Genesis of the hydrothermal Karaçayır kaolinite deposit in Miocene volcanics and Palaeozoic metamorphic rocks of the Uşak-Güre Basin, western Turkey

Turkish Journal of Earth Sciences
/>
Research Article

Turkish J Earth Sci
(2013) 22: 444-468
© TÜBİTAK
doi:10.3906/yer-1112-2

Genesis of the hydrothermal Karaçayır kaolinite deposit in Miocene volcanics and
Palaeozoic metamorphic rocks of the Uşak-Güre Basin, western Turkey
Selahattin KADİR*, Hülya ERKOYUN
Department of Geological Engineering, Eskişehir Osmangazi University, TR-26480 Eskişehir, Turkey
Received: 05.12.2011

Accepted: 02.07.2012

Published Online: 06.05.2013

Printed: 06.06.2013

Abstract: The Karaçayır kaolinite deposit, situated in the Uşak-Güre basin of western Turkey, is hosted by rhyolite and andesite of
the Miocene Dikendere volcanics, and by muscovite schist, glaucophane schist, talc schist and chlorite schist of the Palaeozoic Eşme
Formation. The association of kaolinization with silicification and Fe-oxidation, and the presence of pyrite, chalcopyrite and gypsum,
suggest that hydrothermal alteration processes in the volcanics and schists were controlled by faults. Thus, prevalent kaolinite is associated
with quartz, smectite, illite and opal-CT in the centre of the deposit, with relative increases in smectite, illite, chlorite and Fe (oxyhydr)
oxide phases outwards and upwards. Texturally, sanidine and plagioclase crystals are sericitized and kaolinized in rhyolite and andesite
respectively, whereas muscovite, chlorite and feldspar in schists exhibit partial kaolinization and illitization. Micromorphologically,
authigenic kaolinite, having hexagonal book-like and vermiform textures, occurs as rims on feldspar, muscovite and chlorite suggesting
a dissolution-precipitation mechanism. Pyrite, locally transformed to hematite, is euhedral to subhedral, with grain sizes of ±400 µm.
Iron occurs as Fe2+ and Fe3+ within the structures of the Karaçayır kaolinites and smectites, as determined by Mössbauer spectroscopy.

Enrichment of Mg, Ca and Fe in the kaolinite deposit is related to the presence of smectite, calcite, dolomite, pyrite ± chalcopyrite,
goethite and hematite. Kaolinized volcanic and schist samples from the Karaçayır area are characterized by 35.77-87.58% SiO2, 3.2722.83% Al2O3, 0.91-9.16% Fe2O3, 0.01-5.94% K2O and 0.26-12.41% MgO, revealing moderate degrees of kaolinization ± illitization
± smectitization coexistent with high degrees of silicification and Fe (oxyhydr)oxidation. Increases of Fe2O3, MgO, CaO and Zr and
decreases of Rb, Sr, and Ba (except for decreases in partially altered volcanics) in kaolinite samples adjacent to schists and volcanic rocks
suggest that kaolinite developed by alteration of both schists and volcanics. The Karaçayır kaolinite and smectite have δ18O and δD values
ranging from 11.6 to 20.4‰, and -79‰ to -112‰, respectively. Using the isotopic fractionation factor (α), the temperatures of formation
for the Karaçayır kaolinite and smectite were determined to be 61.6-131.7 °C and 61.2-148.9 °C, respectively, and negative δ34S values
for pyrite, chalcopyrite and gypsum reflect formation under the influence of hydrothermal activity; this assumption is supported by
isotope equilibrium temperatures of 80-125 °C calculated from pyrite-chalcopyrite pairs. Thus, the Karaçayır kaolinite deposit formed
by an increase in Al±Fe/Si under acidic environmental conditions, which facilitated epithermal alteration of feldspar and volcanic glass
in volcanic rocks, and muscovite, chlorite and feldspar in schists, controlled by tectonic activity during Miocene volcanism.
Key Words: Uşak, hydrothermal alteration, kaolinite, Miocene volcanites, Palaeozoic metamorphics, mineralogy, geochemistry, stableisotope geochemistry

1. Introduction
Hydrothermal kaolinite deposits in Turkey typically
occur within volcanics (Seyhan 1978; Sayın 2007; Ece &
Schroeder 2007; Ece et al. 2008; Erkoyun & Kadir 2011;
Kadir et al. 2011). Occurrences of hydrothermal kaolinite
in metamorphic rocks are scarce (Kadir & Akbulut 2009).
Hydrothermal kaolinite deposits generally develop under
the control of an active tectonic environment and with the
presence of permeable units so that hydrothermal fluids
can be flushed through igneous or metamorphic rocks
(Murray & Keller 1993).
The Karaçayır kaolinite deposit is of economic
importance, with approximately one million tonnes of
*Correspondence:

444

reserves (8th Five-Year Development Plan – State Planning
Organisation of Turkey 2001), and is developed in both
volcanic rocks (rhyolite and andesite) and metamorphic
rocks (muscovite schist, glaucophane schist, talc schist
and chlorite schist) by hydrothermal alteration under the
control of tectonic activity.
To date, the geology, mineralogy, geochemistry
and technological properties of the Karaçayır kaolinite
deposit have been studied (Seyhan 1972; Karaağaç 1975,
Karaağaç et al. 1975, Fujii et al. 1995). Furthermore,
the region has been studied for its Quaternary thermal
water (Davraz 2008); the distribution of thermal waters
in Turkey is controlled by fault systems and proximity


KADİR and ERKOYUN / Turkish J Earth Sci
to Tertiary-Quaternary volcanics (Mutlu & Güleç 1998).
Although Kadir & Akbulut (2009) studied the mineralogy,
geochemistry and genesis of the Taşoluk kaolinite deposit
in the Afyonkarahisar (western Anatolia) area, which
developed in both pre-Early Cambrian sericitic micachlorite schist and Neogene volcanics, there have been
no detailed micromorphological (transmission electron
microscopy), 57Fe Mössbauer spectroscopic, geochemical
(modelling of mass gains and losses of major-, trace- and
rare-earth elements during alteration), and kaolinitefraction stable-isotopic (including calculation of formation
temperatures) studies of the Karaçayır kaolinite deposits,
which are related to Palaeozoic mica schist, glaucophane
schist, talc schist, calcareous schist and chlorite schist. The
object of the present study was to investigate in detail the
geological, mineralogical and geochemical aspects, as well

as the genesis, of this hydrothermal kaolinite deposit within
Miocene volcanics and Palaeozoic metamorphic rocks,
and to demonstrate the significance of these data and their
interpretation as important tools in future exploration for
tectonic-controlled hydrothermal-alteration systems and
related kaolinite deposits throughout Anatolia.
2. Geology and general features of the Karaçayır deposit
The basement rocks of the area comprise talc schist, mica
schist, glaucophane schist, chlorite schist and calcareous
schist (Eşme Formation) of Palaeozoic age (Ercan et
al. 1977). These units are overlain unconformably by
lacustrine sediments of the Early Miocene Hacıbekir
group [the Kürtköyü (exposed outside the study area) and
Yeniköy formations], comprising conglomerate, claystone,
sandstone, dolomitic marble and thin layers of tuff and
tuffite, with cross-cutting rhyolite, rhyodacitic lavas and
related tuffs, the latter collectively termed the Dikendere
volcanics (Figures 1 and 2). The research of Seyitoğlu
(1997) included K-Ar dating (20-18.9 Ma) of volcanic
samples from the Hacıbekir group, indicating an Early
Miocene age.
These units are unconformably overlain by the Middle
Miocene İnay group, comprising the Ahmetler formation
(conglomerate, claystone, siltstone), the Beydağ volcanics
(andesitic to rhyolitic lavas and pyroclastic deposits),
the Ulubey formation (lacustrine limestone), and the
Payamtepe volcanics (lava flows and dykes) (Karaoğlu et al.
2010). The Ahmetler, Ulubey and Payamtepe formations
are exposed outside the study area. 40Ar/39Ar radiometric
data from biotite, amphibole and sanidine crystals and

groundmass (12.15±0.15–17.29±0.13 Ma) of the İnay
group suggest an Early-Middle Miocene age (Karaoğlu et
al. 2010).
These units are overlain unconformably by the
Upper Miocene Asartepe formation, comprising fluvial
conglomerate, sandstone, and, locally, marl and limestone.
Seyitoğlu et al. (2009) reported a biostratigraphic and

magnetostratigraphic age of 7 Ma for the Asartepe
formation. All of the aforementioned units are overlain
unconformably by Quaternary fluvial alluvium.
The Karaçayır kaolinite deposit developed within
both Palaeozoic metamorphics and Miocene volcanics
controlled by an NE-SW-oriented normal fault zone
part of the tectonic regime in the Uşak-Güre basin. This
basin possibly developed during and after collision of
the Arabian and Eurasian plates, with subduction of the
African plate under the Aegean-Anatolian plate along the
Hellenic and Cyprean trenches, and following back-arc
spreading (Ring & Layer 2003; Ring et al. 2010; Karaoğlu
et al. 2010) (Figure 1). This deposit comprises a silicified
kaolinite zone, an illitic-smectitic zone, an Fe (oxyhydr)
oxide zone, and silicified and Fe-oxidation zones, and
is hosted by volcanic rocks (rhyolite and andesite) and
metamorphic rocks (talc schist, mica schist, chlorite schist
and glaucophane schist) as controlled by the tectonic
regime (Figure 3a-e). The silicified kaolinite zone at the
centre of the deposit is white and is vertically and laterally
transitional into altered volcanics and schists. The kaolinite
zone encloses irregular grey illite, brown smectite, and

silica lenses (Figure 3f,g). Locally, manganese (oxyhydr)
oxide impregnation also is present within the kaolinized
zone and, locally, as 1–10-mm-thick coatings on schists
(Figure 3h). The volcanics and metamorphics are
characterised by moderate to high degrees of alteration.
Talc schist locally encloses Fe (oxyhydr)oxide phases and
disseminated pyrite and chalcopyrite. Glaucophane schist
is dark blue and moderately hard. A yellowish-brown Fe
(oxyhydr)oxide zone locally containing gypsum crystals
is located in the upper part of the illitic-smectitic zone
and alternates with it (40 cm to 2 m thick). A dark-brown
silicified and Fe (oxyhydr)oxide zone is situated on top
of the deposit as silicic and Fe-oxidised horizons (~5 m).
Silicification and Fe (oxyhydr)oxide phases are abundant
within the Karaçayır kaolinite deposit.
3. Methods
In order to identify the lateral and vertical distribution of
kaolinite and coexisting clay and non-clay minerals, the
volcanics and metamorphics of the Karaçayır kaolinite
deposit were sampled (Figures 1 and 2). One hundred and
forty samples, reflecting various degrees of alteration, were
analysed via polarised-light microscopy (Leitz Laborlux
11 Pol), polished-section microscopy (Leitz MPV-SP),
X-ray powder diffractometry (XRD) (Rigaku-Geigerflex),
scanning electron microscopy (SEM-EDX) (JEOL JSM
84A-EDX), and transmission electron microscopy
(TEM) (JEOL JEM-21007) in order to determine their
mineralogical characteristics.
XRD analyses were performed using CuKα radiation
and a scanning speed of 1° 2θ/min. Randomly selected

powders of whole-rock samples were used to determine

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KADİR and ERKOYUN / Turkish J Earth Sci

