Geo-Mar Lett (2003) 23: 258–268
DOI 10.1007/s00367-003-0152-z
O R I GI N A L
S. Planke Æ H. Svensen Æ M. Hovland Æ D. A. Banks
B. Jamtveit
Mud and fluid migration in active mud volcanoes in Azerbaijan
Received: 7 February 2003 / Accepted: 2 September 2003 / Published online: 23 October 2003
Springer-Verlag 2003
Abstract Mud volcanic eruptions in Azerbaijan normally last for less than a few hours, and are characterized by vigorous extrusion of mud breccias,
hydrocarbon gases, and waters. Recent fieldwork and
mapping on four active mud volcanoes show that
dormant period activity ranges from quiet to vigorous
flow of mud and fluids. Geochemical analyses of
expelled waters show a wide range in solute concentrations, suggesting the existence of a complex plumbing
system. The mud and fluids have a deep origin, but are
sometimes stored in intermediate-depth mud chambers.
A mixing model between deep-seated saline waters and
shallow meteoric water is proposed.
Introduction
Piercement structures, such as mud volcanoes and
hydrothermal vent complexes, are common in many
sedimentary basins. Hydrothermal vent complexes are
numerous in sedimentary basins on the NE Atlantic
margins and in the Karoo basin in South Africa
(Jamtveit et al. 2003). These vent complexes were formed
as a consequence of the intrusion of mafic melts in
sedimentary basins in late Paleocene and mid-Jurassic
times, respectively. In contrast, mud volcanoes are
formed by tectonic processes, e.g., by overpressure
S. Planke (&)
Volcanic Basin Petroleum Research (VBPR), Oslo Research Park,
0349 Oslo, Norway
E-mail: planke@vbpr.no
S. Planke Æ H. Svensen Æ B. Jamtveit
Physics of Geological Processes, University of Oslo, P.O. Box 1048
Blindern, 0316 Oslo, Norway
M. Hovland
Statoil, 4035 Stavanger, Norway
D. A. Banks
School of Earth Sciences, University of Leeds, Leeds, LS2 9JT, UK
buildup in compressional settings, or by maturation and
degassing of rapidly buried organic-rich sediments (e.g.,
Hedberg 1974; Higgins and Saunders 1974; Sjögren
1886; Brown 1990; Milkov 2000; Kopf and Behrmann
2000; Fowler et al. 2000; Kopf 2002).
The piercement structures will clearly have an
important impact on fluid migration in sedimentary
basins when they are formed (e.g., Dimitrov 2002).
However, it has been shown that they may also have an
important long-term impact on the fluid-flow history in
sedimentary basins (Svensen et al. 2003, this volume).
Currently, it is difficult to incorporate such piercement
structures in basin modeling theories, and they are thus
commonly ignored when studying fluid flow in sedimentary basins.
An important issue regarding mud volcanoes and
seeps is if the seep fluids have the same source during the
dormant and eruptive phases, and the degree of mixing
of deep waters (i.e., from mud reservoir level) with
shallow waters. Geochemical data from mud volcanoes
suggest that, even during dormant periods, water seeps
are sourced from the deep mud reservoir (e.g., Dia et al.
1999). Mixing between deep and shallow waters during
ascent is to be expected, and may be related to the
presence of intermediate-depth mud chambers (cf.
Cooper 2001). Thus, the waters expelled at mud volcanoes may represent complex mixtures of deep and
shallow waters, with chemistries affected by processes
like mineral dehydration, adsorption and desorption on
clay minerals, precipitation and dissolution, redox
reactions, and degradation of organic material (e.g.,
Lagunova 1976; You et al. 1993; Martin et al. 1996; Dia
et al. 1999; Kopf and Deyhle 2002).
The South Caspian Basin (Fig. 1) provides a unique
possibility to study mud volcanism and fluid flow in an
active pierced basin. More than 400 active mud volcanoes are present in this region, both onshore and offshore (Jakubov et al. 1971; Aliyev et al. 2002). These
mud volcanoes are commonly associated with hydrocarbon fields (e.g., Guliev and Feizullayev 1996; Fowler
et al. 2000), and may provide important channels for
259
Fig. 1 The distributions of active mud volcanoes in Azerbaijan
(Az). The numbered mud volcanoes are studied in this work.
Modified from Jakubov et al. (1971) and Nadirov et al. (1997)
petroleum migration (Katz et al. 2000; Guliyev 2002).
