Alteration mineralogy, lithochemistry and stable

Ore Geology Reviews 66 (2015) 219–242

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Alteration mineralogy, lithochemistry and stable isotope geochemistry of the Murgul (Artvin, NE Turkey) volcanic hosted massive sulfide deposit: Implications for the alteration age and ore forming fluids Emel Abdioğlu a,⁎, Mehmet Arslan a, Selahattin Kadir b, İrfan Temizel a a b

Department of Geological Engineering, Karadeniz Technical University, TR-61080 Trabzon, Turkey Department of Geological Engineering, Eskişehir Osmangazi University, TR-26480 Eskişehir, Turkey

a r t i c l e

i n f o

Article history: Received 14 March 2014 Received in revised form 16 October 2014 Accepted 19 October 2014 Available online 30 October 2014 Keywords: Late Cretaceous volcanics Hydrothermal alteration Mineralogy Geochemistry Eastern Pontides Murgul massive sulfide deposit

a b s t r a c t The Murgul (Artvin, NE Turkey) massive sulfide deposit is hosted dominantly by Late Cretaceous calc-alkaline to transitional felsic volcanics. The footwall rocks are represented by dacitic flows and pyroclastics, whereas the hanging wall rocks consist of epiclastic rocks, chemical exhalative rocks, gypsum-bearing vitric tuff, purple vitric tuff and dacitic flows. Multi-element variation diagrams of the hanging wall and footwall rocks exhibit similar patterns with considerable enrichment in K, Rb and Ba and depletion in Nb, Sr, Ti and P. The chondritenormalized rare earth element (REEs) patterns of all the rocks are characterized by pronounced positive/negative Eu anomalies as a result of different degrees of hydrothermal alteration and the semi-protected effects of plagioclase fractionation. Mineralogical results suggest illite, illite/smectite + chlorite ± kaolinite and chlorite in the footwall rocks and illite ± smectite ± kaolinite and chlorite ± illite in the hanging wall rocks. Overall, the alteration pattern is represented by silica, sericite, chlorite and chlorite–carbonate–epidote–sericite and quartz/albite zones. Increments of Ishikawa alteration indexes, resulting from gains in K2O and losses in Na2O and the chlorite–carbonate–pyrite index towards to the center of the stringer zone, indicate the inner parts of the alteration zones. Calculations of the changes in the chemical mass imply a general volume increase in the footwall rocks. Abnormal volume increases are explained by silica and iron enrichments and a total depletion of alkalis in silica zone. Relative K increments are linked to the sericitization of plagioclase and glass shards and the formation of illite/smectite in the sericite zone. In addition, Fe enrichment is always met by pyrite formation accompanied by quartz and chlorite. Illite is favored over chlorite, smectite and kaolinite in the central part of the ore body due to the increase in the (Al + K)/(Na + Ca) ratio. Although the REEs were enriched in the silicification zone, light REEs show depletion in the silicification zone and enrichment in the other zones in contrast to the heavy REEs' behavior. Hydrothermal alteration within the hanging wall rocks, apart from the gypsum-bearing vitric tuffs, is primarily controlled by chloritization with proportional Fe and Mg enrichments and sericitization. The δ18O and δD values of clay minerals systematically change with increasing formation temperature from 6.6 to 8.7‰ and −42 to −50‰ for illites, and 8.6 and −52‰ for chlorite, respectively. The O- and H-stable isotopic data imply that hydrothermal-alteration processes occurred at 253–332 °C for illites and 136 °C for chlorite with a temperature decrease outward from the center of the deposit. The positive δ34S values (20.3 to 20.4‰) for gypsum suggest contributions from seawater sulfate reduced by Fe-oxide/-hydroxide phases within altered volcanic units. Thus, the hydrothermal alteration possibly formed via a dissolution–precipitation mechanism that operated under acidic conditions. The K–Ar dating (73–62 Ma) of the illites indicates an illitization process from the Maastrichtian to Early Danian period. © 2014 Elsevier B.V. All rights reserved.

1. Introduction Volcanic-hosted massive sulfide (VHMS) deposits develop primarily in subaqueous rift-related environments (e.g., oceanic, fore-arc, arc, back-arc, continental margin, or continental) and are accompanied ⁎ Corresponding author. Tel.: +90 462 377 27 48. E-mail address: [email protected] (E. Abdioğlu).

http://dx.doi.org/10.1016/j.oregeorev.2014.10.017 0169-1368/© 2014 Elsevier B.V. All rights reserved.

primarily by bimodal, mafic–felsic volcanic successions, (e.g., Hart et al., 2004). The Eastern Pontides a paleo-island arc volcanic setting (Fig. 1a), is located in the Tethyan-Eurasia metallogenic belt extending from eastern Europe to the middle Asia-Pacific region and containing economically important VHMS deposits hosted by Upper Cretaceous age felsic volcanics (Abdioğlu and Arslan, 2009; Çağatay, 1993; Çağatay and Boyle, 1977; Eyüboğlu et al., 2014; Leitch, 1981; Pejatoviç, 1979; Schneider et al., 1988; Tüysüz, 2000). These VHMS deposits (Fig. 1b)

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E. Abdioğlu et al. / Ore Geology Reviews 66 (2015) 219–242

Fig. 1. (a) The inset map shows the tectonic units of Turkey (Okay and Tüysüz, 1999). (b) The simplified geological map of the Eastern Pontides, showing the distribution of the studied Murgul (Artvin) and other significant massive sulfide deposits. Modified from Arslan et al., 2013; Güven, 1993.

have features similar to the Kuroko type deposits in Japan and commonly occur within intensely altered felsic volcanics (Akçay and Moon, 2001; Antonović et al., 1996; Barbieri et al., 2000; Barrett and MacLean, 1999; Çağatay, 1993; Leitch, 1981; Sato, 1977; Urabe and Marumo, 1991), although recently they have been described as Eastern Black Sea-type (Eyüboğlu et al., 2014). The mineralogy and lithochemistry of the hydrothermally altered volcanics have been widely utilized to define hydrothermal alteration haloes of VHMS deposits (Akçay and Moon, 2001; Almodóvar et al., 1998; Barrett et al., 1993a,b, 1996; Barriga and Fyfe, 1988; Bryndzia et al., 1983; Çağatay, 1993; Çağatay and Eastoe, 1995; Gibson et al., 1999; Large, 1992; Leistel et al., 1998; Lentz and Goodfellow, 1996; MacLean and Kranidiotis, 1987; Ohmoto, 1996; Paulick and McPhie, 1999; Paulick et al., 2001; Peter and Goodfellow, 1996; Sánchez-España et al., 2000; Shikazono et al., 1995; Urabe et al., 1983). The actively mined Murgul (Artvin, NE Turkey) massive sulfide deposit is one of the largest VHMS deposits in Turkey and is located approximately 7 km south of the town of Murgul (Artvin) (Fig. 1b). Although the lithochemistry of the hanging wall and footwall rocks and the ore mineralogy of the Murgul deposit have been studied in detail (e.g., Çağatay, 1993; Schneider et al., 1988; Sipahi et al., 2014; Tüysüz, 2000), unanswered questions remain about the lithochemistry

and mineralogy of the hydrothermally altered rocks and the age of the alteration to illustrate the hydrothermal alteration types and patterns. Thus, this study has been carried out as an attempt to scrutinize the alteration mineralogy and chemistry of the Murgul VHMS deposit by means of X-ray diffraction, scanning electron microscopy, whole rock and oxygen-, deuterium-, and sulfur-isotope geochemistry data and the K–Ar dating of clays. 2. Regional setting The Eastern Pontides in NE Turkey represents an east–west trending Late Mesozoic–Early Tertiary magmatic belt and is considered a continental arc that developed in response to the subduction of the northern branch of the Neo-Tethyan oceanic crust beneath the Eurasian plate (e.g., Dixon and Pereira, 1974; Okay and Şahintürk, 1997; Şengör and Yılmaz, 1981). The polarity and time of the subduction and the evolution of the magmatic arc crust are still under debate (e.g., Bektaş, 1987; Boztuğ et al., 2004, 2006, 2007; Şengör and Yılmaz, 1981), but it has been already accepted that a collision between the Tauride– Anatolide Platform and the Eurasian Plate and the closure of the NeoTethyan Ocean, caused a continent–continent collision during the Late Cretaceous to Early Eocene (Arslan et al., 2013; Okay and Şahintürk,


1997; Temizel et al., 2012). The basement of the Eastern Pontides is represented by Devonian–Carboniferous metamorphic rocks that are intruded by Permo-Carboniferous plutons (Dokuz, 2011; Kaygusuz et al., 2012; Okay and Şahintürk, 1997; Topuz et al., 2010). The basement is unconformably overlain by Early and Middle Jurassic volcanics and volcaniclastics (e.g., Arslan et al., 1997). The Jurassic volcanics and volcaniclastics are conformably overlain by the Malm-Lower Cretaceous limestones that consist of neritic, pelagic, and sandy limestones (Okay and Şahintürk, 1997). During the Early Jurassic and Late Cretaceous, the region experienced successive volcanic activities related to the initiation of a magmatic arc (e.g., Arslan et al., 1997). The Late Cretaceous series that unconformably overlie the Malm-Lower Cretaceous carbonate rocks consist of sedimentary rocks in the southern part of the region and volcanics in the northern part (Güven, 1993). These rocks are overlain by the Eocene volcanics and volcaniclastics (Arslan et al., 1997, 2013; Güven, 1993). From Paleocene to Early Eocene, the Eastern Pontides

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was above sea level and experienced minor volcanism and terrigenous sedimentation (Okay and Şahintürk, 1997). The magmatic activity in the Eastern Pontides comprises three main episodes, namely, the Jurassic, Late Cretaceous, and Tertiary periods. The Jurassic volcanics are tholeiitic to calc-alkaline in composition, which formed within an extensional regime that is possibly related to rifting in a volcanic arc setting immediately prior to the subduction of the Neo-Tethyan oceanic crust (e.g., Arslan et al., 1997; Şen, 2007). The Late Cretaceous volcanics mainly belong to the tholeiitic series and calc-alkaline series, which exhibit typical arc characteristics (e.g., Arslan et al., 1997; Çamur et al., 1996; Sipahi et al., 2014). The Late Cretaceous volcanics and volcaniclastics are intruded by I-type, medium-/high-K calc-alkaline to shoshonitic granitoids of similar ages (e.g., Kaygusuz et al., 2013, 2014). The Tertiary activities are post-collisional and mainly represented by minor Miocene alkaline (e.g., Arslan et al., 1997; Aslan et al., 2013; Şen et al., 1998; Temizel

Fig. 2. Geological map of the Murgul mine (Artvin, NE Turkey) and surrounding areas. Modified from Er et al., 1992.

Chloritization, epidotization and argillization

Silicification, sericitization, chloritization, carbonatization

Dense silicification and partial hematitization

Partial silicification

Gypsum formation, pyritization, sericitization and kaolinitization of pumice fragments

Alteration

Dense hematitization, chloritization and local kaolinization


Sericitization, epidotization, chloritazion and carbonatization

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and Arslan, 2009; Temizel et al., 2012; Yücel, 2013) and extensive Middle Eocene calc-alkaline volcanism (e.g., Arslan and Aliyazıcıoğlu, 2001; Arslan et al., 1997, 2013; Aslan et al., 2013; Aydınçakır and Şen, 2013; Kaygusuz et al., 2011; Temizel and Arslan, 2008, 2009; Temizel et al., 2012; Yücel, 2013). The Middle Eocene volcanics and volcaniclastics are intruded by calc-alkaline granitoids of similar ages (e.g., Arslan and Aslan, 2006). In the Eastern Pontides (Fig. 1a), the Late Cretaceous volcanics and volcaniclastics (namely, the Kızılkaya Formation; Güven, 1993) hosting the volcanogenic massive sulfide deposits (e.g., Murgul, Çayeli, Kutlular, Köprübaşı, Lahanos; Fig. 1b) begin with early mafic rock and felsic rocks series, followed by late mafic–felsic rocks consisting of basalts, dacites and pyroclastics and locally interbedded with sedimentary layers (e.g., Arslan et al., 1997; Çamur et al., 1996; Sipahi et al., 2014; Tokel, 1977). The studied Murgul massive sulfide deposit is located in the intra-arc rift zone of the orogenic belt (Fig. 1b) and is surrounded mainly by a thick sequence of Late Cretaceous mafic–felsic volcanics and volcaniclastics with minor intercalations and lenses of marine sediments (Fig. 2).

Lahars — from angled to sub-rounded andesite, dacite, mudstone, granite and basalt gravels

Pumice fragments, glass shards, lithic fragments (mainly dacitic in composition), quartz (primary and secondary), plagioclase, sericite, chlorite, calcite, siderite. Dacitic lava flows, dacitic breccia Dacitic tuff (mainly pumiceous)

Quartz bearing andesite and pyroclastics

Footwall rocks

Lower mafic rocks

Chert

Epiclastic rocks

Mudstone, limestone

Gypsum bearing vitric tuff

Purple vitric tuff

Quartz, plagioclase, biotite, opaque, glass Dacitic flows (columnar jointed) Hanging wall rocks

Components Rock type

Andesitic flows and pyroclastics, locally dacite flows and pyroclastics with shallow marine sedimentary rocks Upper mafic–felsic rocks

Table 1 Mineralogical composition and alteration features of the Late Cretaceous upper mafic-felsic, hanging wall, footwall and lower mafic rocks from the Murgul mine.

