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By R J. Goldfarb

Reduced intrusion-related gold deposits have become a new, low-grade, large-tonnage exploration target during the last decade. The best recognized examples of such deposits are recognized throughout the Tintina Gold Province of the northern North American Cordillera. Because such examples may have many features in common with orogenic gold deposits, such as anomalous Bi, W and Te, low salinity and CO2-rich ore fluids, and a spatial/temporal association with igneous rocks, confusion and controversy have now become commonplace in classification of many gold deposits formed along convergent margins. The best discriminators of IRGS are likely to be their: +        regional location in deformed shelf sequences on the inboard side of a series of accreted terranes and within terranes that also contain important tin and (or) tungsten deposits; +        local spatial association of gold ores with cupolas and contact aureoles of relatively reduced, alkaline-leaning, and volatile-rich plutons; +        post-deformational timing of gold deposition; +        extremely low sulfide content (commonly <1 vol %) of ores within igneous bodies and the outward zoning, through proximal skarns and to distal base metal-rich veins, from the causative pluton; and +        low grades (<1 g/t Au) of auriferous sheeted vein systems in pluton cupolas.

Jan 1, 2005

By R. L. Stanton

"The present contribution examines, in some detail, what appear to be the three outstanding features of the field occurrence of the conformable ""pyritic"" deposits. These are their association with fragmental volcanic rocks (and derivatives), their occurrence in sediments of near-shore formation, and their highly variable structural associations.In a recent paper it has been suggested that two such ""pyritic"" de-posits in New Brunswick may have originated as marine concentrations of volcanic base metal and sulphur compounds, and that many of their present features are the result of diagenesis, folding, and regional metamorphism. This is now put for-ward as a general explanation for the particular class of deposit considered.Such deposits should, on this hypo-thesis, be regarded quite simply as an integral part of the particular geological environment in which they occur -as a normal, though minor, sedimentarry type developed, char-acteristically, in near-shore and shelf facies of intravolcanic units formed along the margins of eugeosynclines. They should not be considered -as, for example, is required by the re-placement theory -as later features simply superimposed on a geological situation to which they are genetically unrelated. Where they are associated with folds and other structures, this may be attributed, from one in-stance to another, to mechanical migration during folding, weaknesses induced by pre-existing sulphides, and, occasionally, to fortuitousness.In the light of this postulated origin, it is suggested that the first stages in regional prospecting for deposits of this particular class should be broadly palaeogeographical. Later phases of the search should then be directed to the delineation of sedimentary facies and, finally, to the investigation of geological structure."

Jan 1, 1960

By Richard Campbell

Effective strata control, utilising fully encapsulated resin grouted roof bolts is dependent on the installed quality of the reinforcement elements. Resin based grouts are the main form of rock bolt anchorage in the underground coal industry in Australia and New Zealand. To be effective the system requires the mixing of the catalyst and mastic components of the resin as well as shredding of the cartridge that contains the resin. Over the past six years Solid Energy New Zealand Ltd (SENZ) has pioneered an extensive work programme quantifying the effects and extent of poor installation quality due to gloving, poor mixing and loss of encapsulation (Pastars 2003, Campbell et al 2003, Mould et al 2004, Campbell et al 2005 and Pastars & MacGregor, 2005). The One-Step Bolt (OSB), an innovative bolting solution designed and manufactured by Hilti Pty Ltd offers a self drilling, single pass bolting method that eliminates gloving, guarantees mixing quality and encapsulation performance of the installed product while not jeopardising the mechanical performance of the bolt. This paper details recent work undertaken by SENZ designed to understand and quantify the system performance of the Hilti OSB in New Zealand?s thick coal seam mining environments.

Jan 1, 2006

By D. A. Reynolds, J. D. Davis

"INTRODUDTION Investigations by the Bureau of Mines have shown that the carbonizing properties of splint and bright coals may differ greatly. In a study of 55 coal columns selected from representative coals of the Appalachian region, Sprunk and coworkers 10/ compared various chemical and physical properties of splint and associated bright coals. Carbonization tests in the Fischer retort at 932°F. (500°C.) showed that, except for bright coals of high oxygen content, the coke residue from bright coal was much more swollen and cellular than that from splint. ·with one exception, agglutinating values determined by the Bureau of Mines test, were lower for splint than for associated bright coal.Because sorting of coal in quantity is tedious and time-consuming, separate types have not been carbonized by the Bureau of Mines-American Gas Association (BM-AGA) test, which requires 85- to 200 pound charges. However, this method has been used to determine the carbonizing properties of samples 0f bed layers that are composed largely of either splint or bright coal.4/ In these earlier tests, which were made at high temperatures on layer samples from the Elkhorn bed, Letcher County, Ky., the splint coal yielded more coke than the bright coal, and this coke was slightly stronger than that from the bright coal. The cokes from samples with large proportions of bright coal were more cellular or porous, as were the low-temperature cokes obtained from carbonization of separated samples of bright coal in the Fischer retort."

