MINERALS AND ROCKS

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MINERALS AND ROCKS
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PERIODIC TABLE OF ELEMENTS




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ELEMENTS

• EIGHT ELEMENTS MAKE UP MOST OF ALL MINERALS ON
  THE EARTH
• Elements combine to form Minerals
• LISTED IN ORDER OF ABUNDANCE
• OXYGEN (O)
• SILICON (Si)
• ALUMINIUM (Al)
• IRON (Fe)
• CALCIUM (Ca)
• POTASSIUM (K)
• SODIUM (Na)
• MAGNESIUM (Mg)

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MINERALS

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

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MINERALS

• MINERALS TWO CATEGORIES
• SILICATES CONTAIN SILICON - OXYGEN MOLECULE
  (SiO)
• NON-SILICATES (NO SiO)

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NON-SILICATE MINERALS

• Make up 5 of Earths continental crust
• Native metals gold, silver, copper
• Carbonates calcite (used in cement)
• Oxides hematite (iron ores)
• Sulfides galena (lead ores)
• Sulfates gypsum (used in plaster)

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SILICATE MINERALS

• MAKE UP 90-95 OF WEIGHT OF EARTHS CRUST
• DOMINANT COMPONENT OF MOST ROCKS
• IGNEOUS
• SEDIMENTARY
• METAMORPHIC

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SILICATE MINERALS

• QUARTZ (SiO2)
• FELDSPARS (PLAGIOCLASE - (Na,Ca)(Si,Al)4O8 )
• MICAS (MUSCOVITE -KAl2(AlSi3O10)(F, OH)2,
  BIOTITE - K (Fe, Mg)3 AlSi3 O10 (F, OH)2 )
• AMPHIBOLES (Hornblende -Ca2(Fe,Mg)5Si8O22(OH2)
• PYROXENES (Augite Mg,FeSiO3)
• OLIVINE - (Mg, Fe)2SiO4,

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FELSIC SILICATE MINERALS

• FELSIC SILICATES HIGH SiO
• QUARTZ (100 SiO2)
• FELDSPARS
• MUSCOVITE MICA

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MAFIC SILICATE MINERALS

• MAFIC SILICATES - LESS SiO
• BIOTITE MICA
• AMPHIBOLE
• PYROXENE

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ULTRAMAFIC SILICATES

• ULTRA MAFIC SILICATES - VERY LOW SiO
• VERY RARE AT SURFACE
• OLIVINE

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ROCKS

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

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IGNEOUS ROCKS

• FORMED FROM COOLED, SOLIDIFIED MOLTEN MATERIAL,
  AT OR BELOW THE SURFACE
• PLUTONIC INTRUSIVE COOLED BELOW SURFACE AT
  GREAT DEPTHS
• VOLCANIC EXTRUSIVE COOLED AT OR NEAR THE
  SURFACE THROUGH VOLCANIC ERUPTIONS

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IDENTIFICATION OF IGNEOUS ROCKS

• IDENTIFICATION PROCESSES
• TEXTURE
• Size, shape and manner of growth of individual
  crystals
• MINERAL COMPOSITION
• Based on SiO content
• Felsic, Intermediate, Mafic

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TEXTURE IDENTIFICATION

• SIZE, SHAPE OF CRYSTALS AND MANNER OF GROWTH
• APHANETIC TEXTURE
• FINE-GRAINED VERY TINY, MINERAL CRYSTALS
  VISIBLE ONLY WITH MAGNIFICATION
• INDICATES FAST COOLING AT SURFACE
• PHANERITIC TEXTURE
• COARSE-GRAINED LARGE, EASILY-VISIBLE MINERAL
  CRYSTALS
• INDICATES SLOW COOLING AT DEPTH

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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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COMMON IGNEOUS ROCKS

• GRANITE PLUTONIC-INTRUSIVE PHANERITIC TEXTURE
  FELSIC MINERAL COMPOSITION
• RHYOLITE VOLCANIC-EXTRUSIVE APHANETIC TEXTURE
  FELSIC MINERAL COMPOSITION
• DIORITE PLUTONIC-INTRUSIVE PHANERITIC TEXTURE
  INTERMEDIATE MINERAL COMPOSITION
• ANDESITE VOLCANIC-EXTRUSIVE APHANETIC TEXTURE
  INTERMEDIATE MINERAL COMPOSITION
• GABBRO PLUTONIC-INTRUSIVE PHANERITIC TEXTURE
  MAFIC MINERAL COMPSITION
• BASALT VOLCANIC-EXTRUSIVE APHANETIC TEXTURE
  MAFIC MINERAL COMPOSITION

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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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SEDIMENTARY ROCKS

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

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CLASSIFYING SEDIMENTARY ROCKS

• THREE SOURCES
• 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 SEDIMENTARY ROCKS