3. Analytical techniques Eighty samples of felsic rocks from the Murgul area were selected for optical microscope, X-ray diffraction (XRD), and lithochemical studies. The optical microscope studies were done on lavas, pyroclastics and partly altered rocks. The selected samples for the XRD and lithochemical analyses were ground using an agate mortar and pestle. Clay fractions (b 2 μm) were obtained by using chemical treatments (Jackson, 1956; Kunze, 1965; Mehra and Jackson, 1960) to remove carbonates, amorphous silica and free Fe oxides, followed by the sedimentation and centrifugation of the suspension after overnight dispersion in distilled water. The dispersion of clay particles was completed by ultrasonic treatment for ~ 15 min. The XRD analyses were achieved by using a Rigaku DMAX 2200 and a Rigaku DMAXIIC X-ray diffractometers (Cu-Kα and Ni filter) at the laboratory of the General Directorate of Mineral Research and Exploration of Turkey (Ankara). The oriented clay fractions were subject to analysis under the untreated state (N), after ethylene glycolation (EG; 60 °C, 2 h) and heated conditions (H; 300 and 550 °C). Semi-quantitative abundances of rock-forming minerals were obtained using Brindley's (1980) external standard method. In addition, the relative abundances of the clay-minerals were obtained by using their basal reflections and the mineral intensity factors described by Moore and Reynolds (1997). Mineral abbreviations were used following Whitney and Evans (2010). Whole rock samples from the footwall and hanging wall volcanics were analyzed for major, trace and rare earth elements (REEs). The major and trace element analyses were carried out with a inductively coupled plasma-atomic emission spectrometer (ICP-AES) from pulp after 0.2 g of rock powder was fused with 1.5 g LiBO2 and then dissolved in 100 ml of 5% HNO3, and the REEs by inductively coupled plasma-mass spectrometry (ICP-MS) after 0.25 g rock powder was dissolved during multiple acid digestion steps at ACME Analytical Laboratories Ltd. (Canada) Loss on ignition (LOI) was determined based on the weight difference after the ignition of samples at ~1000 °C. The detection limits range from 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 REEs. The O-, H- and S-isotopic compositions of the samples were made at Activation Laboratories Ltd. (Actlabs) in Canada. Three illite, 1 chlorite and 2 gypsum samples were analyzed for their H and O isotopic compositions. The H isotopic analyses, made by conventional isotope-ratio mass spectrometry, are reported in the familiar notation in per mil relative to the V-SMOW standard. The procedure described above was used to measure a δD value of −65‰ for the NSB-30 biotite standard. The O isotopic analyses were performed on a Finnigan MAT Delta, dual inlet, isotope-ratio mass spectrometer, following the procedures of Clayton and Mayeda (1963). The data are reported in the standard


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Fig. 3. Field photographs of the Murgul mine (a) the Çakmakkaya and (b) the Damar open pits. The hanging wall rocks, in this case columnar jointed dacites, directly sit on the footwall dacitic tuffs. (c) Gypsum-bearing vitric tuff converted mainly to illite. (d) Euhedral pyrite grains showing a combination of cubic and pyritohedral forms surrounded by argillized particles of volcanic ash. Micrographs of variable degrees of hydrothermal alteration in the hanging wall dacites. (e) and (f) Epidote, sericite and carbonite replacement of plagioclase and chlorite formation in the groundmass and biotite. (g) Euhedral to subhedral quartz grains embedded in a flow textured groundmass with dense carbonate alteration. (h) Carbonite replacement of plagioclase with subhedral quartz grains (hw, hanging wall; fw, footwall rocks; Gp, gypsum; Ilt, illite; Py, pyrite; Bt, biotite; Cal, calcite; Chl, chlorite; Epd, epidote; Ser, sericite; Pl, plagioclase; Q, quartz).

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Fig. 4. Macroscopic views of the footwall rocks and commonly observed alteration zones from the Murgul mine: (a) Chalcopyrite vein in highly silicified dacitic tuff; (b) hydrothermal breccias with chalcopyrite and pyrite veins; (c) highly silicified dacitic tuff cut by a vein consisting of siderite, quartz, pyrite, chalcopyrite and bornite; (d) dense argillic and local iron oxide leached zones in dacitic tuff; (e) dense silicification of dacitic tuff with iron oxide leached zones; (f) chalcanthite as a secondary oxidation product (Arg, argillic alteration; Bn, bornite; Ccp, chalcopyrite; Ch, chalcanthite; He, hematitization; Py, pyrite; Si, silicification; Sd, siderite; Qz, quartz).

delta notation as per mil deviations from V-SMOW. The external reproducibility is ±0.19‰ (1σ) based on repeated analyses of the internal white crystal standard (WCS). The NBS 28 value is 9.61 ± 0.10‰ (1σ). Two gypsum samples were analyzed for δ34S isotopic composition. The gypsum samples were combusted to SO2 gas under ~10−3 Torr of vacuum. The SO2 is inlet directly from the vacuum line to the ion source of a VG 602 Isotope Ratio Mass Spectrometer (Ueda and Krouse, 1986). Quantitative combustion to SO2 is achieved by mixing 5 mg of sample with 100 mg of a V2O5 and SiO2 mixture (1:1). The reaction is carried out at 950 °C for 7 min in a quartz glass reaction tube. Pure copper turnings are used as a catalyst to ensure the conversion of SO3 to SO2. Internal Lab Standards (SeaWaterBaSO4 and FisherBaSO4) are run at the beginning and end of each set of samples (typically 25) to normalize the data and correct for any instrument drift. All the results are reported in the per mil notation relative to the international CDT standard.

Three pure illite samples were analyzed for K–Ar dating at Activation Laboratories Ltd. (Actlabs) in Canada. For Ar analysis, an aliquot of the sample was weighted into an Al container, loaded into the sample system of an extraction unit, and degassed at ~100 °C over 2 days to remove the surface gases. Argon is extracted from the sample in a double vacuum furnace at 1700 °C. The argon concentration is determined using isotope dilution with a 38Ar spike, which is introduced to the sample system prior to each extraction. The extracted gases are cleaned up in a two-step purification system. Then, pure Ar is introduced into the custom-build magnetic sector mass spectrometer (Reinolds type) with a Varian CH5 magnet. The ion source has an axial design (Baur-Signer source), which provides more than 90% transmission and extremely small isotopic mass-discrimination. Measurements of the Ar isotope ratios are corrected for mass-discrimination, and atmospheric argon is removed assuming that the 36Ar is only from the air. The


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Fig. 5. Micrographs of variable degrees of hydrothermal alteration in footwall dacitic tuffs from the Murgul mine: (a) and (b) the quartz altered pumice fragments and fine-grained opaques-clay mixture in the matrix, (c) spheluritic texture (Sph) formed by quartz and K-feldspar, (d) quartz-K-feldspar-carbonate alteration with quartz-kaolinite veinlets, (e) quartz-chlorite alteration, (f) quartz-sericite alteration, (g) silicification accompanied by barite and opaques, h) siderite and opaques in veins of the highly silicified tuffs (Brt, barite; Cb, carbonate; Chl, chlorite; Cl, clay minerals; Kln, kaolinite; K feld, K-feldspar; Opq, opaques; Pm, pumice fragments; Sd, siderite; Ser, sericite; Q, quartz).

concentration of radiogenic 40Ar is calculated by using the 38Ar spike concentration. After each analysis, the extraction temperature is elevated to 1800 °C for a few minutes and the furnace is prepared for the next analysis. For K-analysis, an aliquot of the sample is weighted into a

graphite crucible with a lithium metaborate/tetraborate flux and fussed using an LECO induction furnace. The fusion bead is dissolved with acid. The standards, blanks and samples are analyzed on a Thermo Jarrell Ash Enviro II ICP Spectrometer.

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Fig. 6. XRD patterns of oriented clay fractions (b2 μm) from the Murgul mine under untreated (UN), ethylen glycolated (EG), 300 °C (H(300)) and 550 °C (H(550)) conditions (Ilt, illite; Chl, chlorite; Kln, kaolinite; Sme; Smectite; Q , quartz).

4. Results 4.1. Volcanic stratigraphy and facies The Murgul mine (Artvin, NE Turkey) has been discontinuously mined and is surrounded by Upper Cretaceous aged hydrothermally altered mafic–felsic volcanics intercalated with marine sediment and represented by three volcanic rock groups lower mafic rocks, mainly felsic rocks (host rock of the massive sulfide deposit) and upper mafic rocks (Fig. 2 and Table 1). In the study area, the lower mafic rocks are

represented by quartz-bearing andesite and pyroclastics, and the upper mafic–felsic rocks consist of andesite, dacite and their pyroclastics with sedimentary units. These rocks are unconformably covered by Upper Cretaceous–Paleocene aged limestone and marl and Eocene aged basalt–andesite and their pyroclastics (e.g., Arslan et al., 2013; Aydınçakır and Şen, 2013), which are cut by the Eocene granitic intrusions (e.g, Arslan and Aslan, 2006). Host rocks of the ore body can be divided into two main groups as the footwall comprising of the dacitic flows, breccias and tuffs; hanging wall consisting of the dacitic flows, epiclastic rocks, cherts, mudstones,


limestones, gypsum-bearing vitric tuffs interbedded with an accretionary lapilli tuff and purple vitric tuffs (Fig. 2 and Table 1). The Murgul deposit is mainly mined in three ore bodies named as Damar, Çakmakkaya and Bognari which was transported while the others were in situ (Tüysüz, 2000). 4.1.1. Hanging wall rocks The hanging wall rocks of the massive sulfide lens are partly porphyritic dacitic lava flows, a thin sedimentary unit beginning with mudstonelimestone-tuff and gypsum-bearing vitric tuff (Figs. 2 and 3a-d; Table 1). The dacitic flows (purple dacite or columnar jointed dacites) are characterized by their purple alteration color, but green color in the fresh surfaces that have columnar jointing (Fig. 3a and b). In the region, these hanging wall dacitic flows directly overlie the footwall dacitic flows and pyroclastics (Fig. 3a and b). In hand specimen, they show porphyritic texture with visible quartz, plagioclase and occasional biotite. Additionally, local silicification and argillization are observed. Plagioclase, quartz and biotite phenocrysts are embedded in a fine grained matrix of similar components and/or glass. Plagioclase phenocrysts are generally altered to epidote, sericite, carbonate and even chlorite. Chloritization is also determined in the groundmass and from biotite flakes (Fig. 3e and f). The degree of carbonate alteration increases away from the ore horizon and is represented by the carbonate replacement of plagioclase and the glassy matrix (Fig. 3g and h). The sedimentary and pyroclastic units consist of vitric-lapilli accretionary tuff, mudstone, chert and limestone. The cherts, mudstones and limestones are highly silicified and locally hematized and underlie gypsum-bearing vitric tuff that contains gypsum lenses (Fig. 3c) and pyrite, showing a well-developed lamination. The gypsum-bearing vitric tuff is intercalated with lapilli accretionary tuff, is mainly argillized and contains a combination of cubic and pyritohedral euhedral pyrite grains (Fig. 3d). 4.1.2. Footwall rocks The footwall rocks are mainly pumiceous tuffs and breccias with dacitic flows varying from 200 to 250 m in thickness and generally covered directly by hanging wall units (see Fig. 3a and b). The ore body is present mainly within pumiceous tuffs, generally massive, partly stockwork and disseminated (Fig. 4a and b), formed by yellow ore, black ore and supergene associations, and consists of sphalerite, galena, pyrite, chalcopyrite, tetrahedrite, bismuth, bismuthite, digenite, covelline, malachite and azurite. The deposit has the characteristics of both Cu-pyrite and Cu–Zn types of volcanogenic massive sulfide mineral systems and is classified mainly as stratabound (Çiftçi et al., 2001). The ore textures within the ore body are disseminations, brecciation, veins and veinlets, replacement and atoll-type texture (Çiftçi et al., 2001). The dacitic flows at the base of the footwall unit gradually change to breccias and tuffs. In hand specimen, the color of the footwall rocks changes from white, grey, and red to beige, linked to the degree and type of hydrothermal alteration (Fig. 4). Silicification and/or surficial hematitization are common alteration types around the ore body. The footwall rocks are locally cut by veinlets consisting of quartz, siderite, chalcopyrite, pyrite and bornite (Fig. 4c). Away from the ore horizon, dense argillic and local iron oxide leached zones are recognized (Fig. 4d and e). Chalcanthite is always present as a secondary oxidation product (Fig. 4f). In thin section, quartz, plagioclase, glass fragments and opaque minerals are the main components of the footwall pumiceous tuffs. Elongated pumice fragments are generally converted to quartz with the other glassy material replaced by a mixture of opaques and clays (Fig. 5a and b). Spherulitic texture resulting from devitrification with quartz-K-feldspar is also identified (Fig. 5c), and the veins are filled with cryptocrystalline quartz and kaolinite (Fig. 5d). Based on the extent of silicification, the original texture of the rocks is completely destroyed. Chloritization and sericitization are partially accompanied by silicification (Fig. 5e and f). Barite is associated with silicification

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(Fig. 5g). Disseminated opaques (probably pyrite) are always present. Rare carbonate formation (calcite and dolomite) is locally present (Fig. 5d), whereas carbonate veins (siderite) probably of a later stage epigenetic origin have been identified (Fig. 5h).

