Metamorphic Rocks Notes
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METAMORPHIC ROCKS BEGIN WHAT IS A METAMORPHIC ROCK? A metamorphic rock is a rock that has been changed by heat and/or pressure without completely melting. LAST NEXT Regional Metamorphism Regional metamorphism usually occurs deep underground where rocks are put under intense pressure or stress causing the rock to deform Regional metamorphism LAST PRESSURE NEXT Contact Metamorphism Contact Metamorphism occurs near magma or lava Contact metamorphism magma LAST NEXT A parent rock is the original rock that changed into a metamorphic rock metamorphic rock parent rock LAST NEXT There are two types of Metamorphic Rocks Foliated Nonfoliated Minerals line up due to metamorphism Minerals don’t line up LAST NEXT salt salt Rock RockBB Gabbro Rock RockCC NEXT Limestone Foliated g. ’03 ug. ’03 Mineral Mineral Arrangement Arrangement Before Before Metamorphism Metamorphism pressure Stress Stress Rock RockCCShowing ShowingBanding Banding After AfterMetamorphism Metamorphism Stress Stres Stress Stres LAST Stress Stress [19] [19] mineral growth with pressure 78 78 The The diagram diagram below below represents represents two two magnified magnified views views showing showing the thearrangement arrangementofo minerals minerals before beforeand andafter aftermetamorphism metamorphismofofrock rockC. C.State Statethe thename nameofofrock rockC. C. [1[]1 77 77 Granite Granite could could be be placed placed in in the the same same position position inin the the flowchart flowchart above aboveasasgabbro. gabbro Describe Describe two twodifferences differencesbetween betweengranite graniteand andgabbro. gabbro. [1[1]] 76 76 Rock Rock BBhas hasaaglassy, glassy,vesicular vesiculartexture textureand andisiscomposed composedmainly mainlyofofpotassium potassiumfeldspar feldspa and and quartz. quartz.State Statethe thename nameof ofrock rockB. B. [[11]] 75 75 Rock Rock AA isis composed composed of of very veryfine-grained fine-grainedquartz quartzand andfeldspar feldsparparticles particles0.005 0.005centicent meter meter in in diameter. diameter.State Statethe thename nameof ofrock rockA. A. [1[1]] Nonfoliated mineral growth without pressure Nonfoliated LAST Foliated NEXT crystals and evaporites Dolostone Dolomite Crystalline or bioclastic Microscopic to very coarse Bioclastic P. 7 of ESRT TEXTURE GRAIN SIZE Calcite Precipitates of biologic origin or cemented shell fragments Carbon Compacted plant remains Nonfoliated COMPOSITION TYPE OF METAMORPHISM AMPHIBOLE GARNET PYROXENE Medium to coarse Regional (Heat and pressure increases) MICA QUARTZ FELDSPAR MINERAL ALIGNMENT NONFOLIATED BANDING FOLIATED Foliated Fine Carbon Regional Fine Various minerals Contact (heat) Fine to coarse Coarse Bituminous coal Scheme for Metamorphic Rock Identification Fine Fine to medium Limestone Quartz COMMENTS ROCK NAME Low-grade metamorphism of shale Slate Foliation surfaces shiny from microscopic mica crystals Phyllite Platy mica crystals visible from metamorphism of clay or feldspars Schist High-grade metamorphism; mineral types segregated into bands Gneiss Metamorphism of bituminous coal MAP SYMBOL Anthracite coal Various rocks changed by heat from nearby magma/lava Hornfels Metamorphism of quartz sandstone Quartzite Regional Calcite and/or dolomite or contact Various minerals Metamorphism of limestone or dolostone Pebbles may be distorted or stretched Marble Metaconglomerate Physical Setting/Earth Science Reference Tables — 2011 Edition LAST NEXT Foliation Mineral Alignment minerals line up due to pressure Banding under greater pressure minerals separate into dark and light stripes