Browsing by Author "Gunay, Kurtulus"

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Au-Rich Bimodal-Mafic Type Volcanogenic Massive Sulphide Deposit Associated With Jurassic Arc Volcanism From the Central Pontide (Kastamonu, Turkey)
(Elsevier, 2022) Gunay, Kurtulus; Oyan, Vural; Donmez, Cahit; Cavdar, Bugra; Ciftci, Emin; Chugaev, Andrey V.; Ma, Chang-Qian
The central part of the Pontide Orogenic Belt, located in northern Anatolia, is a segment of the Alpine-Himalayan orogeny. Cangaldag Metamorphic Complex (CMC) occurs within this segment which consists of ensimatic island arc volcanics and deep sea sediments which occasionally cut cross by mafic sills/dykes. They were exposed to metamorphism under the greenschist facies conditions and remain in tectonic contact with each other. The Say yayla mineralization is one of the recently discovered volcanogenic massive sulfide (VMS) deposits in the CMC with a remarkable Au content. The mafic and felsic metavolcanic rocks are the host-rocks of the Say Yayla mineralization and the ages determined by U-Pb zircon grains of these felsic volcanic rocks range from 170 Ma to 165 Ma indicating Middle Jurassic time. At the 0.1% cut-off grade, 7.5 million tons of resource has been calculated with 0.75 ppm Au, 0.65 wt% Cu, and 0.35 wt% Zn grades. The Say Yayla mineralization consists of massive and semi-massive sulfide minerals and a mineral assemblage represented by predominantly pyrite and chalcopyrite and trace amounts of sphalerite, tennantite and galena. Average base and precious metal grades of the zones occur with >1 wt% Cu are 2 wt% for Cu, 0.7 wt% for Zn, 0.04 wt% for Pb and 1.5 g/t for Au. The sulfur isotope values (delta S-34 VCDT) range from 4.9 parts per thousand to 6.7 parts per thousand for pyrite grains and 4.2 parts per thousand was obtained from the one sphalerite sample. delta O-18 values for the quartz from quartz-rich ore samples were 10.6 parts per thousand and 11.7 parts per thousand delta O-18 (VSMOW)(qtz). delta O-18 (VSMOW)(fluid) values for the ore-forming fluids vary between 0 parts per thousand and 2.4 parts per thousand. Lead isotope compositions of the pyrite minerals were 18.148-18.150 (Pb-206/Pb-204), 15.548-15.550 (Pb-207/Pb-204) and 38.078-38.083 (Pb-208/Pb-204) The geological, geochemical, and isotopic data of the ore and host-rocks reveal that the mineralization is a bimodal-mafic type (Noranda type), which is classified into Cu-Zn group of volcanogenic massive sulfides. Geochemical and geochronological data from the wall rocks further show that mineralization was developed within an ensimatic island arc environment during the Middle Jurassic.
Cenozoic Collisional Tectonics and Origin of Pb-Zn Mineralization in the Bitlis Massif, Se Turkey
(Taylor & Francis inc, 2011) Colakoglu, Ali Riza; Hanilci, Nurullah; Gunay, Kurtulus
Hasbey Pb-Zn-F mineralization in the Bitlis Massif, south of Lake Van, lies within the Neotethyan suture of the Alpine orogenic belt. Mineralization occurs in two different lithologies and locations: Type-I is present in dolostone fractures and faults as veins and veinlets, whereas Type-II occupies a fault zone between black marbles and calcschists. Sphalerite and argentiferous galena are the main ore minerals in both types. The dominant gangue minerals are quartz and dolomite in Type-I ore and calcite, quartz, and green-white fluorite in Type-II. Analysed fluid inclusion data from sphalerite, fluorite, and quartz indicate that high-temperature (>500 degrees C) mineralization was initiated from low-salinity fluids (4.3 wt.% NaCl equiv.). As temperatures dropped from 400 degrees C to 160 degrees C, the salinity of solutions increased and appreciable CO2 was contributed to the fluid system. In the absence of immiscibility, assemblages of fluid inclusions containing CO2 indicate that the solutions were homogeneous during entrapment and that mineralization took place under pressure conditions between 5 and 2 kb. Analysed delta S-34 CDT (parts per thousand) values (-1.5 and -3.8, n = 15) of sphalerite and galena indicate that the source of the sulphur is consistent with a magmatic origin for Hasbey Pb-Zn-F mineralization. The stable isotopic compositions and fluid inclusions in fluorite are also suggestive of an origin related to high-temperature, high-salinity magmatic fluids. In the region, volcanic rocks are abundant, and they document the magmatic events associated with the closure of the neo-Tethys. The timing of mineralization is restricted to post-early Oligocene, inasmuch as mineralization occurs in faults that cut post-Eocene-Oligocene thrust faults and because of the relationship between mineralization and wall-rock deformation.
