L4 - Platinum group elements (PGE) Flashcards
Where are PGEs highly enriched?
In the core, mantle, and extraterrestrial bodies.
What are the melting and condensation properties of PGEs?
- High melting and condensation temperatures.
- Early condensation from the solar nebula and mantle processes.
What are the concentrations of PGEs in meteorites and the crust?
- Meteorites: 400-900 ppb.
- Crust: 0.4-0.5 ppb
Why are PGEs siderophile elements?
They bond with iron and sulfides.
How are PGEs transported?
As sulfur (S) and chlorine (Cl) complexes.
What was the first application of PGEs in catalytic reactions?
Davy’s safe lamp (1817) used a platinum wire to limit combustion of flammable gases
What properties make PGEs suitable for industrial applications?
- Resistance to corrosion and oxidation.
- Stability at high temperatures
What are the catalytic applications of PGEs?
- Automotive: Oxidation of exhaust gases.
- Petrochemical: Improving fuel octane rating.
- Chemical: Fertilizer, explosives, nitric acid, and hydrogen cyanide production.
What are other applications of PGEs?
- Jewelry.
- Electrical contacts and wires.
- Electronics (hard drives, LCD displays).
- Medical and dental uses
What sulfide minerals are PGEs associated with?
- Pyrrhotite (Fe₁₋ₓS).
- Pentlandite.
- Chalcopyrite
Name accessory PGE minerals
- Sperrylite.
- Laurite.
- Erlichmanite.
- Irarsite.
- Braggite.
- Cooperite
What is the typical economic ore grade for PGEs?
2.5-10 g/t (ppm), which represents an enrichment of <25,000x
Name significant locations for PGE reserves.
- Stillwater Complex.
- Sudbury Basin.
- Great Dyke.
- Stella Intrusion.
- Bushveld Complex.
- Norilsk.
What are the main deposit types for PGEs?
Layered igneous intrusions (orthomagmatic).
Placer deposits.
What is the Bushveld Complex?
The largest layered igneous intrusion, located in NE South Africa, a primary source of PGEs.
What rocks dominate the Bushveld Complex?
Mafic and ultramafic rocks.
Some granitic and sedimentary country rocks
Describe the stratigraphy of the Bushveld Complex
- Distinct layers of ultramafic (lower) and mafic (upper) rocks.
- Feldspar absent in ultramafic rocks but present in mafic rocks.
- Chromite bands contain high PGE concentrations.
What are the main PGE reefs in the Bushveld Complex?
Merensky Reef (3-20 g/t PGE, first discovered in 1926).
UG-2 Reef (4-7 g/t PGE, primary source today).
How do PGEs form in layered intrusions?
Partial melting of the mantle incorporates sulfides, which scavenge PGEs.
Sulfides bond with PGEs, becoming dense and forming cumulates as they crystallize.
What is the role of fractional crystallization in PGE formation?
- Dense minerals (olivine, pyroxene) crystallize first.
- Sulfides saturate the melt, forming droplets that collect PGEs.
How does magma mixing impact PGE formation?
- Injection of melt into magma chambers disrupts crystallization.
- Mixing promotes PGE scavenging by sulfide droplets
What are the key exploration methods for PGEs?
- Gravimetry: Detects density variations.
Seismic techniques: - Identifies features >25m, such as potholes
How are PGEs produced?
- Underground mining (500-2000m depth).
- Flotation processes separate hydrophilic feldspar and hydrophobic PGEs using foam
What are the environmental impacts of PGEs?
Emissions from cars, smelters, and medical facilities.
Potential bioavailability of PGE nanoparticles.
