Petrology, geochemistry, and evolution of the iron skarns along the northern contact of the Eğrigöz Plutonic Complex, Western Anatolia, Turkey

The Çatak and Küreci skarn districts are located approximately 10 km NW of Emet (Kütahya) in Western Turkey. The skarn and associated ore formations mainly occur at the contact between intrusive rocks of the Eğrigöz Plutonic Complex (EPC) and calcareous pelitic schists with limestone lenses of the Sarıcasu Formation and meta-carbonate rocks of the Arıkaya Formation.

Turkish Journal of Earth Sciences http://journals.tubitak.gov.tr/earth/ Research Article Turkish J Earth Sci (2013) 22: 61-97 © TÜBİTAK doi:10.3906/yer-1006-2 Petrology, geochemistry, and evolution of the iron skarns along the northern contact of the Eğrigöz Plutonic Complex, Western Anatolia, Turkey Tolga OYMAN*, İsmet ƯZGENÇ, Murat TOKCAER, Mehmet AKBULUT Department of Geological Engineering, Faculty of Engineering, Dokuz Eylül University, Tınaztepe, Buca, TR−35100 İzmir, Turkey Received: 01.06.2010 Accepted: 30.06.2011 Published Online: 04.01.2013 Printed: 25.01.2013 Abstract: The Çatak and Küreci skarn districts are located approximately 10 km NW of Emet (Kütahya) in Western Turkey The skarn and associated ore formations mainly occur at the contact between intrusive rocks of the Eğrigöz Plutonic Complex (EPC) and calcareous pelitic schists with limestone lenses of the Sarıcasu Formation and meta-carbonate rocks of the Arıkaya Formation The major, trace, and rare earth element analysis of the igneous rocks indicate that they are high level, subalkaline, calc-alkaline, peraluminous to metaluminous I-type intrusions, generated in a continental arc setting Three distinct skarn-type mineralization, differing in their host rocks and distance from the intrusive body, were chosen to establish the ore-forming conditions in different episodes of skarn formation The Küreci iron mineralization is hosted in a skarn zone with well-developed zoning from unaltered granodiorite and endoskarn, andradite-diopside exoskarn, to diopside-wollastonite exoskarn towards a marble reaction front In Sakari, the iron mineralization and associated skarn have formed due to successive fracturing and infiltration processes From early contact metamorphic rocks to late prograde skarn at the Sakari prospect, the composition of clinopyroxene ranges from (Di50–70 Hd28–53 Jo1–2) to (Di19–73 Hd26–­77 Jo2–6) and the composition of garnet ranges from (Ad95–99 Gr1–5) to (Ad40–61 Gr36–58), respectively The presence of anisotropic grossular garnet with high Fe2+/Fe3+ in crosscutting pyrrhotite-pyrite-bearing veinlets coupled with hedenbergitic pyroxene (Mg-poor clinopyroxene with higher Fe2+/Fe3+) is consistent with reducing conditions during the later stage of prograde skarn alteration The Çatak iron skarn is characteristic, with its high sulphide content due to the presence of pyrrhotite, pyrite, and arsenopyrite, and low proportion of garnet to pyroxene The sulphur isotope (δ34S) compositions in the pyrrhotite-dominant skarn zones range between +0.84 to –2.23‰ We interpret the bulk of the sulphur in the system as of igneous derivation and there has not been any significant sulphur contribution from a crustal source Fluid inclusion measurements conducted on skarn minerals of the proximal zone and distal zone+vein skarn revealed high homogenization temperatures (371 to >600°C) and varying salinity values (10.5 to >70 wt% NaCl) The fluid inclusion data indicate that there are at least three fluids associated with the genesis of the proximal skarn where the high garnet/pyroxene ratios are found Fluid inclusions that represent the early stages both in garnet and pyroxene plot in ‘Primary Magmatic Fluid’ and ‘Metamorphic Fluids’ fields A magmatic fluid, presumably located at deeper parts of the system, mixed with a metamorphic fluid during its ascent Over all the Eğrigöz skarn a weak or moderate retrograde skarn alteration envelope formed, dominated by the incursion of meteoric waters in the system, indicating limited fluid-rock interaction Hydrofracturing resulted in pressure decrease and inclusions with Type III (L+V+S) inclusions that plot in the ‘Secondary Magmatic Liquid’ and ‘Magmatic Meteoric Mixing’ fields Key Words: geochemistry, iron skarn, calc-silicate, Eğrigöz, Turkey Introduction In the Cenozoic copious magmatic activity took place in Western Anatolia and the Aegean region Magmatism was most widespread and abundant during the oldest phase, which began in the Late Eocene (about 37 Ma ago) and ended in the Middle Miocene (about 14–15 Ma ago) It is represented by volcanic and plutonic rocks of orogenic affinity The Eybek, Kozak, Alaỗam, and Erigửz volcanoplutonic centres, predominantly consisting of intrusive rocks, are the main examples of this early phase (e.g., Yılmaz 1990) The Eğrigöz Plutonic Complex (EPC) is situated inland in Western Anatolia