İzmir-Ilıkpınar Sıcak ve Mineralli Sularının Hidrojeokimyasal İncelenmesi

Abstract

The aim of this study was to determine the origins of hot and mineral waters in and around the Ilıkpınar Geothermal Area (Deliömer Village-Ancient Roman Baths) and to explain their relationship with cold water resources and to clarify the geothermal system to which they are connected. For this purpose, geological, hydrogeological and hydrogeochemical studies were carried out. The study area, which is approximately 35km south of Izmir, is located in the northeast of Menderes District and west of Seferihisar District. To the south of the area is the Gulf of Kuşadası. There are Paleozoic metamorphics known as Menderes Massif in the study area that don’t seen on the surface around the study area. The Triassic-Upper Cretaceous Cycladic Zone overlies the Paleozoic Metamorphics. This unit is overlain by the Upper Cretaceous-Paleocene Bornova Flysch. The Miocene sedimentary rocks are unconformably overlain the metamorphic units. Domes related to Upper Miocene-Pliocene rhyolitic volcanism are observed in the region. The rhyolite-rhyodacite lava domes are units with heat source in the region and they are heating rocks. The overlying rock is the impermeable clayey deposits of the Yeniköy Formation and the impermeable schists of the Bornova Flysch. The reservoir aquifer units are marble and crystalline schists that gains secondary permeability tectonically within the Menderes Massif and the Cycladic Zone, thick sandstones between the secondary porosity within the Bornova flysch and the limestone levels of the Yeniköy Formation. Three geothermal areas have been identified around the rhyolite and rhyodacite lava domes in the study area and its vicinity. Those are; Akyar-Kızılcaağaç-Dikmen-Kovukluardı Geothermal Area, Ilıkpınar-Pilav Tepe Geothermal Area and Cumalı Tuzla Geothermal Area which is outside the study area. It is observed that Kızılcaağaç-Dikmen-Kovukluardı springs, which are in the first of the geothermal areas mentioned in previous studies, have dried up during the rainy and dry period of sample collection. In this area, only Akyar Spring is a natural discharge source at a temperature of 36°C with a flow rate of ~ 0.5-1 l/s. The geothermal area of Ilıkpınar-Pilav Tepe is represented by the source of Deliömer (Ancient Roman Baths) and with a flow rate of ~ 1-2 l/s, the temperature of the flowing source is approximately 32°C in both periods. Cumalı Tuzla Geothermal Area (Doğanbey Thermal Springs) is located just outside the study area, just south-west. The natural discharge here lies along a wide line and consists of tens of sources, each with a flow rate of ~ 3-5 l/s. Natural flow sources are approximately 70-75 °C. The temperature and flow rate of the spring here is higher than the springs in the study area. In order to understand the factors that cause this difference, a sample was also taken and evaluated. In this study, the geothermal resources in the mentioned geothermal areas feeding system, circulation and their relations with each other are tried to be determined by hydrogeochemical evaluations. In this context, water chemistry analyzes (Major ion and stable isotope) were completed by taking samples from hot and cold water sources determined in and around Ilikpinar. According to the major ion analyzes, the water samples in the field are Ca/Na-HCO3 type. The Doğanbey spring is different from the waters in the study area with water type of Na-Cl. According to trace element analysis, arsenic was determined between 10,48 ppb and 117,6 ppb in some of the waters in the field and it is above the 10 ppb limit value determined by the World Health Organization for drinking water. The hot water samples in the study area are of meteoric origin and represent a similar recharge area. No significant oxygen-18 or evaporation change was observed in hot waters. The tritium content of hot water sources are close to zero. While rivers and rainwater samples have values close to current tritium levels (4-7 TU), hot and mineral water samples have very low tritium contents. This is due to the fact that the groundwater residence time is relatively long (> 50 years).