Güzelyurt Resurgent Caldera - Cappadocia, Türkiye: The Origin of Gördeles Ignimbrite and Its Geothermal Potential 

Abstract

Turkey hosts various types of volcanic rocks in different areas due to evolving volcanic activity from the Miocene to the present. The Cappadocia region is one of the most prominent areas in these regions. In this study, geological and volcanological data, along with samples obtained through the anisotropy of magnetic susceptibility method (AMS), were used to determine the potential source area of Gördeles ignimbrite (ca. 6.3 My), a Miocene-aged ignimbrite found in the Cappadocia region of Central Anatolia. As a result of field observations, the Gördeles ignimbrite was divided into Lower and Upper Gördeles separated by a paleosoil layer. To the west of Güzelyurt, the largest pumice diameter was found to be 72 cm, while the lithic diameter was 33 cm in the ignimbrite. Near the village of Kayırlı, a lag breccia measuring 30 m in thickness was identified just below an 8m pyroclastic flow unit. The lag breccia contains pumices and andesites with a diameter of 70 cm. To determine paleoflow directions, 130 core samples were taken from 25 locations of the ignimbrite, and 2448 magnetic measurements were conducted using the anisotropy of magnetic susceptibility method. According to our AMS analyses, the paleoflow directions around the Güzelyurt area are distributed radially. Our magnetic fabric data, combined with field and stratigraphic information, suggests that the source area is located near Güzelyurt. The source area (the Güzelyurt resurgent caldera) spans roughly 9x9 km, and its highest point is about 2000 m. The pre-caldera lavas, situated on the eastern side of the caldera, have an elevation of about 1800 m. The caldera's lowest point is at an elevation of 1330 meters. Based on these measurements, the total subsidence amount is estimated to be 500 meters, which indicates the discharge of around 31 km3 of magma. The eruptions occurred in multiple stages and were explosive in nature. After the caldera collapse, the caldera floor rose up, forming a resurgent dome. A graben system was formed on this structural dome consist of marble and granite, reaching a height of 1900 m. Different types of alterations occurred on the edges of grabens and where the dome resurges. Intensive alteration zones have been identified within the ignimbrites in the caldera, particularly around the resurgent dome. The Güzelyurt resurgent caldera in Central Anatolia has significant geothermal potential due to geological events. The Narlıgöl maar, located just north of the resurgent dome towards the caldera boundary is a source of known geothermal potential. There are hot water and gas outlets in the maar, and geothermal facilities are operated on the northern flank of the maar. . Multiple gas emissions have been identified both inside and outside the Güzelyurt caldera, and an important geothermal field is also located just outside of the southern caldera wall (Bozköy Village). Detailed research about volcanism, especially in different regions of Anatolia, particularly in Central and Eastern Anatolia, is of great importance for increasing and revealing Turkey's geothermal energy potential.