Anomalous Behavior of Zirconium and Hafnium in Volcanic Fumarolic Fluids

AbstractThe Zirconium and Hafnium concentrations in worldwide fumaroles fed by magmatic fluids reveal that the Zr/Hf ratio is inversely related to the temperature of emission. Lower Zr/Hf ratio values below the chondritic signature are found in fluids having the highest temperature while super‐chondritic Zr/Hf ratio values are found in lower temperatures. Sub‐chondritic values of the Zr/Hf ratio may be related to larger volatility of Hf‐chloride gas species with respect to Zr‐Cl gas species, while super‐chondritic ratios may correspond to fluid‐rock processes resulting from cooling of uprising magmatic fluids. We propose that sub‐chondritic Zr/Hf ratio values in fumaroles associated with high temperature may be an appropriate marker of fast magmatic rising representing a new sensitive tool for volcanic risks strategies.