GEOTHERMAL WATER CHEMISTRY OF ARMUTLU PENINSULA, TURKEY

This study concerns chemical features of the Armutlu Peninsula geothermal outlets. The E-W trending region stretches into the Marmara Sea (ca. 117 km E-W by 45 km N-S). The peninsula is selected not only for being an active seismic region with controlled North Anatolian Fault Zone (NAFZ) which traverses with two branches bounding to the north and the south the region but also for explicit changing in physical parameters.

Geologically, three distinct zones, northern, central and southern, can be distinguished. Northern and central zones of the region are dominated by metamorphic assemblages. Metamorphic rocks belong to these zones overlie late Mesozoic to late Tertiary succession. The southern zone is typified by a thick sedimentary succession formed during the early-late Mesozoic and Tertiary. All three zones have, as a common cover, some detrital units. Besides, a granitic mass intruded into metamorphic rocks.

From the standpoint of geothermal water chemistry, magmatic and metamorphic rocks mainly act as reservoir rocks. In addition springs issue from fractures of magmatic and metamorphic rocks exclusive of Yalova thermal springs, and they are distributed all around the peninsula. Physical parameters vary 5.98 to 7.33 for pH, 14.2 °C to 70.5 °C for temperature (T), 382 µS/cm to 2710 µS/cm for electrical conductivity (cond.). In order to perform water-rock interaction, affecting chemical processes on water and sketching conceptual model of the region, water samples were collected in the field, former chemical results published by different authors were used and chemical analyses were carried out by ICP-MS. The results of the chemical analyses were plotted into Piper and Schoeller diagrams for depicting water types. Solute geothermometers and saturation indices were used to compare and estimate the host rock temperature with different methods.