N
Mezarardı Sırtı

Güney

Eğlence
Karaçayır
Koca Tepe

Paşacılar

Ciğerdede
3 km

UŞAK

AEGEAN SEA

BLACK SEA
ANKARA
KÜTAHYA

T U R K E Y

UŞAK Study area
100 km

metagranite

high-angle normal fault

Asartepe
Formation

Upper

Karaçayır kaolinite deposit

undifferentiated
continental
clastic rock
continental
carbonate rocks
andesite, rhyolite
and pyroclastic rocks

Beydağ
volcanites

rhyolite, rhyodacite.tuff
and agglomerate

Dikendere

volcanites

continental
clastic rocks

Yeniköy
Formation

Hacıbekir Group İnay Group

schist

Miocene
Middle

Palaeozoic

marble

alluvium

Lower

ophiolite

Musadağı Vezirler
Eşme
Formation marble
mélange

Mesozoic

EXPLANATION

Quaternary

MEDITERRANEAN
SEA SEA
MEDITERRANEAN

undefined fault
residential area

Figure 1. Geological map of the Karaçayır kaolinite deposit and surrounding area (modified from
Akdeniz & Konak 1979; Karaoğlu et al. 2010).

446


R.

LITHOLOGY

EXPLANATION

Upper

0-30

E

AT
QU

THICKNESS
(m)

MEMBER

FORMATION

GROUP

SERIES

SYSTEM

UPPER
SYSTEM

KADİR and ERKOYUN / Turkish J Earth Sci

Middle

MIOCENE

NEOGENE

TERTIARY

CENOZOIC

unconformity

UPPER

US
EO
ET
AC
CR

PERMOTRIASS

PALAEOZOIC

MESOZOIC

Lower

unconformity

Vezirler
mélange

ophiolitic mélange

unconformity
marble

Figure 2. Simplified general stratigraphic section for the study area (modified from Akdeniz & Konak 1979; Karaoğlu et al.

2010).

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KADİR and ERKOYUN / Turkish J Earth Sci

illite
silica cap + Fe (oxyhydr)oxide
kaolinite +
Fe (oxyhydr)oxide

kaolinite
smectite+illite

10 m

a

b

1m

kaolinised andesite
altered schist

c

d

1m

altered schist

smectite

kaolinite

e

0.5 m

f

kaolinite

illite

manganese (oxyhydr)oxide

kaolinite

g

20 cm

h

2m

Figure 3. Field photographs: a. a general view of the Karaçayır kaolinite deposit; b. a close-up view of an
illite lens and Fe (oxyhydr)oxide-bearing phases in kaolinized units outward from the kaolinite deposit;
c. a close-up view of kaolinized andesite in the kaolinite deposit; d. a close-up view of partially altered
schist; e. a close-up view of altered schist; f. a smectite lens developed within the kaolinite unit; g. an
illite nodule developed within the kaolinized unit; h. manganese (oxyhydr)oxide minerals developed
within the kaolinized unit.

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KADİR and ERKOYUN / Turkish J Earth Sci
bulk mineralogy. Clay mineralogy was determined via
separation of the clay fraction (<2 µm) by sedimentation,
followed by centrifugation of the suspension, after
overnight dispersion in distilled water. The clay particles
were dispersed by ultrasonic vibration for about 15
minutes. Four oriented specimens of the <2 µm fraction
were prepared from each sample, then air-dried, ethyleneglycol-solvated at 60 °C for 2 hours, and thermally treated
at 350 °C and 550 °C for 2 hours. Semi-quantitative relative
abundances of rock-forming minerals were obtained
using the method of Brindley (1980), whereas the relative
abundances of clay-mineral fractions were determined
using their basal reflections and the intensity factors of
Moore and Reynolds (1989).
Representative clay-rich bulk samples were prepared
for SEM-EDX analysis by fixing the fresh, broken surface of
each rock sample onto an aluminium sample holder using
double-sided tape, and each sample was subsequently
coated with a thin film (~ 350 Å) of gold using a Giko
model ion coater. The clay particles for TEM analysis

were dispersed in an ultrasonic ethanol bath for about 30
minutes, and one drop of clay suspension was placed on a
carbon-coated copper grid and dried at room temperature.
Purified ferruginous-facies samples were analysed
by Mössbauer spectroscopy (MS) (Wissel Mössbauer
spectrometer). Room-temperature (RT) and 300 K spectra
were collected using a constant-acceleration drive with
triangular reference signal using 50mCi source 57Co in a
Pd-matrix. Velocity calibration was acquired from the MS
of a standard α-Fe foil at RT, and isomer shifts are quoted
relative to α-Fe. The spectra were fitted either with discrete
Lorentzian doublets and/or sextets, or with a modelindependent hyperfine field distribution (Wivel & Mørup
1981).
Thirty-one whole-rock samples of fresh, partially
altered and highly altered volcanics and schist were
manually crushed and powdered using a tungsten carbide
pulveriser, and then were analysed by ICP-AES for major
and trace elements and ICP-MS for rare-earth elements
(REE) at Acme Analytical Laboratories Ltd. (Canada). The
detection limits for the analyses were between 0.01 to 0.1
wt.% for major elements, 0.1 to 5 ppm for trace elements,
and 0.01 to 0.5 ppm for REE.
Enrichments and depletions of elements have been
estimated using the procedure of MacLean & Kranidiotis
(1987). In these calculations, Al was assumed to be the
most immobile element, based upon calculated correlation
coefficients with other elements. All samples were grouped
on the basis of degree of alteration (average result from
each group), and the gains and losses of components
were calculated using a starting mass of 100 grams of

average fresh anhydrous sample. The equation used in the
calculations (MacLean & Kranidiotis 1987) can be written
for SiO2 as:


SiO2 wt% altered rock
SiO2 = --------------------- Х Al2O3 wt% fresh rock

Al2O3 wt% altered rock
Using the above formula, gains and losses of
mass (ΔCi) for each element were determined by
subtracting the calculated values (RC) from the
concentrations of the components in the least-altered
samples.
Three kaolinite- and two smectite-bearing
representative samples from areas proximal to highly
altered volcanics and schist in the central and upper parts
of the kaolinite deposit were purified and analysed for the
stable isotopes H and O by Activation Laboratories Ltd.
(Actlabs) in Canada. The results of H-isotopic analyses,
made by conventional isotope-ratio mass spectrometry, are
reported in the familiar notation, namely per mil relative
to the V-SMOW standard. The procedure described above
was used to measure a δD value of -65‰ for the NSB30 biotite standard. O-isotopic analyses were performed
on a Finnigan MAT Delta, dual inlet, isotope-ratio mass
spectrometer, following the procedures of Clayton &
Mayeda (1963). The data are reported in the standard delta
notation as per mil deviations from V–SMOW.  External
reproducibility is ± 0.19‰ (1σ), based on repeat analyses
of an internal white crystal standard (WCS). The NBS 28

value is 9.61 ± 0.10‰ (1σ).
One each of the pyrite, chalcopyrite and gypsum
samples were selected from crushed bulk samples using a
binocular microscope and analysed for sulphur isotopes
by Activation Laboratories Ltd. (Actlabs) in Canada. A
pure gypsum sample was combusted to SO2 gas under ~103
Torr of vacuum. The SO2 was taken in directly from the
vacuum line to the ion source of a VG 602 isotope-ratio
mass spectrometer (Ueda & Krouse 1986). Quantitative
combustion to SO2 was achieved by mixing 5 mg of sample
with 100 mg of a V2O5 and SO2 mixture (1:1). The reaction
was carried out at 950 °C for 7 minutes in a quartz-glass
reaction tube. Pure copper turnings were used as a catalyst
to ensure conversion of SO3 to SO2. Internal lab standards
(Sea WaterBaSO4 and FisherBaSO4) were run at the beginning
and end of each set of samples (typically 25) and were
used to normalise the data as well as to correct for any
instrumental drift. All results are reported in the δ34S‰
notation relative to the international CDT standard.
Precision (1 sigma) using this technique is typically better
than 0.2 per mil (n=10 internal lab standards).
4. Results
4.1. Petrographic determinations
Rhyolite and andesite have hypocrystalline porphyritic
texture and contain quartz, sanidine, plagioclase, biotite,
hornblende, tridymite and apatite (Figure 4a,b). Quartz is
subhedral and locally corroded. Sanidine is characterised by

449

KADİR and ERKOYUN / Turkish J Earth Sci

oxyhornblende

plagioclase

oxybiotite
0.2 mm

0.2 mm

Fe (oxyhydr)oxide
kaolinised muscovite

c

0.2 mm

0.2 mm

g
muscovite

kaolinite + sericite
0.2 mm

f

0.2 mm

0.2 mm

e
chlorite
talc

g

0.2
0.2 mm
mm

h

0.2
0.2mm
mm

Figure 4. Photomicrographs showing: a. altered feldspar and groundmass within andesite, plane-polarised
light (EG1-1); b. opacitized hornblende in devitrified groundmass of rhyolite, plane-polarised light (KC53); c. kaolinized and iron-oxidised rhyolite, plane-polarised light (KC2-4); d-f. altered and deformed
muscovite schist, crossed polars (KC1-39; KC1-56, KC1-34); g. view of chlorite schist, plane-polarised
light (KC1-55); h. view of talc schist, crossed polars (KC1-37).

