Search Documents

By N. S. Dalal, Xianglin Shi

"INTRODUCTIONEpidemiologic studies of workers in chromate-ore related industries, 1-3 and stainless steel welding and related occupations4 have shown that they have about 20-40 times higher risk of throat or respiratory track cancer than controls. Although the actual carcinogenic substances were not identified in these statistical studies, Cr(VI) compounds (for example, calcium chromate, zinc chromate, and lead chromate) were implicated as the causative agents, whereas Cr(III) compounds were not suspected as carcinogens. s These suggestions were supporte4 by laboratory studies wherein many Cr(VI) compounds produced sarcomas at the implant or injection sites.1,5 Squamous cell carcinomas and adenocarcinomas closely resembling human lung cancer were induced by intrabronchial implants of calcium chromate in rats, 6·7 whereas Cr(DI) oxide and Cr(lll) sulfate did not induce any tumor formation.6,7While the mechanism of the chromate-induced carcinogenicity is not fully understood, it is generally thought8 that it involves some damage to DNA. Specifically, it has been reported that: a) the chromate ion, henceforth referred to as chromate, can pass through the cell membrane and enter the cell while CR(DI) does not, 9 b) chromate does not interact with either native or denatured DNA 10 while Cr(III) does, 11 and c) the final Cr-DNA complex isolated from cellular reactions of chromate is Cr(III)-DNA, with Cr(III) binding to the phosphate groups.12,13 Thus the important question is: since Cr(DI) cannot pass through the membranes, how does Cr(III)-DNA complex form? For this to happen, Cr(VI) must be reduced to its lower oxidation states, 14 ultimately to Cr(III), by some reductants in the cellular environment. Unless this reduction occurs, the DNA would not be damaged and therefore no chromate carcinogenicity would ensue. Thus the reduction of chromate to its lower oxidation states seems to be a key step in the chromate carcinogenicity .1s One of the major reductants in cellular environments is thought to be glutathione (GSH), both outside and inside the cells.16-lB Some evidence for the role of GSH in the chromate toxicity was provided by recent studies showing that exposure of hamster cells to non-toxic levels of added selemite increases the levels of GSH as well as the Cr(VI)-induced DNA strand breaks,19 and that such DNA strand breaks in hepatocytes also change in direct proportion to the GSH content. 20,21 These observations were interpreted as implying that the reduction of chromate by GSH to some reactive intennediate is an important step in the chromate carcinogenicity. 20.21 In · the present undenaking22 we have used electron spin resonance (ESR) and spin-trap methodology to investigate the reduction of chromate by GSH and find evidence for the involvement of the glutathionyl radical (GS ·) as well as Cr(V)-intermediates."

Jan 1, 1990

By R. A. Jankowski

The U.S. Bureau of Mines has conducted a study to identify the sources of respirable dust and appropriate dust controls applicable to today's high tonnage longwall faces. The primary source of respirable dust identified is the cutting action of the shearer; however, the pct contribution of dust from coal transport through the stageloader/crusher was significant. This was primarily due to the high rate of mining, requiring rapid and constant coal transport. Techniques implemented for the control of shearer-generated dust included high drum water flow rates, deep cutting, shearer-clearer-type external water spray systems, and radio-remote control. The high water flow rates, and an enclosed stageloader with scrubber, were used to control dust during coal transport. No novel or effective control technology exists to control dust during support advance. Administrative controls for dust avoidance, and manual and batch-activated electro-hydraulic control systems were used to keep support movers out of the dust generated during support advance.

Jan 1, 1990

Reduce the potential of haulage related injuries in underground mines by providing a method for quickly assessing the state of repair of mine haulage track. The Problem Currently, there are no established standards or procedures for inspection or cleaning of underground mine haulage track. Many track defects are hidden from an inspector because of layers of dirt and debris on the ballast, spikes, fishplates, etc. When a visual inspection can be performed, it may be highly subjective, except for a few items that can be categorized or counted, such as missing bolts or spikes. Track inspectors may even become tolerant of defects that can gradually worsen. For these reasons, mechanical inspection methods are needed to supplement visual inspections. Approach The Bureau investigated this problem and designed a towed vehicle to both mechanically clean and inspect underground coal mine haulage track. The vehicle was developed using a systems approach, paying particular attention to human factors issues such as operator field of view, operator ingress-egress, control positioning, and seating design. The prototype was built using simple fabrication techniques and off-the-shelf components.

