Search

This study presents the Pb isotope values of the galenas and the wall rocks related to the Pb–Zn mineralizations in the Biga Peninsula which include two different continental crusts; Sakarya Zone and Rhodope Massif. Pb–Zn mineralizations in the Sakarya fragment in Biga Peninsula have higher 207Pb/204Pb (15.677–15.710, avg: 15.688) and 208Pb/204Pb (38.895–39.000, avg: 38.935) ratios compared to the Rhodope fragment in Biga Peninsula ratios (15.650–15.709, avg: 15.668 for 207Pb/204Pb, 38.771–38.947, avg: 38.814 for 208Pb/204Pb), though the 206Pb/204Pb ratios of both crusts (Sakarya fragment in Biga Peninsula: 18.749–18.782, avg: 18.763; Rhodope fragment in Biga Peninsula: 18.750–18.839, avg: 18.802) are similar. Also, both crusts have radiogenic 207Pb/204Pb ratios indicating an orogenic source of lead. The Pb isotope ratios of the wall rocks related to the mineralizations in the Sakarya fragment were plotted in close, though different areas on uranogenic and thorogenic diagrams. Only the areas of Oligo-Miocene plutonics and Miocene volcanics, considered to be the main sources of mineralization, coincide with each other. The Pb isotope ratios of galena samples from the Sakarya fragment overlap the Permo-Triassic metamorphic rock (Karakaya Complex) area and seem to be related to the Cenozoic magmatism, both in proximity and trend, in uranogenic-thorogenic diagrams. The intense calc-alkaline magmatism occurrence that followed the closure of the Neo-Tethys Ocean appears to have played an essential role in forming the Pb–Zn mineralizations of the Sakarya fragment by leaching lead from the wall rocks. This study has utilized the Pb isotope ratios of the wall rocks related to mineralizations in the Rhodope fragment from a previous study (one sample for each reservoir). With this data, the magmatic effect on the Pb–Zn mineralizations in the Rhodope fragment is shown to be more dominant compared to those of the Sakarya fragment. In addition, through this study, it was determined that the Pb isotope ratios of two different continental crusts (Sakarya and Rhodope fragments) which came together with the Intra-Pontide suture zone followed two different trends. The Pb isotope compositions of Pb–Zn deposits in Rhodope Massif (both in the fragments of the Balkans and Biga Peninsula) were also compared in this study. According to the Pb isotope ratios, crustal thickness, and amount of the acidic rocks, the crustal materials are dominant in the western part of the massif. These findings also indicate that the western part of the massif is typical for Pb–Zn deposits whereas the eastern part of the massif is typical for the Cu–Au deposits.