called bands LAST NEXT Dolostone Dolomite Crystalline or bioclastic Microscopic to very coarse Mineral Alignment Bioclastic P. 7 of ESRT TEXTURE Calcite Precipitates of biologic origin or cemented shell fragments Carbon Compacted plant remains GRAIN SIZE COMPOSITION TYPE OF METAMORPHISM Medium to coarse Fine Carbon Regional Fine Various minerals Contact (heat) Banding NONFOLIATED AMPHIBOLE GARNET PYROXENE Fine to medium Regional (Heat and pressure increases) MICA QUARTZ FELDSPAR MINERAL ALIGNMENT BANDING FOLIATED Bituminous coal Scheme for Metamorphic Rock Identification Fine LAST Limestone Fine to coarse Quartz COMMENTS ROCK NAME Low-grade metamorphism of shale Slate Foliation surfaces shiny from microscopic mica crystals Phyllite Platy mica crystals visible from metamorphism of clay or feldspars Schist High-grade metamorphism; mineral types segregated into bands Gneiss Metamorphism of bituminous coal MAP SYMBOL Anthracite coal Various rocks changed by heat from nearby magma/lava Hornfels Metamorphism of quartz sandstone Quartzite Regional Calcite and/or dolomite or Metamorphism of limestone or dolostone Marble NEXT Intensity of Metamorphism Low-Grade Metamorphism Little change to rock High-Grade Metamorphism extreme change to rock LAST NEXT shale LOW-GRADE LAST Sh slate ale s low ly c phyllite han ge s schist int oG nei s s gneiss HIGH-GRADE NEXT crystals crystals Silt (0.0004 to 0.006 cm) fragments of other rocks Dolomite Dolomite and minerals Clay (less than 0.0004 cm) Microscopic to to Microscopic very coarse coarse AND/OR very CHEMICALLY Crystalline or or Crystalline bioclastic bioclastic Bioclastic Bioclastic TEXTURE GRAIN SIZE and evaporites evaporites and Very fine grain Sedimentary Rock Calcite Calcite Compact; split Precipitatesmay of biologic biologic Precipitates of origin or or cemented cemented shell shell origin easily fragments fragments Siltstone Dolostone Dolostone Shale Limestone Limestone ORGANICALLY Compacted FORMED SEDIMENTARY ROCKS Compacted Carbon Carbon COMPOSITION plant remains remains plant COMMENTS Halite Bituminous coal coal Bituminous ROCK NAME FineScheme for Metamorphic Rock Identification Crystals from to chemical Gypsum Rock gypsum GRAIN coarse TYPE OF GRAIN TYPE OF precipitates TEXTURE COMPOSITION COMMENTS ROCK NAME NAME TEXTURE COMPOSITION COMMENTS ROCK SIZE METAMORPHISM SIZE METAMORPHISM crystals and evaporites Dolostone Dolomite Low-grade Low-grade Fine Slate Fine Slate metamorphism of of shale shale metamorphism Precipitates of biologic Regional Crystalline or Regional origin or cemented shell Calcite Limestone Foliation surfaces shiny bioclastic Foliation surfaces shiny (Heat and and fragments Microscopic to (Heat from microscopic mica mica Phyllite from microscopic Phyllite pressure pressure Fine very coarse Fine Compacted crystals crystals increases) Bioclastic Bituminous coal increases) Carbon to to plant remains medium medium Platy mica mica crystals crystals visible visible Platy from metamorphism metamorphism of of clay clay from Schist Schist or feldspars feldspars or Fine Fine Fine AMPHIBOLE AMPHIBOLE GARNET GARNET PYROXENE PYROXENE TEXTURE Medium Medium to to GRAIN coarse coarse SIZE MICA MICA QUARTZ QUARTZ FELDSPAR FELDSPAR MINERAL MINERAL ALIGNMENT ALIGNMENT BANDBANDING ING FOLIATED FOLIATED P. Crystalline 7 of ESRT . . . . . . . . . . . . . . . . . . MAP SYMBOL Rock salt MAP SYMBOL SYMBOL MAP Scheme for Metamorphic Rock Identification COMPOSITION Carbon Carbon TYPE OF METAMORPHISM Regional Regional Regional (Heat and Contact Contact pressure (heat) (heat) increases) High-grade metamorphism; metamorphism; High-grade mineral types types segregated segregated