Jan 1, 1990

By M. G. Dellow, D. W. Hendriks

"In early 1988 the decision was made by Noranda Minerals Inc. to install pressure filters at the GECO mill to replace the vacuum disk filters and bunker-C fired rotary kiln dryers. Two filters were installed, one for copper concentrate and one for zinc concentrate. Completion of the project was scheduled for the third quarter of 1989. The filters were made operational in October 1989. Some work remains to be done yet on loadout conveyors for total project completion. Capital expenditures for the project have been approximately $2,700,000 to date. The paper describes the selection criteria for the filter, the installation, startup and associated problems.1. INTRODUCTIONThe filter model chosen for the project was the Verti-Press model VP-50-6(7) (Figures1 ,2 and 3) by Filtra Systems of Farmington Michigan, USA. The decision to purchase the Filtra Systems filter was based on gaining familiarity with a different, mechanically simpler pressure filter than the Larox design and to a lesser extent a necessity for repairs to the the disc filter, rotary kiln dryer system used at the GECO operation for its' copper and zinc concentrates. The fact that it is manufactured in North America was an important consideration. The same basic principles of pressure filtration as the Larox machine are used but the implementation is quite different and somewhat simplified with some interesting innovations. 2 filters were installed to allow direct and immediate comparison of the same machine on both fine and coarse materials. Copper concentrate is reground for cleaning on the flotation circuit while zinc is not. Screen analysis of composited samples of concentrates for 1988 indicated that expected copper concentrate would be approximately 66% minus 400 mesh and zinc 50% minus 400 mesh (Tables 1 & 2).The filter is composed of six horizontal chamber module layered vertically and held together in a frame by 1 O large bolts; torqued down to 4000 ft-lbs. 6 individual belts are used; each with its own drive system. The belts themselves are of a 3 piece design with a filter cloth portion, a support belt and a rubberized intermediate portion. They are held together with steel clipper lacings. A basic description (1) of the filter operation is as follows. ""The horizontal filler chamber is closed by hydraulically pressurizing seals across each end of the filter chamber to 200 psi. The feed pump then pumps slurry into the filter chamber. Suspended solids are retained on the filter belt and the filtered solution drains into a lower drip tray and flows from the filter by gravity. At the end of the filtration or feed cycle, a rubber diaphragm in the filter chamber is pressurized hydraulically to 100 psi pressure. This removes all free liquid from the filter chamber and the filter cake. After the diaphragms are retracted the filter cake is blown with compressed air to remove any residual cake moisture. The seals are then retracted and the belt is advanced to discharge the filter cakes. During the cake discharge the belts are washed with a spray header located at the drive end of the filter. The belt assemblies move one (1) complete revolution during the cake discharge cycle. The cycle automatically repeats until the filter is shut down by the operator."

Jan 1, 1990

By Knasmillner

During blasting body wave interaction with geometrical surfaces induces Rayleigh-waves which propagate along free surfaces, e.g. crack faces or delaminated rock layers. These Rayleigh-waves carry most of their energy within a very shallow surface layer and propagate with very little attenuation in real rock materials. Upon interaction with a crack front a very strong mixed mode stress intensity factor may result and lead to fracture initiation. On the basis of experimental photomechanical results the history of dynamic stress intensity factors Kt and K2 will be studied in Detail.

Jan 1, 1990

By L. I. Rosato

A novel hydrometallurgical process for the recovery of silver and gold from neutral leach residue that is based upon leaching with thiourea, is described. Laboratory and pilot plant studies have shown that 80-90% of the silver and 60-70% of the gold can be recovered by:? ( i) leaching zinc calcine with 'Spent electrolyte at pH 2.0-3.0 to generate a precious metal-bearing zinc ferrite residue, (ii) leaching of the thickened zinc ferrite with 3-5 g/L thiourea in a six stage carbon-in-pulp circuit, (iii) elution of silver and gold from the loaded carbon with a thiourea- butanol solution, (iv) thermal regeneration of the stripped carbon and (v) recovery of the precious metals from the pregnant eluate by cementation with zinc dust. The reasons for adopting the thiourea CIP leach and the preferred operating parameters for each process step are presented. The requirements for the destruction of any thiourea transferred to the zinc circuit are outlined, and the results of an integrated one tonne/day pilot plant operation at Canadian Electrolytic Zinc are given.

