فهرست مطالب معصومه آهنگری

One of the significant challenges in mining areas is the pollution of the environment by heavy metals. Therefore, it is crucial to assess the pollution risk associated with mining wastes and take action to mitigate their environmental impact. The current study assessed the risk potential of recently deposited tailings in the Songun copper mining area.

Based on the conditions of tailings, 26 samples were randomly selected from the recently deposited mine wastes. Twenty-two thin and thin polished sections were prepared for lithology and mineralogy studies. Inductively-Coupled Plasma Mass Spectrometry (ICP-MS) was employed to analyze all 26 samples, while X-ray diffraction method (XRD) was used to analyze a subset of 10 samples.

Sulfide minerals, as the main source of environmental pollution, remain intact and unaffected in the tailings. However, the majority of potentially toxic elements (PTEs) exhibit higher concentrations in the waste composition than the standard levels, resulting in a total ecological risk index of 49.93. Geochemical indicators highlight significant pollution levels for elements such as lead (Pb), arsenic (As), and copper (Cu). The values of the non-carcinogenic risk index for children (except As and Fe) and adults are lower than 1, indicating a non-significant non-carcinogenic health risk. However, the carcinogenicity index also indicates a significant carcinogenic risk in the case of long exposure to wastes, particularly for children.

Therefore, wastes pose a significant environmental risk potential, and due to this risk, proper management of their storage is necessary to prevent the release of PTEs into the environment.

The outcropping mica schists from the Silvana region, which are a component of the Silvana colored mélange complex, are situated southwest of Urmia. This region is located in the northwesternmost part of the Sanandaj-Sirjan metamorphic belt. Mica schists can be classified into three sub-types based on petrographic studies: muscovite schists, biotite-muscovite schists and fibrolite-biotite-muscovite schists. Mylonitic zone can be identified by the presence of mylonitic foliation and microstructures such as mica fish, dynamic recrystallization, asymmetrically tailed porphyroclasts, kink bands, and microfolds. The Silvana mylonites are categorized as low to medium grade mylonites based on textural and microstructural evidence. According to the structural and microstructural relations, the study area appears to have been impacted by three main phases of deformation. The first phase can be characterized by a transpressional deformation regime, leading to the formation of S1 foliation in mica schists. The dextral main simple shear component can be attributed to the second phase. During this phase, S2 foliation, mylonite zones and various folds and microfolds were developed. Ultimately, multiple fractures and microfaults were caused by the third phase of brittle deformation that affected the study area.

Felsic igneous rocks record crustal evolutions and provide an important tool for determining the composition and modification of the crust (Zhang et al., 2018). Up to now, several classifications have been proposed for granites and rhyolites. Alphabetic classification is the most common approach used by petrologists. In this approach, granites and rhyolites have been divided into I, S, M, and A-types according to their geochemical, mineralogical composition, and origin characteristics (Loiselle and Wones, 1979; White, 1979). A-type granites and rhyolites include a wide range of felsic rocks. Currently, the formation of A-type suites has been attributed to both with-in-plate (anorogenic) and postcolision (orogenic) settings (Eby, 1990; Bonin, 2007; El Dabe, 2015).In this study, petrological characteristics of Noraldinabad rhyolites have been studied. These rhyolites exposed adjacent to Gushchi granitoids, which petrologically, have been studied before (e.g. Advay et al., 2010; Shafaii Moghadam et al., 2015). These studies exhibit that the Gushchi granitoides are A-type and formed in an extensional rift-related setting. Nevertheless, there is not any comprehensive study on the Noraldinabad rhyolites and the present study would be the first effort to constrain the geochemical characteristics of these rocks. 

Regional Geology:

The area of study, in aspect of lithological characteristics as well as geological structures has attributed to various zones e.g., Khoy-Mahabad zone (Nabavi, 1976), Sanandaj-Sirjan Zone (Alavi, 1991), and junction of the structural zones of Sanandaj-Sirjan and Central Iran (Alavi-Naini, 1972). Nabavi (1976) believes that the lithological characteristics of Central Iran, Sanandaj-Sirjan, and Alborz-Azerbaijan zones are visible in the northwest of Iran. In this case, the observed geologic successions in the northwest Iran are similar to those of the of Central Iran zone (Shafaii Moghadam et al., 2015). The exposure of Kahar Formation (Late Neoproterozoic) is common in the northwest of Iran, Central Iran, Alborz, and Sanandaj-Sirjan zones (Shafaii Moghadam et al., 2015). However, according to Sabzehi and Mohammadiha (2003), the main characteristics of the Sanandaj-Sirjan zone are not visible in this region but could be considered as the northwest termination of the Sanandaj-Sirjan zone.

