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

Question

Quizplus · Accepted Answer

When a rock is metamorphosed to biotite hornfels facies, it typically results in the growth of large biotite crystals called porphyroblasts. These are irregularly shaped and have randomly oriented platelets, giving the rock a spotted appearance. The other answer choices are not typically associated with this type of metamorphism.

A Massive Mudstone Metamorphosed to Biotite Hornfels Facies Would Have