Apr 1, 1944

By Charles B. Kenahan

The effects of ultrasonic radiation on the electrodeposition of copper-zinc, copper-cadmium, and copper-tin alloys from cyanide baths were investigated by the Bureau of Mines at frequencies of 18.5 and 38 kilocycles per second, and at acoustic intensities up to 0.5 watt per cm3. Significant changes occurred in the composition of the deposited alloys; some of these deposits were brighter, harder, more adherent, or of finer grain size than nonirradiated deposits. The irradiated deposits were also smoother and less porous, and they afforded better corrosion protection for the substrate metal in sodium chloride solution. The limiting current densities of the cyanide baths were increased by the application of ultrasonics. Anode and cathode current efficiencies also were increased, and cell voltages were lowered; the relationship of these effects to current density is discussed. Electrode potential measurements showed significant depolarization effects at both electrodes during ultrasonic irradiation. The resulting decrease in cell voltage was due chiefly to depolarization at the anode, and the anode became less passive.

Jan 1, 1967

By Elmer W. Pehrson

Minerals have played a prominent role in the affairs of man and nations since time immemorial but with the advent of the industrial revolution, expanding use of the products of the mineral kingdom became synonymous with the material progress of mankind. Individuals and business groups have recognized this fact so have been aggressive in searching for and utilizing mineral resources, with notable success. Indeed, their achievements are primarily responsible for the present Machine Age. On the other hand, until recently the body politic has failed to grasp fully the essentiality of minerals although, at times, access to mineral supplies has been an important factor in the political maneuvers of nations. This chapter is concerned primarily with the broader political and economic relationships of mineral resources to the world economy, and with the internal and external actions of nations in the field of minerals. Many factors that condition the mineral economy of regions and the world as a whole, influence the internal and external affairs of individual nations. The more important of these are: 1. The nature of man's dependence on minerals. 2. The problems resulting from the unique characteristics of mineral occurrence. 3. Geopolitical concepts. 4. Minerals and world power. Actions of individual nations affecting their mineral economy seek two basic objectives: 1. Attainment and maintenance of prosperity. 2. Military security. Other objectives may be cited but on careful analysis they become integral parts or extreme phases of the two points noted above. For example, the twentieth century aggressions of the USSR, Germany, Italy, and Japan might be considered as direct bids for world power but they also can be interpreted as exaggerated or mistaken efforts toward military security and peacetime prosperity. Similarly, trade barriers, nationalization of industries, foreign exchange manipulations, taxation, monopolistic prac-

Jan 1, 1964

By Varadajan Seshadri

Keywords: torpedo car, kinetics, physical modeling A 1:6 torpedo car physical model was built to assess the optimum refining conditions for pig iron desulfurization in the torpedo car considering the industrial parameters used in the steel plant CSBM (Companhia Siderurgica Belgo-Mineira, João Monlevade, MG, Brazil). The refining practice in this plant is through injection of a CaO-CaF2-Mg powder in the pig iron melt. Similarity between the model and prototype were established through Froude and turbulent Reynolds criteria. Mixing times were evaluated by pulse tracer addition and the kinetics of metal/slag interactions were assessed from experiments investigating iodine transfer from kerosene to water. The influence of parameters such as level of metal, gas flow rate, lance penetration, lance orientation were also evaluated.

