The figure shows chemogenic mineral projections for Facies P and Facies Q. Which one of the following reactions best represents change from Facies P to Facies Q?
Show Hint
To determine the correct reaction, focus on the minerals present in both facies and match the chemical transformations accordingly.
Step 1: Understanding the mineral projections.
In the given diagram, we are presented with two facies: Facies P and Facies Q. Each facies is characterized by specific mineral compositions that are projected on the triangular diagrams. These minerals include:
- Crn (Corundum)
- Grs (Grossular)
- Wo (Wollastonite)
- An (Anorthite)
- Sil (Sillimanite)
- Qtz (Quartz)
Our goal is to identify the chemical reaction that best represents the transformation from the minerals in Facies P to the minerals in Facies Q.
Step 2: Analyzing the reaction options.
- Option (A) Wo + An = Sil + Qtz: This reaction suggests that Wollastonite (Wo) and Anorthite (An) from Facies P are reacting to form Sillimanite (Sil) and Quartz (Qtz), which are present in Facies Q. This reaction matches the mineral projections from Facies P to Facies Q.
- Option (B) An + Sil = Wo: This reaction suggests that Anorthite (An) and Sillimanite (Sil) from Facies P are reacting to form Wollastonite (Wo). However, this does not match the mineral composition of Facies Q, as Sillimanite and Anorthite are both found in Facies P but are not part of the products in Facies Q.
- Option (C) Wo + Crn = Grs: This reaction would involve the formation of Grossular (Grs) from Wollastonite and Corundum, but this is not the correct reaction to represent the change from Facies P to Facies Q.
- Option (D) Grs + Qtz = Wo + An: This reaction would suggest that Grossular (Grs) and Quartz (Qtz) from Facies Q are reacting to form Wollastonite (Wo) and Anorthite (An), which does not fit the change between the two facies.
Step 3: Conclusion.
The correct reaction that best represents the change from Facies P to Facies Q is Wo + An = Sil + Qtz, as it involves the transformation of the minerals in Facies P to those in Facies Q. Hence, the correct answer is (A).
\[
\boxed{\text{Wo + An = Sil + Qtz}}
\]
