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