Search

The first section of this paper identifies and characterises the key water-related issues at wet and dry mine sites. Dry-climate case histories include a desert mine in Southern California where water recycle is maximised, and other non-traditional water supply sources are considered. Wet-climate case histories include a mine in Northern California where waste rock and tailings leachate as well as poor-quality pit water have required comprehensive water management both during operations and after closure, and a grass-roots mine development proposed in South America, where the potential water quality issues were partly responsible for altering the overall mine design. Complex geochemical and hydrogeological issues that have been dealt with at these mines include the generation of poor-quality water in the pits after closure; groundwater quality changes imprinted on naturally poor-quality groundwater; and generation of poor-quality leachate in the various types of waste rock, even where acidic conditions do not occur. The final part of the paper describes typical approaches to characterising and resolving key water and geochemical issues at dry and wet mines. Solutions are discussed and supported by the lessons learned from the case histories. What role the regulatory process does, and should, play is also described., The first section of this paper identifies and characterises the key water-related issues at wet and dry mine sites. Dry-climate case histories include a desert mine in Southern California where water recycle is maximised, and other non-traditional water supply sources are considered. Wet-climate case histories include a mine in Northern California where waste rock and tailings leachate as well as poor-quality pit water have required comprehensive water management both during operations and after closure, and a grass-roots mine development proposed in South America, where the potential water quality issues were partly responsible for altering the overall mine design. Complex geochemical and hydrogeological issues that have been dealt with at these mines include the generation of poor-quality water in the pits after closure; groundwater quality changes imprinted on naturally poor-quality groundwater; and generation of poor-quality leachate in the various types of waste rock, even where acidic conditions do not occur. The final part of the paper describes typical approaches to characterising and resolving key water and geochemical issues at dry and wet mines. Solutions are discussed and supported by the lessons learned from the case histories. What role the regulatory process does, and should, play is also described.

Chile's snow-capped Andes Mountains in the east are a source of water in the summer, as melted snow goes underground and serves as a water source where it surfaces in the form of small seepages known as bofedales. Water scarcity has compelled mining companies, whose activity accounts for about 15.2% of the country's GDP, to look for new sources of water and innovative technology for proper utilisation, as well as reuse, of the available water. Fog capture using mesh nets is an innovative method which can be a source of water. Desalination is another method which has gained popularity and is currently being used by many companies as a source of mine water. In terms of the Chilean Water Code of 1981, water is a privately traded commodity in Chile. This has enabled companies to take over control of large sources of water from the government, and sell water at high prices on the open market. Many of the rights for the control of water are held by foreign corporations. However, seawater usage has provided companies with large amounts of water, without any pressure on fresh water bodies. With processes such as desalination, mining companies can contribute to society by providing fresh water for public use. Mining is an industry which can also utilise water that is unfit for human consumption., Chile's snow-capped Andes Mountains in the east are a source of water in the summer, as melted snow goes underground and serves as a water source where it surfaces in the form of small seepages known as bofedales. Water scarcity has compelled mining companies, whose activity accounts for about 15.2% of the country's GDP, to look for new sources of water and innovative technology for proper utilisation, as well as reuse, of the available water. Fog capture using mesh nets is an innovative method which can be a source of water. Desalination is another method which has gained popularity and is currently being used by many companies as a source of mine water. In terms of the Chilean Water Code of 1981, water is a privately traded commodity in Chile. This has enabled companies to take over control of large sources of water from the government, and sell water at high prices on the open market. Many of the rights for the control of water are held by foreign corporations. However, seawater usage has provided companies with large amounts of water, without any pressure on fresh water bodies. With processes such as desalination, mining companies can contribute to society by providing fresh water for public use. Mining is an industry which can also utilise water that is unfit for human consumption.

