metamorphism Flashcards
what is metamorphism?
iso chemical process by whihc rocks are changed by either tem, pressure or both.
what happens to the comp of the new rock?
stays the same as the parent rock
what can metamorphism result in
destruction of fossils/beds/sed. structures hardening of the rock change in colour alignment of minerals growth of new metamorphic minerals
temp increses with…
DEPTH
where do high temps occure
near igneous intrusions
temp increases has what effect on rate of metamorphic reaction
rate of metamorhic reaction increases
pressure increases with..
DEPTH
term for no elements added or removed (exept water and CO2)
isochemical
pressure exerted by fluids between grains in a pourous rock?
PORE PRESSURE
pressure from weight of overlying rock bringing minerals togethers
LOAD PRESSURE
pressure from folding or faulting (usually over a short period of time)
TECTONIC PRESSURE/STRESS
why does metamprhic rate increase with tmep
many reactions need heat to take place
increases rate of ion diffusion between minerals
which are more common? pressure or temp dependent reactions
temp dependent reactions
how long do metamorphic reactions take
millions of years, temp and pressure conditions must remain over long periods of time for these reactions to take place
three types of metamorphism
contact
burial
regional
what is contact metamorphism
occurs adjacent to igneous intruisons
due to increase in temp of country rock
produces a metamorphic aureole
minerals not alligned due to low pressure
temp of contact metamorphism
more than 200 (HIGH)
pressure of contact metamorphism
LOW less than 200 MPa
what is burial metamorphism
occurs under sediments also in subdiction zones
can overlap with diagenisis
temp of burial metamorphism
less than 200 degrees (LOW)
pressure of burial metamorphism
HIGH-MEDIUM 200-1000 MPa
what is regional metamorphism
caused by collison of plates or subduction
large scale
alligned minerals due to pressure high
occure in cores of fold mountains
temp of regional metamorhism
around 200-700 degrees (LOW-HIGH)
pressure of regional metamorphism
LOW-HIGH 100-1000 MPa
what is foliation
texture of meta. rocks, formed by the preffered alignment of flat platy minerals
what is slaty cleavage
texture in fine grained rocks formed by low grade metamorphism. platy minerals re crysatlise perpendicular to the direction of stress applied during metamorphism so rock splits into sheets
foliated rocks produced by metamorphsim
slate
schist
gneiss
slate parent rock
shale
slate colour
dark grey
slate texture
slaty
fine
slate composition
clay minerals
msucovite mica
slate type and grade of metamorphism
low grade regional
schist parent rock
shale
schist colour
slivery green
schist compostion
muscovite and biotite mica
quartz
garnet
kyanite
schist texture
shisosity
medium 1-5mm
schist type /grade of metamo..
medium grade regional
gniess parent rock
shale
gniess colour
dark and light bands
gniess texutre
gnuessose banding
coars >5mm
gniess comp
biotite mica
mafic minerals
quartz
gniess grade/type metamrphsim
high grade regional
unfoliated rocks from metamprhsim
marble
quartzite
spotted rock
marble PARENT ROCK
limestone
marble COLOUR
white
marble TEXTURE
granoblastic
medium grain 1-5mm
marble COMP
calcite
marble TYPE OF METAMORPHSIM
contact or regional
quartzite PARENT ROCK
sandstone (composed of quartz)
quartzite COLOUR
white/grey
quartzite TECTURE
grano blastic
medium 1-5 mm
quartzite COMP
quartz
quartzite TYPE OF METAMORPHSIM
contact/regional
spotted rock PARENT ROCK
slate or shale
spotted rock COLOUR
dark with darker spots
spotted rock TEXTURE
slaty cleavage (if slate is parent rock) fine
spotted rock COMP
clay minerals
mica
spotted rock TYPE OF METAMORPHSIM
contact
what does granoblastic texure mean
meta rocks with equidiminsional interlocking crystals
what is a polymorph
mineral that occurs in differnt crystal forms but has same compostion
