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By Tedsen L. F., Dorn J. E., A. E. Flanigan

since aluminum-alloy sheet may be used occasionally at moderately elevated ternperatures, the effects of temperature on the mechanical properties are of interest. Recently the short-time tensile properties of several high-strength materials have been studied at temperatures up to 3750°F.l This paper deals with stress-rupture and creep properties at the same temperatures. The work was done at the University of California as a portion of the project NRC-548. It was financed by the War Production Board and was supervised by the Office of Production Research and Development. This paper has been released for publication by the latter agency. The following materials were studied, all in the form of 0.040-in. sheet: Alclad 24s-T Alclad 24s-T8I Alclad 24s-T86 Alclad 75s-T R3oI-T (clad) Specimens were loaded in tension in the cross-grain direction. Testing temperatures included 94°F., 2II°F., 300°F., and 375°F. Stress levels were selected to cause rupture in times ranging from several minutes to 1000 hr. In each test the following data were obtained: (I) fracture time, (2) elongation at fracture, (3) the complete strain-versus-time curve (creep curve), (4) creep rate (defined in a later section). Materials Materials for specimens were obtained from the manufacturers' commercial

Jan 1, 1947

By Matthew Baumann, Bahram Sameti, Tafazoli Zeng Hairong, Edmond Chow

An automated, centralized, image-based rock fragmentation analysis system provides blast engineers with the benefit of minimizing tedious and mundane work, and allows them to focus on their expertise of blast optimization. In typical manually-operated image-based rock fragmentation analysis, much time is spent on collecting proper images, handling and transferring data, and processing for fragmentation.

Jan 1, 2013

By AIME AIME

AMONG the members of the Institute there are thirty-three who have been members for a half- century or-more Some time ago a professor of psychology made a careful study of a group of unusually brilliant children to determine whether there was any truth in the general belief that a brilliant mind is usually to be found in a physically sub-normal body. He definitely proved the exact opposite and it is now known that children who are above the average in mental capacity are also above the average in physical health and strength.

Jan 1, 1929

By Fei Ruan, Chang Jie, Jieyu Zhang, Jifang Xu, Kuochih Chou

"Viscosity is an important physical parameter of slag in metallurgical processes. Most studies of aluminosilicate and aluminate systems assume that aluminum occurs in tetrahedral coordination. In this case, the O/Al value was utilized to describe the slag structure in terms of the network character of aluminosilicate and aluminate systems. Composition and viscosity data from the literature and the trends were analyzed according to the O/Al value and temperature. It is shown that the O/Al value explains the trends in more than ten systems, containing more than 200 data points. In aluminosilicate system, the trend that viscosity value changed with the O/Al value which implies that alumina works as network modifier such as basic oxides or works as network former. In aluminate system, irrespective of the system and temperature, viscosity decreased steadily when O/Al value increased.IntroductionMetallurgical slags, which are made of oxides and many also contain fluorides, play an important role in metallurgical processes such as iron making, steel making and secondary refining processes. Aluminosilicate slags are applied in a wide range in metallurgical processes. A polymerizing effect of the addition of aluminum and an association of aluminum with low-field strength cations is further supported by the physical variations in aluminosilicate and aluminate systems. The behavior of alumina in silicate melts has been studied by various authors [1-6]. It is generally accepted that Al2O3 is amphoteric [7] because Al3+ ions can behave in profoundly different ways in a silicate melt. When added to a pure silica melt, Al2O3 acted as a network modifier, breaking the bridging oxygen of the pure silica network, thereby decreasing the viscosity in a similar manner to other network modifiers, such as CaO, MgO etc. to form [1/2Ca (AlO4)]4- complexes. However, when added with alkali or alkali-earth metal oxides, some of the Al3+ ions assumed tetrahedral coordination and replaced Si in the liquid network, the missing charge was compensated by Me+ or Me2+ ions. Therefore Al2O3 acted as network former [8, 9]."

