Alteration, mineralization, geochemistry and fluid inclusion study of the Firouzeh mine, NW Neyshabour

The Firouzeh mine is located in the Northwest of Neyshabour in the Khorasan Razavi province, Northeast of Iran, and eastern side of the Quchan- Sabzevar Cenozoic magmatic arc. Widespread magmatic activity in the Quchan-Sabzevar arc, is spatially and temporally associated with several types of mineralizations such as IOCG, Cu-Au porphyry and Kiruna types (Ghiasvand et al., 2016; Karimpour et al., 2011; Fatehi, 2014; Zarei et al., 2016). The aim of this investigation is to provide an understanding of the geology, alteration, mineralization, geochemistry, fluids evolution and genesis of the Firouzeh mine. Two hundred and fifty thin and polished sections were prepared for microscopic study. Twenty-nine samples were analyzed by X-ray fluorescence (XRF) method at the laboratory of Zar Azma company, Tehran, Iran. Twenty-one samples were analyzed by the X-ray Diffraction (XRD) method at the laboratory of Kansaran Binalood company, Tehran, Iran. Sixty samples were selected for 55- elemental analysis by composition of ICP-AES (Inductively coupled plasma atomic emission spectroscopy) and ICP-MS (Inductively coupled plasma Mass Spectrometry). Moreover, Sixty samples were selected for Au analysis by Aqua Regia Digestion at the SGS Laboratories, Canada. Six doubly polished sections of quartz mineralization were prepared for microthermometric analysis. Homogenization and last ice-melting temperatures were measured using a Linkam THMSG 600 combined heating and freezing stage at the Ferdowsi University of Mashhad. The Firouzeh mine contains various Middle- Eocene subvolcanic rocks as dykes which have intruded into Paleocene-Eocene volcanic rocks. Important altrations consist of silicified, argillic and carbonate among which silicified is the most extensive. Primary minerals are magnetite, specularite, pyrite, chalcopyrite and bornite and secondary minerals are hematite, alunite, covellite, turquoise and limonite. Mineralization has occurred in the cracks and fractures at the surface and in tunnels, mainly as disseminated, stockwork, vein-veinlet and hydrothermal breccia. Geochemical explorations showed anomalies of copper (up to ppm 1074), gold (up to ppb 699), iron (up to over percent 30), cerium (up to ppm 464), lanthanum (up to ppm 227), uranium (up to ppm 243) and cobalt (up to over ppm 10000) that has many similarities with IOCG type deposits (Corriveau, 2007; Zamora and Castillo, 2001; Marschik et al., 2000). Fluid inclusions are relatively simple liduid+vapor types, with homogenization temperature from 147 to 278ºC and average temperature of 203ºC and Salinity containing 5.56 to 17.08 wt. percent NaCl equiv. which has resulted from fluids with KCl, CaCl2, MgCl2 and NaCl compositions. Mixing process between hot and saline fluid with cold and low saline fluid and also, boiling process can caused deposition of elements. Firouzeh mineral deposit has magmatichydrothermal source and is related to tertiary magmatic activities of subduction of Neothetys Sabzevar oceanic crust beneath the Turan crust. Fluid mixing has played an important role for precipitation during mineralization and includes the source of hot and saline magmatic fluids with high contents of metallogenic elements and the mixing with cold and low saline meteoric waters resulting in the formation of deposit (Bastrakov et al., 2007; Simard et al., 2006; Wilkinson, 2001; Beane, 1983). Based on geological characteristics, alteration, mineralization, geochemistry, geophysics and fluid inclusion studies, Firouzeh mine is a great mineralization of iron oxide copper-gold-U-LREE which has similarities to the hematite-dominant section of Olympic Dam IOCG deposit. Acknowledgments: The Research Foundation of the Ferdowsi University of Mashhad, Iran, supported this study (Project No. 3/18303). We would like to thank the Iranian mineral processing research center and laboratories of Zar Azma, Kansaran Binalood, ACME and SGS. We also thank rural cooperation of Firouzeh mine for its liaison in field survey.