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lameubiquityMécanique

21 févr. 2014 (il y a 3 années et 8 mois)

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Geothermics of the

Pannonian basin

A talk in the frame of the Tibor
Mendöl Workshop

Lecturer: László Lenkey

Fundamentals of geothermics


Geothermal gradient = grad T =

T ~

T
z

= dT/dz ~ ΔT/Δz


Heatflow density (heat flow), q=
-

T ~ q
z
=
-


dT/dz~
-

ΔT/Δz, where


is the
thermal conductivity of rocks


Heat transport equation:




A
T
T
v
c
t
T
c










Thermal lithosphere

Herein et al., 2008

Ra=10e6

Ra=10e7

2D spherical shell models of thermal convection in the mantle

Thermal lithosphere

Herein et al., 2008

Thermal lithosphere

Geotherms in the mantle

Schubert et al., 2001

Definition of the lithosphere

Lithosphere=

(Thermal Boundary

Layer, TBL)


Thickness of the lithosphere in
Europe

from Artemieva et al. 2006

Thickness of the lithosphere in
Europe

from Artemieva et al. 2006

Heatflow in Europe

Pollack et al. 1993

Artemieva 2003

Thickness of the thermal lithosphere

Geothermal conditions in Hungary


Geothermal Database of Hungary (Dövényi,
1994)


4477 wells



deeper than 200 m



temperature higher then 30
°
C



all wells before 1993


12 000 temperature measurements


Automatic correction of temperatures


Lithology of the well


Thermal conductivity data and trends



Geothermal database

Interpolation, heatflow


Temperature corrections


Bottom hole temperature


Wells test


Outflowing water T


Calculation of heatflow

(condition: constant heatflow)





Interpolation of T


temperature [
°
C]

depth [m]

Thermal conductivity [W/mK]

MAKO
-
2

Measured T

Corrected

temperature

Thermal
conductivity

Interpolated
temperature

lithology

0
1




i
i
M
j
j
j
T T
q
h
k
For 1 layer:


 

T
q k
z
0
1
( )

 

M
j
z
j
j
h
T z T q
k
Number of temperature measurements in wells


EOV X

EOV Y

vagy több

Kutankénti mérések száma

1db

3071

db

2db

648

db

3db

335

db

4db

190

db

5 db és több

233

db

Összesen:

4477

db

(Horváth et al. 2005: Geodynamic atlas of the Pannonian basin)


Heat flow in the Pannonian basin and surrounding areas

Processes influencing heatflow




Volcanic activity (e.g. Hargita)


Groundwater flow (e.g. Transdanubian Central
Range)


Sedimentation/erosion (e.g. Makó trough)


Variation of thermal conductivity in 2D/3D
(topography of the basement of the sediments e.g.
Makó trough, Transylvanian basin)


Tectonics


Power of thermal springs at the feet of the
Transdanubian Central Range

(Horváth et al. 2005: A Pannon
-
medence geodinamikai atlasza)


Heat flow in the Pannonian basin and surrounding areas

Groundwater, helium and heat transport
modell along a section in the Great
Hungarian Plain


Cserepes and Lenkey, 1999

1 km
3 km
5 km
7 km
A NEOGÉN ÉS KVARTER ÜLEDÉKEK VASTAGSÁGA
0
100
200
300
400 km
Thickness of Neogene and Quarternary sediments

Sedimentation
-

model


A thick and cold sediment layer is deposited at the
surface



Parameters of the
model
:


Thickness of the
layer


Time of
sedimentation


Time passed since
deposition

Z

T

T

T
0

T
0

21
20
19
18
17
16
15
14
13
22
23
24
25
26
27
28
50
49
48
47
46
45
44
Prága
Budapest
Bécs
Beograd
100
200
300
400 km
0
CSEH
MASSZIVUM
KELETI
ALPOK
D
I
N
A
R
I
D
Á
K
NYUGATI
KÁRPÁTOK
K
Á
R
P
K
E
L
E
T
I
Á
T
O
K
KÁRPÁTOK
D
É
L
I
ERDÉLYI
KÖZÉP-HG.
ALFÖLD
KISALFÖLD
BÉCSI
MEDENCE
ERDÉLYI
MEDENCE
NEOGÉN
KVARTER
ÜLEDÉKEK
FLYSCH ÖV
PIENINY KLIPPEN
ÖV
NEOGÉN
VULKÁNOK
MOLASSZ
PRE-TERCIER
ALJZAT
Bucuresti
D
A
N
U
B
E
T
I
S
Z
A
D
R
A
V
A
Pozsony
Zagreb
Ljubljana
10.5
8.2
6.3
5.5
A PANNON-MEDENCE FELTÖLTŐDÉSE
Vakarcs et al., 1994 után
Infill of the Pannonian basin

HŐÁRAMDEFICIT A NEOGÉN ÜLEDÉKKÉPZŐDÉS MIATT
21
20
19
18
17
16
15
14
13
22
23
24
25
26
27
28
50
49
48
47
46
45
44
100
200
300
400 km
0
CSEH
MASSZIVUM
KELETI
ALPOK
D
I
N
A
R
I
D
Á
K
NYUGATI
KÁRPÁTOK
KÁRPÁTOK
D
É
L
I
BÉCSI
MEDENCE
ERDÉLYI
MEDENCE
FLYSCH ÖV
PIENINY KLIPPEN
ÖV
NEOGÉN
VULKÁNOK
MOLASSZ
PRE-TERCIER
ALJZAT
D
A
N
U
B
E
T
I
S
Z
A
D
R
A
V
A
Lenkey, 1999
Heatflow deficit due to sedimentation

ÜLEDÉKKÉPZŐDÉSRE KORRIGÁLT HŐÁRAM
0
100
200
300
400 km
Lenkey et al., 2002
Heatflow corrected for sedimentation

Transylvanian basin:

variation of heat flow due to variation of the
thermal conductivity of rocks

Thermal model of lithospheric extension

(Horváth et al. 2005: Geodynamic atlas of the Pannonian basin

Thickness of the lithosphere in the Pannonian basin

Subsidence history

Subsidence
history off shore
eastern cost of
North America

Subsidence history

Summary


Heat flow is an important geodynamic parameter


Large scale variation in heat flow are caused by
tectonic processes


Small scale variations are due to groundwater
flow, volcanism, variations in thermal
condcutivity and heat production


High heat flow in the Pannonian basin is a result
of lithospheric extension occurred 20
-
15 Ma


The extension of the lithosphere was not
uniform: the mantle part was more thinned than
the crust