The aim of this paper is to document the main processes
of mud volcano eruptions, mud breccia emplacement,
and fluid migration based on fieldwork on four active
mud volcanoes in Azerbaijan and geochemical analysis
of seep waters from two of these.
Mud volcanic processes and terminology
Mud volcanism shows many similarities to magmatic
volcanism, and a substantial part of the terminology
used to describe volcanic processes and deposits (e.g.,
Sigurdsson 2000) can be applied to mud volcanoes and
mud volcanism. There is, however, also a separate
terminology related to mud volcanoes (e.g., Hovland
et al. 1997; Milkov 2000; Aliyev et al. 2002; Dimitrov
2002; Kopf 2002). Although the terminology of mud
volcanoes has become more rigorous and consistent
(e.g., Milkov 2000; Kopf 2002), there is still a need to
make a clearer distinction between the active and
dormant stages of mud volcanoes. The importance of
the active/dormant distinction is crucial when estimating gas and fluid fluxes from mud volcanoes, and
when determining their impact on the release of
methane to the atmosphere. What are commonly referred to as active mud volcanoes in the literature are
in many cases only manifestations of seep activity
during the dormant period (e.g., gryphons and salses).
Most of the flux estimates from mud volcanoes are
calculated from dormant volcanoes (see Dimitrov
2002). The bulk of the fluid and mass is, however,
released during eruptions (cf. Kopf and Deyhle 2002;
Dimitrov 2002), but quantitative measurements of
eruption parameters are scarce. According to Dimitrov
(2002), the integrated annual fluxes of methane from
mud volcanoes worldwide during eruptions are 7 times
(average value) higher than the seep activity in the
dormant periods. The estimated value for Azeri mud
volcanoes is a 16 times higher annual flux during
eruptions (Guliyiev and Feizullayev 1994, in Dimitrov
2002).
Mud volcanoes can be classified as active, extinct, or
buried, and mud volcanism may represent a major landbuilding process. A mud volcano eruption can be
explosive or effusive, and may occur both in subaerial
and subaqueous environments. Hydrocarbon gases are
commonly erupted. These gases may self-ignite, and up
to 1-km-high fire-columns have been observed during
mud volcanic eruptions in Azerbaijan (Aliyev et al.
2000). The erupted solid material is present as fall or
flow deposits. Breccia flows are commonly emplaced
during mud volcanic eruptions. These flows consist of
angular boulders and clasts (xenoliths) derived from the
country rocks that are cut by the plumbing system, being
embedded in a mud-dominated matrix.
Active mud volcanoes show a variable degree of
dormant activity. Many are quiet, with no surface seep
activity or ground deformation. However, seep activity
is common on many mud volcanoes, expelling muds,
liquids, and gases. The seep activity leads to the
formation of scenic features such as gryphons (<3 m
high, steep-sided cones extruding mud), mud cones
(<10 m high cones extruding mud and rock fragments),
salses (water-dominated pools with gas seeps), springs
(<0.5 m small, water-dominated outlets), burning fires,
scoria cones formed by heating of mud deposits during
the fires (e.g., Jakubov et al. 1971; Hovland et al. 1997;
Guliyev and Feizullayev 1997), and hydrocarbon
deposits (Higgins and Saunders 1974; Aliyev et al. 2002).
The seep activity is dominantly effusive, but small
explosive events do also occur.
South Caspian Basin
The South Caspian Basin is a Tertiary back-arc basin
with an up to 25–30 km thick sedimentary package (e.g.,
Guliyev and Feizullayev 1996; Abrams and Narimanov
1997; Devlin et al. 1999; Guliyev et al. 2002). The South
Caspian Basin was a depression from the mid Jurassic,
with deposition of marine sediments upon Lower
Jurassic oceanic crust formed during back-arc spreading
(Abrams and Narimanov 1997). Further collision in the
Alpine-Himalayan zone led to regional uplift in the
Miocene–Pliocene, with associated rapid deposition of
10 km of deltaic and lacustrine sediments in the South
Caspian region. Sedimentation rates during the Quaternary were as high as 2.4 km/106 years (Nadirov et al.
1997), and 5–8 km of sediments has been deposited the
last 5·106 years (Tagiyev et al. 1997).