Jan 1, 1990

Robertson Diasol have developed a spectral gamma-gamma tool fully able to withstand borehole conditions. Spectral data is digitally recorded across 256 channels depending on energy levels of the photoelectric effect. Data processing is being developed with the objective of calibrating channel amplitudes to mineral type which will lead to a direct log of selected mineral grade as a continuous trace with depth.

Jan 1, 1990

By David S. Bowling

The ER-300 Series White Recorders were developed to provide on economical, yet invaluable instrument for those who desire permanent recordings of such data OS displacement, vibration, concussion (air borne effect) and velocity information. The precise monitoring of earth displacements and air blast magnitudes aids quarrymen and construction contractors in estimating safe blasting limits when operating in populated areas. A refraction model is available for recording velocities which permit the determination of weathered zone depths as well as the .depths to other subsurface formations. The dual purpose (Refroction- Displacement) systems ore utilized for velocity studies and displacement - oir blast measurements.

Jan 1, 1990

By J. M. Rebstock

Recent re-classification of crystalline silica as a potential human carcinogen has resulted in a new limit of 0.1% free silica in bulk powdered minerals. Detection of silica at this level can be expected to severely challenge or exceed the capabilities of existing protocols for x-ray diffraction, the traditional method for free silica determination. Automated SEH-EOS analysis provides an attractive alternative method, with direct analysis of individual particles for the determination of the concentration of free silica, and a direct measurement of silica particle sizes. This paper will discuss automated SEH analytical procedures, sample preparation, and statistical considerations.

Jan 1, 1990

By N. S. Dalal, Xianglin Shi

"Electron spin resonance (ESR) spin trapping experiments have been carried out to investigate the mechanism of sulfite oxidation em¬ploying 5,5-dimethyl-l-pyrroline-1-oxide (DMPO) as a spin trap. The results show that sulfite autoxidation, catalyzed by Mn(II), involves not only the SO-3 radicals but also the •OH radicals. An addition of H2 02 to the sulfite aqueous medium significantly increases the •OH radical formation. This result provides new clues to the chemical mechanism of the sulfite oxidation and the sulfite toxicity.INTRODUCTIONStudies of the oxidation of the sulfite (SO 2-/3) ions under various conditions are of high current interest because excessive exposure to sulfite is toxic and the origin of this toxicity seems to involve sulfite oxidative pathways [1]. An important fact is that human exposure to sulfite is on the increase [1,2]. Some of the increase in the sulfite exposure is linked to the fact that SO2 is a major air pollutant [2] and in aqueous media SO2 exists in equilibrium with SO2-/3. In addition, beverages and foods are common sources of sulfite intake. For example, sulfite is used extensively in the wine industry as an inhibitor of yeasts and bacteria and is present in finished wines in concentrations up to 6 mM [1]. Sulfite is also often added to dehydrated fruits, vegetables and soups, as well as fruit juices and beer [1,3,4]. Because of these, the mean daily intake of sulfite from diet (in the United States) has been estimated to be between 0.0014 and 0.14 mM/kg body weight [1]. At such high levels, sulfite exposure can have toxic effects, such as the induction of an acute asthmatic state [5,6]. Sulfite also appears to have adverse genetic effects [7] and can act as a mutagen or comutagen [8] and a cocarcinogen [5,7-9]."

Jan 1, 1990

By L. Shuyi

In order to develop the pulsating high gradient magnetic separation technology, a type of laboratory pulsating high gradient magnetic separator (PHGMS) has been manufactured. Experiments of its separating performance were carried out. They show that PHGMS can significantly increase the grade of the magnetic product and avoid the matrix to be blocked. The characteristic curve of the pulsating fluid was measured and a formula for estimating the grade of the magnetic product was established in PHGMS.

Jan 1, 1990

By Arnold O. Tanner

The domestic mining industry gained more strength in 1988 as the healthy comeback that became evident in 1987 continued and grew for many commodities. The increasing and more stable commodity prices, still predominantly in the metals sector, reinforced both the new ways of conducting business and the use of technological advancements in successfully lowering operating costs during the last 4 to 6 years. Some commodities and companies still struggled to survive, but increases in productivity and profits were becoming more common.

