فصلنامه زمین شناسی اقتصادی
سال سیزدهم شماره 4 (پیاپی 31، زمستان 1400)

The widespread Cenozoic magmatic assemblages in Iran host a variety of ore deposits including porphyry Cu-Mo-Au, skarn type ores, and epithermal base and precious metals deposits. Silicic zones of variable sizes are common in the Kerman belt in the southern section of the Urumieh-Dokhtar arc, and some might be representing the upper parts of porphyry copper systems known as lithocap. To investigate this potential relation, a silicic zone in Meideh, north Pariz, is studied. The silicic zone lies in an area with several known porphyry copper deposits (PCD) including Sarcheshmeh, Nochun, Seridun, Sarkooh, and Bagh-Khoshk. For comparison, silica ledges and veins in Seridun and a mineralized silica vein system to the east of the Sarcheshmeh mine are also studied.

The study is based on field studies and investigation of textures and structures, and sampling for mineralogy (microscopic and X-ray diffraction analysis), and fluid inclusions. The XRD analyses were accomplished in the Iranian Mines and Mining Industries Development and Renovation Organization (IMIDRO) and Kansaran Binaloud Co, Tehran. The fluid inclusion studies were performed in the Iranian Mineral Processing Research Center (IMPRC) using a Linkam THMS600 equipped with a Zeiss microscope.

The silicic zone in Meideh is developed in andesitic lava flows and pyroclastic materials, and covers an area of ~ 1 km2. Silica occurs in white to grey colors and in massive, brecciated and locally vuggy textures; the grain sizes range between 0.01mm to 1mm. The silica is locally associated by minor sulfides (pyrite and locally chalcopyrite) carbonates, and clay minerals.The silicic zone grades outward into a silicic-argillic halo and into the host volcanic rocks with propylitic alteration. Chemical analysis of samples from the zone indicated enrichments in Cu, Mo, Ag, As, Bi and Au relative to the average composition of intermediate-mafic volcanic rocks in the Kerman belt. Small outcrops of a quartz-tourmaline rock occur in the southeast of the silicic zone.In Seridun, silica ledges and veins occur in the periphery and in the upper parts of a porphyry copper deposit developed in Miocene shallow intrusive bodies and older volcanic rocks. In east of Sarcheshmeh, several N-S striking silica veins locally containing pyrite, chalcopyrite, malachite, and Fe-oxides/hydroxides occur in Cenozoic volcanic and intrusive host rocks. In both areas, the silicic zones are products of pervasive silicic alteration, and occur in massive, breccia, and vuggy textures. Vuggy texture is well developed in Seridun. XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun.Fluid inclusions in quartz from all three areas are dominated by two-phase liquid-vapor. Homogenization temperature (TH) varies between 140-263 oC (average: 202 oC) for Meideh, 195-320 oC (average: 247 oC) for Seridun, and 140-264 oC (average: 177 oC) for east of Sarcheshmeh. Salinities vary between 0.18-5.71 (average: 1.62), 1.22-4.18 (average: 2.27), and 0.7-3.39 (average: 1.57) wt.% NaCl eq., respectively. The quartz-tourmaline rock from Meideh is distinguished by the occurrence of liquid-vapor-halite±hematite and liquid-vapor-opaque inclusions, in addition to liquid-vapor inclusions. The TH and salinity for the liquid-vapor inclusions, homogenizing to liquid, varies, respectively, between 202-269 oC (average: 231 oC) and 3.71-7.16 (average: 5.43) wt.% NaCl eq. The TH and salinity for the halite bearing inclusions, homogenized by halite dissolution, varies between 240-480 oC (average: 345 oC) and 33.40-56.90 (average: 42.80) wt.% NaCl eq.

