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Lab 7

Lab 7. Metamorphic Rocks. Metamorphic Rocks. Metamorphic rocks: rocks changed by T, P, or action of watery hot fluids Protolith : parent rock can be ign, sed, mm. Common minerals:.

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Lab 7

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  1. Lab 7 Metamorphic Rocks

  2. Metamorphic Rocks • Metamorphic rocks: • rocks changed by T, P, or action of watery hot fluids • Protolith: • parent rock • can be ign, sed, mm

  3. Common minerals: • Quartz, feldspars, muscovite, biotite, chlorite, garnet, tourmaline, calcite, dolomite, serpentine, talc, kyanite, sillimanite, staurolite, and amphibole • Minerals help you name the protolith Tourmaline Kyanite Garnet Serpentine Staurolite Sillimanite

  4. Metamorphic Processes • Contact metamorphism • Occurs locally  ign. intrusions • If hydrothermal fluids  hydrothermal mm • Low pressure

  5. Metamorphic Processes 2. Regional metamorphism: • Occurs over large regions  deep within cores of rising mountain ranges • High stress & high pressure • Result from large ign. intrusions that cool over time • May also have hydrothermal alteration

  6. Composition • Mineral composition after metamorphism: • Can stay the same • Recrystallization – small minerals will convert to larger crystals • Can change • Neomorphism – minerals recrystallize and form different minerals • Metasomatism – significant mineralogical change  chemicals are added or lost and form different minerals

  7. Textures - Foliated Foliated texture – layering  parallel alignment of platy minerals (micas) as a result of applied pressure • NOT depositional feature! • Slaty rock cleavage –more dense; clanky • Rock name: slate • Phyllite texture– wavy/wrinkled foliation; shine • Rock name: phyllite • Schistosity –visible platy minerals and/or alignment of long prismatic crystals; minerals visible; no comp banding • Rock name: schist • Gneissic banding – alternating layers; minerals visible; comp banding • Rock name: gneiss

  8. Textures – Nonfoliated • Nonfoliated texture – no layering • Crystalline texture – coarse grained crystals • Example: marble • Microcrystalline texture – fine grained crystals • Example: hornfels • Sandy texture – fused, sand-sized, resembles sandstone • Example: quartzite • Glassy texture – homogenous texture, no visible grains/structures • Example: anthracite coal

  9. Other Textures • Stretched or sheared grains • Porphyroblastic – large crystal in ground mass (like phenocryst) • Hydrothermal veins – fractures “healed” by ppt from hydrothermal fluids • Folds • Lineations – lines on rocks: foliations, shear planes, slaty cleavage, or aligned crystals.

  10. Today’s Lab • ID metamorphic rock samples (put rock #s in order) • May be more than one of the same thing • Identify important mineralogy in name: i.e., kyanite schist • Foliation demonstration • Campus building stone exercise

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