Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling
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Інститут геофізики ім. С.I. Субботіна НАН України
2010
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| Цитувати: | Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling / O. Parphenuk // Геофизический журнал. — 2010. — Т. 32, № 4. — С. 128-129. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-1021352016-06-11T03:01:49Z Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling Parphenuk, O. 2010 Article Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling / O. Parphenuk // Геофизический журнал. — 2010. — Т. 32, № 4. — С. 128-129. — Бібліогр.: 8 назв. — англ. 0203-3100 http://dspace.nbuv.gov.ua/handle/123456789/102135 en Геофизический журнал Інститут геофізики ім. С.I. Субботіна НАН України |
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Parphenuk, O. |
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Parphenuk, O. Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling Геофизический журнал |
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Parphenuk, O. |
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Parphenuk, O. |
| title |
Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
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Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
| title_full |
Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
| title_fullStr |
Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
| title_full_unstemmed |
Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
| title_sort |
granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling |
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Інститут геофізики ім. С.I. Субботіна НАН України |
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2010 |
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http://dspace.nbuv.gov.ua/handle/123456789/102135 |
| citation_txt |
Granitoids localization in collisional overthrust structures subject to thermal conditions-numerical modeling / O. Parphenuk // Геофизический журнал. — 2010. — Т. 32, № 4. — С. 128-129. — Бібліогр.: 8 назв. — англ. |
| series |
Геофизический журнал |
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2025-07-07T11:53:41Z |
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2025-07-07T11:53:41Z |
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1836988999519961088 |
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Granitoids localization in collisional overthrust structures
subject to thermal conditions-numerical modeling
O. Parphenuk, 2010
Institute of Physics of the Earth, RAS, Moscow, Russia
oparfenuk@mail.ru
High temperature metamorphism and widespread
granite magmatism are common peculiarities of many
ancient continental collision structures. Deeply ero-
ded areas of the Archean and Proterozoic continental
shields formed in the process of tectonic evolution in-
cluding horizontal shortening and collision expose at
the surface middle to the lower crust rocks uplifted by
overthrusting from the depths of 20—40 km. This phe-
nomenon seems to be valid also for modern collision
zones. The massive layer of granite melt approximately
of 10 km thickness is observed at 10—15 km depth
by seismic methods in the resent orogens such as
the Himalayas and Caucasus [Rosen, Fedorovsky,
2001]. The Palaeozoic Variscan orogen in Europe is
characterized by large volumes of felsic granites in-
truded during HT-LP metamorphism and exposed in
deeply eroded parts of the Variscan belt (South Bohe-
mian Batholit) [Gerdes et al., 2000].
Fundamental features of collision zones reflect
the effect of the main tectonic event — horizontal
shortening in compression setting, collision of two
continental plates accompanied by the thickening
of the crust and the surface uplift. Extensive deve-
lopment of horizontal and oblique motions of crus-
tal plates and blocks leads to the disturbances in
the thermal regime, heat flow, the surface and Moho
topography. The main petrologic mark of such colli-
sion is granite melt generated at different depth’s
levels and exposed at the surface as a result of the
denudation and uplift.
Thermal-kinematic model of continental collision
calculates pressure, velocity and temperature fields
and includes horizontal shortening, brittle overthrus-
ting in the upper crust compensated by the lower
crust viscous flow and erosion of the thickened crust.
Finite-element 2D modeling is used to examine the
thermal and kinematic conditions for high-tempera-
ture metamorphism and the depth and timing of
crustal melting in the case of rheologically layered
lithosphere [Parphenuk et al., 1994; Parphenuk,
2005]. The thermal effects during collision process
and postorogenic stage are studied.
Calculation of lithospheric temperature field is
based on crustal thickening by overthrusting with
dip angle of faulting of 15—30 and shortening rate
in the range of 0.5—2 cm/y. Total amount of hori-
zontal shortening is 100 km. We assumed that ero-
sion and concurrent sedimentation begins after an
additional crustal portion of a substantial thickness
is exposed. The equation of energy conservation is
solved for the case of Lagrange coordinates with
material time derivative [Turcotte, Shubert, 1985]:
iiii HT
Dt
DT
c 2
,
where c is specific heat, is density, is the ther-
mal conductivity, and H is the heat generation rate.
