Migmatites represent transitions in the rock cycle from medium and high-grade metamorphic rocks to igneous rocks. Furthermore, migmatites are the result of partial melting that occurred in extreme conditions deep inside the earth’s crust. They can be intricately folded (e.g., having zigzag patterns) because they are the result of thermal softening. Migmatites can also be swirled or twisted in some way because some minerals had started to melt.
Migmatites are commonly of Precambrian age.
Figure 1. Migmatite rock (10 inches from lower left corner to upper right corner): showing rotation of its main components and flow banding.
Figure 2. Migmatite rock (9 inches from lower left corner to upper right corner): showing flow banding of some its component parts.
Figure 3. Migmatite rock (6.5 inches from left to right).
Figure 4. Sketch of ptygmatic (“intestine-like) folding (in pink color) found in a migmatite. Sketch modified from: https://www.britannica.com/science. Scale: unknown.
No comments:
Post a Comment