within the core and cover * Correspondence: tolga.oyman@deu.edu.tr sequences in the northeastern part of the Menderes Massif (Figure 1) The EPC, with an outcrop area of approximately 550 km2, is one of the largest plutons in western Turkey, and is associated with a number of mineral occurences including iron skarns, Au-Ag-bearing mesothermal PbZn-Cu veins, skarns and gossans (ệzgenỗ et al 2006) The district has been of economic interest since the second half of the 20th century, and the magnetite resources around the EPC are becoming increasingly important Recent geochronological studies focused on the crystallizing and cooling ages of the Eğrigöz granite and yield ages around 20 Ma (Işık et al 2004; Ring & Collins 2005; Hasözbek et 61 40 yu Macedonia Greece Ductile shear zones and detachment faults Post Miocene brittle faults Menderes Massif İzmir-Ankara zone EĞRİGÖZ PLUTONIC COMPLEX TAŞBAŞI FORMATION KIZILBÜK FORMATION TERTIARY VOLCANICS and TUFFS EMET FORMATION ALLUVIUM GERNİ TOKLAR GILMANLAR EVCİLER İMRANLAR ÖRENCİK ÇALDİBİ KIRKBUDAK FORMATION BUDAĞAN FORMATION İMRANLAR FORMATION DAĞARDI MELANGE ure Fig ÇOBANLAR KIŞLAKƯY DOLAYLAR FORMATION SİMAV METAMORPHICS SARICASU FORMATION ARIKAYA FORMATION N MINERALIZATION DETACHMENT FAULT THRUST FAULT APPROXIMATE FAULT km EĞRİGÖZ MÜMYE FAULT MUSALAR KÜRECİ Figure 11 ÇAYIR KIZILBÜK DEĞERMİSAZ Figure Location of the study area in Turkey and geology of the study area (simplified after Akdeniz & Konak 1979; Işık & Tekeli 2001; Erkül 2010) Granite km Hisarcık Emet Iraq Iran Eastern stocks Simav Syria Eğrigöz plutonic complex TURKEY ANKARA Miocene volcanosedimentary succession Naşa Kütahya Armenia Alluvium Ko e İstanbul nit gra nob a GEORGIA QUATERNARY CENOZOIC 40 MESOZOIC 30 PLIOCENE TERTIARY MIOCENE PALEOCENE CRETACEOUS TRIASSIC JURASSIC 62 PALEOZOIC Bulgaria OYMAN et al / Turkish J Earth Sci OYMAN et al / Turkish J Earth Sci al 2010) Although some studies have been carried out on aspects of the economic potential of the district, studies of ore and calc-silicate paragenesis and stable isotope studies are lacking (Gümüş 1967; Özocak 1972; Taşan & Cihnioğlu 1984) The aim of this study is to examine the characteristics of this important, but otherwise little known iron district and develop a model for its genesis For this purpose we focus on several iron deposits (Sakari, Çatak, and Küreci) along the northern contact of the EPC, which have representative ore and gangue paragenesis for the mineralization of the northern contact In these deposits we describe the presence of changing redox conditions in ore-forming magmatic-hydrothermal systems based on the mineral chemistry of calc-silicates (e.g., garnet, pyroxene, amphibole) and associated sulphides of Cu, Fe, and As (e.g., chalcopyrite, pyrrhotite, arsenopyrite) Compositional variations in calc-silicate mineralogy reflect differences in magma chemistry, wall rock composition, depth of formation, and oxidation state (Burton et al 1982; Gamble 1982; Meinert 1992, 1997) Fluid inclusion data, together with petrological and isotopic information, may provide complete information for knowing the P and T evolution of the skarn system Although the Sakari, Çatak, and Küreci iron skarns are all spatially and genetically related to the EPC, the differences in skarn texture, paragenesis, and geochemistry are significant Geochemical studies on ore and coexisting calc-silicates in prograde stage or hydrous calc-silicate overprint related to hydrothermal fluids give important clues on the heat and fluid transfer from a cooling magma Rare earth element (REE) mobility is favoured by low pH, high water/rock ratios, and abundant complex ions (CO3–2, F–, Cl–, PO43–, SO42–) in the hydrothermal solutions (Michard 1989; Lottermoser 1990, 1992) REE contents of hydrothermally altered rocks in epithermal and porphyry copper ore deposits indicate that fluid alteration is an important agent in the mobilization of REE (Lottermoser 1990; Hopf 1993; Arribas et al 1995; Bierlein et al 1999; Fulignati et al 1999) Skarn systems adjacent to granite are the most likely sources of the REE and speciation control on the uptake and deposition of the REE from hydrothermal fluids of different temperatures and composition (Smith et al 2000) Wang & Williams (2001) noted that REE were transported in skarn-forming fluids and that their current distribution is influenced by the occurrence of phases, such as allanite and apatite in Cu-Au (Co-Ni) skarns in the Cloncurry district in Queensland, Australia REE contents of ore samples from Pena Colorado iron skarns in Colima, Mexico represent those of the andesitic tuffs of the volcano-sedimentary rocks (Zürcher et al 2001) Trace, and rare earth element (REE) abundances provide an opportunity to investigate the interaction between the mineralizing fluids and the host rocks, with the chemistry of ore-grade samples assisting us to identify