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The usual metallurgical, engineering and administrative activities associated with the handling and smelting of ores, and the subsequent handling and treatment of the products of smelting, present also problems of hygiene that engage the earnest attention of executives in all well-managed concerns.Again, associated with the employment of any considerable number of men, there is always present the problem of accident prevention.INDUSTRIAL HYGIENE.In the earliest records of lead min.ing and smelting there are references to the injurious effects of lead oh the health of the employees, and, with the advancement of medical science, lead poisoning has been the subject of many works by various authorities in many countries.Moreover, in practically every civilised country, there are laws governing the conduct of the lead industry, and in most cases these laws stipulate that employees shall receive compensation for disability caused by lead poisoning.This provision gives the problem an economic aspect. Apart from the legal and the economic aspects, however, there is the humanitarian aspect, which implies that the...

Jan 1, 1937

A study of the accessory opaque iron-titanium oxide minerals of the Oiles Complex, central Australia, was an Important complement to an investigation of the magnetic properties of the Complex. These minerals constitute no more than 10 per cent of the rocks sampled, and generally less than 1 per cent of the ultramafic rocks ("magnetite" concentrations were not sampled for magnetic investigation).Titanomagnetite is the main opaque mineral present, although ilmenite exsolution has been widely developed. High-temperature oxidation of these produced mainly titanohematite, pseudobrookite and rutile. Both exsolution and high-temperature oxidation developed along specific crystallographic directions (along {111}), and in Irregular patches. Low-temperature oxidation is generally not well-developed, indicating the small degree of weathering in the rocks sampled.Although the Oiles Complex is layered, no apparent overall preferred orientation of the iron-titanium oxide minerals was observed, other than crystallographically controlled alignment of very fine grains within pyroxene crystals. Other textural features of the opaque oxides are restricted to symplectic intergrowths mainly with the ferromagnesian silicates.

Jan 1, 1971

Human-caused global warming has become the environmental cause celebre of the early 21st century. The strong warming alarmist camp currently includes the United Nations, most Western governments, most of the free press, many large corporations (including Enron, before it failed), the major churches, most scientific organisations and a large portion of general public opinion. This phalanx of support notwithstanding there is no scientific consensus as to the danger of human-induced climate change. There is, therefore, a strong conflict between the level of public alarm and its scientific justification. How can this be? In a democracy, the media serve to convey to the public the facts and hypotheses of climate change as provided by individual scientists, governmental and international research agencies, and NGO and other lobby groups. In general, the media have promulgated an alarmist cause for climate change; they have certainly failed to convey the degree of uncertainty that is characteristic of climate science, or a balanced summary of the many essential facts that are relevant to human causation. Climate change is as much a geological as it is a meteorological issue. Natural climate changes, both warmings and coolings, are indeed a societal hazard. We usually deal with geological hazards by providing civil defence authorities and the public with accurate, evidence-based, general information about events like earthquakes, volcanic eruptions, tsunamis and floods, and then by adapting to the effects when a damaging event occurs. As for other major natural disasters, the appropriate preparation for extreme climate events is to mitigate and manage the negative effects when they occur, and especially so for dangerous coolings. Attempting instead to æstop climate changeÆ by reducing human carbon dioxide emissions is a costly exercise of utter futility. Rational climate policies must be based on adaptation to dangerous change as and when it occurs, and irrespective of its sign or causation. The issue now is no longer climate change as such, the reality of which will always be with us. Rather, the issues are, first, the failure of the free press to inform the public about the true facts of human-caused climate change and of the dangers posed by natural climate change. And, second, the vested interests held by many of the groups of warming alarmists. These interests include not only the obvious commercial ones, but also the many scientists and science managers who have discounted or remained silent about the huge uncertainties of the human-caused global warming hypothesis because it suited them to do so. Public opinion will soon demand an explanation as to why experienced editors and hardened investigative journalists, worldwide, have melted before the blowtorch of self-induced guilt, political correctness and special interest expediency that marks the sophisms of global warming alarmists.

