فصلنامه زمین شناسی اقتصادی
سال پانزدهم شماره 1 (پیاپی 36، بهار 1402)

The Dalli porphyry Cu-Au deposit is located in the central parts of Urumieh –Dokhtar Magmatic Arc (UDMA). This deposit is formed via the emplacing of Miocene intrusions mainly containing diorite and quartz diorite within the Eocene andesite and porphyritic basaltic andesite units. Main alterations in this region include potassic, propylitic and to a lesser extent phyllic. In this study, magnetite chemistry in the potassic alteration zone is investigated. The results of EMPA show that magnetites of this Au-rich porphyry system are characterized by enrichment in Ti, Al, V, Mg, and Mn values. Also, the magnetites formed via the hydrothermal processes. Evidences such as magnetite martitization and exsolution of ilmenite lamellae imply for magnetite crystallization in high oxygen fugacity conditions. Moreover, based on the Al + Mn vs. Ti + V diagram studied magnetites follow the trend of temperature decreasing which could be considered as an important factor in increasing the potentials of sulfide mineralization thorough the hydrothermal system evolution. Compared with Daralou and Regan porphyry systems, the Dalli magnetites contain higher concentrations of Ni, Mn, Cr, and Co presenting an exploration key for discovering the Au-rich porphyry deposits.

Porphyry copper deposits (PCDs) are related to the shallowly emplaced (5-10 km) oxidized magmatic systems in the subduction, syn-collisional, as well as post-collisional tectonic settings (Richards, 2011). They supply most of the world's Cu and Mo resources; ~80 % Cu and ~95 % Mo (Sun et al., 2015). In Iran, widespread occurrence of porphyry copper deposits has been discovered and mined in the Urumieh-Dokhtar Magmatic Arc (UDMA; Richards, 2015). These deposits are related to the evolution of the Neo-Tethys ocean starting with subduction in late Cretaceous to middle Miocene and subsequent prevailing the  syn- to post-collisional tectonic regimes during the Neogene (Richards, 2015; Zarasvandi et al., 2018). Most of the porphyry bearing intrusions of UDMA exhibiting a spectrum of mineralization from weakly to highly mineralized systems were emplaced during the Miocene (e.g., Sarcheshmeh, Meiduk, and Dalli). Recent studies concerning on the source of mineralized porphyry granitoids in the UDMA (e.g., Asadi, 2018) specified a model comprising the partial melting of subduction-modified thickened mafic juvenile lower crustal rocks responsible to generation of adakite-like-hydrous, relatively oxidized magmas (Sun et al., 2015) with the high potential to form porphyry Cu ± Mo ± Au systems.
During the last decade, magnetite geochemistry has been the focus of several studies trying to constrain the physicochemical attributes of igneous and hydrothermal ore systems (e.g., Dare et al. 2014). Magnetite can form under various conditions having the capability of fixing various minor and trace elements (e.g., Co, Cr, V, Ti, Mn, Mg, and Al) in its spinel structure (Nadoll et al., 2015). This makes magnetite able to record many environmental variables which are very important in mineralization potential of porphyry Cu-systems (e.g., oxygen fugacity, temperature, and ratios of fluid-rock interaction). Although the Dalli porphyry Cu-Au deposit has been the subject of many studies manly focusing on the magmatic evolution, fluid inclusion, silicate (plagioclase, biotite, and amphibole) and sulfide (pyrite and chalcopyrite) chemistry (Ayati et al., 2013; Zarasvandi et al., 2015a; Zarasvandi et al., 2018; Zarasvandi et al., 2019c); none focused on the oxide minerals (magnetite composition). The present work reports petrographic and chemical data of magnetite and tries to constrain the factors controlling the formation of Dalli deposit.

Sampling was carried out on drill cores and special care was undertaken to select the samples showing no obvious overprint of low temperature alteration. Polished thin sections were prepared from 1-2 cm sized blocks for microscopy and electron probe microanalyzer (EPMA) studies. Wavelength-dispersive (WDS) EPMA analyses of oxides were conducted at the Chair of Resource Mineralogy, Montanuniversität Leoben, Austria using the Jeol JXA 8200 instrument and the following analytical conditions: 15 kV accelerating voltage, 10 nA beam current and beam size to spot mode (of about 1μm). K lines were used for Mn, Fe, Ti, Mg, Al, Cr, and V. The counting times for element peaks and background (upper and lower) were 100 s and 20 s, respectively. The lower limit of detection for these elements (single standard deviation) as calculated by the integrated Jeol software.

