Ores and Gangues

7/30/2019 Ores and Gangues

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- Economic geology is concerned with earth materials that

can be used foreconomic and/or industrial purposes.

- These materials include precious and base metals, non-

metallic minerals, construction-grade stone, petroleum, coal

and water.

- The term commonly refers to metallic mineral deposits

and mineral resources.

- The techniques employed by other earth science

disciplines (such as geochemistry, mineralogy,geophysics, and structural geology) might all be used to

understand, describe, and exploit an ore deposit.

Economic Geology: Introduction and scope
http://en.wikipedia.org/wiki/Geochemistryhttp://en.wikipedia.org/wiki/Mineralogyhttp://en.wikipedia.org/wiki/Geophysicshttp://en.wikipedia.org/wiki/Structural_geologyhttp://en.wikipedia.org/wiki/Structural_geologyhttp://en.wikipedia.org/wiki/Structural_geologyhttp://en.wikipedia.org/wiki/Structural_geologyhttp://en.wikipedia.org/wiki/Geophysicshttp://en.wikipedia.org/wiki/Mineralogyhttp://en.wikipedia.org/wiki/Geochemistry


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- Economic geology is studied and practiced by

geologists.

- However, it is of prime interest to investors, stock analystsand other professions such as engineers, environmental

scientists, and conservationists because of the far- reaching

impact that extractive industries have on society, the

economy, and the environment.


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An ore is defined as a mineral or an aggregate of minerals

from which a valuable constituent, especially a metal, can be

profitably mined or extracted.

Ore:

- It is an aggregate of economically important minerals that is

sufficiently rich to separate for a profit.

- Although more than 3,500 mineral species are known,

only about 100 are considered ore minerals.

- The term originally applied only to metallic minerals (see

native element) but now includes such nonmetallic substances

as sulfur, calcium fluoride (fluorite), and barium sulfate(barite) etc.

-
http://www.answers.com/topic/mineralhttp://www.answers.com/topic/native-elementhttp://www.answers.com/topic/sulfurhttp://www.answers.com/topic/fluoritehttp://www.answers.com/topic/baritehttp://www.answers.com/topic/baritehttp://www.answers.com/topic/fluoritehttp://www.answers.com/topic/sulfurhttp://www.answers.com/topic/native-elementhttp://www.answers.com/topic/native-elementhttp://www.answers.com/topic/native-elementhttp://www.answers.com/topic/mineral


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- Ore is always mixed with unwanted rocks and minerals,

known collectively as gangue.

- The ore and the gangue are mined together and then

separated. The desired element is then extracted from the

ore.

- The metal may be still further refined (purified) or alloyedwith other metals.

Gangue :

- It is a mineral occurring in sufficient quantity and

containing enough metal to permit its recovery and

extraction at a profit. The term is also applied to

rock containing such a mineral or metal, as goldore and copper ore.


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(Iron Ore)

(Cupper Ore)

(Lead Ore) (Gold Ore)
http://upload.wikimedia.org/wikipedia/commons/9/9d/GoldOreUSGOV.jpghttp://upload.wikimedia.org/wikipedia/commons/7/79/LeadOreUSGOV.jpghttp://upload.wikimedia.org/wikipedia/commons/3/31/Banded_iron_formation.pnghttp://upload.wikimedia.org/wikipedia/commons/a/a1/ManganeseOreUSGOV.jpg