Jan 1, 1990

By Caress ME, Knight MD

The eruption 75,000 y ago of the Younger Toba Tuff ignimbrite and associated ash-fall ranks as the greatest known volcanic event of the past million years. The ignimbrite is known to cover 21,000 km2 (it may extend farther under alluvium of the coastal plain) and forms a low-angle depositional shield centered on the Lake Toba caldera. The ignimbrite is largely nonwelded and shows systematic outward decreases in lithic and crystal contents and clast sizes. Coarse lithic lag breccias that occur at places 85 km apart point to two or more vents on a fissure having this length. The extensive associated ash-fall traceable as far as Malaysia and India is evidently a co-ignimbrite ash but could have a phreatomag-matic component. The Lake Toba caldera measures95 x 35 km and is >1 kn deep. It is not a single caldera but comprises several contiguous depressions and grabens diversified by two re-surgent domes. Earlier parts of the caldera are related to at least two earlier ignimbrites including the Older Toba Tuff dated by Chesner at 0.5 Ma. The caldera is elongated parallel to, and is only 25 km from, the great Sumatra strike-slip fault, and it can be considered almost certain that the caldera is in part a kind of pull-apart structure. The ignimbrites are very crystal-rich. There is no reason to think basaltic magma was involved in their emplacement. Together with ash-falls they have a total volume of several thousand cubic kilometers. They can be categorized as originating from partially crystallized granitic magmas that erupted because tectonic pull-apart occurred several times across the pluton. Small rhyolitic lava domes on fault-lines comprise the youngest volcanic products.

Jan 1, 1990

By Gordon K. Jorgeonson

Much of the modelling of blasting operations has been devoted to simulating blasts in open pit mines and quarries . This has been the most obvious application and has been reported in many papers and discussions in the past.

Jan 1, 1990

By J. Stachurski

Flotation tests were carried out on 6 coal samples of different rank as well as their oxidized samples. A mixture of diesel oil and alcohols was used in these tests. Surface oxidation caused a distinct decrease of the flotation recovery with some improvement in the grade The reduction in the recovery increased with increasing the concentration of the oxidizing agent. The floatability of low rank coals was affected by oxidation to a higher degree than medium and high rank coals. The recovery size curves of oxidized samples mere similar in shape to that of non-oxidized coals.

Jan 1, 1990

By J. D. Scott

The counter-current jarosite acid wash circuit presently in operation in the zinc plant produces a combined jarosite plus Pb/Ag residue which is discarded. Extensive pilot-scale testwork, and some past in-plant operational experience, has shown that the zinc plant can be easily reconfigured to produce two residues during periods of high silver feeds and/or prices. Plant.optimized circuit configurations are available for silver recovery to a Pb/Ag residue and are in use for the prevention of Pb/Ag-jarosite formation in both the neutral and high-acid leaching circuits. Silver in the zinc plant undergoes several changes in state as it proceeds through these circuits. The roaster calcine is ~3:1 silver sulfate: silver metal, with metallic silver mainly as micro-Inclusions In an aluminosilicate phase. In neutral leach residue, the majority is as silver sulfide or Pb/Ag/Zn-sulfide coatings on unroasted sphalerite grains, with minor Pb/Ag-jarosite and some residual metallic silver in unreacted alumina-silicate grains. In high-acid leach residue, silver occurs as Se-rich silver sulfide particles in sulfur/jarosite ball aggregates, as silver sulfate impregnations in silica-gel masses and in solid solution in Pb/K/Zn~jarosite. Silver concentrations in solution range from 20 to 60 ppb.