Cerro Verde is a large copper mine located approximately 20 miles southwest of Arequipa, Peru. The area is characterised by an arid climate, rapid urban population growth and a long tradition of agriculture irrigated by surface water. The mine has been in operation since the early 1970s. A debottlenecking project was completed at the concentrator in 2010 to increase the concentrator throughput to its current capacity of 120 000 tonnes per day. The mine operation is dependent on having sufficient water supply. In most mining operations, the tailings storage facility consumes the most water. The largest water losses are attributed to evaporation and water trapped in the voids of the deposited tailings. The average annual evaporation is 60 times the average annual precipitation at the Cerro Verde mine, where it is a standard operating procedure to account for every drop of water. A water balance model was created for the Quebrada Enlozada storage facility during its design. The model has been updated and calibrated on a regular basis since the commissioning of the facility using actual information. This paper describes the tailings facility's design and its operational process, and presents the history of the water balance model development and the reasons for the low water losses that make the facility one of the most water-efficient tailing storage facilities in the world., Cerro Verde is a large copper mine located approximately 20 miles southwest of Arequipa, Peru. The area is characterised by an arid climate, rapid urban population growth and a long tradition of agriculture irrigated by surface water. The mine has been in operation since the early 1970s. A debottlenecking project was completed at the concentrator in 2010 to increase the concentrator throughput to its current capacity of 120 000 tonnes per day. The mine operation is dependent on having sufficient water supply. In most mining operations, the tailings storage facility consumes the most water. The largest water losses are attributed to evaporation and water trapped in the voids of the deposited tailings. The average annual evaporation is 60 times the average annual precipitation at the Cerro Verde mine, where it is a standard operating procedure to account for every drop of water. A water balance model was created for the Quebrada Enlozada storage facility during its design. The model has been updated and calibrated on a regular basis since the commissioning of the facility using actual information. This paper describes the tailings facility's design and its operational process, and presents the history of the water balance model development and the reasons for the low water losses that make the facility one of the most water-efficient tailing storage facilities in the world.

The Veladero gold mine is located in the centre of the Andes in San Juan, Argentina, at an altitude of about 4 000 m above sea level, with temperatures ranging from 20 degrees C in summer down to -30 degrees C in winter. The average consumption of water in the base camp is about 5.8 l/s, and after that, all sewage water is treated in plants operated with CARBOX technology. This volume is potentially eligible for reuse rather than final disposal in the soil infiltration pad. To reduce fresh water consumption so as to decrease environmental impact, a system capable of sending all the sewage water up to the leaching facilities was proposed, aimed at increasing the water volume used in the leaching process. A roughly 5 300 m long high-density polyethylene piping system was built with a gradient of 5%. Along with the piping, the system has an open reservoir which operates as a buffer pond, a filter station, a duplicated pumping station and seven pressure bleed stations. During the last year of operation, the system has responded satisfactorily, following the expected pattern and is currently being evaluated in order to increase its pumping capacity. The system has offered a solution for the specific abnormal environmental situation at the site, to preserve soil properties, reduce fresh water consumption associated with the leaching process and contribute to carrying out responsible mining operations., The Veladero gold mine is located in the centre of the Andes in San Juan, Argentina, at an altitude of about 4 000 m above sea level, with temperatures ranging from 20 degrees C in summer down to -30 degrees C in winter. The average consumption of water in the base camp is about 5.8 l/s, and after that, all sewage water is treated in plants operated with CARBOX technology. This volume is potentially eligible for reuse rather than final disposal in the soil infiltration pad. To reduce fresh water consumption so as to decrease environmental impact, a system capable of sending all the sewage water up to the leaching facilities was proposed, aimed at increasing the water volume used in the leaching process. A roughly 5 300 m long high-density polyethylene piping system was built with a gradient of 5%. Along with the piping, the system has an open reservoir which operates as a buffer pond, a filter station, a duplicated pumping station and seven pressure bleed stations. During the last year of operation, the system has responded satisfactorily, following the expected pattern and is currently being evaluated in order to increase its pumping capacity. The system has offered a solution for the specific abnormal environmental situation at the site, to preserve soil properties, reduce fresh water consumption associated with the leaching process and contribute to carrying out responsible mining operations.

The fundamental principles are reviewed of the magnetotelluric method and its practical application to the Tulargen deposit is described. The resistivity anomalies obtained were confirmed by drilling to be related to large and thick Cu-Ni orebodies. The applicability is discussed of the method in the Gobi and other desert areas of northwestern China., The fundamental principles are reviewed of the magnetotelluric method and its practical application to the Tulargen deposit is described. The resistivity anomalies obtained were confirmed by drilling to be related to large and thick Cu-Ni orebodies. The applicability is discussed of the method in the Gobi and other desert areas of northwestern China.