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Important ore minerals

Acanthite: Ag2S for production ofsilver

Barite: BaSO4

Bauxite Al2O3 for production ofaluminium

Beryl: Be3Al2(SiO3)6for production of Berillium

Bornite: Cu5FeS4for production of Copper

Cassiterite: SnO2 for production of tin

Chalcocite: Cu2S for production ofcopper

Chalcopyrite: CuFeS2

for production of Copper

Chromite: (Fe, Mg)Cr2O4 for production ofchromium

Cinnabar: HgS for production ofmercury

Cobaltite: (Co,Fe)AsS for coblt

Columbite-Tantalite orColtan : (Fe, Mn)(Nb, Ta)2O6

Galena: PbS for lead
http://en.wikipedia.org/wiki/Acanthitehttp://en.wikipedia.org/wiki/Silverhttp://en.wikipedia.org/wiki/Baritehttp://en.wikipedia.org/wiki/Bauxitehttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Berylhttp://en.wikipedia.org/wiki/Bornitehttp://en.wikipedia.org/wiki/Cassiteritehttp://en.wikipedia.org/wiki/Chalcocitehttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Chalcopyritehttp://en.wikipedia.org/wiki/Chromitehttp://en.wikipedia.org/wiki/Chromiumhttp://en.wikipedia.org/wiki/Cinnabarhttp://en.wikipedia.org/wiki/Mercury_(element)http://en.wikipedia.org/wiki/Cobaltitehttp://en.wikipedia.org/wiki/Columbitehttp://en.wikipedia.org/wiki/Tantalitehttp://en.wikipedia.org/wiki/Coltanhttp://en.wikipedia.org/wiki/Galenahttp://en.wikipedia.org/wiki/Galenahttp://en.wikipedia.org/wiki/Coltanhttp://en.wikipedia.org/wiki/Tantalitehttp://en.wikipedia.org/wiki/Columbitehttp://en.wikipedia.org/wiki/Cobaltitehttp://en.wikipedia.org/wiki/Mercury_(element)http://en.wikipedia.org/wiki/Cinnabarhttp://en.wikipedia.org/wiki/Chromiumhttp://en.wikipedia.org/wiki/Chromitehttp://en.wikipedia.org/wiki/Chalcopyritehttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Chalcocitehttp://en.wikipedia.org/wiki/Cassiteritehttp://en.wikipedia.org/wiki/Bornitehttp://en.wikipedia.org/wiki/Berylhttp://en.wikipedia.org/wiki/Aluminiumhttp://en.wikipedia.org/wiki/Bauxitehttp://en.wikipedia.org/wiki/Baritehttp://en.wikipedia.org/wiki/Silverhttp://en.wikipedia.org/wiki/Acanthite


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Gold: Au, typically associated with quartz or as placerdeposits

Hematite: Fe2O3 : for Iron

Ilmenite: FeTiO3

: For Titanium

Magnetite: Fe3O4 : For iron

Molybdenite: MoS2 : For Mo

Pentlandite:(Fe, Ni)9S

8: For Nickel

Pyrolusite:MnO2 : For Manganese

Scheelite: CaWO4 : For tungsten

Sphalerite: ZnS : For ZincUraninite (pitchblende): UO2 for production of metallic uranium

Wolframite: (Fe, Mn)WO4 : For tungsten
http://en.wikipedia.org/wiki/Goldhttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Placer_mininghttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Ilmenitehttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Molybdenitehttp://en.wikipedia.org/wiki/Pentlanditehttp://en.wikipedia.org/wiki/Pyrolusitehttp://en.wikipedia.org/wiki/Scheelitehttp://en.wikipedia.org/wiki/Sphaleritehttp://en.wikipedia.org/wiki/Uraninitehttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Wolframitehttp://en.wikipedia.org/wiki/Wolframitehttp://en.wikipedia.org/wiki/Uraniumhttp://en.wikipedia.org/wiki/Uraninitehttp://en.wikipedia.org/wiki/Sphaleritehttp://en.wikipedia.org/wiki/Scheelitehttp://en.wikipedia.org/wiki/Pyrolusitehttp://en.wikipedia.org/wiki/Pentlanditehttp://en.wikipedia.org/wiki/Molybdenitehttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Ilmenitehttp://en.wikipedia.org/wiki/Hematitehttp://en.wikipedia.org/wiki/Placer_mininghttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Gold


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Processes of ore formation:

- The various theories of ore genesis explain how the various types of

mineral deposits form within the Earth's crust.

- Ore genesis theories are very dependent on the mineral or

commodity.