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KADİR and ERKOYUN / Turkish J Earth Sci
Table 1. Mineralogical variation within the Karaçayır kaolinite deposit and host volcanics and metamorphics. kao: kaolinite, smc:
smectite, ill: illite, chl: chlorite, gyp: gypsum, fds: feldspar, qtz: quartz, op: opal-CT, cal: calcite, dol: dolomite, amp: amphibole, tlc: talc.

acc: accessory, +: relative abundance of mineral.
Sample
KC1-1
KC1-2
KC1-3
KC1-4
KC1-5
KC1-6
KC1-7
KC1-12
KC1-14
KC1-16
KC2-1
KC2-2
KC2-3
KC2-5
KC2-6
KC2-7
KC2-8
KC2-10
KC2-11
KC2-14
KC3-1
KC3-8
EG1-7
EG1-8
EG1-9
EG1-10
EG1-11
EG1-13

EG1-14
EG1-17
EG1-19
KC1-27
KC1-28
KC1-30
KC1-31
KC1-32
KC1-33
KC1-34
KC1-35
KC1-36
KC1-37
KC1-38
KC1-39
KC1-40
KC1-41
KC1-44
KC1-48
KC1-49
KC1-52
KC1-55
KC1-57
KC1-59
KC2-17

Rock Type
altered tuff
partially altered tuff
altered tuff

altered tuff
partially altered tuff
altered tuff
altered tuff
partially altered tuff
altered tuff
dolomite
partially altered tuff
partially atered tuff
partially altered tuff
partially altered tuff
partially altered tuff
partially altered tuff
partially altered tuff
altered tuff
partially altered tuff
partially altered tuff
altered tuff
altered tuff
altered tuff
altered tuff
altered tuff
altered tuff
altered tuff
altered tuff
limestone
altered tuff
altered tuff
muscovite schist
altered schist

altered schist
altered schist
muscovite schist
altered schist
altered schist
dolomite
altered schist
altered talc schist
altered schist
quartzite
altered schist
altered schist
altered schist
altered schist
altered schist
altered schist
chlorite schist
altered schist
altered schist
altered schist

kao
acc
acc
acc
+
acc
+
acc
acc

acc
+
acc
+
acc
acc
+
+
acc
acc
acc
+
+
acc
acc
acc
+++
acc
acc
+++
++
acc
acc
acc
+++
++
+
+
acc
+

+
++
acc
+++
+
acc
++
acc

smc
acc
acc
+
acc
+
+
acc
acc
acc
+
acc
acc
+
acc
+
+
+++
acc
acc
++

+
+++
+
++++
acc
acc
acc
acc
+
+
++
+++
acc
++
+
acc
acc
acc
+
+++
+
acc
acc

ill

chl

gyp

acc
acc
+
+
acc
acc
++
++

acc

+
acc
acc
acc
acc
+
acc

acc
+

++

+
acc
acc
+
acc
acc

++++
++
+++
++++
+
+
++
+++
+
+
++
+++
+++
+++
+++
++
++

acc

acc
acc
acc
+
acc
+

+
acc

+
++
acc
acc
acc
acc
+

++
acc
acc
+
acc

++

+
+
++

+++

+++
++
+

acc

acc

++
+++

++

op

acc
acc

acc

+
+

qtz

acc
acc

+
acc
acc
+
acc

acc

fds

+
acc

+++
+

acc

++

++++
++++
++
++
acc
+
acc
+
++++
++++
acc
++
++
+++
acc
+
acc
+++
+
+

+
acc
+
++++
acc
++
acc
++
+
++
+
++
++
+

acc
acc
+
acc
acc
acc
acc
acc
acc
+
acc

+

cal

dol

acc
acc

++
+

amp

tlc

++
+++
acc

++
++++

acc
+
+
acc

+

+

++++

++++
+

acc

acc

++++
acc
+

+
acc

+++++

acc

acc

acc

acc
acc

++
acc

acc

+

++

+

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KADİR and ERKOYUN / Turkish J Earth Sci
partial corrosion, argillization, sericitization and carlsbad
twinning. Plagioclase (oligoclase) is argillized. Biotite and
hornblende are partially to completely opacitized (Figure
4b). Reddish-brown opaque phases such as Fe (oxyhydr)
oxide occur along veins, and volcanic glass is devitrified
(Figure 4c).
Muscovite schist comprises muscovite and quartz,
and shows evidence of both foliation and deformation
(Figure 4d-f). Fe-oxidation, opacitization, sericitization
and kaolinization are widespread. Chlorite schist has
lepidoblastic texture and consists of chlorite, quartz,
plagioclase (oligoclase), diopside and carbonate minerals
(Figure 4g). Chlorite and plagioclase exhibit argillization.
Microfractures are filled by Fe-oxides and micritic calcite.
Talc schist comprises talc, antigorite, feldspar, quartz and
calcite (Figure 4h). Feldspar crystals are both argillized and
carbonatized. Talc crystals rim antigorite. Glaucophane
quartzite is made up of glaucophane, quartz, muscovite
and feldspar.
Pyrite and Fe (oxyhydr)oxide phases coexisting with

quartz were identified using reflected-light microscopy.
Pyrite is euhedral to subhedral with grain sizes of ±400
µm; locally it is replaced by hematite.
4.2. XRD determinations
The XRD results from bulk samples taken from the
kaolinite deposit are given in Table 1 and Figure 5.
Volcanic samples consist mainly of quartz, associated with
kaolinite, smectite, illite, opal-CT and feldspar. However,
schist samples comprise talc, chlorite and glaucophane
associated with kaolinite, smectite, illite, calcite, dolomite,
quartz and accessory pyrite. Concentrations of kaolinite,
smectite, illite and chlorite are relatively higher in altered
schist than in altered volcanics. Although smectite is
distributed heterogeneously, smectite + illite ± chlorite
relatively increases outwards from and upward of the
kaolinite deposit. Locally, the presence of dolomite
associated with kaolinized tuffaceous units was detected.
Kaolinite in both volcanics and schists was identified
by diagnostic peaks at 7.13–7.20 and 3.57 Ǻ (Figure 5).
Smectite was determined by a peak at 15.06–14.33 Ǻ that
expanded to 17.15 Ǻ following ethylene-glycol solvation,
and collapsed to 9.75 Ǻ upon heating to 350 °C and 550
°C. Chlorite was identified by peaks at 14.00–14.38, 7.15
and 3.54 Ǻ, and illite by reflections at 10.0 and 5.0 Ǻ. These
peaks are not affected by ethylene-glycol treatment, and
undergo a slight reduction following heating to 550 °C,
due to dehydroxylation. Gypsum is characterised by peaks
at 7.59, 4.25 and 3.06 Ǻ, and talc by peaks at 9.37, 4.74 and
3.12 Ǻ.
4.3. SEM-TEM determinations

SEM images indicate that kaolinite predominates in
volcanic and schist samples, and coexists with feldspar
and muscovite in the Karaçayır kaolinite deposit (Figure

452

6). Volcanic kaolinites are hexagonal in form and arranged
either as compact irregular stacks or face-to-face in
elongate stacks and with diameters < 10 μm, rimming
altered feldspars, suggesting an authigenic mode of
formation (Figure 6a-c). Kaolinite in schists developed at
the edges of muscovites in characteristic irregular stacks
having diameters of 4-6 μm (Figure 6d).
Smectite rims fibrous illite in both schist and volcanic
samples, exhibiting spongy and filamentous textures
that developed authigenically (Figure 6e-h). Smectiteillite crystals are associated with altered feldspar. Locally,
acicular halloysite was identified in sample KC1-38 (Figure
6i).
Gypsum crystals occur in thick platy and blocky forms
within talc schist (Figure 6j). Rounded and radial fibrous
crystals developed on fracture surfaces, resembling pyrite
and goethite, respectively (Figure 6k,l)
TEM studies reveal that the Karaçayır kaolinites
occur in euhedral, hexagonal forms with regular outlines,
characteristic of well-crystallised kaolinite (Figure 7a,b).
4.4. 57Fe Mössbauer spectroscopy
Karaçayır kaolinite sample KC1-21 displays a symmetrical
doublet spectrum (IS, isomer shift) = 1.18 and (QS,
quadrupolar splitting) = 2.01 mm/s at 300 K, characteristic
of Fe+2 in the octahedral site (Ram et al. 1997; Paduani et

al. 2009) (Figure 8). The symmetrical doublet spectrum
(IS = 0.238 and QS = 0.652 mm/s) (300 K temperature) in
the Karaçayır smectite sample KC1-31 corresponds to Fe+3
in the octahedral site (Paduani et al. 2009). The Mössbauer
spectroscopic result from the Karaçayır kaolinite sample
is similar to that reported for clay minerals in subsurface
sediments of the Jaisalmer basin (India) (Ram et al.
1997). Hence, Fe+2 partially substitutes for Al+3 in the
octahedral site of kaolinite, whereas Fe+3 replaces Al+3 in
the octahedral site of montmorillonite, based on their
chemical compositions (Malden & Meads 1967; Petit &
Decarreau 1990; Silver et al. 1980; Castelein et al. 2002).
4.5. Whole-rock geochemistry
The results of representative chemical analyses of fresh
volcanic and schist host rocks and related altered rock
samples are given in Table 2. Fresh, partially altered, and
altered samples plot in the trachyandesite field and near
the join between the andesite and rhyodacite/dacite fields
on the Zr/TiO2 vs. Nb/Y diagram of Winchester & Floyd
(1977)(Figure 9).
Using gains and losses of mass (MacLean & Kranidiotis
1987), enrichments and depletions of the various major
and trace elements were discerned from fresh, to altered,
to highly altered samples (Table 3; Figure 10). Generally,
SiO2, NaO and K2O have been leached, and Al2O3, Fe2O3,
MgO and CaO enriched. Cs, V, Y are slightly enriched, and
Ba, Rb, Sr, Zr and ∑REE are depleted.
On the Zr vs. TiO2, Cr+Nb vs. Fe+Ti and Ba+Sr vs.
Ce+Y+La diagrams of Dill et al. (1997), plots of the