Following the field observations and collecting several rhyolite samples microscopic studies were performed to determine petrographic features. Also, 10, least altered rhyolite samples, were selected for whole rock analyses, including XRF and ICP-MS, performed at the Zarazma Zanjan laboratories (Zanjan, Iran).

Petrography:

The Noraldinabad rhyolites display porphyritic texture with quartz, alkali feldspar, and subordinate plagioclase phenocrysts. Opaque minerals and zircon are the main accessory minerals. Altered mafic minerals can be seen in some samples. The matrix is composed of medium- to fine-grained quartz and alkali feldspar. Secondary minerals, mostly sericite and chlorite, are ubiquitous in the matrix of some samples. Along with porphyritic texture, flow-alignment (in the matrix of some fine-grained samples), spherulitic (in the matrix of medium-grained samples), embayed, Perthitic, and subordinate granophyric textures are the main visible textures.

Whole rock chemistry:

The Noraldinabad rhyolites have high SiO2 values, consistent with “high silica rhyolitic systems” (SiO2 > 70 wt%) (Gualda and Ghiorso, 2013; Arakawa et al., 2019). The Al2O3 content of the studied rhyolites is lower than of \ this oxide in calc-alkaline rhyolites (> 14 wt%) (Philpotts, 1990). Based on alkali elements content, the rhyolites under study can be divided into two groups: Na2O- and K2O-rich, in concordance with petrographic studies. The K2O-rich samples are dominated by the presence of K-feldspar whereas the Na2O-rich samples are characterized by high numbers of anorthoclase. Except for alkali elements, the contents of other major elements in these two groups are not significantly different. Except for one sample (0.54), the FeOt/(FeOt+MgO) ratio is high and varies between 0.73 to 0.94. All analyzed samples have high A/CNK ratios, indicating their peraluminous characteristics. The studied rocks show shoshonitic magmatic series affinity and are characterized by LREEs enrichment and HREEs depletion with obvious negative Eu anomaly in the chondrite-normalized diagrams. In the NMORB-normalized trace element spider diagram, the samples display enrichment in LILEs, Ba, Nb, Ta, Sr, Zr, Hf, Eu, and Ti negative anomalies, weakly Rb and Pb positive anomalies. The Eu, Sr, Ba, and Ti depletion indicates plagioclase and titano-magnetite fractionation, respectively (Shafaii Moghadam et al., 2015).

The remarkable geochemical features of the Noraldinabad rhyolites are high amounts of SiO2, Na2O+K2O, Fe2O3t and low abundances of CaO, MgO, and P2O5. Furthermore, the concentration of REEs (except for Eu) and LILEs are high, and the contents of Sr and Rb, and compatible elements (i.e., Co, Sc, Cr, and Ni) are low. These geochemical features disclose the A-type nature for the studied rhyolites (Loiselle and Wones, 1979; Eby, 1990; Bonin, 2007). Genetically, considering the high ratios of Y/Nb, Rb/Sr, Rb/Nb, and relatively low amounts of Nb, the investigated rocks can be attributed to the A2-subtype of the A-type rhyolites.The low Sr concentration, negative Eu anomaly and HREEs flat- pattern indicate a garnet-absent and plagioclase-bearing, as a residue of partial melting, origin for studied rhyolites which confirmed these rocks formed by partial melting under shallow depth and low-pressure conditions (Norman et al., 1992; Petford and Atherton, 1996; Jia et al., 2019). The Y/Nb ratio is helpful to determine the characteristics of parent magma (Eby, 1990). Granitoids derived from mantle have Y/Nb<1.2, while crustal granitoids have Y/Nb > 1.2. The Y/Nb ratio in the Noraldinabad rhyolites varies from 1.30 to 4.72 compatible with crustal origin. Additionally, the trace element ratios (i.e., Th/U, Nb/U, Y/Nb) are similar to those of the continental crust composition.Considering tectonic setting discriminant diagrams, the studied rhyolites are anorogenic and formed in within-plate related to rift-related extensional environment. The presence of bimodal magmatism in the studied region, along with the exposure of coeval A-type granites and rhyolites in northwest Iran, can confirm the formation of the studied rhyolites in a continental rift (possibly Neotethys rift) setting.