In the Dalli porphyry Cu-Au deposit, hypogene mineralization mostly includes pyrite, chalcopyrite, and magnetite with minor chalcocite and bornite. Ore minerals occur as aggregates, in veinlets or disseminations within the potassic alteration, and to a lesser extent in the phyllic alteration zones. In the all analyzed samples, the values of Al2O3, V2O3 and MnO were upper then detection limit. Conformably, detectable values were mainly obtained for TiO2, Cr2O3 and MgO. On the contrary NiO, SiO2, CuO were mainly below the detection limit. The FeO content (wt. %) in the analyzed magnetites varies between 91.01 to 98.57 (average; 97.01), Al2O3 between 0.063 -5.07 wt. % (average 0.62 wt. %), and the lowest and highest values of V2O3 are 0.02 and 0.34 (wt. %), respectively. The average of MnO and MgO in the analyzed samples is 0.25 and 0.07 (wt. %), respectively. Additionally, the TiO2 content varies between 0.01 and 2.45 (wt. %); averaging 0.34 (wt. %).

On the Ti (ppm) vs. V (ppm) discrimination diagram, most of the analyzed magnetites extended to the field of hydrothermal field providing insight into the formation of magnetite owing to the exsolving of hydrothermal fluids through the potassic alteration. Comparison of the magnetite composition in the Dalli deposit with other PCDs in the UDMA implies that there are higher average contents (wt. %) of Mn, Fe, Mg, and Cr compared with Daralou (an example of pre-collisional porphyry intrusion) and Keder porphyry systems (an example of weakly mineralized collisional porphyry deposit). These features may highlight the importance of magnetite composition in establishing the discrimination diagrams of Au-rich porphyry Cu-deposits using magnetite composition. The documented oxy-exsolution of ilmenite as well as hematite intergrown with magnetite in the Dalli samples are the indicative of high  in the potassic alteration stage. Under such highly oxidized conditions sulfur is present as oxidized species (such as  ) rather than as reduced species (such as ) preventing the extensive sulfide deposition in magmatic and early stages of potassic alteration (Zarasvandi et al., 2022). This process could enhance the mineralization potential of the system by preserving the sulfur content, especially before the main mineralization stages. Besides optimum tectonomagmatic conditions, the physicochemical attributes of potassic alteration may also have a decisive role in predicting the mineralization potential of porphyry systems (Zarasvandi et al., 2018). Because bulk sulfide mineralization occurs at the end of potassic alteration (Richards, 2011). Prevailing of the high temperatures in potassic alteration could prevent the disproportion SO2 to H2S which is necessary for sulfide precipitation (Richards et al., 2017; Zarasvandi et al., 2018). Conformably, the inability of hydrothermal systems for cooling could be linked to the low mineralization degree of the porphyry deposits. Based on the Al + Mn vs. Ti + V diagram (Zhao et al., 2018), samples of Dalli deposit follow the trend of temperature decreasing which indicate the desirable conditions for enhancing the sulfide mineralization in the Dalli porphyry Cu-Au deposit.

The Tangedozdan area is located in the west of Isfahan province and 25 km northeast of Fereydounshahr. Structurally, this area is located in the Sanandaj- Sirjan zone. The rock units include greenish volcanic rocks, lime-sandstone, limestone to dolomitic-limestone, conglomerate, sandy-limestones and present-age alluviums. The existing rock sequence along with zinc and lead mineralization has been affected by tectonic phenomena, in the form of thrusting and the formation of open folds, joints and fractures. The main geological structures include thrust plates that have pushed scales of Jurassic and Cretaceous rock units from the northeast to the southwest on top of each other. The folding structures are very small and dense size and are mainly related to faults that have affected the rock units, especially thin-bedded limestone. Tectonic studies show the influence of two lateral faults with the NW-SE trend and a concentrated fault zone inside the dolomitic rocks in the mineralization process. Zinc and lead mineralization shows more expansion in the tension zones. Mineralogy, geochemistry and, EPMA studies indicate the presence of calamine and a small amount of zincian dolomite. The limestone to dolomitic-limestone rocks hosts zinc and lead mineralization and consists of lenses, non-sulfide minerals veins and, veinlets such as smithsonite, hemimorphite, cerussite and, barite, sulfide minerals such as sphalerite and galena. The dolomitization phenomenon due to the effects of acidic hydrothermal fluids has caused alteration of the carbonate wall rock. The structural factor is the main reason for the formation of this dolomite type and the replacement of magnesium with zinc.

High tectonic energy causes shear structures by deforming the crust (Ramsay and Huber, 1987; Lawrence, 2010; Peacock, 1992; Montest and Hirth, 2003). Different temporal and spatial distribution of mineral resources is the result of crustal orogenic actions during tectonomagmatic terms related to specific crust zones. (Aghanabati, 2006; Nabatian et al., 2015). Carbonate rocks under appropriate geodynamic conditions with specific platforms are potential hosts of lead and zinc resources (Rajabi et al., 2012a; Rajabi et al., 2012b; Amiri, 2017; Karimpour et al., 2019). Accordingly, in this we attempt to investigate the relationship between the structure and mineralization and provide a model for structural formation. The Tangedozdan zinc and lead mine 25km northeast of Fereydounshahr is located in the extreme western corner of Isfahan Province and adjacent to the Lorestan Province. For the geological location, this area is considered part of the Sanandaj-Sirjan zone. The limestone unit in the east of Tangedozdan hosts zinc carbonate mineralization. In this region, the mineralization is located between two faults inside the dolomite limestone concentrated directly on the trachyandesite volcanic rocks.