2

10

20

30
40
º2 CuK

50

60

2

KC1-57
powder

10

10
15

20
20

30
40

º2 CuK
25
30

50

1.48 qtz

13.14

3 . 5 9 kao

7 . 2 3 kao

3.36 qtz

1 0 . 1 5 il l

3 . 5 6 kao

4.74 tlc

7 . 1 3 kao

14.33 smc

3.12 tlc

9.37 tlc

3.59

7.23

17.45

1.54 qtz

1.81 qtz

2.45 qtz

3.57 kao

14.91 smc
9.97 ill
7.59 gyp
7.01 kao
4.97 ill
4.25 qtz+gyp

3.35

3.18

9.75

3.34 qtz

KC1-36

powder

1.66 qtz

5

3.34 qtz

3.57

7 . 1 3 kao

1.82 qtz

1.99 qtz

5 . 0 2 il l
4.28 qtz

7.15 kao

14.47 smc

2

3 . 0 3 c al
2.56
2.50
2.34

3.34 qtz

15.06 smc

KC1-7
powder

4.46
4.17 4.34

2.18 dol

3.24 fds
2.90 dol

4.25 qtz
3 . 5 8 kao

14.75 smc
1 0 . 0 1 il l
7 . 2 0 kao
6.45 fds

2.19 dol

3 . 0 1 c al

7.04 chl

2.88 dol

3.53 chl
3.34 qtz

4.70 chl

13.97 chl

KADİR and ERKOYUN / Turkish J Earth Sci

KC1-55
powder

heated to 550 °C

ethylene-glycol
solvated

KC1-37
powder

oriented
air-dried

35

kao

KC1-44
powder

kao

60

Figure 5. X-ray diffraction patterns for altered volcanic and schist samples. kao: kaolinite; smc:
smectite; ill: illite; chl: chlorite; tlc: talc; gyp: gypsum; qtz: quartz; fds: K-feldspar; dol: dolomite; cal:
calcite.

453


KADİR and ERKOYUN / Turkish J Earth Sci

a

b

5 um

5 um

c

5 um

smectite + illite

smectite

d

e

10 um

smectite

opal-CT

5 um

f

feldspar

halloysite

smectite + illite

g

5 um

5 um

h

5 um

i

1 um

goethite

Fe (oxyhydr)oxide phase

j

20 um

k

10 um

l

2 um

Figure 6. SEM images of: a. compact kaolinite plate (KC1-14); b. development of vermiform kaolinite plates rimming
altered volcanic material (KC2-10); c. book-like kaolinite plates (KC1-27); d. kaolinite plates and muscovite in schist
(KC1-33); e-f. cornflake-like smectite edging illite fibres that developed within a microfracture (KC1-38; KC1-34);
g. smectite and opal-CT in altered schist (KC1-28); h. smectite rimming illite and altered feldspar within altered tuff
(KC2-10); i. a close-up view of rod-like halloysite (KC1-38); j. a close-up view of gypsum (KC1-40); k. rounded Fe
(oxyhydr)oxide phases resembling pyrite (KC1-12); l. radial fibrous crystals resembling goethite developed on the
surface of a fracture (KC1-33).

454

KADİR and ERKOYUN / Turkish J Earth Sci

kaolinite

kaolinite

a

0.2 μm

b

100 nm

Figure 7. TEM image of a-b. hexagonal platy kaolinite crystals (KC2-1) of various sizes.

IS

KC1-21

22+
+
Fe
Fe
-10.0

QS

0

Velocity (mm/s)

by Weaver (1976). Relatively high SiO2 contents are a
consequence of widespread silicification in the deposit.
The Fe2O3 values (9.16% in sample KC1-59) are related to
Fe (oxyhydr)oxide phases, such as hematite and pyrite.
4.6. Oxygen- and hydrogen-isotope compositions of clay
minerals
The isotopic compositions of Karaçayır kaolinite (KC1-4,
KC1-28, EG1-9) and smectite (KC1-31, KC1-33) samples
are given in Table 4 and Figure 13. The δ18O and δD
values for the Karaçayır kaolinites range between +11.6‰
and +19.4‰, and -79‰ and -103‰, respectively, and
for smectite between 11.8‰ and 20.4‰ and -93‰ and
-112‰, respectively.
The isotopic values of kaolinite are situated to the left of
the supergene/hypogene line (except for sample KC1-33,
composed of kaolinite + smectite, which plots to the left of
the kaolinite line). The formation temperatures of the clay
minerals were calculated using their δ18O values, assuming
that parent fluids were end-member hydrothermal fluids
(1.5‰) (Campbell et al. 1988). The calculation yields 61.6–

Transmission (% )

Transmission (% )

Karaçayır volcanic and metamorphic kaolinite samples
appear to be comparable to the hypogene Lastarria
kaolinites of Peru (Figure 11).

The whole-rock REE contents of samples from both
the volcanics (average 105.69-134.60 ppm) and schists
(average 53.77-143.21 ppm) were normalised to chondrite
values (Boynton 1984) and are given in Figure 12. All
the fresh, partially altered and altered samples from the
volcanics and schists yield similar REE patterns (except
altered schist samples KC1-37, KC1-40, KC1-41 and KC155), displaying enrichment in LREE [La/Sm)cn = 2.66–5.11
and 0.24–3.66], [La/Lu)cn = 4.31–21.78 and 0.38–12.89]
relative to HREE [(Gd/Yb)cn= 0.98–2.85 and 0.54–3.06],
[(Tb/Yb)cn= 1.06–1.82 and 0.76–2.01], and variable
negative Eu anomalies (Eu/Eu* = 0.51–0.74 and 0.22–1.05).
Negative Ce/Ce* values characterise both the volcanic and
schist samples (0.89–1.12 and 0.62–1.09, respectively).
The ratio of SiO2/Al2O3 in the Karaçayır smectitebearing kaolinite and kaolinite-bearing smectite samples
(e.g., samples KC1-44 and KC1-49) is in the range of 2.32–
2.82, compatible with the values (1.85–2.94) reported

IS

KC1-31

QS
Fe

10.0

-9.0

3+

0
Velocity (mm/s)

9.0

Figure 8. 57Fe Mössbauer spectra for a Karaçayır kaolinite sample (KC1-21) and a smectite sample (KC1-31); IS: isomer shift,
QS: quadrupolar splitting.

455


KADİR and ERKOYUN / Turkish J Earth Sci
Table 2. Major- (wt.%) and trace-element (ppm) compositions of fresh, partially altered and highly altered volcanics and schists of the
study area (see Table 1 for the mineralogical compositions of the samples).
Fresh Volcanic Samples
%
SiO2
Al2O3
∑Fe2O3
MgO
CaO
Na2O
K2O
TiO2
P2O5
MnO
Cr2O3
LOI
Sum
ppm

Ba
Be
Co
Cs
Ga
Hf
Nb
Rb
Sn
Sr
Ta
Th
U
V
W
Zr
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb

Lu
Pb
Zn
Ni
Au (ppb)
Ag
Mo
Cu
As
Cd
Sb
∑REE
(Eu/Eu*)cn
(Ce/Ce)cn
(La/Sm)cn
(La/Yb)cn
(La/Lu)cn
(Eu/Sm)cn
(Gd/Yb)cn
(Tb/Yb)cn
(Tb/Lu)cn

KC1-2
87.58
3.27
3.91
0.35
0.32
0.04
0.41

0.20
0.026
0.02
0.154
3.5
99.78

KC2-2
73.14
13.45
1.14
0.92
1.42
0.15
3.80
0.08
0.041
0.11
0.002
5.7
99.95

KC2-6
69.52
12.21
0.91
0.26
4.78
0.32
5.84

0.08
0.034
0.05
0.006
5.9
99.91

KC2-14
72.60
13.42
1.30
1.23
1.61
0.16
3.50
0.08
0.030
0.07
0.002
5.9
99.90

KC5-2
64.14
14.10
4.49
1.57
3.01
2.87
6.10

0.94
0.54
0.12
0.020
1.8
99.70

average
73.39
11.29
2.35
0.86
2.22
0.70
3.93
0.27
0.13
0.07
0.03
4.56
99.80

171
<1
50.3
7.4
2.7
0.9
4.0
21.3

<1
106.5
0.3
2.8
1.5
46
0.6
29.2
4.5
6.7
13.0
1.59
6.0
1.00
0.22
0.81
0.13
0.71
0.16
0.45
0.08
0.47
0.08
17.5
45
918.4
0.7
<0.1
1.1
10.2

845.3
0.3
5.4
31.4
0.74
0.90
4.22
9.65
8.73
0.58
1.39
1.18
1.07

458
3
0.7
9.2
14.5
2.5
15.5
146.5
3
252.1
1.7
15.6
6.7
<8
2.7
59.4

19.2
27.0
51.1
5.53
18.9
3.39
0.63
2.87
0.56
3.09
0.61
1.8
0.29
1.97
0.28
31.2
13
17.6
4.3
<0.1
0.1
0.3
21.4
<0.1
0.2
118.02
0.61
0.92
5.01
9.26

10.02
0.49
1.18
1.21
1.31

583
3
1.4
8.5
12.1
2.2
13.6
208.9
2
68.4
1.4
14.5
8.7
<8
3.6
51.7
18.0
24.6
45.2
5.11
17.1
3.16
0.59
2.64

0.49
2.72
0.55
1.63
0.27
1.74
0.26
18.9
26
253.5
0.8
<0.1
0.4
0.9
15.1
0.3
0.7
106.06
0.62
0.89
4.90
9.56
9.82
0.49
1.22
1.20
1.23

310
4

0.8
9.6
14.2
2.4
15.8
151
3
87.7
1.7
14.3
7.5
<8
3.3
55.7
19.6
24.4
46.4
5.12
17.2
3.23
0.57
2.79
0.52
3.04
0.61
1.90
0.29
2.04
0.30
22.6

9
10.4
<0.5
<0.1
0.2
0.2
4.1
<0.1
0.2
108.41
0.58
0.92
4.75
8.08
8.44
0.46
1.1
1.09
1.13

1116
5
11.9
10.8
17.7
13.1
28.4
211.0
4
634.8

2.1
32.8
12.7
92
4.6
435.5
16.4
56.6
116.4
13.26
48.2
8.04
1.70
6.51
0.79
3.89
0.65
1.71
0.27
1.85
0.27
3.1
54
50.4
2.2
<0.1
1.8
29.6
2.8
0.1

0.7
260.14
0.72
0.96
4.43
20.70
21.78
0.56
2.85
1.82
1.92

527.6
3.2
13.02
9.1
12.24
4.22
15.46
147.74
2.6
229.9
1.44
16
7.42
32.4
2.96
126.3
15.54
27.86

54.42
6.12
21.48
3.76
0.74
3.12
0.49
2.69
0.51
1.49
0.24
1.61
0.23
18.6
29.4
250.06
2.7
<0.1
0.72
8.24
177.74
0.18
1.44
124.76
0.66
0.91
4.66
11.45
11.75
0.51

1.54
1.3
1.33

Eu/Eu*=EuN/√(SmN*GdN) and Ce/Ce*=3CeN/(2LaN+NdN) (Mongelli 1997), LOI: loss on ignition at 1050 °C.

