Geology and Hydrothermal Alteration of the Ayd›n- Salavatl› Geothermal Field, Western Anatolia

24 Pages·2003·0.67 MB·English

Turkish Journal of Earth Sciences(Turkish J. Earth Sci.), Vol. 12,2003, pp. 175-198.Copyright 'T(cid:134)B(cid:220)TAK
Geology and Hydrothermal Alteration of the Ayd(cid:221)n-
Salavatl(cid:221) Geothermal Field, Western Anatolia, Turkey
(cid:220)SMA(cid:220)L HAKKI KARAMANDERES(cid:220)1 & CAH(cid:220)T HELVACI2
1 Maden Tetkik ve Arama Genel M(cid:159)d(cid:159)rl(cid:159)(cid:219)(cid:159) (MTA), Ege B(cid:154)lge M(cid:159)d(cid:159)rl(cid:159)(cid:219)(cid:159),
TR-35042 Bornova, (cid:220)zmir - Turkey
2 Dokuz Eyl(cid:159)l (cid:134)niversitesi, M(cid:159)hendislik Fak(cid:159)ltesi, Jeoloji M(cid:159)hendisli(cid:219)i B(cid:154)l(cid:159)m(cid:159),
TR-35100 Bornova, (cid:220)zmir - Turkey (e-mail: [email protected])
Abstract:The Ayd(cid:221)n-Salavatl(cid:221) geothermal field is located in the middle part of the B(cid:159)y(cid:159)k Menderes Graben, and is
characterized by normal-fault structures. The stratigraphic sequence of the Ayd(cid:221)n-Salavatl(cid:221) geothermal field
consists of metamorphic rocks of the Menderes Massif and sedimentary rocks deposited during the rifting period
of the Menderes Massif in the Miocene. Geological data suggest that there is a connection between tectonic
development and periods of hydrothermal alteration.
Hydrothermal alteration in the Ayd(cid:221)n-Salavatl(cid:221) geothermal field occurred in five distinct periods, and all are
related to different stages of faulting systems, from the Middle Miocene up to the present. The first period of
hydrothermal alteration was characterized by mercury and antimony mineralization related to acidic intrusions, and
by the occurrence of rutile mineralization within quartz veins. Gabbros and associated dykes developed in the
second period. In this period, gneisses were subjected to hydrothermal alteration. The third period was
characterized by granite intrusions. Specularite, talc, calcite, quartz, and aragonite mineralization and travertine
formed along the margins of these intrusions. The fourth period was marked by albite and chlorite mineralization
that developed during N—S faulting. Hydrothermal alteration zones which developed in the last period are
associated with active faults along which hot fluid is circulating. These faults have more than 100 m of downthrow,
and formed during the final period of graben formation. Hydrothermal alteration products caused by the
circulation of geothermal fluids within these faults in Upper Miocene sediments include kaolinite, illite,
montmorillonite, dickite, vermiculite, calcite, pyrite, dolomite and hydrobiotite. These minerals are still
precipitating/forming in active circulation zones. Thermal waters of the Ayd(cid:221)n-Salavatl(cid:221) geothermal field are a Na-
HCO type with high CO and B contents that are associated with metamorphic rocks of the Menderes Massif and
3 2
hydrothermal alteration which developed via water-rock interactions. Geophysical studies were used to outline
tectonic structures and frames of the Salavatl(cid:221) geothermal field.
Key Words: geothermal field, hydrothermal alteration, B(cid:159)y(cid:159)k Menderes Graben, Salavatl(cid:221), western Anatolia,
Turkey
Ayd(cid:221)n-Salavatl(cid:221) Jeotermal Sahas(cid:221)n(cid:221)n Jeolojisi ve Hidrotermal
Alterasyonu, Bat(cid:221) Anadolu, T(cid:159)rkiye
(cid:133)zet:Ayd(cid:221)n-Salavatl(cid:221) jeotermal sahas(cid:221) B(cid:159)y(cid:159)k Menderes vadisi orta b(cid:154)l(cid:159)m(cid:159)nde yer al(cid:221)r ve normal fayl(cid:221) bir yap(cid:221) ile
temsil edilir. Ayd(cid:221)n-Salavatl(cid:221) jeotermal sahas(cid:221) stratigrafik kesiti Menderes Masifi metamorfik kayalar(cid:221) ve bunun
(cid:159)zerine Miyosen(cid:213)den g(cid:159)n(cid:159)m(cid:159)ze kadar devam eden d(cid:154)nemde (cid:141)(cid:154)kelmi(cid:223) sedimanter kaya topluluklar(cid:221)ndan
olu(cid:223)maktad(cid:221)r. Jeolojik veriler Menderes Masifi(cid:213)ndeki tektonik geli(cid:223)im ve evreleri ile hidrotermal alterasyonlar(cid:221)n
ili(cid:223)kili oldu(cid:219)unu g(cid:154)stermi(cid:223)tir.
