Yazar "Yigit, Ozcan" seçeneğine göre listele

Listeleniyor 1 - 6 / 6
  • [ X ]
    Öğe
    A prospective sector in the Tethyan Metallogenic Belt: Geology and geochronology of mineral deposits in the Biga Peninsula, NW Turkey
    (Elsevier, 2012) Yigit, Ozcan
    The Tethyan Metallogenic Belt (TMB), extending from Europe through Anatolia to Iran, is one of the world's major metal producing belts, and consists of many sectors. Mineral deposits of the Biga Peninsula in northwestern Turkey exhibit, in many ways, the characteristics of mineral deposits found throughout the belt. Biga Peninsula tectonically forms the westernmost part of the Sakarya Zone and easternmost part of the Rhodope Zone at the intersection of Gondwana and Laurasia. The Biga Peninsula metallogeny research and exploration project created a GIS inventory of mineral deposits and prospects, and classified them genetically to evaluate the mineral deposit potential using genetic models based on descriptive data. The GIS database, consisting of 128 deposits or prospects, helped to generate new prospects and potential prospects. This field-based study indicated that the Biga Peninsula forms a prime target for gold-copper exploration not only in Turkey but in the world. The current economically significant mineral deposits of the Biga Peninsula were shaped by Cenozoic calc-alkaline magmatism, ranging between 52 and 18 Ma, and related to mainly collisional and post-collisional tectonic regime. Epithermal Au-Ag deposits including high-(HS), low-(LS) and intermediate-sulfidation (IS) styles, porphyry Au-Cu-Mo and base-metal skarn systems are economically the most important. Though there are no currently economic examples of some of them in the Biga Peninsula, other deposit types include Carlin-like distal disseminated Au-Ag, orogenic Au, especially listwanite hosted, volcanogenic Mn and U, lateritic (ferricrete) Fe deposits, carbonate replacement (CR) and placers. Several active metal mines, such as Balya, Arapucandere and Koru, are operating in the Biga Peninsula. Kucukdere Au-Ag deposit in Balikesir is the only gold mine in the Biga Peninsula, except for by-product gold produced from base-metal deposits. Results of the study show current total gold endowment of the Biga Peninsula including reserves and/or resources is 9.18 Moz gold [284.2 t] contained in twelve different deposits. Of these only 6 contain significant gold [>0.3 Moz or 10 t]. Halilaga porphyry and Agi Dagi and Kirazli HS epithermal systems have an ongoing resource estimate, and Halilaga is a candidate to be one of the largest Cu-Au deposits not only in the Biga Peninsula, but in Turkey. Currently newly discovered Tepeoba is the largest porphyry Cu-Mo-Au deposit with known resources in the Biga Peninsula. Here, the first(40)Ar/Ar-39 step-heating age data conducted on some of the major HS epithermal gold deposits and causative intrusives in the Biga Peninsula are reported. Geochronological results from this project, evaluated with previous studies, indicate at least 3 phases of porphyry and 2 phases of high-sulfidation epithermal gold mineralization in the Biga Peninsula. The most important mineralizing phases and related host rocks for gold mineralization range from 38 to 22 Ma. The Oligocene is especially important for economic epithermal and porphyry systems in the Biga Peninsula, which is comparable to deposits in the Oligo-Miocene Serbomacedonian-Rhodope metallogenic belt of the Balkan Peninsula in SE Europe. (c) 2012 Elsevier B.V. All rights reserved.