and classify the type of the deposit In this paper, we present new geochemical data from the host granite and ore, including compositions of skarn minerals, microthermometric studies on skarn minerals and isotope determinations (S isotopes from pyrite and pyrrhotite and O isotopes from magnetite, pyroxene, and garnet) Based upon this data, we interpret the formation conditions of the various iron skarns with different paragenetic, spatial and temporal characteristics related to the emplacement of the EPC Geologic and tectonic setting of Western Anatolia The geological evolution of Western Anatolia was mainly governed by Palaeo- and Neo-Tethyan events, which preserve remnants of the Tethyan ocean The Neotethys Ocean was obliterated by the collision of the Eurasian and African plates mainly during the Late Cretaceous–Tertiary (Şengör & Yılmaz 1981; Şengör 1987) As a remnant of Neotethys, the İzmir-Ankara Melange zone separates the Sakarya Zone and the Anatolide-Tauride Block now exposed in the metamorphic core complex of the Menderes Massif Intrusion of Palaeogene granitoids in the Sakarya Zone, the İzmir-Ankara mélange zone, and the Menderes Metamorphic core complex are linked by the subduction of the East Mediterranean ocean floor, along the Hellenic trench (Fytikas et al 1984; Pe-Piper & Piper 1989; Gülen 1990; Delaloye & Bingöl 2000) The convergence has been generated in a N–NE direction by subduction along the Aegean and Cyprean arcs in the western and eastern Mediterranean, respectively The Menderes metamorphic core complex has undergone five phases of metamorphism (Bozkurt & Oberhänsli 2001) The age of the main metamorphism affecting the whole massif is Palaeocene– Eocene (Satır & Friedrichsen 1986; Hetzel & Reischmann 1996; Bozkurt & Satır 2000; Lips et al 2001; Rimmele et al 2003; Bozkurt 2004) Intracontinental N–S convergence associated with the Palaeocene–Eocene collision along the İzmir-Ankara suture zone continued until the Oligocene During the early Miocene, crustal thinning in the central Menderes Massif was associated with the denudation of the core complex in the footwalls of the Gediz and Büyük Menderes detachment faults (Emre & Sözbilir 1997, 2007; Lips et al 2001) These comprise mylonitised, metamorphic, and granitic rocks lying below a low-angle detachment fault, with associated chlorite brecciation and two supradetachment basins containing a thick succession of nonmarine strata (Hetzel et al 1995; Emre & Sửzbilir 1997; Koỗyiit et al 1999; Sözbilir 2001, 2002; Seyitoğlu et al 2002; Işık et al 2003, 2004; Bozkurt & Sözbilir 2004) The footwall metamorphic rocks were progressively mylonitised, exhumed, and intruded by syndeformational granitoids (Turgutlu and Salihli granodiorites: the Salihli 63 64 4329217N Kütahya-Simav 0490245E 4345601N Ayazmant Ayvalık Kazdağ 500 000 750 000 estimation 0680634E Kalkan 000 000 900 000 900 150 000 4400497N 4344044N Kütahya-Simav 30–40 % Fe 78 000 No reserve 0683710E Karaağıl 30–50 % Fe 18 000 0.6 % Cu; 46 % Fe and pyrrhotite Fe-Cu Plutonic Complex porphyries of Kozak monzodioritic granodioritic to Pluton diorite of Evciler limestone lenses intercalations, skarn after carbonate lenses and metamorphic rocks with hornfels after regional after marble metamorphic rocks, skarn hornfels after rocks Eğrigöz Pluton granodiorite to quartz Fe metamorphic calc-silicate hornfels after dolomites monzogranite of granodiorite- Eğrigöz Pluton monzogranite of skarn after limestone and rocks Eğrigöz Pluton granodiorite- metamorphic calc-silicate hornfels after monzogranite of granodiorite- lenses Di- Scp, Di, Ad-Gr, Hd, Scp, Pl Ad, Gr, Ad-Gr, Di-Hd Po, Gn, Sp, various Au-Ag-Te-Se Or, Chl, Cal, Qz, Minerals Bn, Mo, Go, Hem, Mt, Cp, Py, Po, Py, Cp Cp) Mt, Hem, (Py, Mt, Py, Hem, Go Oyman 2010 Öztürk et al 2008 Öztürk et al 2005; Taşan & Cihnioğlu 1984 Taşan & Cihnioğlu 1984 1972 Gümüş 1967; Özocak 2003 Po, Cp, Py, Apy, Mt Yücelay 1975; Tufan (Apy, Cp, Ilm) Tamer & Kurt 1982 Önal et al 2009 Dora 1971; Gümüş 1964; Karaaslan & Başarı 1979 Reference Gn, Sp, Py, Po, Mt, Cp, Py Sp, Cp, Gn, Hem, Sp, Gn) Mt, Hem, (Py, Cp, Ore minerals Ep, Amp, Pl, Chl, Qz Ep, Cal, Amp, Ep, Cal, Amp, Scp Di-Hd Ep, Cal, Amp, Di-Hd Ant Qz, Cal, Rt, Or, Pl, Ep, Chl, Tr, Cal, Ep Cal, Tr Ep, Cal Late minerals Ad-Gr, Ad-Gr after limestone blocks and Di- of Eybek Pluton Hd Ad-Gr, Di-Hd, Scp Wo, Ad-Gr, Di-Hd, Wo, Di-Hd, Au (up to Fe Fe Fe Zn, Pb Early Minerals metamorphic rocks, skarn hornfels after calc-silicate marble amphibolite, bearing schist skarn after calcerous, marn after limestone blocks metamorphic rocks, skarn hornfels after Host rock granite, granodiorite Pluton granodiorite of Şamlı of Eybek Pluton Cu Fe-Cu granite, granodiorite of Eybek Pluton granite, granodiorite rocks Associated igneous Pb, Zn, Fe Metal 14 ppm) in 50 % Fe 49 % Fe 50 % Fe 4.10 % Pb 4.38 % Zn 58% Fe 1.25 % Cu % Zn, % Pb 50–60 % Fe 43 000 250 