Examkin

Question

Difficulty: Very hardRock Types, Formation, and Economic Importance

Geological mapping along an active fold mountain belt reveals a progression of rocks exhibiting distinct foliated textures, ranging from fine-grained slate to coarse-grained gneiss. Which of the following statements correctly explains the process responsible for this texture progression and the resulting economic application of gneiss?

  1. High-grade regional metamorphism driven by intense heat and directed pressure causes progressive mineral recrystallization and foliation, making gneiss valuable as a durable construction aggregate.Answer
  2. B
    Thermal contact metamorphism caused exclusively by localized magma intrusion recrystallizes organic sedimentary deposits into coarse banded rock suitable for agricultural lime production.
  3. C
    In-situ chemical weathering and mass wasting alter fine clay sediments into coarse foliated bands used primarily as raw material for cement manufacturing.
  4. D
    Chemical precipitation of dissolved minerals in shallow lacustrine basins forms coarse banded structures utilized as impermeable petroleum cap rocks.

Answer

High-grade regional metamorphism driven by intense heat and directed pressure causes progressive mineral recrystallization and foliation, making gneiss valuable as a durable construction aggregate.
Regional metamorphism over vast mountain-building zones Subjects parent rocks to intense differential stress and high heat, driving progressive recrystallization from fine slate to coarse, banded gneiss. Gneiss has high compressive strength and durability, making it an excellent material for heavy construction foundations and aggregate.

Step-by-Step Solution

1
Analyze the rock texture progression described in the stem.
The sequence from fine-grained slate to coarse-grained gneiss represents increasing grade of regional metamorphism.
Large-scale tectonic pressure and geothermal heat during mountain building alter minerals dynamically, forming foliated textures.
2
Evaluate the metamorphic process and structural characteristics of gneiss.
Gneiss exhibits distinct mineral banding (alternating light and dark minerals) due to high-grade recrystallization under directed stress.
This sets regional metamorphism apart from contact metamorphism or sedimentary deposition.
3
Determine the economic utility of gneiss based on its physical properties.
Due to its high compressive strength, density, and resistance to weathering, gneiss is extensively quarried for building stone, road metal, and coarse aggregates.
Economic applications directly depend on physical durability derived from metamorphic crystallization.

Key Concept

Regional Metamorphism and Economic Importance of Metamorphic Rocks
Estimated Time:1m 30s
Rate this question

Topics

Rock Types, Formation, and Economic Importance

More questions from this topic