MANTLE PLUMES, plumes and

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MANTLE PLUMES, plumes and plumes do we need
all of them?
Alexei V. Ivanov Institute of the Earths Crust
SB RAS, Irkutsk Russia www.mantleplumes.org
1. History of plumes and definitions 2. Plumes
are thought to be required by evidence a.
Temperature b. Age progressive volcanism
c. Heat flow d. Trace elements e.
Radiogenic isotopes f. Seismic tomography
g. Uplift shape and history h. Volume of
magma 3. Does the evidence require plumes? 4. New
models for melting anomalies case studies a.
Permo-Triassic Siberian Traps b. Late
Cenozoic volcanism of Central Asia 5. Conclusions
Alexei Ivanov a lecture at the Paleomagnetism
and geochronology laboratory in Beijing (PGLB),
China, January 11, 2006. The lecture was given on
the occasion of his visit sponsored by a PGLB
visitor grant. Special thanks to Prof. R. Zhu
and Dr. H. He.
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History of plumes and definitions
Modified after (Anderson and Natland, 2005
Ivanov, 2006 in press)
Morgan, 1971
Why current skepticism?
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History of plumes and definitions
Morgans evidence and assumptions
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History of plumes and definitions

1. Oceanic island chains (e.g. Hawaii) do not
   associate with lithospheric plate boundaries and
   hence cannot be explained by plate tectonics
2. Age progressive volcanism requires stable source
   of heat (hot spots) (after Wilson, 1963)
3. Upper mantle is vigorously convecting and hence
   the source of heat is somewhere below (source is
   most likely in the D layer)
4. Oceanic island basalts are enriched in
   incompatible elements compared with depleted
   mid-oceanic ridge basalts, hence source is
   primitive in composition (Earths lower mantle)
5. Hot spots lie atop of localized thermal
   upwellings referred to as plumes
6. Plumes represent the major part of upraising
   convective flow
7. Plumes give the force for plate tectonics.

