Geology: Igneous Rocks and Placers
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Questions and Answers

What is the primary cause of the reorganization of atoms in minerals during the formation of metamorphic rocks?

  • Heat (correct)
  • Chemical reactions
  • Water content
  • Pressure
  • Which of the following factors is NOT involved in the metamorphism of rocks?

  • Time
  • Chemical alteration
  • Weathering (correct)
  • Pressure
  • What are the two main textures observed in metamorphic rocks?

  • Coarse and fine
  • Crystalline and amorphous
  • Foliated and non-foliated (correct)
  • Layered and non-layered
  • Which type of fluids primarily contribute to chemical reactions during the metamorphism of rocks?

    <p>Water with dissolved ions</p> Signup and view all the answers

    Which statement about the hardness of metamorphic rocks is correct?

    <p>They are generally harder than their parent rocks.</p> Signup and view all the answers

    How does the duration of exposure to heat and pressure affect the metamorphic transformation?

    <p>The transformation becomes more pronounced.</p> Signup and view all the answers

    What determines the mineral composition of metamorphic rocks?

    <p>Parent rock and conditions of metamorphism</p> Signup and view all the answers

    What role does pressure play in the metamorphic process?

    <p>It causes deformation and reorientation of minerals.</p> Signup and view all the answers

    Which process leads to the concentration of heavier minerals such as gold and platinum?

    <p>Mechanical concentration by water currents</p> Signup and view all the answers

    What type of igneous rock forms as lava cools on the Earth's surface?

    <p>Volcanic igneous rock</p> Signup and view all the answers

    What characterizes plutonic (or intrusive) igneous rocks?

    <p>They have a coarse crystalline texture</p> Signup and view all the answers

    Which of the following is NOT a process involved in the formation of igneous rocks?

    <p>Consolidation of sediments</p> Signup and view all the answers

    How does slow cooling affect the crystal structure of igneous rocks?

    <p>Creates large, visible crystals</p> Signup and view all the answers

    What happens to lighter particles during the mechanical concentration of minerals?

    <p>They are carried away by water currents</p> Signup and view all the answers

    Which of the following is an example of a plutonic igneous rock?

    <p>Granite</p> Signup and view all the answers

    What is the primary origin of igneous rocks?

    <p>Cooling of molten material</p> Signup and view all the answers

    What is the primary process involved in the formation of igneous rocks?

    <p>Cooling and crystallization of magma</p> Signup and view all the answers

    Which method is NOT associated with the formation of metamorphic rocks?

    <p>Cooling of magma</p> Signup and view all the answers

    What distinguishes metamorphic rocks from igneous rocks?

    <p>They result from recrystallization of existing rocks</p> Signup and view all the answers

    Which of the following conditions does NOT typically lead to the formation of metamorphic rocks?

    <p>Low pressure</p> Signup and view all the answers

    Which statement accurately describes both igneous and metamorphic rocks?

    <p>Both involve the transformation of pre-existing materials</p> Signup and view all the answers

    Which types of rocks are primarily found in the earth's crust?

    <p>Igneous rocks</p> Signup and view all the answers

    What is the primary component of rocks?

    <p>Minerals</p> Signup and view all the answers

    Which characteristic would NOT typically be used to classify rock samples?

    <p>Weight</p> Signup and view all the answers

    Which rock types are considered igneous?

    <p>Granite and basalt</p> Signup and view all the answers

    What grouping method might be used to classify rock samples?

    <p>Composition of minerals</p> Signup and view all the answers

    Which of these is NOT a type of rock mentioned in the content?

    <p>Shale</p> Signup and view all the answers

    What is the main function of rocks in the earth's crust?

    <p>To form the foundational layer of the earth</p> Signup and view all the answers

    When classifying rocks, which feature would likely be considered?

    <p>Their mineral composition</p> Signup and view all the answers

    What is a mineral deposit?

    <p>A concentration of a mineral that is scientifically or technologically important.</p> Signup and view all the answers

    What characterizes an ore deposit from a mineral deposit?