Geochemical Properties and Platinum Group Element (Pge) Contents of Eastern Turkey (Van Area) Chromitite
(Tmmob Jeoloji Muhendisleri Odasi, 2011) Gunay, Kurtulus; Colakoglu, Ali Riza
Eastern Anatolia (Van) chromite deposits are associated with an east-west trending units of peridotite in the Eastern Anatolia Accretionary Complex (EAAC). The samples taken from four different areas were analyzed for their trace, major oxides and PGE contents. The average content of chromite ore as follows: Mehmetalan n=11) 45.3 wt. % Cr2O3, Mollatopuz (n=15) 31 wt. % Cr2O3, Yukaribacikh area (n=12) 43 wt.% Cr2O3 and Alabayir (n=4) 36.5 wt. % Cr2O3. The average of Sigma PGE results of same group samples contain 194 ppb, 86 ppb, 287 ppb, and 122 ppb respectively. Ir group (Ir, Os, Ru) elements show significantly enrichement compare to Pd group elements (Pd, Rh, Pt). Sigma PGE of chromitites host in ultramafic tectonits are much more abundant compared to banded chromitite host in cumulates. This results are comparable with all Turkey chromitite ore. In Yukaribalcikh area, both existence of abundant cataclastic zones in the polished sections and boudin shaped ore within shear zones contain high Sigma PGE values (e.g. Sample No:YB-CO2; 627 ppb). This enrichment indicate that multi stage of deformation may have been effected for PGE enrichment.
Geochemistry of Mafic Dykes From the Southeast Anatolian Ophiolites, Turkey: Implications for an Intra-Oceanic Arc-Basin System
(Elsevier, 2012) Colakoglu, Ali Riza; Sayit, Kaan; Gunay, Kurtulus; Goncuoglu, M. Cemal
The Late Cretaceous-Tertiary accretionary prism in Eastern Turkey includes several ophiolitic megablocks and/or tectonic slivers (Mehmetalan, Mollatopuz and Alabayir) within a melange complex, mainly comprising harzburgite, dunite and cumulate-textured gabbro. The diabases, which are the main focus of this study, cut across the ophiolites as parallel and variably thick dyke-swarms. Geochemistry of the diabases reveals three distinct groups, including a) supra-subduction zone (SSZ) type, which is characterized by marked Nb-anomaly and normal mid-ocean ridge basalt (N-MORB) like HFSE distribution, b) enriched MORB (E-MORB) type, showing some degree of enrichment relative to N-MORB, c) oceanic-island basalt (018) type with characteristic hump-backed trace element patterns, coupled with fractionated REE distribution. Among these groups, SSZ- and E-MORB-type signatures are acquired from the Mehmetalan and Mollatopuz suites, whereas OIB-type characteristics are found in the Alabayir suite. The melting models indicate involvement of both depleted and enriched sources for the genesis of the studied dykes. The close spatial relationship, similar ages (based on Ar-Ar dating) and the presence of variable subduction component displayed by Mehmetalan and Mollatopuz suites may indicate melt generation in an intra-oceanic SSZ within the southern branch of Neotethys. In spite of the solely OI8-like character of the Alabayir suite, the similar age obtained from these dykes may suggest their formation in a similar SSZ setting. Alternatively, the Alabayir suite may have represented an oceanic island or seamount formed in an intra-plate setting with or without plume influence. We suggest that decompression melting triggered by slab roll-back mechanism during the closure of the southern branch of the Neotethys during the Late Cretaceous may have been the main process that led to generation of magmas of both depleted and enriched characteristics. (C) 2011 Elsevier B.V. All rights reserved.