Jan 1, 2011

By Yasser Mohamed

Daily field management of earthmoving operations requires quick and regular decisions for allocating available equipment to different jobs on a project. A general foreman?s day starts with matching several activities with a suitable set of available equipment to achieve the highest productivity and lowest unit cost. Usually, this decision-making process needs to be quick, and depends to a great extent on the foreman?s experience, which varies from one individual to another. Many analytical solutions with various degrees of sophistication and optimization exist to address such decisions. However, adopting any of these solutions is contingent on how accessible and easy-to-use the solution is. This paper discusses the development process of a webaccessible solution for evaluating earthmoving fleet composition and allocation scenarios. The solution relies on discrete event simulation and an optimization backend engine, but introduces the user with a simplified and easy-to-use interface that is accessible from any mobile device, and is customized to specific user?s needs. The developed system gathers most equipment and site-related input data from a company?s information systems to minimize user input. The user mainly needs to formulate equipment and job combinations and allocation scenarios (e.g. soil type, quantity, and hauling distance), according to equipment availability each day. Then the system will evaluate the productivity and unit cost estimates for each scenario, allowing the user to choose the most suitable one. It may also be used to automatically recommend the optimum solution given an available list of equipment. The paper presents the process followed in prototyping the proposed system in collaboration with a major Canadian earthmoving contractor, and customizing it to the user needs within the company. It also describes the overall structure of the developed system and its core simulation model.

Aug 1, 2013

By Gilles Tremblay

The legacy of orphaned/abandoned mines, with their associated environmental liability, human health concerns and the financial costs of clean up is a serious issue facing Canada. In 1999 and 2000, a number of stakeholders put forth requests to Mines Ministers to establish a joint industry-government working group, assisted by other stakeholders to review the issue of abandoned mines. The Ministers supported this initiative and asked that a multi-stakeholder workshop be organized to identify key issues and priorities. The Workshop on Abandoned Mines, held June 2001 in Winnipeg, developed consensus, guiding principles and recommendations that were presented at the Mines Ministers? Conference, September 2001. Ministers agreed on the importance of a large-scale program for the rehabilitation of orphaned/abandoned mines sites. A multi-stakeholder Orphaned/Abandoned (O/A) Mines Advisory Committee was formed and a plan was developed to study various issues relating to the implementation of remediation programs across Canada. Three task groups were formed to address the following key areas: Information Gathering; Community Involvement; and Barriers to Collaboration. The presentation will include a summary of the results of the three projects and the future work plan for the program.

Nov 1, 2002

By Dr. O’Neil Thomas J., Donald W. Gentry

"Who is the man who views the mines and promptly turns them down? Who is the one that thinks this is the short cut to renown? Who is it gives the bum advice to the innocent financier? The knowledge-feigning, theory- straining mining engineer." -Anonymous INTRODUCTION Taxes levied against mining properties and operations are a critical cost in the economic evaluation of mining investments. Indeed, taxes represent a substantial cost of doing business in the minerals industry and often have a significant impact on corporate investment decisions. A good example was the postponement of mineral development in the state of Wisconsin, primarily because of what was perceived to be excessive taxes imposed by that state. In many respects mining investments are no different from other industrial investments. Astute taxing authorities should recognize that geologic endowment is a necessary but clearly not a sufficient condition for mineral investments. The fact that a mineral deposit exists does not necessarily mean that it will ultimately be developed-a point that many taxing authorities fail to recognize. While it is true that ore deposits are not mobile in the sense that they cannot be physically moved to a district having more favorable taxes, corporate investment capital certainly is mobile and flows to ventures which maximize wealth to the firm. In short, higher taxes reduce project yields and tend to drive investment capital elsewhere. The appropriate type and level of taxation imposed upon the mining industry continues to be a very controversial and emotion-charged topic. Mining activities have been taxed at various levels over the years due to widely differing taxation philosophies. Location has also influenced taxation policies, as evidenced by the diversity of tax laws and assessment procedures applied to mineral deposits by the various states. Indeed, mineral taxation varies from state to state, from county to county, and from one mineral commodity to another. Whether or not a given tax is appropriate for a specific mineral deposit, or even an industry, is a difficult problem to assess. First, the type or kind of tax which should be imposed must be considered. Second, it is most important to define a fair and unambiguous base against which to levy the tax. Finally, one must consider the tax rate to be applied to this base. It is the combination of these two components

