Geology Reference
In-Depth Information
2. Measure any S-C fabrics and other kinematic indicators and record shear
sense.
3. Look out for layering and 'exotic' magmatic structures such as pipes, ladder
dykes and accumulations of megacrysts (log jams) and record their mineral-
ogy, orientation and spatial association.
4. Look carefully for internal contacts. Record dip and strike of contacts, note
changes in lithology. Is the pluton sheeted internally?
5. Study the nature and distribution of enclaves.
6. Decide whether a pluton is zoned on a regional scale.
It is important to remember that as with all rocks, the fabric you record is
the last increment of finite strain and that a crystal plastic strain fabric may be
superimposed on an originally magmatic one. This distinction may be critical
when mapping in detail internal contacts inside plutons.
In addition:
1. Record any distinctive granitoid textures - graphic granite, orbicular granite
and rapakivi granite, and jointing structures and mineralisation freatures (see
Chapter 10).
2. The type of contact metamorphism in the country rocks surrounding high-
level granites may be distinguished with the aid of Table 7.2.
