Geology Reference
In-Depth Information
examples as large single pulses of magma, for example Skaarguard intrusion,
Greenland. Although a range from mafic/ultra mafic through to granitic com-
positions often characterise these intrusions, it is predominantly the mafic/ultra
mafic rocks which host some of the most stunning and enigmatic igneous struc-
tures, that of layered igneous rocks. Probably the most useful connection that
has been made in igneous geology is the linking up of some of the major igneous
centres with the volcanic systems that they feed. This realisation that we are able
to have a window into the processes going in the depths of a volcanoes magma
chamber, has provided great insights into how magma is processed through the
crust to the surface.
1.4 Summary
The layout and organisation of this field guide emphasises the occurrence of
igneous rock associations within characteristic crustal regions, as introduced
in Section 1.3. Chapters 2 and 3, provide information on the key field skills
and igneous outcrop-texture description as well as basic classification tables for
igneous rocks. Volcanic rocks are looked at in Chapter 4 (lavas) and Chapter 5
(pyroclastics), and the shallow minor intrusions in Chapter 6. Larger plutonic
systems are presented in Chapter 7 (granitic complexes) and Chapter 8 (mafic
complexes), and the roles of magma mixing/mingling in Chapter 9. Finally we
take a look at the mineralisation and engineering properties of igneous rocks
in Chapter 10.
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