A massive mudstone metamorphosed to biotite hornfels facies would have ________.
A) irregular spots of randomly oriented biotite platelets called porphyroblasts
B) biotite defining wavy parallel foliations throughout the rock
C) remnants of biotite, now mostly recrystallized to garnet in discreet layers
D) breccia of angular biotite clasts crushed and sheared out of shape

Question

Quizplus · Accepted Answer

Porphyroblasts are larger crystals that grow in a finer matrix during metamorphism, and biotite hornfels facies indicates a type of contact metamorphism where biotite can form as porphyroblasts in the rock.

A Massive Mudstone Metamorphosed to Biotite Hornfels Facies Would Have