Geologic and Geochemical Properties of the Mafic-Clastic Type Sariseki Volcanogenic Massive Sulfide Deposit, Central Pontides, Turkey
(E Schweizerbartsche verlagsbuchhandlung, 2021) Baran, Cuneyt; Yesilova, Cetin; Gunay, Kurtulus
The Sariseki mineralization has 4.3 million tonnes of 0.47wt% Cu and is one of the newly-discovered massive sulfide formations in the Central Pontides. Mineralization occurred within deep marine sediments interlayered with mafic sills and/or lavas of the cangaldag Metamorphic Complex. The lithologic units in the area of mineralization are metamorphosed under lower-greenschist facics conditions. The metamorphism transformed deep marine sediments into phyllites, whilst mafic sills and/or lava were transformed into chlorite-actinolite schist, chlorite schist and chlorite-epidote schist. The mineral paragenesis of the mineralization is represented by the following minerals in decreasing order of abundance; pyrite, chalcopyrite, sphalerite, and magnetite. Mineralization at different levels has three different textures; banded-disseminated, semi-massive and massive. The Sariseki mineralization has maximum Cu and Zn contents of 3.4 % Cu and 0.24 % Zn, in the Cu-dominant massive sulfide formations. Within the ore, silicified relict sections of wall rock lithology and grading in the mineralized sections indicates that mineralization might have developed by sub-seafloor replacement processes. Mineralization is dominantly formed within wall rock and metamorphic rocks with elastic origin, with no feeder zones in the lower sections of massive sulfide masses, irregular lenses in mineralization and a strata-bound structure. The mafic-clastic formation of Sariseki mineralization has similar features to Besshi-type Volcanogenic Massive Sulfide (VMS), an observation that is also supported by the results of ore and wall rock geochemistry.
Geology and Geochemistry of Sediment-Hosted Hanonu Massive Sulfide Deposit (Kastamonu - Turkey)
(Elsevier, 2018) Gunay, Kurtulus; Donmez, Cahit; Oyan, Vural; Yildirim, Nail; Ciftci, Emin; Yildiz, Hayrullah; Ozkumus, Serkan
Hanonu massive sulfide (HMS) mineralization is the first sediment-hosted massive sulfide deposit discovered in Anatolia (Turkey). Containing more than 1% Cu and with more than 25 million tonnes reserve, the HMS mineralization is located in the Cangaldag Metamorphic Complex (CMC) in the central Pontides within metavolcaniclastic rocks with mafic sill and/or lava interlayers. Rocks related to mineralization were exposed to metamorphism under the greenschist facies conditions. Tectonism and metamorphic processes affected all units including ore. The HMS mineralization consists dominantly of Cu (0.2-6.9%) accompanied by Zn (239 ppm-1%) and comprises massive, banded and disseminated sulfide bodies. The main ore minerals include pyrite, chalcopyrite, with minor sphalerite and magnetite. The regular stratigraphy displaying uninterrupted layers of volcanoclastics contains mafic lava or sills within the sequence with the mineralization initially emplaced within immature clastics and then subjected to metamorphism as a package, which indicates that the ore and wall rocks formed in the same paleotectonic environment. Data obtained from melt models of mafic lava or sills related to the HMS mineralization indicate these rocks formed in back-arc basins from a mixture of 70% depleted MORE; mantle and 30% asthenospheric melt with melting degrees possibly of 8-15%. According to isotope data, lead from the HMS mineralization may be sourced from an arc-related environment, with magmatic activity in the lower crust and upper mantle. Geologic and geochemical data indicate that the HMS mineralization may have formed in a back-arc rift tectonomagmatic environment.
