Metamorphism and metamorphic rocks - review questions for chapter 5

(also look at questions on p.163 in the textbook)

Metamorphic rocks, like igneous and sedimentary rocks, contain clues that can be read in order to decipher something about their history. The texture and composition of an igneous rock tell us about the source of the magma and the environment in which the rock crystallized. The texture, composition, and sedimentary structures of a sedimentary rock tell us something about the source of the sediment, the way it was transported, and the processes at work in the depositional environment. Although the processes are different, the textural characteristics of a metamorphic rock and the particular assemblage of minerals found in that rock may provide important clues that tell us about the environment in which metamorphism took place. Typically the metamorphic environment, unlike the sedimentary environment, is located at some depth beneath the earth's surface, most often in the midst of a subduction zone, a region of continental collision, a fault zone, or in close proximity to an intruding magma body. Although we generally cannot observe the processes of metamorphism at work, the intensity and style of deformation tells us something about the forces that have affected the rock; the particular assemblage of minerals, and the extent to which some of the pre-existing mineral grains have recrystallized or grown together, can tell us something about the temperature and pressure conditions under which the rock evolved.