  • [ X ]
    Öğe
    Discovered and undiscovered gold endowment of Turkey: a quantitative mineral resource assessment using GIS and rank statistical analysis
    (Springer, 2012) Yigit, Ozcan
    An assessment of the discovered and undiscovered gold endowment of Turkey, a prolific sector in the Tethyan Metallogenic Belt, is developed from a comprehensive Geographic Information System database containing 402 gold deposits and prospects. The majority of the gold deposits and prospects are epithermal, porphyry, volcanic-associated massive sulfides, orogenic gold, and skarn systems. These five major deposit types form more than 90% of the known gold deposits and prospects. Just 87, corresponding to 21.6%, of the deposits and prospects in the data set have current calculated gold reserve and/or resources, containing a total of 54.885 Moz Au. Current gold reserves of the country are 21.447 Moz constituting 39.1% of the total gold resources, of which 17.1 Moz gold are contained in four deposits. Out of these 87 deposits and prospects, only 27 contain significant gold reserve and/or resources (defined as equal to or more than 0.32 Moz or 10 tons Au), and contain 91.8% of the total gold endowment of the country. The cumulative frequency distribution model of the gold endowment of Turkey abides by log-normal distribution. Observed and estimated 10th, 50th (median), and 90th percentiles of the data are 0.0046 Moz [0.0045 Moz estimated], 0.1030 Moz [0.0875 Moz], and 1.4969 Moz [1.6938 Moz], respectively. The 99th percentile of the data is 7.6444 Moz [18.9636 Moz]. The arithmetic mean of the known gold endowment is 0.657 Moz and the Swanson mean size is 0.492 Moz. The arithmetic mean of the 27 significant gold deposit or prospects is 1.94 Moz. Zipf's law estimates of the undiscovered (residual) gold resources of Turkey are based on the current size of the largest, rank 1, gold deposit of Turkey, which is the Kisladag porphyry deposit that has 17.481 Moz gold endowment (including past production). Zipf's law estimates a total of 88.261 Moz natural or total gold endowment, 57.133 Moz or 65% of which has already been found. This predicts at least 31.128 Moz residual or undiscovered gold resources to be found in Turkey, though the lack of full delineation of the rank 1 deposit, Kisladag, means that this figure is very conservative.
  • [ X ]
    Öğe
    Geology and geochemistry of jasperoids from the Gold Bar district, Nevada
    (Springer, 2006) Yigit, Ozcan; Hofstra, Albert H.; Hitzman, Murray W.; Nelson, Eric P.
    Gold Bar is one of several Carlin-type gold mining districts located in the Battle Mountain-Eureka trend, Nevada. It is composed of one main deposit, Gold Bar; five satellite deposits; and four resources that contain 1.6 Moz (50 t) of gold. All of the deposits and resources occur at the intersection of north-northwest- and northeast-trending high-angle faults in slope facies limestones of the Devonian Nevada Group exposed in windows through Ordovician basin facies siliciclastic rocks of the Roberts Mountains allochthon. Igneous intrusions and magnetic anomalies are notably absent. The Gold Bar district contains a variety of discordant and stratabound jasperoid bodies, especially along the Wall Fault zone, that were mapped and studied in some detail to identify the attributes of those most closely associated with gold ore and to constrain genetic models. Four types of jasperoids, J(0), J(1), J(2), and J(3), were distinguished on the basis of their geologic and structural settings and appearance. Field relations suggest that J(0) formed during an earl event. Petrographic observations, geochemistry, and delta O-18 values of quartz suggest it was overprinted by the hydrothermal event that produced ore-related J(1), J(2), and J(3) jasperoids and associated gold deposits. The greater amount of siliciclastic detritus present in Jo jasperoids caused them to have higher 6180 values than J(1,2,3) jasperoids hosted in underlying limestones. Ore-related jasperoids are composed of main-ore-stage replacements and late-ore-stage open-space filling quartz with variable geochemistry and an enormous range of delta O-18 values (24.5 and -3.7 parts per thousand). Jasperoids hosted in limestones with the most anomalous Au, A, Hg, +/-(As, Sb, T1) concentrations and the highest delta O-18 values are associated with the largest deposits. The 28 parts per thousand range of jasperoid delta O-18 values is best explained by mixing between an O-18-enriched fluid and an O-18-depleted fluid. The positive correlation between the sizes of gold deposits and the delta O-18 composition of jasperoids indicates that gold was introduced by the O-18-enriched fluid. The lowest calculated 6180 value for water in equilibrium with late-ore-stage quartz at 200 degrees C (-15 parts per thousand) and the measured delta D value of fluid inclusion water extracted from late-ore-stage orpiment and realgar (-116 parts per thousand) indicate that the O-18-depleted fluid was composed of relatively unexchanged meteoric water. The source of the O-18-enriched ore fluid is not constrained. The delta S-34 values of late-ore-stage realgar, orpiment, and stibnite (5.7-15.5 parts per thousand) and barite (31.5-40.9 parts per thousand) suggest that H2S and sulfate were derived from sedimentary sources. Likewise, the 613 C and 6180 values of late-stage calcite (-4.8 to 1.5 parts per thousand and 11.5 to 17.4 parts per thousand, respectively) suggest that CO2 was derived from marine limestones. Based on these data and the apparent absence of any Eocene intrusions in the district, Gold Bar may be the product of a nonmagmatic hydrothermal system.
