1. IGNEOUS ROCK
Felsic rich igneous lunar rock collected from the lunar highlands of the moon by Apollo 16 astronauts.

2. Rock Classification ROCKS SEDIMENTARY
-thin veener in Oceanic and Continental Crusts
-secondary rocks
IGNEOUS
-most abundant
-primary rocks
-source is magma or lava
METAMORPHIC
-proportion is similar to that of Igneous rocks
-change of forms of Ig. And Sed. Due to Temperature, Pressure and Chemical Fluids

3. Rock
Cycle

4. Origin: Igneous Rock
“Fire-formed rocks“ Crystallize from molten material:
IGNEOUS ROCKS: The rocks formed through volcanic action OR
The rocks which are derived from a molten mass “magma or lava”
Magma – molten rock below the Earth's surface
Lava – molten rock that erupts onto the Earth's surface through a volcano or crack (fissure)

5. Origin: Igneous Rock SOURCE OF IGNEOUS ROCKS:
VOLCANO: A gap in the Earth’s Crust where molten rocks and other material escape onto the Earth’s surface
SOURCE OF IGNEOUS ROCKS:
Magma: Molten mass comprising most abundant elements in earth – Si, Al, Fe, Ca, Mg, K, H & O. Where the SiO2 is most abundant amongst all.
Temperature of Magma to C

6. Formation of Magma How are rocks melted? Where do rocks melt?
1. Heating
2. Depressurization
3. Increase water content
4. Increased silica content
Where do rocks melt?
Subduction zones
(Felsic and Intermediate)
Mantle Plumes (“Hot Spots”)
not only at
Divergent
Boundaries
Mafic
Hot and
Low Pressure
Hot and
High Pressure

7. Cooling Rates of Magma
Cooling rates influence the texture if the igneous rock:
Quick cooling = fine grains
Slow cooling = coarse grains

8. Magma
Different magmas have different viscosities. Viscosity is the property of a substance to internally resist flow.
Example: Pine Sap or Molasses (High Viscosity) vs. Water (Low Viscosity)
The HIGHER the viscosity, the more resistance to flow!!

9. Igneous rocks are classified on their texture and their composition.
Igneous textures:
Glassy
Aphanitic
Phaneritic
Porphyritic
Vesicular
Pyroclastic

10. Igneous rocks are classified on their texture and their composition.
Igneous textures:
Glassy - instantaneous cooling
Obsidian = volcanic glass

11. Igneous rocks are classified on their texture and their composition.
Aphanitic - fine grain size
(< 1 mm); result of quick cooling
Basalt
Rhyolite
Andesite

12. Igneous rocks are classified on their texture and their composition.
Phaneritic - coarse grain size; visible grains
(1-10 mm); result of slow cooling
Granite
Diorite
Gabbro

13. Igneous rocks are classified on their texture and their composition.
Porphyritic- Mixture of grain sizes caused by mixed cooling history; slow cooling first, followed by a period of somewhat faster cooling.

14. Igneous rocks are classified on their texture and their composition.
Vesicular - contains tiny holes called vesicles which formed due to gas bubbles in the lava or magma. Very porous. May resemble a sponge. Commonly low density; may float on water.

15. Igneous rocks are classified on their texture and their composition.
Pyroclastic or Fragmental - pieces of rock and ash come out of a volcano and get welded together by heat.
Tuff - made of volcanic ash
Volcanic breccia - contains fragments of fine-grained igneous rocks that are larger than ash.

16. BROAD CLASSIFICATION OF IGNEOUS ROCKS
Intermediate rocks
(Hypabyssal rocks)
Plutonic rocks
(Intrusive rocks)
-dykes, sills, batholiths, laccoliths etc.
Volcanic rocks
(Extrusive rocks)
-Lava or Magma flows
-Pyroclastic flows

17. Igneous Rocks Are Subdivided Into Two Classes
Volcanic (Extrusive)
Volcanic igneous rocks form at the earth's surface as lava cools.
Plutonic (Intrusive)
Plutonic igneous rocks form deep underground where magma cools slowly.

18. Igneous Rock Classification
Mineral Percentage
Intrusive (Plutonic)
Extrusive (Volcanic)
Continental Crust Oceanic Mantle
Crust

19. Intrusive Igneous Rock
E.g., Felsic -Granite (Phaneritic):
Quartz
Na Plagioclase
Biotite
Crystallized (Solidified)
Felsic Magma
Poor in: Fe, Mg, Ca, (<20%)
Rich in: Silica (>70%)

20. Extrusive vs. Intrusive (Mafic Rocks)
Mafic Magmas
Hot (>1000oC)
Non-Viscous (runny, flows easily)
“Dry” (no H2O or C02)
Mafic Rocks
Usually Extrusive, Fine-grained,
Mafic (Basalt) rock forms oceanic crust, Shield Volcanoes and Basalt Floods
If Intrusive, course-grained mafic rocks are formed Gabbro.
If intrusive, Dikes and Sills more common

