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http://journals.tubitak.gov.tr/earth/

Turkish Journal of Earth Sciences Turkish J Earth Sci(2015) 24: 607-626© TÜBİTAKdoi:10.3906/yer-1504-27

Geochemistry of travertine deposits in the Eastern Anatolia District: an example of the Karakoçan-Yoğunağaç (Elazığ) and Mazgirt-Dedebağ (Tunceli) travertines, Turkey

Leyla KALENDER1,*, Özlem ÖZTEKİN OKAN1, Murat İNCEÖZ1, Bahattin ÇETİNDAĞ1, Vesile YILDIRIM21Department of Geological Engineering, Faculty of Engineering, Fırat University, Elazığ, Turkey

2Department of Biology, Faculty of Sciences and Letters, Fırat University, Elazığ, Turkey

* Correspondence: leylakalender@firat.edu.tr

1. IntroductionTravertine deposits located 24 km northwest of Karakoçan (Elazığ) and 60 km southwest of Mazgirt (Tunceli) (Figures 1a and 1b) are on the Karakoçan Fault Zone (KFZ) and Pamuklu Fault Zone (PFZ) and segments of the faults. The terms ‘travertine’ and ‘carbonate tufa’ are often used indiscriminately. ‘Travertine’ is frequently used to refer to carbonate rocks formed from thermal water deposits on the earth’s surface, forming various deposit morphologies such as cascades, apron and channel travertines, fissure ridges, plateaus, and towers (Pedley, 2009; Pedley and Rogerson, 2010; Fouke, 2011). According to Andrews (2006) and Capezzuoli et al. (2014), tufas are terrestrial carbonates that form under surficial open-air conditions in streams, rivers, and lakes. Tufa is a product of physicochemical and microbiological biomediation processes. Because tufas form under exposure to light, they contain microbial (bacterial and cyanobacterial) and sometimes other algal components; many tufas encrust higher plants that live on the margins of streams, waterfalls, and wetlands (Pentecost et al., 1997). Tufa carbonates precipitate at ambient

temperature from the calcium-bicarbonate waters derived from the dissolution of carbonate bedrock. Travertines are freshwater carbonates precipitated by organic or inorganic processes from the resources of calcium- and bicarbonate-rich underground waters (Guo and Riding, 1998). Rapid travertine precipitation initiates when the CO2 gas within the outcropping waters is emitted to the atmosphere. These freshwater carbonates have an internal structure that frequently changes laterally and vertically. Many conditions, such as differences in the lateral and vertical facies, the position of the resource, the base topography, fluctuations in the amount of the waters storing travertine, and changes in the flow rate and direction of water, organic activities, and surface waters, are frequently encountered in travertine fields due to seasonal climatic factors and tectonic zones. Topography plays a determinative role in the development of facies and in the storing of travertines. The climatic  changes’ influence on algal growth and travertine precipitation, besides tectonic settings, may produce a significant  effect on depositional geometry of the hydrothermal travertine formation. These conditions

Abstract: The Karakoçan-Yoğunağaç (Elazığ) and Mazgirt-Dedebağ (Tunceli) travertines, which are related to thermal springs, are situated on the right-lateral strike-slip Karakoçan Fault Zone (KFZ) and left-lateral strike-slip Pamuklu Fault Zone (PFZ) in eastern Anatolia. The surface area of the travertines varies from m2 to km2. Morphologically, the travertines are classified as ridge, banded, and terrace types due to deposition in different ways, in the releasing/restraining bends of the KFZ and PFZ and on the segments of faults. The banded travertines were dated by U-series, and an age of 160,000 ± 76 years was determined in only one sample from the Mazgirt-Dedebağ area. Travertines primarily consist of low magnesian calcite and form the spherical pisoids. Amorphous iron oxide (up to 2.93%), other metal concentrations (As: 753.3 ppm; Co: 14.3 ppm; Cu: 4.9 ppm; Mn: 4094 ppm; Zn: 4.7 ppm), and heavy stabile isotope values (δ18Ocalcite (SMOW) ‰ and δ13Ccalcite (PDB)) have increasing trends from the outside to the inside of the banded travertines. The estimated δ18OH2O isotope values in both ancient and modern travertine samples show that the thermal water temperature decreased approximately 17 °C from ancient to modern travertine formations. Algal species of Cyanophyta (blue/green algae), Chlorophyceae (green algae), and Bacillariophyta are predominant in both the Mazgirt and Karakoçan travertines. Oscillatoria is dominant in the studied thermal waters that are found as superficial mats on the travertines and are often common in sulfide-rich thermal waters.

Key words: Geochemistry, Mazgirt, Karakoçan, Travertine, Turkey

Received: 16.04.2015 Accepted/Published Online: 09.07.2015 Printed: 30.11.2015

Research Article

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are among the reasons for the changes in travertine precipitation. Paleoclimate oscillations affect the amount of fluid discharge or the opening of the feeding fractures. The  thermal water  features are a favorable combination of climatic and geologic factors.

According to Pentecost and Viles (1994), travertines can be divided into two geochemical groups: i) meteogene travertines, where carbon dioxide dissolved in water occurs in the soil and epigene environment; and ii) thermogene travertines, where carbon dioxide is generated from thermal sources, such as the hydrolysis and oxidation of reduced carbon and the decarbonation of limestone, directly from the upper mantle.

Petrographical features, morphological structures, geological characteristics, storage environments, microbiological features, and isotope geochemistry of the travertines located in the western and central Anatolian parts of Turkey have been extensively studied (Altunel and Hancock, 1993a, 1993b, 1993c; Altunel, 1996; Bayarı and Kurttaş, 1997; Pentecost et al., 1997; Ayaz and Gökçe, 1998; Altunel et al., 1999; Çakır, 1999; Tekin and Ayyıldız, 2001; Ayaz, 2002; Altunel and Karabacak, 2005; Kele et al., 2011; Uysal et al., 2011; Mesci et al., 2013, Özkul et al., 2013). A multidisciplinary study combining sedimentological, paleontological, and paleoanthropological observations was performed by Lebatard et al. (2014), who provided

Figure 1. (a) Location map; (b) satellite map of the study area.

MFZ

OFZ

NAFZ

KFZ

Elazığ

Bingöl

Mazgirt

Tunceli

Karakoçan

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an absolute chronological framework for the upper fossiliferous travertine unit where the Kocabaş hominid and fauna were discovered at the Denizli-Kocabaş travertine. The paper constrained the minimum age of 1.1 Ma for the end of massive travertine deposition. The actual age of the fossils is likely to be in the 1.1–1.3 Ma range, which is in close agreement with the paleoanthropological data.

The paleoanthropological conclusions based on morphometric comparisons have implied that the Kocabaş hominid belongs to the Homo erectus s.l. group that included Chinese and African fossils and was different from Middle and Upper Pleistocene specimens. This has been confirmed by the large mammal assemblage, typical of the Late Villafranchian (Lebatard et al., 2014).

