MINERALS AND ROCKS IN THE EARTH

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MINERALS AND ROCKS IN THE EARTHS CRUST

• Igneous, Sedimentary, Metamorphic Rocks and
  Environments

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MINERALS AND ROCKS COME FROM ELEMENTS

• Chemical elements are the fundamental materials
  of which all matter is composed.
• From the modern viewpoint
• a substance that cannot be broken down or reduced
  further

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PERIODIC TABLE OF ELEMENTS




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MAKING MINERALS FROM ELEMENTS

• ALMOST ALL THE MINERALS FOUND IN THE EARTH ARE
  FORMED FROM THE BONDING OF EIGHT (8) ELEMENTS
• OXYGEN (O)
• SILICON (Si)
• ALUMINIUM (Al)
• IRON (Fe)
• CALCIUM (Ca)
• POTASSIUM (K)
• SODIUM (Na)
• MAGNESIUM (Mg)

MOST ABUNDANT
LEAST ABUNDANT
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WHAT ARE MINERALS?

• BUILDING BLOCKS FOR ROCKS
• DEFINITION
• NATURALLY OCCURRING,
• INORGANIC SOLIDS,
• CONSISTING OF SPECIFIC CHEMICAL ELEMENTS, AND
• A DEFINITE ATOMIC ARRAY
• CRYSTALLINE STRUCTURE CRYSTAL
• CRYSTAL AND MINERAL INTERCHANGEABLE TERMS

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MINERALS

• Minerals divided into two main groups based on
  Silica content
• Silica (SiO) compound of molecularly bonded
  silicon (Si) and oxygen (O) molecules (SiO,
  SiO2, SiO4, SiO6 etc.)
• GROUP 1 SILICATES CONTAIN SILICA
• GROUP 2 NON-SILICATES (CONTAIN NO SILICA)

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NON-SILICATE MINERALS

• Non-silicate minerals are very rare
• Make up 5 of Earths continental crust
• Considered valuable commercially as building
  materials, gemstones, iron ores for steel,
  ceramics, and more.
• Native metals gold, silver, copper, platinum
• Native elements diamonds, corundum Ruby (red)
  or Sapphire (blue)
• Carbonates calcite (used in cement)
• Oxides hematite (iron ores)
• Sulfides galena (lead ores)
• Sulfates gypsum (used in plaster, dry wall)
• Halides halite (table salt)

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SILICATE MINERALS

• THE MOST ABUNDANT OF ALL MINERALS
• MAKE UP APPROXIMATELY 95 OF WEIGHT OF EARTHS
  CRUST
• CONTAIN VARYING AMOUNTS OF SILICA (SiO)
• DOMINANT COMPONENT OF MOST ROCKS
• IGNEOUS
• SEDIMENTARY
• METAMORPHIC

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SILICATE MINERALS

• LISTED BELOW IN DECREASING OF SILICA ARE MOST
  COMMON SILICATE MINERALS
• QUARTZ (SiO2) (High Silica content 100)
• FELDSPARS (PLAGIOCLASE - (Na,Ca)(Si,Al)4O8 )
• MICAS (MUSCOVITE -KAl2(AlSi3O10)(F, OH)2 and
• BIOTITE - K (Fe, Mg)3 AlSi3 O10 (F, OH)2 )
• AMPHIBOLES (Hornblende -Ca2(Fe,Mg)5Si8O22(OH2)
• PYROXENES (Augite (Mg,Fe) SiO3)
• OLIVINE - (Mg, Fe)2SiO4, (Low Silica
  content 40)

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SILICATE MINERALS

• SILICATE MINERALS ARE BROKEN INTO THREE MAIN
  GROUPS ACCORDING TO SILICA
• FELSIC High percent
• MAFIC
• ULTRAMAFIC Low percent

