METAMORPHIC ROCKS BEGIN

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1 METAMORPHIC ROCKS BEGIN

2 WHAT IS A METAMORPHIC ROCK? A metamorphic rock is a rock that has been changed by heat and/or pressure without completely melting.

3 Metamorphism metamorphism usually occurs deep underground where rocks are put under intense pressure or stress causing the rock deform metamorphism PRESSURE

4 Contact Metamorphism Contact Metamorphism occurs near magma or lava Contact metamorphism magma

5 A parent rock is the original rock that changed in a metamorphic rock metamorphic rock parent rock

6 There are two types of Metamorphic Rocks Foliated Nonfoliated Minerals line up due metamorphism Minerals don t line up

7 mineral growth without pressure Nonfoliated pressure mineral growth with pressure Foliated

8 Nonfoliated Foliated

9 P. 7 of ESRT Scheme for Metamorphic Rock Identification GRAIN TYPE OF TEXTURE SIZE COMPOSITION METAMORPHISM COMMENTS ROCK NAME MAP SYMBOL Foliated FOLIATED MINERAL ALIGNMENT BAND- ING medium Medium coarse MICA QUARTZ FELDSPAR AMPHIBOLE GARNET PYROXENE (Heat and pressure increases) Low-grade metamorphism of shale Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible from metamorphism of clay or feldspars High-grade metamorphism; mineral types segregated in bands Slate Phyllite Schist Gneiss Carbon bituminous coal Anthracite coal Nonfoliated NONFOLIATED coarse Various minerals Quartz Calcite and/or dolomite Contact (heat) or contact Various rocks changed by heat from nearby magma/lava quartz sandsne limesne or dolosne Hornfels Quartzite Marble Coarse Various minerals Pebbles may be disrted or stretched Metaconglomerate

10 Foliation Mineral Alignment minerals line up due pressure Banding under greater pressure minerals separate in dark and light stripes called bands

11 Mineral Alignment P. 7 of ESRT TEXTURE Scheme for Metamorphic Rock Identification GRAIN TYPE OF SIZE COMPOSITION METAMORPHISM COMMENTS ROCK NAME MAP SYMBOL FOLIATED MINERAL ALIGNMENT BAND- ING medium Medium coarse MICA QUARTZ FELDSPAR AMPHIBOLE GARNET PYROXENE (Heat and pressure increases) Low-grade metamorphism of shale Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible from metamorphism of clay or feldspars High-grade metamorphism; mineral types segregated in bands Slate Phyllite Schist Gneiss Banding

12 Intensity of Metamorphism Low-Grade Metamorphism Little change rock High-Grade Metamorphism extreme change rock

13 shale LOW-GRADE Sh slate ale s low ly c phyllite han ge s schist int og nei s s gneiss HIGH-GRADE

14 Sedimentary Rock Siltsne Shale ENTARY ROCKS P. 7 of ESRT TEXTURE Scheme for Metamorphic Rock Identification GRAIN TYPE OF SIZE COMPOSITION METAMORPHISM COMMENTS ROCK NAME MAP SYMBOL FOLIATED MINERAL ALIGNMENT BAND- ING medium Medium coarse MICA QUARTZ FELDSPAR AMPHIBOLE GARNET PYROXENE (Heat and pressure increases) Low-grade metamorphism of shale Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible from metamorphism of clay or feldspars High-grade metamorphism; mineral types segregated in bands Slate Phyllite Schist Gneiss As heat and pressure increases: NONFOLIATED Shale becomes Slate becomes Phyllite becomes Schist becomes Gneiss coarse Carbon Various minerals Quartz Calcite and/or dolomite Contact (heat) or bituminous coal Various rocks changed by heat from nearby magma/lava quartz sandsne limesne or dolosne Anthracite coal Hornfels Quartzite Marble

15 Surface of Earth 0 5 Clay deposits Inferred Shale Shale Sedimentary zone 10 Slate Depth (km) Metamorphic zone Phyllite Schist Gneiss Temperature ( o C) Key At these temperatures rock melts Boundary between sedimentary zone and metamorphic zone

16 P. 7 of ESRT TEXTURE Scheme for Metamorphic Rock Identification GRAIN TYPE OF SIZE COMPOSITION METAMORPHISM COMMENTS ROCK NAME FOLIATED MINERAL ALIGNMENT BAND- ING medium Medium coarse MICA QUARTZ FELDSPAR AMPHIBOLE GARNET PYROXENE (Heat and pressure increases) Low-grade metamorphism of shale Foliation surfaces shiny from microscopic mica crystals Platy mica crystals visible from metamorphism of clay or feldspars High-grade metamorphism; mineral types segregated in bands Slate Phyllite Schist Gneiss The minerals in Foliated Metamorphic rocks can be determined by looking at the bar graph in the composition section

17 Nonfoliated rocks sometimes indicate the parent rock Carbon bituminous coal Anthracite coal NONFOLIATED coarse Various minerals Quartz Calcite and/or dolomite Contact (heat) or contact Various rocks changed by heat from nearby magma/lava quartz sandsne limesne or dolosne Hornfels Quartzite Marble P. 7 of ESRT Coarse Various minerals Pebbles may be disrted or stretched Metaconglomerate