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Russian Geology and Geophysics 57 (2016) 1135–1142
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Transmantle (intratelluric) fluid flows: a new model for plumes
and plume magmatism
N.S. Zhatnuev *
Geological Institute, Siberian Branch of the Russian Academy of Sciences, ul. Sakh’yanovoi 6a, Ulan-Ude, 670047, Russia
Received 3 June 2015; accepted 24 September 2015
Abstract
A fluid model for the formation of mantle plumes is proposed. During the emission of gas from the Earth’s core, it accumulates as lenses
at the core–mantle boundary. Reaching a critical size, the lenses burst out into the mantle and migrate to the surface. A relatively stationary
transmantle fluid flow from the core–mantle boundary arises, which heats the mantle and the layer interacting with it. The flow stops in the
base of the hard lithosphere and spreads laterally, causing its melting accompanied by the formation of magma chambers, which, reaching
critical sizes, massively intrude and flow out.
© 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
Keywords: mantle plumes; transmantle flows; fluid fracturing; magma fracturing; fluid cavities; excess pressure
Introduction
The hypothesis of mantle plumes (MP) was put forward by
Morgan (1971) and Wilson (1963). Later, it was developed
into the concept of hot fields (Zonnenshain and Kuz’min,
1983, 1992). A comprehensive analysis of the MP problem
was made by Dobretsov (2008), Kuz’min et al. (2011), and
Puchkov (2009), who considered the assumed nature and
mechanisms of MP formation. As follows from the works by
Dobretsov (2008), Letnikov (2001), Letnikov and Dorogokupets (2001), and Puchkov (2009), MP are the result of the
hydrogen and hydrocarbon degassing of the Earth’s core
followed by the oxidation of these gases to water and carbon
dioxide during the ascent. However, the mechanisms of MP
ascent and the details of MP evolution are different in the
above works. According to Letnikov (2001), plumes result
from thermal explosions at the core–mantle boundary accompanied by the outburst of gases at >1300 kbar (130 GPa) and
>4000 ºC, which “burn” through the mantle on the way toward
the surface. The interaction of hydrogen fluid with the
oxygen-containing matrix led to the generation of heat and
water, which caused the conversion of the initial hydrogen
plume into a water–hydrogen one with volatile metal compounds. According to Dobretsov (2008), plumes are generated
in mantle craters of thermochemical nature at the core–mantle
boundary. These craters result from the input of a chemical
material lowering the melting temperature at the mantle base.
Based on experiments with viscous liquids (Campbell, 2005;
Griffiths and Campbell, 1990), a convective mechanism of MP
generation was proposed. It implies the formation of a “head
and tail” structure during the ascent of a light material in a
heavier medium.
The first two hypotheses (Dobretsov, 2008; Letnikov, 2001)
suggest that MP form during the melting of matter in a
continuous conduit from the Earth’s core up to the lithosphere
base. Later research (Zhatnuev, 2010), however, showed a
high excess pressure (EP) in long magma conduits, considerably exceeding the rock strength. In this case, the plume
material should have reached the surface as a result of
catastrophic breaks through the lithosphere, which is not in
fact observed. Following the hypothesis of Campbell (2005)
and Griffiths and Campbell (1990), the ascent should be, on
the contrary, slow, because this is a convective mechanism
and the rate of ascent is close to the rate of mantle convection.
If this mechanism actually took place, one would undoubtedly
observe the deviation of plume from the vertical at a
considerable angle under the impact of the “mantle wind”
(Puchkov, 2009).
* Corresponding author.
E-mail address: [email protected] (N.S. Zhatnuev)
1068-7971/$ - see front matter D 201 6, V.S. So bolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.rgg.201
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6.08.002
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The hypothesis of intratelluric flows
Korzhinskii (1952) was the first in Russia who put forward
a hypothesis of the existence of solutions of subcrustal nature,
called transmagmatic, which cause granitization, melting, and
metasomatism. The hypothesis of the mantle genesis of fluids
inducing crustal-substratum melting was proposed by P. Termier in 1910. He explained crustal metamorphism and melting
by the presence of filtration columns, i.e., ascending flows of
percolating juvenile solutions (Korzhinskii, 1968; Ovchinnikov, 1973). This hypothesis was supported by Kuznetsov
and Izokh (1969) and by Ovchinnikov (1973). Based on
geological observations and a review of voluminous literature
data on magmatism, metamorphism, and accompanying processes, they came to the conclusion about deep mantle sources
of heat and fluids causing magmatism, metamorphism, and
ore formation. The mechanisms of mantle fluid migration and
heat sources, however, remained unclear. These fluids and heat
sources are necessary for endogenic processes in crust, since
the assumed mechanism of material supply from the mantle
along deep faults is impossible because of the ductile rheology
of the mantle and lower crust. Moreover, the rheologic
layering of the crust and lithosphere can be rather intricate in
the case when brittle layers are changed by ductile and again
brittle ones to a considerable depth from the surface (Corti et
al., 2003).