  • [ X ]
    Öğe
    Gold in Turkey - A missing link in Tethyan metallogeny [Ore Geology Reviews 28, 147-179] - Reply
    (Elsevier Science Bv, 2007) Yigit, Ozcan
    [Anstract Not Available]
  • [ X ]
    Öğe
    Mineral Deposits of Turkey in Relation to Tethyan Metallogeny: Implications for Future Mineral Exploration
    (Soc Economic Geologists, Inc, 2009) Yigit, Ozcan
    The Tethyan metallogeny of Turkey, shaped by the interplay between subduction, collision, postcollision, and rifting processes, is mainly associated with Late Cretaceous to Cenozoic volcanoplutonic and ophiolitic rocks. A wide spectrum of ore deposits is represented from those occurring in island arcs to those associated with continental settings. Though Turkey has been one of the leading producers of chromite, the country is an emerging producer of precious and base metals. This assessment of the metallogeny of Turkey is based on a comprehensive GIS database compilation that contains known mineral deposits and prospects with relevant descriptive data. The data set contains information on major deposit types of economic importance such as porphyry, skarn, epithermal including both high-and low-sulfidation, polymetallic volcanic-associated massive sulfide (VMS) deposits including both Kuroko and Cyprus types, podiform chromite, lateritic nickel, carbonate-hosted lead-zinc with nonsulfide zinc including sedimentary-exhalative (SEDEX) and Mississippi Valley type (MVT), karstic and lateritic bauxite, orogenic gold including both mesothermal and listwanite-hosted types, and placer deposits. Well known deposit types that are less well represented in the database include sediment-hosted Cu, Carlin-type gold, iron oxide copper-gold (IOCG), and detachment-fault related gold systems. Exploration programs in the last two decades have started to reveal the true mineral potential of the country. Turkey is an underexplored country by today's standards, with a large prospective area with a wide spectrum of mineral deposits reflecting the diverse geological environments that are present. Turkey is the least well explored portion of the Tethyan belt, which hosts Au and Cu endowments comparable with the Andes and the southwest Pacific metallogenic belts.
  • [ X ]
    Öğe
    Recent Discoveries and Exploration Trends in Turkey
    (Irish Assoc Econ Geol, 2007) Yigit, Ozcan
    Modern exploration programs, mainly by multinational exploration and mining companies, in the last two decades have revealed the mineral potential of the ancient land of Turkey. The country became a gold producer in 2001, previously the only gold produced in Turkey was a by-product from base-metal mines. Currently the country has two active gold mines, Ovacik and Kisladag and more metal mines in development, such as Copier, Efemcukuru, Mastra, Cerattepe, Caldag and Madenkoy. In terms of industrial minerals Kazan and Beypazari mines will begin production of trona soon. Buoyant metal prices, amendment of the mining law in 2004 as well as economic stability have attracted more major and junior exploration and mining companies into Turkey. The main exploration and development focus has been precious- and base-metals, especially gold and copper, though industrial minerals attracted some mining giants. Porphyry copper-gold, epithermal gold and volcanic-associated massive sulphide deposits are the main exploration interests while carbonate-hosted lead-zinc deposits, especially non-sulphide zinc, are other targets. Recent advancements in mining technology have attracted companies' attention to low-grade lateritic nickel deposits of the country.