The following papers are included: Bioremediation of diesel-fuel-contaminated desert mining soils in the Atacama desert (Chile) - a tool for environmental management, by Godoy-Faundez A., Antizar-Lalislao B., Reyes-Bozo L., Saez-Navarette C. and Camano-Moreno A., p.407-411, 7 refs.; Mine closure - the state-of-the-art in Minas Gerais, Brazil, by Lima H.M., Cunha M.F. and Barcellos D., p.413-424, 5 refs.; Coordinating research and practice in oil sands mine reclamation, by Wilson V.R., Gulley J.R, Anderson H.B and Tedder W., p.425-430, 5 refs.; and Beating the budget - case study of closure of Rietspruit mine, South Africa, by van Renssen C.A., p.431-439, 1 ref., The following papers are included: Bioremediation of diesel-fuel-contaminated desert mining soils in the Atacama desert (Chile) - a tool for environmental management, by Godoy-Faundez A., Antizar-Lalislao B., Reyes-Bozo L., Saez-Navarette C. and Camano-Moreno A., p.407-411, 7 refs.; Mine closure - the state-of-the-art in Minas Gerais, Brazil, by Lima H.M., Cunha M.F. and Barcellos D., p.413-424, 5 refs.; Coordinating research and practice in oil sands mine reclamation, by Wilson V.R., Gulley J.R, Anderson H.B and Tedder W., p.425-430, 5 refs.; and Beating the budget - case study of closure of Rietspruit mine, South Africa, by van Renssen C.A., p.431-439, 1 ref.

Case studies from two 225 000 t/d copper mines demonstrate that extracting water from tailings has the potential to be a better option financially than sourcing make-up water from the sea. Several tailing dewatering methods were considered: high-rate thickening, high-compression thickening in units of 50, 62 or 75 m diameter, paste thickening, vacuum filtration and pressure filtration, with transport by centrifugal or positive-displacement pumps, belt conveyors or open launders., Case studies from two 225 000 t/d copper mines demonstrate that extracting water from tailings has the potential to be a better option financially than sourcing make-up water from the sea. Several tailing dewatering methods were considered: high-rate thickening, high-compression thickening in units of 50, 62 or 75 m diameter, paste thickening, vacuum filtration and pressure filtration, with transport by centrifugal or positive-displacement pumps, belt conveyors or open launders.

Papers are presented covering various aspects of sustainable development and life-cycle analysis in relation to exploration, mining, extraction and mineral processing with particular respect to social, economic and environmental issues. Topics include: coal and lignite mining in Germany and other European countries; production of bulk raw materials; recycling of cars, sewage sludge in ceramic bricks and glass in backfill; reclamation and spontaneous revegetation; the Omo forest reserve in Nigeria and the Mojave Desert sustainability project in the USA; bioreactor landfill for methane gas disposal; oil and gas pipeline financing and safeguards; mineral planning policies in a range of EU countries; and the selection of sustainable development indicators for different countries or metal industries., Papers are presented covering various aspects of sustainable development and life-cycle analysis in relation to exploration, mining, extraction and mineral processing with particular respect to social, economic and environmental issues. Topics include: coal and lignite mining in Germany and other European countries; production of bulk raw materials; recycling of cars, sewage sludge in ceramic bricks and glass in backfill; reclamation and spontaneous revegetation; the Omo forest reserve in Nigeria and the Mojave Desert sustainability project in the USA; bioreactor landfill for methane gas disposal; oil and gas pipeline financing and safeguards; mineral planning policies in a range of EU countries; and the selection of sustainable development indicators for different countries or metal industries.

