GL101 Lecture 6: GL101 Lecture : Chapter 7
Document Summary
Metamorphism: where in the rock cycle, when a rock is subjected to temperature or pressure very different from where they formed, during metamorphism the rock remains solid, parent rock can be any type. Composition of parent rock: texture and specific mineral makeup depend on physical processes during metamorphism, only in extreme in cases of fluid migration: metamorphic rocks change in composition from parent rocks. Influences mobility & reactivity of fluids: 1. Fro(cid:373) earth"s i(cid:374)ter(cid:374)al heat: different minerals are stable at different temperature change occurs at different times. Chemically active fluids: at depth, higher temperature and pressure cause minerals to dehydrate, fluids may change the composition of surrounding host rock: metasomatism. Ions in water, migrate in crystal structure: recrystallization. Metamorphic grade and index minerals: metamorphic grade: intensity/degree of metamorphism. Index minerals: sequential appearance & stable at progressively higher pressure and temperature. Low grade = chlorite (around 200 degrees celsius)
