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By Jeffrey C. Reid

Computer processing and high resolution graphics display of geochemical data were used to quickly, accurately, and efficiently obtain impor¬tant decision-making information for tin (cassiterite) exploration, Seward Peninsula, Alaska (USA). Primary geochemical dispersion patterns were determined for tin-bearing intrusive granite phases of Late Cretaceous age with exploration bedrock lithogeochemistry at the Kougarok tin prospect. Expensive diamond drilling footage was required to reach exploration objectives. Recogni¬tion of element distribution and dispersion patterns was useful in subsurface interpretation and correla¬tion, and to aid location of other holes. Tin was its own best pathfinder. Arsenic, also a useful pathfinder element, forms a discrete halo peripheral to tin mineralization. The arsenic halo is expressed in hand specimens by asenopyrite and/or scorodite staining.

Jan 1, 1989

By Massimo Guarascio

Computer data processing and ore reserve evaluation techniques, mainly based on geostatistical methodologies, have been developed at Agip Mining Division with the assistance of the Department of Mining Engineering of the University of Rome. A number of computer programs are available when facing problems such as optimization of sampling patterns, minable reserve estimation, grade control of output, and so on. In the present paper, the aims and the criteria followed in developing these programs are discussed. Some recent examples of application are also cited.

Jan 1, 1977

By L. Maday, V. J. Perrone, M. B. Gilbert

INTRODUCTION The Brightwater conveyance system project in King County, Washington consists of constructing about 21 km (13 mile) of effluent and combined influent and effluent tunnels. The influent tunnels will collect sanitary sewerage from the service area and convey it to the new wastewater treatment plant (WTP) site at Route 9 in Woodinville, Snohomish County, Washington. The effluent tunnels will convey treated effluent from the WTP to an outfall at Puget Sound. The tunnels will be constructed primarily under residential areas, busy suburban roads and state highways. This 21 Km (13-mile) soft ground tunneling project faced many design challenges because of the geologic and hydrostatic conditions, long tunnel reaches, and large overburden depths. Boring depths typically varied from 45.7 M (150 ft) to 114 M(375 ft) with a maximum depth of 185.6 M (566 ft) deep. Conventional empirical methods for non-mountain terrain based on a 1:1 ratio of drilled footage per foot of tunnel bore (National Research Council, 1984) for evenly spaced borings provided a good start for the Phase 1 explorations. However a continuation of this approach with closer spacing was deemed inadequate by the geotechnical team for efficiently allocating geotechnical exploration resources for the final design. This paper presents a rational approach that was used to evaluate the value of a particular geotechnical exploration boring, pump test or other in-situ test. The method of analysis, which was initially developed for rock tunnels (Einstein et al., 1978), was modified for the Brightwater project. The method considers the potential construction cost risks resulting from variable geologic conditions, the cost and reliability of the geotechnical exploration and the earned value (cost risk reduction) of performing the geotechnical exploration. PROJECT DESCRIPTION In total the land portion of the conveyance system will include approximately21 Km (13 miles) of tunnels ranging in size from 3.0 to 5.2 M (10 to 17 ft) minimum inside diameter with overburden depths of 30.0 to 168 M (100 to 550 ft) and

Jan 1, 2005

By Arthur A. Brant

Your chairman has asked me to deal with questions of education relative to our present and projected trends in the field of mineral expiration. First comes our definition of education--and education is not the merely formal acquiring of academic knowledge, but the understanding, using and projection of knowledge into our channels of life and thought activity. This past year makes us realize the extent to which price and economic cut-off may stimulate or curtail exploration,, But exploration does not consist solely in the discovery of sources of material. There is just as inspiring and imaginative a territory in the develop¬ment of uses and application--and no one in our base metal industry but would hope that our educational processes would fertilize those springs of inspiration that lie dormant in us all, toward the- imaginative conception of new uses--lead roofing cloths or felts, non-tarnishable copper utensils, further zinc solid state application. Thus an educational pattern should seek to develop imagination and thinking beyond--the possibility of that small but oh so difficult step just ahead of the existing,

