L4 - Platinum group elements (PGE)

Question 1

Where are PGEs highly enriched?

Answer 1

In the core, mantle, and extraterrestrial bodies.

Question 2

What are the melting and condensation properties of PGEs?

Answer 2

• High melting and condensation temperatures.
• Early condensation from the solar nebula and mantle processes.

Question 3

What are the concentrations of PGEs in meteorites and the crust?

Answer 3

• Meteorites: 400-900 ppb.
• Crust: 0.4-0.5 ppb

Question 4

Why are PGEs siderophile elements?

Answer 4

They bond with iron and sulfides.

Question 5

How are PGEs transported?

Answer 5

As sulfur (S) and chlorine (Cl) complexes.

Question 6

What was the first application of PGEs in catalytic reactions?

Answer 6

Davy’s safe lamp (1817) used a platinum wire to limit combustion of flammable gases

Question 7

What properties make PGEs suitable for industrial applications?

Answer 7

• Resistance to corrosion and oxidation.
• Stability at high temperatures

Question 8

What are the catalytic applications of PGEs?

Answer 8

• Automotive: Oxidation of exhaust gases.
• Petrochemical: Improving fuel octane rating.
• Chemical: Fertilizer, explosives, nitric acid, and hydrogen cyanide production.

Question 9

What are other applications of PGEs?

Answer 9

• Jewelry.
• Electrical contacts and wires.
• Electronics (hard drives, LCD displays).
• Medical and dental uses

Question 10

What sulfide minerals are PGEs associated with?

Answer 10

• Pyrrhotite (Fe₁₋ₓS).
• Pentlandite.
• Chalcopyrite

Question 11

Name accessory PGE minerals

Answer 11

• Sperrylite.
• Laurite.
• Erlichmanite.
• Irarsite.
• Braggite.
• Cooperite

Question 12

What is the typical economic ore grade for PGEs?

Answer 12

2.5-10 g/t (ppm), which represents an enrichment of <25,000x

Question 13

Name significant locations for PGE reserves.

Answer 13

• Stillwater Complex.
• Sudbury Basin.
• Great Dyke.
• Stella Intrusion.
• Bushveld Complex.
• Norilsk.

Question 14

What are the main deposit types for PGEs?

Answer 14

Layered igneous intrusions (orthomagmatic).

Placer deposits.

Question 15

What is the Bushveld Complex?

Answer 15

The largest layered igneous intrusion, located in NE South Africa, a primary source of PGEs.

Question 16

What rocks dominate the Bushveld Complex?

Answer 16

Mafic and ultramafic rocks.

Some granitic and sedimentary country rocks

Question 17

Describe the stratigraphy of the Bushveld Complex

Answer 17

• 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.

Question 18

What are the main PGE reefs in the Bushveld Complex?

Answer 18

Merensky Reef (3-20 g/t PGE, first discovered in 1926).

UG-2 Reef (4-7 g/t PGE, primary source today).

Question 19

How do PGEs form in layered intrusions?

Answer 19

Partial melting of the mantle incorporates sulfides, which scavenge PGEs.

Sulfides bond with PGEs, becoming dense and forming cumulates as they crystallize.

Question 20

What is the role of fractional crystallization in PGE formation?

Answer 20

• Dense minerals (olivine, pyroxene) crystallize first.
• Sulfides saturate the melt, forming droplets that collect PGEs.

Question 21

How does magma mixing impact PGE formation?

Answer 21

• Injection of melt into magma chambers disrupts crystallization.
• Mixing promotes PGE scavenging by sulfide droplets

Question 22

What are the key exploration methods for PGEs?

Answer 22

• Gravimetry: Detects density variations.
  Seismic techniques:
• Identifies features >25m, such as potholes

Question 23

How are PGEs produced?

Answer 23

• Underground mining (500-2000m depth).
• Flotation processes separate hydrophilic feldspar and hydrophobic PGEs using foam

Question 24

What are the environmental impacts of PGEs?

Answer 24

Emissions from cars, smelters, and medical facilities.
Potential bioavailability of PGE nanoparticles.

Question 25

Why are PGEs considered critical resources?

Answer 25

• Rare in the crust, requiring high enrichment for economic extraction.
• Essential for catalytic, electronic, medical, and jewelry applications.