What describes metamorphism in the ductile zone?

• A. Changes in mineral composition and texture driven by temperature, pressure, and fluids
• B. Growth of sedimentary layers
• C. Erosion of rocks
• D. Cracking into faults

Answer: (A)

Metamorphism in the ductile zone involves rocks changing their mineral makeup and texture because of higher temperature, higher pressure, and the presence of fluids. Under these conditions minerals can recrystallize and new minerals can form, reorganizing the rock's internal structure without fracturing it. This is why ductile metamorphism often produces foliated textures, where minerals align or segregate into layers as rocks deform plastically. The role of fluids is to facilitate reactions and transport ions, accelerating changes that create metamorphic rocks like slate, phyllite, schist, or gneiss.

This understanding is different from growing sedimentary layers (deposition), eroding rocks (wearing away), or cracking rocks into faults (brittle fracture). In the ductile zone, rocks deform smoothly rather than break, allowing metamorphic changes to progress.