Jan 1, 1959

Chile, which hosts around 30 per cent of the worldÆs copper resources, is now the largest producer and exporter of copper. Chilean copper output accounts for more than one-quarter of total worldwide production. An increase to around 40 per cent is forecast by the end of the century. In addition, Chile ranks eighth in silver production and 11th in gold output. In Chile, mining generates more than eight per cent of the countryÆs GDP and the total value of mineral exports is more than US $7.85 billion corresponding to more than 25 per cent of South AmericaÆs mineral production. The rate of growth of Chilean mineral production is indeed impressive. Table 1 shows that in the period 1969 - 1998, copper annual production increased 564 per cent from 667 000 t to 3 764 000 t. Gold production went up 27 times from 1827 to 49 770 kg. Silver output grew 1219 per cent from 95 650 kg produced in 1969 to 1 166 380 kg in 1998. Several facts explain this dramatic increase of production, but the most important was the success of exploration sustained over the same period. This resulted in the discovery of several world-class deposits which when developed into mines, account for much of the production increases. Therefore, this summary review shows the success of basic exploration carried out during the last 30 years in the Chilean territory. The review is based on data already published in different specialised mining books or magazines. It only includes those world-class discoveries not the lesser discoveries important at local scale. All figures were calculated using 1998 $US dollar and average estimated metal prices valid for 1999: copper $US 1653 per t ($US 0.75 per pound), gold $US 9452 per kg ($US 294 per ounce) and silver $US 177 per kg ($US 5.5 per ounce).

Jan 1, 1999

By Loris S. Pascoli

The increased pace of globalization in the mining industry has presented more opportunities for Canadian service companies to participate in ventures abroad. However, varying cultures, laws, competitive environments and contracting philosophies in other countries make it impossible to take for granted what is normal in the Canadian context. The author discusses some of his experiences and situations encountered in over 30 years in the diamond drilling industry, the last third of which were primarily focused on projects outside of this country.

May 1, 2001

By D. C. Carter, J. P. Anderle

"Exploration drilling of evaporite sequences in eastern Canada has undergone significant changes in equipment, techniques and philosophy since the early 1970s. The result has been the recovery of full-size cores from properly conditioned and stabilized holes, high quality open hole geophysical logs, and high quality metallurgical samples. The majority of modifications have resulted from the necessity to preserve the integrity of the evaporite deposit, and thus ensure the potential development, combined with the need for cost-effective high quality information. This is particularly evident in the priority placed on the development of non-erosive drilling fluids, casing and cementing procedures. The results are applicable to diamond drilling exploration of evaporite deposits anywhere in the world.IntroductionThe majority of current technical and scientific literature and expertise available on such subjects as drilling fluids or cementing procedures is applicable to large diameter, deep (several thousand metres) oil-field type drilling . The differences between oil-field drilling and wire-line core diamond-drilling are dramatic: large diameter, deep holes drilled with a low rpm tricone bit using large volumes of fluid pumped through a large annulus versus small diameter, shallow (less than 600 m) holes drilled with a high rpm diamond-set core bit using small volumes of fluid pumped through a small annulus. Exploration drilling of evaporite sequences in eastern Canada in the early I970s was conducted using oil-field equipment and techniques to complete holes of moderate (1000 m to 1500 m) depth . The prohibitive cost of these operations has necessitated that subsequent exploration drilling employs modified diamond-drilling equipment and techniques developed as part of a transition away from oilfield methodology. The result has been full size core, recovery approaching 1000/0 and the ability to run open hole geophysical logs; a combination of factors enhancing the collection of high quality information (Carter, I989a)."

Jan 1, 1990

By Edgar A. Scholz

The purpose of this paper is to make a comparative cost analysis of domestic and foreign exploration projects which developed into mines during the 1960-1974 time period. A total of 18 mining companies, American and Canadian, were approached to solicit cost data on domestic and foreign exploration projects which developed into mines. Only 20 percent of the companies to which questionnaires were sent made data available. Several companies answered negatively, informing us that they would have difficulty in attempting to sort our costs. Some companies were usable to release cost details. It is comforting, however, to realize that some of the non-contributing companies expressed eagerness to hear the findings of this paper. Inasmuch as the data available on exploration expenditures is, in some cases, somewhat uncertain and that no two mining companies follow the same system of cost allocations, the results obtained in this analysis should he interpreted as trends of a general character.

Jan 1, 1976

By Russell Webster

In having maintained production for more than 40 years Arizona's Magma mine is unique in a mineral district that includes several major copper mines. Other past and present producers in this area are Miami and Inspiration at Miami, the Old Dominion in Globe, the Ray mine in Ray, and to the south the new San Manuel mine near Tucson. Magma's production of copper, silver, gold, and some zinc has come from nearly parallel east-west striking mineralized faults, one called the Main or Magma vein and the other the Koerner vein, about 1100 ft to the south. This vein system has been prospected and partially mined for some 9000 ft horizontally and 4800 ft vertically. In ascending order from the deepest exploration level, the Main vein cuts Pre-Cambrian schist, Pre-Cambrian Apache Group, Post-Devonian diabase, and Devonian, Mississippian, and Pennsylvania limestones. Until 1950 very little ore was obtained from replacement mineralization.

