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By Willis I. L, Stevens B. P J, Stroud W. J

The Early Proterozoic metamorphic rocks of the Broken Hill (BH) Block have been recently subdivided into sixteen formations and four groups (Willis et al., 1983b, Stevens et al., 1983). This stratigraphic subdivision has relied upon recognition of distinctive mapped rock units and "associations" of mapped rock units, which characterize particular lithostratigraphic units. The rock units and rock unit associations define local ordered sequences which can be compared and correlated, thereby establishing the stratigraphic succession. In the Clevedale homestead, Thackaringa, BH City, Bores Mine-Freyers mine, Silver King mine, and Brewery Well areas, coherent stratigraphic successions have been interpreted. These areas illustrate the regional variability of the stratigraphic succession and facies changes within individual stratigraphic units. Stratigraphic type sections are located in the Thackaringa, Bores Mine-Freyers mine, Silver King mine, and Brewery Well areas. The principles of stratigraphic interpretation applied in the BH Block can be used in other areas of Willyama Supergroup outcrop such as the Euriowie, Olary and Mount Painter Blocks. The general technique may also have applicability to other highly deformed and metamorphosed terrains.

Jan 1, 1983

By Robert A. Pimentel

Dust is still a major problem in increasing production from longwall faces. Over the last decade, significant improvements have been made in the development of techniques for reducing dust exposure on conventional and continuous sections. But virtually no improvements have been made in dust control on longwall sections. It is true, that there are many more continuous mining sections than longwall sections in the United States and that the number of workers overexposed on continuous miner sections is much larger than the number on longwall sections. However, the problem on continuous miner sections appears much easier to solve and, in fact, we believe that the techniques are available to get virtually all continuous miner sections in compliance. The problems on longwall sections are much more elusive. Also, the number of longwall sections in the United States is expected to increase during the 1980's. Thus, dust control on longwall sections remains a formidable and important problem. Companies operating longwall sections with a dust problem are faced with the tasks of having to quantify the various dust sources, of selecting proper techniques to reduce the problem, of implementing the techniques and of evaluating their effectiveness.

Jan 1, 1983

By Hassell E. Hunter

The Wyoming Mineral-Conoco Crownpoint Project represents the first time that big hole drilling has been exclusively used to develop totally a privately financed mine below a depth of 1000 feet. Three shafts, one ten feet in diameter and two six feet in diameter, were successfully drilled to depths of 2243', 2188' and 2188' respectively and cased with hydrostatic designed steel casing. The largest shaft is to be used to handle muck and water from station excavation and enlargement of the other two shafts. A reverse circulation system with potassium chloride base mud was used for drilling. The mud was cleaned by settling in steel lined tanks with assistance by cyclone type separators. Deviation was monitored by gyroscopic surveying at 30 foot intervals and did not exceed 16 inches off plumb. Casing was designed to withstand hydrostatic pressures with a 1.5 safety factor to the large shaft and 1.25 safety factor for the smaller shafts. All casing welds were x-ray tested prior to lowering the casing in the hole. Cementing the annular space completed the operation. The total time to mobilize, drill and move off the three shafts was 363 days. The drilling operation was completed ahead of schedule and under budget.

Jan 1, 1983

By Michael M. Hamilton

U.S. Bureau of Mines personnel examined mines, prospects, and mineralized areas to determine mineral resources and resource potential in and adjacent to the North fork Smith RARE II study area. Most mineral resources identified in this area are in laterites, highly-weathered residual soil zones. In the RARE II area, resources of nickel, cobalt, chromium, and magnesium were identified at 15 laterite properties and chromium resources at one chromite mine. Other commodities include copper, gold, silver, and mercury (fig. 1). Approximately 1,100 lode and 1,200 placer claims have been located in or adjacent to the area. Most placer claims are for literites. There are no patented claims or mineral leases. Forty laterite deposits on 15 ,properties within the RARE II area (fig. 2) contain about 16 million tons of identified marginal reserves and subeconomic resources containing nickel, cobalt, chromium, an magnesium (table 1). Most deposits have keen explored and are currently claimed. California Nickel Corporation is developing laterites on Gasguet Mountain, within and adjacent to the southeastern and western parts of the study area. If this project proceeds to production, a laterite processing plant on Gasquet Mountain would enhance the minability of other deposits in the study area. The Climax, PFM, DF, and Stone Corral properties (fig. 1, nos. 1, 6, 9, and 23) have deposits of sufficient tonnage and grade to attract mining interest; resources at these properties are in and adjacent to the RARE II area.

