ASBOG - Association of State Boards of Geology Economic Geology and Energy Questions and Answers 2

Question 1

Which type of ore deposit forms when hydrothermal fluids precipitate minerals along faults and fractures in host rock?

Accepted Answer

Vein deposit

Answer

Vein deposits form when hydrothermal fluids migrate through fractures and precipitate ore minerals as the fluids cool or chemically react with host rock.

Question 2

What is the primary driving force behind the formation of sedimentary exhalative (SEDEX) deposits?

Accepted Answer

Magmatic intrusion heating basin brines

Answer

SEDEX deposits form when magmatic or geothermal heat drives basin brines upward through faults to exhalate on the seafloor, depositing metal sulfides.

Question 3

Which energy resource is primarily associated with organic-rich black shales deposited in anoxic marine basins?

Accepted Answer

Shale gas and oil

Answer

Organic-rich black shales deposited under anoxic conditions preserve large quantities of organic matter that thermally mature into shale gas and oil over geologic time.

Question 4

A geologist identifies a porphyry copper deposit. What is the most common tectonic setting for this deposit type?

Accepted Answer

Convergent plate margin above a subduction zone

Answer

Porphyry copper deposits form above subduction zones where magmas derived from the mantle wedge carry copper-rich fluids that concentrate in shallow intrusions.

Question 5

In petroleum geology, what is the term for impermeable rock that prevents upward migration of hydrocarbons, trapping them in a reservoir?

Accepted Answer

Seal rock (cap rock)

Answer

Seal rock, also called cap rock, is an impermeable layer (commonly shale, evaporite, or tight carbonate) that overlies a reservoir and prevents hydrocarbons from escaping upward.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Economic Geology and Energy Questions and Answers 2