Geological hazards are not all natural, and their associated damage and costs are likely to rise with global population, especially with increased occupancy and degradation of high-risk land. The risk of their occurrence can be assessed and the spatial and temporal probabilities mapped to assist in land use planning. Hazards may arise as a result of volcanic activity, earthquake activity, mass movements, problem soils, river action, marine action, wind action or problems associated with arid regions, soil erosion and desertification, waste disposal, groundwater pollution and ground subsidence over old pillar-and-stall, longwall or metalliferous mines and shafts. Each of these is discussed, together with the possibilities for control and remediation. There is a reference list for each chapter and the book has a subject index., Geological hazards are not all natural, and their associated damage and costs are likely to rise with global population, especially with increased occupancy and degradation of high-risk land. The risk of their occurrence can be assessed and the spatial and temporal probabilities mapped to assist in land use planning. Hazards may arise as a result of volcanic activity, earthquake activity, mass movements, problem soils, river action, marine action, wind action or problems associated with arid regions, soil erosion and desertification, waste disposal, groundwater pollution and ground subsidence over old pillar-and-stall, longwall or metalliferous mines and shafts. Each of these is discussed, together with the possibilities for control and remediation. There is a reference list for each chapter and the book has a subject index.

Environmental geotechnology is defined as an interdisciplinary science of soil and rock and their interaction with various environmental cycles. The placing of a foundation or any other soil disturbance can lead to favourable or detrimental interactions, which the engineer should take into account. Chapters are presented on: particle-energy-field theory and applications; the nature of soil and environment; soil technology; soil-water-air interaction; soil shrinkage, swelling and cracking; hydraulic conductivity and mass transport; thermal and electrical properties of soils; radiation effects; compressibility and stress-strain-time behaviour; environmental geotechnical engineering; problematic soils and rocks; wetlands, coastal margins and soil erosion; subsidence; slope stability and landslides; solid/liquid waste control and use; and arid regions and deserts. There are several appendices, 24 pages of references and an index., Environmental geotechnology is defined as an interdisciplinary science of soil and rock and their interaction with various environmental cycles. The placing of a foundation or any other soil disturbance can lead to favourable or detrimental interactions, which the engineer should take into account. Chapters are presented on: particle-energy-field theory and applications; the nature of soil and environment; soil technology; soil-water-air interaction; soil shrinkage, swelling and cracking; hydraulic conductivity and mass transport; thermal and electrical properties of soils; radiation effects; compressibility and stress-strain-time behaviour; environmental geotechnical engineering; problematic soils and rocks; wetlands, coastal margins and soil erosion; subsidence; slope stability and landslides; solid/liquid waste control and use; and arid regions and deserts. There are several appendices, 24 pages of references and an index.

Analysis of samples from two sites, whose only sources of water are from human input on the hillsides above, showed clearly that geochemical processes in the tailings are directly related to this input. The detected processes are related to pyrite oxidation and show strong mobilisation of all types of elements. The distribution of elements indicates an upward-migrating oxidation zone, characterised by the precipitation of Fe(III) hydroxides from Fe(II), metal-rich solutions and a water flow confined to the top of the oxidation zone. Acid and sulphate-rich solutions, having leached heavy metals from the primary material, are buffered by calcite and clay minerals and precipitate first Fe hydroxides, which fill the pore spaces and divert the water flow upwards, and then secondary metal sulphides. Heavy metals are also stabilised by adsorption., Analysis of samples from two sites, whose only sources of water are from human input on the hillsides above, showed clearly that geochemical processes in the tailings are directly related to this input. The detected processes are related to pyrite oxidation and show strong mobilisation of all types of elements. The distribution of elements indicates an upward-migrating oxidation zone, characterised by the precipitation of Fe(III) hydroxides from Fe(II), metal-rich solutions and a water flow confined to the top of the oxidation zone. Acid and sulphate-rich solutions, having leached heavy metals from the primary material, are buffered by calcite and clay minerals and precipitate first Fe hydroxides, which fill the pore spaces and divert the water flow upwards, and then secondary metal sulphides. Heavy metals are also stabilised by adsorption.

