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Difficulty: HardRock Types, Formation, and Economic Importance

Match each rock type listed in Group I with its corresponding parent rock and specific formation process in Group II.

  • QuartziteThermal or regional metamorphism of sandstone causing quartz grains to recrystallize into an interlocking network
  • MarbleMetamorphism of calcareous sedimentary rock such as limestone, resulting in coarse calcite crystal growth
  • SchistMedium-to-high grade regional metamorphism of argillaceous shale producing prominent platy foliation
  • AnthraciteHigh-grade thermal and compressive alteration of sedimentary bituminous coal into hard, lustrous carbon

Answer

Quartzite matches with thermal or regional metamorphism of sandstone causing quartz grains to recrystallize; Marble matches with metamorphism of calcareous sedimentary rock such as limestone; Schist matches with medium-to-high grade regional metamorphism of argillaceous shale; Anthracite matches with high-grade thermal and compressive alteration of sedimentary bituminous coal.
Each metamorphic rock is correctly aligned with its original parent rock (protolith) and corresponding thermodynamic transformation process: Quartzite stems from sandstone recrystallization, Marble from limestone recrystallization, Schist from shale foliation, and Anthracite from metamorphic distillation of bituminous coal.

Step-by-Step Solution

1
Analyze the mineral composition and origin of Quartzite.
Quartzite consists predominantly of recrystallized quartz grains originating from siliceous sandstone.
Under elevated heat and pressure, original quartz sand grains in sandstone recrystallize into a dense interlocking matrix.
2
Identify the parent rock (protolith) of Marble.
Marble forms through the metamorphism of calcareous rocks like limestone or dolomite.
Thermal contact or regional metamorphism drives the recrystallization of calcite micro-crystals into larger interlocking calcite grains.
3
Determine the metamorphic grade and protolith of Schist.
Schist develops from fine-grained argillaceous rocks (shale) undergoing moderate-to-high grade regional metamorphism.
Directed compressive stress aligns platy mica and chlorite minerals into distinct foliated bands visible to the naked eye.
4
Evaluate the formation mechanism of Anthracite.
Anthracite is produced by metamorphic alteration of organic sedimentary bituminous coal.
Extreme tectonic pressure and geothermal heat drive off volatile gases, yielding ultra-high carbon concentration.

Key Concept

Metamorphic Protoliths and Transformation Mechanisms
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Topics

Rock Types, Formation, and Economic Importance

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