Jan 1, 2005

By John H. Soulé

"Bureau of Mines engineers3/ examined the White Eagle fluorspar mine on September 3, 1943, and again on February 17, 1944. The examinations led to a proposal for the exploratory project upon which this report is based. The project, which was supervised by the author and P. L. Russell, was started on April 6, 1945, and completed on June 26, 1945.Geologists4/ of the Federal Geological Survey examined, mapped, and reported on this property prior to initiation of the Bureau of Mines project.In its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests. Both these branches are under the supervision of Dr. H. S. Dean, assistant director.Special acknowledgment is due to C. H. Johnson, Rolla, Mo., Division, Mining Branch; to W. R. Storms, mining engineer in charge of the New Mexico field office; and to J. H. Hedges, chief of the Tucson, Ariz., Division Mining Branch. Acknowledgment is owed, also, to Robert Trace and Howard Rothrock, of the Federal Geological Survey, for help in mapping the surface and in logging drill cores.The White Eagle claim is in the east-central part of sec. 34, T. 19 S., R. 9 W., Cooks Peak Mining District, southeastern Grant County, New Mexico. The property is reached from Deming, N. Mex. by taking the paved U. S. Highway No. 260 northwestward for 13 miles to the junction with State Route 61. State Route 61 is a graded but unpaved road and is followed northward for 8 miles to a junction with a poor dirt road, which is followed eastward for 11 miles to the mine. Silver City, N. Hex., is about 50 miles northwest of the mine and may be reached by several routes.The White Eagle patented claim was owned by L. H. Duriez of Vanadium, N. Mex., W. D. and W. A. Howard of Deming, N. Mex., Alvan N. White of Silver City, N. hex, and: Mrs. E. M. Saunders of Los Angeles, Calif. D. P. McCabe of Lordsburg, N. Mex., a former lessee, has recently contracted to purchase the property.The White Eagle claim was located about 1920 and was patented in November 1933. It was leased to Cooper Shapley of Deming, N. Mex., in July 1933; to General Chemical Co. from August 1938 to May 1940; to Antonio Cristo from October 1940 to the fall of 1942; and f is ally it passed into the hands of D. F. McCabe of Lordsburg, N. Mex., in May 1945.Approximately 25,000 tons of fluorite ere containing about 65 percent CaF2, have been mined and shipped from this property.5/ Most of this ore was mined by Cooper Shapley and the General Chemical Co. and shipped to the General Chemical Co.'s La Purisima mill at Deming. No exact data on production are available."

Jul 1, 1946

By Wolf-R. Under

For improvement of urban traffic infrastructure, the City of Amsterdam is cur­rently constructing the 9.5 km long North-South Metro line passing through the central districts of Amsterdam. Focal section of the project is the Central Station linking the NS Line with the Central Railway Station, the East Metro line, new bus and tramway terminals, ferries and individual traffic. Construction works required for the project are of high complexity and technical standards. They are executed under severe restrictions concerning programming, space, logistics, and impact on the integrity of existing buildings and structures as all existing installations and facilities have to maintain fully operational during the construction period. The paper deals with the main geotechnical features of the project and in particular with the diaphragm wall and bored pile construction at the Voor-plein and the De Ruijterkade sections of the Central Station.

Jan 1, 2006

By A. L. Mular

"IntroductionThe mining industry has made slow but steady progress toward the automation of mineral processing plants over the last 35 years. The stimulus to automate is associated with important economic and hidden benefits, so that today, the latest in instrumentation and technology is being employed.This chapter assesses the status of instrumentation justified economically, defines levels of control and certain fundamentals of feedback control loops, describes typical sensors employed in concentrator circuits, summarizes control strategies employed therein, and briefly highlights trends in integrated plant control.Current Status of AutomationAs early as 1948, the mining industry began to show interest in automation, probably because of its close association with the petroleum industry. By 1958, some regulatory control had been achieved in various sections of a concentrator, particularly in crushing circuits. Successes were attributed primarily to the reliability of sensors employed in the corresponding control scheme. By 1961, computers had appeared on the scene, initially, for data logging purposes.From 1958 to 1965, very few new control strategies had been implemented. Guidelines in vogue at this time appeared to be:- Install proven automation, unless a good instrumentation department exists at the concentrator.- Do not bite off too much instrumentation at one time.- Do not purchase on price alone; instrumentation must function in the concentrator environment.- Do not purchase automatic control equipment to be fashionable.Such guidelines were employed1 because of a lack of: (a) quantitative process knowledge, (b) reliable primary sensors, (c) initiative to try something new, (d) trained personnel, and (e) understanding that older concentrators could justify automation in many situations."

