Here are two maps of the geology in Iceland. The first map shows the fault zones with the active volcanoes in Iceland. Also in this map the age of the rock is shown. The second map shows the rock type, if it is acid, basic and so on.
A map of Iceland with fault zones and active volcanoes. This map is not up to date with newest research and stuff like that. Click on the picture to get a full size.
This map shows rock type in Iceland. Explanation is to the right. Click on the picture to get a full size.
Both pictures are from this web site here.