1480
ISSN 1028-334X, Doklady Earth Sciences, 2006, Vol. 411A, No. 9, pp. 1480–1484. © Pleiades Publishing, Inc., 2006.
Original Russian Text © O.P. Polyansky, V.V. Reverdatto, 2006, published in Doklady Akademii Nauk, 2006, Vol. 411, No. 5, pp. 803–807.
The zonal contact-metamorphic aureoles around
intrusions provide insight into the thermal impact of
magma on country rocks. In [1–3], the issue of conduc-
tive heating of rocks without the participation of fluid
was scrutinized. The duration of cooling and temporal
temperature distribution versus distance from the con-
tact were estimated. However, in many cases, the con-
ductive heat transfer turns out to be insufficient to form
thick complexes of thermally metamorphosed rocks. As
was shown for a number of geological and theoretical
models, convective heat-and-mass transfer near mag-
matic bodies is of great importance [3–5]. The country
rocks of intrusions in the Noril’sk ore district at the
northwestern margin of the Siberian Craton are one
such case. In this communication, mathematical mod-
eling is used to describe the heat redistribution and fluid
convection in the volcanosedimentary sequence at the
contact with the Talnakh ore-bearing intrusion. The
objective of this study was to simulate the temperature
and hydrodynamic fields that would fit the location of
isotherms and isograds, as well as the distribution of
metasomatic rocks near the intrusion.
The problem of modeling of heat transfer and con-
vective flows of a two-phase fluid is solved in the 2D
setting in the Cartesian coordinate system on the basis
of time-dependent equations of nonisothermal hydro-
dynamics with account of vapor–liquid phase transi-
tion. The following assumptions are accepted: (1) the
Darcy relationship is fulfilled for two-phase flow; (2)
effects of capillary pressure are ignored; (3) all phases,
including matrix (solid framework of rock), liquid, and
gas, are considered to be in the state of local thermal
equilibrium; (4) mechanical reaction of the solid rock
framework to the fluid motion is negligibly small; and
(5) metasomatic processes are beyond the scope of con-
sideration. The problem boils down to the solution of a
system of equations of energy-and-mass balance for
convection of two-phase liquid through a porous
medium [6]. The state equation of fluid
P
=
P
(
T
,
ρ
)
that
controls the interrelation of thermodynamic variables
(pressure, temperature, and density) closes the system
of equations. The Haar–Gallaher–Kell equation, which
describes the properties of pure aqueous fluid within a
temperature range of 0–1200
°
C and a pressure interval
of 1–10 kbar, was used in calculations. The computing
algorithm is built on the basis of an implicit finite-dif-
ference scheme with iterations by the Newton–Raph-
son method realized in the Hydrotherm software [7, 8].
To solve the problem of convective heat-and-mass
transfer near the Talnakh intrusion at the boundary of
the Yenisei–Khatanga sedimentary basin at the north-
western margin of the Siberian Craton, we elaborated a
geological model of this district. An area at the bound-
ary of the Kharaelakh syncline and Kayerkan–Pyasina
anticline is considered. The model vertical section is
oriented across the Talnakh intrusive body and the
Noril’sk–Kharaelakh fault, which represents the
boundary normal fault in the Kharaelakh syncline. The
modeled fragment of the basin is limited in depth by the
upper 5.5 km of volcanosedimentary cover. The geo-
logical structure of the Upper Talnakh intrusion and its
framework are shown in Fig. 1 on the basis of the data
reported in [9, 10] and simplified for purposes of math-
ematical modeling. According to the geological and
geophysical data, the model section consists of the fol-
lowing rocks (from bottom to top): (1) Devonian car-
bonate rocks (thickness >1600 m, porosity
n
= 0.025,
permeability
k
= 2 ·
10
–17
m
2
, thermal conductivity
λ
=
2.5 W/(m · K), and density
ρ
= 2850 kg/m
3
[11]);
(2) Middle Carboniferous–Upper Permian coaliferous ter-
rigenous rocks of the Tunguska series (thickness 680 m,
n
= 0.07,
k
= 5
·
10
–15
m
2
,
λ
= 1.66–4.0,
ρ
= 2450
),
which are country rocks of the Talnakh intrusion (
n
=
0.004;
k
= 10
–18
m
2
;
λ
= 3.1,
ρ
= 2650
); and (3) Upper
Permian–Middle Triassic volcanic rocks of trap associ-
ation (thickness 3200 m,
n
= 0.03,
k
= 10
–17
–5
·
10
–15
m
2
,
λ
= 3.0,
ρ
= 2750
). The thickness of the tuff and lava
Contact Metamorphism and Metasomatism
near the Talnakh Intrusion: Fluid Convection and Heat Transfer
Modeling on the Basis of the Finite-Difference Method
O. P. Polyansky and
Academician of the RAS
V. V. Reverdatto
Received July 4, 2006
DOI:
10.1134/S1028334X06090339
Institute of Geology and Mineralogy, Siberian Division,
Russian Academy of Sciences, pr. akademika Koptyuga 3,
Novosibirsk, 630090 Russia; e-mail: pol@uiggm.nsc.ru
GEOCHEMISTRY