456


KADİR and ERKOYUN / Turkish J Earth Sci
Table 2. (Continued).
Partially Altered Volcanic Samples
%
SiO2
Al2O3
∑Fe2O3
MgO
CaO
Na2O
K2O
TiO2
P2O5
MnO
Cr2O3
LOI
Sum
ppm
Ba
Be
Co

Cs
Ga
Hf
Nb
Rb
Sn
Sr
Ta
Th
U
V
W
Zr
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Pb
Zn

Ni
Au (ppb)
Ag
Mo
Cu
As
Cd
Sb
∑REE
(Eu/Eu*)cn
(Ce/Ce)cn
(La/Sm)cn
(La/Yb)cn
(La/Lu)cn
(Eu/Sm)cn
(Gd/Yb)cn
(Tb/Yb)cn
(Tb/Lu)cn

KC1-4
74.12
13.55
0.95
0.73
0.75
0.16
4.33
0.07
0.039
0.06

<0.002
5.0
99.76

KC1-5
62.00
6.00
2.58
4.68
8.29
0.08
0.93
0.54
0.110
0.04
0.040
14.2
99.49

KC1-12
61.00
9.19
7.36
5.03
3.48
0.11
2.13
0.43
0.062
0.03

0.119
11.1
100.04

KC2-3
70.25
12.74
2.12
0.54
3.30
0.18
4.22
0.08
0.036
0.25
<0.002
6.1
99.81

KC2-7
62.89
10.98
3.54
0.61
7.97
0.26
3.20
0.35
0.072
0.08

0.026
9.8
99.78

average
66.05
10.49
3.31
2.31
4.75
0.158
2.96
0.29
0.06
0.09
0.03
9.24
99.74

288
3
0.5
11.0
15.4
2.5
18.3
176.8
3
230.5
2.1

13.8
14.2
<8
3.3
50.0
21.0
19.9
38.5
4.19
14.1
2.85
0.51
2.66
0.55
3.28
0.65
2.01
0.33
2.16
0.31
45.6
19
7.0
<0.5
<0.1
0.1
0.2
5.1
<0.1
0.2

92.0
0.56
0.94
4.39
6.23
6.66
0.47
0.99
1.08
1.16

115
1
8.9
3.7
7.2
6.0
10.8
46.7
1
107.3
0.8
7.2
2.8
52
1.3
224.0
22.7
19.8
42.4

5.25
20.8
4.2
0.89
3.87
0.67
3.90
0.78
2.32
0.36
2.25
0.33
6.8
41
167.0
<0.5
<0.1
0.4
11.6
42.2
<0.1
0.5
107.82
0.67
0.96
2.96
5.94
6.22
0.56
1.39

1.27
1.33

752
2
17.4
27.9
11.1
2.3
7.7
150.4
2
133.5
0.5
6.1
1.4
70
0.8
78.0
30.6
16.2
40.5
4.35
17.6
3.83
1.00
4.52
0.90
5.26
1.07

3.00
0.45
2.76
0.39
19.3
19
380.5
<0.5
<0.1
<0.1
2.6
4.8
<0.1
1.9
101.83
0.73
1.12
2.66
3.96
4.31
0.69
1.32
1.39
1.51

1257
3
0.7
10.4
12.6

2.4
15.8
167
3
218.2
1.6
15.5
7.6
<8
3.3
57.3
20.2
26.1
50.0
5.37
17.9
3.21
0.56
2.71
0.53
3.21
0.65
1.88
0.33
2.11
0.32
17.8
22
19.3
0.8

<0.1
1.0
0.2
34.5
<0.1
0.2
114.88
0.58
0.93
5.11
8.36
8.47
0.46
1.04
1.07
1.08

577
2
13.2
11.4
12.9
3.4
13.7
138.3
2
95.4
1.2
11.2
16.3

51
2.2
109.8
20.0
23.5
46.2
5.4
20.3
3.81
0.73
3.29
0.57
3.23
0.64
1.89
0.29
1.99
0.29
56.4
64
589.1
0.8
<0.1
0.8
12.1
50.2
0.5
1.1
112.13
0.63

0.92
3.88
7.98
8.41
0.50
1.34
1.22
1.29

597.8
2.2
8.14
12.8
11.84
3.32
13.26
135.84
2.2
156.98
1.24
10.76
8.46
37.8
2.18
103.82
22.9
21.1
43.52
4.91
18.14

3.58
0.73
3.41
0.64
3.77
0.75
2.22
0.35
2.25
0.32
29.18
33
232.58
0.62
<0.1
0.48
5.34
27.36
0.18
0.78
105.69
0.63
0.97
3.8
6.49
6.81
0.53
1.21
1.20
1.27

457


KADİR and ERKOYUN / Turkish J Earth Sci
Table 2. (Continued).
Altered Volcanic Samples
%
SiO2
Al2O3
∑Fe2O3
MgO
CaO
Na2O
K2O
TiO2
P2O5
MnO
Cr2O3
LOI
Sum
ppm
Ba
Be
Co
Cs
Ga
Hf
Nb
Rb

Sn
Sr
Ta
Th
U
V
W
Zr
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Pb
Zn
Ni
Au (ppb)
Ag
Mo
Cu

As
Cd
Sb
∑REE
(Eu/Eu*)cn
(Ce/Ce)cn
(La/Sm)cn
(La/Yb)cn
(La/Lu)cn
(Eu/Sm)cn
(Gd/Yb)cn
(Tb/Yb)cn
(Tb/Lu)cn

458

Fresh Schist Samples

KC1-6
44.83
8.59
7.76
6.13
10.36
0.16
1.66
0.38
0.074
0.10
0.342

19.0
99.38

KC1-7
68.04
15.86
1.14
1.50
0.95
0.15
5.94
0.08
0.046
0.02
0.002
6.3
100.02

KC1-14
43.10
14.70
5.39
4.97
9.55
0.38
3.56
0.83
0.119
0.06
0.027

17.2
99.88

KC1-21
51.18
13.15
6.03
5.42
5.06
0.13
3.18
0.62
0.13
0.07
0.058
14.7
99.73

average
51.78
13.07
5.08
4.50
6.48
0.20
3.58
0.47
0.09
0.06
0.10

14.3
99.71

KC1-27
76.37
13.05
2.41
0.43
0.11
0.16
2.56
0.68
0.10
<0.01
0.009
4.0
99.89

KC1-33
62.15
16.72
8.93
0.81
0.33
0.26
4.59
0.95
0.13
0.04
0.014

4.8
99.72

KC1-39
83.49
8.49
1.70
0.72
0.22
0.21
2.06
0.59
<0.01
<0.01
0.013
2.4
99.91

KC1-48
71.03
14.56
2.06
1.03
1.74
0.17
4.28
0.88
0.16
0.06
0.016

3.9
99.88

KC1-56
72.80
11.87
3.76
0.82
1.7
1.2
1.67
0.63
0.14
0.15
0.013
5.1
99.85

KC2-17
47.34
15.77
8.53
3.73
11.76
4.79
0.30
1.86
0.21
0.10
0.032

5.4
99.82

average
68.86
13.41
4.56
1.25
2.64
1.13
2.66
0.93
0.12
0.06
0.01
4.26
99.84

246
1
89.1
16.2
10.7
2.3
8.6
83.1
2
240.6
0.6
7.1

3.5
84
1.3
76.3
14.7
17.7
35.9
4.34
17.0
3.08
0.64
2.73
0.48
2.68
0.50
1.45
0.24
1.46
0.22
10.1
41
1363
1.2
<0.1
1.0
21.4
74.2
0.1
1.8
88.42

0.67
1.05
3.62
8.20
8.35
0.55
1.51
1.40
1.43

265
1
7.9
5.8
15.1
2.7
21.0
254.4
3
141.9
2.5
14.0
9.2
<8
1.9
55.4
23.6
19.3
38.1
4.26

14.3
3.02
0.5
2.93
0.60
3.63
0.71
2.20
0.36
2.40
0.35
7.2
12
117.7
<0.5
<0.1
0.4
1.2
6.0
<0.1
0.7
92.66
0.51
0.95
4.02
5.43
5.72
0.43
0.98
1.06

1.12

529
3
20.8
25.9
18.0
5.7
17.9
164.3
3
304
1.3
13.4
8.2
113
1.8
201.4
28.7
37.5
77.8
9.48
36.3
6.90
1.45
5.86
0.97
5.18
1.01
2.81

0.44
2.69
0.39
16.3
89
189.7
0.9
<0.1
0.9
17.4
84.5
0.1
0.8
188.78
0.69
0.95
3.42
9.42
9.98
0.55
1.76
1.54
1.63

428
3
37.1
22.3
18.9
4.7

14.4
154.3
3
243.9
1.0
14.3
4.4
104
2.5
139.5
22.1
34.0
67.9
8.20
32.1
6.33
1.22
5.82
0.90
4.77
0.96
2.85
0.40
2.73
0.38
18.3
59
421
0.9
0.1

0.5
36.5
18.5
0.1
0.5
168.56
0.61
0.92
3.43
8.42
9.29
0.51
1.72
1.41
1.55

367
2
38.72
17.55
15.67
3.85
15.47
164.02
2.75
232.6
1.35
12.2
6.32
77.25

1.87
118.15
22.27
27.12
54.92
6.57
24.92
4.83
0.95
4.33
0.73
4.06
0.70
2.32
0.36
2.32
0.33
12.97
50.25
522.85
0.87
0.1
0.7
19.12
45.8
0.1
0.95
134.60
0.62
0.96

3.62
7.86
8.33
0.51
1.49
1.35
1.43

506
1
3.0
2.5
15.2
8.3
13.0
78.7
3
59.9
1.0
10.9
4.4
75
1.2
272
15.3
26.4
54.9
6.69
27.3
4.80