The volcanic rocks with the Plio-Quaternary age, are exposed in the northern part of the Sanandaj-Sirjan zone, in northwest Urmia. The main mineral phases are olivin + clinopyroxene ± plagioclase, that are present as both phenocrysts to microcrystalline with other minor minerals. The dominant textures of these rocks are porphyry, microlithic porphyry, hyalo-porphyry, glomeroporphyritic and vesicular. Based on geochemistry, the parent magma of these rocks are in the range of trachy-basalt to basaltic trachy andesite, belonging to the alkaline magmatic series. The mantel and chondrite normalised patterns of rare earth elements indicates the enrichment of LILE and LREE as well as the depletion of HFSE and HREE.The spider diagrams show a negative anomaly in Nb, Ta, P, Rb, Zr and Ti and positive anomaly in Pb, La, U, Nd, Th and Cs. These geochemical parameters and tectonic diagrams show that the Plio-Quaternary alkaline magmatism were formed in the post-collision arcs.

Amphibolites crop out in the NW Salmas as two relatively small bodies around Abati and Ureban villages. Based on petrography and mineral paragenesis, the composition of Abati and Ureban amphibolites consists mainly of epidote amphibolite and amphibolite, respectively. Relict of clinopyroxenes from a parental rock are present in some samples. Mineral paragenesis (high hornblende and plagioclase and low quartz content) along with whole rock chemistry of the NW Salmas amphibolites show that the protolith was a basaltic composition with calc-alkaline to tholeiitic affinities. The original magmas of the NW Salmas amphibolites were not primary, and the composition of magmas has been modified by fractional crystallization and crustal contamination during ascending and emplacement. According to the discrimination and multi-element diagrams patterns (enrichment of LILEs in comparison with HFSEs and the negative anomaly of Nb and Zr), the parental magmas of the NW of Salmas amphibolites were generated in subduction-related tectonic settings.

Qushchi gneisses in the north of Urmia city are a part of magmatic-metamorphic complex in NW of Sanandaj-Sirjan zone. Gneiss, with amphibolite and schist, form Precambrian basement of the area. These rocks contain lipidogranoblastic, augen, porphyroblastic and myrmekite textures, and composed of quartz+ alkaline feldespars (microcline and orthoclase perthites) + plagioclase+ biotite± pyroxene+ muscovite± amphibole± epidote +zircon+ opaque. Field, petrography and geochemical evidences were used to know the genesis of igneous (ortho) or sedimentary (para) of these gneisses. All the evidences imply an igneous origin (ortho) for the studied gneisses. In fact, the protolith of these gneisses are porphyritic granite to monzonite rocks and has calcareous-alkaline and peraluminous nature. It can be inferred that the protolith of these rocks which formed in the late Neoproterozoic, belong to the calc-alkaline magmas in active continental margins or volcanic arcs (VAG). Further tectonic events have transformed them into gneisses.

Qareh-Dash rhyolites from the Shahindej area are peraluminous rocks with high SiO2 and K2O contents. These rocks are mainly composed of quartz, K- feldspar and rare plagioclase phenocrysts in a fine-grained K-feldspar rich matrix. Geochemically, Qareh-Dash rhyolites show enrichment in LREEs and LILEs and depletion in HREEs.
Field studies, textural and petrographical relations, along with whole rock geochemistry, demonstrate that the parental magma of the Qareh-Dash rhyolites was originated from the crust. The composition of the parental magma was modified due to fractional crystallization of plagioclase and titanomagnetite evidenced by negative Eu, Sr and Ti anomalies in multielement diagrams. The chemical characteristics of Qareh- Dash rhyolites such as Rb/Nb, K/Rb, Rb/Sr, Rb/Ba and Ga/Al ratios are similar to A-Type granites/ rhyolites associated with post- collision tectonic settings. According to Precambrian age for the Qareh-Dash rhyolites, formation of these rocks might be related to extensional phases which were probably taken place after closure of proto- Thetys Ocean.

The exposed volcanic rocks in south west of the Khoy area consist of basalts with minor amounts of plagioclase-phyric basalts. These rocks are composed of clinopyroxene plus plagioclase and plagioclase phenocrysts, respectively. The basaltic rocks are highly altered and contains high amounts of secondary minerals mainly chlorite and epidote. According to mineral chemistry, the composition of clinopyroxenes varies from diopside to augite. The clinopyroxenes are characterized by normal zoning and were formed from a primitive subalkaline magma. The studied clinopyroxenes were crystalized at pressure of 2 to 5 kbars, temperature ranging from 1100- 1150 °C and high oxygen fugacity. On the tectonic setting discrimination diagrams, the south west of Khoy basalts plot mainly in the areas of overlap between IAT, BABA and MORB. The comparison between studied basalts and basaltic rocks in the Khoy ophiolitic complex reveal that the south west of Khoy basalts might have been formed in back- arc basin settings.