Ayd(cid:221)n-Salavatl(cid:221) jeotermal sahas(cid:221)ndaki hidrotermal alterasyon be(cid:223) farkl(cid:221) evreye ayr(cid:221)lm(cid:221)(cid:223)t(cid:221)r. Bu evreler genle(cid:223)me
tektoni(cid:219)i faylar(cid:221) ile belirlenmi(cid:223) olup Orta Miyosen(cid:213)den itibaren g(cid:159)n(cid:159)m(cid:159)ze kadar devam etmi(cid:223)tir. (cid:220)lk evre
hidrotermal alterasyon civa ve antimuan mineralle(cid:223)mesi ve bunlarla ili(cid:223)kili asidik intr(cid:159)zyonlar(cid:221)n yerle(cid:223)mesidir. Bu
evre fosil jeotermal sistemlerde g(cid:154)zlenen mineral parajenezleri, rutil mineralizasyonlar(cid:221) ve kuvars (cid:141)atlak dolgular(cid:221)
ile karakterize edilmektedir. Gabro ve onlara e(cid:223)lik eden dayklar ikinci evreyi olu(cid:223)turur. Bu evrede gnayslar(cid:221)n
hidrotermal alterasyona u(cid:219)rad(cid:221)(cid:219)(cid:221) belirlenmi(cid:223)tir. (cid:134)(cid:141)(cid:159)nc(cid:159) evrede ise granit intr(cid:159)zyonlar(cid:221) yerle(cid:223)mi(cid:223)tir. Bu
intr(cid:159)zyonlar(cid:221)n yan kayalar(cid:221)nda spek(cid:159)larit, talk, kalsit, kuvars, ve aragonit mineralleri ile (cid:159)st bo(cid:223)al(cid:221)m b(cid:154)lgelerinde
traverten olu(cid:223)umlar(cid:221) g(cid:154)r(cid:159)l(cid:159)r. D(cid:154)rd(cid:159)nc(cid:159) evre albit-klorit mineralizasyonu ile kuzey—g(cid:159)ney uzan(cid:221)ml(cid:221) fay hatlar(cid:221)nda
belirlenmi(cid:223)tir. Son evre ise y(cid:159)ksek s(cid:221)cakl(cid:221)kl(cid:221) jeotermal ak(cid:221)(cid:223)kan(cid:221)n dola(cid:223)t(cid:221)(cid:219)(cid:221) fay zonlar(cid:221)nda belirlenmi(cid:223)tir. Bu fay
zonlar(cid:221)ndaki hareket 100 metreden fazlad(cid:221)r ve graben olu(cid:223)umunu belirleyen son hareketlerdir. (cid:134)st Miyosen
175
AYDIN-SALAVATLI GEOTHERMAL FIELD, WESTERN ANATOLIA
tortullar(cid:221) i(cid:141)inde dola(cid:223)an jeotermal ak(cid:221)(cid:223)kanlar bu fay zonlar(cid:221)nda hidrotermal alterasyona sebep olmu(cid:223)lard(cid:221)r. Aktif
hidrotermal alterasyon mineralojisi kaolinit, illit, montmorillonit, dikit, vermik(cid:159)lit, kalsit, pirit, dolomit ve
hidrobiyotit minerallerinden olu(cid:223)maktad(cid:221)r. Bu minerallerin varl(cid:221)(cid:219)(cid:221) aktif jeotermal ak(cid:221)(cid:223)kan dola(cid:223)(cid:221)m(cid:221)n(cid:221)n halen
s(cid:159)rd(cid:159)(cid:219)(cid:159)n(cid:159) g(cid:154)stermektedir. Ayd(cid:221)n-Salavatl(cid:221) jeotermal sahas(cid:221)n(cid:221)n sular(cid:221), Menderes Masifi kayalar(cid:221)n(cid:221)n su-kaya
etkile(cid:223)imi ile geli(cid:223)en hidrotermal alterasyona ba(cid:219)l(cid:221) olarak y(cid:159)ksek CO ve B i(cid:141)erikli Na-HCO tipindedir. Jeofizik
2 3
(cid:141)al(cid:221)(cid:223)malar(cid:221) Salavatl(cid:221) jeotermal sahas(cid:221)n(cid:221)n tektonik yap(cid:221)s(cid:221)n(cid:221) ve konumunu belirlemek i(cid:141)in kullan(cid:221)lm(cid:221)(cid:223)t(cid:221)r.
Anahtar S(cid:154)zc(cid:159)kler: jeotermal saha, hidrotermal alterasyon, B(cid:159)y(cid:159)k Menderes Grabeni, Salavatl(cid:221), bat(cid:221) Anadolu,
T(cid:159)rkiye
Introduction is located along fault systems near the towns of Salavatl(cid:221)
and Sultanhisar.