000 Grade Size(t) 0485103E 4336320N Kütahya-Simav Evciler 0695750E 4404200N 0518300E 4408780N 0570560E 4398456N 0519986E 4390300N 0504800E Location ầatak Karaaydn aml Barkaỗ Yayer Deposit Table Major skarn mineralization in the Aegean region of Turkey OYMAN et al / Turkish J Earth Sci OYMAN et al / Turkish J Earth Sci granodiorite yielded 39Ar-40Ar amphibole isochron and biotite plateau cooling ages of 19.5±1.4 and 12.2±0.4 Ma, respectively) (e.g., Hetzel et al 1995; Koỗyigit et al 1999; Lips et al 2001; Sözbilir 2001, 2002; Seyitoğlu et al 2002; Işık et al 2003, 2004; Bozkurt & Sözbilir 2004) Different models were proposed to explain the origin and timing of the extension and granitoid intrusions in western Turkey The back-arc spreading (Le Pichon & Angelier 1979, 1981), the tectonic escape (Şengör 1979; Şengör et al 1985) and the orogenic or gravitational collapse model (Dewey 1988; Seyitoğlu & Scott 1996) are the proposed models The Tertiary magmatism in Western Anatolia consisted of three geochemically distinct phases of magmatic activities due to S–SW retreat of the active subduction zone (Doglioni et al 2002; Innocenti et al 2005) The oldest phase of the magmatic activity in western Anatolia, which began in the Late Eocene (at about 37 Ma) and ended in the Middle Miocene (at about 14–15 Ma), is represented by volcanic and plutonic rocks of orogenic affinity The Eybek, Kozak, Alaỗam, and Erigửz volcano-plutonic centres, predominantly consisting of intrusive rocks, are the main examples of this early phase (e.g., Yılmaz 1990) Radiometric dating of the synextensional granites, which intrude the Menderes Massif and Afyon Zone, are Early Miocene in age K-Ar age determination by Delaloye & Bingöl (2000) shows that the subduction event must have commenced before the Oligocene Based on their K-Ar age determinations on biotite and orthoclase from the Eğrigöz granitoid, cooling ages were obtained of 20.0±0.7 to 20.4±0.6 Ma and 21.2±1.8 to 24.6±1.4 Ma, respectively The EPC was emplaced during the late stage of mylonitic deformation of the extensional tectonic regime and was deformed along the boundary of core rocks of the MCC (Işık et al 2004) On its northern and western boundary, the Eğrigöz granitoid is separated from the cover series by the Simav detachment fault (Işık et al 1997; Işık & Tekeli 2001; Erkül 2010) (Figure 1) The cover sequences of the MCC consist mainly of schist, recrystallized carbonates, and ophiolitic mélange which experienced varying grades of metamorphism Intrusion and cooling of the Eğrigöz granitoid occurred at 22.86±0.47 Ma (40Ar/39Ar ages, Işık et al 2004) More recently, U-Pb zircon analyses have yielded crystallization ages of 19.4±4.4 Ma for the Eğrigöz granite (Hasözbek et al 2010) A cooling age of 18.77±0.19 Ma for the Eğrigöz granite was obtained by Rb–Sr (whole rock, biotite) analyses Local geology The oldest country rocks surrounding the Eğrigöz granitoid are the Simav metamorphic sequence, which is exposed southeast and west of the Eğrigöz Pluton (Figure 1) This unit is comprised of biotite-muscovite schists, muscovitequartz schists, garnet schists, muscovite-quartz-biotite schists, basic schists, quartzite and chlorite-bearing calcschists (Akdeniz & Konak 1979) The Balıkbaşı Formation conformably overlies the Simav metamorphics in the south of the EPC, and is comprised of laminated, bituminous recrystallized limestone reflecting neritic facies conditions The Balıkbaşı Formation is uncomformably overlain by Upper Palaeozoic–Lower Triassic Sarıcasu Formation, mainly comprising schists that are metamorphosed greenschist grade equivalents of detrital sediments with basic tuffs and lavas These schists were first identified by Kaya (1972) as part of the İkibaşlı Formation and are equivalent to the Sarıcasu Formation of Akdeniz & Konak (1979) The Sarıcasu Formation is gradationally overlain by the Arıkaya Formation that outcrops widely around the village of Küreci Based on lithological correlation between the Arıkaya Formation and fossiliferous Permian limestone and its boundary with overlying fossiliferous Middle–Upper Triassic rocks, the age of the formation has been thought to be Permian (Akdeniz & Konak 1979) The limestone lenses in pelitic schists and the meta-carbonate rocks of the Arıkaya Formation are important host rocks for magnetite and pyrrhotite skarns 3.1 Host rocks Aureoles associated with EPC commonly show conspicuous evidence of metasomatic processes related to local injection of magma or hydrothermal fluids into country rocks The skarn zone between the Eğrigöz pluton and the surrounding Palaeozoic Sarıcasu and Arıkaya formations extends ~3.5 km along the contact and is ~10 to ~100 m wide The skarn bodies in Çatak are hosted by both the Palaeozoic Sarıcasu and Arıkaya formations, but the bulk of the ore bodies lie within the Sarıcasu Formation (Figure 1) This unit consists of