Jan 1, 1990

By John N. Ludden, Maurice Rive, Hillar Pintson

"Quelques soixante-dix-sept plutons présents dans la Sous-Province de Pontiac et dans la partie centrale de la Sous-Province de I’Abitibi ont fait I ’objet d’une reconnaissance systématique. Ils ont été regroupes en huit suites plutoniques majeures et trois suites mineures à partir de critères géologiques et petro logiques. Parmi les suites majeures, quatre représentent I' activité intrusive la plus ancienne dans la région. L’une d' entre e/les est représentée par deux complexes anorthosito-gabbroi' ques lites et les trois autres comprennent les orthogneiss dioritiques a leucotonalitiques et les intrusions dons la composition varie de diurétique et granodioritique à leucotonalitique. Leur mise en place peut être pretectonique a syn ou tarditectonique; certains plutons sont synvolcaniques. Quelques data/ions U! Pb effectuées à propos de ces roches donnent des âges s' étalant entre 2 718 et 2 694 MA. Les données géochimiques indiquent la présence des deux lignées magmatiques, tholemique et calcoalcaline bien qu’il n'y ait aucune évidence de relations entre elles dans I' espace et dans le temps. Ces suites magmatiques différentes peuvent provenir soit d’une croute tholemique impliquée dans un processus de subduction soit directement du manteau.Les trois autres suites majeures comprenant des monzodiorites, des granodiorites et des monzonites ainsi que les deux suites mineures comprenant des syenites correspondent à un évènement intrusif plus jeunesse déroulant entre2 694 et2 680 MA. Ces roches sont syn, tarti a post tectoniques et sont enrichies en alcalins, Ba, Sr et terres rares legeres par rapport aux quatre suites précédentes. Leurs caractères chimiques prop res suggèrent qu' e/les proviennent d' une source différente par rapport à celle precedemment citee.La derniere suite plutonique majeure correspond a un monzogranite leucocrate, riche en pegmatite, également syn a tard tectonique, dont I' age n' est pas connu avec précision. ll représente le seul granite ""vrai"" de la région et dérive d’une anatexie soit des meta sédiments soit des granodiorites-tonalites plus anciennes. La troisième suite plutonique mineure correspond a quatre stocks de granodiorite porphyrique qui n’ont pas été étudiés en détail.ABSTRACTSevenly-sevenplutons have been identified in the east-centra/part of the Abitibi Subprovince and adjacent Pontiac Subprovince. These have been subdivided, on the basis of geological and petrological criteria, into eight major and three minor plutonic suite. Four of the major suite, which represent the oldest intrusive activity in the area, range in composition from dioritic-leucotonalitic orthogneisses to diorite-granodiorite/leucotonalite and include two layered anorthosite- gabbro complexes. Their time of emplacement ranges from pretectonic to syn-late-tectonic and some plutons are synvolcanic. U-Pb zircon ages for these rocks range from 2 718 to 2 694 Ma. Geochemical data indicate the presence of both calc-alkaline and tholeiitic magma series for these rocks although there is no evidence time and space relationships between the two. The different magma series also suggest the derivation of these rocks from two sources, either from subduced tholeiitic crust or directly from the mantle. Three major monzodiorite-granodiorite, monzonite, and two minor syenite suites comprise a younger inlrusive event ranging from 2 694 to 2 680 Ma in age. These rocks are syn-, late- to post-tectonica and, compared to the above four plutonic suites, are enriched in alkalis, Ba, Sr and light Rare Earth Elements.Their distinctive geochemistry suggests that these rocks were derived from a different source region than for the older plutonic suites. The remaining major plutonic suite consists of leucocratic, pegmatite-rich, monzogranite-granodiorite. These rocks are also syn- to late-tectonic but their ages are not known with precision. They are the only ""true"" granites in the area and were derived by the partial melting of either older"

Jan 1, 1990

By L. C. St. Arnaud

"Open pit mines can produce large disturbances within regional hydrogeologic systems. The degree of disturbance and the consequences on the local environment depend on the size of the pit and on the physical setting of the mine. Comparisons and contrasts are presented for three Noranda base metal open pit mine sites.The Brunswick Mining and Smelting No 6 open pit has a surface area of 11 ha and a depth of 185 m. It is located within complexly deformed schists and meta-volcanic rocks. The massive sulphide and iron formations visible along the north and southwest walls of the pit generate acid drainage. Mining ceased in 1983, and the pit is presently being filled with waste rock and neutralized drainage water. Water balance calculations estimated a total fill up time of sixteen years. As the water level rises, leakage to groundwater could take place across a fault zone intersecting the pit.The Mattabi Mines F-Group pit has a surface area of approximately 3 ha and a depth of 50 m and is also set in meta-volcanic rocks and acid generating iron formations. Production at this site ceased in 1982, and the low pH pit water is neutralized and pumped into a nearby lake at least every five years. Major water inflows are from precipitation and groundwater. Groundwater mounds within adjacent high land surrounding the pit provide a natural hydraulic barrier to groundwater flow, except for the southeast side. As a consequence, the pit water elevation is being kept below the elevation of the nearby creek in which some of the pit water could drain.The Bell Copper open pit covers an area of 40 ha and is 270 m deep. With present ore reserves, the mine might be in operation until 1992. The geology around the pit consists of andesitic tufts, siltstones and shales, and the acid generation potential of the rock is relatively low. A recent hydrogeological study estimated fill up time by precipitation and groundwater to be in the order of 260 years.With increasingly more stringent requirements for mine closure, it is anticipated that more detailed hydrological and hydrogeological studies of open pits will be required to determine post-closure environmental impacts and the suitability of open pits for mine waste disposal."