Jan 1, 2007

Simulation and Analysis of Media Behaviour in the Tower Mill by Discrete Element Method for Estimating the Power Draw and Spatial Distribution of Grinding Process The trends to the Tower Mill (TM) for grinding the materials are increased recently due to its unique merits. Among the various considerations of this machine, the main important items are increasing the efficiency of grinding as more as possible while keep the power consumption, manufacturing and maintenance costs as less as possible. Because this grinding process includes a huge numbers of media particles (ball or other shapes) that are interacted with each other and body of the machine, the DEM (Discrete Element Method) way is a very useful and essential step to getting confident evaluations. Because the DEM simulation is a very young scientific field and proper commercial software are very rare and still under modification, at first step, a FORTRAN code is developed for DEM simulation of two laboratory Tower Mill models (KM5 and KD5). The simulation and experimental results matched each other properly. Then one another DEM software was implemented to perform simulation of bigger models (huge numbers of balls), meanwhile could handle the complex 3D geometry data. The simulation and experimental results were compared and analysed in detail for not only laboratory but also for industrial models (KW5, KWD5, KWD50, KW300F, KW700F and KW1500) without any manipulation or compromising of the parameters of simulation. Some numeric data of industrial models are hidden here due to confidential reasons. The relative velocity of balls (ball-ball and ball-TM body), dissipate energy, interacted forces and stresses during the process are the key outputs of DEM simulation for design this machine. Therefore the main important processes in a Tower Mill machine are recognised and consequently some horizons of development of this machine are distinguished.

Sep 13, 2010

Two types of low-sulphidation epithermal mineralisation may be recognised in volcanic terranes. Chalcedonic Silica- Adularia-Illite type mineralisation is most common in rhyolitic terranes, whereas Crystalline Quartz-Illite-(Adularia- Kaolinite) type mineralisation is more typically formed in andesitic terranes. A third type of epithermal mineralisation, the high sulphidation or Vuggy Silica-Alunite- Kaolinite-Illite type, is also common in andesitic terranes. Episodic violent boiling, accompanying hydraulic fracturing and hydrothermal eruptions, characteristic of geothermal systems in rhyolitic terranes, is stressed for the formation of Chalcedonic Silica mineralisation. Such boiling of deeply circulating meteoric groundwater, with some magmatic fluid contribution, provides chalcedonic veining, episodic banding and brecciation textures, adularia stability, bladed calcite, and extreme loss of H2S from the fluid to cause major gold deposition. Crystalline Quartz mineralisation is probably caused by the mixing of shallow acidic groundwater with ascending deep geothermal fluids beneath andesitic strato- volcanoes. The cooling effect, oxidation, and increased acidity, overcomes the dilution effect, and results in quartz deposition, illite (and locally kaolinite) alteration, and precipitation of metals. Extensive formation of base-metal sulphides further enhances gold deposition. Violent boiling is restricted to local structural dilation sites, potentially producing high grade "bonanza" gold mineralisation.

Jan 1, 1991

Shaft sinking through an amphibolite-granite rock mass experienced rock bursts on the shaft walls and benches. However, rock burst phenomena was exhibited only in granite, which is e1asto-brittle with ability to store strain energy caused by orogenic and man made stresses. To improve ground conditions, blasting of destressing holes at shaft corners was carried out. By this technique rock burst during shaft sinking was minimized, but not eliminated.

Jan 1, 1982

Experimental Validation of a Flotation Cell Model

Sep 13, 2010

A Sun SPARCstation based computer network is utilised to store and process mining data at the Macraes Gold Mine. Techbase and Medsystem software running on the SunOS unix platform is used to generate all data plans, sections and other design data required on a daily basis to run the mining operation. The Macraes site is regarded as a fully integrated site where all geological, grade control, exploration, orebody modelling, resource estimation, pit optimisation and mine design is undertaken on site by MacraesÆ professional staff. The methodologies employed are regarded as æstate-of-the-artÆ where computerisation allows the rapid and efficient evaluation of large quantities of mining data by a handful of professional personnel. Ore reserves are estimated using an indicator kriging method and roving cone pit optimisation, a complex process that would not have been achievable in pre-computing days.