Jan 10, 1958

By John S. Cummings

In this paper the phrase "exploration for blind metal deposits" refers to exploration activities geared to the discovery of metal deposits which cannot be located by visual surface inspection. The word "system" refers to all of the components (people, money, corporations, techniques, etc.) which collectively result in an exploration process. The details of the system or systems which I have employed in exploration will not be discussed because of client relationships. However, some of the more severe problems in exploration result from how the system's components interact and our attitudes as to what exploration data is telling us, if anything. It is these items which will be discussed. Exploration for blind metal deposits, which has been relatively intense over the last 2S years compared to rather minor outlays prior to World War II has often been an uncoordinated assortment of various specialists employing various techniques (see Dickerson -1). In a program geared to the location of blind deposits, the lack of outcropping deposits or occurrences should not be a deterrent to a well conceived and well planned program. The severe cyclical swings in exploration activity, although often coinciding with depressed metal prices, by and large result from the failure of exploration operators to present a coherent and realistic program to management. It is my opinion that the stream of complaints criticizing management for cyclical exploration support are mostly unwarranted, as many of the programs and goals are ill defined. Although depressed market conditions may serve as the catalyst for exploration cuts, the underlying cause is that when the "chips are down", the non-directional, non-specific nature of many programs is revealed. Thus management should not be castigated for eliminating such programs during bad times, but rather they should be castigated for supporting them during boom periods.

Jan 1, 1978

By Theodore H. Eyde

The porphyry copper province of the southwestern United States and northern Mexico, is the largest copper producing region in the world. Most of the deposits occur in Arizona which now produces over 54% of the newly mined copper in the United" States. As the many recent discoveries are brought into production, Arizona's share of the nation's copper production will increase. The term "porphyry copper" as used in this paper includes all deposits of generally low grade disseminated copper mineralization amenable to bulk mining techniques. Therefore, copper deposits such as Pima-Mission, Twin Buttes, and Vekol where the copper mineralization occurs principally in the intruded rocks will be considered as "porphyry copper" deposits. Most of the deposits have been discovered since World War II, consequently, the southwest, and particularly southern Arizona is perhaps the most intensively explored area for copper deposits on earth. Most of the major natural resource companies in the United States and Canada maintain exploration offices in southern Arizona. To illustrate the success of exploration efforts, the location of porphyry copper deposits either known or producing prior to World War II are shown on figure 1 and the deposits discovered since World War II which are either in production or in the exploration and development stage are shown on figure 2.

Jan 1, 1973

By Theodore H. Eyde

The porphyry-copper province of southwestern United States and northern Mexico constitutes the largest copper-producing region in the world. More than 20 deposits discovered since World War II are being exploited or in the process of exploration and development. Because of the remarkable success in discovering new deposits, exploration activity continues at a very high rate and deeper targets are explored each year. Exploration programs for deeply buried porphyry-copper deposits require a reevaluation of the conventional exploration techniques. Though surface induced-polarization techniques have about reached their practical detection limit, aeromagnetics will play an increasing role in the exploration activity as will downhole logging tools. In addition to a valid geological concept, any successful exploration program for porphyry-copper deposits in the southwest must have two other essential ingredients: money and guts. Unfortunately many exploration programs in the southwest are underfunded and doomed to failure. Future exploration will demand more joint venturing in which larger and more expensive exploration programs can be successfully funded by groups of companies or syndicates.

Jan 1, 1975

By Ted H. Eyde

Nearly 17 years ago a major producer of synthetic zeolites started an extensive exploration program for natural zeolite deposits which resulted in the discovery of over 170 occurrences in the western United States. A few years later several of the other producers and consumers of synthetic zeolites also started similar exploration programs. Since then, small quantities of natural zeolite minerals have been produced from at least 12 deposits in the United States. Of these the Bowie deposit, about 13 miles north of Bowie, Arizona, is the most important,having produced over 5,000 tons of vitric tuff zeolitically altered to the mineral chabazite and minor amounts of the minerals erionite and clinoptilolite. Mining Districts and Mineral Deposits of Arizona compiled by Charles A. Mardirosian, Consulting Geologist, estimates the value of the total production from the Bowie deposit at a very conservative $2,000,000. Unfortunately, none of the companies responsible for the discovery and the initial production of natural zeolites made any effort to develop the high volume, low cost applications of this unique mineral raw material. Instead, they developed only the high unit value uses to supplement their existing synthetic molecular sieve product lines. With the producers of synthetic zeolites thinking in pounds and not in tons, further development of natural zeolite deposits stagnated for over a decade.

