Transcript Igneous Rocks

What do rocks tell us
about the Earth?
 Formed
from the cooling and crystallization of
magma
– Molten rock beneath the Earth’s surface
(800 -1200°C to melt rock)
 Magma
 Lava
– Magma that flows out onto Earth’s surface
 Very
similar to
elements found in
Earth’s crust
 O, Si, Al, Fe, Mg, Ca,
K and Na
 Silica
- Most
abundant
What is wrong with this picture?
 Extrusive
Igneous
Rocks
• Fine grained
igneous rocks that
cool quickly on
Earth’s surface
Obsidian
Extrusive
Small Crystals
Cooled Fast
• Intrusive Igneous
Rocks
– Coarse grained
igneous rocks
that cool slowly
beneath Earth’s
surface
Granite
Intrusive
Large Crystals
Cooled Slow
 Felsic
(Granitic)
• Light colored, High silica content, contain
quartz and feldspars
Felsic Igneous Rock
•Mafic (Basaltic)
–Dark colored, rich in iron and magnesium
•Ultra Mafic
–Low silica content, very high levels of Fe
and Mg
Mafic Igneous Rock
 Porphyritic
Rocks
• Rocks characterized by large well-formed crystals
surrounded by fine grained crystals of the same mineral
 Vesicular
Rocks
• Spongy looking rock whose gas bubbles have broken
 Partial
Melting
• Process where some minerals melt at low
temperatures while other minerals remain
solid (Melting Points)
• Example: Ice Cube and Wax Candle
 Fractional
Crystallization
• Process where different minerals form at
different temperatures
 Bowen’s
Reaction Series
• Predictable, dual branched pattern in which
minerals crystallize from cooling magma
 Veins
• Igneous rock intrusions that contain ores (Au and Quartz)
 Pegmatites
• Vein deposits of extremely large grained minerals (Li and
Be)
 Kimberlites
• Rare, ultramafic rock that can contain diamonds and other
minerals formed only under very high pressures
 Compare
and Contrast magma and lava.
 What
two types of igneous rocks are formed as
each cools?
 Describe
the three major mineral groups of
igneous rocks. What minerals are found in
each?