Amphiboles in olivine-bearing hornblende- gabbros from NW of Salmas were crystallized in various textures including oikocryst and interstitial textures in the matrix, outer part of reaction rims around olivine, and at the rim and cleavages of clinopyroxene. On the basis of petrographical and textural studies, amphiboles were formed later than the other minerals in the olivine-bearing hornblende- gabbros. The REE and trace element composition of amphiboles from two different textures including interstitial and matrix amphiboles (group one) and amphiboles after clinopyroxenes (group two), indicate that the studied amphiboles were formed by either crystallization of interstitial melt/fluid or interaction of interstitial melt/fluid with early crystalized minerals such as clinopyroxene and plagioclase. Hence, according to the textural and mineralogical data and trace element composition of amphiboles, olivine-bearing hornblende- gabbros were crystallized at least at two stages. The first stage include fractional crystallization and formation of olivine, clinopyroxene and plagioclase and the second stage was interaction of the relict melt/fluid with early crystalized minerals, specially clinopyroxene and plagioclase and formation of amphibole

Rare earth and trace element concentrations of mineral assemblages including amphibole, plagioclase, epidote group minerals (zoisite and clinozoisite) and relict clinopyroxenes from parental rock of epidote amphibolite from north of Urumia were obtained in situ by LA-ICP-MS analysis. The obtained data were used to study distribution of trace elements among metamorphic phases and relict clinopyroxenes from parental rock. In the studied rocks, compatible elements (Sc, V, Ni and Cr), HSFE (Ti, Ta, Hf and Nb) and MREE were concentrated in amphibole, LREE and LILE were collected into plagioclase and epidote group minerals were gathered HREE accompanied with Eu. The observed REE trends in epidote group minerals in north of the Urmia epidote- amphibolites are unlike to common reported trends for this mineral group in the other parts of the world. Rare earth element geochemistry of the epidote group minerals from the north of Urmia indicates enrichment of HREE and MREE relative to LREE. Relative similarities for rare earth and trace element concentrations of amphibole and relict clinopyroxenes from parental rock indicates that the geochemical features of amphibole were inherited probably from primary clinopyroxenes.

The studied mylonite granites are exposed as small bodies at the west of Qushchi in the West Azarbaijan Province. These rocks contain orthoclase, microcline, plagioclase, fish muscovite, tourmaline ± garnet as porphyroclast. The matrix is composed of recrystallized quartz, fine grained muscovite and low abundant epidote. According to petrographic and mineral chemistry studies and BSE images, tourmaline and garnet are chemically zoned. The mineral chemistry characteristics of core of tourmaline and garnet crystals indicate magmatic origin for them, while the composition of rim part for these minerals, especially for garnet, is consistent with metamorphic origin. Presence of tourmaline muscovite ± Mn-rich garnet in the West Qushchi mylonite granites and occurrence of these rocks as small bodies within metasedimentary rocks suggested that the west Qushchi mylonite granites are formed by low grade partial melting of the metamorphic rocks. On the basis of the mineral assemblage, it seems that the studied rocks belong to Mg-poor peraluminous leucogranite type rocks.

The Nabijan gabbroic and dioritic plutons outcropped at the southwest Kaleybar town. According to the field studies the diorite is younger than gabbro and crosscut the gabbroic pluton. Geochemical data reveal clear geochemical difference between the Nabijan gabbroic and dioritic compositions. Variations of major oxides versus SiO2 and Mg# and trace element ratios indicate that the composition of Nabijan intrusive bodies were modified by fractional crystallization and crustal contamination (AFC) processes. However the geochemical characteristics of the Nabijan plutons suggest a same source for them. According to mineralogical and geochemical data¡ fractionation and/ or accumulation of olivine¡ orthopyroxene¡ clinopyroxene and Ca-rich plagioclase at the first stage has formed the gabbroic body. Due to fractionation of the above mentioned minerals¡ the composition of the remained magma has enriched by fluids and incompatible elements. At the final stage the Nabijan diorites has formed by crystallization of amphibole¡ biotite¡ Na-rich plagioclase accompanied with minor amounts of clinopyroxene. The fractionation/accumulation of the mentioned mineral associations has caused to possess tholeiitic and calc-alkaline character for the Nabijan gabbroic and diorites¡ respectively. The geochemical features of the Nabijan intrusive rocks show hybrid characteristics among active continental margin and within plate tectonic settings. These features can visible in continental post-collision settings.