Table 2 Mineralogical composition (wt%) based on the XRD data of the clay fractions (b2 μm) from the footwall and hanging wall rocks from the Murgul mine (DP, MD and MDA indicate Damar; CAP and MC imply Çakmakkaya open pits). Sample no.

Ilt

Chl

Kln

Sme

Ilt/Sme

DP1-3 DP1-4 DP1-5 DP1-7 DP1-8 DP1-10 DP1-11 DP1-12 DP1-13 DP1-14 DP1-16 DP1-17A DP1-18 DP1-19 DP1-20 DP1-21 DP1-22 DP1-23A DP1-23B DP2-1 DP2-2 DP2-4 DP2-5 DP2-6 DP2-7 DP2-8 MD-2 MD-5 MD-10 MD-11 MD-12 MDA-16 MDA-19 MDA-20 MDA-21 MDA-22 MDA-23 MDA-24 MDA-27 MDA-29 MDA-18 MDA-28 MBG-1 MBG-4 MBG-6 MBG-11 MBG-26 CAP 1-1 CAP1-2 CAP1-3 CAP1-4 CAP1-5 CAP1-6 CAP1-7 CAP1-8 CAP1-9 CAP1-10 CAP1-11 CAP1-12 CAP1-15fr CAP1-15alt MC-9 MC-9 MC-17 MC-19 MC-20

67 32 79 0 94 90 84 30 77 90 75 100 78 0 0 0 0 33 0 0 90 100 100 100 100 86 100 0 100 100 100 34 61 100 47 42 0 68 0 0 68 0 100 100 82 87 100 81 75 92 100 43 86 100 100 100 100 85 67 61 70 100 100 78 100 43

0 0 0 44 0 0 16 0 23 10 25 0 0 46 33 0 100 67 39 57 0 0 0 0 0 0 0 40 0 0 0 29 39 0 53 58 15 32 22 87 32 0 0 0 18 13 0 19 25 8 0 0 14 0 0 0 0 15 33 39 30 0 0 22 0 57

33 22 21 0 6 10 0 70 0 0 0 0 22 0 0 0 0 0 0 0 10 0 0 0 0 14 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 43 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 46 0 56 0 0 0 0 0 0 0 0 0 54 67 100 0 0 61 0 0 0 0 0 0 0 0 60 0 0 0 37 0 0 0 0 85 0 78 13 0 76 0 0 0 0 0 0 0 0 0 47 0 0 0 0 0 0 0 0 0 0 0 0 0 0

228


4.2. Clay mineralogy All the footwall and hanging wall volcanics were subject to intense and varying degrees of hydrothermal alteration. The clay mineralogy of the altered volcanics was described in detail by XRD studies along the lateral profiles in the Çakmakkaya and Damar areas from the inner stockwork ore zone towards the outer zones of the footwall rocks. The term illite was used instead of sericite due to the reports that the roentgenographically determined illite corresponds to optically determined sericite in these types of rocks (e.g. Środoń and Eberl, 1984). Illite was identified by reflections at 10.0 and 5.0 Ǻ, is not affected by the ethylene-glycol treatment and undergoes a slight reduction

following heating to 550 °C due to dehydroxylation. Kaolinite has peaks at 7.16–7.2 and 3.58–3.59 Å, and chlorite has a peak at 14.12 Å. The presence of mixed-layer illite–smectite minerals is inferred from the width of the 17 Å peak (ethylene glycol-solvated) and the lack of rational d spacing for the remaining basal reflections. Quartz was identified by peaks at 3.34 and 4.26 Å (Fig. 6). The Fe and Mg contents of the chlorites were inferred from the intensities of the 001, 003 and 005 peaks relative to the 002 and 004 reflections (e.g., Moore and Reynolds, 1997). In the footwall dacitic tuffs and breccias, clay mineral assemblages are identified as illite (Fig. 6a); illite/smectite + chlorite ± kaolinite (Fig. 6c and d); and chlorite (Fig. 6e and f). Abundant quartz-illite

Fig. 7. SEM images of the common clay mineral phases from the Murgul mine (Ilt, illite; Chl, chlorite; Kln, kaolinite; Sme, smectite; Gp, gypsum; Q, quartz).


229

a

alteration is recognized in the stockwork ores in the Damar and Çakmakkaya area. From the inner zone to outer zone, illite was converted to regular and irregular interstratified illite/smectite (Fig. 6a–d). Chlorite was accompanied by illite and illite/smectite. Mg chlorite was observed at the inner part of the alteration zone and was converted to Fe-chlorite towards the outer horizon (Fig. 6d–f). Kaolinite was determined at the outer zone associated with smectite and illite in the gypsum-bearing vitric tuff of the hanging wall rocks (Fig. 6b and Table 2). The clay mineralogy from the inner stockwork to the outer zone of the ore horizon comprises illite, chlorite, and smectite–kaolinite. The clay mineralogy changes outward from the ore body as follows: illite, illite/smectite, chlorite, and kaolinite associated with coarse grained euhedral pyrite and gypsum lens, and the occurrence of carbonate, albite and Fe-oxide/-hydroxide phases in the hanging wall and footwall rocks. The scanning electron micrographs of illite represent fibers and booklets with well-developed crystals (Fig. 7a, b, d and f) accompanied by chlorite booklets or euhedral and coarse grained idiomorphic kaolinite crystals having hexagonal outlines or occurring as irregular flakes (Fig. 7c and d). The illite/smectite shows thin, leaf-shaped habits forming a dense aggregate (Fig. 7e). The gypsum crystals exhibit blocky and elongated forms (Fig. 7f). In the EDX analysis, the illite and chlorite crystals yielded Si, Al, and K peaks. The peaks of Al and K in the illite are slightly stronger than those in the chlorite. The illite/smectite flakes produced Si, Al, and K peaks. The blocky gypsum gave strong peaks for S and Ca. The kaolinite plate gave nearly equally high peaks for Si and Al.

b

4.3. Lithochemistry of the volcanics The whole-rock major oxide analyses and the trace element and REE analyses of the hanging wall and footwall rocks are presented in Tables 3 and 4. The SiO2 contents of the samples differ from each other based on the degree and type of alteration, ranging from 68.24 to 69.14, 46.05 to 58.1 and 1.00 to 11.26 wt.% for the dacite, purple vitric tuff and gypsum-bearing vitric tuff of the hanging wall rocks, respectively. The SiO2 contents of the footwall pyroclastics mainly depend on the degree of silicification and ore formation, fluctuating between 27.94 and 95.03 wt.%. In the hydrothermal alteration environments, many of the major and trace elements for rock nomenclature cannot be used due to their mobile behavior (Hart et al., 1974; Jeans et al., 2000). The Zr/TiO2 versus Nb/Y immobile element plot of Winchester and Floyd (1977) revised by Pearce (1996) is efficiently used for the hydrothermally altered footwall and hanging wall rocks (Barrett and MacLean, 1994; Barrett et al., 1993a,b; Jenner, 1996; MacLean, 1990; MacLean and Kranidiotis, 1987; Shriver and MacLean, 1993). Petrochemically, most of the studied samples plot in the rhyolite/dacite field, consistent with their petrographic features, but few footwall and hanging wall rocks (purple vitric tuff) are plotted on the andesite/basalt field because intense argillic and carbonate alteration caused the depletion of the most immobile elements and silica (Fig. 8a). The geochemical affinities of the studied rocks were determined by using Zr versus Y and La versus Yb binary plots (Fig. 8b and c). In Fig. 8b and c, the majority of the samples are scattered between the calc-alkaline and transitional fields with a less common tholeiitic character. In the N-MORB (Sun and McDonough, 1989) normalized multi element spider diagrams (Fig. 9a–d), all the hanging wall rocks, apart from the gypsum-bearing vitric tuff due to its high gypsum but low silica content, and footwall rocks have similar patterns with considerable enrichment in large ion lithophile elements (LILEs; K, Rb, Ba) and depletion in Nb, Sr, Ti and P. The enrichment degree of Ba mainly depends on the barite content in the footwall rocks, and the abnormal enrichment of Sr in gypsum-bearing vitric tuff is linked with the gypsum content. The chondrite (Taylor and McLennan, 1985) normalized REE patterns of all the studied samples (Fig. 9e–h) are enriched in light REEs (LREEs) relative to heavy REEs (HREEs), which is common in felsic volcanics formed in

c

Fig. 8. (a) Chemical nomenclature plot by using the Nb/Y-Zr/TiO2*0.0001 immobile element diagram of Winchester and Floyd (1977) revised by Pearce (1996), (b) Y versus Zr and (c) Yb versus La geochemical affinity plots for the studied volcanics from the Murgul mine. The discrimination lines are from Ross and Bédard (2009).

an evolved island arc setting (Almodóvar et al., 1998). All the dacites, purple vitric tuffs and gypsum-bearing vitric tuffs in the hanging wall rocks display moderately fractionated chondrite-normalized REE patterns (LaN/LuN = 2.38–3.08, 4.44–10.39 and 5.41–12.97, respectively; Table 4). The footwall dacitic pyroclastic samples from the Çakmakkaya and the Damar open pits exhibit patterns parallel to each other (LaN/LuN = 1.44–18.31). The REE distributions of all the volcanic samples have concave patterns, which tend to flatten towards LREEs and HREEs and are pronounced by positive/negative Eu anomalies (EuN/EuN* = 0.32–1.43; Fig. 9e–h) explained by different degrees of hydrothermal alteration resulting from interactions with sulfide–sulfate ore forming fluids (Shikazono et al., 2008) and plagioclase fractionation (Fig. 9e–h). 4.4. Stable isotope geochemistry and K–Ar dating of clays In Table 7, the δ18O values of clay minerals decrease towards the ore horizon due to the effect of increasing formation temperature. The δ18O and δD values are 6.6 to 8.7‰ and − 42 to -50‰ for the illites and 8.6 and −52‰ for chlorite, respectively. The δ34S and δD values for gypsum

230

Table 3 Major (wt%) and trace element (ppm) compositions of the hanging wall and footwall rocks of the Murgul mine. CAP1-1

CAP1-2

CAP1-15al

CAP1.15fr

Columnar jointed dacite 68.24 13.69 3.86 1.34 2.75 2.71 3.47 0.4 0.1 0.06 0.002 3.4 0.51 b.d.l. 100.0 2.9 2 21 1.6 b.d.l. 2.6 170.7 0.7 0.1 30.6 132.4 5.7 91.3 102 0.3 4.3 0.8 14 0.2 4.3 23.2 19.0

68.58 13.89 4.06 1.51 2.67 3.93 1.73 0.38 0.09 0.06 0.002 3.1 0.53 b.d.l. 100 10.4 1.4 40 1.1 b.d.l. 1.6 237.8 0.6 0.1 32.8 144.2 5.7 29 92.6 0.3 3.6 1 13 0.2 4.4 25.3 19.0

69.14 14.57 4.41 1.3 2.43 2.99 1.87 0.38 0.09 0.06 0.002 2.6 0.06 b.d.l. 99.84 39.8 0.8 42 1.1 b.d.l. 3.6 195.7 0.8 b.d.l. 37.9 143.2 5.1 32.1 132.6 0.3 3.7 1.2 13 0.1 3.8 28.1 17.0

DP1-19

CAP1-9

Purple vitric tuff 68.46 13.99 4.17 1.3 3.25 2.9 2.08 0.38 0.09 0.06 0.002 3.3 0.49 b.d.l. 99.98 33.2 1 46 1.1 b.d.l. 1.6 212.6 0.6 0.1 32.4 137.4 5.2 41.4 116 0.4 3.9 1.3 14 0.2 4.2 26.4 13.0

46.91 12.01 8.81 4.54 8.95 0.51 2.13 0.65 0.11 0.18 b.d.l. 15.2 3.48 b.d.l. 100 3 12.7 35 2.1 1.6 0.8 219 0.3 0.3 25 95.8 6.3 63.6 147 0.3 1.7 0.4 20 0.3 3.8 15.2 21.0

58.1 19.2 3.7 5.01 2.35 0.65 1.09 0.27 0.04 0.03 b.d.l. 9.4 0.87 b.d.l. 99.85 1.3 2.1 91 b.d.l. b.d.l. 7.2 97.5 0.2 b.d.l. 23.4 138.4 10.1 20.2 108.6 0.8 11.3 3 9 0.4 5.9 13.7 12.6

46.05 16.61 8.93 4.31 7.34 2.56 1.36 1.04 0.34 0.14 0.002 11.1 2.68 0.01 99.78 99.8 4.8 78 1.6 b.d.l. 9.9 472.4 0.4 0.1 20.4 113.2 8.6 29.7 434.3 0.4 3.7 1.2 22 0.4 5.5 13.2 21.5

DP1-15

DP1-17

DP1-18

CAP1-3

CAP1-4

CAP1-5


Footwall dacitic pyroclastics

1.07 0.85 0.15 0.58 37.61 b.d.l. 0.05 0.02 b.d.l. b.d.l. b.d.l. 9.3 0.08 19.03 49.63 2.1 0.4 3 b.d.l. 2.8 0.1 21.1 0.2 b.d.l. 1.9 8.7 b.d.l. 0.5 1123.4 0.1 0.1 b.d.l. b.d.l. – 4.6 – –

77.63 9.44 2.84 2.24 0.13 0.07 1.97 0.2 0.06 0.03 0.003 5.4 0.73 0.52 100.01 13.9 7.7 49 4.5 8.5 1.6 218.8 3.4 0.1 20.5 98 4.6 34.2 48 0.3 3.2 0.9 6 0.2 4.8 21.3 15.3

1.00 0.3 0.17 0.08 33.66 b.d.l. 0.08 b.d.l. b.d.l. b.d.l. b.d.l. 20.7 0.04 16.52 55.99 11.4 0.4 5 b.d.l. b.d.l. 0.3 41.1 b.d.l. b.d.l. 0.1 1.6 b.d.l. 1.1 982.6 b.d.l. 0.1 b.d.l. b.d.l. – 16.0 – –

All Fe as Fe2O⁎3 ; LOI is loss on ignition. ∑C, total carbon; ∑S, total sulfur. b.d.l., below dedection limit.