0.95
4.31
0.66
3.50
0.68
1.92
0.32
1.99
0.29
3.9
3
19.3
2.8
<0.1
1.0
74.3
66.9
<0.1
0.2
134.71
0.63
0.94
3.46
8.96
9.45
0.52
1.75
1.41
1.49

546
2
115.7
6.0
21.2
7.1
21.5
165.3
3
62.8
1.6
12.8
14.7
129
2.5
237.7
28.2
62.1
136.4
16.14
64.7
12.54
2.93
12.20
1.72
8.69
1.47
3.87
0.57
3.65

0.50
7.4
127
485.3
5.8
<0.1
2.3
41.7
86.7
0.4
0.4
327.48
0.72
0.99
3.11
11.50
12.89
0.62
2.70
2.01
2.25

393
<1
2.2
1.7
10.2
11.7
11.9
57.2

2
49.0
0.8
3.5
1.2
50
1.0
412.5
12.4
15.6
33.0
3.92
14.4
2.85
0.55
2.68
0.43
2.60
0.49
1.52
0.24
1.68
0.27
2.5
3
30.6
<0.5
<0.1
1.1
2.3

<0.5
<0.1
<0.1
80.23
0.60
0.98
3.44
6.27
6.00
0.51
1.29
1.09
1.04

631
2
2.2
2.5
20.2
7.6
15.8
140.1
3
50.1
1.3
9.9
1.9
135
1.6
274.8

14.9
23.2
47.5
5.46
21.2
3.54
0.51
3.01
0.45
2.32
0.51
1.56
0.28
1.9
0.33
0.8
8
27.1
8.8
<0.1
1.5
203.9
32.9
<0.1
0.1
111.77
0.47
0.95
3.04
8.25

7.29
0.38
1.28
1.01
0.89

386
2
10.3
1.7
12.5
8.4
10.1
49.9
1
55.3
0.7
8.3
2.7
79
1.1
315.1
25.8
19.5
45.9
5.31
20.9
3.94
0.95
3.80

0.67
4.00
0.89
2.66
0.42
2.90
0.44
9.1
27
44.5
1.2
<0.1
1.7
21.3
8.3
0.1
0.3
112.28
0.75
1.06
3.11
4.54
4.60
0.63
1.06
0.98
1.00

15
<1

20.8
0.4
18.5
3.2
3.9
6.7
1
380.1
0.3
0.4
3.3
258
<0.5
114.5
41.6
9.2
21.9
3.57
18.5
5.77
2.30
7.76
1.46
9.05
1.87
5.27
0.74
4.73
0.68
1.2

14
38.8
<0.5
<0.1
1.1
4.1
2.3
<0.1
<0.1
92.8
1.05
0.90
1.00
1.31
1.40
1.05
1.32
1.31
1.41

412.83
1.5
25.7
2.46
16.3
7.71
12.7
82.98
2.16
109.53

0.95
7.63
4.7
121
1.31
271.1
23.03
26
56.6
6.84
27.83
5.57
1.36
5.62
0.89
5.02
0.98
2.8
0.42
2.80
0.41
4.15
30.3
107.6
3.26
<0.1
1.45
57.93
32.93
0.15

0.2
143.21
0.70
0.97
2.86
6.8
6.93
0.61
1.56
1.30
1.34


KADİR and ERKOYUN / Turkish J Earth Sci
Table 2. (Continued).
Altered Schist Samples
%
SiO2
Al2O3
∑Fe2O3
MgO
CaO
Na2O
K2O
TiO2
P2O5
MnO
Cr2O3
LOI
Sum

ppm
Ba
Be
Co
Cs
Ga
Hf
Nb
Rb
Sn
Sr
Ta
Th
U
V
W
Zr
Y
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm

Yb
Lu
Pb
Zn
Ni
Au (ppb)
Ag
Mo
Cu
As
Cd
Sb
∑REE
(Eu/Eu *)cn
(Ce/Ce)cn
(La/Sm)cn
(La/Yb)cn
(La/Lu)cn
(Eu/Sm)cn
(Gd/Yb)cn
(Tb/Yb)cn
(Tb/Lu)cn

KC1-28
60.35
19.79
1.66
0.75
0.50
0.18

0.24
2.51
0.02
<0.01
0.045
13.9
99.95

KC1-34
49.96
16.07
4.73
5.58
5.52
6.66
0.44
0.64
0.34
0.06
0.067
9.7
99.77

KC1-37
45.45
3.59
7.62
22.28
7.10
0.07

<0.01
0.11
0.02
0.12
0.358
12.7
99.43

KC1-40
54.05
0.13
9.07
7.76
12.28
<0.01
0.03
<0.01
0.01
0.32
0.003
16.2
99.87

KC1-41
64.77
13.63
2.72
1.20
3.61
2.18

0.36
0.90
0.08
0.12
0.012
10.3
99.88

KC1-44
53.03
22.83
2.12
1.29
0.97
0.11
0.08
2.69
0.03
<0.01
0.036
16.7
99.89

KC1-49
57.68
20.45
0.93
1.09
5.49
0.07

0.55
1.07
0.22
<0.01
0.017
12.3
99.88

KC1-52
39.08
8.87
1.44
9.28
14.67
0.09
2.29
0.47
0.12
0.12
0.018
23.3
99.75

KC1-55
35.77
3.90
4.52
12.41
16.63
<0.01

<0.01
0.15
0.01
0.25
0.252
25.8
99.71

KC1-59
41.65
12.78
9.16
2.67
1.31
0.15
3.12
0.53
0.1
0.04
0.067
28.1
99.68

average
50.17
12.20
4.39
6.43
6.80
1.05

0.71
0.90
0.15
0.10
0.08
16.9
99.88

55
1
1.4
3.5
20.7
5.6
6.5
8.4
2
16.7
0.5
0.4
0.5
333
1.3
181.3
10.8
1.2
3.2
0.46
2.0
0.74

0.29
1.23
0.33
2.46
0.55
1.72
0.27
1.84
0.32
4.0
7
10.5
0.8
<0.1
0.2
3.3
2.5
<0.1
<0.1
16.61
0.92
1.07
1.01
0.43
0.38
1.03
0.54
0.76
0.67

26
<1
20.8
1.5
16.3
2.0
3.7
23.5
<1
202.6
0.3
0.5
0.5
31
0.8
64.9
29.5
14.8
40.3
6.05
27.8
6.73
1.91
7.30
1.26
6.97
1.38
3.72
0.54
3.41

0.50
1.5
21
233
<0.5
<0.1
0.6
1.0
1.8
<0.1
<0.1
122.67
0.83
1.05
1.38
2.93
3.07
0.75
1.73
1.57
1.65

4
<1
85.1
0.4
4.2
0.5
1.1
0.7

<1
19.4
<0.1
<0.2
0.2
70
<0.5
21.9
3.7
6.2
16.8
2.36
10.3
1.89
0.12
1.40
0.17
0.83
0.15
0.41
0.06
0.37
0.05
0.7
22
546.6
<0.5
<0.1
0.2
8.7

1.7
<0.1
<0.1
41.11
0.22
1.09
2.06
11.33
12.89
0.16
3.06
1.96
0.34

8
<1
17.8
0.4
0.8
<0.1
0.3
1.1
<1
65.3
<0.1
0.4
2.5
<8
<0.5
1.5

11.6
1.4
2.4
0.32
1.5
0.55
0.22
1.12
0.23
1.53
0.38
1.16
0.15
1.02
0.15
4.1
15
88.3
2.0
<0.1
5.4
84.3
54.6
0.3
0.2
12.13
0.85
0.77
1.60
0.92

0.96
1.05
0.89
0.96
1.00

20
<1
12.8
0.5
13.6
11.7
25
12.1
2
29.6
2.1
4.0
2.4
43
6.2
441.9
14.7
6.6
11.9
1.82
8.1
1.57
0.46
2.28

0.40
2.45
0.54
1.64
0.26
1.72
0.29
2.0
19
54.1
1.7
<0.1
1.2
109.1
19.0
<0.1
<0.1
40.63
0.74
0.78
0.24
2.59
2.36
0.77
1.07
0.99
0.90

8
<1

1.4
1.2
29.7
4.7
6.2
3.5
2
12.4
0.4
0.3
0.9
423
<0.5
180.3
4.5
0.8
1.5
0.21
0.9
0.27
0.1
0.39
0.1
0.7
0.17
0.58
0.11
0.92
0.18
4

1
1.6
5.2
<0.1
<0.1
0.2
1.0
<0.1
<0.1
6.93
0.94
0.83
1.87
0.58
0.45
0.98
0.79
1.95
0.36

20
<1
11.5
0.8
16.1
9.5
26.6
20.4
1
38.2

1.8
9.2
3.5
84
3.2
348.7
11
11.1
22.4
2.74
11.0
1.91
0.35
1.76
0.28
1.57
0.33
1.09
0.19
1.32
0.23
3.4
3
27.1
33
<0.1
1.3
55.5
41.7
<0.1

0.1
56.27
0.58
0.92
3.66
5.68
5.01
0.48
1.08
0.90
0.79

168
<1
7.6
4.5
10.3
3.0
8.4
78.1
1
104.9
0.6
6.4
3.5
107
1.0
107.1
12.7
15.7

29.9
3.62
14.6
2.86
0.68
2.76
0.43
2.38
0.46
1.27
0.21
1.37
0.21
7.2
16
44.2
5.0
<0.1
1.0
36.9
5.9
0.2
0.2
76.45
0.73
0.88
3.45
7.74
7.76
0.63

1.63
1.34
1.34

7
<1
26.3
0.1
6.1
0.8
0.8
0.4
<1
321.3
<0.1
<0.2
<0.1
37
<0.5
33.2
11.5
0.6
1.1
0.23
1.6
0.75
0.24
1.28
0.28
1.81

0.4
1.17
0.17
1.07
0.16
1.8
12
197.7
2.4
<0.1
0.2
0.1
1.1
<0.1
<0.1
9.69
0.74
0.62
0.50
0.37
0.38
0.84
0.96
1.11
1.15

265
2
56.5
51.7

16.7
3.0
9.7
182.4
3
370.6
0.7
11.7
21.8
129
1.9
100.5
25.2
31.2
63.7
7.35
30.3
5.51
1.12
4.84
0.79
4.33
0.84
2.37
0.37
2.2
0.34
60.6
79
853.7

<0.5
0.2
12.6
71.6
276.3
0.3
12.4
155.26
0.66
0.93
3.56
9.58
9.53
0.54
1.78
1.53
1.52

58.1
1
24.12
6.46
13.45
4.09
8.83
33.06
1.5
118.1
0.67
3.33

3.59
126.5
1.64
148.13
13.52
8.96
19.32
2.51
8.81
2.27
0.54
2.43
0.42
2.50
0.52
1.51
0.23
1.52
0.24
8.93
19.5
205.68
5.16
0.1
2.28
37.07
40.56
0.1
1.35
53.77

0.72
0.89
1.93
4.21
4.27
0.72
1.35
1.30
0.97

459


KADİR and ERKOYUN / Turkish J Earth Sci
5

Zr / TiO2

1

fresh volcanic samples
partially altered volcanic samples
highly altered volcanic samples
Com/Pant
Rhyolite

0.1

Trachyte

Rhyodacite/Dacite
TrachyAnd

Andesite

0.01

Phonolite

Bsn/Nph

Andesite/Basalt

Alk-Bas

SubAlkaline Basalt

0.001
0.01

0.1

Nb / Y

1

10

Figure 9. Geochemical discrimination of the Karaçayır kaolinite
deposits and volcanic rock samples from the vicinity using the

Nb/Y- Zr/TiO2 immobile-element diagram of Winchester &
Floyd (1977).

