Chapter 3 Igneous Rocks
Magma evolution
A change in the composition of a Magma body.
Granite
A felsic, coarse grained intrusive igneous rock
Batholith
A large discordant pluton
Stock
A small discordant pluton with an an equal areal
Mafic Magma crystallize into ______ or ______ if minerals are not removed.
Basalt or Gabbro
Intermediate composition
Between felsic and mafic.
Diapir
Bodies of rock or magma that ascend within Earths interior because they are less dense.
Contact
Boundary surface between two different rock types or ages of rocks.
How is Magma created?
By melting of rock above a subduction zone.
Diorite
Coarse-grained igneous rock
Describe the discontinuous branch of the Bowens series.
Ferro magnesia minerals crystallize in sequence with decreasing temperature.
Andesite
Fine grained igneous rock
Rhyolite
Fine grained, felsic igneous rock made of feldspar and quartz.
Xenolith
Fragment of rock distinct from the igneous rock in which it is enclosed.
The most common igneous rock of the continents is _______.
Granite
Example of an intraplate volcano.
Hawaii
Dunite
Igneous rock
Less dense Magma rises and cools to form _________.
Igneous rock
Plutonic rock
Igneous rock formed at great depth.
Chill zone
In an intrusion, the finer grained rock adjacent to a contact with country rock.
What does separation of early formed ferro magnesia minerals from a Magma body do?
Increases the silica content of the remaining magma.
What type of rocks are typically coarse grained?
Intrusive igneous rocks
Intrusive igneous rocks vs Extrusion igneous rocks
Intrusive igneous rocks form when Magma solidifies underground. Extrusion igneous rocks form when Magma solidifies at the Earth's surface (lava).
What happens to igneous rock exposed at the surface?
It gets weathered into sediment.
Gabbro
Mafic coarse grained igneous rock
Basalt is a ________ rock.
Mafic igenous rock
Mantle plume
Narrow column of hot mantle rock that rises and spreads radially outward.
Rock
Naturally formed material composed of one or more minerals.
Aphanitic
Need microscope to see crystals
Discordant? Give 1 example
Not parallel to any layering Dikes
Rock cycle shows how __________.
One type of rocky material gets transformed into another.
Concordant? Give 2 examples
Parallel layering Sills and laccolith
Describe the Continous branch of Bowens series.
Plagicoclase feldspar chemical composition evolves from Calcium rich to Sodium rich with decreasing temperature.
What is the only mineral in the continuous branch of Bowen's?
Plagioclase
Geothermal gradient
Rate at which temperature increases with depth
The difference in texture between intrusive and extrusive rocks is __________.
Rate of cooling and crystallization
Minerals melt in ______ order of that which they crystallize from a Magma.
Reverse
Intraplate volcanism
Rising mantle plumes can produce localized Hotspots and volcanoes when they produce magmas that rise through oceanic or continental crust
Ultramafic rock
Rock composed entirely of ferromagnesian minerals
Describe the rock cycle.
Rock moves from deep to shallow, and from high to low temperature and pressure in response to tectonic forces
Mixtures of minerals such as quartz and feldspar can result in _______.
The melting of both at temperatures lower than either would melt on their own.
Crystal settling
The process whereby the mineral that crystallize at high temperature in a cooling magma move downward in the magma chamber because they are denser.
Texture
The size, shape and arrangement of grains in a rock.
What type of rocks are typically fine grained?
Extrusion igneous rocks
______ igneous rocks are commonly formed adjacent to convergent boundaries.
Felsic
Describe the 4 ways magma evolution can occur.
(1)Differentiation-changing of magma composition by the removal of denser early formed ferro magnesia by crystal settling. (2) Partial melting - produces magmas less magic because lower melting point minerals are more Felsic in composition. (3) Assimilation-When hot magma melts and incorporates the surrounding country rock. (4) Magma mixing - mixing of two or more magmas to produce one of overall intermediate composition.
Pluton
An igneous body that crystallized deep underground.
____ is not an intrusive rock.
Andesite
Phenocryst
Any of the large crystals in porphyritic igneous rock.
Country rock
Any rock that was older than and intruded by an igneous body.
Change in a magma's composition due to melting of surrounding country rock is called _______.
Assimilation
Hot rising magma causes partial melting of the _______.
Continental crust
Intermediate rocks are found at _______ boundaries.
Convergent
Granitic magmas are associated with _____ boundaries and _______.
Convergent and Decompression melting
Mafic magma is generated at divergent boundaries because of?
Decompression melting
Intermediate Magma crystallize into _____ or ______.
Diorite or Andesite
As one mineral becomes unstable in the remaining magma, another begins to form. This would be the _____ branch of Bowens series.
Discontinuous
Mafic igneous rocks are found at _______ boundaries.
Divergent
Why do mafic magmas tend to reach the surface much more often than silicic (felsic) magmas?
Mafic magmas are less viscous. This is due to the Silica content. Felsic magmas have a greater silica content increasing the viscosity.
Metamorphic rock may heat up and melt at depth to form ______.
Magma
Large variety of igneous rocks is produced by large variety of ______.
Magma compositions
Igneous rocks forms when ________.
Magma cools and solidifies
Highly reactive water vapor can reduce the _______ of rocks.
Melting point
If Pressure increases, ____ increases.
Melting point
Bowens reaction series
Minerals crystallize over a large temperature range.
Sediments transported to low lying areas are buried and hardened into ________.
Sedimentary rock
How is metamorphic rock formed?
Sedimentary rock is heated and squeezed at depth
Volcanic neck
Shallow intrusion formed when Magma solidifies in throat of volcano.
Dike
Shallow, tabular intrusive structure that cuts across any layering in country rock.
Sill
Shallow, tabular intrusive structure that parallels layering in country rock.
Mafic composition
Silica DEFICIENT igneous rock
Felsic rock
Silica rich igneous rock
Igneous activity occurs primarily at ______.
Tectonic plate boundaries
Phaneritic
Texture in which the crystals of an igneous rock are easy to see without a microscope
Periodotite
Ultramafic rock composed of pyroxene and olivine.
_____ becomes increasingly reactive at higher temperature.
Water
When does decompression melting occur?
When hot mantle rock moves upward and pressure is reduced enough to drop the melting point to the temperature of the rising rock body.
Why is a higher temperature requried to form magma at the oceanic ridges than in the continental?
mafic magma (the magma that makes up oceanic crust) has a higher melting point than felsic magma (magma that makes up continental crust)
Stocks differ from batholiths in _______.
shape
_______ is not a source of heat for melting rocks.
water under pressure