E&E 151 S Introductory Geology: Chapters 3.4 - 3.7 (Igneous Pt.2) Definitive Study

Bowen's Reaction Series

The specific sequence in which minerals crystallize from a cooling magma based on their stability temperatures.

Discontinuous Branch

The branch of Bowen's reaction series where ferromagnesian minerals crystallize in discrete steps as crystalline structures change with cooling.

Continuous Branch

The branch of Bowen's reaction series where plagioclase feldspar continuously evolves from a calcium-rich to a sodium-rich composition.

Differentiation

The process by which different mineral ingredients separate from an originally homogeneous magma mixture.

Fractional Crystallization

A differentiation process where early-formed crystals are removed from contact with the melt so they no longer react with it.

Crystal Settling

The downward movement of dense, early-formed minerals like olivine and pyroxene to the bottom of a magma chamber.

Assimilation

The process in which a hot magma melts and incorporates surrounding country rock into the melt.

Stoping

The process where ascending magma breaks off blocks of surrounding country rock.

Xenolith

An un-melted block of country rock preserved as a foreign inclusion within an igneous rock body.

Inclusion

A piece of older, foreign rock or mineral enclosed within a younger igneous rock body.

Magma Mixing

The process where two distinct magmas meet and merge into a single homogeneous magma of intermediate composition.

Magma Mingling

The process where two magmas of different compositions encounter one another but retain their individual characteristics, forming inhomogeneous blobs.

Solid Solution

A mineral series in which specific atoms like sodium and calcium substitute for each other in the crystal structure as temperature drops.

Intrusion

A body of intrusive igneous rock that solidified underground beneath Earth's surface.

Pluton

A specific body of coarse-grained igneous rock that crystallized and solidified at considerable depth within the crust.

Discordant

An intrusive body that cuts across the pre-existing layering or planes within the surrounding country rock.

Concordant

An intrusive body that runs parallel to the pre-existing layering or planes within the surrounding country rock.

Aphanitic

A fine-grained igneous rock texture resulting from rapid cooling at or near Earth's surface.

Phaneritic

A coarse-grained igneous rock texture resulting from slow cooling deep underground.

Viscosity

A fluid's resistance to flow; silica-rich magmas have high viscosity, whereas silica-poor magmas have low viscosity.

Felsic

Silica-rich magma or igneous rock containing high amounts of potassium and aluminum, typically forming granite or rhyolite.

Silicic

An alternative term for felsic igneous rocks and magmas that are enriched in silica (SiO₂).

Mafic

Silica-poor, iron- and magnesium-rich magma or igneous rock, typically forming basalt or gabbro.

Intermediate

Igneous rock composition between mafic and felsic, typically represented by diorite or andesite.

Ultramafic

Igneous rock composed almost entirely of ferromagnesian minerals with very low silica content, characteristic of the mantle.

Geothermal Gradient

The rate at which temperature increases with increasing depth inside the Earth.

Decompression Melting

Melting that occurs when hot mantle rock ascends to shallower depths and experiences a drop in pressure without gaining extra heat.

Flux Melting

Partial melting of mantle rock triggered by the addition of water released from a subducting oceanic plate.

Partial Melting

The incomplete melting of a parent rock, producing a magma richer in silica than the original rock.

Magmatic Underplating

The process where hot mafic magma pools at the base of the continental crust, supplying heat to partially melt the overlying crust into granitic magma.

Mantle Plume

A narrow upwelling of hot, solid material rising from deep within the mantle.

Intraplate Igneous Activity

Igneous activity occurring within a tectonic plate at a long distance from any plate boundary.

Hot Spot

A volcanic region on Earth's surface fueled by underlying heat from a mantle plume, independent of plate boundaries.

Plate Boundary Rock Associations

The predictable global relationships between specific igneous rock compositions and their tectonic environments.

Divergent Boundaries

Spreading plate margins where partial melting of the asthenosphere generates mafic basalt and gabbro.

Convergent Boundaries

Subduction zones where flux melting and differentiation produce intermediate and felsic igneous rocks like andesite, diorite, granite, and rhyolite.