Jan 1, 1984

By S. W. Parr, A. R. Powell

FOUR general methods have been used in the study of the decomposition of coal. The first has been directed toward the processes of coal formation, the second has been by means of microscopic studies, the third from the data of destructive distillation, and the fourth has made use of various solvents. Applying these methods to the sulfur of coal, it has been found that the organic sulfur of plant and animal life enters into the formation of coal and remains in organic combination in the final product. The inorganic sulfur is almost entirely combined as iron pyrites and marcasite. The infiltration of hydrogen-sulfide waters is doubtless a large factor in these combinations. Sulfates are found in very small quantities except where free oxygen has entered the coal strata. The mechanical mixing of detritus with the early coal material is another source of sulfur. In this case the sulfur is distributed in microscopic particles throughout the mass. In destructive distillation, a part of the sulfur comes off as hydrogen sulfide and various thiophen compounds, but this furnishes little information as to the nature of the sulfur compounds in the coal itself. The use of solvents has given valuable data concerning the sulfur compounds in coal. Fremyl and later E. Guignet2 noted the action of alkaline solutions on coal after treatment with nitric acid and Anderson and Roberts3 showed the presence of large quantities of organic sulfur in the extract so obtained. In a study of the phenol extract of coal, Parr and Hadley4 found organic sulfur in the soluble organic material. These investigations proved the presence of organic sulfur in coal in addition to the inorganic forms, such as iron pyrites and sulfates. T. M. Drown6 attempted the analysis of the pyritic and sulfate sulfur as distinct from the organic forms by means of sodium hypobromite; no definite proof of

Jan 1, 1920

The fourth annual Mine Rescue Evaluation program was held in conjunction with the 1995 Institute convention at Crested Butte, Colorado. The Mine Rescue committee is chaired by Lynn Busskohl and is but one of 16 such committees of the institute. In 1995 seven teams participated in the program. They were BHP Minerals, The Coteau Properties Company, Decker Coal Co., The Falkirk Mining Company, Kerr-McGee Coal Corporation, Sabine Mining Co. and Western Energy Co. [ ] Professional evaluators who provided challenging scenarios for the near 60 persons were Jack Knight of Pensacola, Florida; Dave Medick of Northwestern Resources, Jewett, Texas; Joe Nugent of Idaho Springs, Colorado and Jack Peleaux of Innovative Access, Evergreen, Colorado. Each team was comprised of seven members and one trainer representing the states of Montana, New Mexico, North Dakota, Texas and Wyoming. This committee challenges the incoming Colorado vice president to locate a team for the 1996 program in Durango, Colorado. Five different scenarios were presented the first day of evaluation and three the second. Each team was given the pertinent information to solve the problem as they assembled at the site. The realistic industrial related scenarios closely simulated the stress of actual rescue incidents and were going on simultaneously. Each team was unaware of the circumstances until arriving on the scene. Lynn Busskohl presented an overview of the Mine Rescue committee work at the Monday Institute welcome session and invited all attendees outside to view the various pretend rescue operations. Valuable suggestions were made by the team of evaluators following each scenario. These teams are providers of immediate rescue and medical care for accident victims at their respective properties. The members are prepared to act with immediate and professional knowledge to save lives and prevent further injuries. [ ] Many donors financially assisted with the 1995 program. They are: Blattner Constructors; Butler Machinery Co.; CMC Rescue, Inc.; Galls, Inc.; General Equipment; PMI-Petzel Distribution, Inc.; SafetyMaster; Skedco and TIC of Wyoming. An adder to the 1995 convention was golfing on Saturday, June 24 for three foursomes. This may become an annual event if there is sufficient interest. Team meetings, tests and swap meetings were attended by all participants during the Friday thru Monday program. A fun competition took place after lunch Monday followed by a training session. All events were chaired by Lynn Busskohl. On Saturday evening, June 24 a reception for all mine rescue participants and spouses who had advance registered for the social event. The RMCMI Board of Directors was invited to attend and meet with the teams. As convention attendees, all mine rescue committee members attended the Monday night country western reception and Bar-B-Q with their families. This was followed by an adult western dance evening. The Mine Rescue committee looks forward to a 1996 return to Tamarron near Durango, Colorado which was the site of the first evaluation program. Plans call for all convention housing to be at Tamarron.

