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The
Plume Assumption: Frequently Used Arguments
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“The method of postulating [assuming]
what we want has many advantages. They are the
same as the advantages of theft over honest
toil.”
Bertrand Russell (Introduction to Mathematical
Philosophy)
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“We see that many assumptions used
in previous hypotheses can be discarded as unnecessary
... there is no need to locate the source of
plumes in the lower mantle.”
Richter, F. & Parsons, B. J. Geophys. Res.,
80, 2529-2541, 1975 |
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Plate tectonics is the style of convection adopted
by a hot planet with a cold atmosphere and an interior that is buffered
by the melting point of rocks. In a planet as large as the Earth the
effect of pressure can make the gravitational separation of different
density materials, during the hot accretion process, irreversible, even
if the intrinsic densities of the superposed materials only differ by
1%. After accretion the planet is stratified according to volatility,
melting point, chemistry and density. The deep layers are inaccessible
since no reasonable temperature can make the material buoyant. The top
of the mantle is characterized by narrow, dense downwellings and broad,
warm, passive upwellings. The warmer and more fertile regions are at
or above the melting point, partly because of moderate temperature variations
and partly because of variations in melting temperatures. Most of the
radioactive elements are in the crust and upper mantle because of fractionation
during accretion and upward transport of melt, a process called radial
zone refining.
A small fraction of the total surface heat flow comes
from the core. The plume hypothesis focuses on this
core heat. The high pressure and low heat flow at
the base of the mantle means, however, that buoyant
upwellings must be huge, long-lived and slow to develop.
Even a small intrinsic density contrast between the
deep layers in the mantle will trap the upwellings,
since pressure lowers the thermal expansivity of silicate
rocks, and increases the viscosity and thermal conductivity.
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Textbooks, however, show narrow plumes of material
rising from the core-mantle boundary directly to Yellowstone and Iceland
and about 40 other volcanoes designated as hotspots. These cartoons
are based on simple laboratory experiments involving the injection of
hot fluid into a tank of stationary fluid, or the pot-on-the-stove analogy.
Pressure is unimportant in these simulations in which all the thermal
properties are more-or-less constant.
The effect of pressure on such key physical
parameters as interatomic distances, thermal conductivity, viscosity
and coefficient of thermal expansion is the main reason why the plume
hypothesis is not viable in an Earth-sized planet. Yet the pressure
effect is seldom discussed, never duplicated in laboratory simulations
and seldom treated in computer simulations.
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Among the more critical assumptions that have been made in developing
the plume hypothesis are:
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“normally” the mantle is below the
melting point
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melting anomalies are due to localized high temperature,
not low melting point
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the mantle is almost isothermal (adiabatic)
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cracks will not be volcanic unless the local temperature
is anomalously high
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high temperatures require importation of heat
from the core-mantle boundary in the form of narrow jets
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the upper mantle is vigorously stirred and is
chemically homogeneous
None of these assumptions are supported (see references below) and
the widely ignored effect of pressure leads to a quite different picture
of the dynamics in the interior of the mantle. The proximity of the
upper mantle to its melting point, and the variable fertility of the
mantle due to plate tectonic processes, makes the plume hypothesis unnecessary.
Why then is the plume model so widely accepted? What are the main arguments
for plumes? The current arguments are quite different from those on
which the plume hypothesis was originally based, although the “fixity”
argument is sometimes still used (DePaolo & Manga, 2003).
Evidence now used in support of plumes includes the large volume of
erupted basalts, the rapidity of eruption, the chemistry of the magma,
elevated helium isotope ratios of some of the basalts at some hotspots,
and the observation that inferred hotspot tracks cross ridges.
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The most convincing arguments for a “hotspot” or a plume
would be high magma temperature, uplift, thick crust, high heat flow,
thermal erosion of lithosphere, or a deep mantle tomographic signal.
