GEOS102-IGNEOUS ROCKS

crystalline granular

completely made up of crystals, can be coarse or fine grained

porphyritic

smaller phenocrysts sititing in a groundmass

glassy texture

magma which has been quenched instantly

vesicular

bubbly texture in an igneous rock

pyroclastic

formed by exploded fragments of magma

mafic

higher Fe+Mg+Ca content in an igneous rock, higher temperature

felsic rock

higher silica content in an igneous rock lower temperature

extrusive rock

volcanic igneous rock

intrusive

more crystalline, plutonic igneous rock, made from lava intrusions

basalt

mafic, porphyritic/extrusive rock

gabbro

mafic, crystalline/intrusive rock

Andesite

intermediate, porphyritic/extrusive rock

Diorite

intermediate, crystalline/intrusive rock

Rhyolite

felsic, porphyritic/extrusive rock

Granite

felsic, crystalline/intrusive rock

mafic minerals

olivine, pyroxene, Ca rich plagioclase

felsic minerals

quartz, Na-rich plagioclase, orthoclase, Muscovite, Biotite

hot spots/intraplate

mantle plume, increased temperature, same pressure

convergent plate boundary (subduction zone)

changing dry solidus to wet solidus by adding water. low temperature, high pressure. (one plate going under another plate)

divergent plate boundary (mid-ocean ridge)

decrease in pressure, no increase in temperature

1300 degrees

Highest temperature for crystallisation

650 degrees

lowest temperature for crystallisation