Jan 1, 1995

By W. A. Anderson

IN the pressure die-casting of zinc alloys it is customary to force the molten alloy under high pressure into a permanent steel die by means of a plunger moving in a bushing that has a clearance on the diameter of the order of 0.002 in. Successful operation of the plunger type of machine requires the presence in the zinc alloy of certain percentages of aluminum. Without these aluminum additions, the normal reaction of molten zinc on ferrous materials causes sticking of the plunger and a complete shutdown of the equipment. All of the zinc alloys used for pressure die-casting today contain approximately 4 per cent of aluminum, which is more than sufficient to make plunger operation feasible. The clearance between the plunger and its bushing is an important matter. As the space becomes larger, there is a loss in effective metal pressure. Ordinary gray cast iron served fairly well and is still used in some machines. However, the rate at which the plunger clearance increases with this material is considered by many to be far too great. There is, therefore, a serious interest in finding new materials more capable of retaining the desired clearance during long periods of use. Today many die casters are using special materials for plungers and bushings selected by the somewhat expensive and time-consuming test of actual experience. An analysis of the problem reveals two possible end points of plunger operation: (1) the building up of zinc-alloy plunger-material reaction products in sufficient bulk to cause sticking and (2) rapid solution, wear or erosion, all of which will increase the clearance to an undesirable extent. If neither of these takes place, the plunger will operate for a long time, of course. The authors have developed a laboratory apparatus in which the action of a plunger moving in a bushing immersed in molten zinc alloy could be simulated closely. Such a machine made possible a more rapid and less expensive survey of the available construction materials and an analysis of the specific alloying reactions taking place in the clear-ance area.

