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Chromite ores have a long history of low pricing and for AustraliaÆs only chromite mine this has been a particularly tough challenge, especially as the mine is located nearly 400 km from the nearest port at Port Hedland. A stockpile of chromite fines (-16 mm) has been built up since 2003. The opportunity to develop a facility to treat this material to produce a chip (-16 + 1 mm) product and a sands (-1 mm + 45 micron) product was taken when the price increased to above US$140/t. A simple add-on plant containing a heavy media cyclone circuit for the chips and a spiral circuit for the sands was designed and developed. During construction of the fines plant the price of chromite reached a level where the payback for the entire project was less than eight weeks. Soon afterwards the price and the demand for chromite plummeted and the site was put on care and maintenance, except for the commissioning of the fines plant. This put considerable pressure on whether to continue to operate the plant or to place it in care and maintenance. Times of boom and bust provide management with almost totally opposite views. By not taking a conservative view on prices and costs, the effect of extremely low prices and minimal demand can be devastating to a good project. Designing and building plants with conservative costings in boom times gives a greater chance of keeping projects alive during the bust periods that tend to follow.

Jan 1, 2009

By Tarvainen M, Mattila O

Outokumpu Oy has systematically developed the automation of mineral flotation covering the technology of both new devices and control methods, and as a practical result of this effort currently produces two on-stream X-ray analyzers. The Courier 300 system basing on conven- tional X-ray technology is applied to complex or large processes. The newer Minexan 202 dis- tributed probe system based on radioisotope technology is developed mainly for simple or small scale applications. In this paper aspects and experiences of these analyzer systems and their applications for flotation control are discussed with particular reference to the role of the computer

Jan 1, 1977

Regions with extensive reserves of brown coal but with inadequate deposits of hard coal provide a particularly suitable field for the application of brown coal petrology.In fact, this discipline is indispensable where brown coal is to form the basis for high-quality products of upgrading. Both chemical and physical analyses are required in addition to the techniques employed in coal petrology, but it is the macropetrographic and the microscopic investigations that are of decisive and specific importance.Foremost among the methods of upgrading brown coal is briquetting. From the raw materials aspect the biochemical rank of coal (i.e. the type of deposit) and the coal variety (i.e. the lithotype) exert a marked influence on briquette strength. These are also the significant factors in the suitability of a brown coal for high temperature carbonization; here the demands on coal quality are even more exacting if adequately sintered and therefore high-strength lump chars are to be obtained. The principle applies also to the char from low temperature carbonization. There are close relationships between the tar yield and the remission of the coal.The reflectivity measurement therefore provides a rapid method for evaluating the suitability of a brown coal for low temperature carbonization. Similar correlations have been established between the content of extraction bitumen (raw montan wax) and the remission. Petrological investigations show that the quality of the coal bitumen is a function of the type of deposit and of the lithotype.

Jan 1, 1968

By Abdulhadi H. M, Soliman S. A

The Western Desert of Egypt is a part of the arid Great Sahara of Africa which extends from the Nile Valley in the east to the Atlantic Ocean in the west. It is covered by a sedimentary sequence of Mezozoic and Teriary rocks. Recently this part of the country (about 65% of its surface area) has attracted an increasing attention in the plan of finding new agricultural and industrial communities outside the crowded Nile Valley. The plan aims to reduce the high population density in the narrow Nile Valley and to cover a considerable part of the increasing food demands in the country of Egypt. Accordingly, the groundwater exploration work in the Western Desert has been remarkably increased in the last decade, however it is still limited compared with the vast area of the Desert. The present work is a part of the groundwater exploration in the 6th October City, a new community located at 40kms west of Cairo. The rock exposures belong to a sedimentary stratigraphic section starting from the Cretaceous in the east to the Pliocene in the west. The Cretaceous outcrops due east are attributed to an almost N-S uplift and forms a thick massive limestone plateau which separates the present area from the Nile Valley. The Teriary section in the west have alternations of different porous formations such as the sands and sandstones which may acquire a good potentiality of groundwater resources. The previous groundwater exploration work included combined geological and geophysical investigations followed by exploration drilling. Although the area lies directly to the west of the Nile Valley, the discovered groundwater is saline and located at deeper reserviores compared with the groundwater in the Nile Valley. This groundwater was described as marine fossile water by the oil companies working in the Western Desert. From the geological point of view, it is believed that the Cretacious massive limestone plateau, in the east, roots to a depth which far exceeds the groundwater levels in the Nile Valley and acts as an impervious barrier between the aquifers in the Nile Valley and the area under investigations.

