Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Uz. Bektas ¹, Fahri Esenli ¹, Senel Ozdamar ¹, Vildan Esenli ¹, Fikret Suner ¹

Affiliations
1 Istanbul Technical University, Department of Geology, Maslak, 80626, Istanbul, TR

Abstract

The geological and chemical compositional heterogeneties of the two different types of bentonite occurrence, from the Hoylu and Caltumar areas in Fatsa of Ordu province (NE Turkey), were discussed in terms of silica polymorph structure The Hoylu occurrence was formed by means of in situ alteration, the Caltumar bentonite was deposited within a volcano-sedimentary sequence and it has undergone diagenetic process The samples of both areas contain smectite and opal (cristobalite/tndymite) as the main minerals Feldspar, quartz and calcite are the other minerals observed in the Caltumar samples while the latter two minerals are not observed in the Hoylu samples The cristobahtcs in Caltumar samples have strongly ordered microstructure and high crystalhnity The d-spacings of 101 line (4A band) of these enstobahtes are lower than 4 07A and these silica polymorphs were identified as opal C But the opals from the Hoylu samples have disordered microstructure and probably rich in trydimite layers The d values of 4A band of these opal-CT are higher than 4 08 A.

Keywords

Structural ordering, Bentonite, Opal-C Opal-CT, Silica polymorphs, Ordu Provinces, NE Turkey.

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Tolga Yalcin ¹, Fikret Suner ¹, Werner Balderer ², Erkan Bozkurtoglu ¹

Affiliations
1 Technical University of Istanbul, Dept.of Geology, 80626, Maslak, Istanbul, TR
2 ETH-Zurich Ingineurgeologie, Honggerberg, CH

Abstract

Due to movement of active North Anatolian Fault Zone in the Marmara Region the two main shocks, which were epicentered on Golcuk - Izmit, and Duzce on August 17,1999 and November 12,1999 respectively, created the chemical changes on thermal waters of Bursa, Adapazari, Yalova and Kuzuluk - Adapazari geothermal areas, which are close to the active fault zone. Field measurements and chemical analyses of these waters from that date to September, 2000 have revealed considerable temporal changes. The trace element contents exhibited variations, particularly as an increase of Pb, Cu, and Ni levels, and a decrease of Fe, Mn, Zn contents after the earthquake. These analyses also collected in 2000 showed that, all 'these changes were temporary and became nearly normal during 2000.

Keywords

Earthquake prediction, Thermal Waters, Geochemistry, Heavy Metal, Marmara Region, Turkey.

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Ali Haydar Gultekin ¹, Fikret Suner ¹, Yuksel Orgun ¹, Mustafa Kumral ¹

Affiliations
1 Istanbul Technical University, Department of Geology, 80626, Maslak, Istanbul, TR

Abstract

The southeastern part of the Anatolian Peninsula hosts a large number of ore deposits that retain well-preserved sedimentary and magmatic textures connected with their origins. The whole region has undergone extensive deformations and high-grade metamorphism during the Alpine Orogeny. From oldest to youngest, the known metallic and non-metallic deposits are scatted over a large area in various litho-units in the inner part of the Eastern Taurus fold belt of southeastern Turkey. Most of them are small deposits and their age of mineralization ranges from Palaeozoic to Tertiary. The metallic ore deposits were formed as a result of the evolution of the Eastern Taurus fold belt in the Alpine tectonic system. This belt is rnainIy constituted of ophiolite and blueschists of the upper Cretaceous-Oligocene age. The ultramafic and mafic members contain Iarge chromite deposits of podiform type and Cyprus-type massive sulphide deposits. The most important example of the massive sulphide deposits is in Ergani, Elazig, as sea-floor pyritic copper sulphides within the ophiolite complexes. The Keban Pb-Zn deposit is another metallic occurrence as vein and cavity fillings in breccias, and stockworks in the pneumatolytic-hydrothermal stage of the intermediate and acidic magmas indicating a backarc environment. Replacement of the country rocks by higb-temperature hydrothermal solution has also resulted in some non-metallic ore bodies emplaced especially within firnestones, the main examples of which are the phosphate and asphaltite occurrences at Mazidag and Sirnak respectively, ranging in the stratigraphical scale from Cambrian to Quaternary. These formations are metamorphosed to gneiss, schist, phyiitte, and marble in the greenschist or arnphibolite facies in many places. The main economic occurrences of metamorphic massifs are apatite-rich iron deposits and several epithermall mesothermal veins along the main faults.

Keywords

Chromite, Massive Sulphide, Phosphorite, Asphaltite, Eastern Taurus Fold Belt, Southeastern Anatolia, Turkey.

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Fikret Suner ¹, Fahri Esenli ¹, Bektas Uz ¹, Vildan Esenli ¹, A. Haydar Gultekin ¹

Affiliations
1 Istanbul Technical University, Department of Geology, 80626, Maslak, Istanbul, TR

Abstract

Pattern of REE distribution in various types of magnesite ore occurring within the Late Cretaceous ultramafics in Orhaneli Region (Western Anatolia) were studied to interpret their genetic significance. The samples were classified into three different groups viz. massive, lentiform and pignolite or stockwork. Individual groups exhibit distinctly different REE distribution pattern with variable Eu, Ce and Yb anomalies. Three types of REE distribution patterns are recognizable with the following characteristics: (1) high LREE/HREE ratios without having Ce and Eu anomalies, (2) similar LREE and HREE abundance with uncertain positive and negative Eu and Ce anomalies, and (3) low REE abundance with markedly positive Eu, negative Ce and slightly negative Yb anomalies. It is postulated that the redox conditions in the primary mineral formation system was subjected to change and as a result, subsequent mobilization followed by recrystallization took place in the formation of primary magnesite minerals. Although a low temperature environment is indicated for magnesite formation, it is possible that REE-Poor solutions derived from the fluid-Rock interaction had caused mobilization and later recrystallization of magnesite ore.

Keywords

Geochemistry, Magnesite, Massive, Lentiform, Pignolite, Stockwork, Sparry, Rare Earth Elements, Turkey.

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