CMA Geology & Mineral Exploration 2 — Questions and Answers
Question 1: Which geophysical method measures variations in Earth's gravitational field to detect subsurface density contrasts?
- Gravity survey (Correct answer)
- Magnetic survey
- Seismic reflection
- Induced polarization
Correct answer: Gravity survey
Gravity surveys detect density variations in subsurface rock formations, useful for locating ore bodies and salt domes.
Question 2: In mineral exploration, what does the term 'strike' refer to?
- The direction of a vein or ore body along the horizontal (Correct answer)
- The vertical depth of a mineralized zone
- The angle of dip relative to horizontal
- The thickness of an ore seam
Correct answer: The direction of a vein or ore body along the horizontal
Strike is the compass direction of a horizontal line on an inclined geological surface such as a vein or bed.
Question 3: Which type of metamorphism occurs when rock is altered by heat and pressure from a nearby igneous intrusion?
- Contact metamorphism (Correct answer)
- Regional metamorphism
- Dynamic metamorphism
- Burial metamorphism
Correct answer: Contact metamorphism
Contact metamorphism results from heat-driven alteration in the zone surrounding a magmatic intrusion, often creating economically valuable skarns.
Question 4: A porphyry copper deposit is primarily associated with which geological setting?
- Subduction zone magmatic arcs (Correct answer)
- Mid-ocean ridge spreading centers
- Continental rift zones
- Passive continental margins
Correct answer: Subduction zone magmatic arcs
Porphyry copper deposits form in magmatic arcs above subduction zones where calc-alkaline magmas intrude and release copper-bearing hydrothermal fluids.
Question 5: What is the primary purpose of an induced polarization (IP) survey in mineral exploration?
- To detect disseminated sulfide minerals in subsurface rocks (Correct answer)
- To measure the thickness of overburden
- To determine surface topography
- To identify uranium deposits via radioactivity
Correct answer: To detect disseminated sulfide minerals in subsurface rocks
IP surveys measure the chargeability of rocks, effectively detecting disseminated sulfides which are often associated with porphyry and epithermal deposits.
Question 6: Which rock texture, characterized by large crystals surrounded by fine-grained groundmass, is commonly associated with porphyry ore deposits?
- Porphyritic texture (Correct answer)
- Pegmatitic texture
- Granular texture
- Foliated texture
Correct answer: Porphyritic texture
Porphyritic texture results from two stages of cooling and is the defining characteristic of porphyry intrusions that host large copper-molybdenum deposits.
Question 7: In geochemical sampling for mineral exploration, what is a 'pathfinder element'?
- An element that occurs with an ore metal and signals its presence nearby (Correct answer)
- The primary metal being explored for
- A laboratory standard used for calibration
- An element that blocks detection of target metals
Correct answer: An element that occurs with an ore metal and signals its presence nearby
Pathfinder elements like arsenic for gold or molybdenum for copper disperse more widely than the ore metal and can indicate the presence of a deposit.
CMA Geology & Mineral Exploration 2
Which geophysical method measures variations in Earth's gravitational field to detect subsurface density contrasts?