The behavior of rare-earth elements, zirconium and hafnium during magma evolution and their application in determining mineralized magmatic suites in subduction zones: Constraints from the Cenozoic belts of Iran

Abstract

Processes, such as partial melting, differentiation, assimilation, magma mixing, and liquid immiscibility, together with partition coefficients between minerals and melt, solubility, and redox conditions, are the controlling parameters for element distribution and enrichment processes. These factors can be evaluated through the geochemical variation of trace elements, such as Rare Earth Elements (REEs) and High Field Strength Elements (HFSEs), specifically Zirconium (Zr) and Hafnium (Hf), in magmatic rocks. For this purpose, two well-mineralized Cenozoic subduction-related magmatic belts in Iran—the Arasbaran and the Urumieh-Dokhtar—were evaluated. The results of this study showed that, in subduction zones, the increase in crust thickness with arc maturity caused low partial melting and more differentiation, which left behind magmas with low Zr, Hf and HREEs. These factors can be used to evaluate the degree of differentiation, degree of partial melting, and the correlation of different magma pulses, from initiation to the end of the subduction processes. Using Zr-Hf or Hf-(Zr/Hf) diagrams, we concluded that low Zr and Hf contents with low Zr/Hf ratios without a Europium (Eu) negative anomaly, and with high LREE/HREE ratios, indicated the more evolved and mineralized magmatic suites, which occurred particularly in the mature arcs.