Resources Flashcards
What is sulfur used for?
Medicine
Sulfuric acid
Match heads
What is magnesium used for?
Metal alloys
Medicine
What is phosphorous used for?
Super phosphate for agriculture
What is aluminium used for?
Agriculture
Food
Building
Electrical
What is barium used for?
Medicine
What is fluorine used for?
Toothpaste
Smelting ores
What is sodium chloride used for?
Food additive
What is barium/caesium used for?
Treatment of cancers
What is copper/lead/zinc used for?
Pipes
Electrical components
Paints
What are diamonds used for?
Drilling
Lasers
Polishing
Jewellery
What is gold used for?
Electrical components
Research
Medicine
Jewellery
Resource =
Material available to us from the Earth for our daily lives
Economic resource =
Known and recoverable today
Sub economic resource =
Known but can’t recover at a profit
Reserve (ore) =
Concentration of material or element deemed to have value
- discoverable, mined economically and legally
- fraction of resource known to exist
How does a resource become a reserve?
Relies on:
Recovery at a profit
Physical factors e.g. water, energy, infrastructure
Human factors e.g. politics, taxation, environmental
Grasberg, papa New Guinea
World largest gold reserve
2nd largest copper reserve
Enrichment factor =
Level of element concentration above crustal abundance that makes it an ore
Hydrothermalism =
Viable analogue in ore forming processes for metamorphism
Involves modification of igneous and sedimentary rocks by heat transfer and pressure fluctuation
Syngenetic =
Ore deposits that form at the same time as the host rock
Source
Large scale, long term geochemical reservoirs
Agent =
Means by which metal ores are removed from source and transported to the site of deposition
CHEMICALLY - interact in solution
PHYSICALLY - transport e.g. grains
Deposition, requires…
1) suitable site and conditions
2) change in transportation to cause ore forming mineral formation
- physical
- chemical (P/T/pH/Eh)
Energy =
Required to mobilise agent
Also assists dissolution prior to transport and deposition
Heat derived from radioactive decay and then transferred by conduction/convection
Direct crystallisation - Example
Uraninite mine in Namibia
2007: 6th largest producer of nuclear energy
125 times U found in normal rocks e.g. black shale enriched in U because organic matter sequestered it
Carbonatite =
Igneous rock with high levels of calcite, dolomite and siderite
Low levels of silica
Unusual to be carbonate rich
- low temperature volcanism 550-600
How do carbonate melts form?
Liquid immiscibility
- silicate minerals crystallise
- increase relative carbonate abundance
- physically separates
Importance of carbonatites
They crystallise with a high % of rare metals
- phosphorous (apatite)
- iron, titanium (magnetite)
- niobium (pyroclore)
- zirconium (baddeleyite)
+ REE
- tantalum
- uranium
- thorium
Rare Earth Element deposits - examples
Palabora South Africa - Fe - Cu - P - Zr - U 225 megatonnes of copper at 0.7% = worth $9.4 billion
Mountain pass California
- 8% bastinite with REE in
The greatest REE deposit in the world
Demand for REE
Hybrid car batteries ~20kg
Wind turbines
- 2 tonnes of high strength magnets ~30%
Pegmatites =
Very coarse grained rocks
Big source of REE
Crystals several cm in length
- granitic
- quartz, feldspar, mica
- topaz/tourmaline
Pegmatite Example
South Dakota Precambrian black hills pegmatite with spodumene (LITHIUM aluminium silicate) crystals 15m
Beryllium
Be
Beryl
Low density, high melting T, resistant
Brake disks in jet aircraft, x ray tubes
Caesium
Cs
Pollucite
Atomic clocks, light sensitive detectors
Nuclei have different energy states
Cerium
Ce
Monazite
Phosphorescence, high friction
High definition TV tubes, lighter flints
Lithium
Li
Spodumene
Low density, high thermal conductivity, low MT
Low density alloys, batteries, coolant in nuclear reactions
Tantalum
Ta
Tantalite
High density, machineable, high resistivity, corrosion resistant
Military warheads, electronic capacities, surgical implants
Tin
Sn
Cassiterite
Low MT, corrosion resistant
Tinplate, float glass, alloys
Tungsten
W
Wolframite
High density, high MT, low thermal expansion
Abrasive and cutting tools, light bulb filaments, high speed steel
Uranium
U
Fissile isotopes
Nuclear reactor fuel
Pegmatite formation
In situ fractional crystallisation of a pegmatite magma
As it progressively crystallises, the wt% of water and incompatible elements increases within the residual melt
- crystallises slower
- increase grain size
Magmatic segregation =
Mineral separation in a magma due to fractional crystallisation to form cumulate layers
2nd pulse of magma allows e.g. chromite to form over a longer period of time
Magmatic segregation; chromite - why is it necessary?