Jan 1, 1983

By Thomas Brunsing

The program was carried out to develop deep kerfing and core breaking techniques to be incorporated into the design of a field prototype hard rock mining machine. The field machine is designed to mine non-abrasive bedded deposits up to 20,000 psi in uniaxial compressive strength. The mining technique involves cutting approximately 2 ft deep parallel kerfs spaced 2 ft apart in either a horizontal or vertical direction and subsequently breaking out the cores so defined. The prototype machine is intended for demonstration of the technique in a quarry or equivalent field environment. The program was aimed at minimizing the required kerf width, obtaining reliable breaking within that kerf width and determining cutter blade requirements necessary to achieve a mining rate of 20 ft3/min. Full scale breaking experiments and 1/2 scale kerfing experiments were employed to evaluate the system. High strength concrete test specimens were used to simulate the rock being cut and broken. The test results indicate the kerf/break technique can achieve the desired mining rate by utilizing two 7 ft diam blades to cut 2 in. wide by 24 in. deep kerfs. A lateral load applied at the base of the kerf (base shear) was selected at the core breaking technique to be employed by the full-scale prototype machine.

Jan 1, 1983

By Gonzalo Mato, Colin Godwin, G. Ditson

"The mid-Cretaceous Seagull batholith intruded Mississippian sedimentary and volcanic rocks and Jurassic(?) granitic and ultramafic rocks within the Omineca Crystalline Belt in the Yuk on Territory near the British Columbia boundary. Leucoerotic fluorine- and boron-rich granites of the batholith exhibit many textural variations from aplite to pegmatite, but are dominated by a coarse-grained seriate unit and a fine-grained porphyritic unit.Four distinctive tin vein occurrences within and near the batholith are described, the most interesting of which is the MC showing of quartz-calcite-chlorite-cassiterite veins in intensely fractured zones of sedimentary and volcanic rocks. Three other showings occur within the batholith:J) the EC showing of quartz-fluorite-cassiterite-sulphide veins with prominent muscovite-illite alteration;2) the DU showing of quartz-hematite-fluorite-sulphide- sulphide-cassiterite with considerable manganese staining and sericitic alteration; and3) the VAL showing of quartz-tourmaline-cassiterite-fluorite-arsenopyrite veins with little associated alteration.Most cassiterite occurrences are within easterly-trending, vertical structures and all occurrences are thought to represent parts of a single system. These mineralogical and physical variations are apparently related to the distance from the upper contact of the batholith.For the Seagull batholith, Rb-Sr isotopic data give a 100±1.4 Ma isochron age that is concordant with the K-Ar model age from biotite of 101±4 Ma. Initial Sr isotopic ratios for the batholith are high at 0.712, indicating an old, sialic crustal source for this pluton. This initial ratio is similar to values for granitic rocks associated with tungsten deposits in the Yukon Territory. The high initial ratio for Sr, the high Si02 content, the high s/I index, the presence of normative corundum. leucogranitic composition and associated lithophile-tungsten mineralization demonstrate that the Seagull batholith is probably an S-type granitic body. This factor is significant to regional exploration jar tin and tungsten in the Canadian Cordillera."

Jan 1, 1983

By K. A. Natarajan

The relative significance of corrosive and erosive wear in magnetic taconite grinding is examined. The influence of different types of aeration, namely, nitrogen, air and oxygen on ball war was established for mild steel and high carbon low alloy steel balls. Ball wear data from dry and wet grinding tests are compared with those obtained in the presence of an organic solvent that does not promote electrochemical corrosion. 'Marked ball grinding, tests along with electrochemical measurements involving ball material and magnetite electrodes indicate that contribution from oxygen towards wear (corrosive wear) is relatively small and abrasive wear appears to be significant. Rheological properties of the slurry-appear to have an important bearing on the abrasive wear of grinding balls.

Jan 1, 1983

By Klaus Stoss, Bernd Braun

The sinking and lining of a large mine shaft with 8.0 m i.d. and 1,133 m total depth is described in detail. The ground freezing method was applied to safely sink the shaft through unstable, waterbearing strata. Following a brief introduction to the geological and hydrological conditions and the owner's shaft requirements, is the general technical concept to sink and line the shaft. Particular emphasis is put on the lining system which has to provide stability and absolute watertightness for the lifetime of the shaft, even though mining takes place in its immediate proximity. Machinery and equipment used to execute the work are mentioned and commented. Furthermore, the excavation and lining of the large filling stations using rock anchors and shotcrete are described. Details on performance rates are given.

Jan 1, 1983

While international coal trading operations often involve relatively small contract quantities, delivered over short periods or even in single shipments, most coal is supplied under long term arrangements. In entering into these arrangements the customer needs to be assured that coal of suitable and consistent quality can be supplied for their duration in the volume required. A detailed knowledge of the mine and transport system is required and must be presented from the customer's perspective.