The geothermal gradient in the South Caspian
Basin is low (10–18 C/km), providing hydrocarbon
maturation down to great depths (14 km to the onset
260
of the gas window; Abrams and Narimanov 1997;
Nadirov et al. 1997). The typically 1–2 km thick
Maykop Fm. is regarded as the major source of both
the extruded mud and the petroleum (Inan et al. 1997;
Fowler et al. 2000). However, mud breccias from the
mud volcanoes often contain clasts from formations
below the Maikop Fm., suggesting that some of the
mud may have an even deeper source (Inan et al.
1997). The Maikop Fm. is locally very deeply buried—it is located between 8.5- and 11-km depth offshore Baku, and at 5.5-km depth underneath the
offshore Shah Deniz structure (Fowler et al. 2000).
The mud reservoirs for the extrusive volcanism may
be as deep as 14 km, with intermediate mud chambers
at 2–4 km depth (Cooper 2001).
The rapid Miocene–Pliocene sedimentation and burial led to increased maturation of organic material,
created structural traps, and caused initiation of mud
volcanism (Abrams and Narimanov 1997). Almost 300
historic small and large mud volcano eruptions are
documented in Azerbaijan, occurring on 76 mud volcanoes (Aliyev et al. 2002). The mud volcanoes, and
associated hydrocarbon reservoirs, are often found
within large anticlines (Jakubov et al. 1971; Guliyev and
Feizullayev 1996; Narimanov et al. 1998; Fowler et al.
2000; Guliyev et al. 2002).
Materials and methods
Fieldwork was performed at four active mud volcanoes—Bakhar, Dashgil, Koturdag, and Lokbatan,
during October 2002 (Fig. 1). Two of the mud volcanoes, Bakhar and Dashgil, are good examples of mud
volcanoes with a high seep activity in the dormant
period. In contrast, the active Kotyrdag and Lokbatan
mud volcanoes are quiet, and recently eruptive
deposits and structures are well exposed. Finally, a
satellite vent 1 km west of the Bakhar mud volcano
was visited.
Detailed mapping of the Dashgil and Lokbatan
mud volcanoes was done using a Garmin etrex GPS
with a relative accuracy of four meters. Water samples
were collected from Dashgil and Bakhar, both from
salses, springs, and gryphons. Temperatures were
measured in-situ with a thermocouple thermometer.
Mud and water was separated by settling (to minimize
release of elements adsorbed to clay minerals; cf. You
et al. 1996), filtered using a 2-lm mesh, and analyzed
in January 2003 at the School of Earth Sciences,
Leeds, UK.
Cations and iodide were measured by ICP-MS (Agilent 7500c) on filtered water samples. Anions were
measured by ion chromatography using a Dionex 600.
Accuracy and precision of both methods was checked by
external standards. Precision in all instances was better
than 5% RSD (residual standard deviation) and accuracy better than 4%.
Eruptions
The Lokbatan mud volcano
The Lokbatan mud volcano is located in the middle of
an oil and gas field just south of Baku (Figs. 1, 2 and 3).
The mud volcano pierces the crest of an anticline, where
several mud volcanoes are aligned along strike within
11 km (e.g., Sjögren 1891; Jakubov et al. 1971; Guliyev
2002; Kadirov et al. 2002). Twenty-two eruptions have
been recorded from the Lokbatan mud volcano since the
early 1800s (Aliyev et al. 2002). These eruptions are
associated with seismic activity, fracture formation,
ground deformation, emplacement of mud breccia flows,
and ignition of hydrocarbons flowing with the mud.
The most recent Lokbatan eruption occurred on 24
October 2001, lasting for about 30 min (Aliyev et al.
2002). It was associated with ground tremors, eruption
of mud breccia, and extensive fires lasting for more than
one year after the eruption (Figs. 2, 3). A graben extends
from the vent along the crest of the anticline (Fig. 2).
The vent is flanked by two horst blocks, which were both
covered by ejected mud breccia material during the most
recent eruption. However, most of the mud breccia was
emplaced as a flow within the central part of the graben.
The estimated total volume of the flow is approximately
0.0003 km3 (Aliyev et al. 2002).
Extensive faulting is seen along the summit of
Lokbatan. Displacement of these faults occurred both
during the 2001 eruption (Fig. 3F) and previous eruptions (Jakubov et al. 1971). The subsidence pattern is
circular in the summit area, forming a ring fault with gas
escape features (burned mud). The displacement on the
main graben-forming faults is decreasing away from the
summit area, from 10–20 m to zero meters one kilometer
to the west.