Max Cr content in ultra mafic lavas = 0.2 wt%
Need >= 30% to mine
So cumulate layers are useful!!!
E.g. Dwars river on the Bushveld Complex
Bushveld and the Great Dyke
World’s most valuable mineral deposit
Cr Pt Pd Ru Au It Rh Cu Ni V
Liqueation of sulphur melt
Liquid immiscibility process
What kind of deposits does liqueation of a sulphur melt form?
Nickel, copper and iron basaltic ore deposits
= MASSIVE DISSEMINATED SULPHIDE ORES
Liqueation of sulphur melt, Example
Voisey’s Bay, Canada
One of the worlds largest nickel deposits
Olivine gabbro when sulphide coats the minerals
Kimberlite formation
A mixture of melt from the mantle and fragmented mantle material is picked up on kimberlites way to the surface
Made up of
- xenoliths (rock)
- xenocrysts (crystals like diamond)
Rapid emplacement up pipeline bodies and deposited in areas of very old, stable lithosphere (intraplate)
Hydrothermalism =
Any chemical or physical process by which hot, aqueous fluids are a component of ore formation
Aqueous fluids involved in hydrothermalism
Meteoric
- from precipitation
Magmatic
- released in eruption
Connate
- trapped during sedimentation
Metamorphic
- dehydration
Mantle
Pathways =
Permeable
Porous
Fractures
Cavities
Present day hydrothermalism =
Metal rich hydrothermal fluids actively venting on the earth’s surface
Also black smokers
Characteristics of present day hydrothermalism
Fluids above magmatic heat sources 200-350
Can be saline
Siliceous sinter and travertine deposits
Diverse element enrichment
Present day hydrothermalism examples
Champagne pool NZ
Dalton sea
California
Red Sea brine pools
Black smokers
Stratiform layers of metaliferous sediments
- hot basaltic magma percolates H2O
- leaches metals
- comes to surface
- reacts with cold seawater
- forms sediment
Ocean mining
Papa new guinae
Types of ancient hydrothermalism
Porphyry type
- Cu
- Mo
- Au
Massive sulphide (SEDEX) - Cu - Pb - Zn (Ba)
Mississippi valley type
- Pb (galena)
- Zn (sphalerite)
- BITUMEN
Porphyry type formation
250-600
Repeats over 50-250 million years
WET MAGMA COOLS
- increased water content
- bubbles separate out and rises
- scavenges soluble metals from magma
MAGMA RISES
- low pressure
- water boils = steam = increases volume
HYDROFRACTURE
STOCKWORK VEIN SYSTEM
RAPID FLUID ESCAPE
- rapid crystallisation
- porphyritic texture and deposition of ore minerals in fractures
Porphyry ore characteristics
Low grade high tonnage
- typically 0.3-1% Cu and 50-1000Mt of ore
Small diameter intrusions in host rocks
Wall rock alteration via ore bearing fluids reacting
STOCKWORK with the ore disseminated
Pyrite, chalcopyrite, bornite
Porphyry type
Example
Bingham canyon, Utah
SEDEX
Submarine hydrothermalism =
Sedimentary Exhalative Massive Sulphide Deposits
Characteristics of SEDEX
Mostly mudstones intercollated with very fine sulphide deposits
Cu Pb Zn
Sometimes barite if SULPHATE
SEDEX Example
Red dog, Alaska
World’s largest zinc deposit
Mississippi valley type
Basically fluids expelled during sediment compaction
Migrate into limestone
Metals precipitated into cavities and fractures when fluids react with limestone
100-150 degrees
Types of sedimentary processes and ore formation
Direct precipitation from water - BIFs
Kupferschiefer
Placer deposits
Weathering/residual deposits - laterites and secondary enrichment
BIFs =
Primary Fe3 ion sources
- hematite
- magnetite
- siderite
Fe(II) vs Fe (III)
Fe2, ferrous iron
Soluble in reducing conditions
Fe3, ferric iron
Insoluble and therefore precipitates in oxidising conditions
How do BIFs form?