Jan 1, 1974

By W. Dan Hausel

In previous reports by Hausel et. al., (1979 a, b, and c), Leighton and McCallum (1979), and McCallum (1974;1979), several exploration procedures were examined as to their effectiveness in locating kimberlite intrusives in northern Colorado and southeastern Wyoming, where approximately 90 kimberlites have been recognized within 5 districts (Figure I). Briefly, geological mapping and stream sediment sampling for indic- ative heavy minerals of kimberlite (pyrope garnet, chrome diopside, and magnesian ilmenite) proved to be the two most effective methods in isolating kimberlite occurrences within the granitic terrain of Colorado and Wyoming (Hausel et. al., 1979 a, b, and c; Leighton and McCallum, 1979). Where a kimberlite intrusive is deeply weathered, remote sensing using color and color infrared aerial photography may be a potential reconnaissance tool in kimberlite exploration. The kimberlitic eluvium supports thicker grassy vegetation, and at least one species of grass (the Bluebunch Wheatgrass) is found to grow only within the eluvium. The result is that vegetation in the kimberlitic eluvium is a better infrared reflector than the vegetation in the surrounding granitic soils (Hausel et. al., 1979 b; McCallum, 1974

Jan 1, 1980

By R G. Barker, A B. Christie

"An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation. More than 11 Moz of Au and 50 Moz of Ag have been produced from epithermal deposits in New Zealand, almost entirely from 50 deposits in the Hauraki goldfield. Since the 1980s, new deposits have been discovered at Waihi (Favona, Trio, Correnso) and nearby at Golden Cross. Feasibility studies into reopening the Talisman mine at Karangahake are continuing, and advanced projects with preliminary inferred resource estimates are reported at Wharekirauponga, Neavesville and Muirs. In the Taupo Volcanic Zone, 11 prospects have been drilled, resulting in the definition of large but low-grade Au-Ag resources at Ohakuri. In Northland, several Au, Ag and/or Hg prospects are known, and small quantities of Ag and Hg have been mined. Six prospects have had some drilling, with the most advanced exploration at Puhipuhi. The application of Taupo Volcanic Zone geothermal systems research to the modelling of former hydrothermal mineralising processes in some epithermal prospects has enabled better targeting of exploration.CITATION:Christie, A B and Barker, R G, 2015. Exploration for epithermal gold deposits in New Zealand, in Proceedings PACRIM 2015 Congress, pp 533–540 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 18, 2015

The decrepitation technique is a rapid means of measuring abundances, temperatures and to some extent the fluid compositions, of fluid inclusions in transparent and opaque minerals. The method has been used to investigate the hydrothermal fluid systems associated with gold mineralisation in the Tennant Creek, Pine Creek and Halls Creek Goldfields. At the Enterprise Mine, Pine Creek, several different stages of quartz veining are distinguished and within these, gradational changes in fluid temperatures and compositions help to define the centre and nature of the thermal system responsible for the mineralisation. In the surrounding Pine Creek region and at Tennant Creek and Halls Creek, the results were applied on a regional scale to characterize outcrops and aid in the discrimination between potentially mineral- ized and barren outcrops. The decrepitation method involves the heating of a small (lgm) sample of crushed and sized grains up to as high as 800 degrees celsius. During the heating the fluid inclu- sions within the grains develop sufficient internal pressure to physically burst, the temperature of such bursting being dependent on the type of fluid and the prevailing tem- perature at the time the inclusion was originally trapped. The resulting tabulation of the number of inclusion bursts per 10 degree temperature interval is plotted as a histogram of decrepitations versus tempera- ture and called a decrepigram. The decrepi- grams frequently show several distinct peaks at different temperatures which are caused by different populations of inclusions in the sample. The areas of the peaks indicate the abundances of inclusions in each population while the shape and mean temperature of the peak provides a guide to the type of fluids involved. Of particular importance in this study is the presence of decrepitation peaks at fairly low temperatures (around 2000 C. These are characteristic of C02 rich fluids which build up internal pressure very quickly when heated. The Enterprise Gold Mine at Pine Creek comprises a number of overlapping quartz vein systems hosted by Burrell Creek Formation sediments. The geology of this mine has been described at this conference by Dann and Delaney, who have defined several distinct stages of quartz veining based on structural, mineralogical and physical features of the veins. For this decrepitation study, 19 quartz samples from the mine and environs, including some from each stage of veining were collected. These results suggest that there are 4 major vein types, within 3 of which additional small variations can be discerned which are due to gradational changes in the temperatures and fluid compositions in the mine area.

