Abstract: The Bor region of Serbia has a long history of mining and abundant mineral resources. The Jama copper deposit is
located in the Bor region and belongs to the Timok mining area. To investigate the genesis and mineralization significance of the host andesite in the Jama deposit, we analyzed its zircon U-Pb ages, trace elements, and Hf isotopes. LA-ICP-MS zircon U-Pb age is approximately 86 Ma in the Late Cretaceous. Calculated Ti-in-zircon temperatures range from 663 ℃ to 806 ℃ (average 724 ℃ ), and zircon oxygen fugacity shows that the log fO2=-14.86--7.60 (average-11.07), ΔFMQ=+2.11-+7.62 (average +5.04), suggesting magmas with relatively high oxygen fugacity and low crystallization temperatures. The andesite is characterized by high εHf(t) value (+12.6-+16.5), and young second-stage model ages (TDM2=88-344 Ma). Based on the trace element characteristics of
zircon, the andesite was formed in an active continental margin arc environment and magma genesis was linked to partial melting of the depleted mantle wedges metasomatized by the subducted plate fluids. Synthesizing our findings with prior research on regional tectonic-magmatic evolution, we propose that the Jama andesite was formed in an active continental margin arc during the northward subduction of the Vardar oceanic plate. The late Cretaceous rollback of the subducted plate likely triggered back-arc extension, facilitating the ascent of oxygen-rich mantle-derived magma and subsequent diagenesis and mineralization.

Key words: Serbia, Jama deposit, andesite, zircon trace element, zircon Hf isotope