I fully support the viewpoints of the above researchers on
the mantle nature of heat and fluid sources and propose a
particular mechanism of hot-fluid input from the deep mantle
into the Earth’s upper horizons and a different mechanism of
MP formation and accompanying magmatism.
A model for transmantle fluid flows
and the formation of mantle plumes
The proposed model for heat and material input is based
on the possible upward migration of fluids in the ductile
mantle along isolated subvertical fracture cavities. The essence
of the mechanism of fracture cavity migration was outlined
earlier (Zhatnuev, 2005). The motion is favored by the
compression of the cavity walls due to the lithostatic pressure.
The fluid, by virtue of its lower density, transmits the pressure
into the “head” of the cavity, thus creating an EP proportional
to the vertical size of the system and to the difference in fluid
and rock densities (Fig. 1a). The calculated vectors of fluid
and lithostatic pressures onto the cavity wall are shown in
Fig. 1. In the case of a rather long vertical conduit and a
significant difference in the densities of fluid and the enclosing
ductile medium, the EP becomes higher than the rock strength,
which leads to a “fluid fracturing” in the head and (since the
volume is constant) a collapse in the tail of the cavity. This
process ensures the upward movement of the cavity, which is
similar to the floating of gas bubbles in liquid, but in our case
the process runs in a solid, plastically deformable medium.
A plot of EP initiation is shown in Fig. 1c. The process is
substantiated as follows.
In the case of a subvertical fracture cavity filled with fluid
(Fig. 1a) in the plastic rock, the lithostatic pressure in the head
(top) fracture cavity, P1lith (Fig. 1c), at depth H1 is
H1
P1lith = ∫ g (h) ρr (h) dh,
(1)
0
Fig. 1. The mechanism of EP initiation in a closed fracture cavity under plastic deformations: a, Vertical cavity with a fluid: Arrows show the fluid flow in the cavity
and hydraulic fracturing in its head, l is the height of the cavity; b, vectors of hydrostatic internal fluid pressure and lithostatic external pressure on the cavity wall;
c, plots of lithostatic and hydrostatic pressures in the cavity. ∆Pfl is the EP of fluid in the head of the cavity.
N.S. Zhatnuev / Russian Geology and Geophysics 57 (2016) 1135–1142
where ρr is the rock density, H1 is the depth from the Earth’s
surface to the cavity head, g is the acceleration due to gravity,
and h is the integration variable. The lithostatic pressure in
the “tail” (bottom) of the fracture cavity, P2lith, is also
calculated from (1) but for depth H2.
The intrinsic pressure of the fluid at the bottom of the
fracture cavity (under assumption that the fluid density is the
same throughout the height of the cavity) is
Pfl = ρflgl,
(2)
where ρfl is the fluid density and l is the vertical length of
the cavity.
The fluid pressure in the “tail” of the cavity, P2fl (at depth
H2), is equal to the lithostatic pressure P2lith, and the fluid
pressure in the head of the cavity (at depth H1) is
P1fl = P2fl – Pfl.
(3)
Thus, the EP in the head of the fracture cavity (Fig. 1c) is
∆Pfl = P1fl – P1lith.
(4)
Admitting the Earth’s core as a source of reduced fluids
(Dobretsov, 2008; Letnikov, 2001; Letnikov and Dorogokupets, 2001) and taking into account its liquid state and the
solid state of the bordering mantle, we assume that gas
emission from the core will lead to the formation of lenses,
horizontal cavities (Fig. 2, on the left) accumulating the fluid,
at the core–mantle boundary. The cavities are a kind of
“craters” (Dobretsov, 2008). This process might be due to the
high rate of gas emission and the impossibility of the
lower-mantle material to absorb the gas or transmit it upward.
