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

Question 1

An exploration geologist discovers a large, stratabound ore body hosted within a Paleozoic dolomite reef complex.
The primary ore minerals are sphalerite and galena, with minor fluorite and barite.
Fluid inclusion studies indicate formation temperatures of 100-150°C from highly saline fluids.
This ore deposit is best classified as which of the following types?

Accepted Answer

Mississippi Valley Type (MVT)

Answer

Volcanogenic Massive Sulfide (VMS)

Answer

Porphyry Copper

Answer

Sedimentary Exhalative (SEDEX)

Question 2

Which of the following lists the five essential elements required for the formation and preservation of a conventional hydrocarbon accumulation?

Accepted Answer

Source rock, Reservoir rock, Seal, Trap, and Migration

Answer

Kerogen, Porosity, Permeability, Anticline, and Overburden

Answer

Shale, Sandstone, Salt dome, Oil window, and Basement rock

Answer

Organic matter, Heat, Pressure, Time, and a Basin

Question 3

A geologist is logging core from a porphyry copper system and observes a central zone rich in secondary biotite and K-feldspar. This is immediately surrounded by an extensive zone of quartz-sericite-pyrite alteration. What are the correct names for these two alteration zones, from the core outwards?

Accepted Answer

Potassic, Phyllic

Answer

Propylitic, Argillic

Answer

Phyllic, Potassic

Answer

Skarn, Greisen

Question 4

A seismic survey reveals a potential hydrocarbon accumulation where a porous sandstone reservoir pinches out updip, becoming encased in impermeable marine shale. There is no evidence of faulting or folding in the immediate area. What type of trapping mechanism does this describe?

Accepted Answer

Stratigraphic trap

Answer

Salt dome trap

Answer

Anticlinal trap

Answer

Fault trap

Question 5

Which of the following correctly lists the ranks of coal in order of increasing heat content, carbon content, and metamorphic grade?

Accepted Answer

Lignite, Sub-bituminous, Bituminous, Anthracite

Answer

Bituminous, Anthracite, Lignite, Sub-bituminous

Answer

Lignite, Anthracite, Sub-bituminous, Bituminous

Answer

Anthracite, Bituminous, Sub-bituminous, Lignite

Question 6

Roll-front uranium deposits are a significant type of sandstone-hosted uranium deposit. What is the fundamental geochemical process responsible for their formation and crescent shape?

Accepted Answer

Precipitation at the interface between oxidizing and reducing groundwater.

Answer

Gravitational settling of dense uraninite crystals in a stream channel.

Answer

Intrusion of a uranium-rich pegmatite into the sandstone host rock.

Answer

Hydrothermal precipitation from high-temperature magmatic fluids.