muscovite-quartz-albite schist, and muscovite-chlorite-calcite-quartz schist intercalated with phyllite and crystalline limestone Phyllite intercalated with schists crops out near the village of Gürepınar The phyllite has well-developed cleavage, and is composed of quartz, plagioclase, sericite, chlorite, titanite, and opaque minerals Recrystallized limestone lenses appear within the schist sequence One of the the largest outcrops of these lenses is observed around the Elỗekka ridge The limestone is fine grained and grey We speculate that hydrothermal fluids migrated along pre-skarn fractures, sedimentary contacts, and other permeable zones until they reacted with the schist intercalated with carbonaterich intervals in the Sarıcasu Formation Successive fracturing and infiltration of more evolved mineralizing fluids may have destroyed the original spatial zonation Along the northern border of the Eğrigöz Pluton close to the contact, the rock is hornfelsed in a 10- to120-m-thick zone identified by its fine schistosity and dark green to olive green colouration Besides the more 65 OYMAN et al / Turkish J Earth Sci common porphyroblastic schists, minor mica-rich varieties with lepidoblastic fabric and quartzo-feldspathic varieties were observed Albite porphyroblasts, quartz with undulatory extinction, calcite, muscovite, chlorite, pyrite, and magnetite are the main constituents of the schist The schistosity strikes mainly NE with variable dips of 30–60° NW Muscovite-quartz-albite schist was typically observed along the eastern contact of the Eğrigöz pluton The schist generally possesses medium-high strength with medium to coarse schistosity The rock has a porphyroblastic texture with quartz and albite porphyroblast lengths exceeding cm The porphyroblast-hosted matrix consists mainly of muscovite and minor amounts of epidote, calcite, and chlorite The Arıkaya Formation is a bedded package of recrystallized limestone with a dense joint system, intensely developed fold structures, and local brecciation Recrystallized limestones with grain sizes up to mm are common, and the limestone is locally dolomitic The ore-bearing calcic skarn is located at the northern contact zones with granodiorite 3.2 Plutonic rocks The plutonic rocks in the region have a holocrystalline, hypidiomorphic texture with quartz, plagioclase, orthoclase, biotite, and hornblende as major rockforming minerals Apatite, zircon, titanite, and muscovite are common accessory phases The opaque minerals (e.g., magnetite, pyrite), chlorite, sericite, epidote, and tourmaline are present, but less common Fine-grained plutonic varieties were observed close to the contact with the skarn Aplitic dykes of the EPC cross-cut plutonic rocks associated with magnetite deposits at the eastern and southern contacts, whereas in the centre and northern part of the pluton, dykes are associated with polymetallic veins Selected whole-rock analyses of 10 samples from the EPC are listed in Table In total 68 fresh, coarseto medium-grained phaneritic granitoid samples were collected from the northern part of the EPC and 10 of them were selected, based on their location near the mineralization sites In the QAP molecular normative diagram (Streckeisen 1976), the rocks plot in the monzogranite and granodiorite fields with a transitional trend (Figure 2a) and in the Q-P diagram (Debon & Le Fort 1983), plot in the granodiorite and adamellite field (Figure 2b) The granitoids are plotted on the boundary between the metaluminous and peraluminous granitoid fields in an aluminum saturation diagram (Maniar & Piccoli 1989) (Figure 2c) The granitoid rocks are calc-alkaline on the Na2O+K2O–CaO versus SiO2 diagram (Frost et al 2001) (Figure 2d) The chondrite-normalized REE patterns for EPC granitoids related to iron skarns are shown in Figure 2e (normalizing values after Sun & McDonough 66 1989) The granitoids exhibit moderate LREE fractionated patterns with a negative Eu anomaly (Eu/Eu*= 0.44– 0.61) They show nearly flat HREE patterns with Tb/Ybn ~1.2 Transitional trends from pre-plate collision to syncollision settings of granitoids are distinctive in Figure 2f The Rb vs Nb+Y diagram (Pearce et al 1984) emphasizes that the granitoids are volcanic arc granites (Figure 2h) and plot in the volcanic arc + syn-collision field in the Nb-Y diagram (Figure 2h) Contact metamorphic assemblages The limestone lenses in pelitic schists of the Sarıcasu Formation and the meta-carbonate rocks of the Arıkaya Formation are important host rocks for magnetite and pyrrhotite skarns in the Çatak region Early distal isochemical metamorphism caused the formation of calc-silicate hornfels and marble Hornblende-biotite hornfels contains quartz, hornblende, biotite, plagioclase, muscovite, and andalusite Pyroxene hornfels contains diopside, garnet, plagioclase, K-feldspar, biotite, cordierite, and sillimanite Metamorphosed carbonate rocks