The Hasancelebi deposit in eastern Turkey, with proven reserves of 95 million metric tons, is a copper-gold-bearing iron oxide deposit. It is chiefly hosted by rocks that underwent widespread sodic-calcic and potassic styles of alteration. In the Hasancelebi district, pervasive Na-Ca and K-Fe alteration types are overprinted by sericitization and by late alteration that occur in multiple, overprinting systems. The age of hydrothermal alteration and mineralization (ca. between 74-68 Ma) overlaps with the age of alkaline magmatism in the Hasancelebi district. Crystallization and cooling of alkaline magmatism is associated with hydrothermal features that spanned the duration of the district’s igneous history. The 40Ar/39Ar and U-Pb geochronology of magmatism indicate that the hydrothermal system was synchronous with diabase and syenite and/or microsyenite porphyry intrusions and consisted of several discrete phases of Na-Ca and K-Fe alteration. The oldest alteration (phase 1) formed at ca 74.4 to 74.3 Ma; it is spatially and temporally associated with the emplacement of diabase dikes and contains scapolite and phlogopite. The next younger alteration (phase 2) formed at about 71.3 Ma and is spatially and temporally associated with syenite porphyry and microsyenite porphyry intrusions. It consists of scapolite, garnet, pyroxene, and actinolite that are superimposed on the first alteration phase. The next alteration assemblage (phase 3) formed at about 68.6 Ma and consists of phlogopite 2 and magnetite mineralization. Still later alteration (phase 4) overprints phases 1, 2, and 3 and consists of sericite-quartz, chalcopyrite, hematite, calcite, fluorite, and barite. Oxygen ( δ 18O) and hydrogen ( δ D) isotope analyses were carried out on phlogopite, sericite, barite, calcite, fluorite, and quartz representing the mineral assemblage formed during phases 1 and 4 of the hydrothermal alteration. The calculated δ 18O (H2O) and δ D (H2O) composition of the fluids that formed preore K-Fe alteration and postore alteration of phase 4 range between 15.1 to 8.5 and −124 to −85.6 per mil, respectively, and partially overlap the range for traditional magmatic waters. Oxygen and H isotope compositions from alteration minerals highlight two major points: Na-Ca and K-Fe alteration assemblages are likely derived from high-temperature primary magmatic fluids, and late sericitization is likely derived from fluids exsolved from cooling alkaline plutons during hydrothermal fracturing and consequent degassing at moderate temperatures. The initial ɛ Ndi values of the alteration zones range from −2.02 to −2.08, close to the calculated ɛ Nd value of associated syenite porphyry at the time of alteration ( ɛ Nd (68.64Ma; −1.9). Nd-Sr isotope compositions combined with 40Ar-39Ar and U-Pb geochronology of the associated alteration suggest that the fluids were sourced from coeval diabase dikes and syenite porphyry and/or microsyenite porphyry intrusions. The rare earth element characteristics, 40Ar-39Ar and U-Pb geochronology of alteration and fresh magmatic rocks, δ 18O, δ D, Nd, and Sr isotope systematics together suggest that the fluids responsible for the high- to moderate-temperature assemblages are largely derived from the coeval alkaline igneous rocks (diabase and microsyenite porphyry dikes) that intrudes the sedimentary-volcanosedimentary basin.

The performance of steel reinforced concrete (RC) beams with a box cross section exposed to fire is studied. The cross-section is divided into an appropriate number of segments so that non-uniform temperature profiles and variations of constitutive relationships across the section can be represented accurately. The temperature distribution in the cross-section is calculated by the finite difference method. The nominal moment capacity of RC beam is obtained using equilibrium of forces in the segments of beam. Advantage of circulating cold water and cover concrete on the nominal moment capacity under fire is examined. Results obtained by the prepared computer program were found to predict the fire resistance and performance of RC box beams well.

