-Pacific tectonic evolution. The permanency of the Pacific Ocean basin throughout 500 MA is remarkable. It appears no continental block or large continental fragment has ever entered or crossed the Pacific Ocean basin since early Paleozoic time. This area where no continent has entered for 500 MA is almost coincident with the present Pacific Ocean basin and seems associated with the 25 to 100 meter geoid high which dominates the present-day figure of the Earth.

Jan 1, 1990

By J. H. Tylczak, R. Blickensderfer

Impact and abrasion properties of various commercial US grinding halls were evaluated and compared by the Bureau of Mines, US Department of the Interior. Laboratory tests were conducted on balls obtained from eight major US manufacturers. The halls included forged steel, cast steel, and alloyed white cast iron and were subjected to repeated impacts until they broke or until 300,000 impacts were exceeded. Pin abrasion tests also were conducted. The results showed wide differences in impact lives, ranging from a few thousand to over 500,000 impacts. The life of inferior commercial halls was increased five to six times by a laboratory tempering heat treatment. For halls that did not break, the major impact wear mode was spalling and ranged from an average rate of 0.28 to 4.46 mg per impact. The softest halls (steel) had excellent impact resistance but low abrasion resistance. The abrasion resistance of the steel halls generally increased with hardness. The alloyed white cast irons had about twice the abrasion resistance of the steel halls. Users should become aware of the wide variations among commercial halls, and ball manufacturers should be aware that their product can he improved.

Jan 1, 1990