Tekin and Ayyıldız (2001) indicated that the travertines in the region of Sıcakçermik (Sivas) are formed from semi-self-shaped prismatic-tabular calcite crystals. In that study, it was mentioned that calcite crystals that formed the pisoids exhibit gradual growth and contain regular cracks that are the product of shock cooling. The same researchers emphasized that the δ13C and the δ18O values of the different types of travertines range from 6.95‰ to 8.09‰ and from 15.73‰ to 16.76‰, respectively. In light of these stable isotope data, it was mentioned that microbiological activity (blue/green algae) has an effect on the travertine formations and outgassing effects on the Sıcakçermik travertines.

According to Ayaz and Gökçe (1998) and Ayaz (2002), the Sıcak Çermik, Sarıkaya, and Uyuz Çermik travertines, which are located in Central Anatolia along the main fault zones and cracks, were formed by the thermal waters heated by the cooling magma of the Bayat volcanites or other hot volcanic masses. The geotectonic studies focused on the relationships between bedded and banded travertine of the Çukurbağ-Denizli fissure ridge indicated that the banded veins were diachronous and migrated through time, suggesting a progressive fault zone enlargement in the footwall. Such a fault zone was characterized by polycyclic activity, with normal to transtensional kinematics, and was active during the latest Quaternary (Filippis et al., 2013). The formation of banded veins was coeval with bedded travertine deposition and strictly depends on fault activity due to the efficient conduits for thermal water migration, therefore highlighting the fundamental role of travertine fissure-ridges in reconstructing paleotectonic activity in a region (Brogi et al., 2014a, 2014b). It is emphasized in these studies that travertine morphologies develop depending on the temperature, depth, carbonate density in the precipitation environment, and flora change, depending on the old topography. The effects of the climate conditions on the algal flora that are related to travertine formations were explained by Bayarı and

Kurttaş (1997) for the Yerköprü (Aladağlar) travertines. These studies indicated that the biochemical contribution concerning the formations of travertine reaches its climax in summer. Pentecost et al. (1997) studied the phototrophic microorganisms of the Pamukkale (Denizli) travertine. These authors indicated that a wide range of algae colonized the Pamukkale travertine and the distribution of the algae communities was controlled largely by water flow and the degree of desiccation. These authors also mentioned that the evaporation of thermal water might play a role in travertine formation.

The objectives of the present study are to correlate the major and trace element concentrations of the thermal waters and travertines, to determine the distribution of trace element effects on the travertine mineralogy, and to define the relationship among thermal water, travertine, and algae geochemistry.

2. Geological settingTurkey is seismically one of the most active regions of the world and is located within the Mediterranean Earthquake Zone, which is a complicated deformation area that was generated from the continental collision between the African-Arabian and Eurasian continents. These deformations contain thrust faults, suture zones, and active strike slip and normal faults, as well as basin formations arising from these faults. The region attained a new geometry after the East Anatolian Fault System became active approximately 3 million years ago (Westaway and Arger, 1996). The area between the left-lateral Malatya-Ovacık Fault Zone in the NW and the East Anatolian Fault System has the same characteristics as the Keban Block in the SE, where a NW-SE linear fault, an active right-lateral fault, and direction slip faults are found, which are the conjugation of these faults at the Karlıova triple junction point. The most important of these faults, which have shifting lengths, is the KFZ, which produced many minor earthquakes at the end of January and beginning of February in 2007, the Büyükyurt Fault Zone, the Pülümür-Kiği Fault Zone, and the Pertek Fault Zone.

The studied travertines have formed on an oblique-slip normal fault with a right- and left-lateral strike-slip, the KFZ and PFZ, and NW-trending extension cracks at the Karlıova triple junction in the convergence region of the main, namely Eurasian, African, and Arabian, plates.

As a result of the detailed mapping performed in the study area, five units of different characteristics were mapped in the region, over the age range extending from the Paleozoic to the Cenozoic (Figure 2). From the bottom upwards, these units are Permo-Triassic Keban Metamorphites, the Lower Miocene Alibonca Formation, the Upper Miocene-Pliocene Karabakır Formation, and the Plio-Quaternary travertines and alluvium.

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The Keban Metamorphites, which are the oldest unit of the study area, outcrop on the right coast of Peri Creek around Hamam Mountain and in the south of the Dedebağ village in the study area (Figure 2). Considering the regional scale, the Keban Metamorphites, which are represented by a lithology consisting of marble, recrystallized limestone-calc-schist, and metaconglomerate and calc-phyllite, are composed of highly massive recrystallized limestones in the study area. The limestones are dark yellow, light brown, and grayish, and their fresh fault surfaces are white. This unit, which appears massive, exhibits medium-thick bedding, and it is quite faulted and cracked. On the recrystallized limestones of the Keban Metamorphites, karsting is characterized by cracks and faults, which increase as one goes from the surface through the deep end. Cracks and karstic spaces that are formed on the Keban recrystallized limestones are mainly filled by calcite

crystals. The effects of regional pressure movements are from the Late Cretaceous to the Early Pliocene in the study area.

The Alibonca Formation is commonly followed south of Hamam Mountain in the study area (Figure 2). The Lower Miocene Alibonca Formation is overlaid by Permo-Triassic Keban Metamorphites with angular discordance. The Alibonca Formation generally consists of conglomerate, limestone, marl, and sandstone. Bedded and partly massive-structured limestones pass to marl containing internal levels of sandstone towards the upper levels. The red conglomerates are observed on the base of the unit that exhibits a lateral-vertical relation with the limestone. The Upper Miocene-Lower Pliocene Karabakır Formation has the largest expansion in the study area (Figure 2). The unit is overlaid by the Alibonca Formation with an angular discordance and is represented

.

1 km

N

KARAKOÇAN FAULT

PAMUKLU FFAULT ZONE

750

1000

1250

1500

A

A’

B’

Peri Stream

ZONE

Hamam CrestKarakocan Fault Zone

A-A’ Section

NW SE

575000

4315000

585000

Bütünlü

Yogunagaç

Tor Crest

Üçbudak

Ohi Stream

Sülüklü Lake

Kepir

Akdüven Crest

Akdüven4320000

Quaternary Aluvium

TravertineQuaternary

Upper MioceneKarabakır Formation

Lower MioceneAlibonca Formation

Permo-TriassicKeban Metamorphites

Normal strike slip faultOblique -slip normal faultThrust faultThermal water

Stream

Figure 2. Geology map of the studied area.

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by pyroclastics (tuff, agglomerate), basaltic and andesitic lavas, and sedimentary rocks, which have lateral and vertical relationships with volcanites. The sedimentary rocks are primarily composed of clayed limestone.