Extensive tectonic activity, especially the formation of
east—west grabens, has dictated the shape of western A couple of deep wells were drilled by General
Anatolia (Figure 1). Of these, B(cid:159)y(cid:159)k Menderes and Gediz Directorate of Mineral Research and Exploration (MTA)
grabens host the main and the most important (AS-1, 1510 m below ground level; and AS-2, 962 m,
geothermal fields of Turkey. The distribution of Figure 2) within a low resistivity zone (5—10 ohmm)
geothermal fields in Turkey closely follows the tectonic outlined by resistivity-depth sounding studies. Cuttings
patterns. All of the hot springs with temperatures above from the AS-1 and AS-2 wells near Salavatl(cid:221) were studied
50—100…C in eastern and western Anatolia are clearly by petrographic microscopy and XRD methods, and the
related to young volcanic activity and block faulting. Post- nature and distribution of their mineral parageneses were
collisional volcanic activity, lasting from the Late Miocene determined. The data obtained from the drill cores of
to present, has been responsible for heating the these wells are the subject of this paper, and are used to
geothermal fields ((cid:222)im(cid:223)ek 1997; Y(cid:221)lmaz 1997; Demirel & explain a model for the geothermal system of the Ayd(cid:221)n-
(cid:222)ent(cid:159)rk 1996). The high thermal activities are reflected Salavatl(cid:221) field.
in widespread acidic volcanic activity with much
hydrothermal alteration, fumaroles, and more than 600
Materials and Methods
hot springs with temperatures up to 100 …C ((cid:130)a(cid:219)lar
1961). Relatively detailed cutting analyses along with various
other borehole logs were used to assess the geothermal
The Ayd(cid:221)n-Salavatl(cid:221) geothermal field is located in the
system into which wells AS-1 and AS-2 were drilled.
middle part of the B(cid:159)y(cid:159)k Menderes Graben, and is
During drilling, rock cuttings were taken every 2 m and
characterized by E—W-trending normal faults (Figure 1).
were properly labelled. Circulation losses and rates of
The stratigraphic sequence of the field is composed of
penetration were recorded for each drill pipe sunk.
metamorphic rocks of the Menderes Massif and overlying
Temperature logs were carried out during drilling to
the Miocene sedimentary rocks deposited during the
locate aquifers and assess the condition of the wells. The
Miocene exhumation of the massif. Field data suggest
temperature-logging equipment comprised Amerada
that there is a connection between tectonic development
logging tools. These logs provide important information
and periods of hydrothermal alteration. Several deep
on temperature conditions, flow paths and feed-zones in
wells were drilled (AS-1, 1510 m and AS-2, 962 m) and
geothermal systems. Temperature logs have also been
revealed low resistivity zones (Karamanderesi 1997).
prepared after drilling and production.
Preliminary studies were conducted on a regional
The well-testing method was controlled by lip-
scale by Karamanderesi (1972). Geochemical analysis of
pressure measurements that give total mass-flow rate
water from hot springs near Salavatl(cid:221) village indicated
and the heat content (enthalpy) of a two-phase
that the area has hot-water-dominated geothermal
geothermal fluid from a discharge pipe.
potential, and geophysical studies outlined the structural
situation of the geothermal field. Geophysical studies Samples in the well or drill boxes are wettened by
using gravity (G(cid:159)lay 1988) and electrical resistivity pouring water onto them. Wetting the cuttings is
methods ((cid:222)ahin 1985) indicated that the geothermal field necessary to enhance the visibility of the samples or
176
(cid:220). H. KARAMANDERES(cid:220) & C. HELVACI
N
(cid:221)ZM(cid:221)R
studyarea
0 500km
Edremitgraben
Bak(cid:253)r(cid:231)aygraben Simav
graben
G(cid:246)rdesgraben
Soma
graben
Turgutlu
(cid:221)ZM(cid:221)R
Gediz
graben
M
E
N
K(cid:252)(cid:231)(cid:252)kMenderesgrabenD
E
R
E K(cid:253)z(cid:253)ldere
Salavatl(cid:253) S
M
A
AYDIN S
SI DEN(cid:221)ZL(cid:221)
A F
E B(cid:252)y(cid:252)kMenderes 0 50km
S
graben Geothermalfield
N
A
fault(unspecifiedand/or
E
vergenceunknown)
G
E G(cid:246)kovagraben normalfault
A
fault(inferred)
neotectonicfault-bounded
basin
Figure 1. Main tectonic features of western Anatolia and location map of the Ayd(cid:221)n-Salavatl(cid:221) geothermal field.
certain features such as finely disseminated sulphides were made in order to expand or confirm preliminary
(e.g., pyrite). The wet samples were then placed onto the findings from the cuttings. However, this method intends
mounting stage of the microscope for investigation. to complement rather than replace careful binocular
Cutting examination was done using binocular microscope microscopic studies and adds understanding with regard
with a 5x10 magnification of the field of study. Initial to rock-mineral deposition and alteration. Selected thin-
information obtained includes stratigraphic/ section samples were analysed using the petrographic
sedimentological features, alteration mineralogy and microscope.
evidence of permeabilities. In addition to binocular
X-ray diffractometric analyses were done on the ~4
microscopic study, thin sections for petrographic study
(cid:181)m fractions of particular samples from the cuttings in
177
AYDIN-SALAVATLI GEOTHERMAL FIELD, WESTERN ANATOLIA
10 Q Q BeyDaðý N 09
Ovacýk Plateau
Bozdað Overthrust
0 1 2km
e Q
r
e
d
klý
a
ab DEM(cid:221)RHAN
K
MALGAÇEM(cid:221)R
A Bozköy
overthrustQ GÜVEND(cid:221)K
KaraT.
