Petrology and Ore Deposits Course 10179 Week 3

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Petrology and Ore DepositsCourse 10179Week 3

• Ch 7 - Petrology of the mantle
• Ch 9 - Igneous rocks of the oceanic lithosphere

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Ch 7 - Petrology of the Mantle

• Basalts originate from the mantle but our
  knowledge of the interior of the Earth is very
  limited because of physical inaccessibility

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Gross Vertical Structure of the Interior

• Crust
• Upper mantle
• Transition zone
• Lower mantle
• Outer core
• Inner core

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Gross Vertical Structure of the Interior

• Lithosphere
• Asthenosphere

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Physical Characteristics of the Mantle

• Horizontal Density Heterogeneity
• Seismic tomography
• http//www.seismo.unr.edu/ftp/pub/louie/class/100/
  interior.html
• http//www.uiggm.nsc.ru/homepages/geophysics/ris/
  

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Physical Characteristics of the Mantle

• Temperature Distribution

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Mantle Convection
Fig 7-4
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Chemistry and Mineralogy of the Mantle and Core

• Meteorites
• Xenoliths and xenocrysts
• Experimental petrology

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Estimates of Mantle Chemistry
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Mantle Petrology
Melting
Solidus
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Melt Formation
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Ch 7 - Study Exercises

• 1. Our knowledge of the composition and structure
  of the mantle is based on both direct and
  indirect (remotely sensed) observation, combined
  with modeling and experimental simulation. How
  deep in the upper mantle does our direct
  observational database extend? What does this
  database consist of?
• 2. The perovskite crystal structure is of great
  interest to geophysicists. Why is this crystal
  structure so relevant to magnesium silicate phase
  transitions in the upper mantle?
• 3. "Seismic tomography" of the mantle shows
  significant lateral variations in seismic
  velocity that have been linked to lateral
  compositional or thermal variations. What
  influence would these variations have on
  generation and ascent of basaltic magmas?
• 4. Why do xenolith-bearing basalts typically show
  much less diversity of xenolith rock types than
  kimberlites show?
• 5. Discuss petrologic explanations for the
  physical properties and mechanical behavior of
  the asthenosphere (1ow-velocity zone).

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Ch 8 Igneous Rocks of the Oceanic Lithosphere
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The Nature of Mid-ocean Ridges
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The Nature of Mid-ocean Ridges
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MOR Magma Heterogeneities
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Ophiolite Stratigraphy
The Ophiolite Model
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Geochemistry of MORBs
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Fractionation Trends of MORBs
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Petrogenesis of Seafloor Basalts
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Ocean Island Basalts (OIBs)
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Chemical and Mineralogical Characteristics of
Ocean Island Rocks
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Petrogenesis of Ocean Island Magmas
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Ch 8 - Study Exercises

• 1. Is the discovery of "smokers - that is, vents
  for mineral-rich hydrothermal waters on mid-ocean
  ridges consistent with the incipient alteration
  of seafloor basalts that is commonly observed in
  dredge samples? If so, how?
• 2. Summarize the chemical distinctions between
  NMORB and E-MORB, and relate these to the
  genesis of each type of magma.
• 3. How does the petrogenesis of MORB magmas
  differ from that of OIB magmas? Do their
  differing chemistries relate more to different
  depths of origin in the mantle or to fundamental
  chemical contrasts in their mantle source areas?
• 4. Are hot spots limited to oceanic lithosphere?
  Is there any petrologic or tectonic reason why
  they should or should not be?
• 5. OIB magmas are considerably more diverse
  chemically than MORB magmas. Is the great
  compositional range of OIB magmas related more
  closely to (a) chemical evolution of a common,
  mantle-derived parental magma for the suite, or
  (1)) complex melting of compositionally
  heterogeneous mantle over a range of depths?