These are indicators of a thermal mechanism, as opposed to athermal
mechanisms which have also been proposed for oceanic plateaus, swells
and continental flood basalts (CFB). Athermal mechanisms include focusing,
fertility, ponding, EDGE and rift mechanisms, processes involving lithospheric
stress and dikes, and a partially molten shallow mantle (Anderson,
1998). Melting of particularly fertile or volatile-rich mantle containing
materials such as recycled oceanic crust, sediments, eclogite, piclogite
or pyroxenite, also obviates the need for high plume temperatures.
The absolute amount of magma is often used as an argument supporting
plumes but usually no comparisons with other mechanisms are made. For
example, ridges also produce large quantities of basalt and do so for
much longer periods of time. Focusing and EDGE-driven effects can increase
rates by a factor of five for short periods of time (see references
below). Ridges have to share their source with adjacent ridge sections
while a CFB can drain a large area to a central point. CFB can also
drain an area that was ponding magma for a long period of time prior
to the extension that allowed eruption. Mature fast-spreading ridges
do not have this opportunity and their drainage area is limited. CFB
are transients and three-dimensional, while most ridges are steady state
and two-dimensional. These factors alone increase eruption rates and
volumes by large factors over ridges, with no increase in temperature.
Also, some plateaus clearly have a continental base and are not entirely
recent features as often assumed. Other processes that can give results
similar to plumes are small-scale convection, an intrinsic part of plate
tectonics, and convection induced by lithospheric architecture (corner
flow).
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Richards et al. (1989) pointed out that large
volumes (of the order of 106 km3 of basalt) and
rapid rates (order of 1 Myr) are characteristics of large igneous provinces
(LIPs) and CFB. They assumed that these must be attributes of plumes since
it was believed that LIPs were the result of plumes rather than athermal
mechanisms, such as increased fertility of the mantle, corner flow or
plate tectonics. Attempts to model these characteristics by fluid dynamic
calculations have failed, however (Cordery et al., 1997; Farnetani
& Richards, 1994; Farnetani, 1996).
Midplate volcanism cannot be explained, neither the volumes
nor the rates. The problem is that thick lithosphere precludes much melting
since the shallow part of the melting column is taken up by the plate.
A fertility explanation does not suffer from this defect. Ad hoc
adjustments have been made to the plume hypothesis to increase the amount
of melting (Cordery et al., 1997). Even so, the eruption rates
calculated are an order of magnitude too low, and even moderately thick
lithosphere is calculated to eliminate melting altogether. These calculations
tended to lend credence to mechanisms such as stress control of eruption
rates (the lithospheric valve mechanism) and fertility and volatile variations
in the shallow mantle (all athermal mechanisms) as explanations for voluminous
midplate volcanism. Large volumes and eruption rates, especially if ephemeral,
can result from low mantle melting point, increase in the basalt content
of the shallow mantle (the recycling mechanism), increase in volatile
content, EDGE- and rift-induced convection, and focusing. High temperature
alone apparently is inadequate (Cordery et al., 1997, Farnetani
& Richards, 1994, Farnetani, 1996). Athermal mechanisms
do not require a deep or hot source. |
So what are the arguments (A) quoted
in support of the mantle plume as the standard
model for the origin of flood basalts, and what
are the counter arguments (C)? |
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A1.
Very large volumes of magma.
C1.
One must compare the observed rates with something. The absolute
value by itself means nothing, particularly since it is trivial
compared to the output of ridges, island arcs, and backarc basins,
and modeling to date, using plumes or high temperatures, has
not explained these volumes or rates.
The
rate-limiting factor appears to be the porous flow part,
from the asthenosphere to the surface. If magma can be focused
by the viscous equivalent of cracks and dikes then flow rates
can be increased. If the ascending melt is impeded for long
periods of time, and accumulates, then large volumes can be
erupted quickly, once the diking condition is satified (i.e.
the least compressive direction is horizontal). Prior to establishing
this stress state in the plate, melts may pond or be stored
in sills and magma chambers.
