Mod 5 Metamorphism and Metamorphic Rocks PDF

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● Metamorphic rocks: changes in texture and possibly mineralogy as a result of the application of heat and pressure ● Foliation: alternating layers of dark and light minerals, different process than sedimentary, process of separation is metamorphic ● Pot making imitates metamorphosis: crystallization after heat means that water won’t be absorbed again ○ Clay is protolith, metamorphic product is mica ● Measured in kilobars, metamorphosis measured from low (lower pressure and temp) to high grade (low pressure and high temp) ○ Occurs between lithification and the “magma line” ● Neocrystallization: start of randomly distributed, when stress is applied the minerals reorient and form perpendicular to stress, creates new crystals ● As grade increases, size of crystals and coarseness increases- foliation subtle inlow grade, obvious in high grade- slate is slaty (duh), schist has schistosity, migmatite has banding ● Recrystallization: protoliths with void spaces form non foliated rocks (sandstone to quartzite, limestone to marble) ● Subsidence, burial metamorphism: increased pressure on rocks as they’re buried (low grade) ● Tectonic burial/ regional metamorphism: pressed down due to tectonic movement, leads to increased temperature and pressure over a large region (low grade) ● Magmatic intrusion/ contact metamorphism: magma sends off heat to surrounding rock, pluton subject to contact metamorphism, doesn’t change pressure much but does increase temperature (intermediate or high grade)

● Dynamic metamorphism: happens at relatively low temp but high pressure and movement, against fault planes, subject to intense shear and rotational stress ● Metamorphism at convergent boundaries: high temp low pressure at volcano, high temp high pressure in lithosphere, dehydration metamorphism as ocean crust is subducted, low-temp high pressure at actual collision point- complicated systems ● Shock metamorphism: happens mainly with meteorite strikes, heat and pressure generated vaporizes the meteorite and metamorphoses rock nearby mostly into glass (like the glass formed at nuke test sites) ● Shale protolith: most common sedimentary rock, made from clay particles, end product of weathering, low energy environments ○ Shale to slate transition is exactly like the pottery dealio- shale is clay, slate has mica ○ Slate is harder, won’t fall apart in water, harder to weather away, cleaves along parallel surfaces because mica minerals are flat and tabular like clay in shale ○ Adding pressure changes crystal size of mica so it turns to phyllite and the crystals reflect light (shiny rock), deeper and add more heat = schist with lots of muscovite mica and bigger index mineral nodules within mica Quiz: 1. The direct cause of contact metamorphism is: igneous intrusion 2. Metamorphism can involve the recrystallization of minerals. true 3. Mineral that commonly defines the foliation in phyllite. Chlorite 4. Shock metamorphism occurs only through lightning strikes. False 5. Metamorphic rocks are named based on the: protolith and metamorphic grade

6. All metamorphic changes to a rock occur in the solid state. True 7. When rocks are metamorphosed, many minerals tend to: grow perpendicular to the direction of maximum stress 8. Which of the following metamorphic rocks cannot form from a shale? Marble 9. Mylonite results from partial melting of felsic minerals during high grade metamorphosis. False 10. Low grade metamorphosis of ________ produces slate. shale...