Download Synthesis - Do plumes exist?

Synthesis
Gillian R. Foulger
Post-meeting books?
1. Book of review articles
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Chemical Geology (Elsevier)
2. AGU monograph
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Book of regular papers
Everyone is invited to contribute to
www.mantleplumes.org
Key points 1
1. Alternatives do not amount to a single,
generic, one-size fits all replacement
model for plume
–
generic elements, but each locality individual,
e.g., OJP, Hawaii, Azores
Key points 2
•
Consistent terminology imperative
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Use of properly defined/explained terms.
It isn’t enough to just say “plume”
Problem of falsification
Key points 3
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~ 1,000-km-wide magmatism - predicted by
both?
Time-progressive track - predicted by both?
Uplift. Domal? - complex pattern predicted by
both?
Temperature - necessary?
CMB origin - detectable?
Key points 4
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Opinion of relationship between plate
tectonics & plumes.
Key points 5
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Problems with publications:
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Standard of interpretations (cart before horse)
Repetition of old, wrong data e.g. ages,
temperatures.
Important problems 1
• Mantle physics
– Self-consistent models that
can produce plate tectonics
required.
– Better understanding of
critical mantle physical
parameters, e.g. CMB heat
flow, LM viscosity
– How important is smallscale convection?
• Lithosphere physics
– Behaviour of lithosphere
when major thermal event
occurs - plume,
delamination, rifting,
meteorite?
– Response of lithosphere to
stress - cracking?
– Characterise lithospheric
stress
– What causes rifting?
Important problems 2
• Temperature
– Petrological
temperatures
– Phase equilibrium of
CO2-bearing systems
– Melting at all depths
– other geothermometry
methods e.g.
seismological
• Geochronology
– More high-quality
dates
– Re-date important
chains where old dates
inadequate.
– LIP ages. Can we be
more specific?
Important problems 3
• Seismology
– Interpreting mantle seismic
anomalies in the mantle and
D” - hot? cool? buoyant?
dense?
– Very wide seismic
tomography?
– Transfer of material
between UM & LM?
– Are innovative highresolution experiments
feasible?
• Planetary
– Sort out Venus.
– Look for meteorite
evidence in geology.
Important problems 4
• Field evidence
– Make diagnostic
observations, e.g., uplift??
temperature, mantle
structure.
– Potential plume localities?
– Can we distinguish cause
and effect, e.g. rifting &
volcanism?
– Address problems of the
Emperor-Hawaii system.
• Petrology &
Geochemistry
– Improved melt generation
models needed
– Melting: high-P traceelement partition
coefficients needed
– Where/what is/are the OIB
sources?