GEO 311 Study Guide - Midterm Guide: Mesoscopic Physics, Deformation Mechanism, Cataclastic Rock
Document Summary
Increase in the spread of grain sizes (some are big and some are small: cataclastic deformed rocks end up with an increase in volume (decrease in grain size) Common in most sedimentary and metamorphic rocks: diffusion along wet grain boundaries and reprecipitation at low stress points, not doing anything with the crystal lattice! Just dissolving the original grains and then reprecipitate the grains: what to look for: Dark stripes in the rock (opaque) (1) formed from material that does not resolve away (residue) (2) micas do not dissolve away so easily so micas tend to get concentrated and then occur in dark stripes in the rock. Stylolites occur (1) these are highly indented surfaces where material has been dissolved in an irregular way (stylolite shown in the picture to the right) Sharp contacts on the edges of the dark stripes and truncated mineral grains. Fibers or beards (1) these are the precipitates.