The westward-trending graben collapse structure
suggests the presence of an elongated, shallow mud
breccia chamber within the crest of the anticline. During
an eruption, mud breccia from this chamber is drained
through the vent. We suggest that removal of this
Fig. 2 Simplified geological map of the upper part of the Lokbatan
mud volcano (vent, crater, and associated graben; October 2002)
261
Fig. 3A–F Lokbatan mud
volcano eruption, deposits, and
tectonic structures. The mud
volcano (A) is located on the
crest of an E-W-trending
anticline (view from the south).
Its last eruption was on 24
October 2001 (B; photo by Phil
Hardy, BBC 2001). Red,
burned mud breccia was present
at the eruption vent (C; see
person in circle for scale).
Ejected mud breccia covers the
horsts on the northern and
southern sides of the vent.
However, most of the ejected
mud breccia was emplaced as a
400-m-long flow in the graben
extending along the axis of the
regional anticline (D). Several
horst structures are present
within this graben (E), which
extends for more than 1 km
from the vent (F). See Fig. 2 for
photo locations
material caused subsidence and collapse of the roof
rocks, forming the graben structure. Subsequent infilling
of the graben by the erupted mud breccia increased the
load on the mud chamber, causing further surface subsidence. A shallow mud chamber hypothesis is also
consistent with the observation of a negative gravity
anomaly above the mud volcano, suggesting the presence of light, buoyant material within the crest of the
anticline (Kadirov et al. 2002).
The Kotyrdag mud volcano
The cone-shaped Koturdag mud volcano is located
about 50 km south of Baku (Figs. 1 and 4; Jakubov
et al. 1971). This dormant mud volcano is currently
quiet. A single circular crater is found on the summit of
the volcano. No faults were identified outside the crater.
The geometry of Koturdag is similar to a simple, cone-shaped composite magmatic volcano of
intermediate composition. The morphology of composite volcanoes is controlled by a complex interaction of
aggradation (i.e., eruption and emplacement) and
degradation (i.e., erosion and gravity flow) processes
(e.g., Davidson and De Silva 2000). Whereas composite
volcanoes have been extensively studied, no comprehensive studies of mud volcanic eruptions (detailed
seismicity surveys, ground deformation measurements,
or gas and fluid emission sampling) are available. The
understanding of the ascent and eruption processes of
composite mud volcanoes is therefore limited.
The most recent breccia flow was erupted from the
summit crater and emplaced on the northeastern flank of
the volcano. The flow is 1 km long and can be subdivided into two main parts—an upper channelized part
on the steep flanks of the volcano, and a lower lobate
part on the less steep, lower parts of the volcano. The
flow is blocky in the channel, and the presence of red,
oxidized mud breccia and scoria shows that escaping
gases have ignited and burned during the emplacement
262
Fig. 4A–D Eruptive deposits of
the 200-m-high Kotyrdag mud
volcano (A). A 1-km-long
channelized mud breccia flow
(B) extends from the main
crater down the flank of the
volcano. Large boulders and
clasts are common in the
breccia flow (C; 1.5-m-high
cliff). The eruption ended by
slow extrusion of viscous,
plastic mud breccia (D). Note
well-defined striations and the
presence of burned breccia at
the edge of the extruded mud
breccia sheet. Photo locations
are shown by arrow on A
(Fig. 4B). The lower lobe is characterized by a smoother
surface and the presence of curved pressure ridges. The
eruption terminated by slow extrusion of very viscous,
plastic mud breccia (Fig. 4D). The emplacement rate of
similar extruded mud breccia has been measured to be
2–15 m/year, lasting for several years after the main
eruption event (e.g., Guliyev and Feizullayev 1997).
Dormant period
The study of the seep activity during the dormant periods may provide important insight into the mud volcanic process, and is particularly important because no
mud volcanic eruptions have been monitored in detail.
In addition, studies of seep gases are important because
methane and other gases may contribute significantly to
the global greenhouse gas budget (e.g., Hovland et al.
1997; Milkov 2000; Dimitrov 2002), and because mud
volcanoes are important conduits for petroleum migration (e.g., Katz et al. 2000).
Vigorous seep activity was taking place in October
2002 on both the dormant Dashgil and Bakhar mud
volcanoes (Figs. 1, 5, and 6). In contrast, the dormant
Kotyrdag and Lokbatan mud volcanoes were quiet, with
the exception of a small fire in the Lokbatan vent
(Fig. 6D).