There
are several opportunities for research and new thinking on athermal
mechanisms for concentrating flow and volcanic episodicity.
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A2.
Eruption during a very short time interval.
C2. The short
time actually implies stress- or lithosphere-control, a valving
action. Plume theorists have shown that in the plume model the
timescale is controlled by the viscosity of the deep mantle
and they get time scales of 10 Myr or longer. A stress mechanism
can be instantaneous (a feature of Stokes flow). Global synchronism
of volcanism also favors a stress explanation – one that
involves a global plate reorganization.
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A3.
Rapid eruption of huge volumes of magma only occur in flood
basalt provinces, and thus these events require a special explanation.
C3.
This unique event can be a change in stress or a plate reorganization.
EDGE- and rift-induced convection mechanisms are, by nature,
episodic, and flux rates vary enormously so there may be no
“event”, just as no causative event is responsible
for a continent-continent collision or a ridge-trench annihilation
or variations of eruption rates along volcanic chains (although
these may be caused by stress variations). A mantle
plume is often assumed to be necessary to get the volumes and
rates but this is not consistent with published calculations
(Richards et al. (1989) argue this way, but it is a
circular argument). This is an intuitive, rather than a quantitative
argument: “high volumes imply large degrees of melting
and this requires high temperatures”. However, “midplate”
volcanoes have a decreased melting column and other mechanisms
such as fertility, volatiles, focusing, EDGE etc. are required
either instead of, or in addition to, high temperatures, even
in plume models. Low melting point (fertility) or an eclogite-rich
source is an alternative to high absolute temperatures (the
plume model).
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A4.
Only plumes can explain the volumes and very rapid eruption of
LIPs.
C4.
Some models certainly don't work but a simple assertion to this
effect is not enough. Models must be tested. Usually, alternative
models are not even considered. The recent literature suggests
alternatives that may be viable, and follow up on earlier suggestions
of a partially molten asthenosphere, a fertile source (eclogite,
piclogite), focusing, EDGE convection, warming of midplate mantle
by continental insulation, refertilization of the shallow mantle,
ponded melt releases by stress control, diking, and so on. |
A5.
LIPs are often associated with time-progressive volcanic trails
that are well-modeled as plume tails.
C5.
Fewer than half of LIPs have even a postulated tail and even the
most prominent examples are contentious (Sheth, 1999a,b;
2000, Burke, 1996, McHone, 1996, 1998, 2000)
or admittedly ad hoc (Morgan, 1981). Also, there
are equally voluminous siliceous eruptions unaccounted for in
the plume-head theory. According to the Campbell-Griffiths plume
hypothesis (which is based on hot fluid injection, rather than
convection, experiments) every narrow Morgan-type plume must be
accompanied by a warm bulbous plume head. Attempts have therefore
been made to find a candidate plume head for every "hotspot"
track, and vice versa. For example, both the Jan Mayen "hotspot"
(actually a microcontinent with basalt flows on top) and Hawaii
have been suggested as the "hotspot" responsible for
the Siberian flood basalts and both the Ontong Java and Fiji plateaus
have been assigned to the Louisville Ridge. "Missing"
plume heads are often attributed to subduction, e.g. the Emperor
seamount chain (which appears to have started on a ridge). These
suggested associations and explanations are often speculative
and mutually contradictory. The other side of the coin is that
so-called tracks often correspond to pre-existing tectonic features. |
A6.
Hotspots often cross ridges, showing that a fixed plume underneath
the plate is responsible.
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C6.
Plate reconstructions based on the fixed
hotspot assumption have this feature
but other plate reconstructions do not
show ridges crossing hotspots (Morgan,
1981). Morgan pointed out that the plate
reconstructions of others (including
Molnar and Burke) were different from
his in this way. The association of
some "linear" volcanic features
with CFB has been used to assert that
the CFB is now separated by a ridge
from the hotspot. However, these associations
have been disputed. For example, it
has been suggested that the Laccadive
– Chagos – Rodrigues –
Mauritius – Réunion or
Deccan/Chagos – Laccadive/Reunion
volcanic "lineation" (which
it is not) or "hotspot track"
is the "tail" associated with
the Deccan
"plume head".
