How Are Ores Deep Beneath Earth's Surface Removed

Mineral Deposits

S.M. Gandhi , B.C. Sarkar , in Essentials of Mineral Exploration and Evaluation, 2022

2.5 Ore Torso

Generally, an ore body is an accumulation of a solid and fairly continuous mass of ore with gangue, distinctly distinguishable by grade and character from the enclosing host rocks. An ore deposit might include unmarried or several ore bodies. The ore bodies are distinguished by their shape: (1) isometric ore bodies are accumulations of mineral substances that are approximately equal in all measurements, (2) flat ore bodies—sheets, veins, and lenses—have 2 long dimensions and i short dimension. The canvass, the almost mutual shape in which sedimentary deposits occur, is a tabular body separated from other rocks by bedding planes. Veins are ore bodies formed when a mineral substance fills fracture cavities or when in that location is metasomatic substitution of mineral substances for rocks forth cracks. The airplane of contact betwixt the vein and the enclosing rocks is called the selvage. A lens is a lenticular geological trunk that tapers out markedly in all directions; its thickness is slight compared to its length. In terms of morphology, lenses and lenticular beds are transitional formations between isometric and flat ore bodies. (3) Ore bodies elongated in one direction are called ore pipes or pipes which are oval in cross-section. They form when an ore substance from magmatic melts or hydrothermal solutions is concentrated; the melts or solutions penetrate from the abyssal parts of the Globe's crust along the line where tectonic fractures intersect or along fractures that intersect easily penetrated stone strata.

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Furnishings of Mining on Surface Water

Christian Wolkersdorfer , Elke Mugova , in Reference Module in Earth Systems and Environmental Sciences, 2022

Introduction

Every ore trunk or mine type develops its characteristic effluent chemical science ( Table 1). Reasons for this are the geochemical and hydrogeochemical reactions occurring during water–stone interaction. By knowing the geological, mineralogical, and climatic background of a mine site as well as the mining method applied, offset estimates about the mine water chemistry and potential effects on surface water can be fabricated (Plumlee et al., 1999). Every bit described in the previous chapter, the concluding composition of the mine water is an interplay of diverse chemical and microbiological reactions and usually shows a loftier temporal and spatial variability. Their principles are identical at all mine sites around the world. Withal, the particulars are controlled by the site-specific conditions (Table two).

Table 2. Bolt and typical parameters impairing inland waters. EC: electrical conductivity; SS: suspended solids.

Article	pH	EC	And so_iv ²⁻	Fe	Al	Cu	Zn	U	Ra	Cl	Hg	As	N	SS
Coal and Lignite	♦	♦	♦	♦	♦					♦
Gilded	♦	♦	♦	♦				♦			♦	♦		♦
Salt		♦								♦
Iron	♦		♦	♦
Copper	♦	♦	♦		♦	♦
Lead/Zinc	♦	♦	♦				♦
Uranium	♦	♦	♦					♦	♦			♦
Diamonds		♦											♦	♦
Aggregates, Building Stones, Quarries													♦	♦
Others	♦	♦	♦	♦									♦	♦

In the absenteeism of disulfides or pyrrhotite in the host rock, (di-)sulfide weathering will not occur, and the mine water will non be acid. Notwithstanding, this does not guarantee that the mine water volition exist of good quality, every bit some elements are mobile under circumneutral or alkali metal conditions. Such examples are elevated antimony concentrations in carbonate rocks (Wolkersdorfer and Wackwitz, 2004) or zinc-enriched mine waters in carbonate-hosted lead/zinc deposits (Johnson and Younger, 2002). When neither disulfides nor (semi-)metals that are mobile under elevated pH values nor water-soluble salts exist, the mine water quality will exist within regulatory limits. In these cases, the mine water might fifty-fifty be used as drinking water without handling (Wolkersdorfer, 2008).

Because the number of working and abandoned mines is large, mining influenced water can become a brunt to humans and the surround when this water is polluted. Plumlee et al. (1999) compiled which type of ore body will very likely develop what type of mine drainage. Though their compendium is quite U.Southward.-based, it is of uniform relevance, as the geological, physical, biological, and chemical processes of mine water geochemistry are identical all around the earth.