- Ore genesis theories generally involve three components:

(i)source (ii) transport or conduit (iii) trap

(i) Source is required because metal must come from

somewhere, and be liberated by some process

(ii)Transport is required first to move the metal bearing fluids or

solid minerals into the right position, and refers to the act ofphysically moving the metal, as well as chemical or physical

phenomenon which encourage movement

(iii) Trapping is required to concentrate the metal via some

physical, chemical or geological mechanism into aconcentration which forms minable ore
http://en.wikipedia.org/wiki/Crust_(geology)http://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Orehttp://en.wikipedia.org/wiki/Orehttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Crust_(geology)


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- The biggest deposits are formed when the source is large, the

transport mechanism is efficient, and the trap is active and ready at

the right time.

- Mineral deposits of economic importance may be formed in

a variety of ways.

- Their formation is very complex and most often takes

place in a combination of more than one processes.

- Mineral deposits form

- From magma by crystallisation or seggregation

or- Metamoprhism and alteration of preexisting

rocks and minerals

or

- By sedimentary processes.


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Processes Resulting deposits Varieties/examples

Magmatic concentration Magmatic deposits Diamond, chromite

Sublimation Sublimates

Contact metasomatism Contact-metasomatic deposits WollastoniteHydrothermal action (a) Filling of cavities

(b) Replacement of rock masses

Sedimentation (a) Sedimentary beds Iron, Manganese

(b) Evaporities Salt, gypsum(c) coal, petroleum

Weathering (a) Residual concentration Bauxite

(b) Placers Monazite, REE

(c ) Oxidised and supergenedeposits

Cupper, Lead, Zinc

Metamorphism Metamorphic deposits graphite

Hydrology Ground water supplies


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Classification of mineral deposits

Primary deposits Secondary deposits-Form from magma or mineral

rich solutions under influence

of temp & pressure.

Examples:Gold, chromite, magnetite,

Nickel, copper, lead, zinc etc.

-Formed from either sedimentary

processes or by weathering,

transportation and metamorphism

of pre-existing minerals.Examples:

Gypsum, limestone, bauxite,

Manganese,iron, kyanite etc.

(based on genetic significance)

Based on time of formation w.r.t. host rocks:Syngenetic mineral deposits

-form in the same period as

host rocks

eg. Chromite, coal, Iron etc.

Epigenetic mineral deposits

-Formed later than host rocks

-eg. vein/hydrothermal deposits

Cu,Pb, Zn, Au


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Magmatic deposits:

-are ore bodies which ahs intimate association with igneous rocks.

-In this there are different stages of ore formation:

(i) Early magmatic :(a) Disseminated crystallisation without concentration

eg. Diamond in Kimberlite pipes.

(b) Crystallisationsegregation : eg. Chromite , platinum deposits

(ii) Late magmatic :

(a) Residual, liquid accumulation and/or injection

eg. Titano-magnetite, chromium, platinum

(b) Liquid separation and accumulation: eg. Ni-Cu deposits(c) Pegmatites: eg. Beryl
http://upload.wikimedia.org/wikipedia/commons/0/06/Fractional_crystallization.svg


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Oreminerals

(eg

Chromite

Crystals).

(Dissemination of ores

eg. Diamond in kimberlite

pipes)

(segregation of ores

Eg. Chromite or magnetite)

[Schematic diagrams showing the principles behind fractional

crystallisation in a magma. While cooling, the magma evolves in

composition because different minerals crystallize from the melt.

1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3:

pyroxene and plagioclase crystallize; 4: plagioclase crystallizes.

At the bottom of the magma reservoir, a cumulate rock forms.]
http://upload.wikimedia.org/wikipedia/commons/0/06/Fractional_crystallization.svghttp://en.wikipedia.org/wiki/Magmahttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Pyroxenehttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Cumulate_rockhttp://en.wikipedia.org/wiki/Cumulate_rockhttp://en.wikipedia.org/wiki/Cumulate_rockhttp://en.wikipedia.org/wiki/Cumulate_rockhttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Pyroxenehttp://en.wikipedia.org/wiki/Olivinehttp://en.wikipedia.org/wiki/Magmahttp://upload.wikimedia.org/wikipedia/commons/0/06/Fractional_crystallization.svg


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- Fractional crystallization is one of the most important

geochemical and physical processes operating within the

Earth's crust and mantle.