The Plio-Quaternary alluvium is composed of gravel, sand, clay, and silt deposits that are accumulated within the Peri and Ohi creeks. The thickness of the alluvium reaches 20 m at some places, especially in the flood plains of these rivers. The Plio-Quaternary travertine deposits are seen as independent surfacings on the segments of the KFZ, ranging between a few tens of m2 and a few km2. In contrast, there are small-scale surfacings on the part where the anticline of Hamam Mountain is deeply worn by Peri Creek. The travertine consists of thin and porous laminas, and its thickness reaches to 25 m from place to place. Depending particularly on thermal waters related with the activity of the faults, the formation of travertine continues even today.

3. Materials and methodsIn the studied area, nine travertine samples (from T1t to T9t) and eight banded travertine samples (I1 to I8), i.e. a total of 17 samples, were collected and indicated on the sampling location map. The samples from the banded travertine were collected on a scale from the outside to the center. Three thermal water samples (from T1w to T3w) from Bağın (Dedebağ)-Mazgirt, four thermal water samples (from T6w to T9w) from Yoğunağaç-Karakoçan, one sample from Sülüklü mineral water (T4w), and one sample from the Ilıca thermal spring pond (T5w) were collected in the present study (Figure 3). A total of six algae samples were collected from the Kolan and Bağın thermal springs and from Sülüklü mineral water (Figure 3). Age determinations of the samples from Mazgirt-Dedebağ were performed by determination of the 230Th/234U radio isotope rates using a mass spectrometer (MS) at the Paul Scherrer Institute of Switzerland. To determine the petrographic features of travertines, 35 thin sections were

T5 w,t,a

T4 w, t, a

T2w,tT3 w,t,a

T6 w,t

T1w,t

T8 w,tT9w,t,a

I1 t-I8 t

Kirazlı Crest

4320000Akdüven

Dedebag

Bütünlü

Hamam Mountain

Yogunagac

4315000

575000 580000

Tor Mountain

Ucbudak

Çayırgülü

585000

Kızılca

Balcalı

Peri Stream

Ohi Stream

1 km

N

MazgirtT1w, T2w, T3w: Bağin �ermal springsT4w: Sülüklü mineral waterT5w: Ilıca thermal spring pondT6w,T7w, T8w, T9w: Kolan thermal springsT1t, T2t, T3t : Bağin travertinesT4t: Sülüklü travertineT5t: Ilıca travertineT6t, T7t, T8t, T9t: Kolan travertinesI1-I8 : Banded traverine sample sitesT2a, T3a: Bağin algaeT4a: Sülüklü algaeT5a: Ilıca algaeT7a, T9a : Kolan algae

T7 w,t,a

Karakoçan

Figure 3. The map of the sample sites for thermal water, travertine, and algae.

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prepared, and the mineralogical features were determined using a scanning electron microscope-energy dispersive system and X-ray diffractometer (SEM-EDS-XRD) in the laboratories of the Turkish Petroleum Corporation. The chemical analyses of water, travertine, and algae samples were performed in the ACME Analytical Laboratories (Canada) using the methods of inductively coupled plasma-optic emission spectrometry (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP- MS). The isotope composition rates of δ18O and δ13C were determined in 12 travertine samples. Carbon and oxygen isotope analyses in travertine samples were performed according to Degans and Epstein (1964) at Geochron Laboratories (USA). The algae samples were washed in distilled deionized water in the laboratory and then dried naturally in air for 24 h. Trace element analyses of the algae samples were performed in an ICP mass spectrometer using 1 g split digested in HNO3 and followed by aqua regia at the ACME laboratories.

4. Description and interpretation of travertine faciesSeveral attempts have been made to classify travertines according to their morphology and setting. In the study of Bargar (1978), the carbonates on which calcic and carbonated (Ca (HCO3)2) waters, which generally emerge on low-pitched surfaces, precipitate as terraces or sets

while flowing down-gradient were first defined as “terrace-type travertines”. In such formations, the shapes of pools, basins, or cups provide an aesthetic appearance, and along their edge parts, various eave structures are frequently encountered (Ayaz, 2002). Terrace-type travertine was precipitated in the beginning as a result of the encounter of the waters flowing through a low-pitched topography with gravel or block deposits on the base and rock ridges or small banks, which have a vertical axis with respect to the flow. Such barriers, which retard the water and enable its deposition, could also be placed by humans. Travertine precipitations in these areas have increased in time through deposition and have formed basin or cup structures from place to place. The term “travertine precipitation” was used by Bargar (1978), Chafetz and Folk (1984), and Altunel and Hancock (1993c) to describe the travertines that are formed in various locations throughout the world. Travertines that are precipitated by Ca(HCO3)2 waters emerging from horizontal and low-pitched surfaces or advanced cracks throughout the long axis of a ridge in the form of a ridge or saddle while flowing towards the two sides are called “ridge-type travertine” (Ayaz 2002). Ridge-type travertine exhibits banded and bedded structures. The travertines in the study area were determined to be “banded” (Figures 4a–4c), “terrace” (Figures 4d–4h), and “ridge” (Figure 4i) types.

Figure 4. Morphological features of the travertine formations, the banded travertines (a, b, c), the terrace-type travertines (d, e, f, g, h), and the ridge-type travertines (i).

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5. Results 5.1. Age determination of travertineAs is known, with the radiometric method of U/Th, ages approximately ranging from 500 to 400,000 years can be determined (Gaff and Shevenell, 1987). The age determined for the Quaternary travertine using the method of U/Th was in the range of 111,000 to 350,000 years by Luque and Julià (2007). U-series dating was used on late Quaternary travertine in coseismic fissures and ridge-type travertines in Turkey (Uysal et al., 2007; Temiz et al., 2009; Temiz and Eikenberg, 2011). A total of eight samples were collected from the center to the outside from banded travertines in the studied area for radiometric age determination. However, the U/Th radiometric age method could be performed on only one sample collected from the banded travertines and the age was calculated as 160,000 ± 76 years

according to Rosenbauer (1991). It was estimated that travertines that are formed on the valley slopes created by Peri Creek are older than the travertines that developed within the crack system. Travertine formations are found to persist even today, depending on the thermal waters.

5.2. Travertine mineralogy and petrography The stromatolites are frequently observed in the travertines numbered I2, I3, I4, and I5 (Figures 5a–5d). In addition, pisolitic structures (Figure 5e) and alternation of fibrous aragonite (Figure 5f) are observed in these travertine samples (I6, I7, and I8). Green algae (Chara) fossils and plant remnants are observed as one moves from the center to the outside from banded-type travertine in the studied area. Although there is commonly a dendritic mineral (calcite, quartz, and aragonite) grain within the core of the pisolitic structures, some of them do not have such a core.

Figure 5. Photomicrographs from the same sample and directly from the center of a pisoid (pelmicritic texture; dark areas), which is surrounded by branching sparry calcite crystals (a, b, c, d). Pisoids (e) and (f) alternation of fibrous aragonite.