Seep structures on the Dashgil crater field were
described by Hovland et al. (1997), and include a gryphon cluster, mud cones, salses, and sinter cones (Figs. 5
and 6). Natural oil seeps are further found on the flanks
of the mud volcano. A re-mapping of the crater field in
October 2002 (Fig. 5) reveals the same seep features as
present in 1995, but some of the gryphons and mud
cones are up to 50% larger. The only major difference is
the addition of a mud cone field formed during a small
eruption in May 2001 (Aliyev et al. 2002).
Active gryphons, mud cones, and springs were also
found at the Bakhar mud volcano and a nearby satellite
vent. The circular satellite crater is about 10 m deep with
a diameter of about 50 m, and is located in an area with
natural oil seeps. The crater was formed by an explosive
eruption in 1998 on a gryphon field.
Waters from several of the gryphons, mud cones,
salses, and springs were sampled. The salses and springs
are dominated by water and gas, whereas the gryphons
and mud cones are filled with intermediate- to highviscosity fluids consisting of mud, water, gas, and oil.
The temperatures of these fluids are up to 2–3 C above
the ambient temperature (Table 1).
The gases seeping through the mud volcanoes in
Azerbaijan during the dormant periods are dominated
by methane (>90%; Sokolov et al. 1968; Valyaev et al.
1985; Guliev and Feizullayev 1996; Aliyev et al. 2002).
The isotopic composition of the seep methane overlaps
with the isotopic composition of methane from petroleum fields in the Caucasus (Valyaev et al. 1985; Guliev
and Feizullayev 1996), emphasizing the intimate relationship between petroleum formation, secondary
migration, and mud volcanism.
Composition of expelled waters
The major element composition of the expelled waters is
controlled by the depositional environment (e.g., marine/
263
Fig. 5 Simplified geological map of the Dashgil mud volcano crater
field (October 2002). Numbers show the sampling locations of the
Dashgil water samples in Table 1
non-marine, presence of evaporites), diagenetic processes
(e.g., Carpenter and Miller 1969; Hanor 1994; Worden
1996), temperature (e.g., Fournier and Truesdell 1973;
Fig. 6A–D Seep structures and
deposits on dormant mud
volcanoes. A Salse A at the
crater field of the Dashgil mud
volcano, with the gryphon field
to the west (B). C Hydrocarbons (black mud) in a
gryphon at Bakhar. D Burning
hydrocarbon gas in the vent at
Lokbatan. The fire has been
burning for more than a year
since the October 2001 eruption
(Figs. 2 and 3)
Hanor 1994), and mixing (e.g., Dia et al. 1999). Elements
like Cl, Br, I, and B may give important information both
about fluid source, depth, and fluid–rock interactions,
and are commonly used as tracers (e.g., Rittenhouse
1967; Harder 1970; Lagunova 1976; You et al. 1993;
Worden 1996; Kopf and Deyhle 2002). A full geochemical discussion of all the elements listed in Table 1 is
264
Table 1 Composition of water seeps from mud volcanoes (all values in ppm)
Sample
AZ02-2
Locality
Bakhar
Type
Springa
Temp. (C) 20.3
N
E
Li
B
Na
Mg
Al
K
Ca
Cr
Fe
Mn
Ni
Cu
Zn
As
Rb
Sr
Cd
Ba
Pb
U
F
Cl
Br
NO3
SO4
I
Cl/Br
Na/Br
CI/B
A202-3
Bakhar
Spring
20.3
AZ02-4
Bakhar
Spring
21.5
AZ02-7
AZ02-8
Bakhar s. v.b Dashgil
Spring
Salse A
22.5
21.6
4000¢03.93¢¢ 4000¢03.97¢¢ 4000¢03.86¢¢ 3959¢53.53¢¢
4928¢13.60¢¢ 4926¢13.91¢¢ 4928¢14.67¢¢ 4927¢18.71¢¢
0.2
0.2
0.15
0.25
49
122
201
254
8,056
12,170
13,230
22,340
116
121
135
153
85
87
86
88
40
100
119
154
170
175
155
178
101
102
102
105
279
284
320
296
41
42
42
44
91
92
93
93
85
91
90
93
19
29
26
31
17
17
17
18
0.03
0.04
0.03
0.04
0.5
0.5