Jan 1, 1988

By G McKay, M Erskine, S Macklin

The City of Sydney is currently investing in a number of infrastructure projects that require tunnel excavations within the Triassic Hawkesbury Sandstone. It is generally accepted that this formation has high residual stresses of ‘tectonic’ origin, so much so that these stresses have been implicated in a number of well-known failures and problems for tunnelling. These include failure of ‘roof beams’ comprising discrete beds in the crown of tunnel excavations; stress-induced spalling and ‘slabbing’ of tunnel walls; shear displacement between beds causing the failure of rock bolts; strain in adjacent infrastructure and, the necessity for re-grouting of high conductivity fractures due to stress relief dilation after excavation. Whilst there is an extensive published database of in situ stress measurements comprising ‘hydrofrac’, ‘over-coring’ and ‘slotter’ stress measurements, these data indicate a considerable spread of results. The traditional approach to interpreting this data has been to attempt to fit linear correlations to stress versus depth data, based on personal experience and ‘back-analysis’ of monitoring data during construction. However, there are a number of such correlations in the literature and there is divergence of opinion regarding the assessment of ‘background’ in situ stress and appropriate upper and lower bound values for design. This paper provides a brief review of the published data; suggestions on an alternative ‘risk-based approach’ to assigning in situ stresses for design; and, proposals on how in situ stress tests may be conducted in future to improve the quality of the database available to designers.CITATION:Macklin, S, McKay, G and Erskine, M, 2014. A review of the in situ stress database for tunnel design in the Hawkesbury Sandstone, Sydney, New South Wales, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 171–178 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Liu Y

Mathematical modelling of scrubbers in development and longwall operations in underground mines produces useful results. Mathematical modelling on the mounting of scrubbers on longwall supports shows that the number of scrubbers and the air quantity through the scrubber are the two important parameters. Increase in both these parameters results in decrease in dust levels at the tail gate. The critical factors are scrubber efficiency and the ratio of the air through the scrubber/total air quantity.Results of parametric studies conducted to establish factors which have dominant influence on the effectiveness of the scrubbers on dust levels and high gas build-up in the scrubber show that for use of scrubbers in development headings, the order of importance of parameters in relation to dust concentration in the scrubber area is: scrubber efficiency, rate of production, specific dust make/tonne, leakage factor, intake dust concentration, recirculation factor and air quantity through the scrubber.The equations developed for mathematical analysis and the detailed results of modelling provide useful data on recirculation of emitted gas in the use ofscrubbers for dust control.

Jan 1, 1995

By R Dimitrakopoulos

Optimisation and mathematical formulations for open pit design and long-term production scheduling have been available since the 1960s. There are two main concerns in the application of existing mixed integer programming (MIP) models in open pit mines: a. the feasibility of generating both optimal solutions and practically mineable scheduling patterns and b. the inability to deal with in situ variability in orebodies and account for uncertainty. In dealing with these issues, a general open pit production scheduling method for multi-element deposits is presented and subsequently used to optimise the long-term production schedule in a nickel laterite deposit. The application shows the weaknesses of MIP formulations in terms of generating optimal solutions as well as practically feasible mining patterns. The application of the same formulation in the presence of in situ orebody variability and uncertainty uncovers a major reason for deviations of scheduled production from actual production, and outlines additional limits of traditional optimisation formulations as well as future needs.

