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: Identify the minerals.
Facies P holds wollastonite (Wo) and anorthite (An). Facies Q holds sillimanite (Sil) and quartz (Qtz). We want the reaction that turns one set into the other.
Step 2: Set up the change.
Going from P to Q means the reactants come from P and the products appear in Q. So Wo and An must be on the left, Sil and Qtz on the right.
Step 3: Write the reaction.
This gives \[ Wo + An = Sil + Qtz. \] This matches the projections, with P minerals breaking down to form the Q minerals.
Step 4: Reject the others.
The other reactions either make Wo or use grossular and corundum, which are not the right pair for this P to Q change. So they do not fit.
Step 5: Final choice.
The correct reaction is Wo plus An gives Sil plus Qtz.
\[ \boxed{\text{Wo + An = Sil + Qtz}} \]