11.26 3.18 0.4 0.21 28.08 b.d.l. 0.82 0.04 b.d.l. b.d.l. b.d.l. 21.9 0.04 14.32 65.9 36.6 2.5 9 1.9 b.d.l. 0.7 363.3 0.1 0.1 1.6 15.5 0.7 14.3 1016.2 0.1 0.6 0.4 b.d.l. 0.4 9.7 22.1 7.0

79.84 8.87 4.24 0.37 0.05 0.08 2.4 0.2 0.05 b.d.l. 0.004 3.9 0.03 2.7 100 5.8 3.5 3 5.8 7 2.7 313.8 3 0.1 21.9 96.4 4.6 40.4 47.5 0.3 2.8 1.2 6 0.2 4.4 21.0 15.3

84.17 6.53 2.98 0.27 0.01 0.05 1.68 0.16 0.02 b.d.l. 0.003 4 0.02 1.74 99.88 108.8 5.2 3 14 21.3 1.8 182.9 1.9 0.2 28.2 73.8 3.5 29.6 24.8 0.2 2.2 0.7 4 0.1 2.6 21.1 17.5

CAP1-7

CAP1-8

CAP1-11

CAP1-12

CAP1-13

CAP1-15

DP1-3

DP1-4

DP1-5

DP1-6

87.09 7.34 0.73 0.38 0.02 0.05 1.99 0.21 0.02 b.d.l. 0.001 2.2 0.01 0.01 100.03 13.1 0.6 4 0.5 2.7 1.3 224.6 1 0.1 21.7 99.3 4.9 36.2 22.5 0.3 2.7 1 5 0.2 4.6 20.3 16.3

81.13 11.8 0.26 0.26 0.03 0.17 2.56 0.29 b.d.l. b.d.l. b.d.l. 3.5 0.01 b.d.l. 100 11.4 0.7 1 0.5 b.d.l. 1.2 205.1 0.7 b.d.l. 31.1 131.4 5.4 43.5 39.6 0.3 3.9 1 6 0.2 4.2 24.3 18.0

87.00 4.69 2.76 0.36 0.04 0.04 1.23 0.12 0.03 0.01 0.003 3.6 0.05 1.46 99.88 84.9 3.9 26 79.2 29.3 3 135.9 5.5 0.7 11.8 58.3 2.7 22.7 14.5 0.1 1.2 1.2 3 0.2 4.9 21.6 27.0

92.49 0.96 2.68 0.23 0.03 0.02 0.16 0.02 0.01 0.01 0.004 2.7 0.13 1.48 99.31 3586.5 9 155 42.6 61.8 4 1919.5 21 1.8 2.1 8.7 b.d.l. 3.3 55.3 0.1 0.4 0.7 1 -! 4.1 -! -!

68.99 14.07 3.77 1.56 3.49 3.81 1.76 0.43 0.09 0.07 b.d.l. 1.8 14.87 b.d.l. 99.84 54.5 0.5 37 0.8 3.5 1.5 291 0.6 0.2 34.7 126.5 5.7 24.7 157.9 0.4 3.8 1.3 14 0.2 3.6 22.2 14.3

67.64 14.48 4.16 0.82 4.73 3.4 1.98 0.42 0.1 0.1 0.002 2 0.38 b.d.l. 99.83 52.6 1.5 44 1.8 2.3 1.3 273.8 0.6 0.1 35 122.4 5.1 32.7 172.8 0.3 4.1 1.1 15 0.1 3.5 24.0 17.0

75.73 13.97 0.48 0.73 0.02 0.13 3.78 0.34 0.05 b.d.l. b.d.l. 4.6 0.02 0.02 99.83 197.8 17 25 27.2 16.6 0.6 298.1 4.1 0.4 47 161 8.2 67.8 162.9 0.5 5 1.9 10 0.2 3.4 19.6 16.4

69.27 2.25 13.65 0.07 0.01 0.08 0.27 0.05 0.02 b.d.l. 0.003 9.2 0.02 11.66 94.87 4925.2 572.7 N10000 1916.9 566.4 2.9 26621 45 47.4 8.3 24.1 1.2 6.1 381.6 0.3 1 1.1 1 0.1 2.9 20.1 4.0

64.35 20.08 1.59 0.96 0.14 0.28 4.28 0.46 0.07 0.01 b.d.l. 7.5 0.04 0.32 99.73 276.6 49 206 31.5 17.3 0.8 705.9 0.9 b.d.l. 45.2 236.5 8.7 82.3 81.9 0.6 6.8 4.4 12 0.2 5.2 27.2 14.5

93.89 0.94 3.35 0.1 0.02 0.01 0.16 0.03 0.02 b.d.l. 0.003 1.5 0.03 0.08 100.02 103.6 8.5 2 34.1 370.4 2.3 242 25.2 13.6 1.6 9.9 0.5 4 4.6 b.d.l. 0.2 1.8 1 0.3 6.2 19.8 -


SiO2 Al2O3 Fe2O3* MgO CaO Na2O K2O TiO2 P2O5 MnO Cr2O3 LOI ∑C ∑S Total Cu Pb Zn As Au (ppb) Ni Ba Mo Sb Y Zr Nb Rb Sr Ta Th U Sc Nb/Y Zr/Y Zr/Nb Nb/Ta

DP1-17A

Table 3 (continued) DP1-7 DP1-8 DP1-10 DP1-12 DP1-13

DP1-14 DP1-16 DP1-18B DP1-20 DP1-21 DP1-22 DP1-23A DP1-23B DP2-1

DP2-6 DP2-4 DP2-7 DP2-8 CAP1-6 DP1-11 DP2-5

CAP1-10 DP2-2

DP1-9

79.31 9.94 2.52 1.06 0.14 0.06 2.48 0.19 0.05 0.02 b.d.l. 4.1 0.23 0.85 99.87 38.7 6.5 42 20.2 13.5 1.6 195.2 3.7 0.2 16.7 77 3.8 44.1 26.2 0.2 3 0.6 7 0.2 4.6 20.3 19.0

77.00 11.27 2.76 0.51 0.12 0.05 3.14 0.24 b.d.l. b.d.l. b.d.l. 4.8 0.03 1.82 99.9 341.5 18.6 77 113 44.6 1.9 651.8 11.6 0.3 18.7 119.4 5.6 55 20.7 0.3 5.2 2.8 8 0.3 6.4 21.3 18.7

85.58 4.93 4.18 0.33 0.17 0.05 1.36 0.12 0.03 b.d.l. 0.001 3.2 0.07 2.55 99.95 676.8 11.5 57 58.5 59.3 2.1 172.5 15.2 0.9 12.4 54.4 2.9 27.1 61.8 0.1 1.7 1.4 3 0.2 4.4 18.8 29.0

27.94 0.31 39.04 0.01 0.01 b.d.l. b.04 b.d.l. b.d.l. b.d.l. b.d.l. 16.6 0.05 28.02 83.94 N10000 649.3 759 567.5 344.6 3.4 127.3 28.9 12.2 0.2 0.8 b.d.l. b.d.l. 3.4 b.d.l. 0.2 b.d.l. b.d.l. – 4.0 – –

Footwall dacitic pyroclastics 82.74 7.19 1.93 0.24 0.04 0.04 1.64 0.16 0.02 b.d.l. b.d.l. 6 0.02 1.08 100 135.6 8.6 21 86.3 21.9 1.6 182 5.2 1.5 16.8 70.7 3.8 33.9 26 0.2 2 1.2 4 0.2 4.2 18.6 19.0

74.8 7.88 4.52 2.95 1.08 0.08 1.5 0.15 0.06 0.05 0.002 6.8 1.22 1.35 99.87 17.7 7.7 77 35 0.5 2.4 210.6 2.7 0.2 40.4 72.5 4.6 32.4 34.4 0.3 2.3 0.5 7 0.1 1.8 15.8 15.3

84.91 7.19 2.24 0.47 0.06 0.08 1.77 0.15 0.04 b.d.l. b.d.l. 2.7 0.04 1.22 99.62 393.3 28 1113 96.2 22.6 1.7 787.6 3.1 1.5 14.1 69.8 3.1 30.2 26.8 0.2 2.4 1 5 0.2 5.0 22.5 15.5

80.67 7.89 2.81 1.83 0.16 0.05 1.49 0.19 0.05 0.02 b.d.l. 4.7 0.55 0.49 99.86 7.2 7.3 90 34.7 21.7 0.9 249.2 1 0.4 22.7 84.4 4.4 27.9 73.1 0.4 3.1 1.3 6 0.2 3.7 19.2 11.0

85.73 4.45 2.96 0.7 0.05 0.04 0.93 0.11 0.03 0.01 0.004 2.9 0.2 1.51 97.91 192.8 459.5 2134 133.9 57 3.8 13314.6 5.7 3.1 12.7 47.3 2.3 18.4 219.7 0.3 1.5 0.9 3 0.2 3.7 20.6 7.7

70.6 15.24 1.2 1.35 1.77 0.05 3.69 0.11 b.d.l. 0.01 b.d.l. 5.8 0.07 1.25 99.82 6.9 1.6 14 1.5 2.7 0.7 607.4 1.8 b.d.l. 2.5 25.1 1.5 58.4 189.2 0.1 0.6 0.3 3 0.6 10.0 16.7 15.0

63.86 4.9 4.19 4.71 8.83 0.33 0.52 0.11 0.05 0.19 0.001 12.2 3.73 0.01 99.9 5.7 8.2 45 0.7 0.9 3.9 78.8 0.5 0.1 13.8 51.9 4.5 12.9 106.6 0.3 3.7 0.7 5 0.3 3.8 11.5 15.0

72.47 13.07 1.32 1.64 0.86 0.44 1.31 0.14 0.04 0.01 b.d.l. 6.8 0.25 b.d.l. 98.09 10.8 0.9 34 1.1 4.3 2.3 92.1 0.1 b.d.l. 16.1 114.6 9.8 20.7 231.5 0.9 8.6 6.5 5 0.6 7.1 11.7 10.9

70.67 11.36 3.4 5.13 0.3 0.02 0.04 0.21 0.05 0.03 b.d.l. 8.1 0.63 0.08 99.31 74.3 1.2 308 0.5 8.5 8.2 5349.3 0.1 b.d.l. 24.3 88.7 4.3 1.7 537.3 0.4 3.9 0.8 8 0.2 3.7 20.6 10.8

62.7 18.14 2.44 6.81 0.27 0.02 0.11 0.22 0.03 0.01 b.d.l. 9.2 0.08 b.d.l. 99.95 6 0.8 274 b.d.l. 2.6 8.7 51.5 0.2 b.d.l. 62.8 191.2 7.4 3.4 104.8 0.4 5.1 1.4 16 0.1 3.0 25.8 18.5

65.95 14.71 4.84 2.86 0.64 0.07 3.13 0.19 0.02 0.11 b.d.l. 7.4 0.46 1.89 99.92 149.8 7.2 87 12.2 5.2 1.8 545.7 1.1 b.d.l. 23.9 126.9 6.7 72.2 54.6 0.7 8.6 1 6 0.3 5.3 18.9 9.6

64.72 11.64 5.47 3.81 2.45 0.05 2.58 0.13 0.02 0.26 0.001 8.7 1.5 1.99 99.84 21.3 28.6 94 1.4 2.6 1.7 447.3 0.5 b.d.l. 17.9 84.6 4.8 54.5 56.9 0.4 5.4 0.7 8 0.3 4.7 17.6 12.0

95.03 0.88 1.85 0.04 0.02 0.02 0.15 0.08 0.03 b.d.l. 0.003 1.5 0.02 0.2 99.61 142.1 33.3 48 40.1 79.4 2.1 3741.6 20.5 2.6 10.1 39.7 1.9 3 95.2 0.2 1 1.3 1 0.2 3.9 20.9 9.5

87.86 4.08 3.14 0.32 0.11 0.03 1.17 0.07 0.02 0.01 0.003 3 0.1 1.91 99.82 735.4 186.5 412 24.8 30.1 3.1 816.9 9.6 0.3 9 37.7 1.4 22.4 27.2 0.2 1.2 1.4 3 0.2 4.2 26.9 7.0

67.76 16.74 2.29 0.31 0.11 0.1 4.29 0.28 b.d.l. b.d.l. 0.002 6.5 0.01 1.26 98.4 28.1 114.7 46 b.d.l. 3.1 2.3 418.7 0.3 b.d.l. 4.5 88.9 3.7 64.9 30.6 0.2 1.3 3.8 7 0.8 19.8 24.0 18.5