0.6
0.8
0.03
0.07
0.05
0.07
0.2
0.2
0.2
0.4
0.003
0.02
0.014
0.015
0.12
0.32
0.2
0.22
<1
<1
<1
<1
13,608
20,534
21,450
33,464
69
108
110
193
6
19
13
<2
84
247
235
161
<5
<5
<5
<5
197
190
195
173
117
113
120
116
278
168
107
132
AZ02-12
Dashgil
Salse B
18.5
AZ02-14
Dashgil
Spring
AZ02-16
Dashgil
Gryphon
19.9
Seawaterc Caspian
Sea
3959¢43.81¢¢ 3959¢39.56¢¢ 3959¢53.80¢¢ 3959¢46.50¢¢
4924¢23.03¢¢ 4924¢30.29¢¢ 4924¢20.19¢¢ 4924¢09.68¢¢
0.2
0.25
0.2
0.26
0.18
<2
16
<2
125
4.5
5,842
14,560
7,876
14,010
10,763
160
504
306
270
1,292
86
66
66
89
0.01
90
323
175
341
399
189
196
198
184
411
102
102
102
102
5E)05
324
497
295
299
0.01
42
42
42
42
0.002
91
93
93
95
0.002
84
91
92
100
0.003
1.6
92
61
62
0.01
17
18
19
17
0.003
0.04
0.03
0.04
0.04
0.12
0.9
6.3
2.9
1.4
8.0
0.02
0.03
0.08
0.07
0.0001
0.3
2.2
0.2
0.1
0.03
0.004
0.02
0.03
0.015
3E)05
0.09
0.13
0.37
0.17
0.003
<1
<1
<1
<1
1.3
11,457
27,168
13,895
23,938
19,354
58
134
59
150
67
<2
<2
<2
252
0.5
2
57
832
2,985
2,710
<5
<5
<5
<5
0.06
198
203
236
160
291
101
109
133
93
162
>5,729
1,698
>6,948
192
278
a
3,250
817
90
387
5,650
9
3,167
628
361
c
The springs are water-dominated with varying degrees of mud
Bakhar satellite vent
Seawater composition is compiled from Fontes and Matray (1993)
for major elements, and Mason (1966) for trace elements. The
seawater data are recalculated from mg/l values to ppm using a
density of 1,022 kg/l (Fontes and Matray 1993). The (central) Caspian Sea data are from Balakishiyeva and Rashidova
(1980)
beyond the scope of this contribution, and would need a
bigger dataset. Although our dataset is limited, we may
draw important conclusions about the main fluid reservoirs that hosted the expelled waters.
The expelled waters have a composition with Na and
Cl as dominant ions (Table 1). The Cl content range is
from 11,000 to 33,000 ppm, from the Dashgil Salse A
and the Bakhar satellite vent, respectively. There is a
considerable range in concentration of major solutes (Cl,
Na) within both the Dashgil and Bakhar localities
(Table 1), consistent with what is documented from
other mud volcanoes in Azerbaijan (Jukabov et al. 1971;
Aliyev et al. 2002) and elsewhere (e.g., Lagunova 1976;
Dia et al. 1999). Na and Cl correlate linearly (Fig. 7),
and the Na–K–Cl relations group according to locality.
Furthermore, the most K-rich waters (175–341 ppm)
have the highest Zn concentrations (61–92 ppm). The
sulfate content of all the waters is low, the one exception
being water from a water–mud mixture from a gryphon
at Dashgil (SO4 value of 3,000 ppm). This is in accordance with published data on both expelled waters and
reservoir waters (Aliyev et al. 2002). Charge balance
considerations do not suggest that bicarbonate is
abundant in the waters, also in agreement with published data from the region (Jakubov et al. 1971).
The analyzed waters are enriched in B and metals
(Al, Cr, Fe, Mn, Ni, Cu, Zn) compared to seawater
(Table 1), oilfield brines (Collins 1975), and expelled
waters from other mud volcanoes worldwide (e.g., Dia
et al. 1999; Kopf and Deyhle 2002). The concentrations of metals like Cu, Ni, and Cr, which are soluble
in the reduced state, are very high (84–105 ppm), and
independent of the Cl concentration in the waters
(Table 1). Metals like Cu, Cr, and Ni are usually
present in parts per billion in oilfield brines (Collins
1975). Intriguingly, elements like Na, Cl, Mg, K, and
B vary considerably in the analyzed waters, whereas
most of the metals show no concentration variations
(Table 1). The standard deviation for the average of all
analyses in Table 1 is less than 5% for Cr, Mn, Ni,
and Cu.