The Saudi Company for Precious Metals (SCPM), jointly owned by Petromin and Boliden, operates the Sukhaybarat gold mine in the Saudi Arabian desert and produces some 80 000 oz/a Au by agitation and heap leaching. Mineralisation was first intercepted in 1983 and it took 8 years to delineate ore reserves, locate water sources, prepare feasibility studies, obtain permits and design and construct the facilities. The open pit mine commenced with only a carbon-in-leach agitation plant but a heap leach facility was added in 1995 to process weathered ore. Gold head grades are in the range of 3.4-3.6 g/tonne with gold recovery of 91%; cash operating costs are between US, The Saudi Company for Precious Metals (SCPM), jointly owned by Petromin and Boliden, operates the Sukhaybarat gold mine in the Saudi Arabian desert and produces some 80 000 oz/a Au by agitation and heap leaching. Mineralisation was first intercepted in 1983 and it took 8 years to delineate ore reserves, locate water sources, prepare feasibility studies, obtain permits and design and construct the facilities. The open pit mine commenced with only a carbon-in-leach agitation plant but a heap leach facility was added in 1995 to process weathered ore. Gold head grades are in the range of 3.4-3.6 g/tonne with gold recovery of 91%; cash operating costs are between US

The Sahel zone, south of the Sahara desert, constitutes a 300 km wide transition zone from arid desert to moist savana and rainforest on the coast and includes Senegal, Mali, Burkina Faso and Niger. Surficial formations often occur which blanket the distribution of trace elements, particularly gold. There are two types of formation: aeolian sand cover or isolated deposits of sand, and ferrallitic weathering. A discussion is presented of geochemical prospecting in these formations, based on surveys in Mali and Niger., The Sahel zone, south of the Sahara desert, constitutes a 300 km wide transition zone from arid desert to moist savana and rainforest on the coast and includes Senegal, Mali, Burkina Faso and Niger. Surficial formations often occur which blanket the distribution of trace elements, particularly gold. There are two types of formation: aeolian sand cover or isolated deposits of sand, and ferrallitic weathering. A discussion is presented of geochemical prospecting in these formations, based on surveys in Mali and Niger.

A rotary dry concentrator that can handle, in continuous operation, alluvial deposits in the same size range as those treated by traditional wet plants has been developed in Australia. Four of these units were mounted on an integrated towable treatment plant which has been in successful commercial operation in northern Queensland for 5 years. Grades of less than 0.2 g Au/loose m3 have been profitably mined at throughputs of 80 m3/h at 85% availability, recovering about 85% of the gold in the -12 mm to +0.07 mm fraction. A second single-unit larger module has been successfully tested in the USA, as a prelude to full scale mining, and is also under consideration ahead of the crushing circuit in some heap leach operations. Major benefits, apart from lower capital and operating costs, are environmental: rehabilitation can be completed almost immediately behind the plant as it advances. The principal disadvantage is moisture which restricts the application of the technique., A rotary dry concentrator that can handle, in continuous operation, alluvial deposits in the same size range as those treated by traditional wet plants has been developed in Australia. Four of these units were mounted on an integrated towable treatment plant which has been in successful commercial operation in northern Queensland for 5 years. Grades of less than 0.2 g Au/loose m3 have been profitably mined at throughputs of 80 m3/h at 85% availability, recovering about 85% of the gold in the -12 mm to +0.07 mm fraction. A second single-unit larger module has been successfully tested in the USA, as a prelude to full scale mining, and is also under consideration ahead of the crushing circuit in some heap leach operations. Major benefits, apart from lower capital and operating costs, are environmental: rehabilitation can be completed almost immediately behind the plant as it advances. The principal disadvantage is moisture which restricts the application of the technique.

About 90% of the nickel produced in China since the 1960s has been from the Jinchuan Nonferrous Metals Corporation. The plant was constructed on the edge of the Tenggeli Desert in the NW of the Asian continent and, as there was no resident population, environmental problems were ignored. Since the 1980s many projects have concentrated on environmental protection including the use of solid wastes, waste water and sulphur dioxide recovery., About 90% of the nickel produced in China since the 1960s has been from the Jinchuan Nonferrous Metals Corporation. The plant was constructed on the edge of the Tenggeli Desert in the NW of the Asian continent and, as there was no resident population, environmental problems were ignored. Since the 1980s many projects have concentrated on environmental protection including the use of solid wastes, waste water and sulphur dioxide recovery.