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

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SHALES

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

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SANDSTONES

• SANDSTONES medium-grained particle-size
  (0.063-2 mm)
• 25 of all sedimentary rocks fall into this
  category
• Three major kinds of Sandstone, based on mineral
  composition and appearance
• Quartz Arenite gt90 quartz grains
• Arkoses more Feldspar minerals
• Graywackes quartz and feldspar grains, and
  volcanics
• Economic value glass natural reservoirs for
  oil, gas, and groundwater

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CONGLOMERATES - BRECCIAS

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

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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 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

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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 Organic Chert

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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.
• 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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SEDIMENTARY ENVIRONMENTS

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

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SEDIMENTARY PROCESSES

• LITHIFICATION
• As sediment is buried several kilometers beneath
  the surface, heated from below, pressure from
  overlying layers 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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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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METAMORPHISM

• HEAT Temperatures needed to metamorphose rock
  (2000 C or 10000 C) reached near 10 km (6 miles)
  beneath the surface.
• PRESSURE Requires pressure gt 1 bar or 1000 mb,
  which is generally found 3 km (2 miles) beneath
  the Earths surface
• FLUIDS Water is the usual fluid and comes from
  various sources

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CHANGES IN METAMORPHIC ROCKS

• Metamorphic processes cause many changes in rocks
  
• increased density
• growth of larger crystals
• reorientation of the mineral grains into layers
  or banded texture
• FOLIATION
• 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 (200-4000C) and low pressures (from
  1-6 kilobars)
• Intermediate grade (300-6000 c) occurs at a
  variety of temperatures and pressures.
• High grade at higher temperatures (600-10000C)
  and at pressures of 12-15 kilobars

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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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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 form under Intermediate-Grade
  Metamorphism
• Schists named for the mineral constituents in the
  parent rock
• mica schist
• talc schist
• garnet 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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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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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
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GEOLOGIC TIME AND DATING

• Four basic principles
• Principle of Original Horizontality
• Beds of sediment deposited in water formed as
  horizontal or nearly horizontal layers.
• Principle of Superposition
• Within a sequence of undisturbed sedimentary or
  volcanic rocks, the layers get younger going from
  bottom to top.
• Lateral Continuity
• An original sedimentary layer extends laterally
  until it tapers or thins at its edges
• Cross-cutting Relationships
• A disrupted pattern is older than the cause of
  the disruption.

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DATING - RELATIVE

• Physical Continuity
• Physically tracing the course of a rock unit to
  correlate rocks between two different places
• Similarity of Rock Types
• Correlation of two regions by assumption that
  similar rock types in two regions formed at same
  time, under same circumstances
• Correlation by Fossils
• Plants and animals that lived at the time rock
  formed were buried by sediment
• fossil remains preserved in the layers of
  sedimentary rock -fossils nearer the bottom (in
  older rock) are more unlike -those near the top
• Observations formalized into Principle of Faunal
  Succession fossil species succeed one another
  in a definite and recognizable order.
• Index Fossil a fossil from a short-lived,
  geographically widespread species known to exist
  during a specific period of geologic time.

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ABSOLUTE DATING - DENDROCHRONOLGY

• Using annual growth rings of trees
• Dates for trees now extending back more than
  9,000 years.
• Bristlecone Pine, White Mountains, CA (pinus
  longaeva) provides a continuous time scale for
  last 9,000 years (to 7000 B.C)
• Provides calibration of radiocarbon dates over
  most of the last 10,000 years (Holocene epoch)

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DENDROCHRONOLOGY
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ABSOLUTE DATINGVARVE CHRONOLOGY

• Varves are parallel strata deposited in deep
  ocean floors or lake floors
• A pair of sedimentary layers are deposited during
  seasonal cycle of a single year
• Laminae (similar to annual growth rings in trees)
  record climatic conditions in a lake or large
  water body from year to year
• Cores extracted from sea floor or lake floor are
  used to date back several million years to 200
  million years

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VARVE CHRONOLOGY
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DATING - ABSOLUTE

• Radiometric dating based on radioactive decay
  of isotopes
• Decay rate can be quantified because it occurs at
  a constant rate for each known isotope
  half-life from parent isotope to stable
  daughter isotope
• Measuring ratio of parent to daughter isotopes
  determines absolute ages of some rocks.

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ABSOLUTE DATING ISOTOPES

• URANIUMLEAD (U238Pb206)
• Half-life 4.5 billion years
• Dating range 10 million 4.6 billion years
• URANIUMLEAD (U235-Pb207)
• Half-life 713 million years
• Dating Range 10 million 4.6 billion years
• POTASSIUM-ARGON (K40-Ar40)
• Half-life 1.3 billion years
• Dating Range 100,000 4.6 billion years
• CARBON-14 (C14-N14)
• Half-life 5730 years
• Dating Range 100 100,000 years

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