    <p>It must have been tested and determined to be economically viable for mining.</p> Signup and view all the answers

    Which type of ore deposit is formed from elements once dispersed in magma?

    <p>Magmatic Ore Deposits</p> Signup and view all the answers

    What is typically needed for a mineral deposit to be considered economically viable?

    <p>A favorable economic environment for extraction.</p> Signup and view all the answers

    Which of the following is NOT a characteristic of an ore deposit?

    <p>Located exclusively in mountainous regions.</p> Signup and view all the answers

    The extraction of which type of mineral resources often involves open-pit mining?

    <p>Coal Deposits</p> Signup and view all the answers

    What does the term 'mineral occurrence' refer to?

    <p>Any presence of minerals without regard to concentration.</p> Signup and view all the answers

    Which factor is critical in determining whether a mineral deposit is mined?

    <p>The economic conditions surrounding the deposit.</p> Signup and view all the answers

    Study Notes

    Placers

    • Are made up of minerals that have been separated from rocks by weathering and then concentrated by gravity
    • Heavier minerals like gold, platinum, diamonds, and tin are mechanically concentrated by water currents
    • Lighter particles are carried away by water currents

    Igneous Rocks

    • Formed from the cooling of molten material such as magma, lava, and pyroclastics
    • The development of Igneous rocks creates uplift exposing them to weathering and erosion
    • Igneous rocks are classified into two groups
      • Volcanic (Extrusive) Igneous Rocks - form on Earth's surface as lava cools
      • Plutonic (or Intrusive) Igneous Rocks - form deep underground where magma cools slowly creating coarse crystalline texture

    Formation of Igneous Rocks

    • Slow cooling of magma creates large crystals that are visible to the naked eye
      • Examples: granite, diorite, syenite
    • Rapid cooling of magma creates minimal mineral crystals that are not visible to the naked eye
      • Examples: chalk, coal, diatomite, some dolomites, and some limestones

    Metamorphic Rocks

    • Rocks that have been changed in form due to heat, pressure, and chemical alteration.
    • Metamorphism: pressure and temperature dictate a rock’s new properties

    Formation of Metamorphic Rocks

    • Heat: energy reorganizes atoms in minerals leading to the formation of new minerals
    • Pressure: causes deformation and reorientation of minerals
    • Chemically Active Fluids: fluids particularly water with dissolved ions cause chemical reactions altering rock composition
    • Time: the longer a rock is exposed to heat and pressure, the more pronounced the metamorphic transformation

    Properties of Metamorphic Rocks

    • Texture: Can be foliated (layered) or non-foliated
    • Hardness: Generally harder than their parent rock
    • Mineral Composition: Varies depending on the parent rock and the conditions of metamorphism

    The Earth’s Crust

    • Composed of rocks that are primarily composed of minerals but may also contain organic materials
    • The granite and basalt rocks of the continental and oceanic crusts were the original, igneous rocks

    Rock Cycle

    • Igneous Rocks: form due to the cooling and crystallization of magma
    • Sedimentary Rocks: form from the accumulation and cementation of sediments
    • Metamorphic Rocks: rocks are recrystallized due to heat, pressure, and chemical alteration

    Mineral Deposits and Their Formation

    • Mineral Occurrence: concentration of a mineral that is of scientific or technological importance
    • Mineral Deposit: a mineral occurrence large enough in size and grade to enable extraction under favorable conditions
    • Ore Deposit: a mineral deposit that has undergone testing and has been determined to be economically viable for mining

    Mineral Resources and Their Origin

    • Magmatic Ore Deposits: elements once dispersed in magma accumulate and enrich, forming ore minerals

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    Description

    Explore the fascinating world of igneous rocks and placers in this quiz. Learn how these geological formations are created, the classification of igneous rocks, and the processes that result in the concentration of minerals. Test your knowledge on the formation and characteristics of these essential earth materials.

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