The textures, structure, and spatial relations with the host volcanic rocks suggest that the Meideh silicic zone developed as a result of pervasive silicic alteration, rather than open space filling. Textures indicative of open space filling, including crustification and symmetric banding, are absent in Meideh. The silicic ledges in Seridun, and the N-S striking silicic zones in east of Sarcheshmeh, are the products of pervasive silicic alteration of the host volcanic and intrusive rocks.The XRD analysis of representative samples from Meideh indicated the occurrence of kaolinite and illite, in addition to quartz. Minerals characteristic of advanced argillic alteration (i.e. alunite, pyrophyllite, diaspore and andalusite) are missing. The minerals, however, were identified in Seridun. Fluid inclusions in quartz from the three silicic zones are dominated by two-phase liquid-dominant L-V inclusions. No distinction in salinity can be made between the three zones; Seridun, however, is distinguished by higher homogenization temperature. The local quartz-tourmaline zones in Meideh developed from distinctly higher temperature and salinity fluids (240-480 oC and 33.9-64 wt.% NaCl eq., respectively). A comparison of fluid inclusion data with several epithermal base and precious metals systems in the Urumieh-Dokhtar arc and elsewhere in Iran suggest that no meaningful distinction can be made between barren (i.e. Meideh, at current exposure level) and productive epithermal systems.Our data indicate that the silicic zone in Meideh cannot be considered as a porphyry-related lithocap at current exposure. The quartz-tourmaline rock developed from fluids of higher salinity and temperature suggests a link with magmatic-hydrothermal systems and warrants further investigation.

The Neyshabour Turquoise Mine is located at 55 km North West of Neyshabour in latitude of E58◦, 23ꞌꞌ and longitude of N36◦, 23ꞌꞌ. This area is situated at the Cenozoic continental magmatic arc in the north of Sabzevar ophiolite sequence and extends to Binalood Mountains (Spies et al., 1983; Karimpour and Malekzadeh Shafaroudi, 2013). Rock units consist of Eocene intermediate volcanic and intrusive bodies and breccia's which are the country rock of ore deposits in the Firouzeh area (Mohammad Nejad et al., 2011a). The Turquoise Mine was suggested as the first Iron Oxide Cu-Au-U-LREE mineralized system in Iran (Karimpour et al., 2012). The turquoise was formed on the oxidation zone of this deposit. The mining procedure operates as underground mining and mine wastes that were recycled for extraction of turquoise were released in the vicinity of the mine area and the surrounding Madan village. High radiometric anomaly of Uranium and Thorium has been reported in the Firouzeh area (Karimpour and Malekzadeh Shafaroudi, 2013). The aim of this study is to study the gamma radioactivity of 238U, 232Th, and 40K in different parts of this area (tunnels, rock units, mine waste, habitations and water resources) and to determine the origin of gamma radioactivity by gamma spectroscopy implement via portable gamma scintillation system (MCA) with sodium iodide NaI (Tl) detector.

