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Seismic and geochemical correlations at hotspots J.G. Konter, T.W. Becker

Seismic and geochemical correlations at hotspots J.G. Konter, T.W. Becker. Konter and Becker, 2012. Outline. Visual (map) correlations at hotspots Correlating actual numbers: Hotspot locations and observations Observations at hotspots: geophysical, geochemical

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Seismic and geochemical correlations at hotspots J.G. Konter, T.W. Becker

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  1. Seismic and geochemical correlations at hotspots J.G. Konter, T.W. Becker Konter and Becker, 2012

  2. Outline • Visual (map) correlations at hotspots • Correlating actual numbers: • Hotspot locations and observations • Observations at hotspots: geophysical, geochemical • Bottom line: only some things correlate significantly

  3. Mantle Models Geochemically: Where to store materials (noble gas, EER, …)? Combine with geophysical observations Tackley, 2000

  4. Geographical anomalies “Dupal” hotspots located in the S hemisphere: Dupal = isotopically enriched by recycling (EM1, EM2) Hart, 1984

  5. Simplest correlations “Dupal” hotspots plot on top of seismically slow areas => Correlation significance? Castillo, 1988

  6. Gradients ? Locations seem to fit gradients => for same CMB area, gradients have ~2x more hotspots Thorne et al., 2004

  7. Adding LIPs - gradients Hotspot correlations done by several groups Gradients seem important Original eruptive locations LIPs “align” with hotspots Torsvik et al., 2006

  8. Mathematical correlations Vertical correlations hotspot-seismic less significant than tilted conduits Boschi et al, 2008

  9. Including geochemistry Besides location, does geochemistry correlate? Raw ratios (PCA) or “end-members” Use: Sr-Nd-Pb isotope data radiate out from FOZO/C to define “mantle tetrahedron” W. White

  10. Isotope space Konter et al., 2008 For end-members, define measure of distance: distance from center (FOZO/C) to end-member

  11. Independent components Contrary to PCA, underlying distribution can be non-gaussian Separates MORB from OIB Iwamori and Albarède, 2008

  12. Correlations - Only few significant Konter and Becker, 2012 Significant: depth –EM1,2,HIMU EM1 –Vs-200 EM2 – Vs-CMB C – Vs-200 Potential temp. – C NOTE: no correlation for gradients

  13. Significance of Correlations Konter and Becker, 2012 Monte Carlo: randomize locations vs composition: EM1 and C/FOZO best, plume depth close for all

  14. Actual correlations Konter and Becker, 2012 EM1 (anti)correlates well with depth, Vs-200km Anti-correlation C/FOZO with Vs-200km

  15. Atlantic EM1 S. American/African continental lavas with overlapping compositions; source in lithosphere? Particularly S. America argued as source by multiple groups Hawkesworth et al., 1986

  16. Atlantic EM1 Return flow in mantle delivers EM1; direct hotspot track/APM does not fit (same authors put EM1 back in plume in 2010) Class and Le Roex, 2006

  17. EM1 origin EM1 combination of deep source with shallow influence: mixing in lithosphere works, but requires >50% Konter and Becker, 2012

  18. Explanation EM1 Combination of conduit vs tomography, shallow pollution of deep source Konter and Becker, 2012

  19. Explanation C/FOZO Anti-correlation C/FOZO vs Vs-200km: Compositions present in ~ all hotspots, shallow correlation is not Anti-correlation from larger degree melt (enriched trace elements suggested by isotopes) Main issue: He isotopes most characteristics, but not available

  20. So correlations? Some correlations with some of the geochemical parameters, but many observables do not correlate at hotspots Even so, what do the correlations mean?

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