CMA Geology & Mineral Exploration 3 — Questions and Answers
Question 1: What is the geological significance of a 'graben' structure in mineral exploration?
- A down-dropped block bounded by normal faults, often hosting sediment-hosted mineral deposits (Correct answer)
- An uplifted block flanked by reverse faults
- A volcanic crater filled with mineralized breccia
- A fold structure containing anticlinal oil traps
Correct answer: A down-dropped block bounded by normal faults, often hosting sediment-hosted mineral deposits
Grabens are rift-related structures where sediment accumulates and can host stratabound mineral deposits including lead-zinc and copper.
Question 2: Which mineral is the primary ore of aluminum and forms by intense tropical weathering of aluminous rocks?
- Bauxite (Correct answer)
- Gibbsite
- Kaolinite
- Feldspar
Correct answer: Bauxite
Bauxite is a lateritic ore composed mainly of aluminum hydroxide minerals formed by deep chemical weathering in tropical climates.
Question 3: In the classification of coal, which rank has the highest carbon content and heating value?
- Anthracite (Correct answer)
- Bituminous coal
- Sub-bituminous coal
- Lignite
Correct answer: Anthracite
Anthracite has the highest carbon content (>86%) and heating value among coal ranks, formed by maximum coalification under heat and pressure.
Question 4: A volcanogenic massive sulfide (VMS) deposit is best described as:
- A seafloor hydrothermal deposit of sulfide minerals formed at or near volcanic centers (Correct answer)
- A magmatic segregation deposit in layered mafic intrusions
- A residual deposit formed by tropical weathering of sulfide rock
- A skarn deposit at the contact of limestone and granite
Correct answer: A seafloor hydrothermal deposit of sulfide minerals formed at or near volcanic centers
VMS deposits form when seafloor hydrothermal vents precipitate massive sulfide lenses of copper, zinc, and lead near submarine volcanic centers.
Question 5: Which exploration tool uses variations in Earth's magnetic field to locate iron-bearing mineral deposits from aircraft?
- Airborne magnetic survey (Correct answer)
- Airborne gravity survey
- Airborne electromagnetic survey
- Airborne radiometric survey
Correct answer: Airborne magnetic survey
Airborne magnetic surveys measure total magnetic field intensity, effectively identifying magnetite-bearing rocks and iron ore deposits over large areas rapidly.
Question 6: What does a 'soil geochemical anomaly' represent in mineral exploration?
- An area where metal concentrations in soil exceed background levels, potentially indicating a buried deposit (Correct answer)
- A zone where soil pH prevents plant growth
- An area of unusually deep weathering profile
- A region where soil moisture is abnormally low
Correct answer: An area where metal concentrations in soil exceed background levels, potentially indicating a buried deposit
Soil geochemical anomalies identify areas where metals have migrated upward from buried mineralization and provide exploration drill targets.
Question 7: The Carlin-type gold deposit, named after deposits in Nevada, is characterized by:
- Microscopic gold disseminated in sedimentary carbonate rocks altered by hydrothermal fluids (Correct answer)
- Coarse visible gold in quartz veins cutting granite
- Gold-bearing massive sulfides on the seafloor
- Placer gold concentrated by river systems
Correct answer: Microscopic gold disseminated in sedimentary carbonate rocks altered by hydrothermal fluids
Carlin-type deposits contain submicron gold trapped in arsenian pyrite within decarbonated and silicified limestone, making them unique and very large.
CMA Geology & Mineral Exploration 3
What is the geological significance of a 'graben' structure in mineral exploration?