The total average natural gamma radioactivity in the mine tunnels was measured to be 98.31 cps. The average gamma radioactivity associated with 238U in the tunnels was 5.2 cps. The average gamma radioactivity associated with 232Th (1.4 cps) in all samples from the tunnels is less than 238U. Highest natural gamma radioactivity associated with 40K was measured in the mine tunnels. Trachyte rock units and the Limonitic soils had the maximum natural total gamma radioactivity and andesite unit shows the least values. The high concentration of these elements in limonitic soils was formed by adsorption of radioactive cations by Fe Oxides. The lowest gamma radioactivity was determined in andesite rock units, coarse grain alluvium and coarse grain soils. Mine wastes from the turquoise mine are explored again by villagers and this might cause exposure to additional dose in this way. The average total gamma radioactivity is 75.26 cps in mine wastes. The highest and lowest gamma radioactivity in the mine waste was associated with 40K and 232Th, respectively. There is a high gamma radioactivity in homes that have been made by local raw materials. Average total gamma radioactivity in rural houses is 83.73 cps. The maximum and minimum total gamma radioactivity was associated with 40K and 232Th, respectively. There is high natural gamma radioactivity in mine drainage waters and springs that which occur on marl unit. The mine tunnels had the most gamma radioactivity and stream sediments show the lowest gamma radioactivity in different samples in the area. 238U, 232Th and 40K radio activities have strong positive relationships and they probably have a similar source. 40K has the most gamma radioactivity in this region. Therefore, trachytic rocks are the source of natural gamma radioactivity in the studied area. Based on mineralogical studies on Neyshabour turquoise mine (Mansouri Gandomani et al., 2020), there are no radioactive elements in Turquois mineral. There are not reliable statistics on occupational diseases and cancer among miners because these patients are sent to Mashhad hospitals or migrate from this area. However, the number of people infected by lung disease such as pneumoconiosis and silicosis is growing and many pensioners and old miners are suffering from different forms of cancer such as cancer of digestive and respiratory systems. The average number of victims of cancer in the Madan village (next to the turquoise mine) is more than other habitants in the Neyshabour area. Although development of cancer is related to several factors, but exposure to radioactivity in job conditions, geological features, presence of radiogenic radon gas in water and air of the area, and presence of 238U, 232Th and 40K in geological formations in the region suggest that radioactive emissions could be considered as the key factors contributing to cancer in this region.

The average level of natural total gamma radioactivity associated with 238U, 232Th and 40K in the Neyshabour turquoise mine area was 87.78 cps. Mine tunnels, houses, mine wastes and geological outcrop have the highest natural total gamma radioactivity, respectively. Trachyte rocks unit has the highest natural gamma radioactivity and andesite coarse-grained clastic sediments display the lowest values. 40K has the most total gamma radioactivity in the study area. Trachytic rocks are the source of natural gamma radioactivity in this region. The radioactivity of 238U, 232Th and 40K in geological formations can be considered as a main factor contributing to cancer.

Granitoids are one of the most abundant and common igneous rocks in the continental crust and they formed the world's largest batholiths. They are widely distributed in Precambrian to Cenozoic orogenic belts (e.g., Raymond, 2002), but some are formed in non-orogenic zones (Blatt et al., 2006). Because much of the continental crusts in orogenic belts are composed of granitoids, they are of particular importance in explaining the petrologic processes in orogenic belts.Cenozoic magmatism of Urmieh-Dokhtar magmatic arc is intruded by Oligo-Miocene plutonic rocks in some regions (Arvin et al., 2004). An outcrop of Oligo-Miocene granites is found in Zafarghand area in the southeast of Ardestan in Isfahan Province. Sarjoughian et al. (2018), Aminoroayaei Yamini et al. (2017), Sadeghian and Ghaffary (2011), Khalatbari Jafari et al. (2016), and Ghalamghash et al. (2019) suggested that this magmatism is a result of lower crust melting during mantle wedge metasomatism, occurred by Neo-Tethys subduction.This study aims to investigate the Oligo-Miocene granodiorites of East Bideshk, which is exposed in the central part of the Urumieh-Dokhtar magmatic arc in the northeast of Isfahan city. Despite the tectonomagmatic importance of this pluton in completing the geological history of Urumieh-Dokhtar magmatic arc, there are no comprehensive petrological studies performed on Bideshk granitoid. Thus, this study considered the mineralogy, geochemistry, tectonic environment, and origin of this granodiorite.

Microprobe analysis of the minerals was performed using a CAMECA SX 100 model with 15 kV accelerator voltage and 20 nA current at Stuttgart University, Germany. The Minpet software was also used to calculate the structural formula of the minerals and plot the diagrams. Intact and less altered rock samples are selected for geochemical analysis of major, trace, and rare earth elements by ICP-MS and ICP-OES methods in the geochemical laboratory of ALS Chemex in Ireland. The LOI values are also obtained by the gravimetric method. Fe2+ and Fe3+ are calculated based on the method by Middlemost (1989). Abbreviations for minerals are from Whitney and Evans (2010).