There are several intrusive plutons in the Saheb- Yapesh-khan area, which are compositionally made from mafic to acidic rocks, including granite, tonalite, syenodiorite, monzodiorite, quartz diorite, diorite and to a lesser amounts gabbros. The main rock type of the area is granite. The intrusive rocks were formed at the Island- Arc (ACM) environment in terms of tectonic setting. The parental magma was primitive and formed by low degree partial melting (less than 5%) of metasomatized mantle with spinel- garnet- phlogopite lherzolite composition. The mantle source was metasomatized by influx of dehydration of sediments and the rocks of the subducting oceanic slab. The crustal contamination had a meager effect on modification of the original magma composition. On the basis of variation diagrams of the studied igneous rocks, there are two main petrogenetic trends (mafic and felsic series) for the studied intrusive rocks. It seems that these trends are formed due to fractional crystallization and separation of amphibole and plagioclase from the primary magma.

According to the olivine and spinel chemistry, two types of peridotite were identified from west north Piranshahr ophiolite. Peridotite rocks are classified based on chemistry of spinel and olivine. Average number of Cr in spinels (Cr#[(100*Cr/(Cr+Al))]) and Mg-number (Mg#[100*Mg/(Mg+Fe)]) in dunite are 0.63 and 0.51 respectively. In harzburgite, Cr# is 0.33 and Mg# is 0.67 and in spinel from serpentinite Cr# is 0.45 and Mg# is 0.55. Also in dunite, Cr/Al is 1.6, in harzburgite Cr/Al is 0.49 and in spinel from serpentinite Cr/Al is 0.81. According to chemistry of spinel and olivine, there are two types of peridotite with different tectonic setting in the Piranshahr ophiolite (which age is upper cretaceous). Discriminant diagrams indicate that dunite is supra-subduction peridotite with a forearc setting, whereas harzburgite and serpentinite are abyssal peridotite. Two different tectonic settings in peridotites of this region are comparable with the Oman ophiolite in Oman-Zagros ophiolitic belt.

Olivine is one of the major crystals in ultrabasic rocks of Piranshahr Ophiolitic Complex. This mineral occurs as anhedral with cracks and fractures. Commonly, olivine is altered to serpentine along the fractures and rims. In some cases, serpentine crosscut the olivine. According to BSE images and mineral chemistry studies of olivine, the secondary iron- rich olivines occur at the rim of primary olivines. The forsterite content of the secondary olivines is lower than the primary olivines. XFo in the secondary olivines varies 85.6 to 87.7. Textural studies suggest that iron- rich olivines formed during serpentinization. Occurrence of Mg- rich serpentine and lack of magnetite during serpentinization of olivine caused formation of Fe- rich fluids. The iron- rich fluids may infiltrated through the olivine crystal and formed iron- rich rims.

Zoisite and clinozoisite are coexistent in the Salmas epidote- amphibolites, NW Iran. The frequency of zoisite is higher than clinozoisite in the studied epidote- amphibolites. The pistacite content of zoisite is lower than clinozoisite. XPs in zoisite is about 6.46-10.65% while for clinozoisite it is about 16.72-18.73%. Al-Fe3+ substitution was effective to create the mineral compositional changes in the Salmas epidote group minerals. Composition of coexisting zoisite and clinozoisite is a function of pressure, temperature and whole rock composition. According to zoisite and clinozoisite phase relations and compositions, epidote- amphibolite metamorphism in the Salmas area occurred at temperature of 500±20 ◦C and pressure of 6.5-7 Kbar conditions.

Amphibolites and epidote amphibolites are the main exposures of metabasites in south of Salmas area. Mineral chemistry of these two rock groups is different، and shows differences in the P-T conditions during prograde metamorphism. Study of amphibole chemistry show increases of tschermakite and crossite end members in amphiboles from epidote amphibolites toward amphiboles within the amphibolite samples، while increasing of the edenite content during transformation from epidote amphibolite to amphibolite is negligible. On the basis of mineral chemistry، rising of temperature was more effective than rising of pressure in transformation of epidote amphibolites to amphibolites in the studied samples. According to geothermobarometeric studies، epidote amphibolites and amphibolites were metamorphosed at 500±20ºC، 2-5 (commonly less than 5) Kbar and 600±20ºC، 6-8 Kbar conditions، respectively.