Arcs & continents
Download
1 / 22

Arcs & continents - PowerPoint PPT Presentation


  • 86 Views
  • Uploaded on

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.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Arcs & continents' - maude


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Updates/questions

  • Wednesday review, midterm on April 2nd

  • Topics:

  • Systematics for:

    • Arcs

    • Some continental rocks


Trace elements rees
Trace Elements: REEs

Enriched

Depleted

Figure 14-2. After Wilson (1989) Igneous Petrogenesis. Kluwer.


Morb normalized spider diagrams
MORB-normalized Spider Diagrams

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



Isotope geochemistry
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


Sr isotope evolution
Sr Isotope Evolution

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


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)


Morb sr nd isotopes
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.


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


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).


Arc magmatism

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












ad