The Eocene Granodiorite - diorite rocks outcrop in the east of Bideshk area, in the northeast of Isfahan, and along the Urumieh-Dokhtar magmatic zone. According to lithological studies, they are mainly composed of granodiorite with predominant texture are granular, granophyre, and porphyroid.The major minerals are plagioclase, quartz, K-feldspar, hornblende, and biotite. Accessory minerals include magnetite, and apatite. Calcite and chlorite are the secondary minerals. Embayed plagioclases and quartz with rounded margins and plagioclases with oscillatory zoning, sieved texture, and dusty rims show non-equilibrium conditions during magma mixing. The composition of calcic amphiboles in these rocks is actinolite- tremolite, hornblende, and magnesio- hornblende. Plagioclases in the rocks of the east of Bideshk are andesine to labradorite in composition, and some show oscillatory zoning. Thermobarometry results indicate pressure, temperature, and crystallization depth decrease from the core (average ~ 3.01-3.63 kb, 685-732℃) of hornblende crystals. Geochemical investigations show that this granitoid is metaluminous, calc-alkaline, and I-type. The primitive mantle and the chondrite- normalized patterns of Bideshk whole-rock samples show enrichment of LREE against HREE. It is in accordance with magmatism in a subduction zone. Geochemical diagrams and variation in Rb content relative to Nb can also indicate a subduction-related magma source and mantle wedge metasomatism in the east of Bideshk, during Neo-Tethys subduction beneath central Iran.

Considering the wide extent of the Urumieh-Dokhtar magmatic arc and the presence of many intrusive and volcanic rocks in this belt, an important question from scientific and exploration points of view is “Why are some plutons productive whereas others are sub-productive and/or barren?” Barren and productive magmatic systems related to calc-alkaline arc magmatism are identified as normal or non-adakitic (low Sr/Y<20) and adakitic (high Sr/Y>20) magmas, respectively. Barren magmas are non-mineralized and have a low Sr/Y ratio, while high Sr/Y magmas are responsible for Cu-mineralization and are known as productive magmas that occur in all major orogenic belts worldwide (Cooke et al., 2005). Understanding their origin and petrogenesis is of critical importance to decipher their long-term growth and stabilization of the continental crust, and formation of economically valuable ore deposits (Monecke et al., 2018). Barren granitoid magmas typically form in pre-collisional subduction zone environments (Shahabpour, 1992), which is confirmed by the results obtained in this study. Magmatism in this region began in the Early Eocene and continued until the Pliocene. The volcanic and intrusive barren-type rocks (Eocene) that formed in a subduction-related tectonic setting are characterized by calc-alkaline and tholeiitic geochemical signature (Shahabpour, 2005). The northwest of Saveh magmatic complex is situated at the central part of the Urumieh-Dokhtar magmatic belt. The volcanic rocks of northwest of Saveh are crosscut by Late Eocene-Early Oligocene granitoids that are exposed over an area of about 100 km2.

Approximately 70 samples were intrusively collected from Mount Shahpasand and Neivesht volcanic rocks. Subsequently, 9 granitoid rocks and 7 volcanic rocks that showed the least amount of alteration were selected for whole-rock geochemical analysis. The main elements analysis was performed by X-ray fluorescence method using Optima 100V device and the analysis of rare earth elements was performed using Inductively Coupled Plasma Mass Spectrometry method and with ICP NeXION 300 device in the Lab West Laboratory of Australia.