Jan 1, 1992

By K H. Esbensen, K Engström

The conclusion from the debate over the last decade in the mining sector is that, for grade control, reverse circulation (RC) drill sampling gives more reliable results due to less sampling problems than blasthole samples. However, by conducting the latter with well-controlled procedures there still exist fair possibilities to counteract the major blasthole sampling problems and achieve fit-for-purpose representativeness, especially if based on minimal loss of fines. In the present PhD study, extensive replicate experiments and variographic characterisations are conducted to evaluate the performance of manual blasthole (BH) sampling and sectorial segment sampling. The experiments were performed in Luossavaara-Kiirunavaara AB (LKAB)’s Leveäniemi open pit mine in the north of Sweden. The experimental area is an apatite-magnetite iron ore deposit of the Kiruna type, with the demand to exhibit a maximum of local heterogeneity to allow the experiment the largest possible conclusion powers. Gathering and splitting the complete BH drill cutting cones (fines cone, coarse cone) served as an authoritative reference on which to assess the representativity of the two BH sampling methods.Results show that manual BH drill sampling is able to produce samples with an acceptable accuracy and precision if performed properly and with insight. Based on variographic comparison, segment sampling shows similar precision for chemical grades as the manual sampling, while the particle size distributions were more deviating for segment sampling than for manual sampling at the high and low size ranges. Possible reasons for these partly surprising results are discussed.For further investigation of the performance of BH versus RC drill sampling, a second experiment has been planned on a parallel profile. This will result in an unprecedented opportunity for a full variographic comparison between RC and BH sampling, aimed at designing specific, fit-for-purpose sampling procedures as a function of ore quality, cut-off grades and important contaminant levels.CITATION:Engström, K and Esbensen, K H, 2017. Blasthole sampling (replicate and variographic experiments) in LKAB open pit iron ore mines – fit-for-purpose representativity?, Australia, in Proceedings Eighth World Conference on Sampling and Blending , pp 85–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By Creasey J. W, Huntington J. F

Faults cutting the Lithgow and Katoomba seams in some collieries of the Western Coalfield can be classified, on the basis of spatial pattern, into three principal groups: meridional swarms of closely spaced minor faults and associated joints, with throws of less than 0.5 m and with exceptional faults of up to 5 m; isolated interswarm strike-slip faults in the Lithgow seam and widely spaced strike-slip faults in swarms in the Katoomba seam; and low-angle normal faults associated with the Lidsdale-Lithgow seam split.Orientations of faults and coal cleats in the coalfield are presented on stereoplots and histograms, as a basis for an analysis of fault dynamics. The low-angle normal faults were found to have been formed only along the Lidsdale-Lithgow seam split, and before the high-angle faults. The origin of the high-angle normal faults in the meridional swarms is discussed and it is suggested that basementcover interactions must have occurred. This suggestion is supported by geophysical evidence. Low-amplitude monoclines in the coal seam, and the spacing of swarms 0.9 to 4.5 km apart, may be due to the underlying basement structure.It is clear that postextensional compressive deformation of swarms in the coalfield gave rise to shortening by minor thrust development, and probably also caused the synchronous strike-slip movement on pre-existing normal faults. There is evidence to show that isolated interswarm strike-slip faults in the Lithgow seam, and widely spaced strike-slip faults in the Katoomba seam, may have originated synchronously with such thrusts. The axis of maximum principal compression ('71) for the thrust event was inferred to be near horizontal and aligned approximately E-W. Recent rock mechanics measurements of the present day stress field indicate a similar stress configuration.

Jan 1, 1981

By McLean E. J

Background The resources of the Gippsland Basin include not only the coal and oil for which it is well known, but also the tourism resource and the quality of life which it offers its residents and visitors. To manage this group of resources requires an understanding and ability to predict the consequences of possible developments. The water of the streams and estuaries as a key component as it is both a resource and the means for transporting wastes from one area to another. To aid in the resource planning process there is a need for models of the estuarine hydraulic processes. This paper describes an appropriate modelling technique. Resource use conflicts may arise from developments in the catchment upstream of the estuarine reach. For example the diversion of water for domestic and industrial use will change the velocity and salinity structure of the downstream estuary. In turn these changes will affect sediment distribution and deposition patterns and may impose stress on the biological communities and ultimately on the fisheries resources and water quality. The manager of an estuarine system may have expertise in ecology, hydraulics or another of the specialist disciplines involved, but commonly will not. The manager will identify needs for resource and development and the broad options required to satisfy them. The manager will use these studies as the basis for his/her selection of the option for execution. Thus a model for'use by the manager of an estuarine system must have the following properties: (i) The model must be sufficiently accurate to throw up all the likely options. (ii) The model must be capable of being run by the manager, interactively, to answer `what if' questions. This requirement implies a simple code andhardware limited to a personal computer or possibly a desk top work station. (iii) The model must be robust so that unrealistic input oes not generate apparently useful output, and no output is generated for cases where the model is not designed to give results. (iv) The model must be capable of being used as part of a modelling system comprising models of all the geographic and demographic components