Furthermore, the B content is high (50–254 ppm;
Fig. 8), with the exception of two waters from Dashgil
(<2 ppm). A boron concentration of 250 ppm repre-
b
265
concentrations (Aliyev et al. 2002), as are mud volcanoes
in the Crimea area of the Black Sea (Kerch-Taman),
where values up to 915 mg/l are documented from
expelled waters (Lagunova 1976).
Fluid sources and mixing trends
Fig. 7 Variation of selected elements compared to seawater
composition (line seawater evaporation trend) for the waters from
gryphons, salses, and springs. Seawater (SW) evaporation data
(straight lines from SW) are taken from Fontes and Matray (1993),
and Caspian Sea (CS) compositional data are from Balakishiyeva
and Rashidova (1980). Open symbols represent samples from
Dashgil, and closed symbols from Bakhar
sents a 55-fold enrichment in comparison to seawater.
Expelled waters from mud volcanoes and oilfield brines
from Azerbaijan are indeed associated with high B
Fig. 8 The Cl–B–Br systematics of the analyzed brines from
Dashgil and Bakhar, showing that their composition can be
explained by a simple two-component mixing model. Type 1 brines
have Cl and B concentrations typical of oilfield brines and high Br
concentrations (low Cl/Br ratios). Type 2 brines are defined by
Salse A at Dashgil. These fluids have a salinity that is lower than
seawater and low B concentrations. The Guneshli production water
Cl concentration is from Statoil (M. Hovland, personal communication), and taken from about 1,500-m depth in the Productive
Series. The compositional range of oilfield brines is from Collins
(1975). Seawater (SW) evaporation data (straight lines from SW)
are taken from Fontes and Matry (1993). Open symbols represent
samples from Dashgil, and closed symbols from Bakhar
Figure 8 shows the Br and Cl relations of the analyzed
waters, revealing a good linear correlation (r2=0.95).
The slope of the trend line for the Cl–Br correlation is
less steep than that of seawater evaporation, making it
unlikely that the waters acquired their salinity by surface
evaporation of parent water in the vents. Although
Cl/Br versus Na/Br plot close to the seawater evaporation trend, the salinities are far too low to correspond to
possible surface evaporation (146,000 ppm Cl at
the onset of halite precipitation; Fontes and Matray
1993).
The Cl–Br–B relationships in Figs. 8 and 9 suggest
two different mixing models: (1) mixing between two
saline waters (Fig. 8), and (2) mixing between deep-seated saline waters and shallow meteoric waters (Figs. 8
and 9). The two end-member waters in the Cl–Br system
(Fig. 8) were taken from the Bakhar satellite vent (high
Cl, high Br: type 1) and from Dashgil Salse A (low Cl,
low Br: type 2). Type 2 water has a salinity resembling
production waters from the Guneshli oilfield reservoir at
about 1,500-m depth below the seafloor (M. Hovland,
personal communication). A mixing model between the
two Cl–Br end-member fluids is also supported by the
Cl–B relations (Fig. 8). The Dashgil Salse A water is
low in Cl and low in B, whereas the Bakhar satellite vent
is high in both Cl and B.
The high B contents of mud volcano waters in
Azerbaijan suggest that the waters have a deep origin
from strata affected by the smectite–illite transformation
(e.g., You et al. 1996; Kopf and Deyhle 2002), where the
B could originate from marine clays or organic material
(e.g., Ishikawa and Nakamura 1993; Williams et al.
266
Fig. 9 The Cl–Br systematics of the waters can be explained by
dilution of a saline fluid by a low-salinity component (meteoric
water). The halite compositional range (‘‘salt’’ rectangle) is from
McCaffrey et al. (1987)
2001). The high Br concentration and lower Cl/Br ratio
in the type 1 component do not support a Br source
related to organic material, as the I concentrations are
too low (cf. Worden 1996). Interestingly, the B and Li
concentrations in expelled waters from a Kerch-Taman
mud volcano was increased following an eruption
(Lagunova 1974), suggesting that these elements are
enriched in the source region. However, our data do not
show any correlation between B and Li as described
from the Kerch-Taman area (Lagunova 1976). In the
case of B release during the smectite–illite transformation, an accompanying salinity reduction due to dehydration should occur as well (e.g., Moore and Vrolijk
1992; Fitts and Brown 1999). However, the B and Cl
concentrations are positively correlated (Fig. 7), suggesting a more complex relationship between Cl–B
concentration and smectite dehydration.
