Study Notes on Metamorphism and Metamorphic Rocks

Chapter 7: Metamorphism and Metamorphic Rocks

Introduction to Metamorphism

  • Greek Origins:

    • Meta: Change

    • Morpho: Shape

  • Definition: The alteration of rocks beneath the Earth's surface; metamorphism.

  • Origin of Metamorphic Rocks: These can arise from:

    • Igneous rocks

    • Sedimentary rocks

    • Other metamorphic rocks

Agents of Metamorphism

  1. Heat

    • Role: Increases the rate of chemical reactions

    • Sources of Heat: Intrusive magma and Deep burial

  2. Pressure

    • Types of Pressure:

      • Lithostatic pressure: equally in all directions; caused by the weight of overlying rocks

      • Differential pressure: unequal forces applied to the rock, often due to tectonic forces during mountain building.

  3. Fluid Activity

Types of Metamorphism

  1. Contact Metamorphism

    • Definition: magma intrudes and thermally alters the surrounding country rock.

  2. Dynamic Metamorphism

    • Definition: exposure to high differential pressures, typically near faults.

    • makes mylonites

  3. Regional Metamorphism

    • Characteristics:

      • at convergent plate margins but can also occur in diverging areas.

      • extreme heat and pressure arising from tectonic processes at convergent plate boundaries.

Classification of Metamorphic Rocks

  1. Foliated Metamorphic Rocks

    • heat/differential pressure → parallel orientation = foliation.

  2. Nonfoliated Metamorphic Rocks

    • no preferred orientation of minerals.

    • ex. Marble and quartz