Jan 1, 2003

By C Zschiesche, alam, A Abadias Llamas, A K

An integrated experimental and thermodynamic modelling study of the phase equilibria in the FeOFeO1.5- SbO1.5-SiO2 system in equilibrium with liquid Sb and Sb-Ag metal has been undertaken to develop thermodynamic model of the Na-Si-Fe-O slag system with S-Sn-Sb-Pb-As minor elements based on the experimental investigation of the selected sub-systems. New experimental phase equilibria data at 575–1600°C were obtained for this system using high-temperature equilibration of synthetic mixtures with predetermined compositions in sealed silica ampoules, Fe3O4 basket in sealed silica ampoule, or Re foils, a rapid quenching technique, and electron probe X-ray microanalysis of the equilibrated phase compositions. Experimental results on phase equilibria in the Fe-Sb-Si-O+Sb metal system obtained helped to produce initial set of model parameters in the slag. The primary phase fields of quartz/tridymite/cristobalite (SiO2), 2 high-SiO2 immiscible liquids, olivine (Fe2SiO4), wustite (FeO1+x), spinel (Fe3O4), schafarzikite (FeSb2O4) and valentinite/ senarmontite (Sb2O3) were identified in the binary Sb2O3-FeO, Sb2O3-SiO2 and ternary FeO-Sb2O3- SiO2 systems. Further refinement, particularly the distribution of excess Gibbs energy among the ‘FeO’-Sb2O3-SiO2 and ‘FeO1.5’-Sb2O3-SiO2 interactions, required the study at more oxidising conditions. Oxygen potential was increased using an inert metal (Ag) rather than using the gas flow due to the high volatility of Sb-containing gaseous species. Liquid Ag-Sb alloys with low concentrations of Sb of a few percent were used. At these conditions, the concentration of AgO0.5 in slag was below 1 mol per cent, which had a small effect on observed phase equilibria in the system. In addition, important information on the solubility of silver in slags is produced, which can be valuable when treating electronic recycling materials or primary silver-containing ores through the Pb process. Two main areas were addressed: the spinel-tridymite boundary (40–70 per cent SiO2 in slag) and spinel liquidus near 15 per cent SiO2 in slag. This allowed to deconvolute the separate contributions of the FeO-Sb2O3(-SiO2) and Fe2O3-Sb2O3(-SiO2) systems.

Jun 17, 2024

The brown coal deposits of the Latrobe Valley are ideal for open cut mining and this method has been used since the start of coal winning in 1894. Operations at the main Yall9urn open cut commenced in 1922, but after a few years the main excavators were replaced by German continuous excavators and subsequent developments of Yallourn and the newer Morwell open cut have been based on this type of plant. The reasons for preferring continuous to intermittent excavators in the Latrobe Valley are indicated in this paper.Under the pressure of post-war conditions, and from their long experience and ability, German engineers have recently made substantial improvements in their continuous excavators and these developments have been enhanced by some American innovations. These changes have extended the economic limits of open cut mining and also serve to emphasize the close inter-relation between the nature of coal and overburden deposits, excavator design and methods of operation.As an aid to descriRing recent excavator developments, this interdependence is demonstrated by means of diagrams which show typical methods of operations, together with examples of actual machines using these methods. The types of excavator dealt with are mainly those in use at, or destined for Yallourn or Morwell open cuts, together with additional types used in U.S.A. and Western Europe. For completeness, and also because they will continue in service at Yallourn and Morwell for some years, rail-mounted dredgers have been included in this paper even though in Europe they are now regarded as obsolescent.Explanations are given of how the intrinsic qualities of Latrobe Valley brown coal and overburden have sometimes prevented overseas plants from operating with the full efficiencies and/or in the methods visualized by the manufacturer, and references are made to the modifications and investigations being undertaken to overcome these problems.A compresensive bibliography is given. Dates shown on illustrations are not commissioning dates of the plant concerned, but the year when photographed.

