Question

Schistosity forms due to:
A. Dynamothermal metamorphism,
B. Contact metamorphism,
C. Plutonic metamorphism,
D. Thermal metamorphism. Choose the correct answer from the options given below:

• A. A only
• B. A and B only
• C. B, C and D only
• D. A, B and D only

Hint:

Schistosity forms mainly due to directed pressure during dynamothermal metamorphism.

Answer 1

The Correct Option is A

Concept:
Schistosity is a planar fabric in metamorphic rocks formed by parallel alignment of platy or flaky minerals.

Step 1: Understand schistosity.
Schistosity develops when minerals such as mica align under directed pressure and recrystallization. \[ \text{Directed pressure}+\text{recrystallization}\Rightarrow \text{schistosity} \]

Step 2: Check dynamothermal metamorphism.
Dynamothermal metamorphism involves both heat and directed pressure. This is the most suitable condition for schistosity formation. \[ A \text{ is correct} \]

Step 3: Check contact and thermal metamorphism.
Contact and thermal metamorphism are mainly caused by heat. They generally produce non-foliated textures rather than strong schistosity. \[ B \text{ and } D \text{ are incorrect} \]

Step 4: Check plutonic metamorphism.
Plutonic metamorphism is mainly associated with deep-seated pressure-temperature conditions, but schistosity is specifically related to directed stress in dynamothermal metamorphism. \[ C \text{ is not selected} \] Thus, the correct answer is: \[ A \text{ only} \] \[ \therefore \text{Correct Answer is (A)} \]