Rare Earth Elements in the Aqueous Phase of Mud Volcanoes of the Kerch-Taman Region

Abstract

This work presents original data on the contents and distribution of major and rare earth elements in the waters from 26 mud volcanoes within the Kerch–Taman region. In terms of the chemical composition, the studied mud volcanic waters are the Na–Cl and Na–HCO₃–Cl types. However, the Cl/Br, Na/Cl, and Y/ Ho ratios indicate three main genetic groups of volcanoes. It was found that the contents of the rare earth elements in the aqueous phase of mud volcanoes are low (fractions of μg/L) and are distinguished by negative cerium anomalies and positive europium and holmium anomalies. The highest REE concentrations are observed in the mud volcanoes located within the oldest Cretaceous sediments in the area of fault influence. As the distance from the Mesozoic source ΣREE dramatically decreases, it was revealed that the free CO₂ content in the aqueous phase regulates the REE content in waters and the cerium and europium anomalies.