General aspect of different barite occurrences in the east of Istanbul, Turkey

Barite occurrences east of Istanbul (NW Turkey) are compared major mineralogical and geochemical properties, and identified depositional origins. Sile barite occurrence, which is near Blacksea, north east of Istanbul, is alternated with Triassic sandstone. Petrographic observations reveal that barite grains are found out in the sand stones. Chemical analyses are conducted on eighteen samples via AAS (Atomic Absorption Spectroscopy) equipment for detection of Cu, Zn, Pb, Sr, Cd and Ni concentrations. Because of a vein shape, the occurrence is evaluated as a hydrothermal origin. However, microscopic studies, low Pb, Zn and Sr concentration and the presence of arkose show that the barite is formed by sedimentary. Gebze barite occurrence is near Marmara Sea south east of Istanbul. Barite is located in the weakness zone between Silurian - Lower Devonian limestones and Lower Devonian fossiliferous shales as a vein or veinlet. This type of barite is considered that is formed under the control of hydrothermal solutions and barium rich circulation fluids. Microscopic investigations show that coarse grain barite crystals are intersected with micro barite fractures. Geochemical investigations are performed on nine samples for detected to the trace element (Cu, Zn, Pb, Sr, Cd and Ni) concentrations via AAS (Atomic Absorption Spectroscopy) equipment. Due to higher than 1.5-2% Sr/SrSO4 ratios, irregular Pb, Zn, Cu and Ni concentrations in barite and host rock with Ba and Sr contents support hydrothermal presence in the mineralization.