The abundance of such fluid lenses and their interaction with
the lower mantle probably explains the nature of superswells
1137
of the layer D″, which are not only of thermal nature but are
also compositionally heterogeneous (Burke et al., 2008).
However, these lenses cannot grow infinitely and, reaching
critical sizes (Fig. 2), undergo fluid fracturing (similar to
hydraulic fracturing), transform into a vertical closed fracture
cavity, and ascend into the mantle. At the initial moment after
the fluid fracturing, the height of the cavity is close to the
lateral sizes of the lens (with the cavity volume remaining the
same) and is much larger than the initial height. This causes
an instantaneous increase in EP, which becomes much higher
than the mantle strength and favors the rapid ascent of the
cavity. However, extremely large vertical cavities in the
ductile medium are unstable and, likely, break into smaller
ones, similarly to the crushing of large air bubbles floating in
liquid. The mechanism of this process was not considered in
this study.
A critical size is the height of a fluid lens at which the EP
becomes higher than the mantle tensile strength. The EP
corresponding to a critical size is calculated from Eqs. (1)–(4),
but the calculation requires data on the strength of the mantle
at its boundary with the core and on the fluid properties, which
are not reliably known under thermodynamic conditions of the
layer D″ and are the subject of discussion. In this work the
mantle base strength was taken close to the lithosphere base
strength (Corti et al., 2003). The rheologic characteristics of
the lithosphere of different types, from stable four-layered to
young two-layered oceanized, differ considerably. The
strength (σm) of the lithosphere of any type, however, becomes
lower than 50 MPa near its base (mantle part) (Fig. 3). For
calculations we borrowed the fluid density value from Letnikov and Dorogokupets (2001), who showed that the specific
density of fluid (g/cm3) at the core–mantle boundary decreases
Fig. 2. Scheme (on the left) of the formation of fluid lenses at the core–mantle boundary and their outburst and ascent in the form of a fracture cavity in the mantle.
Arrows show a fluid flow from the core. hcr is the critical height of lens necessary for its outburst into the mantle. Plot (on the right) of the calculated critical heights
(h1–h9) of lenses at the core–mantle boundary at the mantle strength of 50, 100, and 150 MPa. 1, 2, and 3 are the fluid densities, g/cm3.
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Fig. 3. Strength profiles (Corti et al., 2003) for the young stable four-layered lithosphere (1), thinned three-layered lithosphere (2), and oceanized thinned lithosphere
(3), with the author’s supplements. σm is the strength of the lithospheric-mantle base. Points and dashed lines show the maximum strength of lithosphere layers, and
horizontal dashed lines, their depth from the surface. C is the crust thickness, and L is the lithosphere thickness. On the right of the figure, there is a schematic model
for plume evolution at different stages of evolution of the lithosphere strength and thickness.
in the series N2(3.5)–CH4(1.4)–He(1.25)–H2(0.4). In different
variants of calculations, the mantle strength was taken conservatively: 20, 50, and 100 MPa, which is much higher than the
lithosphere base strength (Corti et al., 2003). Fluid densities
were taken equal to 1, 2, and 3 g/cm3, i.e., close to the values
given by Letnikov and Dorogokupets (2001).
The results of calculations are presented in Fig. 2 (on the
right). At the mantle strength of 20 MPa and fluid density of
1 g/cm3, the critical height of lens, hcr, is ~0.4 km (h1 at σ =
20 MPa); at the fluid density of 2 and 3 g/cm3, h1 is ~0.5 and
0.65 km, respectively (h2 and h3 at σ = 20 MPa). If the mantle
strength increases to 50 and 100 MPa at the same fluid
densities, the critical size will be h1 – h3 at σ = 50–100 MPa
(Fig. 2). That is, the maximum thicknesses of fluid lenses at
these strength parameters of the lower mantle and the fluid
densities of 1–3 g/cm3 do not exceed 3.4 km (σ = 100 MPa).
Thus, the results of calculation suggest accumulation of
fluid lenses up to 3.4 km in height at the core–mantle
boundary. After the outburst, they transform into vertical
fracture cavities with a height much more than the critical one,
but their sizes can hardly be estimated.