To accurately identify the minerals, thin-polished sections were prepared from the surface, boreholes, and trenches and studied by transmitted and reflected polarization microscope (Nikon E200). Also, many samples were studied by XRD and EPMA. 

The Tangedozdan zinc-lead mine includes rock units in the convergent and active margin of the neotethys Ocean in the Mesozoic. These rocks were formed in an eugeocynclinal medium during the Jurassic and early Cretaceous periods (Aghanabati, 2006). Tectonic phenomena, in the form of thrusting and the formation of open folds, joints, and fractures, are considered mineralogy controllers. Two important and major faults related to mineralization have been identified in Tangedozdan. The first fault at a distance of about 650m to the east of Tangedozdan and along the general direction of N158 caused contact between sandy limestone deposits and calcareous sandstone, and the fault has played an important role in mineralization. The second fault, at a distance of about 450 m to the east of Tangedozdan, with the general direction of N150, along with the past fault, has played an important role in mineralization, and together with the sub-faults, they are considered to be structural controllers of mineralization.
Mineralogical studies as well as the use of EDS spectra and XRD have shown presence of non-sulfide minerals such as smithsonite, cerussite, hemimorphite, barite, and sulfide minerals such as sphalerite and galena, which are paragenesis of each other. The transparent minerals are calcite and dolomite and barite and Quartz to a lesser extent, which are placed in the space between the opaque minerals. Quartz is mainly observed heterogeneously and only in some empty spaces. The formation of empty spaces between the crystals and the fractures is the result of the dolomitization phenomenon and it has made possible the concentration of ore-bearing fluids and the deposition of valuable zinc and lead ores. Hence, mineralization can be expected in parts of the deposit where developing dolomitization and creating empty spaces is possible. Calamine is very similar to carbonate minerals such as dolomite and calcite and has a variety of colors (Wilkinson, 2014; Lecumberri-Sanchez et al., 2014). Therefore, in Tangedozdan, the two-component reagent Zinc Zap was used, which qualitatively shows the presence of zinc-bearing minerals and leads to red and orange colors to identify calamine or non-sulfide minerals that cover zinc and primary sulfide minerals. Accordingly, calamine was identified in field studies in Tangedozdan.
The most important existing alteration includes dolomite, silicic, and carbonate, which can be seen with non-sulfide zinc mineralization such as calamine, and zincian dolomite, which is considered an important sign of mineralization in the region. The dolomitization phenomenon due to the effect of acidic hydrothermal fluids has altered the carbonate wall rock. The structural factor is the main reason for the formation of this type of dolomite and the replacement of magnesium with zinc (Boni et al., 2011; Mondillo et al., 2017).

Given field evidence, it can be said that zinc and lead have mineralized simultaneously with the faults with the current mechanism of normal dip-slip along with strike-slip component with the general direction of N150 to N158. Then, with penetration of fluids containing zinc and lead, mineralization has taken place along the existing faults and their sub-faults as mineralization structural controllers. According to the studies, the dolomitized process has led to the formation of empty spaces between the crystals as well as fractures and finally the concentration of ore fluids and deposition of valuable zinc and lead ores. The phenomenon of dolomitization has also changed the carbonate wall rock.

Precious and base metal mineralization in the Qebchaq deposit occurred as brecciated quartz-sulfide veins within the Eocene tuff and lava strata, and the Oligocene quartz diorite-gabbro intrusion. Pyrite, chalcopyrite, galena, sphalerite, and gold along with minor realgar, psilomelane, and pyrolusite, are ore minerals; quartz, sericite, chlorite and calcite are gangue minerals. The ore minerals show disseminated, vein-veinlet, brecciated, comb, cockade, colloform, crustiform, plumose, and vug infill textures. Five stages of mineralization can be distinguished at Qebchaq. Stage 1 is represented by silicification of host rocks along with minor disseminated pyrite. Stage 2 is characterized by quartz veins and breccias that contain variable amounts of disseminated pyrite, chalcopyrite, galena, sphalerite ± native gold ± realgar. Stage 3 is marked by quartz-manganese oxides-hydroxides (psilomelane, pyrolusite, braunite) veins and hydrothermal breccia cements. Stage 4 is represented by quartz (calcite-chlorite) vein-veinlets, and stage 5 is characterized by calcite as veinlets and vug infill texture. Wall-rock alterations include silicification, intermediate argillic, carbonate, chlorite and propylitic alteration. Chondrite–normalized trace elements and REE patterns of the mineralized samples and the host rocks are similar and indicate that host rocks are probably involved in mineralization. Characteristics of Qebchaq deposit are comparable with intermediate-sulfidation type of epithermal deposits. 