63.96 17 4.09 4.62 0.21 0.05 3.3 0.21 0.02 0.07 b.d.l. 6.4 0.33 0.99 99.93 10.3 2.2 217 2.4 1.5 2 572.4 0.2 b.d.l. 35.2 141.2 7.4 58.2 20.1 0.8 9.2 0.7 7 0.2 4.0 19.1 9.3

45.11 7.23 36.17 0.34 0.06 0.05 1.87 0.14 0.13 b.d.l. 0.002 8.8 0.12 0.18 99.9 851.2 10.5 14 11.7 38.9 1.7 254.2 19.3 0.3 15.2 73.9 3.3 33.3 24 0.2 2.5 1.2 6 0.2 4.9 22.4 16.5

45.05 14.72 7.71 5.95 7.26 0.26 1.64 0.86 0.44 0.13 0.025 15.2 3.62 0.68 99.26 1626.5 102.6 1336 33.6 20.4 86.9 1710.9 4.9 0.4 16.1 87.5 11.5 31.5 200.7 0.6 4.1 0.9 19 0.7 5.4 7.6 19.2

39.38 16.25 25.35 7.54 0.22 0.01 0.14 0.2 0.12 0.14 0.001 10.5 0.39 3.99 99.86 7.2 15.7 247 27.1 63 0.3 1173.2 1.6 0.4 15 161.7 8.6 2.6 30.6 0.7 10.5 2.6 6 0.6 10.8 18.8 12.3

75.12 1.43 11.04 0.04 0.01 0.02 0.32 0.04 0.01 b.d.l. 0.001 6.9 0.02 9.62 94.93 N10000 162.1 135 334 325.7 6.1 33822.2 49.8 15.8 3.5 18 0.9 6.5 753.8 0.5 0.7 1 1 0.3 5.1 20.0 1.8


SiO2 Al2O3 Fe2O3* MgO CaO Na2O K2 O TiO2 P2O5 MnO Cr2O3 LOI ∑C ∑S Total Cu Pb Zn As Au (ppb) Ni Ba Mo Sb Y Zr Nb Rb Sr Ta Th U Sc Nb/Y Zr/Y Zr/Nb Nb/Ta

231

232

Table 4 Rare earth element (REEs, ppm) compositions of the hanging and footwall rocks from the Murgul mine. The normalizing chondrite values are from Taylor and McLennan (1985). CAP1-1

CAP1-2

CAP1-15al

CAP1.15fr

Columnar jointed dacite 12.1 28.1 3.43 14.2 3.5 0.83 3.91 0.75 5.04 0.98 2.7 0.55 3.59 0.55 80.23 0.66 2.15 2.38

12.7 29.9 3.59 15.6 3.7 0.81 3.71 0.87 4.91 0.99 3.27 0.48 3.53 0.54 84.6 0.64 2.13 2.54

17.1 32.8 4.86 19.6 5 0.91 4.47 1 6.14 1.22 3.93 0.62 3.85 0.6 102.1 0.56 2.13 3.08

DP1-8

DP1-10

DP1-19

CAP1-9

14.5 33.3 4.19 16.9 4.3 0.83 4.5 0.94 5.04 1.12 3.22 0.51 3.51 0.55 93.41 0.56 2.10 2.85

15 32.5 4 15.6 3.4 0.8 3.41 0.76 3.82 0.77 2.28 0.39 2.41 0.36 85.5 0.69 2.74 4.50

23 52.6 5.82 25.1 4.9 0.77 3.47 0.59 3.95 0.93 2.85 0.45 3.57 0.56 128.56 0.53 2.92 4.44

22.1 47.6 5.9 23.3 5.1 1.34 4.38 0.75 3.59 0.65 1.84 0.32 1.88 0.23 118.98 0.82 2.69 10.39

DP1-15

DP1-17

DP1-18

CAP1-3

CAP1-4

+CAP1-5



1.5 2.1 0.26 2.2 0.6 0.06 0.5 0.06 0.24 b.d.l. 0.21 b.d.l. 0.16 0.03 7.92 0.32 1.55 5.41

11.4 22.8 2.44 9.3 1.9 0.35 2.24 0.49 3.05 0.67 1.91 0.35 2.1 0.34 59.34 0.50 3.73 3.62

0.7 b.d.l. 0.06 b.d.l. 0.1 b.d.l. 0.13 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. 0.99 – 4.35 –

2.4 4.1 0.47 1.9 0.3 0.07 0.34 0.03 0.28 b.d.l. 0.14 b.d.l. b.d.l. 0.02 10.05 0.65 4.97 12.97

12.1 25.1 2.82 12.3 2.4 0.44 2.79 0.6 3.04 0.68 2.04 0.35 2.42 0.35 67.43 0.50 3.13 3.74

8.2 16.2 1.74 8.1 1.8 0.43 3.08 0.73 4.37 0.88 2.26 0.33 2.44 0.34 50.9 0.54 2.83 2.61

CAP1-7

CAP1-8

CAP1-11

CAP1-12

CAP1-13

CAP1-15

DP1-3

DP1-4

DP1-5

DP1-6

9.9 20.9 2.43 9.1 2.2 0.39 2.38 0.5 3.01 0.65 2.09 0.32 2.47 0.34 56.68 0.50 2.80 3.15

15.1 30.2 3.52 14.8 2.9 0.61 3.38 0.75 3.96 0.89 2.91 0.47 3.17 0.49 83.15 0.58 3.24 3.33

6.7 12.3 1.31 6.1 1.6 0.27 1.2 0.25 1.71 0.37 1.13 0.19 1.36 0.23 34.72 0.55 2.60 3.15

1.2 1.8 0.21 0.7 0.3 b.d.l. 0.14 0.07 0.3 b.d.l. 0.19 b.d.l. 0.27 0.02 5.2 – 2.49 6.49

13.4 29.8 3.81 16.8 4 0.92 4.2 0.83 5.23 1.1 3.51 0.57 3.66 0.56 88.39 0.66 2.08 2.59

15.5 33 4.09 16.6 4.6 0.9 4.62 0.88 5.33 1.12 3.54 0.55 3.77 0.53 95.03 0.57 2.09 3.16

20.5 43.6 5.37 24.4 5.8 1.41 5.69 1.25 6.73 1.47 4.07 0.67 4.46 0.65 126.1 0.72 2.20 3.41

5.4 10.8 1.26 5 1.2 b.d.l. 1.48 0.26 1.66 0.23 0.73 0.13 0.79 0.08 29.02 – 2.80 7.30

25.4 51.6 6.24 25.5 5.9 1.19 5.9 1.2 6.95 1.47 4.22 0.78 4.94 0.79 142.1 0.59 2.68 3.48

0.8 0.5 0.1 0.5 0.1 b.d.l. 0.23 0.07 0.42 b.d.l. 0.23 b.d.l. 0.2 0.01 3.16 – 4.97 8.65

Table 4 (continued) DP1-7

DP1-12

DP1-13

DP1-14

DP1-16

DP1-18B

DP1-20

DP1-21

DP1-22

DP1-23A

DP1-23B

DP2-1

DP2-6

DP2-4

DP2-7

DP2-8

CAP1-6

DP1-11

DP2-5

CAP1-10

DP2-2

DP1-9

6.6 13 1.68 6.8 1.7 0.23 1.79 0.3 2.34 0.39 1.2 0.21 1.14 0.15 37.53 0.39 2.41 4.76

16 33.9 4.2 18.5 3.4 0.5 2.7 0.45 2.63 0.56 1.7 0.28 1.84 0.31 86.97 0.47 2.93 5.58

1.6 4.1 0.51 2.4 0.5 0.11 0.72 0.08 0.41 0.06 0.26 b.d.l. 0.21 0.02 10.98 0.54 1.99 8.65

12.8 23.4 2.61 9.5 2 0.42 2.33 0.41 2.22 0.44 1.14 0.23 1.69 0.26 59.45 0.58 3.98 5.32

23.3 44.7 4.75 14.4 3.3 0.57 1.86 0.42 2.37 0.6 1.67 0.23 2.18 0.34 100.69 0.62 4.39 7.41

15.5 47.2 4.31 21.6 4.3 0.88 3.44 0.63 3.85 0.86 2.52 0.42 2.52 0.48 108.51 0.66 2.24 3.49

14.7 43.7 4.65 19.2 5.6 1.32 7.9 1.47 9.34 2.2 6.57 1.05 7.43 1.1 126.23 0.59 1.63 1.44

19.3 41.2 4.06 15.1 2.6 0.65 2.86 0.42 3.51 0.81 2.25 0.43 3.05 0.46 96.7 0.70 4.61 4.54

18.2 36.5 3.65 11.4 2.8 0.53 2.28 0.42 2.13 0.56 1.69 0.3 2.16 0.37 82.99 0.60 4.04 5.32

4.1 8.9 0.99 3.8 1.1 0.27 1.17 0.22 1.47 0.33 0.9 0.16 1.37 0.13 24.91 0.70 2.32 3.41

13.1 27.8 3.4 13.1 2.6 0.87 2.79 0.51 2.77 0.6 1.89 0.29 2.23 0.33 72.28 0.95 3.13 4.29

3.9 8.1 0.97 3.6 0.8 0.3 1.1 0.18 1.34 0.32 0.88 0.12 0.74 0.16 22.51 0.95 3.03 2.64

10.2 19.1 1.93 7.5 0.9 0.37 0.57 0.08 0.89 0.17 0.61 0.1 0.8 0.12 43.34 1.43 7.05 9.19

15.9 37.6 3.5 11.1 3.2 0.86 3.87 0.67 5.04 1.18 3.36 0.46 3.65 0.58 90.97 0.72 3.09 2.96

9.9 19.6 2.16 9.1 2 0.3 1.58 0.42 2.13 0.52 1.54 0.19 1.66 0.23 51.33 0.48 3.08 4.65

27.1 59.8 6.83 24.7 4.3 1.12 3.07 0.57 2.97 0.47 1.36 0.2 1.3 0.16 133.95 0.87 3.92 18.31

2.9 11 1.34 4.8 2.9 0.86 4.59 0.78 4.81 0.69 1.87 0.28 2.37 0.37 39.56 0.70 0.62 0.85

5.5 9.3 1.08 3.7 1.1 0.23 1.12 0.35 1.84 0.39 1.22 0.2 1.25 0.19 27.47 0.61 3.11 3.13

2.9 4.5 0.55 1.8 0.8 0.14 0.73 0.09 1.06 0.12 0.35 0.06 0.56 0.08 13.74 0.53 2.25 3.92

2.4 b.d.l. 0.08 b.d.l. 0.1 b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. b.d.l. 2.58 – 14.92 –

Footwall dacitic pyroclastics La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu ∑REE EuN/EuN* LaN/SmN LaN/LuN

8.9 19 2.28 8.5 1.9 0.37 1.93 0.44 2.52 0.46 1.62 0.26 1.62 0.24 50.04 0.57 2.91 4.01

10.6 25 2.96 11.8 3.6 0.74 5.18 0.97 6.21 1.24 3.4 0.49 3.84 0.51 76.54 0.51 1.83 2.25

7.9 15.5 1.9 9.1 1.8 0.36 1.79 0.33 2.16 0.4 1.4 0.23 1.49 0.23 44.59 0.59 2.73 3.71

14.3 29.1 3.85 15.4 3.5 0.77 2.99 0.62 3.28 0.66 2.22 0.35 2.15 0.35 79.54 0.69 2.54 4.42


La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu ∑REE EuN/EuN* LaN/SmN LaN/LuN

DP1-17A

Purple vitric tuff


a

b

c

d

e

f

g

h

233

Fig. 9. a–d) N-type MORB (Sun and McDonough, 1989) normalized multi-element spider diagrams, e–h) chondrite (Taylor and McLennan, 1985) normalized REE patterns for the studied volcanics from the Murgul mine, showing enrichment and depletion of REEs during the alteration processes (symbols are as in Fig. 8).

vary from 20.3 to 20.4‰ and −92 to to 102‰, respectively. The δ18O values of the illites (Table 7) are generally lower than those of the other minerals as a result of relatively high formation temperature. Similar findings were reported in the Canadian VHMS deposits (Gemmell and Fulton, 2001; Green et al., 1983; Heaton and Sheppard, 1977; Huston, 1999) and hydrothermal systems in Japan (Marumo et al., 1995). In the studied area, there are no data on illites or the other types of clay minerals regarding the radiometric alteration age, and the age relationships are generally given based on the fossil contents of the sedimentary units and lithostratigraphic correlations. In Table 7, the K–Ar dating of the illites (b 2 μm fraction) indicates that hydrothermal alteration processes occurred between Maastrichtian and Early Danian (73–62 Ma).

5. Discussion 5.1. Alteration vectors 5.1.1. Mineral composition vector Different methods are applied to identify the mineralogical and chemical changes in the footwall and hanging wall rocks that may

have occurred during ore formation (Böhlke, 1989; Hermann and Berry, 2002; Mountain and Anthony, 1996). One of the best known methods among them is a least squares spreadsheet method for calculating mineral proportions from whole rock major element analyses (MINSQ), proposed by Hermann and Berry (2002). The mineralogical contents of the studied samples used in these calculations were identified by petrographical and XRD investigations. The calculated MINSQ results are shown in Table 5. According to the MINSQ results, the common alteration mineral assemblages are consistent with the XRD determinations (Table 2) and best described as intense silica alteration in addition to sericite, chloritite, rare smectite and kaolinite alteration.

