Geology Reference
In-Depth Information
(a)
(b)
(c)
Figure 7.12
(a) Shear zone in granite (b) narrow band of dark mylonite (dark
colour due to fine grain size) (c) irregular bands of cataclasite (brittle deforma-
tion) cutting earlier S-C fabric, Cordillera Blanca, Peru.
in the field, especially if the sheets are wide and their margins are diffuse. The
main Donegal Granite in Ireland is a good example of this, where close inspec-
tion has shown the pluton was constructed via accumulation of a large number
of smaller sheets (Figure 7.14). The nature of igneous contacts, either internally
or with country rocks, needs to be recorded accurately, especially where such
relationships are cross-cutting and hence age related (Figure 7.15).
