Chapter 5 - Igneous Rock Flashcards
mafic dyke
a fracture in the rock that is filled with magma from beneath - different composition than surrounding rock
plutonic rock
rock that is formed from great depths within crust or mantle
phaneritic
minerals large enough to see with unaided eye
ex. granite
aphanitic
minerals too small to see
ex. phyolite
glassy
no obvious minerals
ex. obsidian
porphyritic
two distinct mineral sizes
ex. porphyritic basalt
vesicular
many holes or pits in rock surface caused by the trapping of escaping gas
ex. vesicular basalt
pyroclastic
fused, glassy fragments, ash, and blocks of rock from explosive volcanic eruption
ex. tuff
lava types
pahoehoe - smooth and ropy
Aa - sharp and jagged
phenocrysts
large crystals embedded in porphyritic rocks
mafic rocks
rocks that are more dense and contain more iron and magnesium
felsic rocks
rocks that are less dense and contain more silica
felsic rock examples
extrusive- rhyolite
intrusive- granite
intermediate rock examples
extrusive- andesite
intrusive- diorite
mafic rock examples
extrusive- basalt
intrusive- gabbro
ultramafic rock examples
extrusive- peridotite
intrusive- komatiite
Bowen’s reaction series
describes the order and process of magma crystallization
dike
magma tube that forms in cracks and crosses through layers of rocks
pluton
smaller body of magma
batholith
very large body of magma
xenoliths
solid pieces that have formed in magma (fragments of country rock)
sill
horizontal dike
laccolith
a sill that contains high pressure magma and lifts the crust above it
discordant intrusions
any magma body that cut across layers of country rock that they intrude
veins
mineral deposits within rock fractures that are foreign to surrounding country rock.
pegmatites
veins of extremely coarse-grained granite due to slow cooling process. water brings elements to crystallization sites.
important source of rare minerals, gemstones, and industrial metals
