ASBOG Economic Geology and Energy 2

Question 1

Which ore deposit type forms when magmatic fluids cool and precipitate minerals into surrounding fractures, often at temperatures between 200–400°C?

Accepted Answer

Hydrothermal vein deposit

Answer

Hydrothermal vein deposits form as mineral-rich fluids cool and precipitate ore minerals into fractures and faults.

Question 2

The 'cut-off grade' in mining economics refers to:

Accepted Answer

The minimum ore grade that covers all costs of mining and processing

Answer

Cut-off grade is the minimum grade at which ore can be mined and processed while still covering all associated costs.

Question 3

Unconventional natural gas trapped in fine-grained sedimentary rock and requiring hydraulic fracturing to produce is called:

Accepted Answer

Shale gas

Answer

Shale gas is natural gas stored within shale formations and typically requires hydraulic fracturing ('fracking') for economic production.

Question 4

A porphyry copper deposit is characteristically associated with:

Accepted Answer

Felsic to intermediate intrusions at convergent plate margins

Answer

Porphyry copper deposits form from magmatic-hydrothermal fluids associated with felsic to intermediate intrusions at convergent plate margins.

Question 5

Which coal rank has the highest carbon content and is considered the best metallurgical coal?

Accepted Answer

Anthracite

Answer

Anthracite has the highest carbon content (>86%) and lowest volatile matter among coal ranks, making it the highest-rank coal.

ASBOG - Association of State Boards of Geology Practice Test