Zircon U–Pb ages and Sr–Nd–Pb–Hf isotopic compositions constrain the tectono-magmatic evolution of the Anomaly 21-A iron ore region, Bafq metallogenic province, Central Iran

The late Proterozoic - early Paleozoic tectono-magmatic evolution of Central Iran is considered to be a result of subduction of the Proto-Tethys Ocean and the amalgamation of Gondwana continental fragments. Here, we present whole-rock geochemistry, Sr-Nd-Pb isotopes and zircon U-Pb-Hf data for monzonite to quartz monzonite from deep drill core in the area of the Iron Anomaly 21-A, Bafq metallogenic province of Central Iran, to decipher the petrogenetic evolution of the mantle during late Proterozoic–early Paleozoic times. The plutonic rocks display enrichment in large-ion lithophile elements (Rb, Ba, K, and Cs), and depletion in high-field-strength elements (Nb, Ta, Ti), typical of continental arcs. Zircon U-Pb ages of the studied rocks are in the range of 474–512 Ma, which is consistent with the general consensus on the age of the Cadomian basement of Central Iran, and the culmination of subduction along northern Gondwana in the early Paleozoic. The isotopic signatures of the samples, e.g., (87Sr/86Sr)i = 0.706 to 0.718, εNd(t) = -3.3 to +1.8, (206Pb/204Pb)i = 18.87 to 20.32, (207Pb/204Pb)i = 15.72 to 15.84, (208Pb/204Pb)i = 40.74 to 42.32, and εHf(t) = -4.7 to +11.6, cover a compositional range of mantle-derived melts with variable degree of contamination by Neoproterozoic continental crust. A setting of back-arc continental rifting is envisaged for the late Neoproterozoic to early Paleozoic magmatism in the Bafq province.