The model consists of three layers: 20 km brittle
upper crust (i=1), 20 km ductile lower crust (i=2)
and 80 km lithospheric mantle (i=3) with different
thermal, kinematic and rheological parameters.
The calculations show the possibility of the par-
tial melting and granite melt generation subjected
to the main thermal parameters of the model — the
initial temperature distribution (heat flow higher than
60 mW/m2) and radiogenic heat production. The
temperature increase can be fairly significant (up to
250 C) at depths level of 10—30 km confirming the
idea of crustal origin of the continental collisional
granites. The partial melting (wet granite solidus)
starts in the thickened crust in the vicinity of thrust
fault and widens in the direction of thrusting and to
the lesser depths. Maximum temperature increase
along the fault zone is 300 C.
2D collision model confirms the observation of a
wide range of PT-conditions over short distances in
metamorphic belts [Chamberlain, Karabinos, 1987].
As a result of upward motion along the fault, the
additional loading redistribution in the course of ero-
sion, and the viscous compensation at the level of
the lower crust, PT-histories will be completely differ-
ent for the points along the thrust fault. For example,
for the convergence and erosion rates of 0.5 and
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0.025 cm/y, respectively, maximum erosion level of
~9 km of uplifted crust is reached at 45 Ma after
the onset of collision (at postcollisional stage). The
material will be transported from a depth of 20 km
to a depth of about 5 km while the rocks that were
initially located at a depth of 3.5 km will experience
a rather complicated PT-evolution. At the postcolli-
sional stage (after 20 Ma of shortening) the com-
pressional regime is changed by extension with very
low velocities.
Local effect may result from the frictional hea-
ting along the slip zone during the overthrusting.
The frictional heat production is proportional to the
product of the shear stress across the slip plane,
the velocity of obduction and coefficient of friction.
The additional heating can rise the temperature by
50—150 C at 10—20 Ma in the vicinity of slip zone
in the case of horizontal shortening rate of up to 4 cm/
y and thrust sheet thickness up to 20 km [Brewer,
1981]. This local and moderate additional heating
(in comparison with crust thickening effect) is much
less in the case of slower thickening.
The following set of parameters is critical to initiate
crustal melting and granite formation: initial tempera-
ture distribution with heat flow density value higher
than 60 mW/m2, relatively high radiogenic heat pro-
duction, slow crustal thickening (0.5—1 cm/y for 10—
20 Ma) and slow exhumation. The results of the mo-
deling confirm other model estimates [England, Th-
ompson, 1984; Gerdes et al., 2000].
The research is supported by the Russian Foun-
dation for the Basic Research (09—05—01032).
References
Brewer J. Thermal effects of thrust faulting // Earth Pla-
net. Sci. Lett. — 1981. — 56. — P. 233—244.
Chamberlain C. P., Karabinos P. Influence of deforma-
tion on pressure — temperature paths of meta-
morphism // Geology. — 1987. — 15. — P. 42—44.
England P., Thompson A. B. Pressure-temperature-
time paths of regional metamorphism. Part I: Heat
transfer during the evolution of regions of thickened
continental crust // J. Petrology. — 1984. — 25. —
P. 894—928.
Gerdes A., Worner G., Henk A. Post-collisional granite
generation and HT-LP metamorphism by radiogenic
heating: the Variskan South Bohemian Batholith // J.
Geolog. Soc. — 2000. — 157. — P. 577—587.
Parphenuk O. I. Thermal regime of collisional over-
thrust structures // Izvestiya. Phys. Solid Earth. —
2005. — 41, ��3. — P. 238—240.
Parphenuk O. I., Dechoux V., Mareschal J.-C. Finite-
element models of evolution for the Kapuskasing
structural zone // Can. J. Earth Sci. — 1994. — 31.
— P. 1227—1234.
Rosen O. M., Fedorovsky V. S. Collisional granitoids
and the Earth crust layering. — Moscow: Nauchnyi
Mir, 2001. — 188 p. (in Russian).
Turcotte D., Shubert J. Geodynamics. — Moscow: Mir,
1985. — I. — 376 p. (in Russian).
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