User:Babakathy/igneous petrology

Igneous petrology' is the scientific study of igneous rocks. It consists of the observation of the chemistry and mineralogy of igneous rocks, and the connections between these observations and the thermodynamics and kinetics that can explain how the rock formed and crystallized from a melt. It is a branch of petrology, which is a sub-field of geology.

Field studies of igneous rocks

Many aspects of the mineralogy, composition, and formation of igneous rocks can be observed in the field. In the field, a geologist can use a hand lens, acid bottle, and other tools [flesh out] to identify the individual minerals within an igneous rock. These minerals give the geologist an idea as to its composition. The size of the minerals shows how much time the crystals had to nucleate and grow. Large crystals indicate a longer amount of time for growth; this is characteristic of intrusive rocks, igneous rocks that cooled slowly below the surface. Crystals in extrusive rocks, or lavas, are often too small to see, even with the aid of a petrographic microscope. [Something about phenocrysts and/or xenoliths and eruption]

[Include a field classification scheme; perhaps QAPF diagram or a simpler introductory textbook one; or the one for volcanic rocks (TAS diagram, on Wikimedia commons already), too?]

Petrography

A petrographic microscope.

Igneous geochemistry

(check what is in geochemistry)

• major elements
• minor elements
• trace elements
• isotopes
• fluid inclusions

Theoretical petrology

Maybe start out simple with something like Bowen's reaction series - or maybe put this closer to intro.

(phase diagrams & equations)

Phase Diagrams

• Most important probably olivine, some others, in T-X space
• Ternary diagrams of feldspars
• a pyroxene quadrilateral (trapezoid) diagram might also be good

Equations

• Clausius-Clapeyron with respect to # of phases that can be present
• Basic thermodynamics and kinetics with examples
• How to get pressure and temperature from knowing which phases are present

Experimental petrology

high pressure, high temperature laboratories doping of melts