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Burke
(1996) has argued strongly against this
interpretation. He favors multiple small
plumes, a common theme when age and spatial
associations are not simple or as predicted.
There is a volcanic hiatus of ~ 20 Myr
and a clear volcano/structural change
across the ridge which argues against
the coherent-hotspot model. Bailey
& Wooley (1995) also argue against
a plume origin for the features on the
African plate.
There is also considerable doubt as to
whether Réunion is a hotspot rather
than a reactivated ridge. The island is
located on the intersection of an abandoned
ridge and a fracture zone, and between
two other nearby fractures. It does not
flex the lithosphere and has smaller volume
and density than has been used in previous
estimates of its total mass or buoyancy
flux. It is not similar to Hawaii. The
conjectured track of the Rénion
"hotspot" (the Laccadive –
Chagos – Rodrigues – Mauritius
– Réunion or Deccan/Chagos
– Laccadive/Réunion volcanic
"track") is also unlike the
Hawaiian, Emperor and Louisville volcanic
chains.
Both
Réunion and Mauritius appear to
be related to pre-existing and subsequent
tectonic features. They developed atop
Paleocene fossil spreading centers and
were carried away from each other by a
fracture zone in between (Hirn,
2002). Click
here for more on proposed plume "head-tail"
associations.
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A7.
The geochemistry of LIP magmas is consistent with a plume origin.
In particular, the elevated helium isotope ratios often observed
indicate a lower-mantle source.
C7.
This is the circular argument that, because Yellowstone, Hawaii
and Iceland are products of a hot spot, then the elevated helium
isotope ratios observed there must be produced in the lower mantle.
In other words, by definition, the elevated ratios come
from the lower mantle. The only reason elevated helium isotope
ratios were associated with plumes in the first place was because
such ratios were observed at Yellowstone, Iceland and Hawaii which
were thought to result from plumes. It is important to remember
what is an assumption and what is evidence. Reasonable models
have been proposed for how high helium isotope ratios can arise
from the upper mantle (see helium
fundamentals page) and therefore they are not unambiguous
indicators of plumes from the lower mantle |
A8.
The problem that thermal plumes cannot deliver the required
volumes can be solved by adopting an aspect of the chemical
plume model, i.e., a more fertile source. This is achieved
by postulating that recycled oceanic crust that has been subducted
into the lower mantle is swept up in rising peridotite plumes
(e.g., Cordery et al., 1997). This can also explain
the trace element characteristics of LIP basalts.
C8.
The chemical plume model, and the eclogite and recycled-crustal
models are not new, and are alternatives to deep, hot plumes.
Introduction of eclogite into plumes was necessary to get large
volumes of melt, but when this is done there is no longer need
for plumes or a deep source. If the shallow mantle is close
to the solidus of peridotite it will be near the liquidus of
eclogite and melt can be created at “normal” mantle
temperatures. A shallow fertile source is an alternative to
plumes, and gives the necessary volumes in the absence of a
high temperature anomaly.
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A9.
There is no geologic evidence for extension prior to the eruption
of CFB.
C9.
There is abundance evidence for extension, but usually not uplift,
prior to volcanism. Dikes can also take up extension, but this
is generally disregarded. Minor amounts of extension, with magma
viscosities, is all that is needed to provide the volumes and
rates from a fertile and partially molten mantle. Meter-wide
dikes can certainly provide the necessary flow rates and this
can be below geologic resolution for extension.