5.1.2. Major element lithochemical vectors To quantify the intensity of sericite and chlorite alteration resulting from the breakdown of sodic plagioclase and glass, which is a common feature of Kuroko massive sulfide deposits, the Ishikawa alteration index (AI; Ishikawa et al., 1976) is employed. The alteration index (AI) of Ishikawa is described as the ratio of K2O + MgO to the sum of all the alkaline and alkaline earth oxides. The index differs from 50 to 100 for hydrothermally altered rocks, and AI = 100 means that all the

234 Table 5 Mineralogical compositions (wt%) based on the MINSQ –(Hermann and Berry, 2002) of the Murgul mine samples. AI, Ishikawa alteration index, AI = 100*(K2O + MgO) / (K2O + MgO + Na2O + CaO) (Ishikawa et al., 1976); CCPI, chlorite– carbonate–pyrite index, CCPI = 100*(MgO + FeOtotal)/(MgO + FeOtotal + Na2O + K2O) (Large et al., 2001). Sample IDs beginning with CAP indicates Çakmakkaya and with DP refers to Damar open pits. Ser

Fe-Chl

Mg-Chl

Ilt/Sme

Pl

Kfs

Acc

Cb

AI

CCPI

Columnar jointed dacite

32.93 32.72 38.60 36.85

0.00 0.00 11.21 6.02

0.00 0.00 0.00 0.00

5.93 6.73 6.06 6.06

Sme 0.00 0.00 0.00 0.00

Kln 0.00 0.00 0.00 0.00

12.40 12.08 0.00 0.00

20.76 31.18 34.69 35.75

18.97 8.73 3.20 8.09

Gp 1.64 1.56 0.00 0.00

0.00 0.00 0.03 0.04

Brt

Bt 0.00 0.00 0.00 0.00

Ox 2.89 2.96 3.32 3.08

Sul 0.00 0.00 0.00 0.00

2.05 1.93 1.21 1.12

1.67 1.69 0.20 1.11

Total 99.23 99.56 98.53 98.12

R 0.242 0.219 0.002 0.002

46.84 32.93 36.90 35.47

43.78 47.70 52.01 50.36

DP1-17A DP1-19 CAP1-9

Purple vitric tuff

26.07 20.19 13.00

0.00 0.00 0.00

8.89 0.00 1.61

3.10 19.49 19.57

0.00 34.80 0.00

0.00 0.00 0.00

0.00 14.79 19.74

16.73 0.00 18.15

0.00 4.34 5.58

1.65 0.32 2.72

0.00 0.00 0.00

26.33 0.00 0.00

0.00 0.00 5.75

0.00 0.00 0.00

0.82 0.77 4.67

8.42 2.08 6.92

92.02 96.78 97.71

0.289 0.059 0.651

41.35 67.03 36.42

82.52 82.74 75.90

DP1-15 DP1-17 DP1-18


0.00 0.00 0.00

0.00 0.00 0.00

0.00 0.11 0.07

0.00 0.00 0.00

0.00 0.00 11.06

0.00 0.00 0.00

0.00 0.00 0.00

0.10 1.59 0.00

0.00 0.00 5.85

93.83 93.88 79.72

0.00 0.00 0.00

0.00 0.00 0.00

0.00 0.00 0.00

0.00 0.00 0.00

2.97 2.70 2.17

3.10 1.70 1.13

100.00 99.98 100.00

20.914 2.548 1.499

1.65 0.47 3.54

93.46 74.44 41.00

CAP1-3 CAP1-4 CAP1-5 CAP1-6 CAP1-7 CAP1-8 CAP1-10 CAP1-11 CAP1-12 CAP1-15 DP1-3 DP1-4 DP1-5 DP1-6 DP1-7 DP1-8 DP1-9 DP1-10 DP1-11 DP1-12 DP1-13 DP1-14 DP1-16 DP1-18B DP1-20 DP1-21 DP1-22 DP1-23A DP1-23B DP2-1 DP2-2 DP2-4 DP2-5 DP2-6 DP2-7 DP2-8

Footwal dacitic pyro.

65.97 68.58 75.88 36.38 77.61 66.35 79.32 81.22 91.18 31.63 57.54 64.94 32.64 92.46 69.01 62.15 26.47 74.73 22.03 70.96 80.37 67.17 52.07 56.59 39.31 56.99 40.98 48.38 50.71 93.92 73.35 82.97 20.12 63.58 47.45 43.42

17.35 18.31 12.92 15.81 14.84 20.35 11.02 10.45 1.04 0.00 32.17 2.42 36.02 0.00 1.16 3.09 0.00 14.46 0.00 12.84 7.89 21.01 30.43 0.00 1.33 0.31 0.93 26.45 20.72 0.57 3.27 9.46 7.79 27.67 36.27 27.91

1.17 1.06 1.22 1.79 1.24 1.52 0.00 0.00 0.00 0.00 0.00 0.91 1.12 6.25 0.92 1.40 6.39 0.96 5.64 1.89 2.45 1.53 0.00 1.57 0.01 0.00 0.00 1.34 3.60 3.54 0.03 1.01 33.82 0.35 1.12 0.00

10.31 0.00 0.01 1.26 0.00 0.23 1.14 1.42 0.79 3.87 2.95 0.00 2.06 0.00 0.55 13.49 0.00 1.58 26.34 8.22 2.83 4.67 5.99 20.81 3.37 22.83 24.94 12.43 13.80 0.00 0.00 1.22 29.43 2.45 1.25 20.30

0.00 0.00 0.00 0.00 0.00 0.09 0.00 0.00 0.00 0.00 3.26 4.44 23.02 0.00 4.22 0.00 0.00 4.14 0.00 0.00 0.00 0.00 0.00 0.00 43.85 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.00 0.00 0.00 1.21 2.84 8.06 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 9.68 5.33 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.49 15.77 31.17 3.95 0.00 0.00 0.00 0.00 0.00 0.00 5.46 4.43

0.21 3.18 2.73 0.00 0.00 0.87 0.20 0.00 0.00 0.29 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 16.35 1.75 0.80 1.16 5.67 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.93 0.04 0.04 0.28 0.38 0.71 0.75 0.36 0.17 45.02 0.95 0.39 0.44 0.00 0.00 0.68 0.00 0.31 0.00 0.00 0.41 0.44 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.31 0.00 0.00 0.00 0.85 0.43

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.22 11.52 0.00 0.00 0.00 0.00 8.84 6.71 0.00 0.31 7.69 0.00 0.00 0.00 0.00 1.51 6.38 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.00 0.00 0.00 0.00 0.00 0.00 0.21 0.00 0.00 0.94 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.88 4.71 0.00 0.00 0.55 4.11 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.06

0.04 0.00 0.00 0.00 0.00 0.00 0.05 0.02 0.33 0.00 0.06 4.52 0.12 0.00 0.03 0.03 0.00 0.00 0.00 0.00 2.26 0.03 0.13 0.00 0.00 0.89 0.01 0.01 0.07 0.63 5.58 0.12 0.23 0.12 0.07 0.17

0.00 2.41 1.56 0.01 2.93 1.58 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.00 0.00 0.00 34.90 0.26 0.00 0.34 0.00 0.00 3.42 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

0.95 5.05 3.25 0.42 0.02 0.02 4.65 2.73 2.69 0.00 0.00 21.79 0.61 0.45 2.03 2.53 54.42 2.39 1.54 0.92 2.41 1.58 0.50 0.00 0.00 0.00 0.03 3.34 2.31 0.26 17.43 3.73 7.28 3.39 2.34 1.44

0.00 0.16 0.14 0.22 0.20 0.43 0.18 0.22 0.00 1.62 0.53 0.00 0.00 0.00 0.00 0.00 0.00 0.00 4.11 0.03 0.08 0.27 0.17 2.72 0.28 0.07 0.19 0.41 0.27 0.14 0.03 0.19 0.18 0.50 0.58 0.26

0.76 0.00 0.00 0.10 0.00 0.00 0.09 0.01 0.14 1.11 0.00 0.00 0.00 0.00 0.00 2.23 0.26 0.08 8.87 0.58 0.17 0.23 0.04 9.92 0.57 0.83 1.12 0.97 3.17 0.00 0.01 0.17 0.55 0.00 0.00 0.66

97.69 98.78 97.75 92.38 100.33 100.22 97.94 96.44 96.56 99.41 97.45 99.42 96.03 99.16 96.43 97.64 87.55 98.97 92.57 97.20 99.68 98.10 99.88 97.84 95.58 97.73 99.94 101.39 94.65 99.05 100.00 98.87 99.41 98.07 95.40 99.08

0.315 0.018 0.018 0.031 0.006 0.028 0.017 0.005 0.137 0.072 0.052 0.009 0.217 0.166 0.025 0.130 1.380 0.030 0.339 0.185 0.035 0.039 0.026 2.234 0.002 0.347 4.359 0.014 0.025 0.022 0.043 0.011 1.163 0.027 0.006 0.126

95.46 95.52 97.01 95.26 97.13 93.38 88.48 95.21 88.64 25.62 96.78 79.07 92.58 89.66 95.92 79.32 – 94.12 50.23 94.05 94.77 94.65 73.47 36.34 69.41 94.17 95.98 89.40 71.88 82.61 95.55 91.41 97.09 95.55 95.63 96.82

70.16 62.79 63.05 94.48 33.70 15.32 74.37 69.13 93.62 45.89 22.91 97.24 34.39 94.82 54.06 81.62 – 57.33 87.15 73.89 77.62 56.71 39.38 90.89 61.77 99.27 98.58 69.28 76.85 90.93 96.70 72.38 99.51 48.41 35.06 71.25

Qz, quartz; Ser, sericite; Fe–Chl, Fe-chlorite; Mg–Chl, Mg-chlorite; Sme, smectite; Kln, kaolinite; Ilt/Sme, illite/ smectite; Pl, plagioclase (albite + anorthite); Kfs, K-feldspar; Gp, gypsum; Brt, barite; Bt, biotite; Ox, oxide (hematite + magnetite); Sul, sulfide (pyrite, chalcopyrite, sphalerite and galena); Acc, accessory (sphene, apatite); Cb, carbonate minerals (mainly calcite, magnesite, dolomite, siderite, ankerite); R, residual SSQ.


Qz CAP1-1 CAP1-2 CAP1-15al CAP1-15fr


a

235

Fig. 10a and b. Fig. 10a displays K2O increasing with AI increments. As is normally expected, Na depletion is accompanied by AI increases with trends from the albite side and dolomite–ankerite points to the chlorite–sericite corner (Fig. 10b). Using the Ishikawa index alone cannot produce useful data to understand the nature of alteration due to its limitations; it is not able to separate chlorite alteration from sericitic alteration. The chlorite– carbonate–pyrite index (CCPI) is proposed by Large et al. (2001) to measure chlorite alteration, Mg–Fe carbonate alteration and pyrite, magnetite or hematite enrichments. Hanging wall dacites are equally affected by sericitic and chloritic alteration, but chloritization was more effective on the purple vitric tuff (Table 5). The CCPI values for the gypsum-bearing vitric tuffs are not reliable; although it appears that they were subjected to a severe chlorite alteration, this is not confirmed by the SEM and XRD data. A diagram of AI versus CCPI was applied for the studied volcanics (Fig. 10c), as proposed by Large et al. (2001) The CCPI values of the footwall rocks, ranging from 15.32 to 99.51 coupled with high AI values, indicate the inner part of the alteration zones (Fig. 10c). Considering both the MINSQ data and alteration index values in light of the mineralogical data from the studied volcanics, the alteration types can be identified as follows: epidote + chlorite ± sericite alteration, chlorite alteration, gypsum formation, silica alteration, quartz ± chlorite ± sericite alteration, and quartz + argillic alteration. 5.2. Chemical mass changes

b

c

Fig. 10. Ishikawa alteration index (AI) versus (a) K2O wt% and (b) Na2O wt% graphs (after Large et al., 2001) for a set of samples from the Murgul mine. The samples with N60 AI is accepted as hydrothermally altered. (c) AI versus chlorite–carbonate–pyrite index (CCPI) box plot showing principal hydrothermal and diagenetic alteration trends (after Large et al., 2001) for the Murgul mine (ab, albite; carb, carbonate; calc, calcite; chl, chlorite; ep, epidote; ser, sericite; py, pyrite. For the index values see Table 5; symbols are as in Fig. 8).

feldspars and glass were completely converted to sericite and/or chlorite. The calculated AI values for the hanging wall rocks are from 32.93 to 46.84 for columnar jointed dacites, 36.42 to 67.03 for purple vitric tuff, and 0.47 to 3.54 for the gypsum-bearing vitric tuff. The very low AI values of the gypsum-bearing vitric tuff are explained by gypsum contents as high as gypsum ore. The AI values of the footwall pyroclastics range from 25.62 to 97.13. The AI increases towards the center of the alteration zone, suggesting a location below the ore horizon (Table 5). AI versus K2O and Na2O for the volcanics are shown in