Jan 1, 1992

By Hindmarsh J. W, McCoy A. E R

Instantaneous outbursts of coal and gas have occurred at various times in several working districts of Metropolitan Colliery, N.S.W.They have occurred in headings only, under both hand and mechanised conditions, and with seam gas ranging from mainly methane to nearly pure carbon dioxide. A modification of inducer shotfiring using a shear cut was introduced in 1955, and in 1961 full face firing both to a machine cut shear and off the solid was introduced. The current series of outbursts -1961 to 1963 - has been induced under these systems with full control of the time of outburst, but without prediction, and with some disappointing production features.Various aspects of current conditions and practices at Metropolitan are considered singular, such as the coarse granulometry of outburst coal, the prevalence of floor heave, the absence of strong structures at outburst sites, the possibility of outburst at any stage in pillar formation up to the last few yards, the effect of rate of advance on outburst occurrence, and the mildness of many outbursts experienced.It is concluded that inducer shotfiring is a reliable control but it suffers by comparison with outburst-free conditions, and that control by preyention would be preferable.INTRODUCTIONThe phenomenon of instantaneous outbursts of coal and gas has been described in detail previously (Hargraves, 1958). Briefly, it is a combined gas and stress hazard of deep coal mining, usually occurring in virgin work and during active face advance, when coal and seam gas burst from the face into the workings.Instantaneous outbursts have occurred sporadically at Metropolitan Colliery, N.S.W., since 1895. Early outbursts were recorded as firedamp and recent outbursts are of blackdamp.Mining methods used have been conventional hand work, with progressive and relatively complete mechanisation over the past 25 years to substantially conventional...

Jan 1, 1964

By J Hall, A Gallardo, M Strizek

Mineralogy and coproponents Sino Iron, International Minerals and Austeel are in the process of developing four world class magnetite iron ore mines with multiple open pits along a 25 km strike length of Brockman Iron Formation to the south of Cape Preston on the West Pilbara coast. The close proximity of the proposed pits raises some challenging project approvals and environmental management issues relating to the impacts of dewatering at individual projects and the cumulative impacts of progressive development on local and regional groundwater resources, which includes a large fresh water aquifer system in the Fortescue River alluvium.This paper presents an outline of the hydro-environmental impact assessment process adopted and the key result that the cumulative impacts of dewatering at all four projects on the local brackish groundwater system in the basement rocks is only marginally more than the impact of any one project on its own, and that the impact on the Fortescue River alluvium aquifer is negligible. The paper also presents an outline of the proposed integrated water management approach that will involve coordinated monitoring, ongoing impact assessment and management, and reporting programs for all projects.

Jan 1, 2009

To form a true picture of the early history of Queensland, we must think of white settlement advancing like an incoming tide, wave by wave; each wave lapping ahead a little further than the last. The credit for opening up the country belongs to a large number of pioneers, each of whom pushed out just a little further than his predecessors.Contrary to what one might expect, Rockhampton district was settled by overlanders from the south and not from the ocean side. When the Archers, the pioneers of the Rockhampton district, reached Gracemere in 1853, settlement had already made its way down the valley of the Dawson River; for it was from Leith Hay's station at Rannes (a few miles below Mount Morgan) that the Archers advanced northward into the unknown, to find the river that the explorer, Ludwig Leichhardt, had told them must enter the sea somewhere near the Tropic of Capricorn.The Archers travelled northward from Rannes up the valley of the Dee, coming out on the edge of the Razorback Range not very far from the point at which the Dawson Valley Highway drops over into Poison Creek. (Their diary records the bearings from a lookout point to various peaks around Rockhampton, and to-day, by plotting back from these peaks, we can determine the exact spot at which they descended on to the Fitzroy Flats.) We can be certain, then, that they must have been the first white men to set eyes on Mount Morgan; though to them it would have seemed to be nothing more than an insignificant hill...