Jan 1, 1939

By H. Dykstra

Calculated wellbore pressures were obtained for parameters of radilcs ratio and permeability. In all cases bur two, after-production was allowed to occur for one day. The calculated pressure build-up data were compared with actual pressure build-up data from a condensate well. The paper discusses the comparison, gives reasons for, inability to match calculated (2nd actual data, and presents conc1usions derived from the comparison. INTRODUCTION Considerable information has been published on the decline in wellbore pressure for oil and gas fields resulting from production of fluids. Considerable information also has been published on pressure build-up for oil fields, but relatively little has been published for gas and condensate fields. Perrine' summarized the equations derived for pressure build-up in oil wells and showed how the different methods could be applied. On the other hand, very little theoretical information has been published on pressure build-up in gas or gas-condensate wells.2-4 Tracy,' by pointing out the similarity between the equation describing oil wellbore pressure decline and the equation describing gas wellbore pressure decline, showed how methods of pressure build-up analysis could be applied to a gas well. In analyzing pressure build-up data for gas or gas-condensate wells, it would be very desirable to compare actual pressure build-up data with calculated pressure build-up data. Such a comparison would lead to a better feeling for the quantitative picture of gas-well build-up curves and would help to establish a degree of confidence in a given build-up curve. This paper discusses the comparison and presents conclusions made from it. Calculated wellbore pressures are given for parameters of radius ratio and permeability. In all cases but two, after-production was allowed to occur for one day. The work was done in an attempt to evaluate the reserves of a gas-condensate field. As will be discussed later, it was not possible to make an evaluation. METHOD OF CALCULATION The method used for solving the depletion and pressure build-up behavior for a gas-condensate well was that developed by West, Garvin and Sheldon.5 or the IBM 704 computer program used, it was assumed that liquid condensing out of solution would have only a minor effect on the flow behavior. Therefore, the field was treated as having single-phase flow, with the gas saturation S, remaining constant at unity minus the connate-water saturation Sw. As will be discussed later, this may not have been a good assumption. It also was assumed that oil production could be considered as equivalent gas production by using a conversion factor based on an analysis of the liquid produced. An outer boundary condition of no-flow was assumed. BASIC DATA The data required for the study were reservoir properties, fluid properties and production data. Reservoir properties included the following: thickness h, 179 ft; porosity, 0.194; connate-water saturation, 0.43; gas saturation, 0.57; permeabilities k, 1.0, 0.5, 0.25 and 0.15 md; radius ratios re/rw, 800, 1,000 and 2,000; wellbore radius rw, 5 in.; initial reservoir pressure P, 6,529 psia; and reservoir temperature, 272°F. The selection of permeabilities was based on core-analysis data showing an average air permeability of about 2 md. With a relatively high connate-water saturation, the average effective gas permeability would be about one-half, or less, of the air permeability. The selection of radius ratios was based partly on the observed rapid decline in wellbore pressure during production and partly on the fact that the well was believed to be located in a relatively small fault block. Reservoir fluid properties were obtained from a reservoir fluid study on a recombined sample of gas and condensate. Gas formation-volume factors were calculated from pressure-volume measurements made at reservoir temperature. Gas viscosities were calculated by the method of Carr, et al,G from an analysis of the re-combined sample. These data are shown as a function of pressure in Table 1. The production schedule from the gas-condensate

By D. H. Davis

HAND picking was the earliest form of coal preparation, first practiced to improve the outward appearance of the coal being loaded and to remove any pieces that might appear objection- able to the buyer. It is still extensively practiced on the plus 1-in. sizes, and particularly on the plus 4-in. and larger sizes. The percentage of ash reduction that can be obtained by hand picking depends entirely upon the amount of free impurity occurring in the coal. In a particularly dirty seam, where a considerable quantity of rock occurs with the coal as mined, hand picking produces sizable reductions in ash. If the coal is prepared clean at the working face hand picking is a final check; in some cases, on the smaller sizes, it is practiced only to show that an effort is being made to prepare a clean product. Because of the variety and different methods of handling coal, the early plants were not always adapted for efficient hand picking. At most mines an attempt is made to remove the visual impurities at one or more of the following places in the surface plant:2 (1) in the tipple during screening; (2) on picking band, belt, or shaking conveyors;. (3) during the loading of the coal as it goes into the railroad car. Whatever the physical arrangements of the plant may be, the usual practice is to run the coal over the screen, picking table or boom at such a rate that each-piece of impurity is exposed to the view of the picker. Coal should be uniformly sized and spread out on the table so as not to exceed one particle in depth. The flow should be even in tonnage and the speed of travel should be from 30 to 60 ft. per minute and not 'exceed 80 ft. per minute. The dirtier the coal, the slower the speed required for a fixed number of pickers. Actually, picking capacity depends on the number of particles per minute that can be picked out and-rejected. The percentage of impurity removed is determined by this and the average weight of piece rejected. Handling a mixture of sizes from nut to the largest lump over the same picking table or conveyor is not conducive to efficient separation by hand picking because the lump hides the smaller impurities. Picking tables should not exceed 5 ft, in width, so that a picker on either side will be able to remove impurities from the center of

Jan 1, 1943

By R. Asmatulu

A method of improving the efficiency of solid-liquid separation during centrifugal filtration has been developed. It consists of increasing the pressure drop across the filter cake using extraneous means such as pressurizing a filter chamber. This method, which may be referred to as hyperbaric centrifugation, is designed to increase filtration rate during the drainage cycle and, hence, to produce drier cake. In the present communication, the results obtained in a series of batch centrifugal filtration experiments are presented. The results obtained on fine coal and mineral samples show that cake moistures are approximately 50% lower than the case of using ambient pressure.