Qebchaq base and precious metal deposit, 15 km northwest of Qarachaman, is located in the Western Alborz–Azerbaijan zone, northwestern Iran. Several types of deposits are present in this zone including porphyry and skarn Cu-Mo (Au) porphyry deposits, Cu-Mo and Fe skarn deposits, Cu-Mo-Au vein deposits, and epithermal Au deposits (Jamali et al., 2010; Kouhestani et al., 2018). The most important deposit discovered to date within the Western Alborz–Azerbaijan zone is the Sungun porphyry Cu-Mo deposit, which has a defined reserve of 796 Mt at 0.6% Cu (Hezarkhani and Williams-Jones, 1998; Aghazadeh et al., 2015; Simmonds et al., 2017). Other important deposits or occurrences include Haft-Cheshmeh, Sonajil, Ali Javad, Mirkuh-e-Ali Mirza, Astergan, Avan, Anjerd, Mazraeh, Astamal, Pahnavar, Masjed Daghi, Sharafabad, Mivehroud, Nabijan, Zaglig, Aniq, Zaily Darreh, Qara Darreh and Qarachilar (Ebrahimi et al., 2011; Jamali et al., 2010; Mokhtari, 2012; Maghsoudi et al., 2014; Mokhtari et al., 2014; Adeli et al., 2015; Baghban et al., 2015; Baghban et al., 2016; Simmonds and Moazzen, 2015; Kouhestani et al., 2018).
Although geological general characteristics of the location of the Qebchaq deposit have been determined (Asadian et al., 1993), no detailed studies have been conducted on the mineralogy, geochemistry, and genesis of the Qebchaq deposit. In this paper, detailed geology, mineralogy, geochemistry, and alteration styles of the Qebchaq deposit to constrain its ore genesis are investigated. These results may have implications for the regional exploration of epithermal base and precious metal deposits in the Western Alborz–Azerbaijan zone.

Detailed fieldwork has been carried out at different scales in the Qebchaq area. A total of 50 samples were collected from various parts of ore veins and breccias, host volcanic rocks, and intrusions. The samples were prepared for thin (n=8) and polished-thin (n=32) sections in the laboratory at the University of Zanjan, Zanjan, Iran. Thirty nine representative samples from the mineralized veins and breccias, 1 sample from host dacitic rocks, and 1 sample from altered quartz diorite-gabbro intrusion were analyzed for REE, Au, Ag, Cu, Pb, Zn, and other rare elements using Fire Assay and ICP–MS in the Zarazma Analytical Laboratories, Tehran, Iran.

The geological units hosting the Qebchaq deposit are mainly Eocene volcanic and volcaniclastic rocks that have been intruded by Oligocene intrusions. The Eocene sequence includes tuff, andesite, and andesitic basalt, rhyolite, rhyodacite-dacite, and ignimbrite. The intrusive rocks in the Qebchaq area include Oligocene quartz diorite-gabbro and granite-alkali granite. They show porphyritic, microgranular, and granular textures. Mineralization at Qebchaq occurs as the epithermal base and precious metal quartz-sulfide brecciated vein that occupies NE-trending faults in the Eocene volcanic rocks and Oligocene intrusions.  The ore veins are 50 to 1000 m long, from 0.5 to 4 m wide, and generally, dip steeply (65–85°) to the southeast and northwest. Wall-rock alterations developed at the Qebchaq deposit include silicification, intermediate argillic, carbonate, chlorite, and propylitic alteration. The first four types are closely related to mineralization. Five stages of mineralization can be distinguished at Qebchaq. Stage 1 is represented by silicification of host rocks along with minor disseminated pyrite. This stage is usually crosscut by stage 2. Stage 2 (the main ore-stage) is characterized by millimeters to several centimeters wide quartz veins and breccias that contain variable amounts of disseminated pyrite, chalcopyrite, galena, sphalerite ± native gold ± realgar. Clasts of this stage and associated wall-rock alteration have been recognized in the hydrothermal cement of stage 3 breccias. Stage 3 is marked by quartz- manganese oxides-hydroxides (psilomelane, pyrolusite, braunite) veins and breccia cement. It is usually crosscut stage 2 and is cut by stage 4 veinlets. Stage 4 is represented by < 1 mm wide quartz (calcite-chlorite) vein-veinlets. This stage usually crosscuts previous ore stages. No sulfide minerals are recognized in stage 4. Stage 5 is characterized by up to 2 mm wide veinlets or vug infill texture of calcite. Stage 5 calcite veinlets usually crosscut previous ore stages. The ore minerals at Qebchaq have been formed as vein-veinlet and hydrothermal breccia cement, and show disseminated, vein-veinlet, brecciated, comb, cockade, colloform, crustiform, plumose, and vug infill textures. Pyrite, chalcopyrite, galena, sphalerite, native gold, realgar, psilomelane, and pyrolusite are the main ore minerals. Malachite, azurite, smithsonite, cerussite, goethite, secondary pyrolusite, and braunite are supergene minerals. Quartz, sericite, chlorite, and calcite are present in the gangue minerals. 
Comparison of Chondrite–normalized rare elements and REE patterns of host dacitic lavas, fresh and altered quartz diorite-gabbro intrusion, and the mineralized samples at Qebchaq indicate that leaching of some elements from the host rock units may have been involved in mineralization. The data in this study suggest that Qebchaq is an example of intermediate-sulfidation type of epithermal base and precious metal mineralization.

