MINERAL REASOURCES Flashcards
- Provide examples of things that are mined from the earth
o Rock slabs (eg. Granite/ metamorphic countertops, slate garden pavers)
o Gemstones
Minerals humans have socially “agreed” are valuable and often cut (facet) to enhance mineral luster and color
o Fuels
Fossil (peat, coal)
Mineral (uranium)
o Precious metals
o Base metals
o Industrial minerals and materials
Industrial minerals: not sources of fuel or metals, used for their physical and chemical properties (eg. Potash, gypsum, talc)
Aggregate: sand, gravel, crushed stone for construction
o Mineral deposit
an unusual mineral concentration, regardless of whether or not it can be extracted
o Mineral resource:
a concentration of natural material that can be extracted now or in the future, includes reserves. Depending on how much data we have we can consider resources to be measures, indicated or inferred
o Mineral reserve
: resources that can be determined to be extracted at a profit at the time of determination
o Ore
: a naturally occurring solid material form which a valuable mineral can be extracted for a profit
o Grade:
: the concentration of the desired material (mineral or element) the ore contains
o Ore minerals are those that contain the elements of interest
Oxides, sulphides, silicates, elemental metals
Easily extractable
o Gangue minerals
those that are part of the deposit but are considered waste material
- Sedimentary (
eg solutions/precipitation and placer deposits)
o Placer deposits weathering and erosion concentrate ore minerals, usually through fluvial transport
- Magmatic
. Crystal settling and fractionation)
o Igneous sulfide minerals are immiscible in magmas and sink to the bottom of he magma chamber
- Metamorphic
eg. Contact metamorphism and hydrothermal alteration)
o Hydrothermal metals are concentrated in hydrothermal veins
o Plate tectonic is the unifying theory of geology- it provides a geodynamic framework for geological phenomena
Rock deformation
Metamorphism
Magmatism
Climate (oceans circulation, continental elevation)
o Deposits in time and space
Mineral deposits types are not randomly distributed in tie or space- they have preferred or exclusive geological ages or tectonic settings
There is an association of mineral deposits with ….
- Particular geodynamic environments reflecting tectonic setting:
o Convergent margins subduction, collision
o Divergent margins mid-ocean rides, back arc basin
o Most of the world’s major deposits of iron
Chemical sedimentary rocks- precipitation in the oceans
Proterozoic age (dominantly 1.8-25 Ga)
Fe in hematite (Fe2O3) and magnetite (Fe3O4)
o Global distribution of large and giant iron formations and select smaller deposits
Early Paleoproterozoic/ Neoarchean in America. Brazil, Australia and South Africa
* Little or no free oxygen
o Formed as chemical sediments in shallow seas in the Precambrian when the atmosphere and oceans were poor in oxygen
BIF resulted form changes in the iron chemistry of sea water
Because there was little oxygen at this time, iron was present in its reduced state (Fe2+) which can readily be dissolved and transported by water soluble in water and periciptated out as layer of Fe- oxides like hematite and magnetite
o The source of iron in IBF was hydrothermal Fe2+ emitted along ocean ridges or submarine mantle plume- related volcanism:
Fe2+ was dissolved and transported in these deep water, building up over time
Oxidation of seawater by the anoygenic photosynthesis of “iron bacterica” changes iron to its oxidized state (Fe3+)
Fe3+ is not
o Porphyry copper deposits
Large tonnage, low grade deposits
Worlds primary source of coper, Mo, Sn-W (+Au)
Form at depth in magmatic arcs (2-4kms)
The mot important source of Cu and Mo in BC (eg highland valley copper)
Porphyritic- igneous texture, larger crystals in a finer grained groundmass
Mineralization in veins more veins = more ore
o High vs low grade – refers to the concentration of the ore
In general, mineral deposits which occur in veins are higher grade and mineral deposits which contain disseminated ore are low grade
o Large low grade deposits
Open pit copper mine in Canada – grade 0.4% Cu
o Diamonds
Canada is one of the largest producers of diamonds
Diamonds are used as gems and have industrial purposes
Diamonds form within cratons (thick, ancient portions of continental crusts) at ~150-200km depth
Brough to the surface by Kimberlite magmas
o Ores need to be located (exploration), obtained (extraction, and then concentrated (beneficiation/smelting/refining)
After mining is completed, surface and underground impacts should be remediated and the land reclaimed. Mines need to be safely closed
o Exploration
Important to determine location, size, depth, and the orientation/trend of the deposit
Methods to find suitable mining locations
- Create and review geological maps (surface and cross sectional)
- Compare area of exploration to similar environments where the mineral has been found in appropriate concentrations previously
- Visit the potential mine site to complete field studies, which might entail additional mapping, surface rock sampling, and chemical analysis
mining depends on ..
Depends on the size, shape, type, depth, and grade of the deposit
open pit
o Cheaper
o Ore body is close to the surface
o Method has a lot of waste rock (gangue)
underground mining
o Used for deeper deposits
o More costly
o More precise
o Formation of coal
Dead plant matter collects in oxygen poor water (swamp)
Sediments cover organic matter, adding heat ad pressure
Peat lignite, brown coal sub-bituminous coal semi anthracite anthracite
Starts with moisture, volatile matter and oxygen more calorific value, fixed carbon and carbon as more heat and pressure
o Formation of oil
Accumulation of marine microorganism
Methane produced at low depths through anerobic bacteria
At deep depths there is the oil window which is the T and P conditions which favor the formation of oil
- Provide a very basic explanation of environmental impacts that might result from mining
o Landscape and habitat degradation
o Need to control of surface water runoff (mt Polley BC)
funding to ensure safe mine closure and restoration
o Land reclamation
Natural ecosystem disturbance (mining) (restoration, rehabilitation, replacement)
o Many metals occur in nature as sulfides:
Fe as pyrite (FeS2)
Cu as Cu2S (chalcocite, Cu5FeS4 (bornite)
Zn as ZnS (sphalerite)
o Trace toxic metals – calcium, arsenic
o Processing of ore releases sulfur
Acid rain downwind of smelters
Acid mine drainage
* Mine tailing (waste) expose sulphides to air and water
o FeS2 +h2+ O2 Fe (in water) + H2SO4 (sulfuric acid) acid mine drainage
* Rio Tinto (red river) in SW Spain
* 5000 years of mining in this region (Cu, Ag, Au)
* pH= 2 to 2.5, red color due to iron dissolved in water
o Cyanide used to extract gold in small mines