Jan 1, 1990

By Dunlop GA

Pilot Plant confirmatory testing of the treatment route developed in the Metallurgical Laboratory is an essential factor in the development of complex ore bodies. Objectives should be well defined to permit the efficient planning and cost effective operation of the pilot plant project. The primary objective for the pilot plant should be to confirm the viability of the developed flowsheet on a continuous basis, examining only major variables such as ore types, quantum changes in grind, comparison between bulk and sequential flotation circuits, use of flotation columns, evaluation of autogenous grinding and production of samples of concentrates for market evaluation. Secondary objectives may include the collection of engineering design data and the production of a comprehensive report to Bankable Document standards to provide technical support for capital financing. The complexity of the ore body and the scale of the final operating project together with the pilot plant objectives will determine the extent of the pilot plant operations. The level of expenditure associated with a pilot plant can vary, in total cost and as a percentage of the total development capital investment required to take the prospect from exploration to a producing mine. Factors contributing to expenditure are discussed. Associated with cost considerations is the level of confidence mining company investors can have that their capital investment will return dividends.

Jan 1, 1990

By Natalie A. Sapola, Knox Van Dyke, Jean Rabovsky, Vincent Castranova, William H. Pailes, Melanie McPeek, Deloris J. Judy

"INTRODCJCTJONPlatelet activating factor (PAF) is a glycerophospholipid (1-0-alkyl-2-acctyl-sn-glycerol-3-phosphoryl choline) which has been shown to mediate a broad range of biological activities. 1·3 Its pulmonary actions include contraction of pulmonary tissue,4 secretion of leukotrienes from leukocytcs,5 airway constriction,6 pulmonary edema,7 and enhanced migration of neutrophils into the airspaces of thelungs.8-9PAF can be released from several different cell types, such as, basophils, neutrophils and alveolar macrophages, in response to a variety of particulates or membrane stimulants which include zymosan, calcium ionophore, phorbol esters, chemotactic agents, and endotoxin. 1~1 3 Therefore, PAF may play an important role in the development of pneumoconioses by mediating pulmonary responses of lung cells to a variety of occupational dusts. To investigate this possibility, we determined the effects of P AF on several physiological parameters of neutrophils, alveolar macrophages, and alveolar type Il epithelial cells.METHODSIsolation of CellsNeutrophils were isolated from human blood by dextran settling and centrifugal elutriation.14 Isolated neutrophils (93% pure) were resuspended in HEPES-buffered medium (145 mM NaCl, 5 mM KCI, 10 mM HEPES, 5 mM glucose, and 1 mM CaC12; pH = 7.4). Cell number and volume were determined with an electronic cell counter equipped with a sizing attachment.Rat alveolar macrophages were obtained by pulmonary lavage with ea2+, Mg2+-free Hanks balanced salts solution. 15 Alveolar macrophages (94% pure) were resuspended in HEPES-buffered medium, counted, and sized electronically.Rat alveolar type Il cells were isolated by enzymatic digestion for 35 minutes at 37°C with 40 µ/ml type I elastasc and 0.1 % collagenase and purified by centrifugal elutriation. 16.17 Type Il cells (92 % pure) were resuspended in HEPES-buffered medium for measurement of membrane potential, oxygen consumption, and trypan blue exclusion. Type Il pneumocytcs were resuspended in 0.1 M NaCl plus 0.05 M HEPES (pH = 7.8) to measure cytochrome P450-dependent activities and aggregation. Cell size and number were determined electronically."

Jan 1, 1990