Igneous Petrology Course

Lecturer: Matt Genge, Meteorite Researcher, Previously worked at The Natural History Museum.

Lectures: Part I (4 weeks) Igneous Processes at the Atomic Scale.Part II (4 weeks) Igneous Processes at Large Scales.

Practicals:How to recognise and describe igneous rocks in hand specimen and thin section (see list on handout sheet).

Coursework (20%):Five coursework pieces focused on each major group of igneous rocks.1.5 hour Exam (80%):Straight after christmas! Special revision session last practical.

Hot Under the Collar (part I)

Melting and the Phases of Matter

Pacaya Volcano - Guatemala

Igneous Rocks: formed by cooling of a magma.

The Four Phases of Matter

Liquid

Solid Gas

Plasma

Structural Differences

Configurational entropy (disorder)

Kinetic Differences

Vibrational entropy (disorder)

Entropy

The entropy of a mixture is higher than a pure material

Entropy

Entropy increases with temperature due to the magnitude of atomic vibrations

Entropy

Entropy is “wasted” or unavailable energy

Total Thermodynamic Energy in Matter

+Potential Energy Kinetic Energy

Total Energy (Enthalphy H) = PE + KE

Gibbs Free Energy

G – Gibbs Free Energy (energy available for chemical work)

H – Enthalpy (total energy)

S – Entropy (energy locked up in disorder – wasted energy)

G = H – T.S

First Law of Thermodynamics

Extrinsic and Intrinsic Properties

Extrinsic properties depend on the mass of the system.

Extrinsic and Intrinsic Properties

Intrinsic

Taste

Colour

Specific Gravity

Temperature

Extrinsic

Volume

Amount of Alcohol

Attractiveness

Extrinsic and Intrinsic Properties

Intrinsic

Composition

Temperature

Pressure

Extrinsic

Volume/mass

Enthalpy

Entropy

Gibbs Free Energy

Temperature

2

2

1

3

2mv

kT

• Temperature is the effect of the motions of atoms within a material (the vibrations, translations and rotations of molecules).

• Temperature is proportional to the average kinetic energy of the atoms or molecules within a material.

Pressure

V

NmvP

3

2

Pressure is the force applied by rebounding atoms and is related to the change in momentum.

Transitions between the Phases of Matter

Transitions and Gibbs Free Energy

•The phase with the lowest Gibbs Free Energy at equilibrium is the stable phase.

•Two coexisting phases have the same Gibbs Free Energy

Melting

Sudden increase in disorder on melting. A discontinuous increase in entropy S.

First & Second Order Phase Transitions

G = H – T.S• H is the latent heat of fusion

• Temperature stays constant until all the material has melted.