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MINERALS AND ROCKS IN THE EARTH’S CRUST

MINERALS AND ROCKS IN THE EARTH’S CRUST. Igneous, Sedimentary, Metamorphic Rocks and Environments. MINERALS AND ROCKS COME FROM ELEMENTS. Chemical elements are the fundamental materials of which all matter is composed. From the modern viewpoint:

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MINERALS AND ROCKS IN THE EARTH’S CRUST

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  1. MINERALS AND ROCKS IN THE EARTH’S CRUST Igneous, Sedimentary, Metamorphic Rocks and Environments

  2. 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

  3. 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

  4. 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

  5. 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)

  6. NON-SILICATE MINERALS • Non-silicate minerals are very rare • Make up 5% of Earth’s 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)

  7. SILICATE MINERALS • THE MOST ABUNDANT OF ALL MINERALS • MAKE UP APPROXIMATELY 95% OF WEIGHT OF EARTH’S CRUST • CONTAIN VARYING AMOUNTS OF SILICA (SiO) • DOMINANT COMPONENT OF MOST ROCKS: • IGNEOUS • SEDIMENTARY • METAMORPHIC

  8. SILICATE MINERALS • LISTED BELOW IN DECREASING % OF SILICA ARE MOST COMMON SILICATE MINERALS • QUARTZ (SiO2) (“High” Silica content ~100%) • FELDSPARS (PLAGIOCLASE - • MICAS (MUSCOVITE – BIOTITE ) • AMPHIBOLES (Hornblende) • PYROXENES (Augite) • OLIVINE (“Low” Silica content ~40%)

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

  10. 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

  11. QUARTZ FELDSPAR MUSCOVITE MICA

  12. 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)

  13. BIOTITE MICA PYROXENE (AUGITE) AMPHIBOLE (HORNBLENDE)

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

  15. WHAT ARE ROCKS? • AGGREGATIONS OF 2 OR MORE MINERALS • Same or different minerals combine together • THREE CATEGORIES • IGNEOUS • SEDIMENTARY • METAMORPHIC

  16. IGNEOUS ROCKS • Ignis: Latin for “Fire” • FORMED FROM MOLTEN MATERIAL THAT COOLED AND SOLIDIFIED 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

  17. 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)

  18. 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’

  19. TEXTURE IDENTIFICATION Fine-Grained Textures Coarse-Grained Textures

  20. MINERAL COMPOSITION • CLASSIFIED BY SILICA (SiO) CONTENT • FELSIC – MORE THAN 85% SILICA • INTERMEDIATE – 60-85% SILICA • MAFIC – LESS THAN 60% SILICA

  21. COMMON IGNEOUS ROCKS • FELSIC IGNEOUS ROCKS (>85% SiO) • GRANITE: • PLUTONIC-INTRUSIVE; COARSE-GRAINED TEXTURE; FELSIC MINERAL COMPOSITION • RHYOLITE: • VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; FELSIC MINERAL COMPOSITION • INTERMEDIATE IGNEOUS ROCKS (60-85% SiO) • DIORITE: • PLUTONIC-INTRUSIVE; COARSE-GRAINED TEXTURE; INTERMEDIATE MINERAL COMPOSITION • ANDESITE: • VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; INTERMEDIATE MINERAL COMPOSITION • MAFIC IGNEOUS ROCKS (<60% SiO) • GABBRO: • PLUTONIC-INTRUSIVE;COARSE-GRAINED TEXTURE; MAFIC MINERAL COMPOSITION • BASALT: • VOLCANIC-EXTRUSIVE; FINE-GRAINED TEXTURE; MAFIC MINERAL COMPOSITION

  22. IGNEOUS ROCK IDENTIFICATION CHART Granitic Andesitic Basaltic (Felsic) (Intermediate) (Mafic) Coarse-Grained Granite Diorite Gabbro Fine-Grained Rhyolite Andesite Basalt Rock color Light-colored Medium-colored Dark grayblackbased on % <15% mafic 15-40% mafic >40% mafic mafic minerals minerals minerals minerals Viscosity Highest Medium Low Melting Temps 600-8000 C 800-11000 C 1 100-12000 C

  23. FELSIC IGNEOUS ROCKS RHYOLITE VOLCANIC-EXTRUSIVE PLUTONIC-INTRUSIVE GRANITE

  24. INTERMEDIATE IGNEOUS ROCKS VOLCANIC-EXTRUSIVE ANDESITE DIORITE PLUTONIC-INTRUSIVE

  25. MAFIC IGNEOUS ROCKS PLUTONIC-INTRUSIVE GABBRO BASALT VOLCANIC-EXTRUSIVE

  26. 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

  27. VOLCANIC GLASS OBSIDIAN PUMICE

  28. PYROCLASTIC IGNEOUS ROCKS WELDED TUFF

  29. SEDIMENTARY ROCKS • WEATHERING PROCESSES BREAK ROCK INTO PIECES, SEDIMENT. • HOW SEDIMENTATION HAPPENS : • TRANSPORTATION DEPOSITION BURIAL AND LITHIFICATION INTO NEW ROCKS.

  30. 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.

  31. CLASSIFYING SEDIMENTARY ROCKS • THREE SOURCES FOR SEDIMENTARY ROCKS • (1) Detrital (or clastic) sediment is composed of transported solid fragments (or detritus) of pre-existing igneous, sedimentary or metamorphic rocks • (2) Chemical sediment forms from previously dissolved minerals that either precipitated from solution in water, or were extracted from water by living organisms • (3) Organic sedimentary rock consisting mainly of plant remains

  32. CLASTIC/DETRITAL SEDIMENTARY ROCKS • CLASSIFIED ON GRAIN OR PARTICLE SIZE • Shales: finest-grained • Sandstones: medium-grained • Conglomerates – Breccias: coarse-grained

  33. SHALES : CLASTIC SEDIMENTARY • SHALES: finest-grained clastic sedimentary rocks – composed of very small particles • 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

  34. SHALES Burgess Shale in Canada Limestone on black shale

  35. MUDSTONES, SILTSTONES Identified by decreasing amounts of sand and increasing amounts of clay

  36. SANDSTONES • SANDSTONES: medium-grained clastic sedimentary rocks • 25% of all sedimentary rocks fall into this category • Economic value: glass; natural reservoirs for oil, gas, and groundwater

  37. SANDSTONES

  38. CONGLOMERATES - BRECCIAS • CONGLOMERATESAND BRECCIAS: • The coarsest of all the clastic sedimentary rocks • Composed of particles >2 mm in diameter • Conglomerate - the particles are rounded • Breccia - the particles are angular

  39. CONGLOMERATES

  40. BRECCIAS

  41. CHEMICAL SEDIMENTARY ROCKS • TWO CATEGORIES: • INORGANIC CHEMICAL SEDIMENTARY • ORGANIC CHEMICAL SEDIMENTARY

  42. 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

  43. 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

  44. LIMESTONES TRAVERTINE

  45. Tufa Towers, Mono Lake

  46. 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

  47. COQUINA, CHALK AND FOSSILIFEROUS LIMESTONES COQUINA FOSSILIFEROUS LIMESTONE CHALK

  48. 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.

  49. COAL PEAT LIGNITE ANTHRACITE BITUMINOUS

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