Jan 1, 2004

By L. F. Wright

Operations of these two mining companies have some superficial similarities-geographical location, production rates, comparatively large ore reserves; but any critical comparison of mining and milling procedures or of economics must take into account the striking differences in geological environment and mineralogy of the respective ore deposits. The properties are only about 20 miles apart on an upland surface of moderate relief (part of the Interior Plateau of central B. C.) which occupies an area east of Thompson River between the towns of Ashcroft and Merritt. Being in the "dry belt" of British Columbia, water conservation is necessary at both operations.

Jan 12, 1963

By Parviz F. Rad

The Bureau of Mines conducted rock-cutting experiments under constant normal force and constant penetration in an effort to correlate laboratory data with those obtained in the field. Both independent and interacting groove spacing regions were studied, and optimum and critical cutter spacings were determined. For the laboratory work, the effects of specific energy, muck weight, groove depth, cutting coefficient, and size distribution of the muck for both independent and interacting grooves were studied. For field operations, forward thrust, torque, advance rate, and muck size distribution were the parameters studied. Satisfactory correlation is obtained between laboratory cutting results and field performance data.

Jan 1, 1974

In 2006, a total of 280 metal mining operations reported employment to the Mine Safety and Health Administration (MSHA).1 Metal mines were the smallest mining commodity sector, comprising 1.9% of all mining operations. ? Gold mines comprised 46.8% (n=131) of all metal mining operations. Other common types of metal mines were copper ore (n=34; 12.1%), and iron ore (n=33; 11.8%). Nevada had the largest number of metal mines (n=53; 18.9%), followed by Alaska (n=31; 11.1%).

Sep 1, 2008

By Earl R. Johnson

Ore broken at the mine or quarry face generally is loaded by power shovels into large trucks or rail cars and hauled to a primary crushing plant where it is reduced to a more workable size for ease in handling. The primary crushing plant is customarily located as close as possible to the center of gravity of the ore body and the projected limits of the mine pit to minimize the cost of hauling and to increase safety from flying rock as a result of blasting operations. A belt conveyor is used to transport the crushed product to a nearby ore treatment plant or, should this plant be located some distance away, the ore is loaded directly into cars and hauled by rail. Between trips the crusher product is accumulated in bins or stock piles. In all open pit mining and quarrying operations, the power shovel, the transportation equipment, and the primary crushing plant should work as a team, complementing each other. When establishing the design and selecting the equipment for these closely integrated operations, capital and operating costs for each unit operation must be weighed to achieve an optimum balance. Rising labor costs have given impetus to the universal trend toward greater efficiency, higher speed and larger equipment, and higher degrees of automatic control. The result is that power shovels have increased in size, haulage trucks are larger and faster, and only coarse crushers with feed openings adequate to receive run-of-mine lumps of ore with a minimum of secondary blasting are selected for new installations. These coarse crushers also have large through-put capacities, even when adjusted to produce a 6- to 10-in. size of product, thus making it possible to use a single stage of coarse crushing at the average mine. The use of a single crusher results in a compact crushing plant layout consisting of a dumping pocket for receiving loads of run-of-mine ore, a coarse crusher followed by a surge chamber for the crushed product, and a feeder to withdraw the ore at a uniform rate to deposit it on a belt conveyor. A