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Pisolitic zones are interlocked concentric oscillations. Travertine samples numbered from T1 to T9 include calcite, quartz, hematite, and aragonite, in accordance with the abundance order according to the XRD results. SEM images indicate that the mineral composites in some sections vary as silica, calcite, aragonite, goethite, and clay minerals according to the level of abundance (Figure 6); the EDS diagrams also support this result (Figure 7). Based on the XRD analysis of 10 travertine samples, calcite is the most common mineral at all sites. Aragonite and calcite are abundant in the modern travertines deposited at both the Mazgirt-Dedebağ (T1, T2, T3) and the Karakoçan-Yoğunağaç (T6-T9) thermal springs locations. Although micrite (3-μm-long grains) is dominant in the banded travertine, crystalline crusts and secondary pore fills are formed largely of coarse spar calcite. Minor amounts of aragonite are also present in the distal part of the discharge area. Some samples contain detrital minerals, including quartz, goethite, and clay minerals. Figure 7 (EDS diagrams) indicates higher Si and Al values. At the Karakoçan and the Mazgirt thermal springs, aragonite, in varying amounts, is associated with the banded and coated gas bubble travertine, where mesothermal waters are discharged at a temperature of 40–45 °C. Some of

the banded travertines from the Mazgirt-Dedebağ and Karakoçan-Yoğunağaç ridge are formed by aragonite.

The petrographic features of the banded travertine (from I1 to I8) were determined by preparing thin sections and examining these sections. The banded travertine followed a fading of color tones from red to white, and they were also observed as an intercalation of colors, such as white or the white and reddish color tones in the studied area. The bands generally do not vary in a linear manner. The bands proceed in light or very wavy ways. The bands could be in the form of nested millimetric bands having a thickness of 15–40 cm. The bands are observed on the intercalation of white and reddish bands of millimetric scale. Travertine within the banded structure sometimes includes an intraclast with a dimension of approximately 1–5 cm and with colors of either white or reddish. Intraclasts are thought to be precipitated from synsedimentary carbonate layers and have the same age as the sedimentation. These intraclasts are constituted as a result of the sedimentation. The stromatolites are composed of thin, more or less flat laminae of calcite with a specific texture. The stromatolites are not formed by limited individual colonies of constructing organisms; rather, layers or mats of constructing organisms form them.

Figure 6. SEM images from the sample exhibiting clumps of calcite sheets and rhombohedrons, q, quartz (a); ar, aragonite (b); cal, calcite; and car, carbonate (c and d).

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There is a trend from ooid through polyooid and ooid-bag to stromatolite, in which the accreting layers exhibit decreasing influence of a central nucleus in determining the form of growth. The stromatolite-producing microbial community requires a higher alkalinity than the ooid-producing organisms. The etched surfaces of stromatolites result from the decay of organic matter under a cover of clay or living biofilm, resulting in the formation of CO2, thereby lowering the pH and consequently leading to acidification of the water and dissolution of carbonate (Paul et al., 2011).

5.3. Geochemistry of thermal waters, travertine, and algaeThe major and trace element analyses of thermal waters, travertine, banded travertine, and algae are presented in Tables 1–4, respectively. Precipitation from the thermal waters (Table 1) has produced vast white calcite deposits with spectacular arrays of terraces and rimstone pools. The thermal water samples are collected from the same location at the travertine deposition points. Discharge of thermal waters occurs along a fault with N10°W direction at the core of the Mount Hamam anticline. The temperature, pH, and electrical conductivity (EC) of the thermal waters are in the ranges of 24.5 to 44.4 °C, 6.06 to 6.48, and 1020 to 4953 µS/cm, respectively (Table 1). The temperature, pH, and EC of the T4 mineral water are 17.2 °C, 6.6, and

4170 µS/cm, respectively. The saturation index values of calcite of the thermal waters change between –0.53 and 0.9. The δ13CDIC values of thermal waters are in the range of –0.4‰ to 4.4‰. The Dedebağ (Bağın) thermal water (T1) and the Ilıca thermal spring pond (T5) have EC values in the range of 1020 to 4860 µS/cm and a negative saturation calcite index (–0.53 and –0.41) for ridge-type travertine. It is thought that the negative saturation index of calcite is affected by precipitation of metals in the ridge-type travertines, where sulfur circulation might be faster than at other locations. Almost all of the concentrations of the ions of the waters in the basin were found to increase with increasing EC; however, EC has not been linked to increasing water temperature (Table 1).

Table 2 shows the major and trace element concentrations and the δ13C-δ18O‰ isotopic compositions of nine travertine samples. As the values in the travertine samples range between 45.9 and >10,000 ppm, the Ba values range between 9.4 and 154.9 ppm, the Cu values range between 0.07 and 5.9 ppm, the Mn values range between 18 and 149 ppm, the Pb values range between 0.04 and 15.5 ppm, and the Zn values range between 2.1 and 21 ppm. Elements such as Ca, Li, Mg, Mn, Na, Cu, Fe, Sb, Sr, Zn, and Zr do not exhibit a linear relationship with water temperature. This case could suggest that the above-described major and trace elements may be enriched in calcite, either primary or secondary,

a

FeFeCa

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Ti Fe

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Figure 7. EDS spectra of some of the travertine samples.

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Tabl

e 1.

Che

mic

al a

naly

ses o

f the

rmal

wat

ers (

Sept

embe

r 200

8) (T

= °C

, EC

= µ

S/cm

, * =

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ther

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e sa

tura

tion

inde

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ith re

spec

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ite a

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e pa

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ater

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as c

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REEQ

C (h

ttp://

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A

l A

s B

Ba

Be

Br

Ca*

C

o C

u Fe

K

* Li

M

g*

Mn

Na*

Rb S*

SbSr

Zn

Zr Sı

calc

ite

δ13C

DIC

(‰)

T1w

91

23

32

8099

14

3 5.

26

455

64.4

2 0.

65

21.4

38

97

8.50

88

1.8

11.8

6 51

.55

31.2

5 34

4.7

107

137.

29

9687

25

0.

87

–0.5

3na

T2w

10

9 22

07

7336

12

9.25

4.

91

466

62.2

5 17

.8

18.3

24

87

7.92

78

3.1

11.3

5 47

.1

30.4

2 30

8.9

81

83.8

83

20

30.7

0.

6 0.

78

3.6

T3w

94

22

48

7610

14

1.82

4.

4 44

8 64

.09

5.56

20

.8

2757

8.

27

859.

1 11

.62

55.3

9 31

.20

312.

5 93

17

.69

8977

32

.3

0.94

0.

9 4.

4

T4w

21

0 10

91

6948

11

1.43

1.

93

474

61.5

2 20

.42

17.8

46

11

6.41

81

2.7

14.8

4 89

.09

43.2

1 20

2.9

48

100.

6 10

755

57.6

1.

06

0.11

na

T5w

24

84

19

0 56

.39

<0.0

5 21

19

.17

0.14

14

.9

<10

0.35

24

.4

2.46

1.

