Igneous Petrology Concepts

Flashcards derived from notes on igneous petrology, covering key concepts, classifications, and terminology associated with igneous rocks.

Igneous Petrology

The study of melts (magmas) and the rocks that crystallize from these melts.

Classification of Igneous Rocks

Igneous rocks can be classified based on mineral content, texture, and chemistry.

Aphanitic

Volcanic rocks with small grain size, not visible to the naked eye.

Phaneritic

Plutonic rocks with grains that can be seen without a microscope.

IUGS (International Union of Geological Sciences)

Body that developed a widely accepted classification scheme for igneous rocks.

Phenocrysts

Larger crystals within a finer-grained matrix in volcanic rocks.

Bowen's Reaction Series

A sequence of minerals indicating the order in which they crystallize from cooling magma.

Mafic Rocks

Igneous rocks that are rich in magnesium and iron.

Felsic Rocks

Igneous rocks that are rich in silica and light-colored minerals.

QAPF Diagram

A classification diagram for plutonic rocks based on the relative proportions of Quartz (Q), Alkali Feldspar (A), Plagioclase (P), and Feldspathoids (F).

Accessory Minerals

Minerals present in small amounts (less than 5%) that do not affect the naming of the rock.

Trace Elements

Elements present in very small amounts (less than 0.1 wt. %) that can substitute for more abundant elements.

Chemical Petrology

The study of the chemical composition and characteristics of rocks, especially igneous.

TAS Diagram

A graphical representation used to classify igneous rocks based on total alkalis versus silica.

Fractional Crystallization

A process by which different minerals crystallize from magma at different temperatures, affecting the composition of the remaining melt.

Assimilation

The process whereby surrounding rock influences the composition of magma as it rises. Country Rock and Source Rock Interact together

Volcanic Rocks

Igneous rocks formed from lava that cools and solidifies on the surface.

Plutonic Rocks

Igneous rocks formed from magma that cools and solidifies below the Earth’s surface.