In this research, geochemical data from 314 samples of volcanic and intrusive rocks with adakitic or adakite-like affinity reported from eastern Iran have been studied, these rocks are often known with Sr>400 g/ton and Y<18 g/ton. By comparing and analyzing the characteristics of these adakites, it is concluded that: (1) The adakite rocks of eastern Iran are mainly high silica adakites; (2) High-silica adakitic rocks in northeastern Iran have lower MgO, Th, and Th/Ce and relatively higher Cr, Ni, and SiO2 contents than other adakites in eastern Iran, indicating their connection with the subduction zone and melting of the oceanic crust, while the adakitic rocks of southeastern Iran with lower SiO2 content and higher MgO, Sr, and Th/Ce are categorized as post-collision adakites mainly formed from melting of the thickened lower crust; (3) Most of the adakites in the central parts (eastern Iran) were formed from the melting of the thickened lower crust after the collision, from an amphibolite garnet source, and the ratios of Sr/Nb, Ba/Nb and La/Nb of adakites decreases towards the northeast in this section; 4) The analyzed data and the results presented in this research show that the adakites of eastern Iran have characteristics associated with mineralization and often have the necessary potential to play a role in the formation of valuable reserves.

The term adakite refers to volcanic and intrusive rocks that have more than 56% SiO2, more than 15% Al2O3, and usually less than 3% MgO by weight, high Na2O content (3.5-7.5 %), and low ratio of Drummond et al., 1996K2O/Na2O (<0.5) (Defant and Drummond, 1990;; Martin, 1999; Martin et al., 2005; Condie, 2005; Castillo, 2012). Adakites are divided into (1) a high- SiO2 adakite (HSA) and (2) a low- SiO2 adakite (LSA). The HAS have >60 wt.% SiO2, low MgO (0.5–4 wt.%), CaO + Na2O contents <11 wt.% and Sr abundances <1100 ppm. In contrast, the LSA have <60 wt.% SiO2, higher MgO (4–9 wt.%), CaO + Na2O contents >10 wt.% and Sr contents 1000–3000 ppm (Martin et al., 2005).
The studied area in the eastern part of Iran (Figure 1-A) includes a large part of the structural zones in the south and east, including the Lut block, Makran arc, the Sistan suture and Binaloud. This region is a part of the extensive magmatism that has spread from Turkey to Pakistan and had numerous magmatic activities over time, especially from the Cretaceous to the Quaternary.
Adakitic series have received special attention in recent years in Iran and some articles have been published by various researchers. The main goal of this research is to review the published articles and documents related to the geochemical and isotopic characteristics of adakites in eastern Iran, in order to open a window for a better understanding of the relationship between adakite magmatism and magmatic-tectonic evolution and porphyry copper ± gold mineralization in the east of Iran.

Geochemical data of 314 samples of volcanic and intrusive rocks with adakitic nature were collected from eastern Iran. The location of the studied areas and a summary of data and references is presented in Figure 1 and Table 1. In this study, acidic and intermediate rocks (volcanic and intrusive) with adakitic characteristics were studied and mafic rocks such as basalt and samples with high LOI (above 3) were not considered in the database (Figure 2-A, B).

Volcanic and sub-volcanic adakitic rocks have been reported from Sabzevar, Neishabur and Quchan regions (Table 1, Figure 1-B). These rocks are mainly dacite to trachyandesite and andesite with calc-alkaline to high K- calc-alkaline affinity. Rocks with adakitic nature in central part of eastern Iran are reported from the areas of Garjagan, Khosuf, Shurab, Fadeshk, Pironj, Gurung, Shah Suleiman Ali, Sang-Rahuzag, Shadan, and Tighnab (Figure 1-C and Table 1). According to the chemical classification diagram (Middlemost, 1994), the composition of volcanic rocks is mainly dacite, rhyodacite, andesite and trachyandesite and intrusive rocks are mainly diorite, granodiorite and granite (Figure 2-A, B). They are mostly calc-alkaline to high-K calc-alkaline, sometimes shoshonite (Figure 5-A) and meta-aluminous affinity.
Southern part include adakitic rocks from Lar, Malek Siah Kuh, Lakhshak, Chah Serbi, Shaheswaran, Taftan and Karvander areas (Table 1 and Figure 1-D). The volcanic rocks of the southern part are mainly dacite to andesite (Figure 2-A) and the intrusive rocks are mainly diorite and gabbrodiorite (Figure 2-B). These rocks have the characteristics of calc-alkaline with high-K to and meta-aluminous affinity.