AZAPDERES(cid:221)
ESK(cid:221)H(cid:221)SAR
SALAVATLI
AS-1 SULTANH(cid:221)SAR ATÇA
AS-2 Hamam
(mevkii)
YAVUZKÖY
B.
A Menderes c
KÖÞK River ectriline
80 2040Geoelprofil
6
86 1 YEN(cid:221)PAZAR
A. alluvium-travertine- augengneiss contact
U terracematerials
Q Bozk(cid:246)yoverthrust fault
garnet-amphibole
clay-marl-
O.
LI sandstone C schist thrustor
OC.P csalanyds-tmonaerl- OZOI DBoezmdaiðrhovaenrthrust A A rcervoessrs-seefcatuioltn
MI E metagranite
L
NE. Q quartzvein PA chloriteschist AS-1 deepwell
E
C thermalspring
O
MI
E- gabbro marble fumarole
R
P
Figure 2. Geological map of the Ayd(cid:221)n-Salvatl(cid:221) geothermal field.
178
(cid:220). H. KARAMANDERES(cid:220) & C. HELVACI
order to confirm and identify the types of clay minerals western Turkey, and has been under the influence of N—S
present in the cuttings. Approximately two teaspoons of crustal extensional tectonics since the Early Miocene (e.g.,
drill cuttings were placed into a test tube, and dust was Ko(cid:141)yi(cid:219)it et al. 1999; Bozkurt 2001a, b; Bozkurt &
washed out with distilled water. The tubes were filled 2/3 Oberh(cid:138)nsli 2001a, b; Seyito(cid:219)lu et al. 2002; S(cid:154)zbilir
full with distilled water and plugged with rubber 2002). It is dissected into northern, central and southern
stoppers. The tubes were placed in a mechanical shaker submassifs along the E—W-trending seismically active
for 4—8 hours, depending on the alteration grade of the Gediz and B(cid:159)y(cid:159)k Menderes grabens, respectively; the
samples. The contents were allowed to settle for 1—2 grabens are the result of N—S extension which
hours until only particles finer than approximately 4 commenced by the Early Pliocene (~5 Ma) (e.g., Ko(cid:141)yi(cid:219)it
microns were left in suspension. A few millilitres of liquid et al.1999; Bozkurt 2000, 2001a, 2002; Sar(cid:221)ca 2000;
was pipetted from each tube and about 10 drops placed Y(cid:221)lmaz et al.2000; Gen(cid:141) et al.2001; G(cid:159)rer et al.2001;
on a labelled glass plate. An effort was made to avoid S(cid:154)zbilir 2001, 2002; Y(cid:221)lmaz & Karac(cid:221)k 2001). It is now
thick samples. A duplicate was made of each sample and agreed that each submassif represents a core complex
left to dry at room temperature overnight. One set of formation in the footwall of presently low-angle normal
samples was placed in a desiccator containing glycol faults, but their exhumations have occurred at different
times (e.g., Bozkurt & Park 1994, 1997a, b; Verge
(C O O ) solution and the other into a desiccator
2 6 2
1995; Hetzel et al.1995a, b, 1998; Okay et al.1996b;
containing CaCl 2H O. The samples were stored at room
2 2
Ko(cid:141)yi(cid:219)it et al. 1999; Bozkurt & Sat(cid:221)r 2000; Bozkurt
temperature for at least 24 hours. Thick samples needed
2001b; Gessner et al.2001a, b; G(cid:154)kten et al.2001; I(cid:223)(cid:221)k
a longer time in the desiccator — at least 48 hours. Both
& Tekeli 2001; S(cid:154)zbilir 2001).
sets of samples were run from 2 to 15¡ on the XRD. One
set of the samples (normally the glycolated one) was The Menderes Massif is traditionally described as a
placed on an asbestos plate and heated in a preheated thick lithologic succession made up of: (1) a (cid:212)core(cid:213)
oven at 550—600 ¡C. The oven temperature did not consisting mostly of granitic augen gneiss with
exceed 600 ¡C. The exact location on the asbestos of boundinaged layers of metagabbros — they show
individual samples was established before heating because granulite and eclogite relics and, (2) a (cid:212)cover(cid:213) series of
labelling disappears during the heating process. The low-grade metasediments comprising metapelites with
samples were cooled sufficiently before further subordinate psammite, amphibolite and marble
treatment. Then the samples were run from 2 to 15¡ on intercalations (Palaeozoic (cid:212)schist cover(cid:213)) and a marble-
the XRD. dominated sequence (Mesozoic-Cenozoic (cid:212)marble cover(cid:213))
containing emery, metabauxite, and rudist fossils. The
age of the granitic protolith for the augen gneisses is
Geologic Setting of the Menderes Massif assigned as Late Precambrian and Early Cambrian (c.