Based on the alteration types, all the studied samples were separated into three groups for the hanging wall and four groups for the footwall rocks (Table 6). The mass change calculations of MacLean and Kranidiotis (1987) using single precursor material were applied to these groups, accepting that all these volcanics evolved from a similar source. The least altered samples were selected based on the alteration indexes (CCPI and AI; Table 5) and box plots of Large et al. (2001; Fig. 10c) For the mass calculations, Zr is accepted as an immobile element due its high correlation with the other elements (r N 0.5), and the results are given in Table 6 and Fig. 11. Table 6 and Fig. 11 indicate that hydrothermal alteration around the Murgul mine mainly caused a volume increase apart from the hanging wall dacite, which was suffering from epidote + chlorite ± sericite alteration. The stock siliceous ore and highly silicified samples are characterized by abnormal volume increases of 825.85 and 584.82 g/100 g rock, explained by increments in silica and iron, and the total depletion of alkalis. The quartz + chlorite ± sericite and quartz + argillic zones are represented by 58.54 and 10.42 g/100 g rock volume increases. The relative increase or lesser leaching of K is involved with the sericite replacement of plagioclase and glass and the formation of illite/smectite. Overall, Fe enrichment is always met by pyrite formation accompanied by quartz and chlorite. The behavior of Ba is completely linked with advanced quartz alteration, barite occurrence and Cu, Zn, etc., with ore minerals. Although REEs were completely enriched in the stock siliceous ore horizon, LREEs show depletion in the silica alteration zone and enrichment in the others; whereas the opposite is true for HREEs (Table 6 and Fig. 11). Hydrothermal alteration within the hanging wall rocks reflects their alteration mineralogy and the non-importance of quartz alteration on these rocks but the importance of chlorite alteration implied by Fe and Mg enrichments (Table 6 and Fig. 11). However, gypsum-bearing vitric tuffs exhibit very different patterns due to high gypsum contents characterized by enrichment in Si, Fe, Mg and Ca. Al and K enrichment is probably due to accompanying illite detected in SEM studies (see Fig. 7). 5.3. Temperature and origin of ambient fluid Clay minerals are formed within different environments as a result of interactions between rock and fluid at several temperatures, and

236 Table 6 Average major (%) and trace element (ppm) compositions of the hanging wall and footwall rocks showing similar hydrothermal alteration patterns. The reconstructed compositions (RC) and net mass change (ΔCi) are calculated based on the formulae of MacLean and Kranidiotis (1987) and Zr is accepted as an immobile element. The mass changes are g/100 g rock for oxides and ppm/100 g rock for trace elements and REEs. Hanging wall rocks Leastaltered Mean


Columnar jointed dacite epidote + chlorite ± sericite alteration Mean

RC

Purple vitric tuff chlorite alteration ΔCi

Mean

RC

Gypsum bearing vitric tuff gypsum formation ΔCi

Mean

RC

Stock siliceous ore

ΔCi

Mean

Silica alteration

RC

ΔCi

Mean

Quartz + chlorite ± sericite alteration RC

ΔCi

Mean

RC

Quartz + argillic alteration ΔCi

Mean

RC

ΔCi

70.63 70.90 66.29 −4.34 57.23 65.44 −5.19 11.14 171.53 103.29 71.50 662.00 591.38 95.96 653.91 585.67 82.94 131.49 60.86 78.68 84.22 15.98 14.17 14.60 13.65 −0.52 18.12 20.71 6.55 3.62 55.72 42.03 1.66 15.33 1.16 0.95 6.46 −7.23 9.21 14.60 0.43 15.00 16.06 2.37 4.00 4.35 4.06 0.07 8.12 9.29 5.29 0.60 9.27 5.41 26.44 244.82 240.82 2.69 18.31 14.45 3.59 5.70 1.70 1.15 1.24 −2.62 MgO 1.39 1.41 1.32 −0.07 5.25 6.00 4.62 0.73 11.20 9.86 0.05 0.46 −0.93 0.13 0.86 −0.48 1.48 2.35 0.96 0.70 0.75 −0.59 CaO 2.85 2.87 2.68 −0.16 7.06 8.07 5.23 83.04 1278.44 1275.69 0.01 0.12 −2.73 0.02 0.16 −2.59 0.33 0.52 −2.33 0.37 0.39 −2.36 Na2O 2.80 3.38 3.16 0.35 1.41 1.61 −1.19 0.00 0.00 −2.71 0.04 0.38 −2.42 0.02 0.12 −2.59 0.06 0.09 −2.71 0.14 0.15 −2.56 3.59 1.95 1.83 −1.77 1.74 1.98 −1.61 0.79 12.22 8.75 0.24 2.27 −1.32 0.16 1.09 −2.38 2.15 3.41 −0.18 3.63 3.88 0.41 K2O 0.41 0.39 0.37 −0.05 0.74 0.85 0.44 0.08 1.16 0.76 0.04 0.35 −0.07 0.04 0.30 −0.10 0.17 0.27 −0.14 0.30 0.32 −0.08 TiO2 0.10 0.09 0.09 −0.02 0.19 0.21 0.11 − 0.00 −0.10 0.01 0.12 0.01 0.02 0.14 0.04 0.03 0.05 −0.05 0.02 0.03 −0.07 P2O5 MnO 0.06 0.06 0.06 0.00 0.13 0.15 0.09 − 0.00 −0.06 0.00 0.00 −0.06 0.01 0.07 0.01 0.04 0.06 0.00 0.00 0.00 −0.06 0.00 0.00 0.00 0.00 0.00 0.00 0.00 − 0.00 0.00 0.00 0.02 0.01 0.00 0.02 0.02 0.00 0.00 0.00 0.00 0.00 0.00 Cr2O3 Total 100.00 −6.51 14.34 1442.92 825.85 584.82 58.54 10.42 Cu 2.90 27.80 25.99 23.09 34.70 39.67 36.77 16.70 257.10 254.20 8308.40 76,925.33 76,922.43 1277.40 8704.47 8701.57 198.61 314.88 311.98 88.98 95.24 92.34 Pb 2.00 1.07 1.00 −1.00 6.53 7.47 5.47 1.10 16.93 14.93 461.37 4271.67 4269.67 16.93 115.39 113.39 55.44 87.90 85.90 30.60 32.75 30.75 Zn 21.00 42.67 39.89 18.89 68.00 77.75 56.75 5.67 87.24 66.24 3631.33 33,621.58 33,600.58 68.33 465.64 444.64 314.57 498.73 477.73 49.33 52.80 31.80 As 1.60 1.10 1.03 −0.57 1.85 2.12 0.52 1.90 29.25 27.65 939.47 8698.28 8696.68 38.93 265.30 263.70 42.91 68.04 66.44 12.24 13.10 11.50 Ni 2.60 – – – 5.97 6.82 4.22 0.37 5.64 3.04 4.13 38.27 35.67 2.80 19.08 16.48 2.12 3.36 0.76 1.15 1.23 −1.37 Ba 170.70 215.37 201.37 30.67 262.97 300.66 129.96 141.83 2183.57 2012.87 20,190.30 186,936.76 186,766.06 1967.70 13,408.31 13,237.61 1328.90 2106.89 1936.19 409.97 438.80 268.10 Mo 0.70 0.67 0.62 −0.08 0.30 0.34 −0.36 0.15 2.31 1.61 41.23 381.77 381.07 22.23 151.50 150.80 4.68 7.42 6.72 1.47 1.57 0.87 Sb 0.10 0.10 0.09 −0.01 0.20 0.23 0.13 0.10 1.54 1.44 25.13 232.70 232.60 6.00 40.89 40.79 0.71 1.12 1.02 0.25 0.27 0.17 Y 30.60 34.37 32.13 1.53 22.93 26.22 −4.38 1.20 18.47 −12.13 4.00 37.03 6.43 4.60 31.35 0.75 18.98 30.09 −0.51 25.33 27.12 −3.48 Zr 132.40 141.60 132.40 0.00 115.80 132.40 0.00 8.60 132.40 0.00 14.30 132.40 0.00 19.43 132.42 0.02 83.51 132.41 0.01 123.70 132.40 0.00 Nb 5.70 5.33 4.99 −0.71 8.33 9.53 3.83 0.70 10.78 5.08 1.05 9.72 4.02 1.20 8.18 2.48 4.13 6.55 0.85 5.40 5.78 0.08 Rb 91.30 34.17 31.95 −59.35 37.83 43.26 −48.04 5.30 81.60 −9.70 6.30 58.33 −32.97 3.43 23.40 −67.90 38.35 60.80 −30.50 58.85 62.99 −28.31 Sr 102.00 113.73 106.34 4.34 229.97 262.93 160.93 1040.73 16,022.45 15,920.45 379.60 3514.62 3412.62 51.70 352.29 250.29 51.56 81.75 −20.25 87.78 93.96 −8.04 Ta 0.30 0.33 0.31 0.01 0.50 0.57 0.27 0.10 1.54 1.24 0.40 3.70 3.40 0.15 1.02 0.72 0.32 0.51 0.21 0.33 0.36 0.06 Th 4.30 3.73 3.49 −0.81 5.57 6.36 2.06 0.27 4.11 −0.19 0.63 5.86 1.56 0.53 3.63 −0.67 3.62 5.74 1.44 3.38 3.62 −0.68 U 0.80 1.17 1.09 0.29 1.53 1.75 0.95 0.40 6.16 5.36 1.05 9.72 8.92 1.27 8.63 7.83 1.13 1.79 0.99 2.07 2.21 1.41 Sc 14.00 13.33 12.47 −1.53 17.00 19.44 5.44 0.00 −14.00 1.00 9.26 −4.74 1.00 6.81 −7.19 5.36 8.49 −5.51 7.17 7.67 −6.33 ΣLREE 66.07 77.76 72.70 6.63 100.03 114.37 48.30 7.67 118.06 51.99 17.19 159.17 93.10 9.15 62.35 −3.72 52.74 83.61 17.54 66.14 70.79 4.72 0.67 10.24 −3.92 3.10 28.70 14.54 2.45 16.67 2.51 8.26 13.10 −1.06 10.99 11.76 −2.40 ΣHREE 14.16 15.61 14.60 0.44 10.98 12.56 −1.60 SiO2 Al2O3 Fe2O⁎ 3


ΣLREE, total light REE; ΣHREE, total heavy REE; Fe2O⁎3 , All Fe as Fe2O⁎3 .


237

Fig. 11. Bar plots referring average net mass change for the groups of similar alteration patterns, calculated on the basis of MacLean and Kranidiotis (1987). Values used for calculations and the results were given in Table 6.

their O- and D-isotopic compositions are commonly used to enlighten the physicochemical conditions of their formation (Sheppard et al., 1969). To constrain the formation temperature of clays, the initial δ18Ofluid composition is accepted in a definite narrow change for

thermometric calculations. The value of δ18Ofluid is given as 1.4–3‰ by Altaner et al. (2003) for similar hydrothermal systems. It is also proposed as between − 1 and + 4‰ for the hydrothermal fluids needed to form the VHMS deposits (Huston, 1999). On the other hand, this

Table 7 δ34S values of gypsum, δ18O and δD values of the illites–chlorite, and K–Ar dating data of pure illite minerals (b2 μm). The temperature (T°C) and δ18Ofluid composition calculations of the fluid are based on the illite and chlorite δ18O values from the Murgul mine. Sample no.

MDA-21 DP1-18 MD-11 MD-12 DP2-7 MC-19 DP1-22

Location

Damar Damar Damar Damar Damar Çakmakkaya Damar

Mineral

Gypsum Gypsum Illite Illite Illite Illite Chlorite

δ18OV-SMOW

15.1 15.5 8.2 6.6 8.7 – 8.6

δDV-SMOW

−92 −102 −49 −42 −50 – −52

δ34S

20.4 20.3 – – – –

Age (Ma)

– – 65.5 ± 1.7 73.3 ± 1.9 – 62.0 ± 1.6 –

δ18Ofluid = 0

δ18Ofluid = 4

T (°C) = 140

T (°C) = 170

T (°C) = 250

T (°C)

T (°C)

δ18Ofluid

δ18Ofluid

δ18Ofluid

– – 171 203 162 – 69

– – 269 332 253 – 136

– – 3.52 1.92 4.02 – 6.79

– – 5.34 3.74 5.84 – 6.18

– – 8.76 7.16 9.26 – 7.81

238


of Schardt et al. (2001) The equations of O'Neil and Taylor (1969) for illites and Wenner and Taylor (1971) for chlorite were used as follows, and the results are given in Table 7. 3 illite 6 2 10 In α fluid ¼ 2:38 10 =T −3:89

3

chlorite

10 In α fluid

Fig. 12. δD versus δ18O plot showing the isotopic compositions of the illites, chlorite and gypsum from the Murgul mine. MWL, meteoric water line; the lines for kaolinite and montmorillonite are from Savin and Epstein (1970); SH, supergene/hypogene line of Sheppard et al. (1969) and SM, smectite line representing isotopic compositions of smectite in equilibrium with meteoric waters at 20 °C. Mh and Ml, isotopic compositional ranges of high temperature and low temperature montmorillonites (Andrews, 1980; Lawrence and Drever, 1981); Black Sea, the isotopic composition of its present day seawater (Balderer, 1999); magmatic and metamorphic fields from Sheppard (1986). Spotted field indicates calculated fluid composition (see Table 7).

value is reported as 0‰ or from 0 to + 4‰ as a mixture of mainly seawater and hydrothermal liquids for the Hellyer (Tasmania) deposits (Green and Taheri, 1992). During the formation temperature calculations for the illite and chlorite from the Murgul mine, the δ18Ofluid compositions are accepted as between 0‰ and +4‰, consistent with those

6 2 ¼ 1:56 10 =T −4:70

The calculated temperatures for the studied illites (162 to 332 °C; Table 7) are consistent with the results from Japan obtained in drilling cores from mining areas (Eslinger and Savin, 1973; Inoue et al., 1992). Similarly, investigations of VHMS deposits indicate 300–350 °C formation temperatures in copper-bearing ore body zones (Pisutha-Arnond and Ohmoto, 1983). Consequently, the constrained temperatures for the Murgul mine must be close to but not higher than those values. Taking into account that the studied illites were collected from the central part of the alteration hole and close to the ore body, it should be inferred that the δ18Ofluid for the studied clays should be approximately 4‰ as a mixture of seawater and hydrothermal liquids. For the chlorite, the formation temperatures of the study area are calculated to be from 69 to 136 °C. The formation temperature of 69 °C is very low for chlorite. In addition, the formation temperatures of chlorite were 235 °C based on the stable isotope data for the Pacmanus hydrothermal fields (Beaudoin et al., 2007) and 295–315 °C for the Gurupi belt (Brazil) gold deposits. Additionally, the fluid inclusion studies of Gökçe (2001) revealed that the high NaCl, CaCl2 and MgCl contents of the ore forming fluids in the ore minerals lowered towards the later episodes, rising up to 254.0 °C and lowering to 110.2 °C. Çiftçi et al. (2001) also reported formation temperatures between 160 °C and 320 °C using liquid rich, two phase fluid inclusions, indicating low fluid salinities ranging from

Fig. 13. Deduced evolutionary schematic model for the Murgul massive sulfide deposit; (a) simplified cross-section showing horizontal and vertical distribution of the Late Cretaceous ore bearing volcanic units and granitoid emplacement, (b) hydrothermal alteration zones around the massive sulfide ore lens.