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All of the arguments used
in support of plumes and against alternative
mechanisms have been widely discussed in the
literature. There is little support for these
arguments but they are constantly repeated,
and new papers often quote earlier ones containing
undiscussed repetitions. In order to progress
we must critically assess the original sources
of ideas, not simply repeat assertions, and
to facilitate this an extensive bibliography
is provided below: |
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References on CFB and other LIPs: non-hotspot processes
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Anderson, D.L., The EDGES of the mantle, in The
Core-Mantle Boundary Region, edited by M.E. Gurnis, E.K. Wysession,
and B.A. Buffett, pp. 255-271, AGU,Washington, D. C., 1998.
- Bailey. D.K. and Woolley, A.R., Magnetic quiet periods and stable
continental magmatism: can there be a plume dimension? in Anderson,
D.L., Hart, S.R., and Hofmann,A.W., Convenors, Plume 2, Terra Nostra,
3/1995, 15-19, Alfred-Wegener-Stiftung, Bonn, 1995.
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Czamanske, G.K., Demise of the Siberian plume:
Paleogeographic and paleotectonic reconstruction from the prevolcanic
and volcanic records, north-central Siberia, Int. Geol. Rev.,
40, 95-115, 1998.
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Favela, J., and D.L. Anderson, Extensional tectonics
and global volcanism, in Editrice Compositori, edited by
E. Boschi, G. Ekstrom, and A. Morelli, pp. 463-498, Bologna, Italy,
1999.
- Hirn, A., Réunion (Indian
Ocean) Oceanic Island Volcanism: Seismic Structure and Heterogeneity
of the Upper Lithosphere, EOS Trans. AGU Fall Meet. Suppl., Abstract,
83, S72C-03, 2002.
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McHone, J.G., Constraints on the mantle plume model
for Mesozoic alkaline intrusions in northeastern North America, Can.
Min., 34, 325-334, 1996.
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McHone, J.G., Comment on Opening of the central
Atlantic and asymmetric mantle upwelling phenomena: Implications for
long-lived magmatism in western North Africa and Europe, Geology,
26, 282, 1998.
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McHone, J.G., Non-plume magmatism and tectonics
during the opening of the central Atlantic ocean, Tectonophysics,
316, 287-296, 2000.
-
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Richter, F.M., Convection and the large-scale circulation
of the mantle, J. Geophys. Res., 78, 8735-8745,
1973.
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Richter, F.M., and B. Parsons, On the interaction
of two modes of convection in the mantle, J. Geophys. Res.,
80, 2529-2541, 1975.
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Sheth, H.C., Flood basalts and large igneous provinces
from deep mantle plumes: fact, fiction, and fallacy, Tectonophysics,
311, 1-29, 1999.
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Sheth, H.C., The timing of crustal extension, diking,
and the eruption of the Deccan flood basalts, Int. Geol. Rev.,
42, 1007-1016, 2000.
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Sheth, H.C., I.S. Torres-Alvarado, and S.P. Verma,
Beyond subduction and plumes: A unified tectonic-petrogenetic model
for the Mexican volcanic belt, Int. Geol. Rev., 42,
1116-1132, 2000.
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Sheth, H. C., A historical approach to continental
flood basalt volcanism: insights into pre-volcanic rifting, sedimentation,
and early alkaline magmatism, Earth planet. Sci. Lett., 168,
19-26, 1999.
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Smith, A.D., A re-appraisal of stress field and
convective roll models for the origin and distribution of Cretaceous
to Recent intraplate volcanism in the Pacific basin, Int. Geol.
Rev., 45, in press, 2003.
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Smith, A.D., Intraplate volcanism: concepts, problems
and proofs, Astron. Geophys., 44, 2.8 -2.9,
2003.
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Tanton, L.T.E. and B.H. Hager, Melt intrusion as
a trigger for lithospheric foundering and the eruption of the Siberian
flood basalts, Geophys. Res. Lett., 27,
3937-3940, 2000.
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Vogt, P.R., Bermuda and Appalachian-Labrador rises:
Common non-hotspot processes?, Geology, 19, 41-44, 1991.
