The Louvicourt deposit is proving to be a very large one. Reserves now stand at approximately 30 million tons and, more importantly, the deposit contains some impressive widths of exceptionally high grade Cu-Zn-Ag-Au mineralization that should ensure its profitability in virtually any future metal price scenario.

Regional Setting

The Louvicourt deposit is located approximately 15 miles east of Val d’Or, and just one-half mile north of provincial highway 117 that links Val d’Or with Montreal. The deposit lies within a one-mile wide unit of felsic volcanic rocks that strikes east-west over a distance of at least 25 miles. This unit hosts numerous important copper-zinc massive sulphide occurrences, including four past-producing mines; the East Sullivan, Golden Manitou, Dunraine and Louvem mines. These four mines collectively produced over 30 million tons of Cu-Zn massive sulphide ore at the average grades listed in Table 1. However, despite these significant production figures, Val d’Or has generally not been recognized as an important base metal camp, and the announcement of the new discovery at Louvicourt came as a surprise to many industry observers who regarded Val d’Or strictly as a gold producing camp. (Of course, this was not without good reason as Val d’Or has

Carbonates are a very rare and volumetrically insignificant family of igneous rocks composed mainly of carbonate minerals, and normally are described in terms of their habits (intrusive) and composition (mineralogy). No other association of igneous rocks exhibit as great a diversity of rock types and intrusive habit. They vary in shape and size with depth as well as the completeness of differentiation, so that differences in the internal structure, habit and compositions of associated (co-genetic) rocks, as well as the type of metasomatic alteration (fenitization) with the country rock should be exposed with the depth of erosion level since emplacement.

Morphology of Carbonatite Complexes

1. Core carbonatite, in which (a) a carbonate-rich core is surrounded, in part or completely by, (b) cone-sheets and/or ring- dikes in the intermediate, outer, and fenite rings (aureole) of the complex, and (c) radial, tangential and irregularly distributed dikes within the complex, in the fenite aureole or at some distance into the country rocks. A variant of the above is the carbonatite that occurs only as arcuate dikes (ring-dikes and/or cone-sheets), and breccia zones in alkali ring complexes. These probably represent an unroofed core carbonatite.
2. Some carbonatites occur as a thick sheet and tabular to
   

The Grasberg copper-gold orebody is contained with a young igneous complex of dioritic composition which intrudes limestones of the Tertiary New Guinea Group. Alteration is typical of porphyry copper deposits worldwide except that higher grade primary chalcopyrite with significant gold values is associated with a centrally located zone of strong quartz stockwork.

The Grasberg was generally regarded as a 0.7% porphyry copper target with little or no chance of having an enriched chalcocite blanket. The leached capping appears weak and the general area has been glaciated within recent times.

Regional Geology

The island of New Guinea has long been recognized as the product of collision between the north-moving Australian plate and the southwest-migrating Pacific plate. Convergence and deformation of the northern edge of the Australian plate probably began during Eocene time. The resulting geologic and physiographic features of New Guinea, and especially Irian Jaya, can be divided into three distinct geotectonic provinces: (1) southern coastal plains, (2) central mobile fold belt, and (3) northern Pacific plate margin.

Undeformed

Rare earth element (REE)- and gold-bearing breccia pipes are a potentially significant economic target in the Pea Ridge iron ore mine, Washington County, Missouri. The Pea Ridge deposit is one of eight known volcanic-hosted iron ore deposits in the Middle Proterozoic St. Francois terrane, which are similar to the Olympic Dam-type deposits of Australia. Total REE oxide content of samples of the groundmass material, which are not diluted with lithic fragments, average about 20 weight percent. Grades from working faces in the mine are lower and average about 12 weight percent. Gold distribution is erratic, but concentrations are as high as 371 parts per million.

Geologic Setting

Middle Proterozoic rocks of the St. Francois terrane, which includes rhyolitic ash-flow tuffs, lava flows, and coeval granitic plutons, host Missouri’s Precambrian iron ore deposits. Zircons from the granites have yielded U-Pb isotopic ages of 1,480 to 1,450 Ma. The central plutons have distinct accessory minerals, such as fluorite, topaz, allanite, monazite, garnet, and cassiterite, and a characteristic trace element suite that includes elevated abundances of Sn, W, Nb, Y, Be, Li, Rb, Ba, and F. The central plutons have a unique negative magnetic anomaly signature.

Concentrations of minerals between 3.5 and 5 specific gravity such as ilmenite, rutile and zircon in large accumulations of sand constitute “heavy mineral” placers. Two fundamentally different modes of formation characterize “trap” and “bed” placer variants. Smaller and generally higher grade trap placers form during sediment erosion or reworking. Because of their smaller size, they rarely yield economic heavy mineral deposits.

Trap and Bed Placers

Fundamentally, a trap placer is one where the higher specific gravity grains have become caught in a manner similar to gold in a riffle box. Once deposited, the grains of greater specific gravity fail to become entrained and to move away with subsequent fluid flows as do the other grains. A critical point to make here is that erosion and failure to entrain occur sometime after the grains first were deposited. Trap placers, unlike the sluice box, are characterized by later reworking of the original sediment and passive collection of grains that are essentially not displaced by the later fluid flow.

