differentiation of magma Flashcards
continous reaction sereies (bowens sereis)
ca rich plagiocase feldspar
|
na rich plagioclase feldspar
discontinuos reaction seres (bowens)
olivine
pyroxene
hornblende
biotite
last section of bowens reaction sereis
K feldspar
muscovite mica
quartz
high temp =
first to crystalise (deeper)
low temp=
last to crystalise (shallowe)
mafic rocks form at which temps
high temps (1st to crystallise)
silicic rocks form at which temps
low temp (last to crystallise)
processes of magmatic differentiation
fractional crystalisation
gravity settling
filter pressing
what is fractional crystalisation
as olivine and pyroxene form at high temps, they use iron and magnesium from magma and plagioclase crystals use calcuim. resulting in magma becoming depleted in mg fe and Ca. remaining liquid becomes enriched by silica pottasium and sodium. over time comp of magma chnages from the original
what is gravity settling
crystalls are generally denser( ie olivine) than surrounding crystals
they sink to form a layer at the base of the intrusion
gravity removes crystals from remaining liquid so they dont react with magma left.
form a cumulative layer
what is a cumulative layer?
layer of dense early formed crystals at bas of an intrusion or magma chamber
what is filter pressing
during crystallisation of magma there is a point where crystals and liquid exist together as slush. due to weight of crystals liquid is sweezed out forming a seperate layer above . liquid lacks the minerals in early crystals and enriched in elements that form felsic minerals
what are the results of of magmatic deifferentiation
major layered intrusions
examples of major layered intrusions
palisades sill, New jersey
skaergaard intrusion, greenland