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Costs of copper production

Marking E. Schlesinger , ... Gerardo R.F. Alvear Flores , in Extractive Metallurgy of Copper (Sixth Edition), 2022

21.3.ane Byproduct credits

Many Cu ore bodies incorporate Au and Ag (Chadwick, 2010; Kendrick et al., 2003; Supomo et al., 2008). These metals follow Cu during concentration, smelting, and refining. They are recovered during electrorefining (with some additional handling; encounter Affiliate xx) and sold. Other ore bodies comprise MoS₂ (Section xx.1) which is recovered in the concentrator and unremarkably sold. The credits (sales minus extra costs for recovery) for these byproducts should exist included in all project evaluations (Freeport–McMoRan Copper and Gilt, 2022). Sulfuric acid is also often a valuable byproduct, especially when the smelter is near leach/solvent extraction/electrowinning operations.

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Elements of exploration geochemistry

Athanas Simon Macheyeki , ... Feng Yuan , in Applied Geochemistry, 2022

ane.1.4.4 Elements dispersion in master and secondary environments

In whatever ore body, the trace elements within its minerals are never static; they are always in a dynamic state. They move from their original (primary/parent) rocks to other parts (secondary) of the ore, stone, or other materials in response to changes of natural parameters such equally Eh, pH, oxygen fugacity, temperature, chemical science, and pressure connected to the ore trunk. The process of trace-element movements is termed as dispersion; information technology is largely a weathering effect of the ore body (Gandhi and Sarkar, 2022).

If the elements movements are restricted inside the surface area where elements were formed, it is called "primary dispersion." In this instance, the size and shape of resulting dispersion halos differ significantly as an aftereffect of the various physical and chemical variables that influence passage of fluid in rocks (Kyser, 2022). Contrarily, in instance, trace elements of ore bodies and their associated principal halos are leached abroad by weathering processes to soils, overburden and vegetation they consequently generate secondary halos (secondary dispersion). Some chemical constituents of ore bodies may be widely dispersed through the agency of basis waters or surface stream systems; analysis of leap and stream waters or stream sediments may therefore point the presence of a mineral eolith from a considerable distance (Robb, 2005; Gandhi and Sarkar, 2022; Kyser, 2022).

The trace elements do non disperse in the aforementioned rate. Some are more mobile than the others and can therefore form trails of their motility (halos) much faster than the other less mobile elements. Thus metal mineral deposits are surrounded by halos of aberrant trace-element concentrations proximal to mineralized rocks. These abnormal trace-element concentrations can be found inside glacial sediments, soils, springs or stream waters, and stream sediments directly (enclosing) or indirectly connected to weathering of mineral deposits (Fig. 1.xvi).

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Geochemical Exploration

S.M. Gandhi , B.C. Sarkar , in Essentials of Mineral Exploration and Evaluation, 2022

vi.5.11 Electrogeochemical Survey

Sulfide ore bodies which are buried deep beneath the globe act equally giant batteries and the abiding measurement of specific conductance can help in delineating a target. This is gaining momentum in locating securely buried sulfide deposits. Electrogeochemistry depends on movement of ion in an electric field. In a mineral body, electrochemical dissolution happens over a huge expanse of electroactivity. According to Xianrong et al. (2008), "The process leads to elevated concentration of metallic ions in dispersion haloes surrounding a mineral torso. Nether the activity of geodesic electric field, metal ions that are not reacted or absorbed volition ultimately move upwards into loose sediments/regolith close to the surface and grade ion halos in dynamic equilibrium." A schematic diagram showing the profile in rock and regolith and the formation of ICS anomaly is shown in Fig. 6.thirteen.

At the point when an artificially generated electric field is strengthened and the supply time expands, the particles in chemical element remainder movement upwards one by one and the infinite abandoned past moved particles volition be filled by particles from next minerals in order to keep up dynamic equilibrium. An all-encompassing ionic source (mineral torso) at a depth within the range of applied electric field might ceaselessly supply cations to a cathode extractor setup at the surface and will keep on aggregating until another dynamic equilibrium is reached. The particles assembled by the extractor are sourced from both the secondary halos close to the surface and ionic halos of mineral body at depth (Luo et al., 2004, 2010). Geochemical anomalies tin can be identified for exploration targeting by analyzing ionic concentration in the extractor (www.crcleme.org.au).