Jan 1, 1968

By R. C. Timberlake

In the past three years there has been a great amount of attention given to phosphates world wide, and in particular to the Florida Phosphate Industry. I would like to relate some of the most recent history of the industry and give you a personal outlook for the future. Phosphate rock has been produced in Florida since its discovery on the Peace River in the 1880's. Through 1976, approximately 720 million ST of rock had been mined from Florida reserves, and it is my opinion that there are at least 1.2 billion tons remaining which are consolidated, accessible and can reasonably be expected to be permitted for mining. Over half the 1.2 billion tons will be deeper, more scattered, leaner and will produce lower grade rock than the Bone Valley of Central Florida has tradition-ally produced. In 1973, '74, '75 and '76 the Florida Phosphate Industry produced 32.6, 34.0, 38.2 and (38.0) (P) million ST of phosphate rock respectively. This rock was produced by ten mining companies, Agrico, Borden, Brewster Phosphates, Gardinier, Grace, IMC, Mobil, Occidental, Swift, and USS Agri-Chem; mines are located -17 in Polk County, one in Hillsborough County and two in Hamilton County, Florida. Phosphate rock is used by local companies in Florida primarily to produce phosphoric acid from which DAP and TSP is manufactured. Florida acid producers use about 15 million STPY in acid plants in Florida, and another 7.5 million STPY is consumed by acid producers in plants on and near the Mississippi River. Somewhat

Jan 1, 1977

By H. S. Cannon, F. N. Rhines

IT. H. Hausner( Sylvunia Electric Products Inc., Bay-side, N. Y.)—The results reported by the authors are interesting because they contribute some information on the principles of sintering and also because of a certain practical value for the manufacture of powder . metallurgical parts in production. Pressed powder compacts are frequently sintered in a boat in several layers so that the lower layers are actually sintered under the weight of the upper layers and, therefore, are frequently deformed. The authors gave information on this deformation process by determining the effect of the load on the density. The experimental setup of the authors, however, has a disadvantage—that the sintering occurred in a cylindrical container so that the deformation was stopped in the direction of the diameter. The authors should have rather called this a study of hot-pressing than of sintering. I want to call the attention of the authors and others interested in sintering under load to the experimental work described by Dawihl and Rix.' These authors sintered cylindrical compacts under a lengthwise ten-sional load of 0 to 25 g and found that the shrinkage in length and diameter changes considerably with the load, but that the volume shrinkage is affected very little by the load. H. S. Cannon (authors' reply)—We wish to thank Dr. Hausner for calling attention to the experimental work of Dawihl and Rix. The fact that they found volume shrinkage little affected by varying tensional loads during sintering seems to support the contention that the forces due to loading are equivalent to and additive to the forces which cause densification. This contention is the basis of our comparison of sintering and creep.

Jan 1, 1952

By P Vasconcelos, X D. Deng

Numerous supergene manganese oxide deposits are developed inSouth China as a result of weathering of a thick sequence of Paleozoic marine Mn-bearing sedimentary rocks, consisting mainly of limestones, cherts and black shales that were intensely folded and faulted due to multiple episodes of tectonism since the late Triassic. The ore minerals are dominantly pyrolusite, cryptomelane, nsutite, lithiophorite and braunite. The supergene manganese ores contain Mn ranging from 20 to 44 wt per cent; manganese oxide deposits derived from cherts and black shales also contain recoverable levels of Co, Ni, Cu, Pb and Zn. 40Ar/39Ar dating of potassium-bearing manganese oxides reveals that extensive supergene manganese ore formation started at least in the earliest Miocene and persisted to the Present. Ages of the deposits show a close correlation to tectonic stability, with the oldest in tectonically quiescent areas and the youngest in active areas that have subjected to continuous uplift and thus significant denudation. The prolonged wet and hot climate since Oligocene and the balance between weathering and erosion, which is parameter to the tectonic stability, are the ultimate controls on the formation and distribution of South China supergene manganese oxide deposits. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008