Jan 1, 1989

By Ralph van Rijswick, Erik Vlot

"Anglo American operates 18 Weir GEHO piston diaphragm pumps (PD) in the two pump stations of the 52-km (32-mile) long Minas Rio iron ore concentrate pipeline. The pipeline is designed to transport 26.5 Mt/a (29.2 million stpy) of concentrate from the mine to the export terminal at the coast.During the commissioning of the pipeline in the fall of 2014, high pressure pulsation levels were experienced, with peak-to-peak levels as high as 20 bar. Based on pressure readings it was concluded that hydraulic resonances were present in the system, which were excited by the third and sixth harmonic of the flow pulsation generated by the pumps.Based on this observation, Weir Minerals Netherlands, manufacturer of GEHO PD slurry pumps, recommended installing a phase shift controller that controls the phase shift between the crankshafts of the individual pumps, thereby minimizing the effect of the hydraulic resonances.GEHO piston diaphragm pumps and pressure pulsation analysisPiston diaphragm pumps are used worldwide to transport abrasive and/or aggressive slurries against high discharge pressures in the mining, mineral processing and power industries. The basic operating principle of a piston diaphragm pump is shown in Fig. 1.A crankshaft is driven by an external electric motor via a gearbox. The crank mechanism transfers the rotating motion of the crankshaft into a reciprocating motion of the piston. The piston displaces a hydraulic fluid, called the propeling liquid, which displaces an elastic rubber diaphragm. When the piston moves to the right, the pressure in the pump chamber drops below the suction pressure and the nonreturn valve on the suction side will open, allowing the pumped fluid to flow into the pump chamber. When the piston moves to the left, the fluid is compressed, and when the pump chamber pressure rises above the pipeline pressure, the nonreturn valve on the discharge side will open allowing a displacement of fluid into the discharge line. The main objective of the diaphragm is to isolate the piston and the drive mechanism from the abrasive and/or aggressive fluid and create a hermetic seal between the pumped fluid and the ambient environment. Piston diaphragm pumps as shown in Fig. 1 are among the largest positive displacement pumps in the world and have been produced with stroke volumes of up to 100 L (26 gal) per pump chamber for flow rates up to 800 m3/h, discharge pressures up to 250 bar and hydraulic outputs over 2 MW per unit (van Rijswick et al., 2010)."

Jan 9, 2017

By D. E. Parson, W. A. Morgan

This paper offers a brief review of current literature pertaining to vacuum degassing or vacuum casting of steel as practiced in the U.S.A., Germany and the U.S.S.R. The advantages of vacuum degassing of large forging ingots, heavy section casting, for the conversion of rimming bessemer steels to killed steel and for the production of transformer steels are discussed. Operating pressures, reduction in gas contents and improvements in hydrogen segregation, steel cleanliness and mechanical properties, obtained with the various techniques, are described. The paper includes a description of an experimental vacuum stream-droplet degassing unit and some preliminary results obtained at the Physical Metallurgy Division Research Laboratories Department of Mines and Technical Surveys, Ottawa on laboratory steel melts. Experimental 500 lb direct arc, basic melts have been spray cast into either ingot moulds or dry sand moulds, held inside a vacuum tank. Also 500 lb melts have been

Jan 1, 1961

By Robert L. de Beauchamp

The Bureau of Mines reviewed aluminum chloride technology to determine the problems associated with its preparation from minerals, and to ascertain the best areas for research to solve these problems. Commercial AlC13 production processes are described and the ?state of the art? for the preparation of AlC13 from aluminous materials is evaluated. Areas for further research are indicated.

Jan 1, 1969

By M. L. Glenn

The Bureau of Mines is conducting research on Fe-based alloys using Si and Al additions to reduce the Cr required for heat-resisting appli-cations. Part of this research is being done to evaluate alloys containing (8-10)Cr-(10-14)Ni-(0-8.5)Si-(0-4) Al to determine which of these alloys have austenitic structures, as well as fabrication properties and oxidation resistance sufficient to substitute for type 304 stainless steel. Based on initial results, an Fe-lOCr-11Ni-5Si alloy and an Fe-8Cr-13Ni-5Si alloy were selected for evaluation of oxidati.on, stress rupture, and tensile properties. Both alloys have oxidation resistance at 7000 and 8000 C that is better than that of type 304 stainless steel. The stress rupture strengths are less than that of type 304 stainless steel but significantly better than that of commercial heat-resisting steels with similar Cr contents. Yield strengths of the alloys were equivalent to that of type 304. Both alloys had high tensile strengths comparable to those of stainless steels that transform to martensite during straining (e.g., type 301). These alloys have weld-hot-cracking resistance comparable to that of type 304 stainless steel. This initial study shows that Si has potential as a substitute for Cr in stainless steels for heat-resisting applications.

