Türkiye Jeoloji Bülteni

Abstract: Petrographic and microtextural features of the metamorphic rocks cropped out in the Marmara Island indicate that they have three identifiable metamorphic phases (Mj, M2, M}). The first two phases (Mj, M2) form the parts of a single progressive regional metamorphic cycle. The last phase (M3) represents the retrograde metamorphism. Typical mineralogical changes in the metamorphics delineate that the degree of metamorphism increases from north to south. Based on these mineralogical changes, three metamorphic fades zones have been distinguished. These are greenschist, epidote-amphibolite and amphibolite fades. These fadeszones generally run parallel to the trend of the D2fold axis in the ENE-WSW direction. By determining the formational conditions ofindex minerals, it is found out that the progressive regional metamorphism occurred beneath a magmatic arc at pressures between 3and 6 kbar and temperatures between 400 and 600°C. Under these conditions, the rocks have undergone four phases of deformation,synchronous with the regional metamorphism. 

Abstract: The studied area is located 4 kms N-NW of Doğanşehir township in Malatya province. The units of the studied area (from theoldest to the youngest) are; Permo-Triassic Malatya Metamorphics, Upper Cretaceous Berit Group, Upper Cretaceous PolatGranitoid, Middle Eocene Maden Complex, Pliocene Beylerderesi Formation and Quaternary talus and alluviums. Theplutonic rocks(tonalite, diorite) of Polat Granitoid intruded during the Upper Cretaceous effected the Malatya Metamorphics (marble, crystalizetlimestone) and skarn rocks with Fe mineralizations formed as contact-metasomatic at this contact. Fe mineralizations have usuallybeen together with skarn rocks.The skarn formations have developed inform of endoskarn and exoskarns. While endoskarn formations are represented by garnetand epidote skarn rocks, exoskarn formations are represented by garnet, garnet-epidote, epidote-garnet and epidote skarn rocks. Themineral assemblages of the skarn rocks are as garnet (andradite, grossularite), epidote, pyroxene (diopsite,ferrosalite, hedenbergite),plagioclase, K-feldspar (orthoclase), amphibole (hornblende), scapolite (meionite), calcite, quartz, chlorite, magnetite and sphen.The mineralizations occur along the marbles-plutonics contact, in the pockets and fractures extending towards marble. Thethickness of mineralized bodies can reach up to 5-10 m. The main mineral of mineralizations is magnetite. Hematite, specularite,limonite, pyrite, chalcopyrite, malachite and azurite are in less amount, and, covellite and chalcosite are rare.

Abstract: In the Şükrüpaşa area studied, the rocks are made up of Mesozoic limestones, schist, calc-schist, and metasandstones which unconformably overlay a basement of metagranitic rocks and the intrusive rocks of Cretaceous age. The Şükrüpaşa intrusion forms apart of the Srednogorie -Istranca granitoid chain identified as the island- arc type plutonism.The mineralization in the study area occurs as pirometasomatic type in the contact zone between the intrusive and sedimentary cover rocks, and as disseminated, fine vein, and stuckwork types in the calc-alkaline magmatic rocks, mainly including granodioriteand tonalite. Major ore minerals are pyrite, chalcopryrite, molybdenite, and scheelite. Primary magnetite, bornite, pyrrhotite, Bi-minerals, sphalerite, galena, enargite, neodigenite, arsenopyrite, ilmenite, ilmenomagnetite, rutile, anatase, and psilomelane and secondary chalcocite, covellite, malachite, azurite, limonite andgoethite accompany to these minerals. The average contents of Cu and Moare 0.41 percent and 0.08 percent respectively and it was determined that the most important mineralizations are in associated withthe contact zone.

Abstract: Beidellite is a dioctahedral smectite mineral, which contains principally (Al) ions in octahedral site. Beidellite mineral was foundin the Ayvacık bentonite deposits, which were formed within Miocene volcanic rocks. In the Ayvacık region; volcanic rocks are composed of mainly highly fractured andesite, trachyandesite and highly porous tuffs. In the study area, hydrothermal solution sascended through the fracture systems and altered volcanic rocks to bentonite. During bentonitization, beidellite mineral was occurred as an alteration product of plagioclase in andesitic rocks and vitric tuffs. X-ray diffraction data indicate an unusually ordered layer stacking arrangement of beidellite. Minor amount ofillite, halloysite, kaolinite and cristobalite were determined during X-ray diffraction analysis of clay size.

Abstract: The K-rich metavolcanites of Kadınhanı (Konya) have undergone low grade metamorphism characterized by sericitization, chloritization and albitization. The rocks are transitional between alkaline and tholeiitic, trachyandesite in composition and havewithin-plate lava characteristics. They are extremely K-rich (6.5-11.1 wt. % K2O) and show also strong enrichments in LILE andLREE, implying possibly an enriched source. In addition, depletion in Nb indicates the presence of a subduction component in magmagenesis. These enrichments probably occurred in the source region prior to magma generation. The parental magma of the rocks wasformed in an extensional regime and derived from subcontinental lithosphere involving a small amount of subduction component. Their mantle source was geochemically capable of supplying the K-rich material.