During the accumulation at the core–mantle boundary, a
fluid experiences different chemical and thermodynamic conditions, passing from the metallic oxide core into the mantle,
and, most likely, interacts with the mantle material, causing
melting and dissolution of the components. Then, ascending
through the mantle, the fluid undergoes changes as a result of
the total-pressure and temperature decrease, as well as adiabatic expansion. At the same time, the exothermic oxidation
of the fluid can compensate for the heat loss related to the
adiabatic expansion and temperature decrease. It is impossible
to establish in detail the intricate evolution of this system. It
is clear that during the ascent, the fluid heats up and forms
the trunk part of the plume, which is detected by seismic
tomography as a slow-mantle zone. Here, fluid fracture
cavities ascend, reaching the lithosphere base, much harder
than the sublithospheric mantle (Fig. 3). The heating-up and
impact of the fluid (plume), however, cause the thinning and
softening of lithosphere, followed by its melting (Corti et al.,
2003). Figure 3 (on the left) shows how the lithosphere
strength changes under plume impact. The right part presents
the section of lithosphere heated by mantle fluids (interpretation of the strength plots). Numerals 1–3 mark the process
stages. In the case of a four-layered lithosphere, fracture
cavities with a fluid cannot overcome the barrier at a depth
of 55 km at stage 1. At stage 2, the lithosphere softens as a
result of heating-up, and the fluid can rise to the next height
level (35 km). At stage 3, the continuing heating-up and
softening of the lithosphere favor the fluid ascent up to the
crust. The arrows in the right part of the figure show a fluid
flow, which spreads laterally when reaching the hard lithosphere.
Sublithospheric evolution of fluid
There are numerous data on the discovery of mantle fluid
components in the hydrosphere, but there is no information
about the direct outlet of hot mantle fluids. This means that
the proposed mechanism of fluid transport breaks down as the
fluid approaches the lithosphere, which is due to the significantly higher strength of the latter as compared with the ductile
mantle. More simply, the ascending fluid cavities stop at the
strength barrier near the lithosphere base (Figs. 3 and 4)
because of the insufficiently high EP, which, as shown above,
depends on their vertical extension and the density of fluid in
the cavities. The process of fluid cavity ascend through the
mantle is schematically shown in Fig. 4. At Hcr, the EP in the
fluid lens increases considerably to cause fluid fracturing (by
analogy with hydraulic fracturing) of the enclosing mantle
N.S. Zhatnuev / Russian Geology and Geophysics 57 (2016) 1135–1142
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strength. This favors the rapid movement of the fluid cavity.
Nevertheless, reaching the hard lithosphere, the lens cannot
break through it, but the EP within the lens is high enough to
cause a horizontal fluid fracturing and spreading of the fluid
throughout the softer asthenospheric mantle (Fig. 4b).
Plume-related magma formation
Fig. 4. General scheme of fluid accumulation in lenses at the core–layer D″
boundary and its following outburst into the mantle, attainment of the hard
lithosphere, and spreading beneath it. a, Stages 1–9 of fluid accumulation and
outburst at the core–mantle boundary; b, stages 1–5 of fluid lens stop at the base
of the hard lithosphere and their lateral spreading.
layer. As a result, the lens, which was initially of horizontal
strike, transforms into a vertical cavity and ascends (Fig. 4a).
The height of the cavity is much more than Hcr, and,
correspondingly, the EP is much higher than the mantle
Letnikov (2003) showed that neither the recent nor the
Mesozoic continental geotherms intersect with the solidus of
mantle rocks. This indicates that melting of mantle rocks is
hardly possible without an additional impact (a local temperature increase or the appearance of a water fluid in the system)
on the continental mantle. As shown above, plume makes a
thermal or fluid impact (in the form of fluid cavities ascending
from the core through the mantle) on both the continental and
the oceanic lithosphere. The reduced fluids separated from the
core during the cavity ascent are oxidized on oxides of metals
of variable valence, producing water and CO2 and generating
heat in the exothermic oxidation reactions. As well known
(Kadik et al., 1971), water significantly decreases the solidus
and liquidus temperatures of magmas.