19

21.9

6 10

.62

47

84.2

29

65

12.9

0.

16

–0.4

1–0

.4

T6w

10

7 48

93

6623

17

9.9

2.73

48

7 37

.24

15.2

6 7.

7 65

27

5.69

63

5.2

7.85

32

.84

23.9

6 21

8 59

16

2.58

68

04

16.3

0.

6 0.

4 na

T7w

19

3 27

69

1050

3 18

4.4

5.55

74

8 67

.31

4.28

44

.5

2754

9.

76

1051

.5

12.0

9 59

.87

38.8

0 36

6.5

92

100.

61

10,0

66

77.7

0.

88

0.9

3.9

T8w

12

8 31

86

9679

18

8.5

6.13

69

8 66

.06

8.82

5.

7 41

94

9.34

10

45.2

12

.04

56.1

3 37

.86

351.

3 96

34

.54

10,1

87

17.1

0.

74

0.69

3.

5

T9w

34

6 59

33

6623

18

1.18

3.

39

438

36.2

0 1.

62

9.1

9049

5.

71

582.

1 7.

65

49.1

2

23.

02 21

5.2

58

36.6

6 65

44

25.2

0.

6 0.

25

4

Tabl

e 1.

(Con

tinue

d).

T

pH

EC

Cl*

SO

4*

HC

O3*

T1w

37

.5

6.22

48

60

130.

9 18

8.0

655

T2w

38

.0

6.06

40

22

126.

2 18

1.5

650

T3w

38

.0

6.4

4871

13

3.7

186.

1 67

8

T4w

17

.2

6.6

4170

12

3.8

106.

1 11

05

T5w

24

.5

6.21

10

20

7.9

119.

3 16

6

T6w

26

.9

6.1

2917

12

0.7

151.

7 62

0

T7w

44

.0

6.39

40

91

170.

1 19

1.7

440

T8w

44

.4

6.4

3948

16

8.4

191.

5 74

4

T9w

28

.8

6.08

28

34

115.

1 14

5.5

482

617

KALENDER et al. / Turkish J Earth Sci

Tabl

e 3.

Maj

or a

nd tr

ace

elem

ents

and

13C

and

18O

isot

ope

conc

entr

atio

ns in

ban

ded

trav

ertin

es (f

rom

I1 to

I8).

M

o C

u Pb

Zn

N

i C

o M

n A

s U

Sr

Sb

C

r Ba

Zr

Y

Be

Li

Fe*

Ca*

P*

M

g*

Al*

N

a*

δ 13

C

(PD

B) ‰

δ 18

O

(SM

OW

)

‰

I1

0.73

4.

9 0.

27

4.7

8.6

14.3

40

94

753.

3 0.

7 44

7 3.

21

2.9

6.2

4.3

1.09

4.

1 1.

8 0.

7 34

.24

0.01

2 0.

13

0.1

0.00

5 8.

7 17

.4

I2

0.11

0.

19

0.08

0.

7 0.

1 0.

3 28

6 10

2.7

0.1

369

0.26

0.

8 6.

6 1.

2 0.

19

2.6

0.1

0.13

34

.4

0.00

6 0.

08

0.02

0.

002

8 17

.1

I3

0.18

0.

16

0.15

0.

7 0.

1 0.

2 23

8 54

.3

0.1

362

0.15

0.

6 6.

1 1

0.28

2.

5 0.

3 0.

05

34.6

1 0.

005

0.07

0.

04

0.00

5 7.

5 16

.6

I4

0.21

2.

62

0.09

3.

3 2.

9 2

483

708.

9 0.

4 49

8 2.

72

2 15

.8

3.9

0.89

4

0.3

0.59

36

.35

0.00

9 0.

15

0.05

0.

006

na

na

I5

0.22

0.

09

0.09

0.

7 0.

1 0.

3 20

2 16

2.5

0.2

832

0.2

0.6

13.4

1.

2 0.

2 3.

5 0.

2 0.

13

35.0

2 0.

008

0.18

0.

03

0.01

9 na

na

I6

0.

08

0.1

0.07

0.

3 0.

8 0.

1 17

1 13

5.5

0.1

1095

0.

04

0.7

10.6

1.

2 0.

12

3.7

0.2

0.04

35

.24

0.00

6 0.

28

0.02

0.

023

na

na

I7

0.07

0.

27

0.06

0.

6 0.

6 0.

2 19

3 39

.6

0.1

439

0.04

0.

9 9.

8 0.

9 0.

07

3.1

0.1

0.01

34

.56

0.00

5 0.

1 0.

01

0.00

9 na

na

I8

0.

17

0.48

0.

09

1.7

0.3

0.9

460

88.6

0.

2 55

6 0.

14

1.9

12.1

1.

3 0.

19

3.5

0.2

0.07

35

.24

0.05

5 0.

15

0.04

0.

06

7.3

16.5

Tabl

e 2.

Maj

or a

nd tr

ace

elem

ents

and

13C

and

18O

isot

ope

conc

entr

atio

ns in

trav

ertin

e. *

= %

; th

e ot

hers

are

giv

en a

s ppm

.

A

l *

As

Pb

Ba

Be

Sc

Ca

* C

o C

u Fe

* K

* Li

M

g *

Mn

Na

* Rb

S

* Sb

Sr

Zn

Zr

δ

13C

(PD

B)

‰

δ 18

O

(SM

OW

)

‰

T1t

0.06

47

8.7

0.41

58

.2

0.9

0.2

27.2

6 0.

4 5.

79

0.37

0.

01

5.1

0.34

71

0.

056

1.2

0.14

0.

03

2992

21

0.

9 11

21

.6

T2t

0.06

10

4.6

0.74

71

0.

5 0.

2 34

.48

0.9

1.06

0.

15

0.04

6.

7 0.

38

80

0.25

7 2

0.2

0.04

28

20

15.9

1.

4 na

na

T3t

0.14

45

.9

0.51

42

.6

0.1

0.5

33.0

9 0.

7 2.

36

0.17

0.

02

1.3

0.01

18

0.

007

2.4

0.14

0.

08

884.

9 6.

1 1.

4 5.

2 19

.4

T4t

0.04

52

71

0.26

11

0 9.

3 0.

2 31

.98

0.3

0.23

1.

39

0.02

3.

2 0.

01

87

0.06

6 1

0.36

0.

24

2523

7.

7 0.

6 8.

7 18

.3

T5t

0.05

37

2.5

15.5

12

.8

1.1

0.6

35.2

8 0.

5 4.

35

0.23

0.

01

0.7

0.21

13

3 0.

01

0.7

0.02

0.

45

344.

1 5.

5 1.

3 8 .

2 17

.3

T6t

0.02

>1

0,00

0 0.

04

148

11.7

0.

2 32

.64

0.5

0.15

2.

81

0.02

3.

5 0.

01

50

0.05

9 0.

7 0.

33

0.4

2167

4.

5 0.

4 3.

