Intro to Metamorphic Rocks and the Rock Cycle

Intro to Metamorphic Rocks and the Rock Cycle 1. Types of metamorphic rocks Classified based on texture (the size, shape and arrangement of the minerals) Two groups: foliated and non-foliated Foliated texture: Foliation: layering Minerals become aligned perpendicular to the directed stress Add figure increasing metamorphism increasing foliation increasing grain size For example: mica grains get larger and the shininess increases from Slate to Phyllite to Schist to Gneiss With temperature and pressure increasing Gneissic layering—distinctive bands of light and dark minerals Migmatite-partial melt: melt the light colored minerals leucosomes melanosomes Nonfoliated texture Grains are interlocking such as puzzle pieces Two examples: Quartzite—sandstone is metamorphosed into quartzite Can be different colors depending on the composition of sandstone Marble—limestone is metamorphosed into marble Marble can have different colors depending on the composition of the limestone. Way to distinguish: A drop of dilute hydrochloric acid If effervesces / gas bubblesmarble (calcite in the limestone) Example: acid on the quartzite and marble This figure shows acid rain corrosive effects on sculptures 60 years later, it changed from left to right 2. Parent rock -- is the original rock, before metamorphism With increasing temperature/pressure/fluids ShaleSlatePhylliteSchistGneiss (partially melted) Migmatite 3. How to identify Step 1—foliated or non-foliated If non-foliated, use acid. If gas bubblemarble If no gasquartzite Step 2—foliated Look at the grain size Larger the grain size, higher degree of metamorphism Classification of metamorphic rocks based on texture: Example: list all foliated samples 4. The rock cycle Depicts the relationship between igneous, sedimentary and metamorphic rocks. Igneous rocks can turn to metamorphic rocks (metamorphosed) / sedimentary rocks / igneous rocks Sedimentary rocks can form from the erosion and weathering of igneous, metamorphic or other sedimentary rocks Any rock with increasing temperature, pressure, or adding fluids, can form a metamorphic rock Add figure rock cycle 5. Classification of rocks based on texture and composition texture is the size and shape of mineral grains and their relationship textures for each rock type Rock Types Textures Igneous Rocks Phaneritic, Aphanitic, Porphyritic, Glassy, Vesicular, Pyroclastic Metamorphic Rocks Foliated and Non-foliated Sedimentary Rocks Clastic and Non-clastic (chemical, biochemical, organic) I hope this helps. Thank you for watching. Music: A Quiet Thought