Based on the data presented in this study, it is clear that the adakite rocks of eastern Iran are mainly high silica adakites. These rocks in northeastern Iran have lower MgO, Th, Th/Ce and relatively higher Cr, Ni, and SiO2 contents than other adakites in eastern Iran, which indicate their connection with the subduction zone and melting of the oceanic crust.
The adakitic rocks of southeastern Iran with lower SiO2 content and more MgO, Sr, and Th/Ce are in the range of post-collision adakites, which are mainly formed from melting of the thickened lower crust.
Most of the adakites in the central parts (eastern Iran) were formed from the melting of the thickened lower crust after the collision, from an amphibolite garnet source.
Temporal-spatial relationship between adakites and porphyry copper deposits and/or epithermal gold-copper deposits is studied in many researches (e.g., Thiéblemont et al., 1997; Sajona and Maury, 1998; Li et al., 2011; Richards et al., 2012; Zhang et al., 2021). Porphyry mineralization in Iran mainly took place during the evolution of the branches of the Neo-Tethys Ocean and its final closure. The results presented in this research illustrate the adakites of eastern Iran have characteristics associated with mineralization and often have the necessary potential to play a role in the formation of valuable reserves. Changes in La/Sm and Dy/Yb ratios in adakites are considered as a geochemical sign for mineralization potential. The ratios of (LaN/SmN) and (DyN/YbN) help to determine the fertile magmatism (with the participation of amphibole) from the barren (without amphibole) (Richards et al., 2012). Amphibole-dominated adakites are clearly associated with economic porphyry copper mineralization (e.g., Kheirkhah et al., 2020). In the studied adakites, the changes of LaN/SmN and DyN/YbN ratios are 1.7 to 10.7 (average 4.5) and 0.7 to 2.5 (average 1.2), respectively. Based on these ratios, most of the studied adakites, except for some adakites that show changes in LaN/SmN ratios of less than 4 and DyN/YbN less than 1.1, have mineralization potential.
The analyzed data and the results presented in this research yields that the adakites of eastern Iran have characteristics associated with mineralization and often have the necessary potential to play a role in the formation of valuable deposits. The distribution of copper-gold indices, and the outcrops of adakites along with magnetic anomalies (Figure 10-A), and crust thickness variations in eastern Iran (Figure 10-B), emphasize the importance of focusing on future prospecting, drilling and isotopic studies in this area.

In this research, to contribute to the understanding of the geochemistry of trace elements in zircon, we determined the REEs, Y, Nb, Ta, Th, and U contents in zircon grains in three granitoids (Sarnowsar, Sarkhar and Bermani) by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in order to determining the magma sourcee and magmatism fertility. The zircon/rock partitioning coefficients of REE, Y, Nb, Ta, Th, and U contents indicate that the patterns of the trace elements of the studied granitoids are controlled by the liquid composition at the magmatic crystallization. Compared to Sarkhar and Bermani granitoids, the Sarnowsar granite has a higher temperature (736° to 915 °C), higher zircon/rock partitioning coefficient of REEs, Y and Th (up to 2770 for Zr) and it was formed in higher oxidant conditions (△FMQ values between -0.06 to 17.01). The results of this study show that oxidized and I-type magmas in subduction-related tectonic environments are more favorable for porphyry and skarn mineralization.

Zircon is the most commonly analyzed accessory mineral and is routinely employed in U–Th–Pb geochronology, (U–Th)/He and fission track thermochronology, radiogenic (Hf) and stable (O) isotopic studies, crystallization thermometry, and trace element geochemistry (Belousova et al., 2002). A critical presumption in zircon chemistry studies is that data obtained from zircon is a proxy for the parent igneous rock. This is evidently true for most types of analyses, however, relating trace element and rare earth element (REE) concentrations in zircon compared to bulk rock or melt concentrations has been verified for causing some difficulties. The incentive to establish more accurate estimates of parental bulk rock concentrations using in-situ zircon measurements is significant as it would link zircon to a large body of whole rock geochemical literature with numerous possible applications including studies of magma source, crustal thickness, mineral exploration, crustal evolution, metamorphism, and petrogenesis (Chapman et al., 2016 and references therein). In this research, we determined the contents of REEs, Y, Nb, Ta, Hf, U, and Th in the zircon grains of eight granitoid samples from the Sangan mining district, NE Iran, to calculate zircon/rock partitioning coefficients of REEs applicable to magma source studies and mineral exploration.

