Igneous Rocks Flashcards
B. Intermediate/Andesitic Composition (2)
25 percent dark silicate minerals
explosive volcanic
A. Granitic/Felsic Rock (2)
Continental Crusts,
Light
C. Basaltic/Mafic Rock (3)
Ocean floor/volcanic islands,
Dark Silicates and calcium-rich feldspar
higher density than granite
Felsic
Feldspar and Silica
Mafic
Magnesium and Ferrum
Ferrum
Iron
D. Ultramafic Composition (3)
magnesium, iron, silicates (same as mafic)
Ferromagnesian
iron/magnesium
Fewer Large Crystals
Slow Cooling
Many Small Crystals
Fast Cooling
Glass (Obsidian)
very fast cooling
Texture
Size Arrangement of Mineral Grains
Vesicular Texture
Rapid Cooling, gas escapes through hole
Aphanatic Texture
Fine grained, rapid cooling, some vesicles, rapid cooling
Phanertic Texture
Coarse-grained texture, slow cooling, large visible crystals
Porphyritic Texture
large crystals embedded in matrix of smaller crystals, multiple cooling rates, formed at different temperatures
two distinct grain sizes
Pyroclastic Texture
Fragmental Appearance (like sedimentary rock)
Pegmatitic Texture
Exceptionally coarse grained, formed in late stages of crystallization of granitic magmas
Phenocrysts
Large Crystals
Groundmass
Smaller Crystals
Rhyolite has
glass fragments and seciles
Rhyolite Texture
Aphanitic
Rhyolite vs Granite
less common, less voluminous, extrusive
Granite Composed of (3)
Quartz, Feldspar, Mica
Granite Properties (4)
FelsicCoarse GrainedIgneousLight Colored Silicates
Light Colored Silicates (2)
Quartz and Potassium Feldspar
DARK Igneous Examples (5)
Ferromagnesium silicatesOlivinePyroxeneAmphiboleBoitite Mica
Light Igneous Examples (6)
Non-Ferromagnesium silicatesQuartzmuscovitemicasfeldspars
Texture of “Basalt”
Aphanatic
Most Common Extrusive Rock
“asalt”
“Basalt” Origin
Volcanic
“Basalt” Composition (Igneous)
calcium-rich plagioclase feldspar
Andesite Properties (2) IGNEOUS
Volcanic ORiginAphanitic Texture
Diorite Texture IGNEOUS
Coarse Grained
Plutonic (intrusive ingeous ) equivalent of andesite
diorite
Rhyolite IGNEOUS Properties (3)
Extrusive equivalent of graniteMay contain glass fragments and vesiclesless voluminous and common than granite
“Rhyolite” IGNEOUS Texture
Aphanitic
“Obsidian” IGNEOUS Texture
dark/glassy
“Pumice” IGNEOUS Properties (3)
frothy/voidsvolcanicglassy
Granitic/Felsic Minerals (2)
Quartz/Potassium Feldspar
Andesitic/Intermediate Minerals (2)
Amphibole/Plagioclase Feldspar
Basalatic/Mafic Minerals (2)
Pyroxene/Plagioclase Feldspar
Ultramafic Minerals (2)
Olivine, Pyroxene
High Temp to Low Temp
Ultramafic->Felsic
Continuous Series of Crystallization
BRS
Calcium Rich->Sodium Rich (Plagioclase Feldspar)
Ultramafic->Felsic
Discountinuous Series of Crystallization (BRS)
Olivine, Pyroxene, Amphibole, Biotite (Ultramafic, Felsic)
First to Crystallize
Olivine
1/3 Magma Crystallized
Melt depleted in iron, mag, calcium