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Radiogenic isotopes

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Radiogenic isotopes. Isotopes. Same number of protons, different number of ... The U-Pb-Th System. Concordia = Simultaneous co-evolution of 206Pb and 207Pb via: ... – PowerPoint PPT presentation

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Title: Radiogenic isotopes


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Radiogenic isotopes
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Isotopes
  • Same number of protons, different number of
    neutrons (same atomic number, different atomic
    masses)
  • Same chemical properties
  • but different masses
  • Chemical etc. processes fraction only slightly
    isotopes (mostly the lights)

3
  • Stable isotopes
  • See GEOL214
  • Used largely for surface processes, some use as
    magmatic tracers
  • Unstable isotopes
  • Parent -gt daughter
  • Used for dating
  • Tracers of sources

4
Isotopic systems
  • Used for dating
  • K-Ar
  • Rb-Sr
  • Sm-Nd
  • U-Pb (and Pb-Pb, and more)
  • Used as tracers
  • Sm-Nd
  • Rb-Sr
  • Pb-Pb
  • Lu-Hf
  • Re-Os

See G.214
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The U-Pb-Th System
Concordia Simultaneous co-evolution of 206Pb
and 207Pb via 238U ? 234U ? 206Pb 235U ? 207Pb
Figure 9-16a. After Faure (1986). Principles of
Isotope Geology. 2nd, ed. John Wiley Sons. New
York.
8
The U-Pb-Th System
Discordia loss of both 206Pb and 207Pb
Figure 9-16a. After Faure (1986). Principles of
Isotope Geology. 2nd, ed. John Wiley Sons. New
York.
9
The U-Pb-Th System
Concordia diagram after 3.5 Ga total evolution
Figure 9-16b. After Faure (1986). Principles of
Isotope Geology. 2nd, ed. John Wiley Sons. NY
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