include marble Metamorphism of pelitic schists and calcareous rocks has produced an assemblage of andalusite, cordierite, sillimanite, feldspar, biotite, tourmaline, and quartz The presence of cordierite, andalusite, and sillimanite imply metamorphic temperatures of 500°C and a maximum pressure of 2kb (Winkler 1967; Mason 1990) Stabilities of calc-silicate assemblages depend on mole fractions of CO2 in the aqueous phase, as well as on pressure, temperature, and the composition of solid solution minerals (Sato 1980; Newberry 1982; Meinert 1982) If CO2 was near 0.1 kb during the metamorphism and early skarn formation, a minimum temperature of 550°C is required for grossularite and wollastonite stability at kb (Greenwood 1967; Gordon & Greenwood 1971; Meinert 1982) A minimum temperature of 550°C is also required for the presence of diopside in pyroxene hornfels As prograde alteration reflects the protoliths, pelitic schists are represented by hornblende hornfels, calcareous rocks by pyroxene hornfels and meta-carbonate rocks by pyroxene-garnet skarns The pyroxene hornfels facies is developed within a restricted zone close to the contact with the pluton The presence of sillimanite indicates pyroxene-hornfels facies conditions and aluminum rich protoliths (Winkler 1967) The paragenesis in the pyroxene-hornfels facies comprises cordierite, pyroxene, garnet, plagioclase, sillimanite, orthoclase, biotite, titanite, apatite, chlorite, and quartz The hornblende hornfels facies is characterized by the occurrence of andalusite, amphibole, biotite, muscovite, quartz, and subordinate plagioclase, calcite, chlorite, apatite, tourmaline, axinite, titanite, and zircon Typical pressures for the hornblende hornfels are less than OYMAN et al / Turkish J Earth Sci Table Composition of plutonic rocks Weight % CT-1 CT1-8 CT1-13 CT1-14 CT2-22 CT2-23 CT3-7 OC1-26 KUR1-7 KUR-14 KB-1 SiO2 Al2O3 TiO2 Fe2O3 BaO MnO CaO MgO K2O Na2O P2O5 LOI Total ppm Ba Rb Sr Ga Nb Zr Y Th Ni Cr V Cu Pb Zn La Ce 70.93 14.33 0.32 2.82 0.09 0.03 2.09 0.73 4.13 3.51 0.03 0.94 100.05 71.09 13.92 0.32 2.43 0.09 0.04 2.12 0.73 4.23 3.24 0.12 1.1 99.52 71.16 13.87 0.34 2.89 0.09 0.04 2.03 0.89 4.62 3.13 0.01 0.8 99.95 67.13 15.08 0.45 3.55 0.11 0.06 2.9 1.22 3.95 3.51 0.14 0.85 99.04 72.15 13.76 0.29 2.69 0.09 0.05 2.1 0.8 4.16 3.24 0.11 0.61 100.15 65.9 15.52 0.56 4.22 0.13 0.08 3.13 1.49 4.08 3.38 0.1 0.88 99.55 66.56 15.37 0.51 4.09 0.12 0.06 3.16 1.35 3.74 3.69 0.198 0.85 99.78 67.38 15.2 0.47 3.78 0.11 0.06 1.27 3.75 3.61 0.11 0.73 99.57 67.96 14.78 0.43 3.58 0.12 0.05 2.84 1.12 3.9 3.41 0.05 0.88 99.22 70.01 14.42 0.35 2.9 0.11 0.05 2.42 0.9 3.5 0.03 1.11 99.9 69.08 14.47 0.41 3.39 0.13 0.08 2.4 0.99 4.26 3.37 0.13 0.77 99.6 785 164 230 18 14 145.5 26.5 16 15 690 15 25 25 25 39 72.5 1443 164.4 211.6 19.1 15 151.9 28.5 20.2 20 500 25 2.2 100 25 34.5 59.8 745 175 201 17 20 153.5 27.5 29 16 530 35 15 25 25 34.5 64 973 169 309 19 15 168.5 25 19 17 500 55 15 30 50 39 70.5 701 167 218 17 14 132 23.5 19 18 550 30 15 25 35 31 55.5 1100 152 330 20 17 212 31.5 19 19 440 65 15 25 55 44.5 80.5 1025 173 334 19 16 208 27 16 20 510 65 15 35 55 42 75.5 906 174 313 19 15 187.5 27 19 21 550 50 20 40 50 44 78.5 1005 153 300 18 14 175 25.5 58 22 550 50 15 25 30 37 65.5 937 153 282 17 14 157.5 24.5 21 23 550 35 15 25 35 39.5 70.5 1075 176.5 287 18 15 181 27 19 24 660 40 15 35 55 45 81 4.6 4.4 2.6 0.8 5.5 0.9 0.4 34 28.5 7.9 5.6 1.5 0.7 >0.5 0.4 2.7 >1 2.4 4.1 4.35 2.6 0.76 4.28 4.5 0.88 0.38 0.4 22.8 6.69 5.1 1.7 0.74 >0.5 0.4 1.1 2.66 >1 3.9 4.5 2.7 0.7 4.7 0.9 0.5 20 24.5 6.9 4.9 2.5 0.6 >0.5 0.4 8.5 3.2 >1 6.6 4.2 2.3 4.9 0.9 0.4 20 26.5 7.5 5 1.5 0.6 >0.5 0.4 6.5 2.6 >1 4.5 4.6 3.9 2.2 0.8 4.2 0.4 22 21.5 6.1 4.3 1.5 0.6 >0.5 0.4 5.5 2.7 >1 7.5 5.9 4.9 2.8 1.1 5.8 0.9 0.5 18 31 8.5 5.8 1.5 0.7 >0.5 0.4 4.5 >1 10.4 4.6 2.6 1.1 5.7 0.9 0.4 22 29 5.5 1.5 0.7 >0.5 0.4 6.5 2.8 >1 6.5 6.7 4.3 2.6 5.6 0.9 0.4 22 29 8.4 5.5 1.5 0.7 >0.5 0.4 2.8 >1 4.5 4.2 2.5 5 0.9 0.4 20 25.5 4.9 1.5 0.6 >0.5 0.4 12 2.7 >1 6.3 4.1 2.4 0.9 4.8 0.9 0.5 22 25.5 7.4 4.9 0.6 >0.5 0.4 2.9 >1 5.5 5.7 4.6 2.6 1.1 5.8 0.9 0.4 24 30 8.6 5.6 1.5 0.7 >0.5 0.4 2.8 >1 Co Cs Dy Er Eu Gd Hf Ho Lu Mo Nd Pr Sm Sn Ta Tb Tl Tm U W Yb Ag 67 OYMAN et al / Turkish J Earth Sci kilobars, and temperatures range between 400 and 650°C The existence of andalusite indicates low- to intermediategrade metamorphism in the surrounding aureole With increasing distance from the contact aureole, greenschist facies regionally metamorphosed rocks represent the cover series Skarn mineralogy and paragenesis More than 30 iron skarn occurences are known in the Sarıcasu and Arıkaya formations, of which 12 had been mined between 1950 and 1970 In Çatak district, the area along the northern contact of the EPC contains more than 15 iron deposits The Çatak iron skarn district consists of several bodies that include: Sakari, Çavdarlık, Gưğez, and Katranlı (Figure 3) Among these zones of mineralization, the Sakari prospect differs because it is a magnetite-dominated ore, compared to the other prospects in the Çatak district In the Katranlı, Gưğez, and Çavdarlık prospects, iron mineralization occurs commonly as tabular bodies and lenses associated with disseminated and stockwork-type deposition Subordinate small crosscutting veins and veinlets are also present The mineralization is closely associated with metasomatic skarn consisting mainly of pyroxene, garnet, plagioclase, amphibole, epidote, calcite, and quartz, preferentially replacing pyroxene hornfels facies rocks between 10 to 100 m from the Eğrigöz granodiorite 5.1 Mineralogy of skarn in the Katranlı, Gưğez and Çavdarlık districts A narrow reaction zone (20 cm to 1.5 m thick) is developed in the Göğez and Çavdarlık endoskarn toward the proximal zone of the pluton (Figure 4) At the contact, the granite is a darker greenish colour due to the metasomatic reaction with the wall rock pyroxene hornfels Chlorite, amphibole, and epidote are the characteristic metasomatic minerals in the endoskarn Fracture-controlled metasomatism is the most common replacement mechanism Chlorite and amphibole, as pseudomorphs of pyroxene, are the main calc-silicate minerals associated with opaque minerals in these fracture fillings Disseminated anhedral to subhedral opaque crystals are mantled by chlorite crystals in the endoskarn Epidote and plagioclase are associated with chlorite and amphibole to a lesser extent The plagioclase is replaced by epidote and calcite Biotite is also replaced by chlorite and amphibole pseudomorphs Some disseminated anhedral ore minerals occur, which are hematitized and limonitized The calcic exoskarn is composed chiefly of pyroxene with subordinate garnet and amphibole Microprobe analyses were performed mainly on pyroxene, garnet, amphibole, pyrrhotite, chalcopyrite, and arsenopyrite Details of the analytical methods of microprobe analysis are given in the Appendix 68 Garnet and pyroxene crystals are fractured and crosscut by veinlets of late stage ore and retrograde minerals Euhedral to subhedral pyroxene is the earliest calc-silicate mineral of the prograde stage with the grain size ranging between 20 µm and mm Pyroxene grains within the exoskarn range between hedenbergitic and diopsidic end members with an average composition of Di43–53 Hd46–56 Jo1–2 (Figure 5a; Table 3) Optically and compositionally zoned individual garnet grains typically are 10 µm – mm in diameter In the exoskarn zone, garnet is andradite (Ad97–99) within a narrow compositional range (Figure 5b; Table 4) Pyroxene grains are extensively included in garnet, magnetite, and pyrrhotite as relict crystals Pseudomorphic amphibole replacement after pyroxene is the most common retrograde alteration, followed by the replacement of the epidote, chlorite, and prehnite as vein-fillings The composition of amphiboles varies within the calcic amphibole types (Na+KII Pyroxene Type I>II Type I>II Garnet 20 N=18 18 16 14 12 10 0 10 15 20 25 30 35 40 Salinity (equiv.Wt.%NaCl) 45 50 55 60 Figure 14 Microthermometric data for fluid inclusions in garnet and pyroxenes from the Çatak and Küreci skarns in the Eğrigöz area (a) Homogenization temperatures of primary fluid inclusions in garnet and pyroxenes; (b) Average salinities wt% NaCl eq of primary fluid inclusions in garnet and pyroxenes magnetite skarn to the pyrrhotite skarn, was decreasing whereas pH was increasing The sulphur isotope results reported here are consistent with the interpretation that the bulk of the sulphur in the system is of igneous derivation and implies that there has been no significant contribution from crustal-sourced heavy sulphur (e.g., Ohmoto & Goldhaber 1997) Similar results for isotopically well-homogenized sulphur from pyrrhotite, pyrite, chalcopyrite and arsenopyrite are reported from other Cu, Au, W and Pb-Zn skarn deposits (Figure 17) (Gray et al 1995; Laouar et al 2002; Chiarada 2003; Zhao et al 2003) 9.3 Fluid inclusion constraints Fluid inclusion measurements conducted on skarn minerals in the proximal zone and the distal zone+vein skarn in Çatak revealed high homogenization temperatures (307 to >600°C) and varying salinity values (10.5 to 60 wt% NaCl) Fluid inclusions in the calc-silicates of the prograde stage represent the composition of magmatic fluids after reaction with the carbonate wall rocks Most of the inclusions in both garnet and pyroxene plot in the ‘Primary Magmatic Fluid’ and ‘Metamorphic Fluids’ fields (Figure 19) (Bodnar 1999) A diagram of the temperature of total homogenization versus salinity of all the fluid inclusions studied reveals the existence of two fluids in the Çatak region (Figure 19) An early fluid responsible for magnetite deposition (corresponding to fluid inclusions of Types I and II), is a high temperature fluid (temperature of total homogenization: between 227–>600°C), with a salinity ranging between 3.5–21.1 wt% eq NaCl At Çatak a plot of salinity versus homogenization temperatures does not define a continuous trend between the different stages of skarn formation and may thus suggest intermittent flow of external fluids during retrograde skarn formation at different times, possibly in response to hydrofracturing The magmatic fluid, presumably originating from deeper parts of the system, is mixed during its ascent with metamorphic fluid rather than connate or groundwater due to low fluid-rock ratio Hydrofracturing in a transient pressure increase subsequently results in a geostatic pressure decrease and formation of Type III (L+V+S) inclusions (temperature of total homogenization: between 405.2–>600°C), with a salinity ranging between 37.1–58.7 wt% eq NaCl) that plot in the ‘Secondary Magmatic Liquid’ and ‘Magmatic Meteoric Mixing’ fields (Bodnar 1999) At Küreci the fluid (corresponding to Types I and II fluid inclusions in garnets) responsible for magnetite deposition along the contact between granodiorite and marble is a high temperature fluid (temperature of total homogenization: between 306.5–>600°C), with a salinity ranging between 10.4–22.6 wt% eq NaCl) Calculated 18O values for anhydrous minerals from the early prograde stage (garnet, magnetite and pyroxene) show that they formed from fluids with a significant magmatic component Whitney et al (1985) experimentally showed that between 500 and 650°C, iron accounts for up to 50% of the available chlorine in fluids in equilibrium with rocks of granitic composition Experimental work on magnetite solubility indicates that iron is transported as FeCl2 in sulphur-free, chloride-bearing supercritical fluids (Chou & Eugster 1977; Boctor et al 1980; Frantz et al 1980) The partitioning of metals between melt and magmatic fluid is 83 OYMAN et al / Turkish J Earth Sci b a V L L V 10 m c 10 m d L V V S S L 10 m 10 m Figure 15 Photomicrographs of primary fluid inclusions in garnet and pyroxene in skarn from Eğrigöz skarns (a) Type I inclusions are two phases (liquid + vapour) and liquid-rich at room temperature; (b) Type II inclusions contain two phases (liquid + vapour) and are vapour-rich at room temperature; (c, d) Daughter-mineral (mainly halite)-bearing gas-rich, and aqueous inclusions (Type-III) in garnet of Çatak skarn related to the Cl concentration of the magmatic fluid In the upper levels of the crust, the supercritical fluid consists of vapour and hypersaline liquid phases (Sourirajan & Kennedy 1962; Henley & McNabb 1978; Fournier 1987; Shinohara & Fujimato 1994) Due to its low density, the buoyant vapour phase separated from the dense hypersaline liquid and began to differentially ascend Owing to the high crustal level of this emplacement, the fluid began to boil during or very soon after its release, promoting hydrofracturing and, in turn, further boiling Among CuCl3, CuCl, CuClOH, and CuCl2 the latter was the dominant form of aqueous copper above 300°C A sudden increase in pH could also result from boiling, due to the partitioning of acidic components (e.g., HCl, CO2, SO2, H2S) into the vapour during phase separation (Drummand & Ohmoto 1985) Copper transport by magmatic vapour has been documented both in oxidized or reduced porphyry Cu-Au deposits However, Simon et al (2003) experimentally showed that the iron concentration 84 in the S-bearing magmatic volatile phase (1.1 molal) is significantly higher than in the S-free magmatic volatile phase (0.11 molal) The difference between ore-bearing and barren porphyries may be that ore-bearing porphyries crystallise from high oxygen fugacity melts, which not become depleted in Cu and Au when they become S saturated, whereas barren porphyries crystallise from low oxygen fugacity magmas that 9.4 Comparisons with other major iron deposits in the Anatolides Most of the important iron ore resources of Turkey occur in Central-Eastern Anatolia, which has a geological history of multiple orogenic and tectonic events Hercynian and pre-Hercynian phosphorus-rich (2% P) magnetite deposits, such as Avnik (e.g., Helvacı 1984), Bulam, Pınarbaşı, and Ünaldı, are hosted in Palaeozoic metamorphic rocks of the Bitlis Massif In central-eastern Anatolia prolonged subduction (82.90±0.43 to 79.43±0.58 Ma) between Eurasian and Afro-Arabian plates was OYMAN et al / Turkish J Earth Sci Table Abundances of selected geochemical indicator elements in hornfelses, skarns and ores Çatak Hornfels Skarn+ore Ore % CT2-1 CT4-3 CT2-10 CT2-11 CT1-12 CT4-8 CT1 - CT1-8 CT - a4 Fe Al2O3 CaO MgO S TiO2 P2O5 ppm Mo Cu Pb Zn Ni As Cd Sb Bi Ag Au * ppb Hg Tl Co Cs Ga Hf Nb Rb Sn Sr Ta Th U V W Zr Y La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Tb/Ybn La/Ybn Eu/Eu* Ce/Ce* 3.20 13.95 1.45 0.60 0.01 0.30 0.11 8.04 14.48 0.79 3.03 0.04 0.68 0.16 47.98 12.35 4.97 1.41 0.02 0.31 0.13 33.66 2.55 4.62 3.68