Biga Yarimadasi’nin dogusunda yer alan Kalkim (Yenice) beldesinin guneyinde bulunan Handeresi, Bagirkacdere ve Firincikdere yataklari Turkiye’deki onemli Pb-Zn±Cu yataklari arasinda yer almaktadir. Bolgedeki distal Pb-Zn skarn olusumlari, Kalabak Formasyonuna ait epidot-serizit-grafit sist ve metakumtaslari ile kalk sist ve mermer dokanaklarinda ve/veya bunlarin kirik-catlaklarinda meydana gelmis olup, hem litolojik hem de yapisal kontrollu cevherlesmelerdir. Bolgede yapilan calismalar sirasinda endoskarn zonuna rastlanilmamis olup, eksoskarn zonunda gorulen mineraller, grossular-andradit turu granatlar, Mn-hedenberjit-johansenit (cok nadiren diyopsit) turu klinopiroksenler, aktinolit-tremolit turu amfiboller (cok nadir), epidotlar, kuvars (kuvars-I) ve kalsittir (kalsit-I). Cevher mineralleri olarak ise galenit, sfalerit, pirit, kalkopirit, arsenopirit, manyetit ve hematit saptanmistir. Gerek cevherli zonlari gerekse de tum yan kayaclari kesen ve damar dolgusu seklinde gozlenen ayri bir kuvars (kuvars-II) ve kalsit (kalsit-II) jenerasyonu da belirlenmis olup bunlar cevher icermeyen gec evre olusumlaridir. Klinopiroksen, sfalerit, kuvars-I ve kalsit-II ornekleri uzerinde yapilan sivi kapanim calismalarinda klinopiroksen minerallerinin 300-340 oC (% 5,6 ile % 8 arasi NaCl esdegeri tuzluluk), sfalerit minerallerinin 272-338 oC, kuvars-I minerallerinin 157-319 oC (% 1,4 ile % 9,1 arasi NaCl esdegeri tuzluluk) ve kalsit-II minerallerinin 68-75 oC arasinda olustuklari saptanmistir. Kapanimlarin cok kucuk olmalari sebebiyle sfalerit ve kalsit-II minerallerinden tuzluluk olcumleri yapilamamistir. Cevherlesme ile iliskili kalsit (kalsit-I) minerallerinde yapilan C-O izotop analizleri sonucunda δ13CVPDB degerlerinin ‰ -3,9 ile ‰ 0,6 arasinda, δ18OSMOW degerlerinin ise ‰ 1,82 ile ‰ 12,76 arasinda yer aldiklari gorulmustur. Tum veriler bir arada degerlendirildiginde, bolgedeki bu olusumlari meydana getiren akiskanin olasilikla magmatik kokenli oldugu ve yaklasik 340 oC veya uzerindeki bir sicaklikta (prograd-retrograd evre gecisi) meydana geldigi sonucuna varilabilir. Sicakligin dusmesi ile birlikte, ilk olarak olusan klinopiroksenlere kuvars-I mineralleri de eslik etmistir. Sicakligin yaklasik 300 oC altina dusmesi (retrograd evre) ile meteorik sular sisteme katilip tuzluluk degerlerinin dusmesine sebep olmuslardir. Cevherlesme ise yaklasik prograd-retrograd evre gecisinden itibaren olusmaya baslamis ancak esasen retrograd evrede meydana gelmistir. Yapilan C-O izotop calismasi ile de cevherlesme ile iliskili kalsitlerdeki karbonun kokeninin oncelikle magmatik oldugu ancak cevherlesmenin ilerleyen evrelerinde yan kayaclardaki rekristalize denizel kirectaslarinin da karbona kaynaklik ettigi, oksijenin ise yine magmatik kaynakli oldugu ancak ilerleyen evrelerde meteorik su etkisi ile oksijen izotop degerlerinin degistigi saptanmistir

Biga Yarimadasi’nin KB ucunda ve Canakkale ili Lapseki ilcesi dogusunda yer alan Cataltepe Pb-Zn±Cu±Ag yatagi, Kretase yasli Camlica metamorfitlerinin mermerleri icinde ve onlarin diger kayaclarla olan dokanaklari boyunca genellikle litolojik kontrollu olarak gelismis bir cevherlesmedir. Su an aktif olarak uretim yapilan isletme alaninda cevherlesmelerin genel dogrultu/egimi mermer ve diger metamorfitlerin genel dogrultu/egimine uyumlu olup yaklasik K40oB/40oKD’dur. Mikroskobik calismalar prograd evreye ozgun granat ve piroksen minerallerinin varligini ve bu minerallerin retrograd evrede karbonatlasip epidotlastigini gostermektedir. Cevher mineralleri olarak kahverengi sfalerit, bal renkli sfalerit, galenit, kalkopirit, pirit, pirotin, valeriit, manyetit, hematit, markazit, arsenopirit ve limonit mineralleri izlenmektedir. Retrograd evre sirasinda gelisen cevherlesmeler dokusal olarak masif dokulu cevherlesmeler ve sacinimli dokulu cevherlesmeler olmak uzere iki gruba ayrilmakta ve masif dokulu cevherlesmeler sacinimli dokulu cevherlesmeler tarafindan kesilmektedir. Bu cevher minerallerine karbonat, klorit ve kuvars mineralleri eslik etmektedir. Gec evre alterasyonlar baslica manganoksit-hidroksit, limonit, karbonat ve kalsit mineralleri ile temsil edilmekte olup prograd ve retrograd evre alterasyonlarini maskelemektedir.Calismalar sirasinda elde edilen veriler, Cataltepe Pb-Zn±Cu±Ag yataginin mermer-metakumtasi/kuvarsit dokanaklari boyunca ve esas olarak mermerler icinde bir magmatik etki ile evrimlesen cevherli cozeltilerden itibaren olustuguna isaret etmektedir. Ayrica veriler, sicaklik bakimindan mezo-epitermal kosullarda olusan distal Pb-Zn skarn yataklarina gore biraz daha sig kesimlerde ortaya cikmis epijenetik bir yatagi onermektedir