Jan 1, 1960

By T Sparks

The Collie River catchment, located approximately 200 km south of Perth, covers an area of around 2830 km2 and is the source of run-off to the Wellington Dam, an important irrigation water resource for the Collie Irrigation District. The salinity of the Wellington Dam has increased due to historical clearing and irrigators currently use water with salinity levels approximately twice that of the Murray River in South Australia (Water and Rivers Commission, 2001). The Collie River Salinity Situation Statement (2001), released by the Water and Rivers Commission (now the Department of Water), identified realistic actions that could achieve the salinity reduction target. Subsequent benefit-cost analyses and prefeasibility studies recommended the diversion of the most saline flows in the Collie River away from the dam as an immediate intervention (URS, 2003). The East Branch of the Collie River above the locality of Buckingham (20 km east of Collie) contributes around half of the salt that flows into the Wellington Dam and the diversion and storage of the saltiest flows from the East Branch at Buckingham was identified as a viable option for reducing salinity in Wellington Dam. The proposal had one problem û the water could not be disposed of as quickly as it was diverted. However, in the vicinity of the diversion site were a number of coal mine voids and after preliminary discussions, the Government/Griffin Coal alliance was formed and from this the opportunities have continued. Diverted water would be stored temporarily in an adjacent mine void (Chicken Creek 4 void) and then disposed of to the sea. The disposal options included Western Power CorporationÆs saline discharge pipeline from Collie Power Station, or a new pipeline. The diverted water was also identified as a potential raw source for treatment and use in industry. This has opened up opportunities including desalination, water efficiencies in the power stations, increased reliability of water supply for the power stations, water for new industries, wastewater disposal options and extra water for PerthÆs water supply. In the process of solving the water storage problems the project introduced a range of mine water quality problems û heavy metals and pH û and the Department of Water (DoW) is now working with the mining industry and the Centre for Sustainable Mine Lakes (CSML) to develop treatment and management technologies. The project has received support and funding through the National Action Plan for Salinity and Water Quality (NAP) and it has been possible to accelerate and enhance this project as a result of NAP. The DoW has developed the proposal to an advanced stage and gained approvals for the capital diversion program to go ahead. The partnerships have expanded to include the second mining company, Premier Coal, the Water Corporation, Western Power and the Harvey Irrigation Cooperative. The proposal could feasibly result in a $90 million integrated water management initiative for Collie using the latest technology, mining operations and providing water for value adding industries in the local area. The DoW is not a mining company; however, our experience in managing water in times of shortage, environmental water quality criteria, competition for water and managing community expectations will have the same success factors:consultation and knowing your community and stakeholders, sharing issues and working in partnership can provide results far greater than the initial issue, even brackish water has value, every sector is in competition with each other and has to have a share of the water, an integrated approach can provide opportunities for development in areas of water shortage, and never think of water as wastewater.

Jan 1, 2006

Gold mineralization belt of eastern China in the adjacent part of the northwestern Pacific rim is orientated NE to NNE and as-sociated with Mesozoic faults and igneous intrusives and Mesozoic to Cenozoic volcanism and subvolcanism extending more than 3000 km in length and 300 to 800 kni in width affected by the movement from the Pacific Plate subducted against the Asian Plate.The relative movement between the Pacific and the Asian plates give rise to two types of fracture zones, the tensional ones providing the space for the formation of fissure-filling type of auriferous quartz veins and the shear zones providing the space for the formation of hydrothermal replacement type of gold de-posits in Shandong Peninsula. The fissure filling type of quartz vein, is represented by Linglong gold deposit which is hosted in Mesozoic Linglong Granite and consists of hundreds of quartz veins filling fractures trending NE to NNE and the hydrothermal replacement type is represented by Sanshandao gold deposit which is hosted in crushed and hydrothermally altered Mesozoic Linglong Granite in contact with Archaean metamorphic complex of Jiaodong Group along a Mesozoic upthust fault zone trending NE.

Jan 1, 1990

By Seymour K. M, Sampson D. B, Walker I. W

Ashton Mining Limited is the operator of two wholly-owned gold mine/mill complexes at Laverton and Leonora. In addition, Ashton owns 43% of the Bardoc Joint Venture mine/mill complex, which is operated by Aberfoyle Pty Limited. All three of these operations are located in the Eastern Goldfields region of Western Australia (Figure 1). At Laverton, milling capacity is in the order of 1 million tonnes per year in 3 mills (Duketon 200,000 tpa, Cork Tree Well 650,000 tpa and Craiggiemore 150,000 tpa). These mills service a distance of 80 km, from Baneygo in the north to Craiggiemore in the south. Mineral tenements cover a 150 km long stretch of a series of sub-parallel mineralised structures. At Leonora, the Harbour Lights mill is designed to treat 750,000 tpa of sulphide ore, and has treated oxide ores at an annualised rate of over 1 million tonnes/year. The mill is supported by several tenement blocks that lie within a 50 km trucking radius of the mill. The most important of these is the Mertondale tenement block, which covers approximately 25km of the Mertondale Shear Zone.

