geochemistry

The XVI-B anomaly iron ore deposit is situated within the Central Iranian structural zone, specifically in the Bafq region. This region is notable for its lack of a direct association between specific tectonic periods and iron ore deposits. The Bafq area contains 39 iron ore deposits with an estimated total reserve of 2 billion tons, making it one of the most significant iron ore extraction regions in Iran.
 

Prominent iron ore deposits in the area include Sechahoon (117 Mt), Chadormalu (400 Mt), and Choghart (216 Mt). The Bafq anomaly iron ore deposit is located within the Central Iranian structural zone. This study involved the collection of drilling core samples for ICP-MS analysis (conducted at Karaj Laboratory), thin-polish and thin-section preparations (54 samples), and XRF analysis (5 samples, also conducted at Karaj Laboratory). According to the structural-sedimentary unit classification of Iran, the study area lies within the central Iranian zone (Nabawi, 1976). This zone contains some of the oldest metamorphic rocks in Iran, dating back to the Precambrian (Aghanbati, 2004). The Bafq mineral district, a subset of the central-eastern Iranian microplate, has experienced tectonic evolution influenced by the Katanga orogeny and related movements over the past 600 million years (Taghavi, 2015). The region's Neoproterozoic–Early Cambrian mass magnetite deposits are predominantly found in volcanic rocks associated with mantle diapirism along caldera margins. Notable deposits include Chaghez, Chadormalu, Choghart, and Sechahoon (Torab et al, 2007). The dispersed mineralization of iron and rare earth elements in the Bafq mining area is directly linked to intracontinental rifting. Volcanism, magmatism, and regional tectonics, influenced by rift dynamics, played a significant role in the mineralization of igneous rocks (Samani, 1993). The XVI-B deposit is part of the Bafq mineral district, located within the central-eastern Iranian microplate. Stratigraphically, the area is divided into western, central, and eastern sections (Ramezani and Tucker, 2003). The oldest rocks (Neoproterozoic–Early Cambrian) are situated in the eastern part, while the youngest rocks (Eocene) are found in the west. Major faults, including the Nybaz-Chatak and Poshte-Badam faults, delineate these sections.

The region contains diverse igneous and metamorphic rocks. The igneous rocks include gabbro, diorite, syenite, quartz monzonite, granite, and highly altered basic rocks (metabasites). The metamorphic rocks are dominated by marble and skarn formations. The leucogranite, characterized by idiomorphic and graphic textures, contains plagioclase and sodic feldspar crystals alongside quartz, alkali feldspar, biotite, and secondary minerals such as sericite, clay minerals, epidote, and carbonates. Tectonic activity has resulted in cataclastic textures in some samples. Mineralization in the area is primarily associated with syenite, gabbro, and skarn rocks. The metallic minerals include magnetite, hematite, pyrite, and chalcopyrite, while non-metallic minerals such as quartz, actinolite, calcite, and epidote are also present. Mineralization and Geochemical Characteristics Iron mineralization predominantly occurs as magnetite, which is observed in massive, void-filling, and disseminated forms. Near the surface, magnetite undergoes oxidation, resulting in its transformation into hematite, goethite, and other iron oxides. Associated metallic minerals include pyrite and chalcopyrite, often found with quartz, actinolite, calcite, and epidote in host rocks, intrusive syenites, gabbros, and skarns.The total iron oxide content in the collected samples ranges from 25% to 75%, while silica content varies between 5% and 45%. Titanium concentrations are relatively low, between 0.1% and 0.5%, and exhibit a negative correlation with iron content. Potassium oxide levels range from 0.1% to 1.8%, and phosphorus content varies between 0.02% and 0.35%, indicating an absence of phosphate mineralization. Magnesium oxide levels range from 1% to 12%, largely attributable to the presence of ferromagnesian minerals such as amphibole and dolomite. Negative correlations between magnesium oxide and iron suggest minimal substitution of magnesium for iron in the mineral lattice. Aluminum and calcium oxides range from 2% to 12% and 2% to 26%, respectively. The ore samples contain cobalt (3–75 ppm), nickel (1–17 ppm), chromium (10–96 ppm), and vanadium (40–120 ppm). The behavior of rare earth elements (REEs) indicates hydrothermal alteration, with total REE content varying between 13.1 and 375.1 ppm. Enrichment in light REEs (LREEs) and depletion in heavy REEs (HREEs), alongside a positive Eu anomaly, are consistent with skarn-type deposits (Bea et al, 1996). This pattern suggests that REEs may substitute for elements in garnet, zircon, and magnetite structures.
 

