What alternatives are there to the plume hypothesis?

1
What alternatives are there to the plume
hypothesis?

• Helen Brown

2
Background!

• Great variability amongst hot spots
• Plume theory become progressively elaborate
• Question the hypothesis
• Investigate alternatives
• should account for what is observed
• and be scientifically testable

3
Meteorite Impacts

• Catastrophic mechanism
• Recognition shock related effects.
  Auto-obliterated?
• Pressure release or decompression melting
• Volume of melt comparable to LIP

4
Ridge Transform Intersections

• 3D finite element models

• Seamount formation

Consider effect of lithospheric stress on all
hotspots
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Plate Tectonic Processes

• Volcanic anomalies are by products of plate
  tectonics
• Unifies convection and volcanism
• 2 key requirements
• Intraplate Deformation
• Upper mantle is compositionally variable
• Location amount of melt

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Reheated Slabs

• Low velocity anomalies

• Do NOT resemble plumes
• Ancient slabs
• Velocity inversion
• Radioactive heat source
• Penetrative convection
• NO need for plumes!

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Lithospheric Delamination

• Explain continental volcanism
• 2 Conditions for delamination
• Gravitationally unstable
• Viscosity lowered
• How cause magmatism
• Astheno sucked into void
• Horizontal T gradients drive convection
• Dewatering

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Edge Driven Convection (EDC)

• Instability between thick, stable lithosphere and
  thinner lithosphere.
• Fixed boundaries, mantle mobile.
• EDC driven by vertical T variation along the
  edge

9
Conclusions

• Common themes
• Fertile mantle
• Lithospheric Extension
• Decompression melting
• Alternatives need further scientific
  investigation before they can truly challenge the
  long believed Plume Hypothesis