GEOL 1010 Lecture Notes - Lecture 9: Blueschist, Biotite, Subduction
24 Sep 2016
School
Department
Course
Professor
Document Summary
Clays recrystallize into larger, aligned clays to yield a slate. Clays neocrystallize into tiny, aligned micas in a phyllite. Mica recrystallize and grow large to form a schist. New minerals grow in the schist, like garnets. Micas decompose; elements recombine into new minerals. Neocrystallization yields quartz and feldspar in a gneiss. Factors controlling metamorphism: parent rock (protolith): usually no new elements (other than water) are added to rocks during metamorphism. Slate ---> phyllite ---> schist ---> gneiss ---> migmatite (increasing metamorphic grade [intensity]) (felsic melts, mafic doesn"t: heat (t): minerals stable over finite temperature range. Mineralogy can change: pressure (p): increases with depth. Formation and stability of many minerals depends on both p and t. Confining pressure: same in all directions (ex: scuba diving, squished from all directions. Differential pressure of differential stress: not equal in all directions. (ex: dough ball, squishing it from both sides) at high t and p, differential stress deforms rocks.