mineral COMMENTS into bands bands into Low-grade Metamorphism of of Metamorphism metamorphism of bituminous coal coal shale bituminous Gneiss Gneiss ROCK NAME MAP SYMBOL Slate coal Anthracite Anthracite coal Fine Fine to to Medium coarse coarse to AMPHIBOLE GARNET YROXENE LAST Fine Fine to medium Various Various minerals minerals MICA QUARTZ FELDSPAR ANDMINERAL NONFOLIATED NONFOLIATED ING ALIGNMENT FOLIATED As heat and pressure increases: Shale becomes Slate becomes Phyllite becomes Schist becomes Gneiss Quartz Quartz Calcite and/or and/or Calcite dolomite Regional Regional or or Foliation surfaces shiny by Various rocks rocks changed by Various changed from microscopic mica heat from from nearby nearby heat crystals magma/lava magma/lava Phyllite Hornfels Hornfels Platy mica crystals visible Metamorphism of of clay Metamorphism of from metamorphism quartz sandstone or feldspars quartz sandstone Schist Quartzite Quartzite High-grade metamorphism; Metamorphism of mineral types segregated Metamorphism of limestone into bands or dolostone Gneiss Marble Marble NEXT types that form from original clay deposits at certain depths and temperature conditions within Earth’s interior. Inferred Metamorphism of Shale Surface of Earth 0 Clay deposits Shale 5 Slate 10 Depth (km) Sedimentary zone Phyllite 15 20 Schist Metamorphic zone 25 Gneiss 30 0 200 800 400 600 Temperature (oC) 1000 Key At these temperatures rock melts Boundary between sedimentary zone and metamorphic zone LAST 55 When clay materials are buried to a depth of 14 kilometers, which type of meta- NEXT Bioclastic Carbon GRAIN SIZE COMPOSITION TYPE OF METAMORPHISM Medium to coarse Fine AMPHIBOLE GARNET PYROXENE Fine to medium Regional (Heat and pressure increases) MICA QUARTZ FELDSPAR BANDING MINERAL ALIGNMENT Fine FOLIATED Bituminous coal Scheme for Metamorphic Rock Identification P. 7 of ESRT TEXTURE plant remains Carbon Regional COMMENTS ROCK NAME Low-grade metamorphism of shale Slate Foliation surfaces shiny from microscopic mica crystals Phyllite Platy mica crystals visible from metamorphism of clay or feldspars Schist High-grade metamorphism; mineral types segregated into bands Gneiss Metamorphism of bituminous coal MAP SYMB Anthracite coal NONFOLIATED The minerals in Foliated Metamorphic rocks can be determined by looking at the bar graph in the composition section Fine Fine to coarse Coarse LAST Various minerals Contact (heat) Quartz Various rocks changed by heat from nearby magma/lava Hornfels Metamorphism of quartz sandstone Quartzite Regional Calcite and/or dolomite Various minerals or contact Metamorphism of limestone or dolostone Pebbles may be distorted or stretched Marble Metaconglomerate NEXT SIZE METAMORPHISM Low-grade metamorphism of shale Slate NONFOLIATED P. 7 of ESRT Medium to coarse AMPHIBOLE GARNET PYROXENE Fine to medium Regional (Heat and pressure increases) MICA QUARTZ FELDSPAR MINERAL ALIGNMENT Nonfoliated rocks sometimes indicate the parent rock BANDING FOLIATED Fine Fine Carbon Regional Fine Various minerals Contact (heat) Fine to coarse Coarse Quartz Foliation surfaces shiny from microscopic mica crystals Phyllite Platy mica crystals visible from metamorphism of clay or feldspars Schist High-grade metamorphism; mineral types segregated into bands Gneiss Metamorphism of bituminous coal Anthracite coal Various rocks changed by heat from nearby magma/lava Hornfels Metamorphism of quartz sandstone Quartzite Regional Calcite and/or dolomite or contact Various minerals Metamorphism of limestone or dolostone Pebbles may be distorted or stretched Marble Metaconglomerate 7 hysical Setting/Earth Science Reference Tables — 2011 Edition LAST NEXT