Trap placers quite often exhibit high grades. They also often exhibit wide particle size discrepancies between the matrix and the heavy minerals. Great care should be taken when identifying by using such internal evidence, however,

Red Dog is a Mississippian to Permian aged sulfide deposit located in the western Brooks Range north of Kotzebue, Alaska. It belongs in the family of black shale hosted sedimentary exhalite deposits but lacks classic sulfide sedimentary textures. Pervasive silicification, and a significant portion of the mineralization, is replacement in nature. An extensive feeder vein system cuts the footwall and the exhalite package. A Jurassic to Cretaceous age compressional event has repeated the ore section through thrust faulting and folding. The orebody contains 77,000,000 metric tons averaging 17.1% Zn, 5.0% Pb and 82 g per metric ton of Ag. Weathering has locally altered the sulfides to sulfates and formed elemental sulfur.

The Operation

An open pit is used with an expected annual production of 1,506,088 metric tons of ore per year. The overall strip ratio is 0.9 to 1.0 waste to ore.

Benches are 7.6m high with pit slopes of 1 to l in ore decreasing to 2 to 1 in waste. Expansion of the pit will ultimately require the diverting of Red Dog Creek.

Because of the high grade and low stripping ratio the mine’s tonnages and the equipment fleet are relatively small. Two Driltech D40K blast hole drills are used

IESG is an inexpensive but valuable component of our interdisciplinary integrated effort to discover and to understand hydrothermal convective plumbing systems, with originally hot, reducing, upward-flowing components yielding present negative IESG anomalies, and with originally cold, oxidizing, downward-flowing components yielding present positive IESG anomalies. This technique should facilitate the meaningful sampling of subtle Carlin-type invisible gold deposits, in another region (Basin and Range) of rift-related ores.

IESG Empirically Learned and Tested

Literature perusal revealed a wide spectrum of explanations including the religious, irreligious, psychic, and physical, but none seemed to correlate with all the observations which I had already made at mines. The most promising approaches appeared to be in classical physics, with some aspect of magnetism, electromagnetism, or electricity.

In 1949 in a major tome on dowsing, Tromp showed that a moving human body is comparable to a moving electrically charged body, and that as such a body approaches a conductor, capacitance increases and human skin potentials decrease. Also, Tromp suggested that the moving human is a charge in motion (a current) which therefore creates a magnetic field. In 1968, Tromp reported on the correlation between magnetic fields and cardiograph (human skin potential) readings. He also showed dowsing reactions in

Gold extraction along the Carlin trend requires large withdrawals of ground water, which can be perched, unconfined at shallow depth, and (or) confined at depth. Five hydrogeologic units—Quaternary basin-fill sediments, Tertiary basin-fill sediments and sedimentary rocks, Tertiary volcanic rocks, Devonian to Ordovician siltstones, and Devonian to Ordovician carbonate rocks—form the framework for two aquifer systems that discharge along some reaches of the Humboldt River and its tributaries and are recharged by streamflow along other reaches. Groundwater withdrawals eventually could affect these stream-aquifer interactions.

Regional and Hydrogeologic Setting

Active gold mines along the Carlin trend are in three large areas tributary to the Humboldt River. The South Fork of the Humboldt River and its tributaries drain a large area south of the river (hereafter called the South Fork area). Two large areas north of the Humboldt River are drained by Maggie, Marys, and Susie Creeks east of the Tuscarora Mountains (the Maggie Creek area) and by Boulder Creek on the west side of the mountains (the Boulder Flat area).

A fraction of high-altitude precipitation in mountainous areas (1,800-3,400 m above sea level)

Epithermal gold deposits occur in and near the marginal fault that circumscribes the Goldfield, Nevada, Tertiary caldera. The gold occurs disseminated in alunite, pyrite, and kaolin- bearing silicified zones that are controlled by the circular faults. Other Tertiary calderas (i.e., Summitville and Red Mountain No. 3) have epithermal disseminated gold deposits located in and near their marginal circular faults in settings that resemble the Goldfield example.

Geologic Setting of Goldfield, Nevada

Goldfield, Nevada is perhaps the best documented of the three districts. It is a Tertiary volcanic center that sustained a major mineralizing event at about 21 m.y. B.P. The volcanic rocks and the underlying pre-Tertiary plutonic and metasedimentary rocks of the district are extensively altered. Ashley and Keith (1976) show that the Goldfield district is mostly a 0.5 square mile mineralized area near the town of Goldfield, but that argillic alteration extends for about 15 square miles. Within the altered area, lying just east of Goldfield, is a complex circular feature that is about 5 miles (8 km) wide.

Precious metal mineralization occurs with some tabular silicified “ledges” composed of microcrystalline quartz, primary alunite, pyrite, and kaolinite. These developed adjacent to fractures and in breccias.

Gold mineralization appears within silicified zones