The Menderes Massif is a crustal-scale (covering more 521—572 Ma, averaging 550 Ma: U-Pb and Pb-Pb single
than 40,000 km2), elongate (with its long axis trending zircon evaporation methods) (e.g., Hetzel & Reischmann
NE—SW) metamorphic core complex in western Turkey 1996; Loos & Reischmann 1999; Gessner et al.2001a).
(Figure 1). It is structurally overlain by the Lycian Nappes Fossil evidence indicates a Permian to Middle Palaeocene
(e.g., Graciansky 1972; Collins & Robertson 1997, age for the cover rocks (e.g., Phillipson 1918; (cid:133)nay
1999; Oberh(cid:138)nsli et al.2001) in the south and rocks of 1949; (cid:130)a(cid:219)layan et al.1980; Konak et al.1987). The
readers are referred to Okay (2001, 2002), (cid:133)zer et al.
the (cid:220)zmir-Ankara Neotethyan suture (e.g., (cid:222)eng(cid:154)r &
(2001) and G(cid:159)ng(cid:154)r & Erdo(cid:219)an (2002) for further
Y(cid:221)lmaz 1981; Okay & Siyako 1993; Okay et al.1996a) in
reading.
the north. There are claims that the massif can be
correlated with the Cycladic Massif in the Aegean (D(cid:159)rr et The contact relationship between the so-called (cid:212)core(cid:213)
al.1978; Oberh(cid:138)nsli et al.1998); but others argue that and (cid:212)cover(cid:213) rocks is still debated. The views fall into three
these massifs do not represent mutually lateral major categories: (1) the contact is a major unconformity
continuations (e.g., Ring et al.1999; Okay 2001). called the supra Pan-African unconformity ((cid:222)eng(cid:154)r et al.
1984); (2) it is a south-facing extensional shear zone with
The massif forms one of the most important
preserved local igneous contacts along which the core
geological entities of the Turkish Alpine orogenic belt in
rocks are intrusive into cover rocks (Bozkurt et al.1993,
179
AYDIN-SALAVATLI GEOTHERMAL FIELD, WESTERN ANATOLIA
1995; Bozkurt & Park 1994, 1997a, b, 1999; Hetzel & Western Anatolia is characterized by a number of
Reischmann 1996; Bozkurt & Sat(cid:221)r 2000; Lips et al. approximately east—west-trending, subparallel, normal
2001). These authors suggest that the so-called core fault zones bordering a set of grabens and intervening
rocks have been exhumed in the footwall of this shear horst blocks. Seismic activity is intense and has been
zone during a top-to-the-SSW deformation; (3) while recorded by a network of instruments roughly encircling
others confirm the tectonic nature of this contact but the active faults. Motions on the faults confirm that
claim that it is south-facing thrust fault with a top-to-the- extension is in a north—south direction. Western Anatolia
south deformation (Ring et al. 1999; Gessner et al. and the Aegean regions have long been known to
2001a). represent a broad zone of extension (Phillipson 1918),
The literature suggests that the core rocks have been stretching from Bulgaria in the north to the Aegean arc in
affected by granulite facies metamorphism followed by an the south (McKenzie 1972).
eclogite facies event, then by an amphibolite facies There are about ten ~E—W-oriented grabens in
metamorphic overprint (Candan 1995, 1996; Candan et western Anatolia. The best-developed grabens are B(cid:159)y(cid:159)k
al.1997, 2001; Oberh(cid:138)nsli et al.1997; Candan & Dora Menderes, Gediz, Edremit, G(cid:154)kova and Bergama. They
1998). The lack of eclogite and granulite relicts in the are c. 100—150-km long and 5—15-km wide. In each
augen gneisses suggests that these rocks were affected graben, one margin is characterized by steeper
only by the latest amphibolite-facies metamorphism (e.g., topography, associated with surface breaks. On the
Candan et al.2001 and references therein). footwall margins of the grabens, planar faults are readily
The most agreed-upon concept concerning the observed (Figure 1).