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References on helium isotopes and
the helium paradoxes
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Breddam, K., and M.D. Kurz, Helium isotope signatures
of Icelandic alkaline lavas, EOS Trans. AGU, 2001.
-
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Kellogg, L.H., and G.J. Wasserburg, The role of
plumes in mantle helium fluxes, Earth planet. Sci. Lett.,
99, 276-289, 1990.
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Meibom, A., D.L. Anderson, N.H. Sleep, R. Frei,
C.P. Chamberlain, M.T. Hren, and J.L. Wooden, Are high 3He/4He
ratios in oceanic basalts an indicator of deep-mantle plume components?,
Earth planet. Sci. Lett., in press, 2003.
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CFB are not underlain by hot plume heads
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Anderson, D. L., Tanimoto, T., and Zhang, Y. -S.,
1992a, Plate tectonics, and hotspots: The third dimension: Science,
256, 1645-1650.
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Anderson, D. L., Zhang, Y. -S., and Tanimoto, T.,
1992b, Plume heads, continental lithosphere, flood basalts, and tomography,
in Storey, B. C., Alabaster, T., and Pankhurst, R. J., eds., Magmatism
and the Causes of Continental Break-up: Geol. Soc. (London) Spec.
Publ. 68, 99-124.
-
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Tanimoto, T., Predominance of large-scale heterogeneity
and the shift of velocity anomalies between the upper and lower mantle,
J. Phys. of the Earth, 38, 493, 1990.
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Thermal plumes cannot explain the volumes or rates
of CFB magmatism
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Cordery, M. J., Davies, G. F., and Campbell, I.
H., 1997, Genesis of flood basalts from eclogite-bearing mantle plumes:
J. Geophys. Res., 102, 20,179-20, 1997.
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Farnetani, C.G., Excess temperature of mantle plumes:
the role of chemical stratification across D", Geophys. Res.
Lett., 24, 1583-1586, 1996.
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Farnetani, C.G., and M.A. Richards, Numerical investigations
of the mantle plume initiation model for flood basalt events, J.
Geophys. Res., 99, 13,813-13,833, 1994.
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Richards, M. A., Duncan, R. A., Courtillot, V.
E., Flood basalts and hotspot tracks: plume heads and tails, Science,
246, 103-107, 1989.
-
Tanton, L.T.E., and Hager, B.H., Melt intrusion
as a trigger for lithospheric foundering and the eruption of the Siberian
flood basalts, Geophys. Res. Lett., 27,
3937-3940, 2000.
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Athermal mechanisms of CFB magmatism
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Favela, J., and D.L. Anderson, Extensional tectonics
and global volcanism, in Editrice Compositori, edited by
E. Boschi, G. Ekstrom, and A. Morelli, pp. 463-498, Bologna, Italy,
1999.
-
Holbrook, W.S. and Kelemen, P.B., Large igneous
province on the U.S. Atlantic margin and implications for magmatism
during continental breakup, Nature, 364,
433-436, 1993.
-
Lameyre, J., Black, R., Bonin, B. and Giret, A.,
The magmatic provinces of eastern America, West Africa, and Kerguelen:
indications for a tectonic control of within-plate magmatism triggered
from above and associated processes, Annals of the Soc. Geology
Nord, CIII, 101-114, 1984.
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Sleep, N.H., Tapping of magmas from ubiquitous
mantle heterogeneities: An alternative to mantle plumes?, J. Geophys.
Res., 89, 10,029-10,041, 1984.
-
Smith, A. D., Back-arc convection model for Columbia
River basalt genesis: Tectonophysics, 207,
269-285, 1992.
-
Smith, A. D., The continental mantle as a source
for hotspot volcanism: Terra Nova, 5, 452-460,
1993.
-
Vogt, P.R., Bermuda and Appalachian-Labrador rises:
Common non-hotspot processes? Geology, 19,
41-44, 1991.
