EAS100 Lecture Notes - Lecture 12: Migmatite, Differential Stress, Pyroxene

• School: University of Alberta
• Department: Earth and Atmospheric Sciences
• Course: EAS100
• Professor: Korhan

Document Summary

Erosion: removal of surface material from one place to another. Mechanical weathering : physical breakdown of older rocks into smaller pieces. Chemical weathering : changes that modify the composition of the original material. Ex. carbon dioxide + water = carbonic acid makes water acidic. Ex. hydrogen ion enters feldspar, potassium ion leaves solution, end product is a new clay mineral. More stable minerals (ex. quartz) requires lower temperatures to crystallize. Less stable minerals (ex. pyroxene, olivine) require higher temperatures. Weight of accumulating sediment pushes grains together. Reduced pore space and water content: cementation. Pore water migrates up towards earth"s surface. Ions dissolved in the water precipitate form minerals that cement the grains together: recrystallization. Pressure causes less stable minerals to rearrange into more stable forms i. over time, aragonite in skeletal structures recrystallizes and becomes calcite which has a different crystal structure. Grain size indicates energy of the environment. Silt: 4 mm < x < 1/16 mm.