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FELSIC SILICATE MINERALS

• FELSIC SILICATE MINERALS HAVE A HIGH
  CONCENTRATION OF SILICON, OXYGEN, ALUMINIUM AND
  POTASSIUM
• FELSIC SILICATES HIGH SiO (75-100)
• QUARTZ (100 SiO2)
• FELDSPARS (Plagioclase, Orthoclase)
• MUSCOVITE MICA

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QUARTZ
FELDSPAR
MUSCOVITE MICA
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MAFIC SILICATE MINERALS

• MINERALS WITH HIGH CONCENTRATION OF MAGNESIUM AND
  IRON, PLUS CALCIUM AND SODIUM, AND LOWER AMOUNTS
  OF SILICON AND OXYGEN
• MAFIC SILICATES - LESS SiO (50-60)
• BIOTITE MICA
• AMPHIBOLE (Hornblende)
• PYROXENE (Augite)

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BIOTITE MICA
PYROXENE (AUGITE)
AMPHIBOLE (HORNBLENDE)
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ULTRAMAFIC SILICATES

• MINERALS WITH GREATER CONCENTRATION IN MAGNESIUM
  AND IRON. VERY RARE AT EARTHS SURFACE
• ULTRA MAFIC SILICATES - VERY LOW SiO (less than
  50)
• VERY RARE AT SURFACE
• OLIVINE (FORSTERITE, FAYALITE)

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WHAT ARE ROCKS?

• AGGREGATIONS OF 2 OR MORE MINERALS
• Same or different minerals combine together
• THREE CATEGORIES
• IGNEOUS
• SEDIMENTARY
• METAMORPHIC

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IGNEOUS ROCKS

• Ignis Latin for Fire
• FORMED FROM COOLED, SOLIDIFIED MOLTEN MATERIAL
  AT, NEAR, OR DEEP BELOW, THE SURFACE
• TYPES
• PLUTONIC (INTRUSIVE) IGNEOUS ROCKS COOLED AND
  SOLIDIFIED BELOW SURFACE AT GREAT DEPTHS
• VOLCANIC (EXTRUSIVE) IGNEOUS ROCKS COOLED AND
  SOLIDIFIED AT OR NEAR THE SURFACE THROUGH
  VOLCANIC ERUPTIONS

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IDENTIFICATION OF IGNEOUS ROCKS

• TWO IDENTIFICATION PROCESSES FOR PLUTONIC OR
  VOLCANIC IGNEOUS ROCKS
• TEXTURE
• Size, shape and manner of growth of individual
  crystals
• MINERAL COMPOSITION
• Based on SiO content
• Felsic, Intermediate, Mafic
• (high Silica low Silica)

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TEXTURE IDENTIFICATION

• SIZE, SHAPE OF CRYSTALS AND MANNER OF GROWTH
• FINE GRAINED TEXTURE
• VERY TINY, MINERAL CRYSTALS VISIBLE ONLY WITH
  MAGNIFICATION
• INDICATES FAST COOLING AT SURFACE CRYSTALS
  SOLIDIFIED QUICKLY WITH NO TIME TO GROW
• COARSE-GRAINED TEXTURE
• LARGE, EASILY-VISIBLE MINERAL CRYSTALS
• INDICATES SLOW COOLING AT DEPTH CRYSTALS
  SOLIDIFIED SLOWLY WITH LOTS OF TIME TO GROW

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TEXTURE IDENTIFICATION
Fine-Grained Textures
Coarse-Grained Textures
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MINERAL COMPOSITION

• CLASSIFIED BY SILICA (SiO) CONTENT
• FELSIC MORE THAN 85 SILICA
• INTERMEDIATE 60-85 SILICA
• MAFIC LESS THAN 60 SILICA

