Studies On The Petrogenesis And Genesis Of Porphyry-Type Mineralisation Of The Sungun And Masjed Daghi Deposits In The Urmieh-Dokhtar Magmatic Arc,Iran

The Ahar-Julfa/Arasbaran metallogenic belt is located in the Urmieh-Dokhtar magmatic Are of the central part of the Tethyan metallogenic belt.The Masjed Daghi and Sungun porphyry deposit in Iran is located in the north-western part of the Ahar-Julfa metallogenic belt,in which the porphyry deposits have not been sufficiently studied.This paper is based on the Eocene porphyry from the Masjed Daghi porphyry deposit and the Miocene Sungun porphyry Cu–Mo systems,with the aim to deepen the understanding on the metallogenic background and magmatic environment of the Urmieh-Dokhtar magmatic Are.We used infrared spectroscopy,raman spectroscopy,electron probe microscopic analyzer(EPMA),whole-rock major-and trace-element analyses,and zircon trace element and U-Pb-Lu-Hf isotope analyses to clarify the formation setting,oxygen fugacity,water content and other characteristics of the ore-forming magma.Zircon U-Pb dating of the Masjed Daghi porphyry yielded Eocene(54.1±1.5 Ma)age and positive?_Hf(t)ratios(+4.5?+13.5),with T²_DMages of 260 to 841 Ma.The rocks have high K₂O(4.9 wt.%)and Sr(120?122 ppm)but low Y(5 ppm)contents.In addition,the porphyries have high zircon Ce⁴⁺/Ce³⁺ratios(152?543),and their plagioclase has high Al content.The Sungun samples were rich in large-ion lithophile elements and poor in high-field-strength elements;moreover,they presented both high K₂O(2.4?3.5 wt.%)and Sr(727?770 ppm)and low Y(11?14 ppm)contents.The zircon U–Pb age of the Sungun porphyry was between 19.12±0.45 and 19.75±0.67 Ma,with positive?_Hf(t)ratios(6.5?11.7)and young T_DM²ages between322 and 705 Ma.Additionally,the Sungun high-Sr/Y porphyries contained anhydrites(Ca SO₄);and had high zircon Ce⁴⁺/Ce³⁺ratios(33?728),relatively low zircon saturation temperatures(620?804°C),and plagioclases with excess Al content.Such evidence indicates that the Eocene Masjed Daghi porphy-ries have water-rich and high-O fugacity features,and were generated from mafic magma upwelling during subduction,and a water-fluxed melting of the subduction-modified juvenile lower crust might have generated a high oxygen fugacity,leading to the formation of the hydrous and S-rich Sungun fertile magmas.