The northwest of the Saveh magmatic complex is situated at the central part of the Urumieh-Dokhtar magmatic belt. The volcanic rocks of this area are crosscut by the Late Eocene-Oligocene granitoids. Whole-rock geochemistry shows that the studied igneous rocks with low to medium potassium calc-alkaline geochemical signatures have strong depletion in Nb and Ti and enrichment in LREE and LILE, which imply formation during normal arc magmatism. Sr/La and La/Yb trace element ratios show that all samples have evidence for slab fluid metasomatism and a mantle source affected by metasomatism. La/Nb and La/Ba ratios also confirms a subduction-modified lithosphere mantle source for the magmatic rocks in the northwest of Saveh. Geochemical evidence shows that these rocks are barren-type igneous rocks that have the same origin and differential crystallization is the dominant process in their petrogenesis. Barren magmatism in the northwest of Saveh is likely a result of partial melting of juvenile lower crust caused by subduction of the Neo-Tethys oceanic lithosphere, whereas productive adakitic rocks within the Urumieh-Dokhtar magmatic belt have formed by partial melting of thickened lower crust.

Granitoids have gabbrodiortite-diorite, Quartz monzonite, granodiorite and granite composition, while volcanic rocks are petrologically classified as basaltic andesite, andesite and dacite-trachydacite. Geochemical studies of whole rocks indicate that they have strong depletions in HFSE (Nb, Ti, Zr) and enrichments in light rare earth elements and large ion lithophile elements compared to N-MORB. Geochemical signature of the igneous rocks in northwest of Saveh (low Sr/Y ratio of almost <30) and their negative Eu anomalies (Eu/Eu∗ = 0.62–1.05) suggest generation in a subduction zone and pre-collisional setting. However, productive rocks elsewhere within the Urumieh-Dokhtar magmatic belt exhibit adakite-like calc-alkaline magmatic characteristics (high Sr and Sr/Y, but low Y). Signature of this magmatic complex is consistent with other barren-type magmas through the Urumieh-Dokhtar magmatic belt. The low ratios of (La/Sm)N and (Dy/Yb)N (0.50–1.18 and 0.91–1.35, respectively) are similar to those from barren-type of granitoids. Examination of the studied samples on a Y versus MnO diagram (Baldwin and Pearce, 1982) shows that the samples have characteristics of barren-type igneous rocks. Haschke and Pearce (2006) suggested that a high Y content in barren magmas may record the participation of anhydrous phases during the early stages of magma genesis and so account for lack of associated mineralization. However, it may be possible that partial melting of the source is superficial, in agreement with a moderate pre-collisional crustal thickness of 35–45 km. Low Sr/Y (< 30) ratios measured in the Eocene–Oligocene northwest of Saveh igneous rocks suggest generation via island-arc magmatism, while a Sr/Y ratio of > 56 for productive rocks implies garnet, hornblende, and clinopyroxene minerals in the source, leading to enrichment of LREE/HREE (Castillo, 2012).

Podiform chromite deposits are small magmatic chromite bodies formed in the lower section of an ophiolite complex. The Khoy ophiolite covers an extensive area in the northwest of Iran along the Iran-Turkey border.In this research study 1200 magnetometry data and geoelectric studies along 5 profiles were designed for prospecting chromite lenses. Mineralogical and geological studies have shown that pyrite, magnetite and other metallic sulfides are formed during the serpentinization process in the fractures of chromite lenses. The amount of released magnetite in the chromitites is less than the amount released in the harzburgite and dunites. Therefore, the number of magnetic anomalies created are less than those generated by bedrocks (Imamalipour, 2009). These metal sulfides increase the chargeability of positive anomalies in the cross-sections. Resistivity also shows a significant reduction compared to the bedrocks due to the metallic properties of chromite lenses.

In this research study, geological methods were used to interpret geophysical data in the Khoy ophiolite. Geological surveys at a scale of 1:20000 were implemented in an area of about 70 km2. 1200 magnetic points and resistivity and induced polarization along 5 profiles with a geological map and mineralogical studies were used. Magnetometric data at the 5*10m grid and Ip-Rs data with 10 m interval electrode spacing were collected.  For the inversion modeling of Ip-Rs data, Res2d inv software was used and geological and mineralogical data were integrated with magnetometric results.

