Türkiye Jeoloji Bülteni

Abstract: Büyükbelen iron ore composed of autochthonous laterites and red soils. Thin (5-10 cm) hematitic and thick (5-15 m)goethitic layers were determined in the lateritic prophile. In the small karstic cavities (1 dm -7m diameters) within the weathering zone, semiautochthonous earthy limonites and colloform goethites were deposited.Structural and textural features of the ores are controlled essentially by goethite, siliceous components (quartz, opal-CT)and hematite. Hematites usually occur as euhedral crystals agregates, while the most of the goethites are seen as bouquets offine, fibrous crystals in the crusty and botiyoidal ore textures. Lateritic iron ore includes average 49.71 % Fe2O3, 30.75 %SiO2, 3.12 % Al2Oh 0.42 % K2O, 0.11% Na2O and 0.09 % Cat).The mineralogical compositions of the parent rock (chertspelagic limestone), laterite (hematitic and goethitic layers) andred soil samples are as follow. Chert: Quartz, calcite, opal - CT, hematite, amorphous matter; pelagic limestone: Calcite,quartz, opal-CT, illite, hematite, amorphous matter; the hematitic section of the laterite: hematite, ferrihydrite, quartz, opalCT, illite, kaolinite, amorphous matter;` the goethitic section of the laterite: Goethite, ferrihydrite, quartz, amorphous matter;red soil: Quartz, opal-CT, calcite, montmorillonite, illite, amorphous matter.Geological, mineralogical, structural and textural properties and geochemistry ofBüyükbelen iron ore point that iron hasbeen derived from Upper Cretaceous aged pelagic carbonates intercalated with chert around Büyükbelen. Ore forming lateritic and partly karstic processes were effective during the Plio-Quaternary period. Goethite occurrences were resulted fromweathering of iron bearing parent rock during the wet periods. Afterwards hematites were also formed as a result of the dehydratation of goethites. 

Abstract: In this study, the magnesites of Konya region were investigated as geological,mineralogical and geochemical and accordingto this, origines and foundation conditions of the magnesites were defined. The magnesites, which are found as a result of alteration of the Upper Cretaceous serpentinites, have a cryptocrystalline texture. Magnesites are classified as primary and secondary which cut across the primary ones. While primary magnesites are harder with concoidal fracturing, secondary magnesites are softer due to the absence of silica. The formation of magnesites commenced with the emplacement of the ophiolites(Upper Cretaceous) in the region and is also continuing today. The thrusting of ophiolites over the carbonate rocks caused a temperature increase and this event led to the seperation of CO². Besides this, CO²- bearing waters of hydrotermal origin are alsoeffective in magnesite formation. These CO² -bearing waters, circulating upwards along the fractures within the serpentinites,alter the serpentinites and mobilise Mg²+ ion. During this circulation CO² and Mg2+ ion are combined and precipitated in smallfractures as stockwork ores. 

Abstract: Volcanic rocks are common constituents of the post-collisional basins that developed after the collision of the Anatolideand Pontide microcontinents. These volcanic rocks (Pazarcık volcanics) are observed in the area around Yıldızeli. Pazarcıkvolcanics are composed ofbasltic and andesitic lava flows, and their pyroclastic equivalents. Basalts show hypocrystallineporphyritic-pilotaxitic texture, and include plagioclase, clinopyroxene and olivine phenocrysts. Andesites display hypocrystalline porphyritic texture, and include the hornblende and plagioclase phenocrysts.Major element data indicate that the Pazarcık volcanics are mainly calcalkaline, and partly alkaline in character. MORBnormalized spider diagram reveals that the Pazarcık volcanics are enriched in large ion lithophile (LIL) .elements and depleted in Ti and Y. Geotectonic discriminant diagram based on the trace element data implies that the Pazarcık volcanics havewithin-plate character.Considering the mineralogical-petrographical and geochemical data together with the regional geological setting, the following model may be suggested for the evolution of the Pazarcık volcanics: The magma was formed as a result of a smalldegree partial melting of the upper mantle peridotite under the tensional regime following the period of continental collisionbetween the Anatolide and Pontide fragments. During its ascent to the surface, this magma was contaminated by thickenedcontinental crust. 

Abstract: An earthquake taken place on the western part of the North Anotolian Fault Zone around Bolu, Düzce and Kaynaşlı villages on the 12 November 1999 at 1857. The earthquake affected very large areas resulted in more than 800 deaths, left over2500 people wounded, around 1500 buildings damaged. It is notable that Bolu tunnel and viaducts were also severely damaged. According to USGS data, epicenter of the Duzce earthquake falls at 40.768 North latitude and 31.148 East longitudewhere coincides N-NE of the Çınarlı Village of Düzce. The magnitude was determined as 7.2 Ms and started at 14 km deepfrom surface. This event created about 30 km surface rupture between Gölyaka in the west and Dip village in the east. Theobserved dextral strike-slip displacement yields up to 380 cm along the eastern part of the surface rupture. The detailed mapping of surface rupture revealed at least one main and two smaller segments in a E- W trend. In addition to strike-slip offset,occasionally huge landslides of around 4-5 m, collapsed and subsided. The geometry of the surface rupture of the Düzce earthquake, elongated between Gölyaka and Dip villages, has shown a general characteristics of strike-slip faulting such as anastomosing structures, horse tails, pressure ridges and sag ponds were extensively developed along the surface rupture of Düzceearthquake. Furthermore, small scale sag ponds and liquefaction structures were determined locally along the surface rupture.

Abstract: This study which is apart of the "Melen Project" aims to using of foraminifer s and ostracods fauna, sedimentologicalfeatures and quaternary features to investigate of sedimentary environment and ecology of the sequence which was sampled fromdrill-cores in S-SW of Yeşilçay (Ağva), Yeşilçay (Ağva) creek and north of Göksu creek.

Abstract: The characteristics of the Küçükdere (Havran - Balıkesir) gold vein and wall-rock and structrural and textural specifications of the gold vein have been investigated. Gold mineralization is in aN 45° E trending vein which is hosted by a porphyryticandesite stock. According to the textural specifications, the gold vein can be classified as `andesite vein breccia`, `vein breccia`, `massive carbonate` and `banded vein`. Small open spaces, cockade, cockscomb, banded and breccia textures occurredin the vein as the type of open spacefilling textures. Banded vein is the mineralized and richest vein type. Gold and silver arethe economic metals, however Hg, As, Sb, Cu, Pb, Zn are traces in the vein. Silicification, argillization, sericitization andpropylitization are the significant alteration types for the vein and the wall-rock