Jan 1, 1984

By Gerald M. Ellis

Exploration for gold .deposits on Hispaniola has taken place sporadically over the years but has expanded in the past decade. There are veintype, disseminated, alluvial and elluvial deposits. Investigations were previously undertaken in Haiti by combined Haitian, Bureau of Mines, and UN geological teams at Grand Bois Limbe(Milot) and Cap Coq areas. Later studies were conducted at the Miches and Moncion districts. Gold occurrences were reported in quartz, silicic-barite veins and gossans. An important deposit ?at Pueblo Viejo is? a disseminated type where extraction is taking place in the oxidized zone. Exploration by Japanese and West German firms with local geologists are described in this paper together with Pueblo Viejo, Miches, Restauracion, Milot, and Meme ?areas where occurrences are known. Copper deposits with associated gold va1ues are also described. These include vein deposits in Central Cordillera and disseminated deposits at Terrier Rouge and Blondin.

Jan 1, 1989

By R. Mittler

Over 100 saprolite samples from Turkey Hill Gold Mine, Lumpkin County, Georgia, were analyzed (-80 mesh) for As, Au, and Sb. Maximum values are 16.2 ppm As, 7.9 ppm Au, and 29.1 ppm Sb. Results show trace element content of saprolite varies with topography: ridge top samples show a pronounced decrease in Au and Sb, and to a lesser degree in As, whereas, slope and valley samples have anomalous Au and Sb concentrations, with no discernable pattern for As. Statistical analysis shows strong correlation between Au and Sb and none between Au and As. This study will serve as a model for gold exploration in deeply weathered terrains with variable relief.

Jan 1, 1987

By Lou Covello

Bow Valley Industries Limited i conducting an on-going exploration program for gold in Archean, turbidite-hosted iron formations near the Lupin mine on Contwoyto Lake, orthwe t Territorie . Exploration philosophy and practice are modelled on the Lupin deposit where 70% of the gold occurs within laminated pyrrhotitechert. sulphide facie iron formation. Thi i intimately associated with barren to low-grade silicate facie iron formation which i enclosed by predominantly argillaceou meta ediment . This type of mineralization i amenable to exploration through an integrated program of geological and geophy ical surveying, consisting of the following: i) Geological urvey both regional and local to outline area of turbidites and a ociated iron formation. Structural and tratigraphic trends documented during this phase are useful in determining eventual grid configurations. Grids are then mapped and ampled at 1:2000 cale. ii) Magnetometer and gradiometer urvey at the ame scale define strongly magnetic diabase dyke and erratically magnetic portions of iron formation. iii) VLF-EM survey are u eful in outlining conductive trend invariably as ociated with sulphidic or graphitic phase of iron formation. iv) Geological updating and ampling of iron fom1ation based on the geophysical su rveys. This is necessary for the production of a final geologic map and a an adjunct to drill target election. In problematic instances self-potential urveys have documented the pre ence of non-conductive sulphide accumulations, and horizontal loop EM surveys have been used to determine conductor geometry and quality. Target selection is based on a synthesis of the information from all of the above surveys with the results of no single survey being critical to drill decisions. The program is designed to provide first-pass, detailed , cost-effective ground coverage of large areas of highly prospective geology.

Jan 1, 1986

By William K. Brown

Are the results of an exploration program worth the cost? This is a question I suspect many of you are familiar with and, theoretically at least, it is an easy question to answer. The answer, of course, lies in comparing the future earnings stream the program is expected to generate, to the present value of the cost of carrying it out. While historical costs can be determined without much difficulty, estimating the value of a future earnings stream involves all sorts of assumptions regarding future costs, metal prices, inflation rates and an appropriate discount factor; and in the context in which the question arises, requires additional assumptions about mineral deposits which have yet to be discovered. As a practical matter, this kind of approach isn't likely to produce a very convincing answer; certainly not one convincing enough to satisfy a skeptical audience; nor one likely to temper the illusions of recent converts to mineral exploration, who are convinced that if enough money is spent, profitable discoveries will inevitably follow. Within broad limits, however, I believe it is possible to analyze the costs and results of gold exploration in the U.S.A. over the past 20 odd years in a useful manner. And while such an analysis is imperfect, it will provide some insight into this fascinating subject.

Jan 1, 1983