Menderes Massif is that the massif has acquired its massif N—S extensional tectonics in the Aegean region have
character during an Alpine regional HT/MP Barrovian- been explained by (cid:210)tectonic escape(cid:211) ((cid:222)eng(cid:154)r 1979, 1980,
type tectono-metamorphic event termed (cid:210)main Menderes 1982, 1987; Dewey et al.1979; (cid:222)eng(cid:154)r et al.1985) or
metamorphism (MMM)(cid:211) during Eocene (Rb-Sr mica ages (cid:210)back-arc spreading(cid:211) (Le Pichon & Angelier 1979, 1981;
of 35–5 Ma, Sat(cid:221)r & Friedrichsen 1986 and 62—43 Ma, McKenzie 1978; Jackson & McKenzie 1988; Melenkamp
Bozkurt & Sat(cid:221)r 2000; 40Ar-39Ar mica age of 43—37 Ma, et al.1988). These models and their variations ((cid:222)eng(cid:154)r
Hetzel & Reischmann 1996; and 40Ar-39Ar laser probe 1987; Dewey 1988) indicate the timing of initiation of
mica age of 36–2, Lips et al.2001). It is suggested that extensional tectonics as Tortonian (Late Miocene) and/or
the MMM was a result of the burial of the massif area younger. According to Seyito(cid:219)lu & Scott (1991, 1992),
beneath the southward moving Lycian nappes — rooted the palynological ages from the E—W-trending B(cid:159)y(cid:159)k
from the (cid:220)zmir-Ankara Neotethyan suture zone, thus Menderes Graben show that in western Turkey, the N—S
causing regional metamorphism and deformation of the extensional tectonics had begun during latest
massif ((cid:222)eng(cid:154)r & Y(cid:221)lmaz 1981; (cid:222)eng(cid:154)r et al.1984). On Oligocene—Early Miocene. The fact that the Late Miocene
the other hand, the existing structures formed during the and Plio-Quaternary tectonic evolution of this region is of
MMM indicate a top-to-the-NNE tectonic transport the extensional nature and still active is also
(Bozkurt 1995; Hetzel et al. 1998; Bozkurt & Park demonstrated by seismic studies. Eyido(cid:219)an (1988)
1999; Bozkurt 2001b; Bozkurt & Oberh(cid:138)nsli 2001a). reported extension of 13.5 mm/yr based on seismicity
Temperatures during the (cid:212)MMM(cid:213) reached ~550 ¡C while over the last 40 years. Volcanic activity, whose increase
pressure is estimated as £ 5 kbar (Whitney & Bozkurt coincided with the neotectonic phase, was studied in
2002). Subsequent exhumation occurred along originally detail by Ercan et al.(1985).
high-angle but presently low-angle normal faults during
Geophysical studies and drilling have shown a normal
Miocene time (e.g., Bozkurt & Park 1994, 1997a, b;
fault structure, resulting in stepwise graben formation,
Hetzel et al. 1995a, b, 1998; Verge 1995; Hetzel &
which is also characteristic of the Germencik, Salavatl(cid:221),
Reischmann 1996; Ko(cid:141)yi(cid:219)it et al.1999; Bozkurt 2000,
and K(cid:221)z(cid:221)ldere geothermal fields in the B(cid:159)y(cid:159)k Menderes
2001a, b; Gessner et al.2001a, b; G(cid:154)kten et al.2001;
Graben (Figure 1). For further information the reader is
I(cid:223)(cid:221)k & Tekeli 2001; Lips et al. 2001; Bozkurt &
referrred to Konak et al.(1987) and Dora et al.(1992).
Oberh(cid:138)nsli 2001a; S(cid:154)zbilir 2001, 2002; Seyito(cid:219)lu et al.
Broad E—W-striking normal graben faults cut across
2002).
nearly 100-m-thick cataclasites, which were formed at
180
(cid:220). H. KARAMANDERES(cid:220) & C. HELVACI
the base of detachment faults, and non-metamorphic 1965) and also in the cross-section between the AS-1 and
Neogene sediments on the crystalline basement (Hetzel et AS-2 wells (Figures 3 & 4).
al. 1995b). Several intermediate to basic volcanic
Tertiary sedimentary rocks, which have been filling
extrusions and geothermal springs in the central parts of
the graben that developed as result of neotectonic
the Menderes Massif are directly related to the graben
activity, have been deposited over the metamorphic
system. Early fossil geothermal systems developed along
basement. These Neogene sedimentary rocks include
tectonic zones during the dome-forming period. The
coarse- and fine-grained sandstones, siltstones, and well-
development and evolution of these systems are related
cemented conglomerates, and are separated by a thin
to neotectonic activity (Figure 2).
lignite layer at the base of the sequence. Sediments
Although the Menderes Massif has been the subject of thicker than 1000 m have been drilled through in the
intense research since 1990s there are still many B(cid:159)y(cid:159)k Menderes Graben at the Germencik-(cid:133)merbeyli
problems concerning the lithology, age, structure, geothermal field (Karamanderesi et al.1987). Travertine
deformation and metamorphism of the Menderes Massif. deposits, precipitated from cold or hot springs along the
We therefore suggest that readers refer to Bozkurt & faults, are present locally. Hot springs having 32¡C
Oberh(cid:138)nsli (2001a, b) for further reading. temperatures near Malga(cid:141)emir village are evidence of
present geothermal activity.