Jan 1, 1984

By Michael Hughes, Selva Selvamohan, Ray Costa

"Cutoff walls are commonly used to mitigate underseepage problems for levee remediation projects. At abrupt changes in seepage cutoff wall depths there is a potential for water to flow around the back of the deeper cutoff wall leading to elevated seepage pressures on the landside that could result in exit gradients exceeding design criteria. This condition is referred to as end-around-effects and is a complex problem that requires detailed and time consuming 3-D numerical modeling to represent accurately. This paper presents a simple approach for assessing end-around-effects using the results of 2- D seepage analysis to determine if lateral extension of the deeper portion of the cutoff wall is required. This simplified approach provides a pragmatic solution to a complex 3-D problem. The presented procedure was used as part of the Feather River West Levee Project in Yuba City, California, to assess end-around-effects at 26 locations. The results showed that wall extensions of up to 100 feet were needed at only 2 locations.INTRODUCTIONAs the lead geotechnical consultant for the Feather River West Levee Project, AECOM were responsible for designing levee remediation works for approximately 35 miles of levee protecting the area around Yuba City, California, and communities to the north and south. Due to land use constraints, seepage cutoff walls were the main remediation alternative selected to address underseepage issues for the project.As part of the design review process, the California Department of Water Resources (DWR) requested AECOM to look at 26 locations along the levee alignment where the depth of cutoff wall changed abruptly from shallow to deep, or vice versa. At these locations there was the potential for seepage pressures to pass behind the deeper section of cutoff wall and stress the blanket layer landward of the cutoff wall. A condition referred to as end-around-effects.End-around-effects involve complex 3-D ground conditions that have traditionally been addressed by laterally extending the deeper section of cutoff wall an arbitrary distance based solely on engineering judgment. In discussions with DWR, AECOM developed a simple procedure to provide a more objective assessment of end-around-effects without the need for detailed and time consuming analysis. This procedure allows the engineer to make an informed decision of whether end-around-effects are a problem at the location of a cutoff wall transition rather than laterally extending the deeper section of cutoff wall an arbitrary distance based on engineering judgment alone."

Jan 1, 2015

By A. W. Jolliffee

ANY attempt to forecast the mineral resources of a largely unknown region is hazardous and, in the case of the Northwest Territories, such a task is even more hazardous than usual. This is not merely because of the immense territory involved (over a million and a quarter square miles), only a small fraction of which has ever been explored or prospected, but also be-cause both the geology and mineral deposits thus far examined show many unique features, and, finally, because the region is being actively prospected at the present time. However, in view of the present widespread interest in Canada's mineral resources, a brief compilation of what is known regarding mineral occurrences and geology in the explored parts of the far north seems timely. From these assembled data, a few inferences are warranted as to future mineral production from this region. HISTORY The story of mineral discovery in the Canadian northwest is a fascinating one. As well, it abundantly illustrates the importance of mineral occurrences in indicating future mining possibilities. The same sequence of events has repeated itself too often to be merely fortuitous.? In most cases, the dis-covery of a mineral deposit of possible economic value has been foreshadowed by the finding of the valuable mineral or an associated mineral in the same district, generally in small quantity, by an early explorer or traveller. Thus, John Franklin reported oil seepages from the base of Bear Rock, near Nor-man, at almost the very spot where oil was struck nearly one hundred years later. Again, some would-be Klondikers, deterred by the hardships of the route, remained to prospect around Great Slave lake, and were the first to report the Pine Point lead-zinc occurrences there and the gold-bearing veins on Yellowknife bay. Sporadic prospecting followed at the latter locality for over thirty years before the recent rich strikes were made. Similarly, in 1847, Dr. John Rae picked up a boulder of copper ore south of Rankin inlet, on Hudson bay. More than eighty years later, a body of copper-nickel sulphides carrying values in platinum metals was found at this locality. Also, the report of cobalt bloom on the east coast of Great Bear lake brought back by a Geological Survey of Canada party in 1900 was a factor in the events leading to the discovery of silver and radium there in 1930.