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Principles of Electric Methods in Surface and Borehole Geophysics

A.A. Kaufman , B.I. Anderson , in Methods in Geochemistry and Geophysics, 2010

6.3.1 Self-Potential of Electrochemical Origin in Mineral Exploration

Suppose that an ore body with electronic conductivity is surrounded by sedimentary stone whose conductivity is dominated by ions in its water-filled pores, and that office of the body extends above the water table. The surface of the ore body below the water table is a boundary between media with different mechanisms of electrical conductivity (electronic and ionic), and a natural electrochemical reaction takes place generating an external non-Coulomb electromotive force in the form of a double layer of charge: net positive charge arises on the external surface of the ore body and is balanced by negative charge of equal magnitude on its internal surface ( Fig. half dozen.13). In a higher place the water table, the process of oxidation plays an of import role and reverses the double layer: net negative charge appears on the external surface, balanced by positive charge on the internal surface. The ore trunk, thus, acts as a natural battery. The strength of the double layer below the water tabular array depends on the mineral content of the ore body and on the concentration of ions in the surrounding fluid-filled rocks. The departure of potential across the layer can reach several hundred millivolts. Two conditions must be met to generate a steady electric field outside the trunk. The first is a variation of the dipole density along the double layer (a uniform double layer does non create an external electric field). This first condition is the reason that massive sulfide ore bodies, which usually contain dissimilar types of minerals, crusade a stiff self-potential field. The second condition for generating a steady external field is a process that continuously renews the double layer by removing stray ions created by electrochemical processes near the contact that act to neutralize the surface accuse. Oftentimes, the flow of the groundwater performs this function by carrying oxygen to the region. The self-potential field tin can be studied either by measuring the potential at observation points with respect to a fixed reference electrode, or by measuring potential differences between a moving pair of electrodes. In the commencement case, the reference electrode Northward is usually located at a large distance from the survey filigree occupied past the second electrode Thou. This method gives a direct map of the self-potential field. Inasmuch as the dipole moment of the double layer in the upper part of the ore body is directed down, the potential usually has a minimum directly above the torso (Fig. 6.13A). A map of equipotential lines on the earth's surface volition take a similar depression. The second arroyo is based on measuring of the voltage difference betwixt ascertainment points forth survey lines. In this case, the departure of potentials between two points one and 2 tin be written as

$\nabla U_{1} = \nabla U_{MN} + e_{1} - e_{two},$

where $\nabla U_{MN}$ is the voltage betwixt electrodes M and North caused past the self-potential field, and $e_{1}$ and ${east}_{2}$ are the electrode potentials. Their result can be eliminated by interchanging the electrodes and repeating the measurement, giving

$\nabla V_{2} = \nabla U_{MN} + {due east}_{ii} - e_{1} .$

The average of the 2 measurements is the desired quantity. (With an artificial current source, the influence of electrode potentials can be similarly "averaged out" by repeating the measurement after reversing the direction of the current.) Over a massive ore body, the potential can be relatively large, reaching several hundred millivolts. When the mineralization is disseminated through the rock, each clump of mineralized rock acquires a double layer, merely the net effect is usually small considering of random orientations.

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Including Actinides

M. Hoshino , ... Y. Watanabe , in Handbook on the Physics and Chemical science of Rare Earths, 2022

4.2.7 Denudation or Preservation of Ore Body

Depth of REE ore bodies is variable at different deposits (Figs. 42 and 43 ), because weathered crusts on granites have been removed by erosion. If a denudation charge per unit is high, an ore torso is rarely preserved or crops out on the surface. In contrast, if a denudation charge per unit is low, an ore body is cached deep in a weathering profile. A moderate denudation rate may atomic number 82 to ore formation in a moderate depth, and this is probably typical in ion-adsorption type deposits in southern China ( Bao and Zhao, 2008; Zhang, 1990). The weathered crusts on the Zudong intrusion in the Longnan deposits have a thin REE-leached zone with a positive Ce anomaly up to simply 0.7 m deep and a thick REE-accumulation zone (ore trunk) with a negative Ce anomaly is adult from 0.7 to 19 m deep (Wu et al., 1990). In other deposits of Heiling, Guposhan, and Huashan, the REE-leached zone with a positive Ce anomaly is thin as well (Bao and Zhao, 2008). The thin REE-leached zones suggest that they have been mostly eroded subsequently supplying REEs to the REE-accumulation zone in the lower role of the contour.

