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Arcs & continents

Arcs & continents. Updates/questions. Wednesday review, midterm on April 2nd Topics: Systematics for: Arcs Some continental rocks. Trace Elements: REEs. Enriched. Depleted. Figure 14-2. After Wilson (1989) Igneous Petrogenesis. Kluwer. MORB-normalized Spider Diagrams.

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Arcs & continents

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  1. Arcs & continents

  2. Updates/questions • Wednesday review, midterm on April 2nd • Topics: • Systematics for: • Arcs • Some continental rocks

  3. Trace Elements: REEs Enriched Depleted Figure 14-2. After Wilson (1989) Igneous Petrogenesis. Kluwer.

  4. MORB-normalized Spider Diagrams Figure 14-3. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Data from Sun and McDonough (1989).

  5. Trace Elements

  6. Isotope Geochemistry • Isotopes do not fractionate during partial melting of fractional melting processes, so will reflect the characteristics of the source • OIBs only cross oceanic plate, limiting contamination (<-> continent); good estimate of mantle

  7. Sr Isotope Evolution Figure 9-13. After Wilson (1989). Igneous Petrogenesis. Unwin Hyman/Kluwer.

  8. Sm-Nd: Evolution opposite to Rb - Sr Ctl Crust (enriched) = hi 87Sr/86Sr, lo 143Nd/144Nd 147Sm143Nd by alpha decay half life 106 Ga Daughter more incompatible • 143Nd/144Nd = (143Nd/144Nd)o + (147Sm/144Nd)(elt-1)

  9. MORB Sr - Nd Isotopes Figure 13-12. Data from Ito et al. (1987) Chemical Geology, 62, 157-176; and LeRoex et al. (1983) J. Petrol., 24, 267-318.

  10. MORB+OIB: Sr - Nd Isotopes Range in compositions = mantle array Every composition by mixing end-members: DM -depleted mantle EM 1&2 - enriched mantle HIMU - high m = 238U/204Pb 238U -> 206Pb So high 206Pb/204Pb DM MORB } OIB (colors) HIMU BSE EM2 EM1

  11. A Model for Oceanic Magmatism Continental Reservoirs DM OIB EM and HIMU from crustal sources (subducted OC + CC seds) Figure 14-10. Nomenclature from Zindler and Hart (1986). After Wilson (1989) and Rollinson (1993).

  12. Arc Magmatism Volcanism in arc-shaped region of volcanoes Different because: Composition more diverse and silicic Basalt generally occurs in subordinate quantities Also more explosive than the quiescent basalts Strato-volcanoes are the most common volcanic landform Result of subduction: H2O melting

  13. Arc occurrence

  14. Structure of an Island Arc

  15. Major Elements and Magma Series

  16. A multi-stage, multi-source process NOAA Ocean Explorer

  17. Continental Arcs

  18. Andes arc: north, central, south

  19. Andes trace elements

  20. Granitoid Rocks

  21. Types of granites

  22. Melting and composition

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