Chapter 2

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Chapter 2
2011-09-05 16:58:29
Geology Rocks Minerals

Earth Materials & Features
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  1. Rocks
    a collection of one or more minerals
  2. Minerals
    A collection of one or more elements (atoms).
  3. What makes up rocks & minerals?
    a granite <rock> is made of quartz +feldspar + biotite <minerals>. quartz <a mineral> = silicon + oxygen
  4. atom
    An atom is the smallest piece of matter that exists with unique chemical properties
  5. element
    An element describes different types of atoms
  6. Periodic table of the elements
    There are 112 known elements, but only 92 are naturally occurring.
  7. Ionic bond
    • Atom loses an electron from its outer shell to another atom. Ex:Halite
    • 1
  8. Covalent bonding
    electrons are shared, rather than exchanged between two atoms. Ex: Quartz

  9. Metallic Bonds
    atoms share clouds of electrons. Electrons in the outer shells drift from one atom to another as a result of close packing of the atoms. Ex:Gold
  10. Van der Waals Bonds
    a weak secondary bond between electrically neutral molecules (each have a + and - end). Ex:Graphite
  11. Atoms to Minerals
    Approximately 20 important rock forming minerals that fall into 6 groups
    • Silicate mineral
    • Carbonate mineral
    • Sulfate minerals
    • Halide minerals
    • Oxide minerals
    • Sulfide minerals
  12. Silicate mineral
    Has a silicate tetrahedron (SiO4) as the basic chemical property. Silicates are the dominant group in igneous, sedimentary, and metamorphic rocks.
  13. Carbonate mineral
    Have Ca, Mg, Fe (and others) attached to a carbonate ion (CO3-). They typically form in water and are important sedimentary rocks.
  14. Sulfate minerals
    Have Ca (and other) calcium ions attached to a sulfate ion (SO4-2). Most rock-forming sulfate minerals, such as gypsum and anhydrite, occur in due to evaporation (sedimentary).
  15. Halide minerals
    Have positive ions (Na, K) attached to negative ions (Cl, Br). Most rock-forming halides occur due to evaporation (salts) in sedimentary rocks.
  16. Oxide minerals
    Have metallic ions combined with oxygen. Usually economic minerals. Occur in igneous, sedimentary, and metamorphic rocks.
  17. Sulfide minerals
    Have metallic ions combined with sulfur. They occur in igneous, sedimentary, and metamorphic rocks.
  18. Rock Cycle
  19. Rocks on Earth have a varierty of origins:
    • Crystallization of magma (IGNEOUS)
    • Deposition of particles weathered and eroded from preexisting rocks (SEDIMENTARY)
    • Biologic precipitation (BIOMINERALIZATION)
    • Alteration of preexisting rocks(METAMORPHISM) Biomineralization in commenly considered a sed. process
  20. Sediment
    Unconsolidated particles of rock that have been transported by agents of erosion and unconsolidated particles formed as skeletal material through biominralization
  21. Sedimentary Rx. (from latin word sedimentum, "to settle")
    A rock, usually layerd, formed from sediments and from minerals precipitated under aqueous conditions
  22. Metamorphic Rx. (from Greek word meta, "change, " and morphe, "form."
    Rock whose original mineralogy or texture has been transformed though any combination of heat, pressure, chemical environment (inc. hydrothermal fluids), and shearing stress.
  23. Types of Rocks
    Descriptive classification
    Rx. organized according to their texture or fabric (size of grains or crystals, their packaging, etc.) and their compsition (quartz, feldspar, mica, clay, calcite, etc.)
  24. Genetic classification
    system or classification according to origin
  25. Igneous Rocks & Processes
    Intrusive (plutonic) rocks
    Ig. rx. usually coarsely crystalline (phaneritic), that resulted from the cooling and solidification of magma within Earth's crust. Ex:Granite, Diorite, Gabbro
  26. Extrusive (volcanic) rocks
    Ig.rx. usually finely crystalline (aphenitic), that resulted from cooling and solidification of magma erupted onto Earth's surface. Ex: Rhyolite, Andesite, Basalt
  27. extrusive rocks cont.
    • Rhyolite is formed of tuff-fine volcanic ash mixed with larger particles called lapilli.
    • Another term for ext.rx. is pyroclastic, refers to rx. formed by violent ejection of broken rock fragments from a volcano
  28. Obsidian (volcanic glass)
    forms when lava cools and solidifies rapidly.It is an amorphous or noncrystalline solid, aka mineraloid
  29. Common Igneous Rocks consist mostly of 6 minerals
    Quartz, feldspar, mica, amphibole, pyroxene, and olivine.
  30. Felsic
    • Light colored ig.rx.
    • dominated by Quartz, feldspar, and muscovite (potassium rich)mica. Ex. Granite & ryholite. form much of the continental crust
  31. Mafic & Ultramafic
    • Dark colored ig.rx.
    • dominated by biotite (a ferromagnesian, or Fe- and Mg- bearing) mica, amphibole, and pyroxene.
    • Mafic- basalt and gabbro
    • Ultramafic- peridotite
  32. Intermediate
    • midway between felsic and mafic
    • Ex: andesite, diorite
  33. Pluton
    An ig. rock body
  34. Batholith
    An irregularly shaped intrusive (plutonic) ig. rock body larger then 100 km2 and no known base.
  35. Stocks
    An irregularly shaped intrusive (plutonic) ig. rock body smaller then 100 km2.
  36. Pegmatites
    Unusually large crystals. Often containing desirable and rare elements as Be, B, and Li
  37. Dike
    Thin, tabular, sheet-like intrusive body that cuts across the layering or fabric of preexisting rocks.
  38. Sill
    a tabular, sheet-like intrusion that extends parallel to the layering or fabric of the rocks it intrudes.
  39. Laccolith
    extends parallel to the layering or fabric of preexisting rocks, but when it was emplaced, it caused the intruded rocks to bend upward into a dome.
  40. Sedimentary Rocks and Processes
    The process involving in changing sediments to rock.
  41. Siliclastic sediments
    the precursors of sed.rx., are particles (or clasts) composed of silicate minerals (notebly quartz, mica, and feldspar).
  42. Sedimentary grain sizes