Chemical weathering is promoted past the temperate and tropical climate weather because the chemical weathering charge per unit increases with the increase in almanac precipitation and temperature (both are climatic parameters) (Gislason et al., 2009; Oliva et al., 2004; Sanematsu and Watanabe, 2022; Viers et al., 2022; White and Blum, 1995). The ion-adsorption type deposits and prospects were found in the temperate (C) and tropical (A) areas, encounter Fig. 34 (Köppen, 1936; Peel et al., 2007), because chemic weathering and degradation of REE-bearing minerals are promoted by moderate to high temperatures and high almanac atmospheric precipitation rates. Not only chemical weathering but too moderate mechanical erosion is required to preserve REE ore bodies.

Elevations of granite areas appear to accept important roles to preserve the ore bodies as well as climate considering they are closely related to denudation (erosion) of weathered rocks (Einsele, 2000). A moderate denudation rate of southern China is preferable for the preservation of weathering profiles including ion-adsorption ore bodies. Ion-adsorption type deposits in southern China were found in low hill areas (Bao and Zhao, 2008), and they are by and large present below an elevation of 550 chiliad (Zhang, 1990). On the other manus, Wang et al. (2013) summarized that the elevation ranges mostly from 160 to 400 k with some exceptions of higher hills in Dingnan (Wang et al., 2022), Guposhan (Li and Shen, 2022), and Long'an every bit summarized in Table 13. Denudation charge per unit of depression hills is compared to that of high mountains (Einsele, 2000; Milliman and Syvitski, 1992), and this likely helps to preserve thick weathering profiles of ion-adsorption ores in southern Communist china (Tabular array thirteen). Since the denudation charge per unit is controlled by both weathering and ship rates of weathered materials, and thick weathering profiles tin can be preserved where more weathered rocks tin be developed by weathering than tin can exist removed past transport processes (Einsele, 2000). Considering the well-nigh important ship processes consist of rainfall, surface runoff, and river period (Einsele, 2000), thick weathering profiles are likely to be developed in areas with moderate rainfall not to advance a ship of weathered materials but to promote chemical weathering. Southern China is located in the areas of temperate climate and the almanac temperature is a range of 18–21°C and annual precipitation is a range of 1500–2000 mm on average (Wang et al., 2022). Climates control rainfall and temperature, and they are consistent with denudation rates, which are basically equivalent to annual belch of suspended sediments from various drainage basins (Einsele, 2000; Milliman and Meade, 1983).

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Uranium resource in the Middle E and Due north Africa

Fares Howari , ... Philip Goodell , in Uranium Geology of the Middle East and North Africa, 2022

Ore types

Mineralization of the ore torso according to mineralogy and lithology tin be classified into 3 main types: (ane) Kasar type, where uranium occurs in a fine matrix as autonite, meta autonite and torbernite; (2) Tasharman type that contains large quantities of phosphate every bit dahllite and apatite, with a greater amount of carbonate than Kasar and non-existent relevant mineral uranium; and (3) Carbonate type, which is distinguished by high calcite with some apatite dahllite.

Turkish Atomic Free energy Potency (TAEK) and the MTA are withal examining whether uranium reserves in Turkey would prove profitable or not. As the reserves accept pocket-sized amounts of uranium, the mining of these reserves may not be cost-constructive. The reserves with mining costs lower than $eighty per kilogram are deemed profitable, with mining costs of the reserves in Turkey estimated to vary between $80 and $130 per kilogram.

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Environmental Geochemistry

D.W. Blowes , ... D.B. Johnson , in Treatise on Geochemistry (Second Edition), 2022

11.5.6.1 Clandestine Workings

Access to securely buried ore bodies is attained through secret mining. Workings are excavated to provide admission to the ore trunk ( Figure 4 ) and to mine the ore. These operations typically involve the removal of rock with no or little valuable metallic content. Mining and economic limitations frequently result in large amounts of residual sulfide minerals being left next to the excavated stopes. The extent of oxidation of these residual sulfides is primarily dependent on the surface area of exposed sulfide minerals and the duration of exposure to oxygen (Morin and Hutt, 1997). Afterward a mine is decommissioned, the weathering products of these exposed sulfides may become a source of acerbity, sulfate, and dissolved metals.

Many secret mines are allowed to flood shortly later mining ceases, thus limiting the extent of sulfide-mineral oxidation. In areas where the water tabular array is deep or where adits have been excavated to drain the mine workings, extensive oxidation of the wall stone may persist for years or decades after mining ends. The extent of sulfide oxidation and the quality of the h2o derived from a mine site are dependent on the duration of exposure to atmospheric O₂, the local geological weather, and the methods of mining used.

