An Approach to Determine of the Formation Stages of Volcanism Using Natural Gamma-Ray Spectrometer from Geophysical Methods (Example of Gölcük Volcanism)

Abstract

Gölcük Caldera is in the Isparta Angle, which is an interesting tectonic structure in Southwest Anatolia. This caldera is formed as a result of back-arc volcanism associated with the northward subduction zone of the African plate under the Eurasian Plate during the Tertiary. It attracts the attention of many researchers with its tectonic and volcanic structure. In this article, the results of in situ natural gamma radiation measurements made in the caldera are evaluated. In the study, radioactive element (Potassium (%K), Uranium (eU), and Thorium (eTh)) contents of volcanics were measured in situ with the portable gamma-ray spectrometer, which is effectively used in Geophysical Engineering. The changes in natural gamma radiation of alkaline volcanic are presented with maps. When these maps are examined, it is understood that K%, U-ppm and Th-ppm concentrations of Gölcük volcanic are higher than the world average values. The high potassium concentration draws even more attention. The high potassium content indicates that the local volcanic are ultrapotassic and contain lithospheric materials. In addition, since the radioactive element concentration will reflect the magmatic development, the volcanic stages in the region have been tried to be determined. The number of these stages was determined from the curves of the radioactive data from a purely geophysical engineering (numerical) point of view, and the study area was interpreted as consisting of three different phases. This finding is supported by the results of the articles on the aging studies of the samples taken as a result of observations. In addition to these, the ranges of radioactive elements belonging to these stages were determined.