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MINERAL COMPOSITION OF COMMON IGNEOUS ROCKS

• FELSIC IGNEOUS ROCKS (gt85 SiO)
• GRANITE
• PLUTONIC-INTRUSIVE PHANERITIC TEXTURE FELSIC
  MINERAL COMPOSITION
• RHYOLITE
• VOLCANIC-EXTRUSIVE APHANITIC TEXTURE FELSIC
  MINERAL COMPOSITION
• INTERMEDIATE IGNEOUS ROCKS (60-85 SiO)
• DIORITE
• PLUTONIC-INTRUSIVE PHANERITIC TEXTURE
  INTERMEDIATE MINERAL COMPOSITION
• ANDESITE
• VOLCANIC-EXTRUSIVE APHANITIC TEXTURE
  INTERMEDIATE MINERAL COMPOSITION
• MAFIC IGNEOUS ROCKS (lt60 SiO)
• GABBRO PLUTONIC-
• INTRUSIVE PHANERITIC TEXTURE MAFIC MINERAL
  COMPOSITION
• BASALT
• VOLCANIC-EXTRUSIVE APHANITIC TEXTURE MAFIC
  MINERAL COMPOSITION

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FELSIC IGNEOUS ROCKS
RHYOLITE
EXTRUSIVE
INTRUSIVE
GRANITE
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INTERMEDIATE IGNEOUS ROCKS
ANDESITE
EXTRUSIVE
DIORITE
INTRUSIVE
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MAFIC IGNEOUS ROCKS
GABBRO
INTRUSIVE
BASALT
EXTRUSIVE
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IGNEOUS ROCKS
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OTHER IGNEOUS ROCKS

• VOLCANIC GLASS
• OBSIDIAN VOLCANIC-EXTRUSIVE NO CRYSTALS FORM
  SILICA-RICH, COOLED INSTANEOUSLY
• PUMICE VOLCANIC-EXTRUSIVE NO CRYSTALS FORM
  SILICA-RICH SOLIDIFIED FROM GASSY LAVA
• PYROCLASTIC ROCKS
• TUFF VOLCANIC-EXTRUSIVE SOLIDIFIED WELDED ASH

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VOLCANIC GLASS
OBSIDIAN
PUMICE
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PYROCLASTIC IGNEOUS ROCKS
WELDED TUFF
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SEDIMENTARY ROCKS

• WEATHERING PROCESSES BREAK ROCK INTO PIECES,
  SEDIMENT.
• READY FOR SEDIMENTATION PROCESSES
• TRANSPORTATION DEPOSITION BURIAL AND
  LITHIFICATION INTO NEW ROCKS.

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SEDIMENTARY PROCESSES

• LITHIFICATION
• As sediment is buried several kilometers beneath
  the surface, heated from below, pressure from
  overlying layers, heat, and chemically-active
  water converts the loose sediment into solid
  sedimentary rock
• Compaction - volume of a sediment is reduced by
  application of pressure
• Cementation - sediment grains are bound to each
  other by materials originally dissolved during
  chemical weathering of preexisting rocks
• typical chemicals include silica and calcium
  carbonate.

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CLASSIFYING SEDIMENTARY ROCKS

• THREE SOURCES FOR SEDIMENTARY ROCKS
• Detrital (or clastic) sediment is composed of
  transported solid fragments (or detritus) of
  pre-existing igneous, sedimentary or metamorphic
  rocks
• Chemical sediment forms from previously dissolved
  minerals that either precipitated from solution
  in water, or were extracted from water by living
  organisms
• Organic sedimentary rock consisting mainly of
  plant remains

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CLASTIC/DETRITAL SEDIMENTARY ROCKS

• CLASSIFIED ON GRAIN OR PARTICLE SIZE
• Shales finest-grained
• Sandstones medium-grained
• Conglomerates Breccias coarse-grained

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SHALES CLASTIC SEDIMENTARY

• SHALES finest-grained clastic sedimentary rocks
  composed of very small particles (from
  lt0.004-0.063 mm)
• 50 of all sedimentary rocks are Shales
• Consist largely of Clay minerals (weathered
  granite in many cases)
• Subcategories Claystones Siltstones Mudstones
• Economic value building material china and
  ceramics spark plug housings