Abstract: The rock units, observed in the area from bottom to top, are the Permo-Triassic Tokat Massif, Late Jurassic-Early CretaceousFerhatkaya and Carcurum formations of Amasya Group, Middle Eocene Çekerek formation and Mio-Pliocene Kemerkaş formation.Tokat Massif is represented by phyllites, marble, metavolcanites, metasediments and mica schists.Amasya Group, which overlies Tokat Massif with an unconformity, is composed of Ferhatkaya and Carcurum formations on thebasis of its lithologic and fades properties. Ferhatkaya formation starts with a thin layer of conglomerate derived from metamorphicmaterials. The formation is composed mainly of limestones except lower levels. In places brecciated fabric and often oolitic andpseuodooolitic fabrics are seen. Carcurum formation is, generally, composed ofclaystone and mudstone layers in lower levels, whilelimestones with chert layers and lenses occur in upper levels. Çekerek formation is divided in three members. These are, from bottom to top; Kozluca, Kuzualan limestone and Göynücekagglomerate members. Kozluca member generally consists of pebblestone, sandstone, mudstone, clay stone and marl alternationKuzalan limestone member contains limestone lithology with high amount of Nummulites sp. fossils in some levels. Göynücekagglomerate member is composed of a matrix made of volcanic materials and basalt and andesite pebbles-blocks. In this unit,silicificated wood, metamorphic rock fragments, recrystalized limestone and limestone blocks, mudstone and clay stone lumps andcoal seams are commonly observed.Kemerkaş formation overlying Çekerek formation with an angular unconformity, is composed mainly of alternating conglomerateand pebblestone-rough sandstone, mudstone, gypsum interlayers and travertines.

Abstract: This paper concerns the determination of stress tensor from a set of striated faults and of focal mechanisms of earthquakes. The central and occidental parts of the North Anatolian Fault Zone illustrates the applied methodology. Then, temporal changes intectonic regimes of the central North Anatolian Fault Zone are briefly examined. The fault kinematics analysis within central North Anatolian Fault shows that strike-slip stress changes from transpressional regime to transtensional regime as indicated by chronologies of fault slip vectors. Both states have consistent NW- and NE- trending o) and O3 axes respectively, but havesignificantly different mean R values: Rm=0.75 for transpressional and Rm=024 for transtensional regimes respectively. Theinversion of focal mechanisms, occurred in the central and occidental parts of North Anatolian Fault Zone, shows that actual stress rejime is transtensional and is characterized by a NW-(N126°E) trending a} and a NE-(N217E) trending a3 axes with a R value of0.40. The stress changes along the North Anatolian Fault Zone result from the coeval influence of forces acting in the west and in theeast. However, the timing of the temporal stress change permits to suggest that Quaternary stress regime variation in central North Anatolian Fault Zone is mainly due to the Aegean domain influence.

Abstract: CFC (cholorofluorocarbon) gases of atmospheric origin have been used as groundwater age-indicators since the late 1980s. CFCages of groundwater samples from Aladağ karstic aquifer have been determined to range between 7-8 to 25 years. Comparison ofcalculated CFC ages with the physical and chemical properties of groundwater indicates a strong positive correlation. Moreover, thetritium and CFC composition of groundwater along the regional flow path have been found to vary harmoniously.

Abstract: The studied mineralizations are situated at 10 km south of Çüngüş (Diyarbakır) and 500 m north of Derdere Village. The research area contains three different Hthologies. These are Jurassic-Lower Cretaceous Koçali Complex, Eocene Midyat Group and Lower Miocene Fırat Formation. The Koçali Complex which bears the mineralizations, presents a cross section ofophiolitic suite, while the position of ophiolites is upside down and contains serpentinite, gabbro, diabase, spilitic basalt and pelagic sediments.The mineralizations are placed within the top units of the ophiolitic suite and inside the spilitic basalt. The mineralized bodiesare either lense shaped or stratiform. The position of ore is N50°W/55° NE, 4-5 m thick and around 50-60 m long. The observed oreminerals are pyrite, chalcopyrite, sphalerite, covellite-chalcocite and baryite.The chemical analyses of ores show that the Cu and Zn contents are promising. It is also observed that there are good positive correlations between Cu-Mn, Cu-Fe, Cu-Zn, Au-As, Au-Sb, Au-Ag, Ba-Mg; but negative correlations between Cu-Ag, Fe-Cd, Cu-Cd.The Derdere mineralizations which are placed in the upper levels of ophiolitic suite which itself is a section of oceanic crust,exhibit the general features of Cyprus Type massive Sulphide Ores. These mineralizations are quite different from the Eocene Cumineralizations of Southeastern Thrust Belt; studied mineralizations are Jurassic-Lower Cretaceous aged and openly situated inophiolitic litholigies (Eocene aged Cu mineralizations do not show any open relationship with ophiolites).

Abstract: Tokuş formation which is the basal sediments of the Sivas Tertiary Basin and play a key role on its geological evcfution, was first described by Yılmaz and Özer (1984). Its age was regarded as Lutetian-Priabonian and it was thought to be deposited in shallow marine environmental conditions. Detailed geological map of the units, two measured stratigraphical columnar section; stratigraphie, paléontologie and sedimentalogic features of the formation were examined, therefore new aged data and depositional conditions have been defined in this study. The fossils Alveolina cucumiformis Hottinger and Nummulites solitarius (A) de la Harpefound in the lower part indicate llerdian stage, fossils Alveolina cuspidata Drobne, Alveolina ruetimeyeri Hottinger, Nummulitesformosus de la Harpe Assilina cf. dandotica Davies indicate Cuisian stage. According to this data the age of the formation is yieldeddown to llerdian. The dominant fades of the unit from bottom to top and in a recurrent manner are alluvial fan, coastal, neritic andslope fades. Thickness of the formation shows thinning and thickening from place to place caused by the dominant regional thrust tectonics.