An attempt to use aerial gamma‐ray spectrometry results in petrochemical assessments of the volcanic and plutonic associations of Central Anatolia (Turkey)

SUMMARY Volcanic and magmatic rocks of Central Anatolia are fairly rich in radioelement concentrations. The aerial gamma‐ray spectrometric survey data, gathered for the purpose of radioactive mineral exploration were utilized as an additional tool for the petrochemical classification of the volcanic and magmatics rocks and their environments. The survey data on acidic intrusions (e.g. granite, monzonite and syenite) have revealed radioelement concentrations to occur in wide ranges to be 2–6 wt per cent for potassium (K), 3–15 ppm for uranium (U) and 10–52 ppm for thorium (Th). The chain‐like high and moderately high potassium, uranium and thorium anomalies on acid intrusives of the entire area show a halo‐shaped feature. Locations and lithological compositions of the volcanic rocks namely lavas, tuffs, ignimbrites and basalts, appear to be reasonably effective on their radioelement concentrations. The highest potassium, uranium and thorium concentrations of the volcanic rocks are around 4 wt per cent, 10 ppm and 35 ppm, respectively. Consequently, depending on the location and composition, volcanics show a very wide range of air absorbed dose rate. The lowest rates, which vary between 10 and 120 nGy/hr, were calculated in the ophiolitic group, thick cultivated soil covering areas, particularly at the centre of the aerial survey area, metamorphosed rocks in the north and young basalts mostly in the Kayseri district. Their average radioelement concentrations were found to be very low, that is, 1.2 wt per cent, 2.3 ppm and 10 ppm for K, U and Th, respectively. Because of the accumulation of soluble uranium isotopes, air absorbed rates stemming from radioactivity of these isotopes at the vicinity of the Kozaklı hot spring reach 440 nGy/hr and exceed 150 nGy/hr at the vicinity of the Nevşehir geothermal field.