3 25

.1

T7t

0.01

14

8 1.

14

9.4

0.5

0.1

31.5

0.

3 1.

58

0.21

0.

01

0.5

0.01

31

0.

009

0.3

0.04

0.

33

280.

4 1.

6 0.

3 3

27.2

T8t

0.03

71

92

0.37

14

5 14

.4

0.7

33.6

5 0.

2 0.

25

1.8

0.09

7

0.25

11

6 0.

287

3.8

0.6

0.04

27

11

15.8

0.

8 5.

2 15

.2

T9t

0.02

11

80

1.1

154.

9 5.

2 0.

4 34

.88

0.2

0.42

0.

48

0.02

2.

4 0.

3 10

8 0.

07

0.6

0.49

0.

03

2267

6.

3 1.

2 6.

8 -

618

KALENDER et al. / Turkish J Earth Sci

in a cavity. In fact, the same major and trace element contents in travertine exhibit a normal distribution when they are correlated with water temperature. Trace elements of travertine, such as As, B, Ba, Rb, and S, decrease with the decrease temperature of thermal waters. Figure 8 shows the relationship between As, Ba, and S and temperature in the thermal waters, travertine, and algae. The concentrations of As, Ba, and S in thermal waters exhibited a linear relationship with increasing temperature (Figures 8a–8c). The S concentration in thermal waters decreased as the temperature decreased, and hence the Ba and As concentrations of travertine and algae increased (Figures 8d–8i). Precipitation is an effective factor for the decreasing As, Ba, and S values in water at lower temperatures. The positive relationship between As and Ba and SO4 demonstrated that these elements could be moved and form components in high-temperature waters based on the S concentration. These elements exhibited a log-normal distribution due to the travertine formation process under the low temperatures.

The stable carbon (δ13C) and oxygen (δ18O) compositions of the travertine deposits were determined from nine samples. The δ13C values range from 3‰ to 11‰ PDB, whereas the δ18O values range from 15.2‰ to 27.2‰ SMOW (Tables 2 and 3). According to Özkul et al. (2013), the recent and fossil travertines have high δ13C values; however, water temperature and lithology may

have affected the δ13C and δ18O values. Drake et al. (2014) indicated that δ18O and δ13C in the different fracture zones were consistent with precipitation from waters of different salinity and decreasing organic input with depth, respectively. The latter is also supported by biomarkers, providing clear indications of sulfate-reducing bacteria-related organic compounds, except in the deepest zone.

In Table 3, a total of eight samples collected from the northeast Dedebağ banded travertine (from I1 to I8) from the center to the outside are presented. According to Table 3, the Mo values range between 0.73 and 0.07 ppm, the Cu values range between 4.9 and 0.10 ppm, the Pb values range between 0.27 and 0.11 ppm, the Zn values range between 4.7 and 0.3 ppm, the Mn values range between 4094 and 171 ppm, the As values range between 1682 and 23.8 ppm, and the Fe values range between 2.93 and 0.01 wt.%. In Figure 9, depending on the sample-taking points, the As, Ba, Cu, Mn, Pb, and Zn distributions of the travertine samples were studied. The Cu and Pb concentrations in the main emergence points of T5, T7, and T9 were found to be at high levels compared to As, Ba, Mn, and Zn.

On the basis of stable isotope analyses from inside to outside in a banded travertine, average δ18Ocalcite (SMOW) ‰ and δ13Ccalcite (PDB) ‰ of the travertine bands changed in the ranges of 16.5‰ to 17.4 ‰ and 7.3‰ to 8.7‰, respectively. The heavy isotopes are increased inside of the banded travertine. The average isotopic composition

Table 4. Determination of micro- and macroalgae species in thermal waters (June 2009).

T2a (at 38 °C)

T3a (at 38 °C)

T4 (at 17.2 °C)

T5 (at 24.5 °C)

T7a (at 44 °C)

T9a (at 28.8 °C)

Microscopic determination Macroscopic determination Microscopic determination

Cyanophyta Oscillaturia limosa Ag. ex Gom. O. sancta (Kütz.) Gomont O. tenuis Ag. ex Gom. O. princips Vaucher Chrococcus turgidus

Cyanophyta Oscillaturia limosa Ag. ex Gomont O. sancta (Kütz.) Gomont O. tenuis Ag. ex Gom. Chlorophyta

Chlorophyta Chlorophyta

Cyanophyta Spirulina platensis (Gomont) Geitler S. tennusima Chroococcus. minutus Nag. C. turgidus Gloeocapsa minor (Kütz.) Hollerb.

Cyanophyta

Oscillaturia terebriformis Ag. ex. Gomont

O. tenuis Ag. ex Gum.

Phormidium laminasum Bory. Gom.

Phormidium sp.

Chlorophyta

619

KALENDER et al. / Turkish J Earth Sci

00.10.20.30.40.50.60.7

0 20 40 60

S (%

wt)

in tr

aver

tines

Temperature (oC) of thermal waters

020406080

100120

0 20 40 60S (p

pm) i

n th

erm

al w

ater

s

0

50

100

150

200

0 20 40 60

Ba (p

pm) i

n th

erm

al w

ater

s

02000400060008000

10,00012,000

As (

ppm

) in

trav

ertin

es

0

50

100

150

200

0 20 40 60

Ba (p

pm) i

n tr

aver

tines

Temperature (oC) of thermal waters

Temperature (°C) of thermal waters Temperature (°C) of thermal waters

Temperature (°C) of thermal waters

Temperature (°C) of thermal waters

Temperature (°C) of thermal waters Temperature (°C) of thermal waters

Temperature (°C) of thermal waters

01000200030004000500060007000

0 20 40 60As (

ppb)

in th

erm

al w

ater

s

00.05

0.10.15

0.20.25

0.30.35

0.4

0 10 20 30 40 50

S (%

wt)

in a

lgae

02000400060008000

10,00012,000

0 10 20 30 40 50

As (p

pm) i

n al

gae

050

100150200250300

0 20 40 60

Ba (p

pm) i

n al

gae

a b

c d

e f

g

i

h

Figure 8. The diagrams showing the relationships among As, Ba, and S and temperature in thermal waters (a, b, c), travertines (d, e, f), and algae samples (g, h, i).

620

KALENDER et al. / Turkish J Earth Sci

is relatively higher compared to the average δ18Ocalcite and δ13Ccalcite, based on conventional analyses due to the detrital-rich bands (O’Brien et al., 2006). In Figure 9, the trace element concentrations are high for the I4 and I8 samples. The stable isotope concentrations are low at the same locations due to significant δ18Ocalcite and δ13Ccalcite decreases, indicating that paleoclimatic effects (e.g., water temperature changes in summer and winter) are important factors on travertine geochemistry.