This can be shown schematically on a diagram (Fig. 5). As
a water fluid carrying heat inflows into the system, the solidus
and liquidus of anhydrous melt shift to the left, to lower
temperatures, and the geotherm shifts to the right, toward the
solidus. This results in a mantle magma chamber, which
expands both laterally and vertically as the plume fluid
inflows. The lateral expansion is predominant, which is due
Fig. 5. Schematic diagram of melting-out of mantle magmas during the inflow of water fluid and heat from plume (on the right) and evolution of a mantle magma
chamber (on the left). AS and AL are the anhydrous solidus and anhydrous liquidus of mantle rocks, respectively (the zone between them is hatched). HS and HL are
hydrous solidus and hydrous liquidus, respectively (the zone between them is shaded). Dotted lines mark the degree of rock melting between the HS and HL
(0–100%). White arrows show the shift of the solidus and liquidus from anhydrous to hydrous under water input, and black arrows (at the bottom), the shift of the
geotherm under heat input. Dashed lines on the diagram depict the degree of melting from core to periphery, and arrows at its bottom show a flow of hot plume fluid.
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N.S. Zhatnuev / Russian Geology and Geophysics 57 (2016) 1135–1142
Fig. 6. Height of magma chamber vs. excess pressure diagram (on the left) and schematic evolution of the chamber during its growth (on the right). p1–p7 are the
excess pressures in the apical part of the chamber with heights h1–h7 at evolution stages 1–7.
to the strength of the overlying lithosphere. This process is
accompanied by the increase in the degree of melting of
mantle rocks.
The prolonged thermal impact of plume, however, leads to
the thinning and strength degradation of the lithosphere (Corti
et al., 2003) and to the lateral expansion of the magma
chamber and increase in its height, which finally reaches a
critical value. The concept of a critical height, described above
for fluid lenses, is also true for magma chambers (Zhatnuev,
2010). As for fluid lenses, a critical height is determined by
the difference in the densities of the enclosing medium and
magma, which governs the EP in the apical part of the
chamber (Fig. 6). If the EP exceeds the strength of the
enclosing medium (σ), this causes magma fracturing (by
analogy with hydraulic fracturing), and magma begins to
intrude in the direction of pressure decrease (upward). This
process is probably very fast because it is developed on the
background of a rapid increase in the height of the magma
column, decrease in the total (lithostatic) pressure, and EP
increase. Figure 6 presents a schematic diagram showing the
stepwise evolution of the magma chamber during the medium
melting. Here, each height of the chamber (h1–h7) corresponds
to a certain EP (p1–p7). In this series of pressures, pcr
corresponds to the strength of the enclosing rocks. At stages
1–3 (on the right), the magma chamber expands as a result of
melting without magma fracturing. At stage 3, with the
chamber height hcr, the EP reaches pcr exceeding the strength
of the enclosing rocks, which leads to fracturing and intrusion
of magma. At stages 4–7, with the chamber heights h4–h7,
rapid magma fracturing gives rise to a magma conduit. During
the conduit formation, a self-developing increase in the height
of the magma column and, accordingly, EP in its head take
place. The magma fracture propagates in the direction of the
least resistance, i.e., vertically upward, as a result of the
Fig. 7. EP diagram for a peridotitic-magma chamber in comparison with lithosphere strength diagrams (hatched). a, EP for magma with CH2O = 0, 4, and 8 wt.% in
the case of young four-layered lithosphere I, thinned three-layered lithosphere II, and oceanized lithosphere III, after Corti et al. (2003). b, Magnified fragment of the
diagram, depicting critical heights (h1 and h2) necessary for the outburst of magma of different densities depending on water content. Small numerals at the horizontal
axes show the EP corresponding to magma outburst, and numerals at the vertical axes are the heights of magma chamber and magma column. Schematic models for
magma chambers 1 and 2 are also given. Arrows show a mantle fluid flow. For other explanations, see the text.
N.S. Zhatnuev / Russian Geology and Geophysics 57 (2016) 1135–1142
1141
Fig. 8. Scheme of plume formation and plume magmatism. a–e, The sequence of plume formation stages (not to scale). Hcr is the critical height of lens necessary for
its outburst into the mantle. mcr is the critical thickness of magma reservoir necessary for its outburst. For other explanations, see the text.
accelerating EP increase in the head of the column and finally
transforms into a relatively narrow, isometric in plan, magma
conduit forming through the “abrasive” action of the moving
magmatic melt.
Figure 7 presents diagrams of EP calculated for sublithospheric peridotitic magma with different contents of water
(different densities), together with diagrams of the lithosphere
strength (Corti et al., 2003). The calculations were made using
the densities of peridotitic magma with different water contents (Ohtani and Zhao, 2009) and the densities of the
lithosphere and crust (Ohtani and Zhao, 2009; Ringwood,
1979).
