Geology 1500-11 EXAM 2 CH 7 METAMORPHIC ROCKS

What phenomena cause metamorphism?

-Mountain building (regional) -plutonism (formed underground, the intrusion of magma -cools below the surface) -volcanism -faulting shear zone (structural discontinuity surface in the Earth's crust and upper mantle. Deformation) -meteoric impact (shock wave and heat - craters?) -mantle convection (currents carrying heat from the interior to the planet's surface) deformitity -water-rock interactions

What is a protolith and why does it matter in metamorphic rock formation?

A protolith is the parent rock that later forms a metamorphic rock. This is important because it will determine what materials are available to metamorphosed.

hydrothermal metamorphism

Chemical alterations that occur as hot, ion-rich water circulates through fractures in rock.

Non-foliated vs foliated metamorphic rocks

Foliated metamorphic rocks gneiss, phyllite, schist, and slate -have a layered or banded appearance that is produced by exposure to heat and pressure. Non-foliated metamorphic rocks -Hornfels, marble, quartzite, and novaculite -do not have a layered or banded appearance.

metamorphic foliation and how is it formed

Foliation is the repetition of parallel surfaces or layers in a metamorphic rock Ex. schistocity and gneissic layering -grains are broken down and regrown -Can give a striped or streaked appearance - give them the ability to split into thin sheets.

list the different type of metamorphic facies and the environments in which they form (8)

Geothermal gradient metamorphism; burial metamorphism; Dynamic metamorphism: subduction zone metamorphism: regional metamorphism: contact metamorphism: hydrothermal metamorphism: impact metamorphism

how are metamorphic rocks different from igneous and sedimentary rocks?

Igneous - a rock formed by the crystallization of molten magma Sedimentary rocks are weathered products form when sediments become compacted and cemented. Metamorphic rocks form when existing rocks are changed by heat, pressure, or solution

Explain how a geologists use index minerals.

Index minerals are used to describe the type of metamorphic environment they belong to.

Explain the difference between low grade and high-grade metamorphic rocks

Low-grade metamorphic rocks are formed under lower temperatures and pressures Low-grade metamorphic- fine-grained (shale->slate) High-grade metamorphic rocks are formed at high temperatures and pressure High-grade metamorphic- coarse-grained (schist or hgneiss)

What two features characterize most metamorphic rocks?

MINERAL ASSEMBLAGE -minerals produced under the temperature and pressure regimes of metamorphism METAMORPHIC TEXTURE -grain arrangement -often involving foliation: a preferred alignment of platy grains -or alternating light and dark mineral bands)

explain the upper temperature limit of metamorphism

Metamorphic rocks do not melt. The upper temperature limit for metamorphism is 800ºC. Above this temperature, rocks begin to melt, which by definition, is no longer a metamorphic rock.

What is Metasomatism ?

Metasomatism undergoes a metamorphic hydrothermal process. (hot water makes its way into the system of a metamorphic rock but the hot water carries minerals that transfer onto the rock) - the before minerals are altered/ transferred - along with the hot water minerals fluid transport of chemical substances into or out of the rock

What are the factors that control metamorphism?

Protolith (PARENT ROCKS) TEMPERATURE and PRESSURE (direction, amount and stress) The presence or absence of PORE FLUIDS RATE and DURATION of DEFORMATION affect the type of metamorphic rocks that will form.

subduction zone metamorphism

Sediments and oceanic crust are subducted fast enough that pressure increases before the temperature blueschist.

How does slate differ from phyllite? How does phyllite differ from schist? How does schist differ from gneiss? in order (heat + pressure) 4

Slate (shale) - from low-temperature and low-pressure -slaty cleavage arises from clay minerals Phyllite -higher temperatures and pressures -cause clay grains within slate to be recrystallized to form mica grains ( a silky luster) unlike dull slate Schist -higher heat and pressure - its mica grains are large, visible plates -unlike the smooth, tiny mica grains within phyllite. Gneiss -alternating bands or swirls of light- and dark -colored minerals, including additional minerals -besides mica (quartz, feldspar, amphibole)

What is the difference between slaty cleavage and schistosity?

Slaty cleavage(foliation) is cleavage made of thin slates of rock. (slate is fine clay, low grade metamorphic ). Schistosity is when mica and chlorite crystals begin to grow. these platy materials are large enough to be seen with the unaided eye (medium to high grade metamorphism)

What are the difference between blue-schist and greenschist?

blueschist -blue metamorphic rock containing glaucophane --formed under conditions of high pressure and low temperature greenschist -green metamorphic rock containing green minerals such as chlorite, serpentine, and epidote --formed at low temperature and pressure,

contact metamorphism

changes in rock caused by the heat of a nearby magma body; also called thermal metamorphism

What are the agents that change rocks through metamorphism?

heat, pressure, and hydrothermal solution.

Geothermal gradient metamorphism

heating by a plutonic intrusions Plutonic rocks are formed underground. They involve the "intrusion" or insertion of magma between other rocks which then cools below the surface.

What is a metamorphic grade, and how can it be determined? How does grade differ from facies?

indicates the intensity of metamorphism, meaning the amount or degree of metamorphic change. (high grade) facies is a restricted range of temperatures and pressures defined by the presence of key minerals.

Why are hornfels nonfoliated?

metamorphic rock may lack foliation (that it has not been subjected to high pressure) Hornfels is a metamorphic rock that can form when a rock is subjected to high temperatures. Hornfels, which often forms when magma or lava touches other rock, is nonfoliated.

regional metamorphism

metamorphism associated with large-scale mountain-building processes pressure and temperature alternation due to orogenesis (earth's crust is folded and deformed by lateral compression to form a mountain range.)

dynamic metamorphism

metamorphism in fault zones where rocks are subjected to a high differential pressure San Andres

impact metamorphism

metamorphism that occurs when meteorites strike Earth's surface

Burial metamorphism produces

nonfoliated rocks only increase pressure and temperature by deep burial in a basin

Non-foliated

parent rock (protolith) - metamorphic rock - Gabbro ( or Basalt) -> Amphibolite ( dominated by amphibole minerals) - mudstone -> hornfels (alternation by heating, associated w plutonic intrusion) - sandstone -> quartzite (sand grains in the protolith recrystallize and fuse ) -limestone -> marble (coarsely crystalline calcite of dolumite, extensive recrystallization)