Algae are unicellular organisms living in aqueous mediums. The best-known species are blue-green algae. However, algae can principally live within territorial waters, such as resources, streams, and rivers, in a planktonic and benthic way. Although there are a large number of parameters for the formation of the algae, the insolation rate, air temperature, and water temperature are the most important environmental factors. In the study area, the algae species of the classes of Cyanophyta (blue/green algae), Chlorophyceae (green algae), and Bacillariophyta were described by the Biology Department of Fırat University (Table 4). The algae species have been described at micro- and macroscales, and the descriptions at the microscale were collected from the travertine relationship with the thermal waters. All of the samples were collected in June. In the present study, a total of 28 taxa were determined in the Cyanophyta, Chlorophyta, and Bacillariophyta divisions, and the related temperatures of the thermal waters are presented in Table 4.

Cyanophyta (blue-green algae) has an important role in the formation of travertines. Some species of

Cyanophyta have a dominant distribution in the travertine formations related to the S-enriched thermal waters. These species are tolerant to a wide range of light intensities and high pCO2 and they survive desiccation well (Castenholz, 2002). Phormidium laminasum forms dark green mats (from green-blue algae) in the thermal waters at 28.8 °C (T9 location). Generally, the species of Spirulina form dark green mats in the S-enriched thermal waters at temperatures from 40 to 45 °C. These species could also form at the lower temperatures that are controlled by the S concentration of the thermal waters (Pentecost, 1995a). Table 4 indicates that Spirulina and Oscillatoria were found at the T7 location due to the appropriate temperature (44 °C) and SO4 concentration (191 mg/L) at that location. The other species, Oscillatoria sp., was found in the other locations (T1, T2, T3, and T9) at lower temperatures (26.9–38 °C) and at high SO4 concentrations (119–186 mg/L). Chlorophyta species (green algae) are rarely encountered in sulfide-rich waters, and thermophiles are rare.

On the travertine, eukaryotic algae are often found to be associated with prokaryotes (Cyanophyta, Oscillatoriales), but eukaryotic algae usually tolerate less shade and are rarely found in water at a temperature exceeding 45 °C. Their growth is often more rapid in the warmer parts of the year; as a result, they will frequently overgrow Cyanophyta. Chlorophyta (green algae) was determined to be macroscopic at the T4a and T5a locations of lower temperatures (17.2 °C and 24.5 °C). The SO4 concentrations of the thermal waters (T4w and T5w) were lower than the others (Table 1). According to Pentecost (1995, 2005),

0.001

0.01

0.1

1

10

100

1000

10000

I1 I2 I3 I4 I5 I6 I7 I8

log v

alues

Dedebağ banded travertine

Mo Cu Pb Zn Ni Co Mn As U Sr Sb CrBa Zr Y Be Li Fe* Ca* P* Mg* Al* Na*

Figure 9. Distribution of the major and trace elements in the Dedebağ banded travertine from the outside to the inside.

621

KALENDER et al. / Turkish J Earth Sci

Chlorophyta is rarely encountered in S-rich waters, and thermophiles are rare. Approximately one-quarter of the 20 species known from the travertine are regularly encrusted with calcite and become incorporated into the travertine deposits. In the present study, the highest HCO3 concentration in the T4w (Table 1) indicated that Chlorophyta species were encrusted with calcite.

The algae, thermal water, and travertine element concentrations are presented in Table 5.

6. Discussion The geochemical characteristics of the travertine deposits are controlled by tectonics, seasonal climatic variations, and meteoric-origin deep and shallow waters in the basin. As the thermal waters ascend to the surface, they mix with the shallow cold groundwater at different ratios. In the study region, the upper crust is cut by numerous cracks. The groundwater circulates through these cracks, and the fluid pressure in these cracks is high. The investigated thermal waters ascend to the surface along the NW-SE right-lateral strike-slip KFZ and the left-lateral strike-slip Pamuklu fault where the travertines are deposited.

The PFZ and KFZ have a conjunction in the Karakoçan-Yoğunağaç and Mazgirt-Dedebağ areas. In extensional and transtensional provinces, the faults and associated fissures served as natural conduits for the emerging thermal waters. Fissure ridges are elongated, wedge-like structures that formed as ridge travertine was precipitated from the thermal waters that ascended along a fracture or fault plane (Altunel and Hancock, 1993c; Öztekin Okan, 2004; Dilsiz, 2006; Öztekin Okan et al., 2008; Brogi and Capezzuoli, 2009; Temiz et al., 2013; Brogi et al., 2014a; Mohajjel and Taghipour, 2014).

Consequently, tectonic activity in the studied area significantly controls the travertine deposition at the regional and local scales. In the thermal waters, except for As, the other heavy metals exhibit a medium-high positive correlation among each other. In addition, some metals, such as Sr, B, and Hg, could have been affected by the physical features of waters, such as temperature, pH, and alkalinity; in particular, Sb increases in direct proportion with As. In ridge-type travertines, the As and Ba concentrations are high, depending somewhat on water temperature. The effects of thermal water temperature on travertine formation might be correlated to the As concentration, e.g., the thermal water temperature is 17.2 °C at the T4 location, but the As concentration is 5271 ppm at the same terrace-type travertine in the Sülüklü area. In addition, the thermal water temperatures are measured as 26.9 and 44 °C at the T6 and T8 locations in the Yoğunağaç area, but the As concentration are >10,000 ppm and 7192 ppm (Figure 10). Deposition of travertine might be controlled by two major factors. The first is that

the As concentration in thermal waters is controlled by the travertine morphology, the travertine formation age, and the dissolution speed of As-containing iron and sulfur minerals. The As and Ba concentrations depended on the sulfur and sulfate concentrations in the waters and are affected by the seasonal temperature changes. During rainy periods, the As concentration decreases due to dilution, and during arid periods, the As concentration decreases with redox processes (Kumar et al., 2010). The second factor is that the meteoric waters mixing with the groundwater may affect the As and the other metal concentrations. The negative calcite saturation index (–0.4) and δ13C ‰ DIC (–0.4) at the T5 location indicate that the mixing process is an important factor for the metal concentrations of both travertine (δ18O 17.3‰) and the thermal water chemistry. The travertines were found to be grouped into four types according to their trace element and stable isotope compositions. The T6 and T7 travertines (δ18O 25–27‰) are enriched in heavy oxygen isotope composition; the T4 and T5 (δ18O 17.3–18.3‰) travertines have moderately heavy oxygen isotope composition; the T1 (δ18O 21.6‰ and δ13C 11‰) travertine has a moderately heavy oxygen composition and a high carbon isotope composition; the T8 (δ18O 15.2‰) travertine has a lower heavy oxygen isotope composition. It is thought that the formation of travertine types or the stable isotope composition of travertine might be related with the travertine age. This study does not include a systematic travertine dating process. Nevertheless, according to Ohomoto and Rye (1979), it was estimated that the δ18OH2O values are between 13.2‰ and 1.2‰. As a result, the δ18OH2O isotope composition values changed on a geological time scale with an exchange ratio of 12‰, which indicates that the travertine formation temperature decreased approximately 17 °C from ancient times to modern.