Exploration of podiform chromite deposits has been a challenge due to their unpredictable occurrence, small size of most orebodies, and intensive tectonic dislocations (Mosier et al., 2012). Moreover, the absence of primary geochemical halos and associated alteration are issues that lead to difficulties in prospecting for podiform chromites. Chromite is an accessory mineral associated with the harzburgite host rock. The results of geophysical studies show that chromite lenses have lower magnetization than gabbro and higher mangnetization than harzburgite (Frasheri et al., 1995). The reason is the mineralogical conditions of chromite lenses and their host rocks. Mineralogical study showed that some chromite lenses have fractures that are filled with silicate secondary minerals (serpentine). Chromite and serpentine are the main minerals, and hematite and magnetite are minor minerals in the chromite orebodies. Although these minerals have been altered and have mostly been converted to serpentine, the earliest composition is likely to be olivine. Dunite and harzburgites are chromite lenses host rock and are mainly serpentinized and contain fine magnetite particles, which can cause positive magnetic anomaly (Imamalipour, 2009, Masoudi and Imamalipour, 2019). These small metallic minerals cause high induced polarization and the embedded rocks show a higher degree of charge. Because of the metallic nature of chromite lenses, the resistivity has a much lower value. Therefore, using resistivity, induced polarization, and magnetic geophysical methods, chromite lenses can be separated from harzburgite host rocks.

In this study, geophysical resistivity and inductive polarization method with magnetometry, which is one of the most important methods for the exploration of subsurface deposits in the Khoy ophiolitic zone, have been used. As a result, it was found that podiform chromite does not show much difference in the magnitude of the magnetic field. Therefore, this method cannot alone be used to explore chromite deposits. However, the IP-Rs method can be used as a practical method for exploration of these reserves. Chromite lenses have low resistivity values of about 400 to 600 ohm-m. The amount of induced polarization is also much lower than its host rock, with values of 3 to 6 mv/v. Therefore, these properties can be used for chromite exploration at a much lower cost than gravimetric and electromagnetic methods. The reason for these values can also be found in the mineralogy of the chromitite lenses. During the serpentinization process of harzburgite and dunite, magnetite minerals, chalcopyrite, and some metallic elements are released. Released magnetite increases the magnetic properties of chromitite. However, this increase is less than the magnetism of the host rock. The released metallic elements such as chalcopyrite with serpentinite also increase the changeability of the host rocks and chromite lenses with low induction polarization and much lower resistivity could be identified.

The lenticular Shahneshin barite deposit (N: 35°39'36'' and E: 46°36'11'') is located 80 km  northeast of Marivan, Kurdistan Province; north Sanandaj-Sirjan Zone (Stöcklin, 1968). The deposit consists of stratiform ore and stringer zone. The stringer zone has occurred with alteration sericite- quartz in the footwall dacitic unit (Kv) and evident in a series of vein-veinlets under stratiform ore. The stratiform ore has been located concurrently on the dacite unit and below the Sanandaj Shale unit (Hasankhanloo, 2015).The study area mainly consists of Mesozoic succession dominated by the dacite tuff, andesitic-basaltic lava and pillow lava (Kv: the host rock), black slate and phyllite (Kss: Sanandaj Shale), dolomitic limestone with intercalation of sandstone (Kl), and black shale and slate (Ks: Sanandaj Shale). In this study, samples of the Shahneshin barite deposit have been analyzed for their 87Sr/86Sr and δ34S isotopes and trace elements (plus REE) geochemistry to assess the source of the deposit.

