1 / 16

Metamorphic Rocks

Metamorphic Rocks. Metamorphic Rocks. Key Concept #1. How are metamorphic rocks formed?. extreme heat and/or pressure. Metamorphic Rocks. Key Concept #2. MELTING DOES NOT OCCUR!. If melting occurs, it is classified as an. Igneous Rock. New Minerals Form and Crystals Grow Larger.

allayna
Download Presentation

Metamorphic Rocks

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Metamorphic Rocks

  2. Metamorphic Rocks Key Concept #1 How are metamorphic rocks formed? extreme heat and/or pressure

  3. Metamorphic Rocks Key Concept #2 MELTING DOES NOT OCCUR! If melting occurs, it is classified as an Igneous Rock

  4. New Minerals Form and Crystals Grow Larger Mud Shale Slate Phyllite (Digenesis) Mica/chlorite grains start to align (> 200°C, 3Kbar) More chlorite (incl. Biotite), more foliation Gneiss Migmatite Schist Much more mica, and foliation. Porphyroblasts form (andalusite, kyanite and sillimanite, garnet, etc) More quartz, K-spar, less mica, ~600°C, “compositional layering” starts separating mafic from felsic 700 - 800°C (7.5Kbar) – partial melt, esp. the felsic regions

  5. Metamorphic Rocks - formed from other rocks, via. heat and pressure (and sometimes fluids) • Metamorphosis changes the mineral assemblages which are present in a rock • A Protolith is the original parent-rock from which a metamorphic rock is formed (i.e. limestone is the protolith of marble) • Occurs @ ~>200°C ~>3 kbars (3000ATM) • Typical geotherm depth = 25°C/Km, so ~8Km std. temp • 1 kbar per 3 km, so ~9 km depth

  6. Metamorphic Rocks: Key Concept #3 What is the difference between Regional and Contact Metamorphism?

  7. Regional Metamorphism Large geographic area Example: where mountains form

  8. Contact Metamorphism small geographic area Example: when rocks come in contact with magma

  9. Metamorphic Rocks: Key Concept #4 Key Identifying Features of Metamorphic Rocks

  10. Foliation Image #1 Image #2 banding or alignment of minerals usually black and white Image #3

  11. Examples of Foliation… Diagenesis Low grade High grade Intermediate grade Slate Phyllite Migmatite Schist (abundant micaceous minerals) Gneiss (fewer micaceous minerals) Schistosity Banding Banding Increasing intensity of metamorphism Low grade Intermediate grade High grade Increasing crystal size Increasing coarseness of foliation

  12. Distorted Structure folded layers Image #3 Image #1 Image #2

  13. Key Identifier Minerals Dark Red Color Garnet Shiny, flaky Mica

  14. New Minerals Form and Crystals Grow Larger Mud Shale Slate Phyllite (compaction and cementation) Mica/chlorite grains start to align (> 200°C, 3Kbar) More chlorite (incl. Biotite), more foliation Gneiss Migmatite Schist Much more mica, and foliation. Porphyroblasts form (andalusite, kyanite and sillimanite, garnet, etc) More quartz, K-spar, less mica, ~600°C, “compositional layering” starts separating mafic from felsic 700 - 800°C (7.5Kbar) – partial melt, esp. the felsic regions

More Related