Jan 1, 1991

Standards in the public reporting of resources and reserves in Australia have dramatically improved since the implementation of the Australasian Code for Reporting of Mineral Resources and Ore Reserves (The JORC Code) in 1989. Whilst the JORC Code states clearly that Mineral Resources and Ore Reserves are imprecise calculations and should be treated as estimates, there is strong evidence that many people regard them as fact, including some accountants, directors, auditors and investors. Mineral Resources and Ore Reserves are key inputs in the valuation of a mining company and the determination of financial performance. Geological knowledge is the foundation upon which Mineral Resources, Ore Reserves and investment decisions are made, however this information carries with it substantial uncertainty. Case studies and company reports have established that errors derived from inadequate geological inputs have led to reduced profitability in operating mines and in extreme cases the premature closure of mine operations. Whilst there are many causes of mine closure and reduced profitability, including commodity prices and exchange rates, the cumulative effect of all geological uncertainty contributes significantly to the erosion of the credibility of mining within the investment community. There are a number of methods used to characterise and model uncertainty in Mineral Resource and Ore Reserve estimation. Empirical mining indexes, sensitivity analyses, Monte Carlo simulations and Conditional simulations are used to identify and estimate geological uncertainty, notably the quantification of uncertainty in grade and tonnage estimates. These techniques have not generally been applied to estimating geological uncertainty associated with key Ore Reserve inputs such as appropriate mining technique, equipment selection, production rate, mining dilution, stability requirements, materials handling, metallurgical processing, product quality and waste storage. New software tools are needed to model the entire mining process with all its geological and other interdependencies, enabling all uncertainties to be separately identified and estimated. By its very nature, mining involves the assumption of significant technical, financial, political, environmental and social risk. Success comes by understanding and managing these risks and consequently the mining industry will never choose to reduce the level of geological uncertainty to nil. The ultimate aim of improved identification and estimation of geological uncertainty is to quantify inputs into the Ore Reserve process, allowing a company to assess the risks and manage these accordingly. This approach is relevant to feasibility studies for new projects as well as life-of-mine planning through to the weekly schedule at existing mines.

Jan 1, 2003

By A Fowler

The unpredictability of the location, grade and width of narrow-vein deposits presents difficulties for mine geologists and engineers attempting to estimate, schedule, forecast and mine their deposit profitably. This unpredictability stems not only from the grade distribution within a vein, but also the irregularity of vein geometry in three-dimensional (3D) space. Traditional deterministic methods of modelling vein geometry do not account for the inherent variability of the veins, resulting in significant errors when using limited drill hole information. This paper presents a probabilistic method of modelling narrow-vein deposits using sequential gaussian simulation (SGS), which can quantify this variability and improve production forecasts. Vein geometry, thickness and grade are simulated to provide a number of different equi-probable realisations that each honour the drill hole and face sample input statistics. An example is presented from the Augusta narrow-vein Au-Sb mine in central Victoria, where the simulation results are validated against the input data and survey pick-ups of the veins along ore drives.

Aug 22, 2011

A variety of rockbolt designs and resin anchors are currently in use in underground mines. This paper identifies possible risk factors that may affect the intended performance of rockbolts. The paper also presents the outcome of a study on the variability of some aspects of fully encapsulated rockbolts undertaken across seven coal mines within the context of previous research findings on rockbolt anchorage performance.

Jan 1, 2003

Delhi Australian Petroleum Ltd., acting as operator for the joint interests of Delhi and Santos Ltd., has been engaged in petroleum exploration in the western Great Artesian Basin since 1958.Extensive airborne magnetometer, gravity meter, reflection and refraction seisomograph, and surface geological surveys have been carried out. Results of the surveys have considerably altered the concepts of the geology of the area.Seven exploratory wells have been drilled in the area. Results of the drilling have established the presence in the subsurface of previously unknown Paleozoic sediments which are capable of generating hydrocarbons.Production of oil or gas has not been achieved, but each phase of the exploration programme has resulted in progressively establishing the basic conditions necessary for the discovery of commercially profitable accumulations.INTRODUCTIONDelhi Australian Petroleum Ltd. commenced operations in Australia in 1958. They have subsequently been engaged in systematic exploration for oil and gas, acting as operator for their partner, Santos Limited. The methods and techniques employed are those used throughout the petroleum industry. The results of the exploration programme contribute to a better understanding of the basic geology, and concomitantly a firmer analysis of the petroleum producing potential, of the western Great Artesian Basin.Each phase has progressively enhanced the gross geological interpretation of the area with regard to favourable conditions for the generation and accumulation of hydrocarbons, but the stage has not been reached where productive potential is definitely established.Exploration status in 1958Basin configurationIn 1958 knowledge of the pre-Jurassic stratigraphy of the geographically defined western Great Artesian Basin...