- Fractional crystallization is the removal and segregation

from a melt ofmineral precipitates; except in special

cases, removal of the crystals changes the composition of

the magma.

- Fractional crystallization in silicate melts (magmas) is

complex compared to crystallization in chemical systems at

constant pressure and composition, because changes in

pressure and composition can have dramatic effects onmagma evolution.

-
http://en.wikipedia.org/wiki/Crust_(geology)http://en.wikipedia.org/wiki/Earth%27s_mantlehttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Magmahttp://en.wikipedia.org/wiki/Magmahttp://en.wikipedia.org/wiki/Mineralhttp://en.wikipedia.org/wiki/Earth%27s_mantlehttp://en.wikipedia.org/wiki/Crust_(geology)


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- Addition and loss of water, carbon dioxide, hydrogen, and

oxygen are among the compositional changes that must

be considered.

- For example, the partial pressure (fugacity) of water insilicate melts can be of prime importance, as in near-

solidus crystallization of magmas ofgranite composition.

- The crystallization sequence ofoxide minerals such asmagnetite and ulvospinel is sensitive to the

oxygen fugacity of melts, and separation of the oxide

phases can be an important control ofsilica concentration in

the evolving magma, and may be important in andesite

genesis.
http://en.wikipedia.org/wiki/Partial_pressurehttp://en.wikipedia.org/wiki/Fugacityhttp://en.wikipedia.org/wiki/Solidus_(chemistry)http://en.wikipedia.org/wiki/Granitehttp://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Ulvospinelhttp://en.wikipedia.org/wiki/Mineral_redox_bufferhttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Andesitehttp://en.wikipedia.org/wiki/Andesitehttp://en.wikipedia.org/wiki/Silicahttp://en.wikipedia.org/wiki/Mineral_redox_bufferhttp://en.wikipedia.org/wiki/Mineral_redox_bufferhttp://en.wikipedia.org/wiki/Ulvospinelhttp://en.wikipedia.org/wiki/Magnetitehttp://en.wikipedia.org/wiki/Oxidehttp://en.wikipedia.org/wiki/Granitehttp://en.wikipedia.org/wiki/Solidus_(chemistry)http://en.wikipedia.org/wiki/Fugacityhttp://en.wikipedia.org/wiki/Partial_pressure


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Discontinuous

Series

Continuous

SeriesHigh

OlivinePlagioclase

(Calcium rich)

Pyroxene

Amphibole

Biotite

(BlackMica)

Plagioclase

(Sodiumrich)

Relative

Crystallization

Temperature

Orthoclase

Muscovite

(WhiteMica)

Quartz

Low
http://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Pyroxenehttp://en.wikipedia.org/wiki/Amphibolehttp://en.wikipedia.org/wiki/Amphibolehttp://en.wikipedia.org/wiki/Biotitehttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Crystallizationhttp://en.wikipedia.org/wiki/Orthoclasehttp://en.wikipedia.org/wiki/Orthoclasehttp://en.wikipedia.org/wiki/Muscovitehttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Quartzhttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Muscovitehttp://en.wikipedia.org/wiki/Orthoclasehttp://en.wikipedia.org/wiki/Crystallizationhttp://en.wikipedia.org/wiki/Sodiumhttp://en.wikipedia.org/wiki/Plagioclasehttp://en.wikipedia.org/wiki/Micahttp://en.wikipedia.org/wiki/Biotitehttp://en.wikipedia.org/wiki/Amphibolehttp://en.wikipedia.org/wiki/Pyroxenehttp://en.wikipedia.org/wiki/Calciumhttp://en.wikipedia.org/wiki/Plagioclase

Documents

Ores and Gangues