131.7 °C as the formation temperatures of kaolinite using
the isotopic fractionation factor (α) between kaolinite and
water, expressed by 1000 ln α = 2.76*106/T2-6.75 (Sheppard
& Gilg 1996). Based on δ18O values, the formation
temperatures for smectite, using the isotopic-fractionation
factor (α) between smectite and water (expressed by 1000
ln α = 2.58* 106/T2 -4.19), were 61.2–148.9 °C (Yeh 1974;
Yeh & Savin 1977; Savin & Lee 1988).
4.7. Sulphur isotopes
The δ34S value for pyrite (-3.4‰) is lower than for
chalcopyrite (-0.2‰) in the Karaçayır kaolinite deposit
(Table 5). The low δ34S values were derived either directly
from magmatic fluids or via dissolution and leaching of
pre-existing sulphide-bearing igneous sources (Ohmoto &
Rye 1979). On the other hand, the slight negative S isotope
values of kaolinite suggests that sulphide and sulphate
samples (-0.8‰) were closer to the source of mineralization
(Campbell & Lueth 2008), and fall within the range (0±3‰)
for post-magmatic sulphide values (Ohmoto & Rye 1979).
Hypogene mineralisation is characterised by the entry of
sulphides (pyrite, chalcopyrite) and sulphates (gypsum).
Pyrite-chalcopyrite pairs yield isotope equilibrium
temperatures of 80–125 °C (Table 5).
5. Discussion
The Karaçayır kaolinite deposit developed as a result
of hydrothermal alteration processes within Miocene
volcanics (rhyolite, andesite) and Palaeozoic mica schist,

glaucophane schist, talc schist, calcareous schist and
chlorite schist, controlled by a NE-SW-oriented normal
fault and fractures under the influence of a post-Late
Oligocene regional extensional tectonic regime (Seyitoğlu
& Scott 1991, 1992; Seyitoğlu et al. 2009; Karaoğlu et

460

al. 2010) and related geothermal activity (the Emirfakı
thermal water is located just 21 km SW of the deposit,
outside the study area). Prevalent kaolinite is associated
with quartz, smectite, illite and opal-CT in the centre of the
deposit, with relative increases of smectite, illite, chlorite
and Fe (oxyhydr)oxide phases outward and upward, and
the development of a silica cap on kaolinized volcanics and
schists strongly suggests hydrothermal activity. The release
of silica during alteration and silicification processes
operating within the rhyolitic tuffs and schists resulted in
the precipitation of a silica cap (quartz) at very high fluid/
rock ratios (e.g., Heinrich 1990; Tagirov & Schott 2001).
The distribution of silicified zones and associated Fe
(oxyhydr)oxides was controlled by fissures and fractures
above the Karaçayır kaolinite deposit within both volcanics
and schists, and was also associated with kaolinite phases.
Rapid decay of the thermal gradient along the flow path
reduces the precipitation capacity of the system, resulting
in decreasing silica precipitation (Ondrak & Möller 1999).
The circulation of silica-rich geothermal fluid along the
flow path favoured rapid precipitation of silica in the
kaolinite deposit. Reddish-brown colouring in the silica

cap is due to the presence of Fe (oxyhydr)oxide phases,
such as goethite and hematite, as determined by reflectedlight microscopy, SEM and Mössbauer spectroscopic
methods.
Textural images show that plagioclase and sanidine
are kaolinized, muscovite, chlorite and talc are argillized,
hornblende and biotite are opacitized, and that Fe
(oxyhydr)oxide phases and silica developed within
volcanics and schists. Micromorphologically, the
development of kaolinite, either as compact irregular
stacks or with vermiform morphology, at the edges of
altered feldspar, glass shards and muscovite suggests in
situ precipitation of kaolinite as a result of a dissolutionprecipitation mechanism (Bobos & Gomes 1998, Chen
et al. 2001, Kadir & Akbulut 2009). Also, the coexistence
of illite with smectite, the development of illite fibres on
smectite flakes, and the association of muscovite with
illite and kaolinite may suggest conversion of smectite to
illite via a dissolution-precipitation mechanism controlled
by Al/Si ratios and K during alteration of schists under
low-grade metamorphic conditions (Eberl 1993; Rask
et al. 1997; Bobos & Gomes 1998). Thus, illitization is
more widespread in the schists than in the volcanics, and
is related to alteration of K-bearing phases (K-feldspar,
muscovite, biotite) resulting in mass loss of Sr and Ba
(Ehrenberg 1991; Hillier et al. 1995; Leikine et al. 1996;
Lanson et al. 1998; Meunier & Velde 2004).
The leaching of SiO2, Na2O and K2O, the enrichment of
Al2O3, Fe2O3, MgO and CaO and LREE relative to HREE,
and negative Eu anomalies in both the volcanics and the
schists may be attributed to the alteration of K-feldspar and

KADİR and ERKOYUN / Turkish J Earth Sci
Table 3. Mass gains and losses for the Karaçayır area samples (compositional values for the oxides are in wt.% and other elements in
ppm, and mass changes for them are in g/100g rock and in ppm/100g rock, respectively).
Partially Altered Volcanic
Samples n=5
RC
SiO2

ΔCi

Altered Volcanic
Samples n=4
RC

Altered Metamorphic
Samples n=10

ΔCi

RC

ΔCi

71.08

-2.30

44.72

-28.66

46.42

-22.43

Al2O3

11.29

0

11.29

0

11.29

0

3.56

1.21

4.38

2.03

4.06

-0.49

MgO

2.48

1.62

3.88

3.02

5.95

4.7

CaO

5.11

2.89

5.59

3.37

6.29

3.65

Na2O

0.17

-0.52

0.17

-0.52

0.97

-0.15

K2O

3.18

-0.74

0.27

-3.65

0.65

-2.0

0.31

0.04

0.4

0.13

0.83

-0.09

P2O5

0.06

-0.06

0.07

-0.05

0.13

0.01

∑Fe2O3

TiO2
Sum

97.24

2.14

70.77

-24.33

76.59

-16.8

Ba

643.39

115.79

317.01

-210.58

53.76

-359.06

Co

8.76

-4.25

2.96

-10.05

22.32

-3.37

Cs

13.77

4.67

15.15

6.05

5.97

3.51

Ga

12.74

0.5

13.53

1.29

12.44

-3.85

Hf

3.57

-0.62

3.32

-0.89

3.78

-3.92

Nb

16.63

1.17

13.36

-2.09

8.17

-4.52
-52.38

Rb

146.19

-1.54

141.68

-6.05

30.59

Sr

168.95

-60.94

200.92

-28.97

109.29

-0.24

Ta

1.33

-0.1

1.16

-0.27

0.62

-0.32

Th

11.58

-4.41

10.53

-5.46

3.08

-4.54

U

9.1

1.68

5.45

-1.96

3.32

-1.37

V

40.68

8.28

66.72

34.32

117.06

-3.93

W

0.2

-2.75

1.61

-1.34

1.51

0.2

Zr

111.73

-14.56

102.05

-24.24

137.08

-134.01

Y

24.64

9.1

19.23

3.69

12.51

-10.51

La

22.7

-5.15

23.42

-4.43

8.29

-17.7

Ce

46.83

-7.58

47.44

-6.97

17.87

-38.72

Pr

5.28

-0.83

5.67

-0.44

2.32

-4.51
-19.67

Nd

19.52

-1.95

21.52

0.04

8.15

Sm

3.85

0.09

4.17

0.41

2.1

-3.46

Eu

0.78

0.04

0.82

0.08

0.49

-0.86

Gd

3.67

0.55

3.74

0.62

2.24

-3.37

Tb

0.68

0.19

0.63

0.14

0.38

-0.5

Dy

4.05

1.36

3.5

0.81

2.31

-2.7

Ho

0.8

0.29

0.6

0.09

0.48

-0.49

Er

2.38

0.89

2.0

0.51

1.39

-1.4

Tm

0.37

0.13

0.31

0.07

0.21

-0.2

Yb

2.42

0.81

2.0

0.51

1.4

-1.39

Lu

0.34

0.11

0.28

0.05

0.22

-0.18

Total REE

113.67

-10.52

116.1

-8.51

50.09

-95.15

n: number of samples, RC: reconstructed compositions, ΔC i: net mass changes.