Jan 1, 1964

By Z S Chang, T F. Zhou, G X. Zhong

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. The Yaojialing zinc-gold polymetallic deposit is a newly discovered, large skarn deposit in the Middle-Lower Yangtze metallogenic belt, East China. It is located in the transitional zone between the Tongling uplift block and the Fanchang faulted basin. It is mainly hosted in the contact zone between early Cretaceous granodiorite porphyry and Carboniferous-Triassic limestone, or occurs in limestone xenoliths within the intrusion. Skarn and stratabound massive sulfide orebodies are the primary ore styles. Sulfide ?34SV-CDT values indicate a magmatic sulfur source, in common with most deposits in the Tongling block. Calcite d13CV-PDB and d18OV-SMOW ratios reveal that marine carbonates were the major source of carbon in late-stage hydrothermal fluids. The calcite probably formed during interaction between magmatic fluids and carbonate wall rock.CITATION:Zhong, G X, Zhou, T F and Chang, Z S, 2015. Geology, chronology and isotope geochemistry of the Yaojialing zinc-gold deposit, Tongling ore district, Anhui Province, China, in Proceedings PACRIM 2015 Congress, pp 457–462 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

Rare-earth permanent magnetic roll separators, pioneered by our group a few years ago, have distinctly different operation characteristics compared to prior art electromagnetic separators of various types. Many new applications for dry high-intensity (or better: high-force) magnetic separation have been developed in a short time period. It has also been found that the new generation of separators generally are more efficient with regards to removal of weakly magnetic contaminants in glass and ceramic raw materials with minimum loss of valuable product compared to induced magnetic roll (lMR) separators. The latest development is in the area of production of clean magnetic concentrates at high recoveries. It is likely that the PERMROLLR magnetic separator will replace cross-belt and lift-type magnetic separators as a result of this most recent advance.   The paper will review the features of the PERMROLLR magnetic separator in comparison with other types of magnetic separators on the market and give examples on applications.

Jan 1, 1990

By Tumilty JA, Schmidt CG

Sulphide ion is a powerful poison in gold cyanidation, however, the detrimental effect is less severe in plant practice. This is thought to be due to the presence of depassivating elements in the ore, mainly lead. Trace amounts of lead can counteract the poisonous effect of considerable amounts of sulphide. The reaction is instantaneous and is likely to be a direct involvement in the electrochemical surface reaction. Lead addition cannot be regarded as an all-round cure when experiencing poor leach efficiencies. A possible beneficial effect depends on the mineralogy of the ore and has to be determined individually for every material.

Jan 1, 1989

Some major mineral deposits in northern Australia are found in preconsolidation slump disturbances in the sediments.In the retransported marine sediments at Tennant Creek, breccia beds and disturbances are found which have localized later mineral deposits such as the Peko copper orebody. These disturbances are thought to result from slumping, turbidity flow and various types of "semi-fluidized" subaqueous slides intermediate between slumps and turbidity currents.Movements are found to ~ause widespread disturbances in the sediments such that subsequent mineralization can spread through a large volume of rock giving rise to orebodies greater than those localized by tectonic structures.A similarity is noted between the sedimentary disturbances at Tennant. Creek and those at Mount Isa and Mary Kathleerr. It is suggested that disturbed beds which are host rocks to ore minerals in these mines may also be due to movements of the sediments before compaction.Certain characteristics of the slumped rocks can be recognized and limited generalizations can be made about the shape, extent and habit of these host rocks and the orebodies they contain.INTRODUCTIONSubmarine slumping and· turbidity current retransport are almost entirely responsible for some types of deep marine sediments.However, little attention has yet been drawn to slump deposits and associated disturbances bedded in the sediments as features localizing later mineralization.A study. has been made by the writer of the slump and associated phenomena of the ,Tennant Creek field where many mineralized bodies, including some gold and copper orebodies, occur as replacements of coarse fragmental slump...

Jan 1, 1960