Particularly in banded travertine samples (from I1 to I8), metals (except Sr and Ca) were determined to be enriched in banded travertines related to the seasonal water temperature and the host-rock composition.

O’Brien et al. (2006) determined that a 1 °C increase in the water temperature corresponded to a 0.25‰ decrease in δ18Ocalcite. A combined air and water temperature fractionation effect of 0.4‰ per °C was found, approximately the difference between the average δ18O that they measured in modern travertine. The δ18Ocalcite (SMOW) ‰ and δ13Ccalcite (PDB) ‰ compositions of banded travertines from the inside to the outside are in the ranges of 16.5‰ to 17.4‰ and 7.3‰ to 8.7‰, respectively. The increase in the heavy isotope compositions in the inside of the banded travertine indicated that the water temperature decreased 3.61 °C from the inside to the outside in the banded travertine.

The slight downslope increase in the δ18O water

622

KALENDER et al. / Turkish J Earth Sci

Tabl

e 5.

Ba,

Sr,

As,

Mn,

Cu,

Pb,

Zn,

Co,

and

Sb

conc

entr

atio

ns o

f the

rmal

wat

ers,

trav

ertin

es, a

nd a

lgae

(con

cent

ratio

ns o

f the

ele

men

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KALENDER et al. / Turkish J Earth Sci

values is attributed to progressive evaporation (Fouke et al., 2000) and a decrease in water temperature. The downslope increase in the δ13C of travertine is linked to the amount of CO2 degassing (Kele et al., 2011). According to Pentecost (1995b), in Europe (Italy and Turkey), stable isotope compositions of the thermogene and meteogene deposits are variable, but the travertines tend to be slightly enriched in 13C (δ 13C from –2‰ to 10‰), except for the Karakoçan-Yoğunağaç and Mazgirt-Dedebağ travertines.1) The Mazgirt (T1-T3) and Karakoçan (T6-T9)

travertines might have been isotopically enriched due to seasonal changes. Travertines might have been isotopically enriched with overland flow during the summer or depleted with snowmelt during the spring.

2) The carbonate dissolved from the Permo-Triassic limestone of the Keban Metamorphic Formation or from the Quaternary travertine within the channel might have been reincorporated into downstream travertine, where it skewed the δ18O calcite and muted the overall signal. Because the Keban Metamorphic carbonates reach up to δ 18O 27.3 (SMOW) ‰ (Kalender, 2011), compared to the Quaternary travertine, the dissolved carbonate from these rocks could effectively increase the δ18O calcite within the rich layer, thereby reducing the intralayer range in δ18Ocalcite.

3) Dissolution/reprecipitation might have occurred across the couplet boundaries, thereby dampening the isotopic signal. Enrichment in the δ18O values was observed, possibly related to diagenetic processes in the banded travertine (Love and Chafetz, 1988; Janssen et al., 1999; O’Brien, 2006).

In this study, the travertines of the Karakoçan and Mazgirt areas were studied; the results indicated that the physical parameters and the chemical composition of the thermal waters, the host rock lithology, the structural geology, and the morphological features played important roles on the travertine deposition and the chemical composition.

In the study field, the algae species of Cyanophyta (blue/green algae), Chlorophyceae (green algae), and Bacillariophyta were determined. The algae species Oscillatoria is dominant in the studied thermal waters; this algae species is found as superficial mats on the travertines and is common in sulfide-rich thermal waters (Pentecost, 2005).

The As concentrations in thermal waters increase because of the high solubility of As at high temperatures (Table 1). However, it is thought that the As content in the algae could be related to the algae species due to metal absorption by organisms. Phormidium laminasum was found only at the T9 location (Table 4) in this study. Table 5 indicates that As, Ba, Cu, Pb, and Sb in algae at the T9 location are at the highest concentrations of all of the areas considered due to the S-tolerance of Phormidium laminasum (Pentecost and Tortora, 1989).

7. Conclusion 1) Tectonic activity significantly controls the travertine

deposition at the regional and local scales in Karakoçan and Mazgirt.

2) As, Sb, Sr, B, and Hg concentrations in the thermal waters have a positive relationship with temperature, pH, and alkalinity.

T1 T2 T3 T4 T5 T6 T7 T8 T9

As (ppb) in thermal waters 2332 2207 2248 1091 84 4893 2769 3186 5933

As (ppm) in travertines 478.7 104.6 45.9 5271 372.5 10000 148 7192 1180

T C 37.5 38 38 17.2 24.5 26.9 44 44.4 28.8

1

10

100

1000

10000

100000

log

valu

es

0

Figure 10. The diagram shows relationship between As concentrations in the travertines and thermal waters and temperature values of thermal waters.

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3) The present study points out that the ridge-type travertines are characterized with high As concentrations that are formed by the thermal waters with temperatures from 17 to 44 °C in the studied area. It is indicated that As concentrations of the thermal waters may be controlled by the deposition type, morphological characterizations, and age of the travertines, and also the dissolution speed of As-containing Fe and S minerals.

4) The stable carbon (δ13C) and oxygen (δ18O) compositions of the travertine deposits range from 3‰ to 11‰ PDB and from 15.2‰ to 27.2‰ SMOW, respectively. The water temperature, fracture zones, organic input with depth, and regional lithological characterizations may affect the δ13C and δ18O compositions.

5) The negative calcite saturation index (–0.4) and δ13C ‰ DIC (–0.4) indicate that the mixing process is an important factor for the metal concentrations of both thermal water and travertine (δ18O 17.3‰) chemistry.

6) The trace element and stable isotope geochemistry shows that the studied travertines could be grouped into three types (terrace, ridge, and banded-type travertines). It is thought that the high stable isotope composition of the travertines might be related to the ancient travertines and ridge-type travertines.

7) The estimated δ18OH2O isotope composition values indicate the changing of the geological time scale

with an exchange ratio of 12‰ where the travertine formation temperature decreased approximately 17 °C from ancient times to modern.

8) The metal contents of the banded travertines in the studied area were determined to change with the seasonal water temperature linking to host-rock composition. The increasing in the heavy isotope compositions in the inside of the banded travertine also indicated that the water temperature decreased 3.61 °C from the inside to the outside in the banded travertine. The studied travertines may be isotopically enriched with overland flow during the summer or depleted with snowmelt during the spring.

9) Algae species of Cyanophyta (blue/green algae), Chlorophyceae (green algae), and Bacillariophyta were determined in the travertines within the present study. In addition to the previous algae species, Oscillatoria and Phormidium laminasum were also determined in the studied travertines, which are common in sulfide-rich thermal waters due to their S tolerance.

AcknowledgmentsThe authors would like to thank the Scientific and Technological Research Council of Turkey (TÜBİTAK) for research support (Project number 106Y150). We also would like to thank the editors Dr  Fuat Yavuz and Dr Ömer Işık Ece and the reviewers for all their support.

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