Composition of Igneous Composition of Igneous RockRock

Joy C. VillarazaJoy C. Villaraza

1.1. CompositionComposition

A.) Sialic or FelsicA.) Sialic or Felsic

B.) IntermediateB.) Intermediate

C.) MaficC.) Mafic

D.) UltramaficD.) Ultramafic

2. Refferences2. Refferences

Composition of Igneous Composition of Igneous rocksrocks

• Chemical compositionChemical composition

• Color or mineralsColor or minerals

Sialic or granitic or Sialic or granitic or felsicfelsic

• Dominated by Dominated by silicon and silicon and aluminum (SiAl)aluminum (SiAl)

• Light in colorLight in color

• Forms a stiff Forms a stiff (viscous) lava or (viscous) lava or magmamagma

Granite

•Rhyolite Rhyolite

Intermediate (or andesitic)Intermediate (or andesitic)

• Composition between sialic and Composition between sialic and maficmafic

• Andesite(aphanitic)Andesite(aphanitic)

• Doirite(phaneritic)Doirite(phaneritic)

Mafic (or basaltic)Mafic (or basaltic)

• Contains abundant ferromagnesian Contains abundant ferromagnesian minerals (magnesium and silicates)minerals (magnesium and silicates)

• Dark in color (dark gray to black)Dark in color (dark gray to black)

• Forms a runny (low viscosity) lavaForms a runny (low viscosity) lava

• BasaltBasalt

• gabbrogabbro

UltramaficUltramafic

• Almost entirely magnesium and iron Almost entirely magnesium and iron silicates (ferromagnesian minerals)silicates (ferromagnesian minerals)

• Commonly found as xenoliths in Commonly found as xenoliths in basaltic lavasbasaltic lavas

• Peridotite(phaneritic)Peridotite(phaneritic)

Igneous Rock Composition Chart

Felsic Intermediate Mafic

   

   

Bowen’s ReactionsBowen’s Reactions

• characterize the process of characterize the process of crystallization magma.crystallization magma.

• differentiation as magma coolsdifferentiation as magma cools

http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/mincomp.htmlhttp://hyperphysics.phy-astr.gsu.edu/hbase/geophys/mincomp.html

http://facweb.bhc.edu/academics/science/harwoodr/Geol101/labs/igneous/Texture.htm#Phaneritic

http://www.gpc.edu/~pgore/geology/geo101/igneous.htm