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SHALES
Burgess Shale in Canada
Limestone on black shale
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MUDSTONES, SILTSTONES
Identified by decreasing amounts of sand and
increasing amounts of clay
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SANDSTONES

• SANDSTONES medium-grained clastic sedimentary
  rocks particle-size (0.063-2 mm)
• 25 of all sedimentary rocks fall into this
  category
• Economic value glass natural reservoirs for
  oil, gas, and groundwater

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SANDSTONES
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CONGLOMERATES - BRECCIAS

• CONGLOMERATES AND BRECCIAS
• The coarsest of all the clastic sedimentary rocks
  
• Composed of particles gt2 mm in diameter
• Conglomerate - the particles are rounded
• Breccia - the particles are angular

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CONGLOMERATES
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BRECCIAS
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CHEMICAL SEDIMENTARY ROCKS

• TWO CATEGORIES
• INORGANIC CHEMICAL SEDIMENTARY
• ORGANIC CHEMICAL SEDIMENTARY

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INORGANIC CHEMICAL SEDIMENTARY ROCKS

• Formed when dissolved products of chemical
  weathering precipitate (form out of) from
  solution
• Most common types
• Inorganic limestones and cherts precipitates
  directly from seawater and fresh water
• Evaporites precipitates when ion-rich water
  evaporates
• Dolostones Origin is still in debate

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INORGANIC - LIMESTONES

• Limestones - account for 10 - 15 of all
  sedimentary rocks formed from Calcite or Calcium
  Carbonate (CaCO3).
• Formed as pure carbonate muds accumulate on the
  sea floor
• Also formed on land
• Tufa - a soft spongy inorganic limestone that
  forms where underground water surfaces
• Travertine - forms in caves when droplets of
  carbonate-rich water on the ceiling, walls and
  floors precipitate a carbonate rock stalactites
  and stalagmites

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LIMESTONES
TRAVERTINE
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ORGANIC LIMESTONES

• Formed with calcite from marine environment
  CaCO3 shells and internal/external skeletons of
  marine animals
• Coquina - crushed shell fragments cemented with
  CaCO3
• Chalk - made from billions of microscopic
  carbonate- secreting organisms
• Coral Reefs - Formed from the skeletons of
  millions of tiny invertebrate animals who
  secrete a calcite-rich material. Live condo
  style while algae acts as the cement to create
  the large structures called reefs.
• Organic Chert - formed when silica-secreting
  microscopic marine organisms die (radiolaria
  single-celled animals and diatoms skeletons
  of singled-celled plants)
• Flint - an example of an Inorganic Chert

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COQUINA, CHALK AND FOSSILIFEROUS LIMESTONES
COQUINA
FOSSILIFEROUS LIMESTONE
CHALK
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ORGANIC SEDIMENTARY ROCKS

• Coal - Organic sedimentary rock consisting mainly
  of plant remains
• Formation
• Burial of decaying vegetation
• Increasing pressure from the overlying layers
  expels water, CO2 and other gases
• Carbon accumulates.
• STAGES
• Peat - formed early in the process, when the
  original plant structure
• can still be distinguished.
• Lignite - a more hardened form of Peat
• Bituminous - more pressure and more heat produce
  this moderately
• hard coal.
• Anthracite - the hardest coal - formed from
  metamorphic processes
• under extreme heat and pressure - Hard - Shiny
  - the most
• desired as an energy resource.

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COAL
PEAT
LIGNITE
ANTHRACITE
BITUMINOUS
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SEDIMENTARY ENVIRONMENTS

• Lakes
• Lagoons
• Rivers
• Ocean bottoms
• Estuaries
• Salt Flats
• Playas
• Glacial environments

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METAMORPHIC ROCKS

• METAMORPHISM process by which conditions within
  the Earth alter the mineral content and structure
  of any rock - igneous, sedimentary or metamorphic
  - without melting it.
• Metamorphism occurs when heat and pressure exceed
  certain levels, destabilizing the minerals in
  rocks...but not enough to cause melting
• Ion-rich fluids circulating in and around rocks
  also influences metamorphism