A prototype rotary dry concentrator has been developed that can handle tHe fine-grained fraction of alluvial deposits as well as the coarse. It has demonstrated its capacity to mine gold-bearing superficial deposits where water is in insufficient supply and at grades that would not support wet mining. Four units mounted on an integral towable treatment plant have been operating successfully in northern Queensland for four years, and a second plant is now under construction for use in the USA. Grades of less than 0.2 g/lcm have been profitably mined at throughputs of about 80 m3/h and 85% availability. Major benefits, apart from lower capital and operating costs, are environmental: ore is picked up, treated and replaced in its original mixed condition within 25 m of its original location, leaving no slimes dams, coarse stockpiles or haul roads as the plant advances. The main handicap is moisture, with mining only possible for six months of the year in Queensland; suitable deposits in desert regions are being sought by the developers., A prototype rotary dry concentrator has been developed that can handle tHe fine-grained fraction of alluvial deposits as well as the coarse. It has demonstrated its capacity to mine gold-bearing superficial deposits where water is in insufficient supply and at grades that would not support wet mining. Four units mounted on an integral towable treatment plant have been operating successfully in northern Queensland for four years, and a second plant is now under construction for use in the USA. Grades of less than 0.2 g/lcm have been profitably mined at throughputs of about 80 m3/h and 85% availability. Major benefits, apart from lower capital and operating costs, are environmental: ore is picked up, treated and replaced in its original mixed condition within 25 m of its original location, leaving no slimes dams, coarse stockpiles or haul roads as the plant advances. The main handicap is moisture, with mining only possible for six months of the year in Queensland; suitable deposits in desert regions are being sought by the developers.

Papers presented in this section are: Chronic copper toxicity in ruminants - prophylatic salt lick, by Scheepers G.J., p.153-158, 2 refs.; Forest ecosystem and mining activity, by Badrinath S.D., Chakraborty A. and Khan S., p.159-172, 3 refs.; and Designing eco-balance system for mechanised opencast limestone mines in Thar desert area of western Rajasthan, by Rathore S.S. and Gupta K.P., p.173-180., Papers presented in this section are: Chronic copper toxicity in ruminants - prophylatic salt lick, by Scheepers G.J., p.153-158, 2 refs.; Forest ecosystem and mining activity, by Badrinath S.D., Chakraborty A. and Khan S., p.159-172, 3 refs.; and Designing eco-balance system for mechanised opencast limestone mines in Thar desert area of western Rajasthan, by Rathore S.S. and Gupta K.P., p.173-180.

The papers present an overview of the mineral species, possible mechanisms involved in their precipitation and the range of surficial depositional environments recorded for Fe and Mn minerals. The documented sites range from intracellular to million-ton orebodies. Research thrusts are on both modern and ancient environments because similar biogeochemical mechanisms to those cited for modern sediment accumulation may have been involved in the formation of the earliest laminated rocks, the banded iron formations and Proterozoic flat-lying Mn deposits. Introductory chapters present background material outlining the crystal chemistry and common occurrences of Fe and Mn minerals and surveying known microbiological mediators. Bacterial mechanisms and reactions related to Fe/Mn oxides in general are discussed and descriptions given of the range of mineral types and forms associated with and in bacterial species, fungi, and a human Fe-protein complex. Modern geodepositional sites are covered by papers on desert varnish, soils and groundwater, marshes, oceanic sediments and mine ponds, and the genesis of ancient deposits evaluated for Groote Eylandt in Australia's Northern Territory, the Cuyuna North range in Minnesota and the late Archaean banded iron formation of Bababudans in Karnataka, India., The papers present an overview of the mineral species, possible mechanisms involved in their precipitation and the range of surficial depositional environments recorded for Fe and Mn minerals. The documented sites range from intracellular to million-ton orebodies. Research thrusts are on both modern and ancient environments because similar biogeochemical mechanisms to those cited for modern sediment accumulation may have been involved in the formation of the earliest laminated rocks, the banded iron formations and Proterozoic flat-lying Mn deposits. Introductory chapters present background material outlining the crystal chemistry and common occurrences of Fe and Mn minerals and surveying known microbiological mediators. Bacterial mechanisms and reactions related to Fe/Mn oxides in general are discussed and descriptions given of the range of mineral types and forms associated with and in bacterial species, fungi, and a human Fe-protein complex. Modern geodepositional sites are covered by papers on desert varnish, soils and groundwater, marshes, oceanic sediments and mine ponds, and the genesis of ancient deposits evaluated for Groote Eylandt in Australia's Northern Territory, the Cuyuna North range in Minnesota and the late Archaean banded iron formation of Bababudans in Karnataka, India.