The low Cl/Br ratios of the waters (160–236 by mass)
suggest that their salinity was not derived from dissolution of evaporates in the source strata or during ascent, which would have resulted in higher Cl/Br ratios.
The narrow Cl/Br ratio range of the waters suggests that
all waters represent dilution of one, high-salinity water
reservoir by low-salinity waters. The low B concentrations in the type 2 water component suggests that it has
undergone different processes than type 1 waters, possibly originating from shallow reservoir levels with fluids
not significantly affected by clay mineral diagenesis (cf.
the Guneshli water composition), or from meteoric water. The latter is more likely, considering the narrow Cl/
Br range of the waters.
The metal concentrations in the analyzed waters do
not vary with the chlorine concentration, and may be
explained by enrichment after mixing. Both metal
Fig. 10 Conceptual drawing summarizing the main elements of
Azeri mud volcanism and the results from the geochemistry
presented in this paper. The deep type 1 waters may have
originated from the clay-rich Maikop Fm., and deeper mud-rich
layers. The type 1 reservoir is located below the main depth of
initiation of smectite dehydration (see Ransom and Helgeson
1995), and has probably acquired the high B concentration from
desorption from clays (cf. Kopf and Deyhle 2002). The presence of
a mud reservoir at deeper levels than the Maikop Fm. is evident
from Cretaceous–Eocene clasts in mud breccias (Inan et al. 1997).
Furthermore, the main oil source rock is believed to be located
deeper that the Eocene (stippled line; Inan et al. 1997). Saline water,
mud, and oil migrate through the mud volcano conduit, and mud is
in many cases stored in intermediate mud chambers. Low-salinity
meteoric waters mix with the more saline deeper waters, and there
is considerable variation in the degree of mixing between the two.
High-water runoff features like salses can be explained by being fed
by a shallow meteoric reservoir, whereas waters from gryphons
may represent deeper fluids slowly percolating to the surface. The
figure is modified from Guliyev and Feizullayev (1997), and the
stratigraphic information is from Inan et al. (1997)
desorption from clay minerals (e.g., Helios Rybicka
et al. 1995) and redox-controlled precipitation–dissolution are possible mechanisms that may occur in the
upper part of mud volcanoes. High Fe/Mn ratios
(6.7–11.8) do not suggest loss of iron due to oxidation,
and can be considered as indicative of a reduced fluid
(Bottrell and Yardley 1991); hence, the waters may carry
transition metals soluble in the reduced state, as shown
by the water analyses.
Type 2 waters have the lowest salinity and possibly
the shallowest origin, and represent the most waterdominated parts of the mud volcanoes (i.e., the salses).
The salses apparently have higher runoff rates than the
springs and the gryphons. The waters plotting along the
mixing line away from the type 2 component were all
267
sampled from mud-dominated systems (gryphons and
springs). These observations can be explained if the flux
from the shallow reservoirs (meteoric water) is high in
the salses, whereas the gryphons and springs represent a
low-flux system originating from the deep-seated mud
source.
Conclusions
A shallow mud chamber is interpreted to be present
below the summit of the Lokbatan mud volcano
(Fig. 10). Inflation and deflation of this elongated mud
chamber prior to, and during eruptions causes the formation of a graben by subsidence and fracturing of the
roof. A more deep-seated mud chamber is suggested for
the composite Koturdag mud volcano.
New data on water geochemistry, integrated with
published gas data (Guliev and Feizullayev 1996; Katz
et al. 2000), support the hypothesis of a complex
plumbing system beneath the mud volcanoes during the
dormant periods. We propose that the mud volcano seep
fluids represent leakage from a deep source mixed with a
component of meteoric waters. This is consistent with
the recognition of the deep-seated Maikop Fm. as the
main source of the extruded mud, and the existence of
intermediate mud chambers at 2–4 km depth (Cooper
2001).
Dormant mud volcanoes show a large variation in
activity, from mainly quiet (e.g., Koturdag, Lokbatan)
to very active (e.g., Dashgil, Bakhar). We suggest that
the water-dominated salses represent expulsions of
shallow waters, whereas deep-seated fluids percolate
slowly to the surface and are expelled as mud–water
mixtures in gryphons and springs.
Acknowledgments This work was partly financed by the Norwegian
Research Council grant 120897 to B. Jamtveit/H. Svensen. We
would like to thank Statoil for logistic assistance during fieldwork,
and Achim Kopf for a constructive review.
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