Zircon from Sarkhar and Bermani granitoids were analyzed at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan, using laser ablation system, ICP-MS instrument (Agilent 7700a ICP-MS). Also, samples from Sarnowsar granitoids were analyzed at the Nanjing Hongchuang Geological Exploration Technology Service Co. Ltd., China. Zircons were analyzed for trace elements using a laser energy density of 3.6 J/cm2, a spot size of 30 μm, and a repetition rate of 5 Hz.
The estimations of melt composition and the measured trace element concentrations in zircon, values of DCezircon/rock was calculated. Estimates for DCe3+zircon/rock and DCe4+zircon/rock were implemented after Ballard et al. (2002) method. Partition coefficients of the trivalent REEs and the quadrivalent series Hf, Th, and U are used to constrain DCe3+zircon/rock and DCe4+zircon/rock, respectively. Blundy and Wood (1994) showed that the mineral melt partition coefficient for a cation i can be related to the lattice strain energy created by substituting a cation, whose ionic radius (ri) differs from the optimal value for that site (r0) (Equation 1).
lnDi=lnD0-4π ENA/RT (ri/3+r0/6) (ri- r0)2                                                                                     (1)
Plotting lnDi against the (ri/3 +r0/6)(ri−r0)2 yields a linear relation for an isovalent series of cations. With knowing the ionic radii of Ce3+ and Ce4+, partition coefficients of these species can be determined by interpolation. Since Ce will be a mixture of Ce3+ and Ce4+, the value of DCezircon/rock will lie between these two-partition coefficient end-members, and by combining Equations (1) and (2) oxygen fugacity fO2 of crystallization can be estimated.
ln[xmelt Ce4+/ xmelt Ce3+]= 1/4 ln fO2 + 13136 (±591)/T − 2.064 (±0.011) NBO/T −8.878(±0.112).xH2O −8.955 (±0.091)                                                                                                                                              (2)
Temperatures were calculated using the Ti content of zircon, by using the Equation (3) (Ferry and Watson, 2007):log(Tizircon) = (5.711 ± 0.072) – 4800 ± 86/T −logaSiO2 + logaTiO2                                                     (3)
where Tizircon is the concentration of Ti in zircon in ppm, T is temperature degrees in Kelvin, and ai (aSiO2 and aTiO2) is the ratio of component i concentration in the melt over the concentration of component i in the rock at saturation.

Concentrations of trace elements in the zircon grains are given in the Supplementary Table and are summarized in Table 1, where the geometric mean (G), the variation coefficient CV (which corresponds to the ratio of standard deviation by the arithmetic mean), and the number of determinations (n) are listed. Heavy rare earth elements (HREEs) show a relative enrichment. (Lu)N in the Sarnowsar granitoids range from 1522.40 to 8869.00 (DA sample), 1477.00 to 6442.00 (TP sample) and 1655.37 to 53.00 7523 (CSK sample). These values for Sarkhar and Bermani granitoids are in the range of 835.43 to 4077.95 (BR-01 sample), 1233.46 to 4337.80 (SK-01 sample), 1984.37 to 5681.81 (SK-1-1 sample), 2281.71 to 4955.97 (SK-1-2 sample) and 2268.68 to 6422.57 (SK-2-2 sample). Furthermore, the LREEs show lower concentrations, resulting in an (La/Yb)N that is generally less than 0.1. A negative Eu anomaly and a positive Ce anomaly are observed in studied granitoids. Contents and patterns of REEs in the studied granite samples are similar to those reported by other authors with higher HREEs contents than LREEs (e.g., Hoskin and Schaltegger, 2003).
Zircon Ti concentrations used to constrain its crystallization temperatures, and T is calculated by the revised Ti-in-zircon thermometry of Ferry and Watson (2007) (Supplementary Table). Calculated Ti-in-zircon temperatures for Sarnowsar intrusions (736° to 915 °C) are higher than those of Sarkhar (646° to 819 °C) and Bermani granitoids (653° to 861 °C). The △FMQ values (calculated by equation of Trail et al., 2011; Trail et al., 2012) for Sarnowsar range from -0.06 to 17.01. For Sarkhar and Bermani intrusions, the △FMQ values are in the range -4.43 to 4 and -8.53 to 0.07, respectively. These data indicating different magmatic conditions for productive (Sarnowsar) and barren (Sarkhar and Bermani) granitoids.

Defining the magma source and fertility of acidic to intermediate magmatism within the Cenozoic volcano-plutonic magmatic belts of Iran has immense scientific and mineral exploration significance. By using the zircon/whole rock partition coefficient in the Sangan mining area (Sarnowsar, Sarkhar and Bermani granitoids), we discuss the magma source and fertility of magmatism. The magmatism of Sangan mining district area is alkaline and classified as I-type granitoids, which have a direct genetic association with iron skarn mineralization in the area. The current results show that Sarnowsar granitoid was formed at a higher temperature (736° to 915 °C), lower negative Eu anomaly (with geometric mean 0.35 to 0.4), higher values ​​of Ce4+/Ce3+ (25.56 to 718.62) ratios compared to Sarkhar and Bermani granitoids. Also, the Sarnowsar granitoid has lower Hf values ​​(700 to 1199 ppm) and higher Zr/Hf (65 to 87) values, which shows that it formed in an earlier magmatic stage compared to Sarkhar and Bermani granitoids. The results of this research can be used for identifying productive Cenozoic intrusions in Iran that are related to porphyry and skarn mineralization systems.