Jan 1, 1939

The Hyde Macraes Shear Zone (HMSZ) is an extensive low angle semibrittle mineralised structure in the Otago Schist Belt, New Zealand. The shear zone is located on the lower limb of a late metamorphic recumbent fold. Structural observations suggests that the shear zone initiated as a high strain mylonite zone and transgressed the ductile/brittle boundary (D4) later in its development. A surge zone at Round Hill is bounded to the south by a NE-SW striking lateral ramp which displaces the hanging wall shear (HWS) by 50 m. Oblique strike slip displacement during surge zone propagation created space for deposition of the sheeted vein complex or stockwork. Quartz recrystallisation in stockwork veins suggests that the veins were deformed in a ductile manner and implies that surge zone propagation may have occurred during late D3 deformation. A macroantiform was produced during D3/D4 shortening below the HWS. Over tightening of the antiform hinge created SW and NE-dipping ramp thrusts. Continued strike slip displacement along the lateral ramp rotated the antiform and associated ramps into a south plunging drag fold. Post-mineralisation (D5) structures include NE-dipping nonna! faults below the HWS and SW-dipping low angle imbricate thrusts above the HWS. The development of these structures was kinematically compatible with normal movement on the HMSZ and is related to mid Cretaceous break up of Gondwanaland in the SW Pacific.

Jan 1, 1992

By Hargraves A. J

The paper outlines events at the Collinsville State Coal Mine, Queensland, leading to the practice of full face multiple shotfiring in bord and pillar development places. The 1954 disaster is referred to, and factors involved in simultaneous shotfiring in coal are discussed. Promising preliminary multiple shotfiring tests at the Colliery are described, as well as the resulting routine measures adopted, and the changes involved. The subsequent inducing of two outbursts under safe conditions by remote multiple shotfiring is given as justification for the changes made.INTRODUCTIONFollowing a disastrous instantaneous outburst (1.0.) of coal and gas at the Collinsville State Coal Mine in 1954, the necessity for inducer shotfiring for the control of possible further outbursts was established. However this mine, immediately classified as gassy after the 1954 outburst, is subject to the general restrictions pertaining to gassy mines which at present preclude the use of inducer shotfiring due particularly to the non-existence of a permitted exploder for more than six shots, and further, because permitted multipleexploders are not designed for remote firing through long lengths of cable. This situation was met by arresting or reducing progress in the production places, thereby reducing the danger of outbursts while means were being considered to achieve overall maximum safety.In August 1957 two full faces were successfully blasted in experimental simultaneous rounds. In June 1958 four full faces were blasted, and in October 1958 full face grunching without prior cutting, Le. inducer shotfiring, was introduced in No. 1 Tunnel as a production feature. In March 1960 it...

Jan 1, 1960

By Burns W. G, Muceniekas E, Whitcher I. G, Hughes F. E

No iron ore deposits were reported before 1961 from the Hamersley Ranges, Western Australia, although low-grade bedded iron formations, associated with ferruginous jaspers and cherts, were known to occur in the local Nullagine Series of Precambrian age.In January-March 1961 preliminary investigations in the area drained by the Turner River, Duck Creek and Serpentine Creek revealed the presence of over 1000 million tons of dense botryoidal or pisolitic limonite, forming flat-lying orebodies with 50-57 per cent iron.Large bedded hematitic orebodies were also discovered in the same area in August-October 1961. These have a porous, biscuity texture and an iron content of 60-61 per cent. They occur at a welldefined stratigraphic level (Brockman Iron Formation), normally in synclines where they have been upgraded by circulating meteoric waters during an old cycle erosion.In 1962 systematic geological studies and mapping, together with sampling and scout drilling, indicated larger reserves of biscuity hematitic ore and led to the discovery of massive hematite deposits at Mt. Tom Price. These were extensively drilled in 1963, proving the persistence of' high-grade mineralisation to a depth of 200 ft and over.To date the total indicated reserves of the Hamersley deposits, within the area held by Hamersley Iron Pty. Limited, are of the order of 4960 million tons and thus rank among the more important of the world. The reserves are composed of 600 million tons of bedded dense hematite ore with 64-66 per cent iron, 2900 million tons of bedded biscuity hematite-limonite with 60-61 per cent iron, 1360 million tons of limonite (goethite) ranging in grade from 50 to 57 per cent, and 100 million tons of canga (conglomerate) iron ore containing 53-63 per cent iron. In all cases harmful impurities are comparatively low.