21. Igneous Rock Classification
Felsic Intermediate Mafic
Granite Diorite Gabbro
Rhyolite Andesite Basalt
(Porphyritic)
Intrusive
Extrusive

22. Bowen’s Reaction Series
Minerals form as molten rock crystallizes. A generalized order of crystallization of minerals is shown in the Bowen's Reaction Series. As the magma cools, first olivine, then pyroxene, then amphobole, etc. will be crystallized (assuming the proper elements are available).
Bowen's Reaction Series has two branches.
They are:
Discontinuous reaction series, from olivine to biotite,.
Continuous reaction series, from Ca plagioclase to Na plagioclase.

23.  KINDS OF IGNEOUS ROCK
Mafic
Intermid
Felsic

24. Bowen’s Reaction Series
The discontinuous reaction series involves the dark-colored ferromagnesian minerals:
olivine
pyroxene
amphibole
biotite.
The continuous reaction series involves the plagioclase feldspars. Plagioclase feldspars are an example of a "solid solution series", exhibiting gradations in chemical and physical properties. Chemically, this series consists of two "end members":
Na plagioclase (NaAlSi3O8), the sodium "end member", and
Ca plagioclase (CaAlSi2O8), the calcium "end member".

25. BOWEN'S REACTION SERIES
Shows a generalized crystallization order of minerals as a magma cools.
GENERALITIES down the reaction series (from top to bottom):
Easier to melt minerals
The more complex the silicate mineral
Higher the viscosity of the magma
More resistant the mineral is to chemical weathering
Lower the rock's final density

26. Fluidity or Viscosity of magma depends on content (%) of Silica
FLUIDITY OF MAGMA
Fluidity or Viscosity of magma depends on content (%) of Silica
Silica poor (mafic)
-Known as Basic magma
-Less viscous, moves faster and occupies larger area (release gas easily)
Silica Rich (felsic)
known as Acidic magma
More viscous, so do not spreads and piles up at one place (trap gas easily)
However, the viscosity of magma is considerably influenced by
temperature too. When temperature is less- magma is more viscous (thicker) and when temperature is high - less viscous (thinner).

27. Volcanic Eruption of Magma
When magmas reach the surface of the Earth they erupt from a vent.  They may erupt explosively or non-explosively.  
Non-explosive eruptions are favored by low gas content and low viscosity magmas (basaltic to andesitic magmas).
Usually begin with fire fountains due to release of dissolved gases
Produce lava flows on surface
Produce Pillow lavas if erupted beneath water

28. Eruption of Magma
Explosive eruptions are favored by high gas content and high viscosity (andesitic to rhyolitic magmas).
Expansion of gas bubbles is resisted by high viscosity of magma - results in building of pressure
High pressure in gas bubbles causes the bubbles to burst when reaching the low pressure at the Earth's surface.
Bursting of bubbles fragments the magma into pyroclasts and tephra (ash).
Cloud of gas and tephra rises above volcano to produce an eruption column that can rise up to 45 km into the atmosphere.

29. Eruption of Magma
Tephra that falls from the eruption column produces a tephra fall deposit.

30. Eruption of Magma
If eruption column collapses a pyroclastic flow  may occur, wherein gas and tephra rush down the flanks of the volcano at high speed.  This is the most dangerous type of volcanic eruption.  The deposits that are produced are called ignimbrites.

31. Eruption of Magma
Lateral blasts and debris avalanches occur when gas is released suddenly by a large landslide or debris avalanche taking out part of the volcano

32. Plutons Plutons = Igneous rocks cooled at depth.
Name comes from Greek god of the underworld - Pluto.

33. Pluton features
Dikes are small (<20 m wide) shallow intrusions that show a discordant relationship to the rocks in which they intrude.
Discordant means that they cut across preexisting structures. They may occur as isolated bodies or may occur as swarms of dikes emanating from a large intrusive body at depth.

34. Pluton features
Sills are also small (<50 m thick) shallow intrusions that show a concordant relationship with the rocks that they intrude.  Sills usually are fed by dikes, but these may not be exposed in the field.

35. Pluton features
Laccoliths are somewhat large intrusions that result in uplift and folding of the preexisting rocks above the intrusion.  They are also concordant types of intrusions.

36. Pluton features
Batholiths are very large intrusive bodies, usually so large that there bottoms are rarely exposed.  Sometimes they are composed of several smaller intrusions.
Stocks are smaller bodies that are likely fed from deeper level batholiths.  Stocks may have been feeders for volcanic eruptions, but because large amounts of erosion are required to expose a stock or batholith, the associated volcanic rocks are rarely exposed.

37. Methods of Igneous Intrusion
Methods of intrusion
Melting - crystallization
Stoping - xenoliths
Injection

38. Igneous Intrusion