The most important Manto-type deposits are located in the Coastal and Central Cordillera, northern Chile. Manto-type copper deposits have been reported in Iran in Saveh-Jiroft zone, the volcanoes of eastern Iran, the volcanic-intrusive complex of Alborz-Azerbaijan, Sabzevar zone, and Sanandaj-Sirjan zone. Nasim copper deposit is located in the northwest of Bardaskan, northeastern Iran. The deposit is part of the Iranian Plateau, Sabzevar Subzone, and Oryan region, located at the end part of the Khaf-Kashmar-Bardaskan magmatic belt. The geological units in the area include the Late Tertiary (Paleocene-Eocene), volcanic rocks, and sedimentary rocks including conglomerate and limestone. In Nasim deposit, mineralization has been done in conglomerate unit as a particular horizon. This unit is composed of volcanic fragments with carbonate and volcanic cements. Chalcocite is the most important and main sulphide mineral in the study area. Alteration can be divided into pre-mineralization and syn-mineralization stages. Pre-mineralization includes Celadonite, Carbonate, Silicified, and Propylitic alteration. Syn-mineralization consists of small amounts of Chlorite, Zeolite, and Calcite. In this system, the chemistry of solution is different from those of other systems such as IOCG, massive sulfide, porphyry etc., due to completely reduced and iron and silica-deficient solution.

Nasim deposit is located in northeastern Iran, 50 kilometers northwest of Bardaskan. The study area is part of the Iranian Plateau, Sabzevar subzone, and Oryan region, which is located in the end part of the Khaf-Kashmar-Bardaskan magmatic belt. The most important Manto-type deposits of Iran are located in Bardaskan region. The study area includes Paleocene-Eocene volcanic rocks, major volcanic and minor intrusive fragments. In this study, the chemistry of solution was investigated based on alteration and paragenesis in Bardaskan region.

This study was done in two parts: field studies and laboratory works. Sampling and structural studies were done while doing field studies. Logging drill cores was done for about 1000 meters in 20 boreholes. After field work, a total of 150 thin sections and 50 polished sections were prepared and studied to investigate petrography and mineralogy and to prepare geological map.
 

Geology of the area includes sequence of volcanic rocks of basalt, basaltic-andesite and andesite, respectively, formed in a non-marine environment. Conglomerate and limestone units formed after volcanic activity. Mineralization occurred only within the conglomerate unit due to useful porosity. Mineralization formed clearly post-dates conglomerate and limestone in the region. Chalcocite is the most important primary copper mineral in Manto Chalcocite systems, which has a high amount of copper and lacks iron. Mainly in the conglomerate unit, due to the good porosity of the conglomerate, the solution has risen up through the faults and penetrated into the conglomerate. Limited mineralization is observed in the carbonate rock. The mineralizations have no time and origin relationship with the volcanic cycle and the time of conglomerate formation. The porosity in the conglomerate and the fault structure in the region have played an important role in the mineralization.
Manto copper solution is a solution poor in iron and poor in silica, and it is completely reducing. This solution cannot react with lime under any conditions; so the mineralization rate is very low in lime, and this shows that the solution has a special chemistry.
Some exploration consultants have used the word agglomerate instead of conglomerate in Bardaskan. This is not acceptable because agglomerate is created during volcanic activity and its fragments consist of only one type of composition and have a rounded state (volcanic bomb). But conglomerate is formed during the erosion cycle and all the pieces are rounded when transported by river water or on the seashore. The use of the term agglomerate becomes a fundamental problem regarding the time and manner of formation of copper mineralization. Not knowing the exact time of Qata mineralization challenges the exploration.
 Alteration assemblage do not consist of epidote and quartz due to the lack of iron and silica in the solution. Moreover, the reducing solution is due to the presence of organic substances. Some researchers (e.g., Wilson and Zentilli, 2006; Tosdal and Munizaga, 2003) suggest a volcanic origin for Manto-type deposits. The volcanic rocks contain at least 5% primary magnetite. If the rocks are the origin, the solution will be rich in iron, but there is no evidence of iron-bearing minerals such as chalcopyrite and pyrite in the area.
Other researchers (e.g., Palacios, 1986; Oliveros et al., 2008) see intrusive rocks as the origin of these deposits. If the rocks are the origin, solution will be definitely rich in silica, iron, and aluminum, but there is no evidence of quartz-chalcocite mineral assemblage. Therefore, the determination of the origin of the deposits requires further studies and consideration of other factors.

We would like to thank Ferdowsi University of Mashhad and Kome Madan Pars Company for cooperating and supporting this research. We thanks the reviewers and editor(s) for their thoughtful contributions.