What Caused the High Radiation Levels in Plio-Quaternary Volcanic and Pyroclastic Rocks Used as Building Raw Materials in Isparta Volcanic Field, SW Turkey?

Abstract

Available natural radioactivity ( 40 K, 238 U, 232 Th) measurements on Plio-Quaternary volcanic and pyroclastic rocks, which are usually used to as building raw materials, from the Isparta region of SW Turkey, released that their radium equivalent activity values are close to the internationally accepted upper limits and a potential radiation risk. Here, to deciphere the what caused the high radiation values in these volcanic materials carrying value by more than three times the equivalent materials in Turkey, the relationship between their magma and source characteristics has been investigated. Recent volcanological studies have shown that potassic-ultrapotassic magmas governed the genesis of the Isparta volcanism. K-rich character’s and elevated concentrations of radiogenic (e.g.,Th and U) and total rare earth elements (∑REE) are their most diagnostic features. These characteristics are also similar to some mantle-derived carbonatites (e.g., Norwage and Kenya) with high radiation levels. To support this, recent investigations also revealed that the origin of Isparta potassic volcanism is associated with a common and enriched mantle source, which were interacted with carbonatite melts. Accordingly, carbonatitic melts left their geochemical imprints into their mantle sources, and partial melting of this mantle source produced K, REE, Th, and U-rich volcanic materials with high radiation levels in the region. These results indicate that the carbonatite-influenced mantle source were played a key role for not only enrichments in distinct (e.g., Th, U and REE) elements but also high radioactivity levels in Isparta volcanic and pyroclastic rocks. Here, attention is drawn to the fact that a potential risk of high radiation in volcanic and pyroclastic rocks used as building raw materials can be expected for a given volcanic region, which include potassic magma derived from a carbonatite-modified mantle source.