Chapter 6 E2 Flashcards
changed form rocks; produced from preexisting igneous, sedimentary and metamorphic rocks
metamorphic rocks
takes place where preexisting rock is subjected to temperatures and pressures unlike those in which it formed
metamorphism
two types of metamorphism
contact (thermal) and regional metamorphism
occurs near a body of magma, changes are driven by a rise in temperature; caused by a hot body like an intrusive; doesn’t melt surrounding rock but changes it
contact or thermal metamorphism
directed pressures and high temperatures during mountain building; occurs along plate boundaries; produces the greatest volume of metamorphic rock
regional metamorphism
______ and _____ increase with depth in all regions
pressure and temperature
created by quick intense pressure
shock metamorphism like a meteor impact
there is high pressure metamorphism at _________; water is being subducted with the plate so very high pressure and low ___
subduction zones
temperatures
seafloor metamorphism
new crust is still hot and kind of fluffy so there is an exchange of cations easilyt
1300 degree celsius isotherm
everything below this line is hotter and molten
confining pressure
pressure from all directions; things just pile on top
directed pressure
usually pressure from two directions; occurs near the surface
folation
occurs due to directed pressure; the minerals turn perpendicular and flatten; also have the segregation of felsic and mafic materials
directed pressure causes sedimentary rocks such as shale to form
cleavage planes
metamorphic rock textures
foliated and non foliated
minerals are in a parallel alignment perpendicular to the compressional force
foliated texture of a metamorphic rock
contain equi-dimensional crystals; resembles a coarse-grained igneous rock
nonfoliated (massive) texture of a metamorphic rock
metamorphic textures from low grade of intensity to a high grade intensity of metamorphism
slate, phyllite, schist, gneiss, and migmatite
most abundant detrital sedimentary rock
shale
every metamorphic rock has a ____ rock
parent
porphroblasts
like garnet in schist
difference between marble and quartzite
scratch the glass; quartzite is harder
nonfoliated (granoblastic) rock; parent rock is limestone; large interlocking calcite crystals
marble
nonfoliated (granoblastic) rock; parent rock quartz sandstone; quartz grains are fused
quartzite
with nonfoliated rock you can’t tell immediately the grade of
metamorphism
as the intensity of the metamorphism increases ________ and __________ also increase
crystal size and coarseness of foliation; (pressure and temp are also increasing because they are the factors that increase the metamorphic intensity)
minerals you use to figure out where you are in the temperature pressure space
index minerals or isograds
_______ path is faster than the ______ path
prograde
retrograde
low grade metamorphism that is caused by the progressive increase in pressure
burial metamorphism
the four criteria of classifying a foliated rock
metamorphic grade
grain (crystal) size
type of foliation
banding
nonfoliated metamorphic rocks composed mainly of crystals that grow in equant shapes such as cubes or spheres rather than in platy or elongate shapes
granoblastic rocks
the process of transporting a rock from the earth’s interior back up to earth’s surface
exhumation
this type of foliation results in the segregation of lighter and darker minerals
gneiss
metamorphic rocks formed by _____ are rarely exposed at the earth’s surface for geologists to study
high pressure metamorphism
hot basaltic lava at a seafloor spreading center heats infiltrating seawater which starts to circulate through the newly forming oceanic crust by convection
seafloor metamorphism
the kind of change in a rock’s composition by fluid transport of chemical substances into or out of it
metasomatism
another name for pressure
stress
groupings of rocks of various mineral compositions formed under particular conditions of temperature and pressure from different parent rocks
metamorphic facies
