Question

On the basis of the following schematic diagram, choose the CORRECT statement(s). 

• A. Minerals X and Y predate matrix foliation (S2).
• B. Mineral X grew after the development of matrix foliation (S2).
• C. Mineral Y grew during or after the development of internal foliation (S1).
• D. Minerals X and Y postdate matrix foliation (S2).

Hint:

Minerals enclosing an earlier foliation (S\textsubscript{1}) but cut by a later one (S\textsubscript{2}) → Pre-S\textsubscript{2} porphyroblasts.

Answer 1

The Correct Option is B, C

Step 1: Interpreting the diagram.
The diagram shows two sets of foliations — S\textsubscript{1} (internal) and S\textsubscript{2} (matrix foliation). Mineral X shows no internal fabric and is overprinted by S\textsubscript{2}, whereas mineral Y encloses an older foliation S\textsubscript{1}, both being overprinted by S\textsubscript{2}.
Step 2: Interpretation.
Both minerals (X and Y) existed before the development of the matrix foliation S\textsubscript{2}, as they are truncated or overprinted by it. Mineral Y also preserves an internal foliation (S\textsubscript{1}), indicating growth during or after S\textsubscript{1} but before S\textsubscript{2}.
Step 3: Conclusion.
Hence, both minerals X and Y predate matrix foliation (S\textsubscript{2}).