This interactive courseware module approaches the use and interpretation
of phase diagrams using various igneous systems. It is designed
for first or second year undergraduates.
The module makes full use of multi-media techniques to explain phase diagrams, for example user interactions, animations and simulations. The relationship between phases in different spaces (T-X, P-X, X-X, texture) is demonstrated simultaneously on screen and this helps the user to understand a subject that is traditionally found difficult. In addition, the ability to rotate and view phase relations in three dimensional space has obvious advantages over standard two dimensional textbook diagrams.
The module occupies about 4Mb and consists of six separate units, each containing approximately 45 minutes of material. The user is encouraged to undertake the units in the order presented, working from unary systems through to the three component ternary systems. The module is constructed so that the examples used to demonstrate binary systems are also components of the ternary systems.
This unit introduces the user to phase diagrams and the Phase Rule with an explanation of systems, equilibrium, components, phases and variance (divariant, univariant and invariant). The significance of the slopes of phase boundaries is also discussed. The unary H2O system is used to illustrate these concepts.
The diopside-anorthite system This unit introduces the user to the terms liquidus, solidus and eutectic and provides a brief review of the Phase Rule. Equilibrium crystallisation and melting pathways for different compositions are discussed along with potential variation in textures. The Lever Rule is explained and its use in determining the amounts of phases present is demonstrated.
The forsterite-silica system This unit introduces intermediate compounds, the peritectic, congruent and incongruent melting and the effect of pressure on phase equilibria.
The anorthite-albite system The An-Ab system is used to introduce the terms solvus, exsolution and sub-solidus. The unit also explains partial and complete solid solution, equilibrium/fractional crystallisation and melting, and gives an example of the effect of water on phase equilibria.
The diopside-albite-anorthite system This unit shows how ternary systems can be built up from binary systems, and demonstrates different ways of representing 3D information in 2D space. The Di-Ab-An system is used to introduce primary fields, liquidus surfaces, thermal contours and the cotectic. Representative equilibrium crystallisation pathways are demonstrated simultaneously on 3D block and triangular composition diagrams.
The forsterite-anorthite-silica system In the final unit the Fo-An-Si system is used to revise concepts and terms introduced in unit 5, as well as introduce the ternary cotectic and pseudo-ternary systems. The unit also demonstrates the effect of intermediate compounds on equilibrium crystallisation pathways in ternary space.
The different parts of the module are accessed via a main menu
and navigation around the module is by means of buttons along
the base of the screen.
| Arc Magmatism | Aspects of Earth Resources | Basic Geochemistry | Basic Petrography | Basic Skills for Earth Sciences | Crystallography | Dynamic Stratigraphy: Controls and Products | Exploring the Shallow Subsurface using Geophysics | Fossils as Palaeoenvironmental Indicators | Ocean Crust and Ophiolites | Optical Mineralogy | Petrogenesis of Granitic Rocks | Radiogenic Isotopes in Geological Sciences | Rock Deformation and Geological Structures | Systematic Palaeontology: the Phylum Mollusca | Using Stereonets in Geology | Visualising Geology in 3D |