Jan 1, 1964

Cessation of mining on the Bendigo goldfield makes it evident that, as the older generation fades away, knowledge of the famous Bendigo saddle reefs will be limited in the future by their written records. It is important therefore that the summarised account by D. E. Thomas (1953) in the Geology of Australian Ore Deposits should not be misleading. Fig. 6 in this article is stated to portray a cross section and longitudinal section through a series of gold shoots in the Garden Gully 300 ft. reef. The gold shoot along the capof the saddle reef is represented as extending down the east leg in a series of prongs, with the tips of the prongs about 50 ft. apart. It is the purpose of this note to indicate that this illustration can be suspected to be a diagram of the old stopes instead of a diagram of the distribution of gold in the quartz.The original sketches of Figs. 6 and 7 in Thomas' account were extracted, I believe, from the field note books of H. S. Whitelaw, years after his death in the late twenties. Whitelaw was stationed in the Bendigo office of the Geological Survey of Victoria, carrying out geological surveys of the Bendigo mines. He was there for many years before the Gold Research committee started its investigations in 1916 and he was acutely aware of the problem attached to the distribution of gold in the reefs. He had felt concern that manyauriferous reefs were being mined without adequate study and record and he decided, as he expressed it to me, to pick up what he could as he went along. There can be little doubt that the diagrams of Figs. 6 and 7 are products of this resolve.Opportunities to investigate gold occurrences at Bendigo were limited before 1916 because the field was operated by Manuscript received at The Institute 18th November, 1960.

Jan 1, 1961

By M Vendrup, T C. Christensen, C Dube

The adsorptive and granulate forming MetClean™ process has been used at many locations in Northern Sweden, Norway, Denmark, France, Spain, Mongolia, Japan and Australia. It has been pilot tested and used in full scale treatment plants to remove metals from:mine watersleachate from solid waste in incineration flue gasleachate from fly ash damsleachate from landfill and waste ponds.The following paper provides details of pilot and plants tests on the effectiveness of MetClean™ in removing arsenic, antimony, barium, cadmium, copper, molybdenum, nickel, radium, uranium, vanadium and zinc. Results show that MetClean™ may reduce the concentration of these metals in treated effluent water to the one part per billion (ppb) range.The paper also finds that, for specific metals, the optimal adsorption condition depends on the:pH levelmolar relation between the specific targeted metal and the addition of iron (II) or manganese (II)type of oxidation agentssalinity levelpresence of other metals.The most effective pH level varies according to the targeted metal but falls within the pH 5 to pH 11 range. A compromise pH level may be set when more than one metal is targeted for removal at the same time and through only one process step. The removal efficiency of one or both metals may be affected by operating at a compromise rather than optimum pH level.The MetClean process generates non-hazardous solid waste. Waste can then be disposed of more easily than brine or sludge.CITATION:Christensen, T C, Vendrup, M and Dube, C, 2015. Pilot tests for heavy metals removal in mine water, in Proceedings MetPlant 2015, pp 404–415 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By S Kasaneva

TheSan Cristobal gold district is located 110 km east of the port of Antofagasta, Chile. It contains the San Cristobal gold mine, where Niugini Mining Ltd. commenced a heap leach operation, with initial reserves of 10.1 million tonnes grading 1.34 g/t Au, in December, 1990. The San Cristobal district occurs within an upper Cretaceous-lower Tertiary magmatic arc. The main mineralisation occurs within a northwest trending subvertical zone, 1km long and 70 - 100 m wide, which contains rhyolite porphyry and minor breccia, and is locally termed the 'subvolcanic complex'. At the San Cristobal mine, most gold mineralisation occurs in subvertical quartz-pyrite veins which were emplaced in dilational sections of an imbricate fault system. The bulk gold resource comprises four ore shoots which formed where the vein system intersects the subvolcanic complex. Gold-bearing quartz-pyrite veins also occur at separate prospects, the Three Sisters and Sol prospects, west and south of the San Cristobal mine.   Hydrothermal alteration consists of potassic and propylitic assemblages related to intrusion of the subvolcanic complex. This alteration is overprinted by a phyllic stage which is associated with the emplacement of the quartz-pyrite veins. The oxide zone is 180 m thick, and contains native gold, electrum, limonite, and manganocarbonates. The underlying hypogene zone contains pyrite with minor chalcopyrite, sphalerite, galena, covellite, bornite, chalcocite, and arsenopyrite. Fluid inclusion studies indicate that the deposit formed at approximately 270¦C, and the mean salinity of the fluid was 4% NaCl equivalent. These observations enable the San Cristobal deposit to be classed as a porphyry- related, mesothermal quartz-vein system of the low sulphidation type.

Jan 1, 1995