461


100
50
0
-50
Ba
Co
Cs
Ga
Hf
Nb
Rb
Sr
Ta
Th
U
V

W
Zr
Y
REE

-100

P2O5

TiO2

K 2O

NaO

Ca O

Mg O

Fe2O3

ne t m a s s c ha ng e

150

A l2O3

4
3
2

1
0
-1
-2
-3

S iO2

ne t m a s s c ha ng e

KADİR and ERKOYUN / Turkish J Earth Sci

partially altered volcanic samples

5
0
-5
-10
-15
-20
-25
-30
-35

ne t m a s s c ha ng e

-100

ne t m a s s c ha ng e

50
0
-50
-100
-150
-200
-250
-300
-350
-400

-150
-200
-250

Ba
Co
Cs
Ga
Hf
Nb
Rb
Sr
Ta
Th
U
V
W
Zr
Y

REE

P2O5

TiO2

K 2O

NaO

Ca O

Mg O

Fe2O3

0
-50

altered volcanic samples

altered schist samples

Ba
Co
Cs
Ga
Hf
Nb
Rb

Sr
Ta
Th
U
V
W
Zr
Y
REE

P2O5

TiO2

K 2O

NaO

Ca O

Mg O

Fe2O3

A l2O3

altered volcanic samples

10
5

0
-5
-10
-15
-20
-25
S iO2

ne t m a s s c ha ng e

A l2O3

50

S iO2

ne t m a s s c ha ng e

partially altered volcanic samples

altered schist samples

Figure 10. Mass changes of major elements (in grams) and trace elements (in ppm) within the study area.

plagioclase, muscovite + biotite, hornblende and glasses in
fresh host-rock (volcanic and schist) samples, trending
toward an advanced argillic alteration system (Meyer &
Hemley 1967; Inoue 1995; Dill et al. 1997). Hydrothermal
fluid(s) flushing through fault and fracture zones resulted
in an increase in Al2O3/SiO2 ratios, favouring precipitation

of kaolinite under acidic conditions (Meunier 1995;
Kadir & Karakaş 2002; Felhi et al. 2008). In contrast, the
concentration of alkaline elements and Al2O3+Fe2O3+MgO
resulted in an alkaline condition suitable for the
precipitation of smectite (Weaver 1989; Chamley 1989;
Christidis et al. 1995; Kadir et al. 2011).
The negative Eu and Ce anomalies suggest alteration of
feldspar at high temperature, with release of Eu+2 during
diminishing hydrothermal alteration (Lackschewitz et al.
2000). The La/Lu ratio>1 (except KC1-28 and KC1-55)
implies that kaolinization occurred in low pH waters with
low concentrations of hydroxyl or carbonate species and

462

halogens (Bau 1991; Bau & Möller 1992). Furthermore,
excess local REE depletion in altered schist samples
(e.g., KC1-37, KC1-40 and KC1-55) possibly was related
to leaching of K and Zr during hydrothermal processes
(Honty et al. 2008).
High Ba, Sr and Zr, and low Cr, Nb, Ti, Ce, Y and
La values in the Karaçayır kaolinite deposit suggest a
hypogene origin, similar to the Lohreim kaolinite deposit
(Dill et al. 1995), and to hydrothermal clay minerals in
the Escanaba Trough, in the north-eastern Pacific Ocean
(Lackschewitz et al. 2000).
The low δ18O values for the Karaçayır kaolinite also
suggest a hypogene origin, as compared to kaolinites
from the El Salvador porphyry copper deposit, Chile
(Sheppard & Gustafson 1976) and the Andacollo Pb-Zn

deposit, Neuquén (Domínguez 1990). The low δD values
for kaolinite may reflect deuterium depletion of residual
fluids during magmatic degassing with subsequent


KADİR and ERKOYUN / Turkish J Earth Sci
1000

10

Zr (ppm)

Fe+Ti (%)

100
1

10
Peru hypogene kaolinites
Karaçayır volcanic kaolinites
Karaçayır metamorphic kaolinites

1
0.01

Ba+Sr (ppm)

1000

0.1

TiO2

1

0.1
10

10

100

1000
Cr+Nb (ppm)

10000

100

10
10

100
1000
Ce +Y+ La (ppm)

1000

Figure 11. Genetic analysis of Karaçayır area samples using the Zr vs. TiO2, Cr+Nb vs. Fe+Ti and Ba+Sr vs. Ce+Y+La
diagrams of Dill et al. (1997).

meteoric water mixing (Taylor 1992, Hedenquist et al.
1998), and hydrogen exchange with meteoric water
without the accompanying oxygen-isotopic exchange
typical of phyllosilicates (O’Neil & Kharaka 1976).
The δ18O and δD isotopic compositions and formation
temperatures (61.6–131.7 °C) from kaolinite reflect
formation under epithermal-water-derived conditions.
Crystallisation of gypsum, pyrite and lesser amounts
of chalcopyrite in the schists reflects hydrothermal
alteration. Pyrite and chalcopyrite formed during the
latter stages of hydrothermal activity along a NE-SWoriented tectonic zone that developed within the deposit.
Isotope equilibrium temperatures ranged from 80 °C to
125 °C, suggesting an epithermal alteration process. The
negative δ34S value for pyrite suggests that local meteoric

water partially mixed with geothermal fluids during
the last stages of hydrothermal activity (Ece et al. 2008;
Szynkiewicz et al. 2009). In addition, negative δ34S values
indicate that the sulphate/sulphide ratio decreased at low
partial pressures (fugacity) of oxygen with the escape of
sulphur-bearing gases from the melt and consequent
depletion in δ34S values (Sakai et al. 1982). The low isotopic
values of gypsum near the top of the deposit may suggest
that gypsum formed rapidly relative to the alteration
of the pyrite-bearing host rocks and recent oxidation
(Cunningham et al. 2005). Gypsum formed as a result of
the oxidation of pyrite and chalcopyrite under sulphideand sulphate-reducing conditions (Cunningham et al.
2005; Kämpf et al. 2000).

463


KADİR and ERKOYUN / Turkish J Earth Sci
300

200
fresh volcanic samples

100

partially altered volcanic samples

S ample/Chondrite

S ample/Chondrite

highly altered volcanic samples

10

2

fresh schist samples

100

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

highly altered schist samples

10

1

La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Figure 12. Chondrite-normalised REE patterns (Boynton 1984) for kaolinite and related volcanics of the Karaçayır area.

6. Conclusions
1. Geological features and analysis of the Karaçayır
kaolinite reveal that alteration of feldspar and glass shards
in rhyolite, and muscovite and feldspar in muscovite schist,
glaucophane schist, talc schist and chlorite schist was
effected by tectonically controlled hydrothermal fluids.
The alteration process resulted in zonation, such that
prevalent kaolinite is associated with quartz + smectite +
illite + opal-CT in the centre of the deposit, with relative
increases of smectite + illite + chlorite + Fe (oxyhydr)oxide
phases outward and upward.
Ocean-Crust
PoreWater

-80

s

Ocean
Water

MetamorphicH 2O

Primary
MagmaticH2O

A

Sediments

eat

her

ing

)

Meteoric/Hydrothermal

te L

Organic
Waters

Ka
oli
ni

B

S/H

-120

ine

(w

δD (0 00)

Me

teo

ric

-40

ter

CanadianShield
brines

Sea-Water/Hydrothermal

Wa

0

-160

-20

-10

10
0
0
18
δ O ( 00)

20

30

Figure 13. δD versus δ18O plot showing isotopic compositions
of kaolinite (KC1-4; KC1-28; EG1-9) and smectite (KC1-31;
KC1-33) from the Karaçayır kaolinite deposit (Sheppard 1986).
The line for kaolinite weathering is from Savin & Epstein (1970),
and the line for supergene/hypogene alteration (S/H) is from
Sheppard et al. (1969) ▲: kaolinite, ■: smectite.

464

2. Development of an Fe (oxyhydr)oxide-rich silica
cap in the upper part of the deposit and the occurrence
of iron- and iron-sulphide phases (such as goethite,
hematite, pyrite and chalcopyrite) as microfracturefillings, and sulphates (gypsum) support the supposition
that hydrothermal alteration was occurring.
3. Micromorphologically, the development of
authigenic book-like and vermiform kaolinite edging

feldspar and glass shards in volcanics, and muscovite and
feldspar in schists, suggests a dissolution-precipitation
mechanism.
4. Relative depletion of SiO2, Na2O and K2O and
enrichment in Al2O3, Fe2O3, MgO and CaO reveal that
alteration of both the volcanics and schists resulted in the
precipitation of kaolinite, kaolinite + illite and smectite.
Depletion of both total REE and HREE in the altered
volcanics and schists relative to their host rocks and, in
contrast, enrichment of LREE and negative Eu anomalies,
reveal fractionation of feldspar and hornblende during
hydrothermal alteration processes. The negative Ce/Ce*
values in both volcanic rock and schist samples are related
to fractionation of zircon.

5. High Ba, Sr and Zr, and low Cr, Nb, Ti, Ce, Y and
La values in the Karaçayır kaolinite deposit are consistent
with a hypogene origin.
6. δ18O and δD isotopic data from the Karaçayır
kaolinite and smectite reveal that alteration occurred via
a low temperature (perhaps 61.6–131.7 and 61.2–148.9
°C, respectively) hydrothermal process; thus, smectite
developed at a relatively lower temperature nearer the
margins of the kaolinite deposit. The negative δ34S values
for pyrite, chalcopyrite and gypsum reflect formation under
the influence of hydrothermal activity; this assumption is
supported by isotope equilibrium temperatures of 80–125
°C, as calculated from pyrite-chalcopyrite pairs.

KADİR and ERKOYUN / Turkish J Earth Sci
Table 4. Oxygen- and hydrogen-isotopic compositions of clay minerals from the Karaçayır kaolinite deposit, with calculated temperatures
(see Table 1 for the rock types of the samples).
Sample

Mineral

Yield
(%)

δ18O V-SMOV (‰)

KC1-4

kaolinite

14.2

11.6

KC1-28

kaolinite

14.9

19.4

EG1-9

kaolinite

14.2

18.8

KC1-31

smectite

14.1

20.4

KC1-33

smectite

13.9

11.8

11.9

Wt. % H2O

δD V-SMOV(‰)

Formation Temp.*(°C)

4.3

-79

131.7

11.3

-103

61.6

9.0

-95

65.7

12.6

-93

61.2

-112

148.9

* Formation temperatures were calculated as above, but assuming δ18Owater = 1.5‰.
Table 5. Sulphur-isotopic compositions of pyrite, chalcopyrite and gypsum, with calculated temperatures.

Sample

Mineral

δ34S (‰)

KC1-37

pyrite

-3.4

KC1-37

chalcopyrite

-0.2

KC1-40

gypsum

-0.8

KC1-37

pyrite-chalcopyrite

Acknowledgements
This study was supported financially by the Scientific

Research Projects Fund of Eskişehir Osmangazi University
in the framework of Project 200715009. The authors are

T (°C)

± 80-125

indebted to the anonymous reviewers and the editors
for their extremely careful and constructive reviews,
comments and suggestions which significantly improved
the quality of the paper.

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