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History of plumes and definitions
In fluid mechanics literature, "plumes" refer to
upwelling or downwelling driven by self-buoyancy
(Korenaga, 2005)
A mantle plume is a localised, roughly
axisymmetric upwelling of buoyant rock,
originating from a boundary layer deep within the
Earth (Saunders, 2004)
... surface hotspots on Earth may have three
distinct origins (a) ltprimary plumesgt would
originate from the deepest part of the lower
mantle (... Morganian ltplumesgt) (b)
ltSecondarygt plumes originate from ... the top of
the large transient domes that correspond to the
superswells. (c) The remainder could be upper
mantle features, and in that sense Andersonian
(Courtillot et al., 2003).
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History of plumes and definitions
Plume, hotspot, wetspot, melting anomaly - a
region of active or ancient volcanism not
associated with MOR- and IA-types of
volcanism. Superplume, superswell, megaplume,
reheated slab - thermal and/or thermochemical
broad upwelling structure either traversing
through the whole mantle or located in the lower
mantle on a scale of gt108 yr. Lower mantle
plume, primary plume, Morganian plume - thermal
and/or thermochemical localized upwelling
structure traversing through the whole mantle to
the subsurface. Upper mantle plume, secondary
plume - thermal and/or thermo- chemical localized
upwelling structure originating in the
transitional zone. Andersonian plume -
asthenospheric structure, which is not a plume
in any sense.
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History of plumes and definitions
The classical Morganian plume probably does not
exist
Arguments pro and contra
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Plumes are thought to be required by
evidence Temperature
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Does evidence require plumes? Temperature
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Plumes are thought to be required by evidence Age
progressive volcanism
Age increase
Plumes are fixed - plates are moving
No
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Does evidence require plumes? Age progressive
volcanism
Raymond et al., 2000
Fixed plumes gone with the ltmantle?gt wind
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Does evidence require plumes? Age progressive
volcanism
Stuart, 2005
Hawaiian chain is an effect of thermoelastic
propagating crack?
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Does evidence require plumes? Age progressive
volcanism
Rasskazov et al., 1997 2000
Dobretsov et al (2001) use as example of moving
plume
Example of complex stress conditions in
intracontinental setting
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Plumes are thought to be required by
evidence Heat flow
Hofmeister and Criss, 2004
Total output is 44 TW gtthan radiogenic output of
20 TW, hence core must contribute heat to the
surface
1. Measured heat flow value for oceanic crust is
underestimated 2. Half space cooling model used
instead of measurements -gt 44 TW 3. BSE is made
of CI chondrite -gt 20 TW
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Does evidence require plumes? Heat flow
Hofmeister and Criss, 2004
Is the half space cooling model is better than
direct measurements ???
Total output 31 TW radiogenic output 31 TW if
BSE is made of EH
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Plumes are thought to be required by
evidence Trace elements
MORB and IAB are from depleted upper mantle. OIB
must come from somewhere else (lower mantle?)
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Does evidence require plumes? Trace elements
Ontong-Java
There are many examples when studied basalts do
not resemble OIB-trace element component, but
they are still considered to be of lower mantle
plume origin
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Plumes are thought to be required by
evidence Radiogenic isotopes
Iceland plume
Elam and Stuart, 2004
Iceland plume
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Does evidence require plumes? Radiogenic isotopes
(Helium)
Iceland plume
Elam and Stuart, 2004
Class et al., 2005
Iceland plume
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Does evidence require plumes? Radiogenic isotopes
(Helium)
Comoro plume
Iceland plume
Anderson, 2000, 2001
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Plumes are thought to be required by
evidence Seismic tomography
Montelli et al., 2004
Plumes are imaged via seismic tomography
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Does evidence require plumes? Seismic tomography
Plume from the core/mantle boundary or lowermost
mantle RA2002 M2004 Afar
yes no Bowie yes
no Hawaii yes no Iceland
yes no Reunion no
no Tristan no no Louisville
yes no Samoa yes no Tahiti
no yes Ascension no
yes Azores no yes Canary
no yes Easter yes
yes Yellowstone no no
Ritsema and Allen, 2002
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Plumes are thought to be required by
evidence Uplift shape and history
Campbell, 2005
Plumes support broad surface uplifts
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Plumes are thought to be required by
evidence Uplift shape and history
Burov and Guillou-Frottier, 2005
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Does evidence require plumes? Uplift shape and
history
Korenaga, 2005
Two most voluminous LIPs Siberian Traps and
Ontong-Java did not experienced uplift before
the eruptions !
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Plumes are thought to be required by
evidence Large volume of magma
Large volume of magma requires high
temperature and hence lower mantle plumes
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Does evidence require plumes? Large volume of
magma
Actually, it does not
Siberian Traps example
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New models for the melting anomalies case
studies Siberian Traps
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2005
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New models for the melting anomalies case
studies Siberian Traps
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New models for the melting anomalies case
studies Siberian Traps
Modified after Ivanov and Balyshev, 2005
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2004 in preparation
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2004 in preparation
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2004 in preparation
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2004 in preparation
Upper Mantle
Transitional zone
Lower Mantle
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New models for the melting anomalies case
studies Siberian Traps
Ivanov et al., 2004 in preparation
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New models for the melting anomalies case
studies Siberian Traps
Data do not require lower mantle plume origin of
the Siberian Traps Data do require water in the
mantle source of melting Water is brought into
the mantle by plate tectonic processes
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New models for the melting anomalies case
studies Central Asia
Enriched isotopic signatures require long
conservation of recycled material in the lower
mantle and hence lower mantle plumes
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New models for the melting anomalies case
studies Central Asia
Actually, it does not
Central Asian example
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New models for the melting anomalies case
studies Central Asia
A number of papers refer Cenozoic volcanism of
the Central Asia to be related with lower mantle
plume on basis of geochemical data (e.g.
Grachev, 2000 Yarmolyuk et al., 2003)
Zorin et al. (2004) revealed 7 upper mantle
plumes on basis of gravity data
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New models for the melting anomalies case
studies Central Asia
Zorin et al., 2004
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New models for the melting anomalies case
studies Central Asia
Zorin et al., 2006 (2 papers in press)
Seismic tomography after model of Zhao, 2004
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New models for the melting anomalies case
studies Central Asia
Demonterova et al., 2005
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New models for the melting anomalies case
studies Central Asia
Demonterova et al., 2005
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New models for the melting anomalies case
studies Central Asia
Demonterova et al., 2005
SDo/Co
IRbo/Co1-Po
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New models for the melting anomalies case
studies Central Asia
Modified after Zorin et al., 2006 (in press)
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New models for the melting anomalies case
studies Central Asia
Data do not require lower mantle plume origin of
the Central Asian basalts Data do require
fertile fusible source and upper mantle plumes
(in terms of fluid dynamics) Fertile source in
the mantle is created by plate tectonic processes
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Conclusions
1. The term plume is poorly defined and hence
should not be used in publications without
special explanation of its meaning.
2. Evidence cited to prove plumes from the core
and lower mantle in many instances do not
require such interpretation.
3. Many alternative models can better explain
melting anomalies than lower mantle plumes
do.
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Thanks!