Geology

Geology of the Red Dog Mine

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

Inductive Electrostatic Gradiometry IESG

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

Carlin Trend Hydrogeology

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).

hydrogeologic setting stratigraphic

hydrogeologic setting map

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

Mineral Titles Online MTO BC

Using this summary page you can locate Geological Maps from the MTO Online service in British Columbia to acquire Mineral Titles, Mining Claims.

Mineral Title means a claim or lease acquired and maintained under the Mineral Tenure Act and its predecessor Acts (the Mineral Act and the Placer Mining Act) and these are by far the most prevalent form of title to minerals. The only method of acquiring new mineral rights today requires the registration of a cell claim. A claim is an exploration and development tenure, and a recorded holder may convert a claim to a lease in order to carry out production mining. Information on the methods of claim and lease acquisition and maintenance may be viewed on the Mineral Titles Branch website. This guide deals with the rights and responsibilities of the surface owner and the subsurface mineral title holder where this subsurface right is granted by a mineral or placer claim or lease.

MTO British Columbia

bc_mineral_titles_online_https://www.mtonline.gov.bc.ca/mtov/home.do

Mineral Claim – Work Requirement in BC

$5 per hectare for anniversary years 1 and 2;
$10 per hectare for anniversary years 3 and 4;
$15 per hectare for anniversary years 5 and

Disseminated Epithermal Gold Deposits

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

Distribution of Gold and Sulfides

Lupin is located on the shores of Contwoyto Lake at lat. 65° 48’N, Long. 111° 15’W and lies about 80 kilometres south of the Arctic Circle. Since start up in 1982 the mine has produced over 2.15 million ounces of gold from 6.66 million tonnes of ore grading 10.63 gm/tonne. Total remaining reserves at 1993 year end were 5.1 million tonnes at a grade of 9.11 gm/tonne (1.65 million ounces). This is sufficient for 7 – 8 years at the present annual production rate of about 200,000 ounces. The Centre and West Zones of the deposit are open to depth.

Controls of Gold and Sulfide Distribution at Lupin NWT

Different processes have been suggested for the formation of the Lupin deposit including synsedimentary deposition of gold and sulfides, epithermal emplacement of gold, metasomatic emplacement of gold and sulfides, redistribution of gold and sulfides during metamorphism and combinations of the above. There is no unequivocal argument in the literature for any of the possibilities noted, although different authors have their own biases. The geological staff at Lupin deals with the deposit on a daily basis over long periods of time and bases their ideas and opinions to a large degree on

Estimating Weak Rock Strength

Factors Controlling the Strength of Weak Rock Masses: For the purposes of this paper a weak rock mass is defined as any rock mass in which the effective shear strength parameters are less than:

  • effective cohesion, c’ = 25 psi (0.2 Mpa)
  • effective friction angle, ∅’ = 30°

using the Mohr Coulomb failure criticism. This would be equivalent to material (refer Figure 1) having a macro sample unconfined compressive strength of less than 100 psi (approx. 0.7 MPa), a strength normally associated with soil like materials.

rock-mohr-coulomb-failure-criterion

Rock masses, with such low strengths, may occur as a result of a number of independent factors as illustrated in Figure 2.

  • Weak rock material (Figure 2.(i)

Where the sole reason for a weak rock mass strength is the low strength of the rock material it is more properly classified as having a soil like strength. An appropriate classification for rock and soil, based on simple tests, from which an estimate can be made of the uniaxial compressive strength is given in Table 1 (Jennings and Robertson, 1969). Extremely weak “rocks”, or more properly materials with a soil strength but a rock appearance, can be tested in the

Geocharacterization

Excluding economic factors, the physio-chemical parameters of ore deposits such as permeability and mineralogy constrain the application of ISM techniques to those ores that can be readily accessed by a suitable lixiviant and dissolved. The released metals must then be transported to the surface in solution. Most mineral deposits are geologically complex and evaluating their in situ mining potential in a quantitative or even a semi-quantitative fashion is a formidable task. It is important, however, to characterize the geology of a deposit as completely as possible because such information (particularly the microscopic characteristics) is vital to the successful engineering of an ISM operation.

Geocharacterization of the deposit should be carried out at all scales. Large scale studies such as the collection of major fracture and fault densities and orientations are used to evaluate the hydrologic properties of the deposit. Fluid infiltration and migration through fracture networks in crystalline rock can be modeled using these data (Neuman, 1986). The distribution of host-rock lithologies and ore bodies should be mapped in detail in order to evaluate ore reserves and to select proper well placement, and depth of injection. Small scale studies describe the mineralogy, mineral chemistry, texture, and relationships of ore minerals to

Carlin Trend Geology

Stratigraphy

The stratigraphic sequence in the Carlin Trend Geological area is Lower Paleozoic marine sediments and Late Tertiary tuffaceous sediments. The Lower Paleozoic sediments consist of the Siluro-Devonian Roberts Mountains Formation, the Devonian Popovich Formation and the locally named Rodeo Creek Formation. The Rodeo Creek Formation had previously been described in the mine area as the Ordovician-Silurian Vinini Formation, which had been thrust over the Popovich Formation along the Roberts Mountains Thrust. This is now thought to be erroneous due to the lack of structural evidence for thrusting, the gradational nature of the contact between the Popovich Formation and Rodeo Creek Formation and the presence of Mid to Upper Devonian age radiolaria and conodonts in rocks above the Popovich Formation.

The Lower Paleozoic units are a transgressive sequence of carbonate shelf, slope, and basin facies that have gradational contacts. The Roberts Mountains Formation consists of carbonaceous calcareous siltstones to fine grained sandstones. It is only found in the subsurface at depths of 1,400′ to 1,500′ in the extreme northern part of the mine area. The Popovich Formation can best be described as a sequence of dirty, limestone. It occurs at depths of 600′ to 800′ below the surface and consists

Diatomite Deposit Formation

Worldwide, diatomites occur within Tertiary to Recent lacustrine and marine sediment facies (see Table 1). Geologically, the oldest marine and lacustrine diatoms predate the effusive blooms of the post Oligocene depositional period, and are respectively found within Cretaceous and late Eocene sediments. In the U.S., marine species are found in rocks as old as the California’s Cretaceous Moreno Shales. The oldest non-marine diatoms observed in the U.S. are found as a well developed assemblage within late Eocene sediments of Wyoming.

Deposits of diatomite reflect stability of environmental and depositional conditions as well as optimum preservation environment. While depositional rates vary, typical varve thicknesses suggest yearly accumulations of no more than several millimeters of compacted sediment. Strata of significant thickness and high purity, therefore, indicate prolonged environmental conditions that favored high diatom productivity and that were free of continuous and significant elastic contribution or chemical precipitation. Geological preservation of the soft sediments requires protection from erosion, such as by overlying volcanics, and it also demands that they are not subjected to geological conditions which promote dissolution or diagenetic alteration to chert, porcelanite or quartz such as deep burial, exposure to high temperature and exposure to alkaline ground water.

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