The diagram b (Fig. 7), a magnified fragment of the
diagram a, shows that peridotitic magma with 8 wt.% H2O in
a chamber with height h1 = 2.8 km can cause hydraulic fracturing of the mantle at EP = 11 MPa and a depth of 1117.8 km.
The horizontal dimensions and volume of the magma chamber
cannot be evaluated; they can vary over a wide range of values
and depend on the lateral spreading of fluid forming the plume
head. According to Dobretsov’s (2005) estimates, the plume
head can spread laterally for more than 1000 km. At the higher
density of magma containing 4 wt.% H2O, the EP necessary
for upward magma rush increases to 13 MPa, and the critical
height of the magma chamber, to 3.6 km (h2 = 120 km –
116.4 km = 3.6 km). The anhydrous peridotitic magma cannot
rush to the surface (its EP in the apical part of the chamber
is not beyond the hatched field of the diagram). That is, the
EP does not exceed the strength of the enclosing rocks. The
heights of hydrous-magma columns increase during magma
outburst, as well as the EP (thin arrows along the plots on the
diagrams). However, as the magma column (8 wt.% H2O)
reaches a depth of 71.5 km, the trajectory of the EP plot
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intersects with the mantle strength plot at point 1 (Fig. 7a).
This indicates that the EP of magma (280 MPa) is insufficient
for break through the hard young four-layered lithosphere
(Corti et al., 2003). This is still more impossible for less
hydrous (i.e., denser) magmas, but nothing hampers horizontal
intrusion of magma and formation of a lenticular plume head.
As shown by Corti et al. (2003), the prolonged thermal
impact of the anomalous mantle (plume) softens the lithosphere, and its strength evolves from state I to states II and
III (Fig. 7a). Later, the softened lithosphere will favor magma
breakthrough to the surface. It is beyond doubt that the magma
chamber will ascend synchronously with heating and will be
mushroom-shaped or lenticular.
Conclusions
A general model for the formation and evolution of
transmantle fluid flows, mantle plumes, and plume magmatism
can be presented as follows (Fig. 8). In a sufficiently vast area
of the core surface the sources of gas form fluid lenses
merging into larger ones during their growth (Fig. 8a, b). As
the lens reaches a critical size (Hcr), it bursts out and
transforms into a fracture, which can carry all accumulated
fluid away (Fig. 8b). After the removal of this fracture,
formation of fluid lenses can be resumed (Fig. 8c). During the
ascent, the fluid fracture cavities break into smaller fragments
until they reach the particular size (similarly to the break of
large gas bubbles floating in liquid). The ascending fluid
continuously interacts with the enclosing mantle to provoke
partial melting of silicates, and the dimensions of the cavities
evolve as a result of the decompression and cooling of their
contents. The prolonged existence of this flow causes heating
and decompression of the mantle and formation of the plume
trunk (Fig. 8d). When approaching the hard lithosphere, the
fracture cavities stop because the EP is low enough for their
break through it. However, the EP is sufficient for the lateral
spreading of cavities through fluid fracturing, which is accompanied by the heating of the lithospheric and sublithospheric
mantle by the hot hydrous fluid and by its metamorphism and
melting. As a result, the mushroom-shaped head of plume
forms. It is a zone of melting of the mantle, which interacts
with the lithosphere and partly assimilates and softens it. The
lithosphere of type 1 transforms into the lithosphere of types
2 and 3 (Fig. 3) with a significant loss of strength, which will
favor a breakthrough of the magma chamber to the surface as
it reaches the critical thickness mcr (Fig. 8e). The mechanism
of magma chamber breakthrough when the critical height is
reached was considered earlier (Zhatnuev, 2010). The large
volume of accumulated magma can lead to its mass intrusion
and outflow. The catastrophic outflows of the Siberian Platform and other plateau basalts might have proceeded in the
same way.
References
Burke, K., Steinberger, B., Torsvik, T.H., Smethurst, M.A., 2008. Plume
generation zones at the margins of Large Low Shear Velocity Provinces
on the core–mantle boundary. Earth Planet. Sci. Lett. 265 (1–2), 49–60.
Campbell, I.H., 2005. Large Igneous Provinces and the mantle plume
hypothesis. Elements 1, 265–269.
