Glossary :: Igneous Petrology

Aa

A solidified lava flow with a blocky surface, formed from a viscous lava. The name is of Hawaiian origin.

Agpaitic

Alkaline rocks having the alkalis over Al ratio in excess of 1, and containing a suite of complex alkali titano-, niobo- and zirconosilicates (e.g., eudialyte).

Alkalis

When applied to igneous rocks, this word implies the presence of Sodium (Na) and/or Potassium (K).

Apatite

Phosphate mineral, which can be in three forms depending on its chemistry. Forms are Fluorapatite (fluorine-rich), Chlorapatite (chlorine-rich and Hydroxylapatite (rich in hyrdroxides). It is also what most teeth of mammals are made of!...More

Cumulate Rock

Formed from the settling of crystals within a magma chamber, may be layered if dense minerals are allowed to sink preferentially.

Fissure Eruption

An eruption occurring through long, open crack in the ground. They commonly form flood basalts which are repeated flows on low viscosity lava and can cover large areas.

Gardar Province

Geological area of south-west Greenland famous for its alkali intrusions especially Ilimaussaq which has over 200 minerals associated.

Incompatible elements

Incompatible relative to mantle minerals; those elements with large ionic radii such as Nb, Zr, U, Th, K, Na, Li, Be, REE, that preferentially go into the melt rather than remain in residual minerals.

Intrusion Magma

That has crystallised beneath the surface.

Lahar

A mudflow associated with volcanic eruptions when volcanic ash mixes with water.

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