Jan 1, 1983

By John B. Goddard, David R. Brosnahan

Leaching of uranium in situ from sandstone deposits with ammonium carbonate solution containing dissolved oxygen occurs rapidly compared with the leaching of the bulk of the sulfur present as FeS2. However, because of their high reducing capacity and their relative abundance, the FeS2 minerals consume the bulk of the oxidant. A pressure leach apparatus was constructed that permitted measuring oxygen consumption by FeS2, best described by a first-order reaction. The experimental rate constants for various cores are roughly proportional to their FeS2 contents.

Jan 1, 1983

By M. F. Dunn

During a mine fire or other emergency, it may be desirable to reverse the airflow in order to provide an escapeway or to isolate a fire. Also, in colder areas, the airflow may be reversed to prevent ice buildup. When reversing main mine fans, the mine operator usually does not know what operating characteristics of flow and pressure to expect. Laboratory and field tests of vane axial main mine fans in the 7- to 9-ft diameter size range were conducted to establish forward and reverse performance characteristics under controlled conditions and at typical mine installations. The data obtained suggest that reverse performance characteristics are dependent upon the blade angle and the hub to tip ratio. There is also evidence that reverse performance can be predicted for a family of blade angles and a given hub to tip ratio. Generally, quantity of air is 30 to 65% less in reverse than when operating in the normal forward mode.

Jan 1, 1983

By E. Topuz, G. Faulkner, M. Karmis, C. Haycocks

The Appalachian coal region of Virginia, southern West Virginia and Kentucky and the extreme eastern portion of Tennessee constitutes a unique area of surface coal mining activities. The area contains a number of contiguously placed coal seams, up to a total of fourteen in some places, which vary in thickness from a few centimeters to 2,5 meters. Much of this coal is of high quality, some being the highest grade metallurgical coal found anywhere in the world. The region may be broadly characterized physiologically as a dissected plateau with a relief above the valley floors of up to 500 meters and a dendritic drainage pattern. Up to six seams may outcrop in the hillsides above drainage, many of which have been subjected to contour stripping operations. Prior to the passage of the surface mining reclamation act, little effort was made to reclaim stripped areas. The passage of the strip mining act, including the controversial requirement for returning the land to its approximate original contour, has forced intensive recla¬mation efforts from the mining industry. The wisdom of this original contour requirement has been the subject of considerable debate and litigation, mainly because of its cost, inconvenience, and value of the land after it has been reclaimed. Regardless of whether recla¬mation is carried out, under current practices slope failures do occur. This in effect circumvents the intent of the law and can expose large unvegetated spoil areas, and contribute to hillside erosion and stream silting. Such failures must be eliminated if further costly reclamation efforts are to be avoided.

Jan 1, 1983

By David H. Y. Tang, Syd S. Peng

In general, the strata sequence of the immediate roof in the under- ground coal mine openings can be divided into three types. They are: (A) each stratum deflects independently, (B) some stratum (or strata) loads on the underlying stratum, and (C) each stratum loads on its underlying stratum. The flexural behavior of the immediate roof which is made up of multiple strata not only depends on the material property, geometry, and external loading of rock strata, but also on the strata sequence. A computer program based on the beam-column theory is written for determining the bending stress and deflection for the generalized immediate roof. The flexural behavior of the immediate roof in various strata sequences are investigated for the following effects: roof span, horizontal stress, thickness and Young's modulus of the lowest stratum. In addition, some of the results are compared with the results of the finite element method.

Jan 1, 1983

By J. C. Draper

The Duquesne Light Company and GAI Consultants, Inc. conducted a demonstration program aimed at establishing permanent vegetative cover directly on acidic, deep coal mine refuse. Several plots were treated with formulas varying in soil amendment application rates and plant species. Periodic monitoring of refuse chemistry has indicated when maintenance applications of seed and soil amendments were required. To establish drainage control, the site had to be regraded. The most successful formula was applied to the entire site. Specific treatment for acidic spots has been initiated. Results of the program indicate that adequate permanent vegetation has been established.

Jan 1, 1983

By W. R. Boehme

The test work was done in two parts. In Part I, five 6 x 16 mesh activated coconut shell carbon samples made by four different manufacturers were evaluated as to their gold loading rate and total gold loading. The five carbon samples tested are not identified by manufacturer and are simply designated as Types A through E. Then from the carbons tested, a suitable highly active carbon was selected for subsequent studies on impurity effects upon loading, Part II. Test Procedures The procedures and tests descriptions are given for the ultimate gold carbon loading tests and the dynamic gold carbon loading tests.