Based upon their mineral parageneses (Table 1),
Geology of the Ayd(cid:221)n-Salavatl(cid:221) Area
metamorphic rocks of the Menderes Massif are known to
The Ayd(cid:221)n-Salavatl(cid:221) geothermal field is located in the
be the products of regional metamorphism characterized
north-central part of the B(cid:159)y(cid:159)k Menderes Graben, and
by medium to high temperature and pressure. A mineral
covers an area about 8 km long and 2 km wide (Figure
paragenesis including chlorite - biotite - muscovite -
2). The geological sequence of this area includes
garnet - staurolite - kyanite - sillimanite occurs within
orthogneiss and paragneiss, fine-grained schists, coarse-
allochthonous augen gneisses and cover schists.
grained augen gneiss, mica schist, quartz schist,
Observations within the massif show that large
metaquartzite and marble units. Structural analysis shows
fissures and fracture zones developed during neotectonic
that these units have been reverse-faulted and that the
activity, and quartz veins and calcite and chlorite veins
gneisses have been thrusted over the schists and marbles.
occur in swarms related to deep-seated intrusive bodies.
These structures can be seen at the surface (Akartuna
KaraT.(976m) SE
NW
1000m
750
AS-1 500
C
A LEGEND
250
0s.l
QUATERNARY alluvium
-250
PLIOCENE clay-marl-sandstone
-500
MIOCENE sandstone-siltstone-limestone -750
marble F1 F2 F3 F4 A-1000
PALAEOZOIC
micaschist AS-1well
formationboundary normalfault
gneiss probableformationboundary disconformity
probablefault overthrust
0 500 1000m
Figure 3. Geological cross-section of the Ayd(cid:221)n-Salavatl(cid:221) geothermal field (see Figure 2 for location).
181
AYDIN-SALAVATLI GEOTHERMAL FIELD, WESTERN ANATOLIA
SW NE
AS-2 AS-1
50
m 0
-100
Pliocene Pliocene
Miocene Miocene
allochthonousgneiss
-500
Bozk(cid:246)y overthrust
schist
1stE-WFault
Marble
-1000 962m 2ndE-WFault
N
-
marble S marble
F
a
ult
schist
-1500 schist
200m 1510m
lossofcirculation
Figure 4. Cross-section through the Ayd(cid:221)n-Salavatl(cid:221) geothermal field (see Figure 2 for location).
These intrusives are not exposed because of the greater zones at the altitudes of the regional discharge zones.
depths of their magma chambers, but a few outcrops Fracture-related mineralization includes epidote, pyrite,
bearing rutile, titanite, limonite, quartz, calcite and arsenopyrite, garnet and clay minerals. An example of
siderite can be observed in the Ovac(cid:221)k plateau at the such an outcrop is at the Kabakl(cid:221)dere locality. Toward the
northern end of the study area (Figure 2). The erosion south, a similar sort of activity is present within the
surfaces of these outcrops have altitudes of 900 m. vicinity of Malga(cid:141)emir and Azapderesi. The gabbro
intrusion exposed near Malga(cid:141)emir village continues to be
From the Ovac(cid:221)k plateau toward the south at lower
a heat source (Figure 2).
altitudes, dykes of gabbro and its derivatives, which have
intruded along small-scale fracture zones and cooled Travertine deposits along fossil discharge areas are at
during the Quaternary, are present. Silicified zones have an altitude of 550 m due to regional neotectonic uplift.
developed along the margins of these dykes. The Quartz veins and travertine deposits are exposed at a
mineralogical composition of the gabbroic intrusive rocks discharge altitude of 600 m in Azapderesi village. Quartz
(of Early Miocene age [or post-metamorphic]) is as veins facilitated the development of alteration zones of
follows: plagioclase, clinopyroxene, orthopyroxene, dolomite, calcite, quartz, and clay along fracture zones
olivine, biotite, uralite, zoisite, chlorite, apatite, magnetite within the host rock.
and garnet. Locally, these gabbroic rocks have schistose
The fault systems, clearly traceable around Salavatl(cid:221),
textures. Where erosion has been slow, travertine
Eskihisar and G(cid:159)vendik villages where regional
deposits are present along the margins of these silicified
neotectonic activity continues, are imprints of partially
182
(cid:220). H. KARAMANDERES(cid:220) & C. HELVACI
Table 1. Mineral paragenesis of surface samples and well cuttings in the Ayd(cid:221)n-Salavatl(cid:221) geothermal field.
