Browsing by Author "Colakoglu, Ali Riza"

Now showing 1 - 7 of 7

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 and Mineralogical Characteristics of Fe-Ni Laterite Ore of Saricimen (caldiran-Van) Area in Eastern Anatolia, Turkey
(Tubitak Scientific & Technological Research Council Turkey, 2009) Colakoglu, Ali Riza
The Saricimen Fe-Ni laterite ore is located 15 km east of Caldiran County, northeast of Lake Van. This area is situated in the eastern Anatolia accretionary complex of Turkey, close to the Iran boundary. It is the first transported Fe-Ni rich laterite to be described from this area. This paper concentrates on the mineralogical and textural features of the ore minerals and the transported Fe-Ni laterite zone. These transported laterites are very inhomogeneous and contain very abundant zoned chromite grains, which have been altered to magnetite. SEM/probe investigations indicate that Fe-Ni is depleted in the core chromite and increases in the magnetite rim. A sedimentary transported laterite zone exhibits a high proportion of silcretes and ferruginous materials and chemically contains 29-61wt% SiO2 and 11.8-48.7 wt% Fe2O3. The average contents of Al2O3, TiO2, MnO and P are 4.81, 0.37, 0.32, and 0.03 (all in wt%) respectively. The highest Ni value obtained from the transported lateritic ferruginous zone is 1.16 wt%. The Pt and Pd concentrations are low, ranging from 39 ppb to 6 ppb and 21 ppb to 5 ppb, respectively. The Au value reaches up to 3 ppb. The diversity in chemical compositions of transported laterites is related to fracturing, erosion, corrosion, transportation, quantity of clastic material with different alteration history and diagenesis.
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.
Geology and Isotope Geochemistry (c-O of the Diyadin Gold Deposit, Eastern Turkey: a Newly-Discovered Carlin-Like Deposit
(Elsevier Science Bv, 2011) Colakoglu, Ali Riza; Oruc, Mahmut; Arehart, Greg B.; Poulson, Simon
Diyadin mineralization is the first reported gold deposit located in a collisional tectonic environment in Eastern Anatolia. The mineralization is related to N-S and N10-20 degrees W-trending fault systems and hosted within the Paleozoic metamorphic basement rocks of the Anatolide-Toride microcontinent. Calc-schist, dolomitic marble and Miocene and Quaternary volcanic rocks comprise the exposed units in the mineralized area. Geochemical signatures, alteration types and host rock characteristics of the Diyadin gold deposit resemble those of Carlin-type deposits. Mineralization is constrained by alteration of overlying volcanic rocks to younger than similar to 14 Ma (K-Ar). Carbon and oxygen stable isotope measurements of carbonate rocks were made on six drill holes (n = 81) with an additional four samples of fresh carbonate rocks from surface outcrops. Background carbonate rocks have delta C-13(V-PDB) similar to 1.8 parts per thousand. and delta O-18(V-SMOW) similar to 27 parts per thousand. Isotopically-altered host rock samples have decreased delta O-18 (down to similar to+11.4 parts per thousand) and variable delta C-13 (from -3.6 to +4.8 parts per thousand). Postore carbonate veins and cave-fill material have distinctly different isotopic signatures, particularly carbon (from delta C-13 = +8.4 to +9.8 parts per thousand). Whether this post-ore carbonate is simply very late in mineralization associated with the gold system, or is a completely different, younger system utilizing the same pathways, is unclear at present. Within the host rock sample set, there is no correlation between gold and delta C-13, and a weak correlation between gold and delta O-18, indicative of water-rock interaction and isotopic alteration. Both the isotopic data and structural mapping suggest that the main upflow zone for the deposit is near the northern portion of the drill fence. Additional data at multiple scales are required to clarify the relationship(s) between fluid flow and mineralization. (C) 2011 Elsevier B.V. All rights reserved.
The Petrogenesis of Saricimen (caldiran-Van) Quartz Monzodiorite: Implication for Initiation of Magmatism (Late Medial Miocene) in the East Anatolian Collision Zone, Turkey
(Elsevier, 2010) Colakoglu, Ali Riza; Arehart, Greg B.
The Saricimen porphyry is exposed as a sub-volcanic pluton within the Upper Cretaceous ophiolitic rocks in East Anatolian Accretionary Complex. The pluton is quartz monzodioritic in composition consisting of feldspar, hornblende, and biotite phenocrysts set in a fine-grained matrix. Major element geochemistry indicates the pluton is of high-K, calc-alkaline, metaluminous character, with a low (0.81-0.90) Aluminum Saturation Index (ASI). Trace element and sulfur isotope geochemistry suggests that the Sancimen porphyry was mantle-derived and contaminated by crustal materials during ascent. Tectonically, this and related volcanic and plutonic rocks in eastern Turkey and Iran are subduction-related and comprise the earliest documented neotectonic igneous activity associated with the final closure of the neo-Tethys between the Arabian and Eurasia plates at similar to 14-13 Ma. (C) 2010 Elsevier B.V. All rights reserved.
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.