Fe2 rich water reacts with neutral water = oxidation
= Fe3 = precipitation
Iron rich chert with cryptocrystalline silica
When did BIFs form?
In Proterozoic/archaean times
And 720-660Ma
Why did BIFs form when they did in Proterozoic/archaean times?
Low levels of oxygen in the atmosphere
Iron in the ocean due to hydrothermal input and continental weathering
Photosynthesis suddenly increased oxygen and Fe was oxidised
- quickly used oxygen
- fe built up
- O2 built up etc etc
Once oxygen was readily available it didn’t build up so more so didn’t form as “the ferrous ions were exhausted”
Why did BIFs form 720-660Ma?
Neoproterozoic times
“Snow ball Earth”
- lacked water
- lacked atmospheric interaction
Ice sheet broke up = flood of oxygen into the ocean
Short lived and not economic
Kupferschiefer =
Stratiform sediment of copper shale
Enriched in Cu and Zn
Economic in a few areas e.g. Poland (the leading copper producer in Europe)
Kupferschiefer deposition
Syn deposition sulphide precipitation
Sulphide precipitation due to bacterial reduction of sulphate in seawater
Pyrite
Kupferschiefer replacement
SYN DIAGENESIS
Connate water leaches copper and other metals
Replaces primary sulphides with copper bearing sulphides
Placer deposit =
Concentrate of heavy minerals
How do placer deposits form?
Exposed ore body
Weathered = eroded
Stream environment = deposited where there is a drop in energy e.g. inside a meander
Characteristics of placer deposits
Dense
Hard
Poor cleavage
= not transported far and withstands erosion
Placer deposit examples
WITWATERSRAND FOSSIL GOLD PLACER DEPOSIT, SOUTH AFRICA
- 2 billion years old
- 48,000 metric tonnes of gold mines
- 40% of the world’s total production
CANADA
- ice sheets migrated diamonds and other minerals from kimberlite
ORANGE RIVER, AFRICA
- old river system which has migrated
- 97% gem quality
- 60-100 carats
Laterites =
In situ residual deposit
How do laterites form?
Water percolates into soil/bedrock etc
Mobilises and transports metals
Form enriched zone with kaolinite and insoluble hydrated oxides
Why are laterites economic at low grades?
Poorly consolidated at surface = easy to mine
High levels of Al = third most abundant element but usually locked in silicate minerals
Cheap labour due to locations
Secondary enrichment =
Analogous to laterite formation
How do secondary enrichment deposits form?
Oxidising water reacts with metals and soil
- oxygen used
- more reducing conditions with depth
Different reactions take place
Secondary enrichment - layers
GOSSAN LAYER
- iron cap
- pyrite»_space;> iron oxides
LEACHED ZONE
- dissolved O2/CO2 in groundwater leaches out minerals = sulfuric acid
OXIDISED ZONE
- primary»_space;> secondary minerals = oxides + carbonates
- malachite/azurite/native Cu
WATER TABLE
ENRICHED ZONE - R E D U C I N G
- primary sulphides don’t break down
- “supergene sulphide enrichment” zone
- new sulphide minerals
- chalcocite/bornite
PRIMARY ZONE
- unaltered primary minerals
Magmatic
Direct crystallisation
Carbonatite
Pegmatites
Cumulate layers
Liquidation of sulphur melt
Kimberlite
Hydrothermal
Present day
Porphyry type
Submarine - SEDEX
Mississippi-Valley type
Sedimentary
Direct precipitation
Kupferschiefers
Placer deposits
Laterites
Secondary enrichment
Liqueation MINERALS
Nickel
Copper
Iron
- sulphides
Pyrrhotite and Chalcopyrite
Magmatic segregation MINERALS
Iron
Chromium
Chromite
Pegmatites MINERALS
Quartz Feldspar Mica Topaz Tourmaline Be, Ce, Cs REE; Li, Nb, Rb, Ta, Th, Sn, W, V, Zr
Carbonatite MINERALS
Calcite
Dolomite
Siderite
REE
Potassium (low silica)
Fe, T»_space; magnetite
Zirconium
Laterite MINERALS
Kaolinite
Hydrated oxides
Placer MINERALS
Ilmenite
Cassiterite
Columbite
Zircon
Gold
Diamond
Kupferschiefer MINERALS
Cu
Zn
Chalcopyrite/Bornite
Pb
Galena
Zn
Sphalerite
Pt