Regional metamorphic or
Mineral relict, from igneous and/or Metasomatic or early Active hydrothermal
sedimentary mineral assemblages hydrothermal stage stage
oligoclase __________________
andesine __________________ __________________
albite __________________ __________________
sillimanite __________________
biotite __________________ __________________
muscovite __________________ __________________
garnet* ______________ (1st) ______________ (2nd)
tourmaline* ______________ (1st) ______________ (2nd) __________________
apatite __________________ __________________ __________________
epidote __________________ __________________
zircon __________________ __________________
pyrite __________________ __________________
siderite __________________ __________________
dolomite __________________ __________________
calcite __________________ __________________ __________________
vermiculite __________________ __________________
hydrobiotite __________________ __________________
quartz __________________ __________________ __________________
illite __________________ __________________
kaolinite __________________ __________________
dickite __________________ __________________
montmorillonite __________________ __________________
chlorite __________________ __________________ __________________
opaque mineral(s) __________________ __________________ __________________
* _ Two different stages of mineral crystallisation.
cooled intrusives. Vein mineralization of calcite, quartz, temperatures were measured with Amerada logging tools
gypsum, sulphur, pyrite and clay occurs along these as 169.77—175.62¡C (Tables 4 & 5). The chemistry of
faults. It has been observed that travertine and the waters was determined to be of the Na-K bicarbonate
travertine-sulphur deposits are located in NE—SW- and type. Naturally, it is necessary to determine the chemistry
N—S-trending fault zones, respectively (Figure 2). The of the encrustation that will develop from these sorts of
N—S-trending faults can be correlated with cross-faults waters, which, in this case, precipitate calcite and illite.
described by (cid:222)eng(cid:154)r (1987), and are illustrated in Figures Water samples were taken from the total discharge of the
2 and 4. wells thrown out into the atmosphere. Total discharge
was measured from the well, which had been opened for
Sulphur efflorescence related to the fracture zones is
a vertical production test. Total discharge data are as
exposed at a 100-m altitude to the east of Salavatl(cid:221)
follows WHP (bar) 2.27; Patm: 14.6 psi.a; 11% steam,
village, and sulphur deposits with travertine are exposed
297 t of water; 39.8 t of steam. Total production was
at the same altitude at G(cid:159)vendik village. At an altitude of
calculated at 336.8 t/h.
50 m, calcite, quartz, clay and sulphur efflorescence occur
between Sultanhisar and At(cid:141)a (Figure 2). Sulphur The mineralized zones observed along the N—S
efflorescence, clays, gypsum and small-scale carbonate traverse, as mentioned above, are related to E—W fault
mineralization are surface geothermal manifestations systems which become younger toward the south. This
along these faults. type of structure can be observed clearly in the NW—SE
cross-section (Figure 3). There are two N—S-trending
The chemical composition of geothermal waters is
strike-slip faults that form the east and west boundaries
shown in Table 3. The reservoir temperature, with
respect to the chemical composition given in Table 3, has of the Salavatl(cid:221) geothermal field; the first outcrop is
been stated to be 160—175¡C according to the method of exposed in Yavuzk(cid:154)y village and the second outcrop is
Giggenbach (1986). Also, the values of two deep well between G(cid:159)vendik-Malga(cid:141)emir villages and Sultanhisar.
183
AYDIN-SALAVATLI GEOTHERMAL FIELD, WESTERN ANATOLIA
Table 2. XRD results for well AS-1 clay samples.
Sample Well depth Temperature Air-dried Mg-ethylene glycol K-550 ¡C K-700 ¡C Probable
(m) (T ¡C) lines d(cid:129) lines d(cid:129) lines d(cid:129) lines d(cid:129) minerals
17.32 less montmorillonite
7657 6 52.1 10.15 10.04 10.15 illite
7.18 7.13 kaolinite
17.32 montmorillonite
7658 50 52.1 10.04 10.04 10.04 illite
7.13 7.19 kaolinite
8231 287 64.6 10.04 10.04 10.04 10.04 illite
7.13 7.13 7.13 dickite
17.65 montmorillonite
7927 312 64.6 10.15 10.15 10.15 illite
7.22 7.22 kaolinite
17.65 montmorillonite
7928 328 64.6 10.22 10.15 10.15 illite
7.22 7.22 7.22 kaolinite
7930 502 70.9 10.04 10.08 10.08 illite
7.13 7.15 kaolinite
17.51 montmorillonite
7931 556 77.1 10.04 10.15 10.15 illite
7.13 7.18 kaolinite
7932 566 77.1 10.08 10.15 10.04 illite
7.18 7.18 kaolinite
11.04 hydrobiotite
7933 576 77.1 10.04 10.04 10.04 illite
7.15 7.13 kaolinite
13.18 15.23 chlorite
8232 576 77.1 10.64 10.04 montmorillonite
9.92 9.82 illite
13.38 14.96 vermiculite
8233 583 77.1 10.59 13.18 10.07 chlorite
9.93 illite
7934 682 88.1 10.04 9.99 9.99 illite
7.18 7.13 kaolinite
12.61 16.99 montmorillonite
8234 682 88.1 9.98 9.93 10.04 illite
7.10 7.13 kaolinite
7935 706 88.1 10.04 10.04 10.04 illite
8235 706 88.1 9.92 9.92 9.92 illite
7.07 7.07 chlorite
7938 732 101.3 10.04 10.04 10.04 illite
8239 766 122.6 9.92 9.92 9.92 illite
8240 778 127.6 9.86 9.92 9.98 illite
7.13 7.19 kaolinite
8242 990 131.9 10.04 9.98 9.98 illite
8243 1100 162.75 9.92 9.93 9.93 illite
184