-
Yaxley, G. M., Experimental study of the phase
and melting relations of homogeneous basalt + peridotite mixtures
and implications for the petrogenesis of flood basalts, Contrib.
Mineral. Petrol., 139, 326-338, 2000.
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Tectonic explanations of CFB
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Bailey, D. K., Episodic alkaline igneous activity
across Africa: implications for the causes of continental break-up,
in Storey, B. C., Alabaster, T., and Pankhurst, R. J., eds., Magmatism
and the Causes of Continental Break-up: Geol. Soc. London Spec.
Pub. 68, 91-98, 1992.
-
Bailey. D.K. and Woolley, A.R., Magnetic quiet
periods and stable continental magmatism: can there be a plume dimension?
in Anderson, D.L., Hart, S.R., and Hofmann, A.W., Convenors, Plume
2, Terra Nostra, 3/1995, 15-19, Alfred-Wegener-Stiftung, Bonn,
1995.
-
Burke, K. C., The African plate, S. Afr. J.
Geol., 99, 341-409, 1996.
-
Czamanske, G. K., Gurevich, A. B., Fedorenko, V.,
and Simonov, O., Demise of the Siberian plume: paleogeographic and
paleotectonic reconstruction from the prevolcanic and volcanic records,
North-Central Siberia, Int. Geol. Rev., 40,
95-115, 1998.
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McHone, J.G., Volatile emissions of Central Atlantic
Magmatic Province basalts: Mass assumptions and environmental consequences,
in Hames, W.E., McHone, J.G., Renne, P.R., and Ruppel, C., editors,
The Central Atlantic Magmatic Province: AGU, Geophysical
Monograph 136, p. 241-254, 2002.
-
McHone, J. G., Non-plume magmatism and tectonics
during the opening of the central Atlantic Ocean, Tectonophysics,
316, 287-296, 2000.
-
McHone, J.G., Comment on Opening of the central
Atlantic and asymmetric mantle upwelling phenomena: Implications for
long-lived magmatism in western North Africa and Europe, Geology,
26, 282, 1998.
-
McHone, J. G., Constraints on the mantle plume
model for Mesozoic alkaline intrusions in northeastern North America:
Can. Min., 34, 325-334, 1996.
-
McHone, J.G., Broad-terrane Jurassic flood basalts
across northeastern North America, Geology, 24,
319-322, 1996.
-
McHone, J.G. and Shake, S.N., Structural control
of Mesozoic magmatism in New England, in Mason, R., ed., Basement
Tectonics 7, Boston, Kluwer Academic, 399-407, 1992.
-
McHone, J.G., Tectonic and paleostress patterns
of Mesozoic intrusions in eastern North America, in Manspeizer, W.R.,
ed., Triassic-Jurassic Rifting: Continental Breakup and the Origin
of the Atlantic Ocean and Passive Margins, Part B: New York,
Elsevier, 607-619, 1988.
-
McHone, J.G. and Butler, J.R., Mesozoic igneous
provinces of New England and the opening of the North Atlantic Ocean,
Geol. Soc. Am. Bull., 95, 757-765, 1984.
-
McHone, J.G., Mesozoic igneous rocks of northern
New England and adjacent Quebec, Geol. Soc. Am., Map and Chart
Series MC-49, scale 1:690,000, 5 p. + text,
1984.
-
Sheth, H. C., A historical approach to continental
flood basalt volcanism: insights into pre-volcanic rifting, sedimentation,
and early alkaline magmatism, Earth Planet. Sci. Lett., 168,
19-26, 1999a.
-
Sheth, H. C., Flood basalts and large igneous provinces
from deep mantle plumes: fact, fiction, and fallacy, Tectonophysics,
311, 1-29, 1999b.
-
Sheth, H. C., The timing of crustal extension,
diking, and the eruption of the Deccan flood basalts. Int. Geol.
Rev., 42, 1007-1016, 2000.
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