Nordstrom and Alpers (1999b) and Nordstrom et al. (2000) described the generation of extremely acidic water at the Atomic number 26 Mountain Mine near Redding, California, where a series of tunnels had been excavated to let access to deep portions of the ore body. The excavation of drainage tunnels from these sites had the effect of exposing large volumes of sulfide minerals, principally pyrite with lesser amounts of chalcopyrite and sphalerite, to oxidation. Large accumulations of secondary sulfate solids, such every bit römerite, rhomboclase, and Zn–Cu-bearing melanterite, have been observed equally efflorescences on the mine walls and equally stalagmites and stalactites (Nordstrom and Alpers, 1999b). H2o dripping from the mine walls and in pools independent extremely high concentrations of dissolved solids (up to 760 000 mg 50^{− 1} SO₄, 86 mg fifty^{− 1} Atomic number 26, and very high concentrations of other metals) and had a pH equally low as − 3.6 (Nordstrom et al., 2000; Table viii ). During dry periods, secondary minerals form within the mine workings and the dissolved metals in pools become concentrated from evaporative furnishings. Later on rainfall events, flushing of the accumulated oxidation products results in effluents that have very high-metal concentrations. The concentrations of dissolved metals associated with the Fe Mount site are much higher than those observed in drainage from other base metallic and gold mines, such as the Carlton Mine and the Roosevelt Mine in Colorado ( Tabular array viii ).

Table eight. Example of h2o chemistry observed in mine workings

	Königstein Mine ^a Groundwater in fourth aquifer	Königstein Mine ^a Unsaturated unleached blocks	Königstein Mine ^a Unsaturated leached blocks	Königstein Mine ^a Flooded leached blocks	Richmond Mine Portal ^b	Carlton Mine Tunnel ^c	Roosevelt Mine Tunnel ^d
pH (SU)	5.99	1.88	2.92	i.88	0.5–1.0	vii.81	7.69
Eastward _h (mV)	307	747	807	651	–	–	–
TDS (mg l^{− 1})	1736	12 322	3827	13 296	–	–	–
SO₄ (mg l^{− 1})	33	8220	2090	8800	20 000–108 000	1292	849
As (mg 50^{− ane})	–	–	–	–	34–59	–	–
Cd (mg l^{− 1})	–	–	–	–	4–19	–	–
Cr_T (mg l^{− 1})	< 0.002	0.97	0.072	ane.34	–	–	–
Cu (mg l^{− i})	–	–	–	–	120–650	–	–
Fe_T (mg l^{− 1})	1.51	1171	15.32	1570	13 000–nineteen 000	0.006	0.012
Lead (mg fifty^{− ane})	0.013	two.i	0.010	1.43	–	–	–
Zn (mg l^{− 1})	< 0.01	132	24	164	700–2600	0.044	0.22
Ra (Bq kg^{− i})	104 ± 7	0.520 ± 0.047	0.0073 ± 0.0016	2.74 ± 0.24	–	–	–
Th (Bq kg^{− 1})	north.a.	1333 ± 100	49 ± vi	1051 ± 95	–	–	–
U (mg l^{− 1})	< 0.02	12.3	eighteen.1	50	–	–	–

a: Königstein Mine, Germany (Biehler and Falck, 1999).
b: Richmond Mine portal, California, United States (Nordstrom et al., 2000).
c: Carlton Mine Tunnel, Colorado, U.s. (Eary et al., 2003).
d: Roosevelt Mine Tunnel, Colorado, United States (Eary et al., 2003).

At the Wismut Königstein mine, most Dresden, Germany, acidic solutions were used in an in situ leaching process to excerpt uranium from a sandstone aquifer. During mining, zones of the mine were isolated, and acidic leaching solutions were percolated through blocks of aquifer material. The residual sulfuric acrid was nerveless at the base of the block. The blocks were blasted to enhance permeability. In improver to the acrid used in the leaching procedure, acidity was released by the oxidation of sulfide minerals contained in the sandstone (Biehler and Falck, 1999). The concentrations of dissolved constituents vary in the vicinity of the mine ( Table 8 ). Low concentrations of sulfate and dissolved metals are observed in the groundwater. College concentrations are observed in the mined blocks, with the maximum concentrations observed in blocks that had been leached and flooded. Wismut plans to decommission the Königstein mine. The fate of dissolved metals and radionuclides in the flooding water is an of import factor in the development of decommissioning plans (Bain et al., 2001).