Jan 1, 1983

By David K. Denton

There are no active mines in the Mt. Eddy RARE II area. Chromite, gold, and stone prospects were examined. The RARE II area contains no identified mineral resources; however, a sample of a 260 ton occurrence contained 38.1 percent chromium oxide (Cr203) at the Ratero Prospect (fig. 1, no. 3), which has low potential for chromium resources. The Johnson Mine (fig. 1, no. 6) produced a small unrecorded amount of chromite during World War IT, but only a low potential exists for chromium resources. A low potential exists for gold resources at the Half Century Prospect (fig. 1, no. 2). At a borrow pit northwest of the study area (fig. 1, no. 1), sheared serpentinite is quarried for road metal; similar rock occurs in the RARE II area, but better material is more readily available elsewhere. Sand and gravel occurrences are too inaccessible and distant from markets to be considered resources. Mineral fuels and geothermal resources were not evaluated during this Bureau of Mines study. There currently are three unpatented lode mining claims in the study area. INTRODUCTION The Mt. Eddy RARE II area is 7 air-mi west of Mt. Shasta City, California, and straddles the Siskiyou-Trinity county line. The roadless area includes 7,200 acres of rugged, glacially carved, ridges and drainages which comprise Mt. Eddy. Elevations vary from 6,000 ft along the North Fork Sacramento River to 9,025 ft at the summit of Mt. Eddy. The area is covered with conifer forest below 8,000 ft elevation.

Jan 1, 1983

By L. L. Oriard

In order to predict the influence of blasting on slopes, one must first understand the action of explosives, the manner in which rock is broken or displaced, and how seismic waves are transmitted, and the nature of these seismic waves. In this paper, the author describes the action of high explosives on rock masses, beginning at the source of the explosion, extending through the zone of rupture to a distance where only elastic waves of low energy persist. The paper describes the relationships between explosives charge quantities and distances, including the character and intensity of the seismic waves in various types of terrain. In looking at the analysis of slopes subjected to seismic waves, it has been common practice to assume a simplified model in which the anticipated acceleration is applied horizontally to the slope as an equivalent static force, or a model in which there is a rigid base subjected to mechanical shaking. Such models do not accurately portray blasting activity taking place within or near the slope in question. In dealing with blasting effects, it is important to under- stand seismic wave types, wave lengths, attenuation and transmission paths, as well as vibration intensity. In most cases, those slopes that are the least stable under static loading will also be the least stable under dynamic loading, although there may be rare exceptions. Thus, the more that is known about a slope statically, the better will be the assessment of it dynamically.

Jan 1, 1983

Fig. 4 and 5 of the paper 'The analysis of ventilation and cooling requirements for mines' by J. van der WaIt, E. M. de Kock, and L. K. Smith are positioned incorrectly in the February issue (J.B. Afr. Inst. Min. Metal., vol. 83, no. 2, Feb. 1983). Extractive metallurgy of zinc At a professional development seminar to be held in Montreal (Canada) from 18th to 22nd April, 1983, specialists from industry and university will discuss the extractive metallurgy of zinc from ore to finished metal with special emphasis on the theory and practice of modern technology.

Jan 1, 1983

By Andrew Button

INTRODUCTION This review deals with the controls exerted by unconformities on the stratigraphic and areal distribution of gold (and uranium) in Precambrian conglomerates. The relations described are drawn mainly from Precambrian basins in southern Africa, particularly the Witwatersrand Basin. The mining industry of South Africa started in earnest with the discovery of diamonds in 1866. Gold was first discovered in 1870, and in March of 1886, two out-of-luck prospectors stumbled across what was to become the world's greatest goldfield, in the vicinity of Johannesburg. George Harrison and George Walker sold their claims for a pittance and were heard of no more. The Witwatersrand goldfield has been in continuous operation since that time, some 150 mines having operated at one time or another. Deep mining technology developed here has allowed operations to proceed to depths approaching 13,000 feet. The Witwatersrand has produced some 55% of all the gold ever mined, and currently produces 60% of the world's supply, some 650,000 kg Au per year. To 1971, the Witwatersrand had produced some $32 billion of gold and $2 billion of uranium (when average prices were less than $35/oz. for Au and $10/lb. for U308). At present prices, the annual Witwatersrand production of close to 700,000 kg would be worth about $10 billion. Uranium was discovered in the Witwatersrand in 1923. In the $15-30/lb. bracket, the basin contains a reasonably assured plus

Jan 1, 1983

By Whiten W. J

An investigation on the breakage characteristics of closely sized orc samples at different levels of input energy was carried out to determine an appearance function for possible use in ball mill modelling. A consistent pattern of breakage behaviour was observed and the resultant size distributions could be described by a one-parameter, ('t'), family of curves. For each particle size range tested, this parameter 't' has an exponential relationship with input energy below an upper energy limit. A tentative linear relationship between the input energy at a constant value of 't' and the work-index leads to reconstruction of 'I' - input-energy curves from the work-index values. To normalise the efrect of particle size and input energy, multidimensional cubic spline regression was performed on thc entire range of data. The results indicated that the parameter 't' can be determined, reasonably accurately, as a function of Ln (input energy, kWh/tonne) and Ln (particle size, mm) for input energies between 0.5 and 8.0 kWh/tonne.

Jan 1, 1983