The establishment of a mine in a remote and undeveloped desert region requires an understanding of the far-reaching effects that this will have on the local population and the environment. Responsible management is essential to ensure the full potential benefits of the mine are realised. The establishment of one mine's infra-structure, the township and medical, recreation, conservation and socio-economic factors is discussed., The establishment of a mine in a remote and undeveloped desert region requires an understanding of the far-reaching effects that this will have on the local population and the environment. Responsible management is essential to ensure the full potential benefits of the mine are realised. The establishment of one mine's infra-structure, the township and medical, recreation, conservation and socio-economic factors is discussed.

Placers in arid environments conform to a geological model accommodating two basic placer types: eluvial-colluvial deposits developing in modern day arid environments and alluvial palaeo-placers formed under more humid conditions. The developed geological model accommodates a variety of factors influencing the distribution of sediment and the related heavy mineral suite. Increasing transport distance from the provenance area alters both the clasts and the accompanying gold grains. A more humid depositional environment is more effective in milling sediments and contained gold than arid environments. This jigging action associated with alluvial deposits would concentrate gold more effectively on bedrock., Placers in arid environments conform to a geological model accommodating two basic placer types: eluvial-colluvial deposits developing in modern day arid environments and alluvial palaeo-placers formed under more humid conditions. The developed geological model accommodates a variety of factors influencing the distribution of sediment and the related heavy mineral suite. Increasing transport distance from the provenance area alters both the clasts and the accompanying gold grains. A more humid depositional environment is more effective in milling sediments and contained gold than arid environments. This jigging action associated with alluvial deposits would concentrate gold more effectively on bedrock.

Two symposia were held at the meeting: Geochemical exploration in arid and deeply weathered environments, including 25 papers, and Geochemistry and genesis of ore deposits associated with weathering, jointly sponsored by the Specialist Group in Economic Geology of the Geological Society of Australia and including five papers., Two symposia were held at the meeting: Geochemical exploration in arid and deeply weathered environments, including 25 papers, and Geochemistry and genesis of ore deposits associated with weathering, jointly sponsored by the Specialist Group in Economic Geology of the Geological Society of Australia and including five papers.

The case histories of two of the world's largest copper mines-the Bougainville mine in Papua New Guinea and the Toquepala mine in Peru-illustate many of the problems encountered in the creation of a mine in an isolated area of a non-industrialised country, one a rain forest and the other a desert. Rarely are the considerations that must go into a decision to invest in a mine costing several hundred million dollars fully appreciated. A better understanding of these issues as they relate to the foreign investment policies of the host countries and to the negotiation and implementation of mine development agreements between host countries and foreign mining companies is essential., The case histories of two of the world's largest copper mines-the Bougainville mine in Papua New Guinea and the Toquepala mine in Peru-illustate many of the problems encountered in the creation of a mine in an isolated area of a non-industrialised country, one a rain forest and the other a desert. Rarely are the considerations that must go into a decision to invest in a mine costing several hundred million dollars fully appreciated. A better understanding of these issues as they relate to the foreign investment policies of the host countries and to the negotiation and implementation of mine development agreements between host countries and foreign mining companies is essential.

Plateau Resources' Tony M uranium mine is situated in Utah in a sparsely populated desert region. The deposit occurs within the Morrison Formation, a Jurassic sandstone unit, and is tabular in form. Coffinite is the most abundant ore mineral; vanadium is also present but is not abundant enough to exploit. Current reserves are estimated at 5 780 000 tonnes at 0.108% U3O8 containing 6 170 000 kg of U3O8. Reserve estimation methods, mine planning and development, production, transport and infrastructure development are discussed., Plateau Resources' Tony M uranium mine is situated in Utah in a sparsely populated desert region. The deposit occurs within the Morrison Formation, a Jurassic sandstone unit, and is tabular in form. Coffinite is the most abundant ore mineral; vanadium is also present but is not abundant enough to exploit. Current reserves are estimated at 5 780 000 tonnes at 0.108% U3O8 containing 6 170 000 kg of U3O8. Reserve estimation methods, mine planning and development, production, transport and infrastructure development are discussed.