Corti, G., Bonini, M., Conticelli, S., Innocenti, F., Manetti, P., Sokoutis, D.,
2003. Analogue modelling of continental extension: a review focused on
the relations between the patterns of deformation and the presence of
magma. Earth Sci. Rev. 63, 169–247.
Dobretsov, N.L., 2005. 250 Ma large igneous provinces of Asia: Siberian and
Emeishan traps (plateau basalts) and associated granitoids. Russian
Geology and Geophysics (Geologiya i Geofizika) 46 (9), 867–869
(870–890).
Dobretsov, N.L., 2008. Geological implications of the thermochemical plume
model. Russian Geology and Geophysics (Geologiya i Geofizika) 49 (7),
441–454 (587–604).
Griffiths, R.W., Campbell, I.H., 1990. Stirring and structure in mantle starting
plumes. Earth Planet. Sci. Lett. 99 (1–2), 66–78.
Kadik, A.A., Lebedev, E.B., Khitarov, N.I., 1971. Water in Magmatic Melts
[in Russian]. Nauka, Moscow.
Korzhinskii, D.S., 1952. Granitization as magmatic replacement. Izv. AN
SSSR. Ser. Geol., No. 2, 56–59.
Korzhinskii, D.S., 1968. Transmagmatic flows of subcrustal solutions and
their role in magmatism and metamorphism, in: The Earth’s Crust and
Upper Mantle. Int. Geol. Congress, 23rd Session. Abstr. Soviet Geologists.
Problem 1 [in Russian]. Nauka, Moscow, pp. 69–74.
Kuz’min, M.I., Yarmolyuk, V.V., Kravchinsky, V.A., 2011. Phanerozoic
within-plate magmatism of North Asia: Absolute paleogeographic reconstructions of the African large low-shear-velocity province. Geotectonics
45 (6), 415–438.
Kuznetsov, Yu.A., Izokh, E.P., 1969. Geologic evidence for intratelluric heat
and matter flows as agents of metamorphism and magma formation, in:
Problems of Petrology and Genetic Mineralogy [in Russian]. Nauka,
Moscow, Vol. 1, pp. 7–20.
Letnikov, F.A., 2001. Ultradeep fluid systems of the Earth and problems of
ore formation. Geol. Ore Deposits 43 (4), 259–273.
Letnikov, F.A., 2003. Magma-forming fluid systems of continental lithosphere. Geologiya i Geofizika (Russian Geology and Geophysics) 44 (12),
1262–1269 (1219–1225).
Letnikov, F.A., Dorogokupets, P.I., 2001. The role of superdeep fluid systems
of the Earth’s core in endogenic geological processes. Dokl. Earth Sci.
378 (4), 500–502.
Morgan, W.J., 1971. Convective plumes in the lower mantle. Nature 230,
42–43.
Ohtani, E., Zhao, D., 2009. The role of water in the deep upper mantle and
transition zone: dehydration of stagnant slabs and its effects on the big
mantle wedge. Russian Geology and Geophysics (Geologiya i Geofizika)
50 (12), 1073–1078 (1385–1392).
Ovchinnikov, L.N., 1973. Intratelluric solutions, magmatism, and ore formation, in: Problems of Magmatic Geology [in Russian]. Nauka, Novosibirsk,
pp. 318–329.
Puchkov, V.N., 2009. The controversy over plumes: Who is actually right?
Geotectonics 43 (1), 1–17.
Ringwood, A.E., 1979. On the Origin of the Earth and Moon. Springer-Verlag,
New York.
Wilson, J.T, 1963. A possible origin of the Hawaiian Islands. Can J. Phys.
41, 863–870.
Zhatnuev, N.S., 2005. Fissure fluid systems in the ductile deformation zone.
Dokl. Earth Sci. 404 (7), 1014–1017.
Zhatnuev, N.S., 2010. The dynamics of deep magmas. Dokl. Earth Sci. 430
(2), 176–180.
Zonenshain, L.P., Kuz’min, M.I., 1983. Intraplate magmatism and its
significance for understanding the Earth’s mantle processes. Geotektonika,
No. 1, 28–45.
Zonenshain, L.P., Kuz’min, M.I., 1992. Paleogeodynamics [in Russian].
Nauka, Moscow.
Editorial responsibility: M.I. Kuz’min