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METAMORPHIC PROCESSES

• HEAT
• (2000 C or 4000 F) reached near 10 km (6 miles)
  beneath the surface.
• PRESSURE
• gt 2 bar or 2000 mb, which is generally found 6
  km (4 miles) beneath the Earths surface
• FLUIDS Chemically-active water is the usual
  fluid and comes from various sources

TEMPERATURE/PRESSURE For every 3 kilometers
depth in the Earth, pressure increases by about 1
kb. Average temperature gradient in the Earth
increases 30 C per km
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CHANGES IN METAMORPHIC ROCKS

• Metamorphic processes cause many changes in rocks
  
• Increased density
• Growth of larger crystals
• FOLIATION reorientation of the mineral grains
  into layers or banded texture
• Transformation of low-temperature minerals into
  high-temperature minerals

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CLASSIFYING METAMORPHIC ROCKS

• TEXTURE the size, shape and distribution of
  particles in a rock
• texture is determined by grade of metamorphism
• Low grade (less than 6000C and 4 kilobars
  pressure)
• Intermediate grade occurs at a variety of
  temperatures and pressures.
• High grade (greater than 6000C and 4 kilobars
  pressure)

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FOLIATED TEXTURES

• Foliated texture more pressure and mineral
  grains realign themselves and grow into larger
  crystals
• Three types of foliated texture
• Rock or Slaty Texture
• Schistosity
• Gneissic Texture

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ROCK SLATY TEXTURE - SLATE

• Shale metamorphosed to Slate
• clay minerals (stable at surface temperatures
  and pressures) become unstable and recrystallize
  into mica crystals
• Slate is formed under Low-Grade Metamorphism

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SLATE
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SCHISTOCITY - SCHIST

• More extreme pressures and temperatures mica
  crystals grow even larger - 1 cm in diameter.
• rock has scaly appearance - schistosity,
• referred to as a Schist.
• Schists formed under Intermediate-Grade
  Metamorphism
• Schists named for the mineral constituents in the
  parent rock
• mica schist
• talc schist
• garnet schist

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SCHIST
Mica schist
Ruby schist
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GNEISSIC TEXTURE - GNEISS

• Light and dark silicate minerals separate and
  re-align themselves into bands
• Rocks with this texture are called Gneiss
• Gneiss forms from High Grade Metamorphism
• Typical parent rocks for Gneiss
• granite
• diorite
• gabbro
• shale

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GNEISS
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NON-FOLIATED TEXTURES

• Rocks with only one mineral metamorphose without
  a visibly foliated texture
• Limestone metamorphoses into Marble as the
  interlocking calcite crystals grow larger
• Quartz Sandstone metamorphoses into Quartzite

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MARBLE AND QUARTZITE
MARBLE
QUARTZITE
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METAMORPHIC ENVIRONMENTS

• CONTACT METAMORPHISM
• Metamorphism of a rock touched by the intense
  heat of migrating magma.
• REGIONAL METAMORPHISM
• Burial metamorphism - occurs when rocks are
  overlain by more than 6 miles of rock or sediment
• Dynamothermal metamorphism - occurs when rocks
  are caught between two convergent plates during
  mountain building
• OTHER METAMORPHIC ENVIRONMENTS
• Hydrothermal metamorphism - chemical alteration
  of preexisting rocks by hot seawater near
  seafloor spreading or subduction zones
• Fault metamorphism - occurs as rocks grinding
  past one another create a form of directed
  pressure, as well as considerable frictional heat
  
• Shock metamorphism - occurs when a meterorite
  strikes the Earth surface, resulting in
  tremendous pressures and temperatures at the
  impact sites. The shocked minerals do not
  fracture, but rather recrystallize

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Contact and Regional Metamorphism
Regional Metamorphism
Contact Metamorphism
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ROCK FORMING PROCESSES
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THE ROCK CYCLE