Petrogenesis of Granitic Rocks

by

Dave Bryon and Alan Boyle, University of Liverpool

This courseware module is intended for second-year undergraduates, and covers various aspects of igneous petrogenesis using granitic rocks as an example.

The module has two main objectives.

1. To supplement existing teaching and provide specialist knowledge of a major area of igneous petrology.

2. To show how the different component areas of igneous petrology taught during first- and second-year courses interlink, and can be assimilated to produce an overall model for granite petrogenesis in various tectonic settings.

Description of the module

The module occupies approximately 2.2 Mb, and consists of five main units selectable from this menu

Users are free to work through as many or as few units as they want, and in any order they want.

The units are as follows

Unit 1. Introduction

This unit deals with what granites are and reasons for studying them, how and where they form, how granites move and what happens when they cool.

Information is given in a variety of ways, including animations

Unit 2.Classification

This unit deals with classification according to modal abundance, chemical trend, source, and tectonic setting.

User interactions are required throughout the modules

Unit 3.Generation

This unit covers the factors that cause melting, the source rocks and how they melt, and how the melt segregates from the source region.

This page forms part of the magma generation unit.

Unit 4.Transport

The ascent and emplacement of granitic magmas are deal with in this unit. The topics covered under ascent include the factors affecting the ascent of granitic magmas, magma ascent along faults and as diapirs, and the heat loss from ascending magmas. The emplacement topics include forceful and passive emplacement, evidence in and around solidified bodies for forceful emplacement, passive emplacement by stoping, and emplacement along strike-slip fault zones.

This question and answer section is from the 'Transport' unit.

Animated block diagrams are used to reinforce concepts

Unit 5.Crystallisation

This unit deals with magma chamber processes and granitic textures and crystallisation histories. Open and closed magma systems, the cooling history of magma chambers, crystal mush zones, and compositional variation and fractional crystallisation are covered under magma chamber processes. The essential mineralogy, the textural relationship between crystals, phase diagrams and textural evolution during crystallisation are covered under granitic textures and crystallisation histories.

Graphs and phase diagrams are used throughout.

Running the software

Navigation around the module is by means of buttons along the base of the screen. Users can work through the module step-by-step and are then required to complete everything on each page before being allowed to proceed. Alternatively, users can opt to be allowed to proceed without having to complete all the material on each page.

A Glossary is accessed by clicking either on hot words in the body of pages or on the Glossary button along the base.

A short list of references to publications about granite petrogenesis can be accessed by clicking on the Refs. button.

Summary information on the user's performance at answering questions is provided on completion of each unit.