1 to 5 wt.% eq. NaCl. All these formation temperatures obtained from the fluid inclusion studies are consistent with the formation temperatures. The VHMS deposits were derived either from seawater-dominated, buoyant fluids that built mounds on the seafloor (e.g., the Hokuroku Basin, Japan) or from saline fluids that reversed buoyancy when mixing with seawater and filled basins on the seafloor (the Iberian pyrite belt and the Mount Read province in Tasmania; Solomon and Quesada, 2003). Taking into account that fluid temperatures from 140 to 250 °C and equilibrium conditions generated between minerals and fluids were assumed, the probable δ18Ofluid values were calculated using the equations of O'Neil and Taylor (1969) for illites and Wenner and Taylor (1971) for chlorite. The selected temperature ranges were consistent with those findings; 150–250 °C was used by Gemmell and Fulton (2001) during the geochemical modeling of VHMS deposits. The obtained results indicate mainly seawater compositions with a mixture of magmatic water in several degrees (Table 7). Gökçe (2001) reported 5‰ and 8‰ values for δ18Ofluid and δDfluid, respectively, based on fluid inclusion studies of quartz. These values indicated that hydrothermal solutions might have been mainly meteoric origins mixing and/or interacting with a small amount of sea water. In Fig. 12, the isotopic features of clays from different environments are depicted. Under hydrothermal alteration conditions, the isotopic compositions of clays are placed close to the meteoric water line (Faure, 1986). In the diagram, illite and chlorite compositions are plotted on the magmatic water area, compatible with the temperature calculations and gypsum located near the kaolinite line and representing lower formation temperature conditions for the hanging wall rocks. The δ18O and δD compositions and calculated formation temperatures of illite and chlorite (Table 7) suggest the effect of magmatic fluids. The obtained data also indicate decreasing temperature from the illite in the center of the massive ore body to chlorite outward. The δ34S and δ18O values of sulfates from the Kuroko deposits were slightly higher than the Miocene seawater sulfate values, from +20 to + 21‰ and 0‰, respectively (Sakai et al., 1970; Watanebe and Sakai, 1983). Çağatay and Eastoe (1995) reported 20-28.8‰ δ34S values for gypsum from the Murgul mine and indicated that these values are a few per mil above the contemporaneous (Upper Cretaceous) seawater sulfates. In the studied samples, the δ34S values for gypsum from the hanging wall vitric tuff vary from 20.3 to 20.4‰, suggesting contributions from seawater sulfates reduced by Fe-oxide/-hydroxide phases within altered volcanic units. Although the number of the stable isotopic analyses is limited to make extended interpretations, one should take into account that all the results were gained from purified mineral phases from distinct alteration zones, carrying fingerprints of the formation conditions of the Murgul mine. 5.4. Modeling of the alteration pipe The modeling of alteration pipes during the exploration of the VHMS needs to answer questions such as the characterization and degree of alteration. In addition, general alteration models have been produced by many authors (e.g., Large et al., 2001; Shikazono, 2003), but each deposit has its own alteration fingerprints. Hydrothermal alteration zones in the footwall and hanging wall rocks from the Murgul may be classified in general as follows: quartz–chlorite–sericite–pyrite, sericite–chlorite– pyrite, chlorite–sericite–pyrite and chlorite–carbonate–epidote–quartz/ albite–sericite. In the footwall rocks, silica alteration is the most common alteration type and accompanies all the alteration minerals. A 250 m thick stringer zone (Çağatay, 1993) was formed within the highly silicified pumiceous tuff (Fig. 13). In particular, the dacitic tuffs in the Çakmakkaya open pit were completely converted to quartz and their original texture disappeared. The rocks were cut by quartz veins including pyrite and carbonate. In the Damar open pit, argillic alteration and silica alteration can be observed. Carbonate alteration with siderite, ankerite, dolomite and seldom calcite, albite and limonite are other types of alteration products

239

observed in the footwall rocks (see Figs. 4 and 5). Based on the microscopic investigation, small amounts of sericite are accompanied by quartz and opaques. Field observations and mineralogical studies indicate that this silica alteration zone with sericite (illite) is enveloped by a 150 m thick sericite zone. In this zone, dacitic tuff contains quartz phenocrysts, the sericite replacement of plagioclase with minor curved biotite flakes as mineral components, glass shards and pumice fragments. Sericite on glass shards and plagioclases, chlorite and rare calcite formations are also identified. Vertically and laterally, the sericite (illite) zone partially changes to a chlorite zone. The sericite zone in the hanging wall rocks is characterized by its soft texture, distinctive white color, euhedral coarse grained pyrite and gypsum lens and kaolinite content. The thickness of the zone is approximately 10 m. The hanging wall rocks of the massive sulfide lens are highly altered, and four types of alteration have been identified: chlorite, carbonate (calcite), epidote, and quartz–albite and sericite (Fig. 13b) Although there is no distinct zonation, all four types of alteration can be observed at one point, and their lateral changes outward cannot be determined. Chlorite and carbonate formed close to the massive lens, changing to quartz–albite and sericite alteration zones, respectively. Carbonates, mainly in the form of calcite accompanied by epidote within chlorite- or sericite-bearing zones, occurred as selective replacements of components such as plagioclase and disseminations in the rocks (Fig. 13b). 5.5. Modeling of the hydrothermal alteration environment In the study area, hydrothermal alterations of the volcanic units resulted from hydrolysis and dissolution mechanisms. Micromorphological images reveal that illite fibers form booklets, suggesting direct precipitation mechanisms from solution parallel to the flushing direction. Furthermore, the edges of the illite booklets with chlorite booklets and kaolinite crystals and locally developed smectite flakes imply the breakdown of precursor chlorite, smectite and kaolinite in the parent volcanic rocks via hydrothermal fluids. These breakdown processes also resulted in the depletion of Na and Ca and the conservation of Al and K for the precipitation of authigenic illite. K was released via the alteration of K-feldspar and glass shards, which allowed the precipitation of illite under alkaline environmental conditions and poor drainage (Berner and Berner, 1996; Eberl and Hower, 1977; Erhenberg, 1991; Hoffman and Hower, 1979; Meunier and Velde, 2004; Ziegler, 2006). Furthermore, the significant conservation of Al, nonexistence or consumption of K during the formation of illite and depletion of alkalis by hydrothermal fluids caused the development of kaolinite under acidic environmental conditions. Locally, the S concentrations in conjunction with Ca resulted in the precipitation of gypsum under acidic conditions, which developed in a well-drained system (Ece and Schroeder, 2007; Ece et al., 2008; Kadir and Erkoyun, 2013). Consequently, the excess silica precipitated as quartz and opal-CT (Kadir and Akbulut, 2009; Meunier and Velde, 2004; Velde, 1977). The studies on the chemistry and temperature of the hydrothermal fluids have indicated that the temperature of the fluids for the Kuroko type deposits is approximately 250 ± 50 °C (Shikazono, 1976), whereas the temperature for the massive sulfide deposits that formed on the seafloor is ~ 360 °C (Von Damm et al., 1985). In those environments, the Na and K have higher concentrations in the fluid than Mg. The Na/K and Na/Ca activity of the ambient fluid will change with the alteration zone (Inoue, 1995). Additionally, pH will be affected by the salinity and reactions between aluminosilicate minerals and fluid (Arnórsson, 1978; Giggenbach, 1984; Henley and Ellis, 1983). The mineralogical changes in the alteration zones are determined by mass changes between the hydrothermal fluids and minerals (Helgeson, 1979). The other factors affecting hydrothermal alteration are the flow velocity and temperature of the fluid in addition to the water–rock interaction. In the hydrothermal alteration haloes of the Murgul mine, changes in alteration mineralogy were controlled by many factors such as the

240


composition and temperature of the hydrothermal fluid and the chemical activity of the cations. The identified hydrothermal alteration pattern is quite similar to those reported in the Kuruko types (e.g., Shikazono, 2003). However, Özgür et al. (2008) emphasized the differences between the Murgul deposit and the Kuroko-type deposits based on their fluid inclusion temperatures and salinity in addition to the δ34S values in the sulfide ore minerals, the δ18O and δD, and the anion and cation analyses in the secondary quartz crystals. Thus, they classified the Murgul deposit as a transition between Kuroko-type deposits and copper porphyries. Hydrothermal alteration and ore formation in the Murgul mine may have developed as a result of a fault- and fracture-controlled tectonic regime in the Eastern Pontides, associated Late Cretaceous calc-alkaline to transitional felsic volcanism (~ 91 to 83 Ma U–Pb zircon dating; Eyüboğlu et al., 2014) and medium-/high-K to shoshonitic granitoid emplacements (~ 78 to 74 Ma U–Pb zircon datings; Kaygusuz et al., 2013, 2014). The development of thick stockwork ore with highly silicified and argillized pumiceous tuffs reveals that the area was subjected to penetration by hydrothermal fluid activity. Acidic hot hydrothermal fluids generated from Late Cretaceous granitoid intrusions mixed with heated seawater flushed along faults and fractures during the Late Cretaceous to Early Paleocene (~73 to 62 Ma) episode based on the K–Ar dating of the illite fraction. Therefore, the U–Pb zircon age data of the Late Cretaceous ore-bearing dacites and granitoid intrusions may suggest that the Murgul VHMS deposit should have been formed by fluids that were a mixture of seawater and magmatic fluids resulting from the emplacement of granitoid intrusions (Fig. 13a). 6. Conclusions Based on the field geology, alteration mineralogy, lithochemistry, stable isotope data and K–Ar dating of clays from the Late Cretaceous volcanics of the Murgul VHMS deposit in the northern part of the Eastern Pontides metallogenic belt, we conclude the following major findings: • The field observations and mineralogical and lithochemical determinations reveal that quartz–chlorite–sericite–pyrite, sericite–chlorite– pyrite, chlorite–sericite–pyrite and chlorite–carbonate–epidote– quartz/albite–sericite alteration zones in the hanging wall and footwall volcanics developed as a result of acidic hydrothermal alteration controlled by fault and fracture systems during the Late Cretaceous to Early Paleocene (73–62 Ma) episode based on the K–Ar dating of illite fractions. • The occurrence of stockwork veins, silica alteration, argillic alteration, brecciation, and clay mineralogy zonation outward from the massive ore deposit containing illite, illite/smectite, chlorite, and kaolinite accompanied by coarse grained euhedral pyrite and gypsum lens and the occurrence of carbonate, albite and Fe-oxide/-hydroxide phases in the hanging wall and footwall rocks reveal the former operation of an acidic hydrothermal process(es). • Increases in Si, Al, Fe, Ba, Sr, K and ΣLREE (towards the center of the ore deposit), depletion in Na, Ca and ΣHREE and positive/negative Eu anomalies mainly suggest the devitrification of glass shards and pumice fragments under hydrothermal alteration conditions related to the massive sulfide ore mineralization. Mg, Fe, Al, Ca and Na leaching outward to the ore deposit resulted in the precipitation of chlorite + smectite under basic conditions. • The coexistence of illite booklets with chlorite, smectite and kaolinite reveals that illite formed either authigenically or from in situ precipitation derived via a mechanism of paired dissolution and precipitation and the conservation of K. • The O and H isotopic data from the illites and chlorite reveal that alteration patterns were developed in a temperature (perhaps 253–332 °C and 136 °C, respectively), suggesting a lateral decrease in temperature from the illite in the center of the massive sulfide deposit to the

chlorite outward. The S isotopic data imply a contribution from seawater sulfates reduced by Fe-oxide/-hydroxide phases. • The alteration patterns and ore formation in the Murgul mine were formed by hydrothermal fluids, a mixture of seawater and magmatic fluids resulting from the emplacement of Late Cretaceous granitoid intrusions.

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