Question

The schematic diagram given below shows textual relationship among garnet, muscovite, biotite and kyanite in a metapelite. Biotite defines S1 foliation and muscovite defines S2 and S3 foliations. S1, S2, and S3 fabrics were developed during distinct deformation events D1, D2, and D3, respectively. Which one of the following represents the pre-D3 mineral assemblage? 

• A. kyanite + garnet + biotite
• B. garnet + biotite + muscovite
• C. garnet + kyanite + muscovite
• D. biotite + garnet + kyanite

Hint:

When determining pre-D3 assemblages, focus on the minerals present before the final foliation event. Pay attention to the textural relationships defined by each foliation.

Answer 1

The Correct Option is B

Step 1: Understand the Textural Relationship.
The diagram shows the relationship between garnet, biotite, muscovite, and kyanite during distinct deformation events. Each mineral is aligned with a specific foliation.
Step 2: Analyze Pre-D3 Mineral Assemblage.
- S1 is defined by biotite.
- S2 and S3 are defined by muscovite.
Thus, the mineral assemblage before deformation event D3 (pre-D3) would include garnet, biotite, and muscovite, as these minerals existed prior to the final foliation event (S3).
Step 3: Conclusion.
The pre-D3 assemblage is represented by garnet + biotite + muscovite. Final Answer: \[ \boxed{\text{garnet} + \text{biotite} + \text{muscovite}} \]