Jan 1, 1937

By MEHMET KIZIL, PETER KNIGHTS, ROYAL REA

A 1/20 scale experimental dozer push test rig was designed and constructed to quantify the expected production rates (loose cubic meters per hour) for dozers operating in hard-rock bulk push applications. The particle size distribution of the material employed in the test rig was modeled on a fragmented muckpile representative of that for a typical surface copper/gold mine overburden. Buckingham Pi theory was applied to mathematically develop factors for scaling up dozer productivity parameters, including blade loads and push times. Dozer production rates were investigated for various dozing distances and slope angles. A series of instantaneous productivity curves were produced which are applicable for use in hard-rock dozer push operations. The productivity curves produced demonstrate that dozer productivity declines rapidly over the range of 10 to 40 m.

By Francis C. Lincoln

"INTRODUCTION As part of a general investigation of the zinc-producing area of southwestern Wisconsin, the Bureau of Mines undertook a limited amount of exploratory drilling in the immediate vicinity of the New Dale Rundell mine, in the Mifflin District of Iowa County, Wisc.The work was carried out during the early part of 1945, at a time when all effort was being directed toward increasing production of metals important to the Nation's war program. Bureau of Mines engineers decided to conduct exploration at the New Dale Rundell mine after a preliminary study of available data showed a reasonable possibility of indicating an important deposit. Before the Bureau of Mines investigation, 50 holes had been drilled in the vicinity. Of this number, 18 encountered ore of minable grade. Subsequently the mine was developed and operated for a brief period; however, work was stopped before all of the ore disclosed by drilling had been mined. There appeared to be a correlation between the ore shown by the drilling in the New Dale Rundell mine and another disclosure some 1,500 feet to the northwest. The Bureau of Mines exploration was pinned to explore this possible correlation. Of the 7 holes drilled by the Bureau of Mines, 3 disclosed minable ore beyond the limits of previous drilling."

Aug 1, 1946

By M. C. Malamphy

A general description of the activities and results of bauxite investigation by the Bureau of Mines at its bauxite project in saline and Pulaski Counties, Ark., has been given in Report of Investigations 4251. The factual data obtained during the project are reported in a series of Reports of Investigation beginning with No. 4251, of which this is the eleventh. The-data are accompanied by maps showing the location of holes drilled and the deposits developed. Each area upon which work was done is reported by half townships. Each bauxite deposit investigated was assigned a name and a number for ready reference and identification, and its location and name are shown on the appropriate half-township map. The description of each halt township is followed by a description of each deposit developed in that halt township. The 14 halt-township maps and 77 detail maps of the bauxite deposits in this series at reports give the locations and numbers of all the holes drilled on the project, except the deep holes drilled to test the geophysical anomalies. The locations of those holes show on figure 13 in volume 1. The descriptions of the deposits developed are followed by complete detailed logs of the drill holes. Many of the widely spaced exploratory holes did not discover bauxite of minable thickness and grade. The pertinent information obtained tram the widely spaced exploratory drill holes has been summarized and tabulated, and a table for each halt township is given with the discussion of that area.

Jan 1, 1948

By D Craw, J Pope

The Greenland Group, Westland, can be characterised with respect to environmental issues by the application of a GIS database (DAME), and specific sampling campaigns. Waters draining gold mineralised areas have a distinctive chemistry characterised by neutral pH and arsenic as a trace element. The acid neutralising capacity (ANC) from carbonates usually exceeds the maximum potential acidity (MPA) from sulphides resulting in circum-neutral pH. These waters are readily distinguishable from waters draining coal mine related areas, which commonly have low pH (~4) and low As concentrations (~0.1 ppm). In contrast, dissolved arsenic mobilised from Greenland Group historic gold mining areas is up to 2.4 ppm. This As mobilisation is controlled by the secondary As mineral, scorodite (FeAsO2+2H2O). Maximum dissolved As concentrations increase with increasing pH, corresponding to the increasing solubility of scorodite with increasing pH. Dissolved As is attenuated by dilution, precipitation of scorodite, and/or adsorption to iron oxyhydroxide (HFO). Adsorption to HFO is an important attenuation mechanism in and adjacent to many mine sites. HFO is abundant at mine sites where pyrite was abundant in fresh rock, such as where the mineralised zone is dominated by disseminated pyrite. Pyrite, and resulting HFO, are relatively rare where mineralisation occurred as well-defined quartz veins. Localised HFO occurs also where ankerite oxidises in host rocks. Arsenic output flux (ca. 25 g/day) from historic gold mine sites is commonly less than the natural background flux from mineralised rocks (>5000 g/day).

Jan 1, 2006