02.11.14 EES 1030 Lecture 7 Outline of Last Lecture I. Lecture 6: Sediments and Sedimentary RocksII. Sedimentary RocksIII. Sediments vs. Sedimentary Rocks:IV. Types of Sedimentary RocksV. Detrital Sedimentary RocksVI. Chemical Sedimentary RocksVII. Sedimentary StructuresOutline of Current Lecture VIII.Metamorphic RocksIX. Agents of Metamorphism: HeatX. Agents of Metamorphism: PressureXI. Agents of Metamorphism: FluidsXII. Metamorphic TexturesXIII.Metamorphic Textures: FoliationXIV. Metamorphic Rocks: Non-FoliatedXV. Metamorphic EnvironmentsCurrent Lecture- Metamorphic Rockso Changes in mineralogy, texture, and often chemical composition of a solid rock subjected to conditions very different to those in which it initially formed.o Effects of metamorphism depend on parent rock (protolith): Igneous, Sedimentary, Metamorphic.- Agents of Metamorphism: Heato Heat: provides energy for chemical reactions. Chemical reactions occur at faster rates. Recrystallization of existing minerals Formation of new stable mineralso Sources of Heat Geothermal gradiant: T increase with depth  Local intrusion of magma- Agents of Metamorphism: Pressureo Pressure: also increases with depth as thickness of overlying rocks increaseso Confining pressue: applies force equally in all directionso Produces a compact, more dense rock.o Directed pressure of Differential Stress: forces are unequal in different directionsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Agents of Metamorphism: Fluidso Chemically-active Fluids: Mainly water, with other volatiles. Chemical reactions take place faster and at lower temperatures in the presence of water than under dry conditions. Changes composition of rock.o Sources of Fluids: Hydrated minerals: clays and micas. Fluids from magma intrusions. Pore waters in sedimentary rocks.- Metamorphic Textureso Physical changes during metamorphismo Texture: Size, shape and arrangement of mineral grains.o Reorientation of rod or plate-shaped crystalso Recrystallization of minerals resulting in fewer but larger grains.o Creation of new stable minerals- Metamorphic Textureso Porphyroblastic texture: Large grains surrounded by fine-grained matrix of minerals.o Foliation: Any planar arrangement of mineral grains or structural features within a rock.o Rotation: Of platy and/or elongated mineralso Recrystallization Of minerals in the direction of preferred orientation- Metamorphic Textures: Foliationo Rocks or slaty cleavage: Closely spaced planar surfaces along which rocks easily split into thin, tabular sheets Recrystallization and alignment of mica grains: Quartz & feldspar not affected.o Schistocity: Higher metamorphic grade – larger crystals. Platy minerals are discernible with naked eye and exhibit a planar or layered structure.o Phyllite: platy minerals larger than in slate but not quite large enough to see with eye. Exhibits rock cleavage. Mainly fine crystals of muscovite.o Schist: medium to coarse-grained rock. Platy minerals (mainly micas) predominate.o Gneiss: parent rock = schist, granite, volcanic medium to coarse grained rock. Banded appearance = “gneissic” texture. High-grade metamorphic rocko Migmatite: transition from high-grade metamorphic rock to igneous rock.- Metamorphic Rocks: Non-Foliatedo Marble: parent rock = limestone or dolostone coarse crystalline calcite o Quartzite: parent rock = quarts-rich sandstone Quartz grains fused together  v. hard rock- Metamorphic Gradeo Index minerals: Certain minerals are good indicators of metamorphic conditions. Minerals formed depend on original rock type.- Metamorphic Environmentso Geothermal gradient & metamorphism:o Contact or thermal metamorphism.o Increase in heat due to intrusion of hot magma.o Local effect.o Zone of alteration called an aureole corms in country rock around the intrusion.o Hornfels: general term for rather hard, non-foliated metamorphic rocks formed in aureoleo Hydrothermal metamorphism: Chemical alteration as hot, ion-rich fluids circulate through fissures and cracks that develop in rocko Impact metamorphism: meteorites hit Earth at high-velocityo Regional metamorphism:  greatest quantities of metamorphic rocks.o Occurs when rocks are squeezed between two