Geology, Geochemistry and Re-Os Geochronology of the Jurassic Zeybek Volcanogenic Massive Sulfide Deposit (Central Pontides, Turkey)
(Elsevier, 2019) Gunay, Kurtulus; Donmez, Cahit; Oyan, Vural; Baran, Cuneyt; Ciftci, Emin; Parlak, Osman; Ozkumus, Serkan
Located in the north of Anatolia, the Pontide Orogenic Belt hosts Turkey's most important volcanogenic massive sulfide (VMS) deposits. Studies completed in the last ten years have discovered new massive sulfide deposits in the Central Pontide zone. The Zeybek VMS deposit is one of these newly-discovered deposits found in the Central Pontides. This deposit is associated with the Cangaldag Metamorphic Complex occurring as east-west-striking tectonic slices. The Cangaldag Metamorphic Complex is an allochthonous mass of metavolcanic, metavolcanidastic and metaclastic rocks in the form of imbricated tectonic slices. Zeybek massive sulfide deposit is located within metaclastic rocks intercalated with mafic sills or lava flows in this complex. The major ore mineral paragenesis in the Zeybek VMS deposit comprises pyrite, chalcopyrite and sphalerite, with lower amounts of bornite, covelline, chalcocite and magnetite. With thirty thousand meters of drilling in the mineralized area, 20 million ton resources with 0.32 wt% Cu were determined. According to the wall-rock mineralization relationships, mineralization style and ore geochemistry of the Zeybek VMS mineralization, it is similar to a mafic-siliciclastic type volcanogenic massive sulfide formation. Re-Os geochronologic studies of chalcopyrites from the Cu-rich massive ore samples obtained a 178 +/- 2.2 Ma (MSWD: 4.1) Re-187/Os-188 against Os-187/Os-188 isochron. Geochemical and isotopical age data associated with the Zeybek VMS deposit indicate that the mineralization occurred in an arc-back arc tectonic environment, which developed in Middle Jurassic age intra-ocean as a result of the closure of north-ward subduction that resulted the closure of the Tethys ocean.
Spinel Compositions of Mantle-Hosted Chromitite From the Eastern Anatolian Ophiolite Body, Turkey: Implications for Deep and Shallow Magmatic Processes
(Elsevier Science Bv, 2016) Gunay, Kurtulus; Colakoglu, Ali Riza
The Eastern Anatolian Accretionary Complex includes several ophiolitic megablocks and/or tectonic slivers within a 150-180 km long east-west trending complex formed during the Late Cretaceous-Tertiary in Eastern Turkey. The Alabayir, Mollatopuz, Yukanbalcikli and Mehmetalan ophiolites are megablocks or tectonic slivers containing locally massive, nodular or schlieren banded chromitite layers. These podiform chromitites formed in mantle sequences and are classified as high-Cr chromitites (Cr# 0.63-0.88; Mg# 0.50-0.64; 0.01-0.5 wt.% TiO2; 5.7-18.8 wt.% Al2O3). Calculated parental melt compositions of these chromitites indicate boninite magma characteristics (8.2-13.4 wt.% Al2O3; 0.64-1.50 FeO/MgO). The PGE patterns also support the view that they crystallized from a boninitic melt. The total PGE contents of chromitites vary between 79 and 390 ppb. Pd/Ir ratios of chromitites vary from 0.07 to 0.28 and are consistent with an IPGE fractionated nature. The examined chromitites were divided into two groups in terms of their mineral chemistry (Group-I: Alabayir, Mollatopuz, Yukanbalcikli and Mehmetalan-I chromitites; Group-II: Mehmetalan-II chromitites). Mineral chemistry of these chromitites and their parental melt composition indicate that Group-I chromitites were probably formed at shallow mantle depths and that Group-II chromitites formed in deeper parts of the mantle. Mineral chemistry of these Eastern Anatolia high-Cr chromitites indicate that they formed not only in the deeper mantle but also in shallower parts of the MOHO transition zone. (C) 2015 Elsevier B.V. All rights reserved.