Forty samples were collected from the Shahneshin barite deposit and country rocks. Polished blocks (6 samples) and thin sections (34 samples) were prepared for SEM images and petrographic examination at the University of Kurdistan. Trace elements (plus REE) were determined by ICP-MS in the Geological Survey center of Iran (Karaj). The detection limits for elements are between 0.08-0.6 ppm. Three whole-rock samples for Sr and S isotopes were analyzed at the Department of Earth and Space Sciences of the University of Science and Technology of China.Sulfur isotope analyses were measured by the use of a Delta V Plus Gas Isotope Ratio Mass Spectrometer. The analysis accuracy was determined to be ±0.2‰ (2σ) by using Canyon Diablo Troilite (CDT) as a standard (34S/32S=0.0450045). The strontium isotopic composition was completed on a Thermal Ionization Mass Spectrometry instrument by Phoenix. The measured strontium isotope normalized to 86Sr/88Sr=0.1194 and its NBS-987 standard was 0.7102477±0.000014 (2σ).

Strontium isotopes, sulfur isotopes, trace-element (plus REE) composition, fluid inclusion, and petrography of barites help to identify sources of mineral-forming components and environments of precipitation (Baioumy, 2015). The Shahneshin barite deposit includes sulfate barium without valuable Pb and Zn elements. Barite crystals are mainly coarse (>20µ m) with euhedral, tabular, and bladed morphologies. Fluid inclusion microthermometry indicates that the barite formed from low salinity (2.0-8.5 wt.% NaCl eq.) fluids at low temperatures, between 115 to 215oC (Hasankhanloo, 2015).Chondrite-normalized REE patterns for the barite samples reflect enrichment of the LREE/HREE ratios, as is shown by the high (Nd/Er)CN> 11 ratios. They also show Eu/Eu*CN (0.5-7.0), Ce/Ce*SN (0.1-1.16), La/Lu*CN >1, and ratios of the Ce/La (mostly>1), and Eu/Sm (0.1-2.83). The geochemistry of the barite samples represents variation in the abundance of trace elements and REECN patterns. The 87Sr/86Sr and S-isotopic values of Shahneshin barite samples are 0.70649-0.70651 and δ34S=19.05-21.53‰, respectively.

Barite has very little Rb in its structure, and the isotopic composition of the original Sr is preserved in it (Martin et al., 1995). The 87Sr/86Sr values of the barite samples are consistent with 87Sr/86Sr=0.70649-0.70651, which itself is higher than those for host volcanic rocks (0.704-0.705) but lower than that of the Cretaceous seawater (0.7075), the time of barites formation. We may conclude that strontium in the barites is a mixture of predominantly juvenile hydrothermal fluid of low Sr isotope and seawater that contains more radiogenic strontium. δ34S (=19.05-21.53‰) of the samples indicate that much of the sulfur in barite was derived from seawater (δ34S=20-22‰).Fluid inclusion salinities (Hasankhanloo, 2015), crystal sizes and morphology, abundance of sulfate mineral, lack of valuable Pb and Zn, distribution patterns of trace elements (plus REE) of barite reveal that mixture of magmatic fluid and seawater, with different ratios, were the source of the barite-forming fluid. That is supported by the δ34S values, the location of samples on the Th-U diagram (seawater sources), variations in trace element (plus REEs), and Au anomaly (magmatic sources) in the samples. REEs, La enrichment, variations in abundance of trace elements, as well as δ34S and 87Sr/86Sr isotope values of the samples are consistent with the Kuroko massive sulfide-type (Marumo, 1989) and submarine hydrothermal volcanic model. In this model, barium has leached from the bedrocks by circulation of reduced hydrothermal fluid and transported along the syn-sedimentary normal faults to the sea-floor. Then, fluid is mixed with SO42- of seawater and it causes the barite to precipitate. These barites have been formed in an open system, on or immediately below the sea-floor.The Shahneshin barite deposit was, most probably, formed within caldera structures on top of the volcanic complexes in the late-stage of submarine volcanic activity with andesite-dacite in composition. It has occurred at continental margin tectonic setting between subduction zone and passive continental margin due to oblique collision along the Sanandaj-Sirjan Zone in the Late Cretaceous.