The effects of Au mining on groundwater quality was assessed at the Cripple Creek Mining District, Cripple Creek, Colorado, using field measurements of water quality, mineralogical analyses, and geochemical modeling techniques (Eary et al., 2003). The surreptitious workings were dewatered using a series of drainage adits. These adits have not been plugged, assuasive the workings to continue to be exposed to atmospheric O_ii. The Au ore occurs as disseminated native Au and is more often than not associated with pyrite. Oxidation reactions have produced low-pH atmospheric condition (pH < 3), with elevated concentrations of SO_four (> 2000 mg l^{− 1}), Atomic number 26 (> 200 mg l^{− one}), and other dissolved metals in the shallow groundwater. Deeper drainage waters are most neutral in pH (> 7) and have low concentrations of dissolved metals. The upper host rocks were depleted in carbonate minerals, suggesting the increase in pH was a result of carbonate-mineral dissolution reactions. The removal of Atomic number 26 was attributed to the formation of ferrihydrite, Mn to the formation of Mn oxyhydroxides and rhodochrosite, and Zn to the germination of Zn silicates and/or Zn substitutions in calcite. The predictions suggest that the neutralizing capacity of the rock will result in connected improvements in water quality for the foreseeable future (Eary et al., 2003).

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Sudbury nickel in a global context

Peter C. Lightfoot , in Nickel Sulfide Ores and Impact Melts, 2022

The Geophysical Signature of Contact and Footwall Mineral Systems

The geophysical signatures of contact ore bodies adult around the margin of the SIC is very evident in high-resolution magnetic surveys. The contact mineralization tends to consist of Po-Pn-Cpy that collectively yields a strong magnetic response. Moreover, the mineralization tends to comprise many fragments of mafic-ultramafic stone that contain magnetite, and occur in association with the Sublayer which contains disseminated sulfide mineralization. This combination of rock types produces a strong positive magnetic response, and the response is often amplified past the development of unusually large bodies of magnetic mafic land rock in the footwall. Collectively, these rocks provide a strong magnetic betoken that is easily recognized over known ore bodies by examining the analytic signal of the magnetic data.

Although the analytic signal of the magnetic response resolves these features very clearly, information technology mostly only maps out what is known to a depth of a few hundred meters based on drilling, only it is yet a useful guide in areas with less complete exploration. The gravity response tin also be important, but there is a range of density in the mineral systems, the SIC, and the country rocks that makes unconstrained interpretations quite difficult. For these reasons, the application of magnetic and gravity methods is often best achieved in conjunction with constraints from 3D geological models in geophysical inversion software that support possible models of the 3D distribution of stone types and mineral zones (King, 2007).

The footwall ore bodies tend to be poor in Po and they typically have bulk mineral compositions comprising Cpy>>Pn>Mill>Bn; they tend to have an social club of magnitude weaker electromagnetic response as well a weaker magnetic response relative to contact ore bodies because of both the mineralogy and the conductivity of the sulfide assemblage.

Other technologies have been tested in areas such every bit Trillabelle where the footprint of the eolith has been evaluated using iii-dimensional seismic tomography (Eaton et al., 2010 ). Likewise, a seismic traverse over the 402 Ore Body has identified a response that may be due to the mineral system or to the anthropogenic effects of mining ( Eaton et al., 2010).

The application of radio-imaging (RIM) betwixt boreholes (Stevens et al., 2000) has produced anomalies that are non ever due to the presence of sulfide mineralization, but sometimes they are drill-tested on the basis of the known association of anomalies with sulfide. As the anomalies are ofttimes institute in the footprint of mineral systems, it is not always articulate whether the successful discovery of mineralization is due to the survey or to the willingness to take a risk and drill a hole in an area of very prospective geology.

A technology that is sometimes used for regional exploration is an awarding of natural field electromagnetic methods, termed the magnetotelluric survey method (Livelybrooks et al., 1996). The interpretation of the natural field response can reverberate highly conductive sulfide but information technology can also be produced by other confounding effects such equally the channeling of the betoken by conductive stratigraphy, faults, and contacts.

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