Introduction

The purpose of this virtual experiment is to show how the temperature changes in rocks adjacent to an intrusion as the intrusion cools. The data used in making this virtual experiment are based on a real experiment which has been done many times. The data represent an average of those results. All the rocks around an intrusion are referred to collectively as the country rock. The belt of metamorphosed country rock around an intrusion is called the metamorphic aureole. Where exposed the junction between the intrusion and the metamorphosed rocks is sharp and easy to pin point. The junction between the metamorphic rocks and the unmetamorphosed country rocks will be gradational. Usually there is no exact place where everyone would agree the change takes place. Can you explain why this contact is gradational? Look at the map of the Loch Doon area in Scotland. You can see the granite intrusion coloured red and the metamorphic aureole in orange. The width of the metamorphic aureole varies. Can you explain this? The little outcrop of granite in the south east is connected to the main outcrop undrground. It may help you to draw a sketch section along the line A-B. Reproduced with the permission of the Brtish Geological Survey © NERC