The geological evidence indicates that the oldest rocks in the area are Precambrian metamorphic units, including gneiss, mica-schist, amphibolite, and migmatite, which form the bedrock of the mineralization anomaly. The deposit is covered by Tertiary and Quaternary sediments of the Bafq Basin. The alkaline diorite-syenite intrusive units play a significant role in hosting mineralization.The mineralization comprises a variety of igneous and metamorphic rocks, including gabbro, syenite, quartz monzonite, granite, marble, and skarn. Magnetite is the dominant iron oxide ore and is accompanied by pyrite and chalcopyrite. Oxidation near the surface leads to the formation of secondary iron oxides like hematite and goethite. The geochemical data suggest that the deposit is of hydrothermal origin, with characteristics aligning it with skarn-type deposits. Correlations among trace elements such as Co/Ni, Cr/Ni, and Cr/V, along with ratios like Al/Co and Sn/Ga, further support this classification. The REE patterns, including a positive Eu anomaly and LREE enrichment, are consistent with skarn-type mineralization and provide insights into the role of hydrothermal fluids in the formation process. This study highlights the skarn origin of the XVI-B anomaly iron ore deposit, emphasizing the significance of intrusive magmatic activity and hydrothermal processes in its formation. These findings contribute valuable insights for the geological modeling and economic evaluation of the deposit.

IntroductionThe Urumieh-Dokhtar magmatic belt is one of the most active magmatic regions of Iran during the Cenozoic era. There are differing views regarding the tectonomagmatic setting of this magmatism; some attribute it to active continental margin magmatism, island arcs, post-collisional regions, and intra-continental rifts (Hassanzadeh, 1993; Shahabpour, 2007; Ghasemi and Talbot, 2006). The study area as the other sections of the Urumieh-Dokhtar Belt, is the area of Eocene magmatic activity. The geochemical characteristics of volcanic rocks in the northeast of Tafresh are similar to those of magmatism in active continental margin subduction zones (Nasiri Bezanjani, 2006). In the eastern part of Tafresh, numerous dikes cut through Paleozoic and older sedimentary and volcanic units. K-Ar dating of these dikes indicates an age of 15.4 million years (Ghorbani et al., 2014). Babazadeh et al. (2022) have provided a U-Pb age of 17.5 million years for the mafic dykes. This study examines the petrology and geochemistry of the Mafic and intermediate dyke bodies located in the eastern part of Tafresh and discusses their tectonomagmatic setting.GeologyThe study area lies in the central part of the Urumieh-Dokhtar magmatic belt. Cenozoic sedimentary-volcanic deposits unconformably overlie Upper Cretaceous marly limestones due to the Laramide orogeny, which uplifted the region. Eocene units comprise   alternating marine and continental deposits of volcanic flows, pyroclastics, and sediments.Marine transgression during early Eocene introduced marl-sandstone units (E1), followed by dominant volcanic activities forming basaltic to rhyolitic flows and pyroclastics (E2). Continental red deposits and marine green layers alternate. Later, marine conditions resumed (E3), forming sedimentary layers with green tuffs, while subsequent continental volcanic phases (E4) produced dacitic flows and tuffs. Renewed marine sedimentation (E5) followed, then thick terrestrial volcanic layers of andesitic-basalts (E6).Extensive dykes, mostly basaltic-intermediate, intrude older units, with U-Pb dating indicating Miocene age (17.5 Ma).Analytical method8 samples with the least alteration were selected for analysis of major and trace elements. The analysis of major and trace elements was carried out using the ICP-MS method (LF200 analytical system) at the ACME-Bureau Veritas Laboratory in Canada. For the study of the chemistry of clinopyroxene, plagioclase, and amphibole minerals, 15 points were analyzed using an electron microprobe at the University of Milan, Italy.Petrography and mineral chemistryDiabase: These rocks display a doleritic texture with minimal groundmass. Plagioclase crystals dominate (70 vol.%). The other primary minerals include clinopyroxene and iron-titanium oxides, while amphibole, alkali feldspar, olivine, and apatite appear as accessory minerals. Secondary minerals, such as calcite, chlorite, and epidote, form from plagioclase and clinopyroxene alteration.Basaltic andesite: These rocks comprise plagioclase (60–70 vol.%), amphibole (10–20 vol.%), iron-titanium oxides (5–10 vol.%), and clinopyroxene (5–10 vol.%), with accessory alkali feldspar, olivine, and apatite. Phenocrysts make up to 40 vol.% of the total volume, primarily plagioclase and amphibole. Secondary minerals, including chlorite and epidote, are present in the groundmass.Andesite: The primary minerals in these rocks are plagioclase (70–80 vol.%), iron-titanium oxides (10–20 vol.%), and amphibole (5–10 vol.%), with minor pyroxene, alkali feldspar, and apatite in the groundmass. The matrix consists of plagioclase microlites and fine-grained oxides, with secondary minerals like calcite, epidote, and sericite.The clinopyroxene crystals are of the salite type, and the plagioclase crystals ranging in composition from labradorite to andesine. Additionally, the amphiboles are of the pargasite type.GeochemistryThe continuity of trends in Harker diagrams for the studied samples suggests a common origin. Increasing Na2O+K2O and decreasing MgO, FeOt, TiO2, Al2O3, and CaO/Na2O along with increasing SiO2 indicate that the crystallization and separation of ferromagnesian minerals (especially clinopyroxene) with feldspar and Fe-Ti oxides played a significant role in the magmatic evolution of these rocks.On TAS diagram, the samples are classified as basalt, basaltic andesite, and andesite. Using immobile elements on the Zr/TiO2 versus Nb/Y diagram, the samples fall within the basaltic andesite field. All samples plot in the sub-alkaline field on the alkaline-subalkaline discrimination line. On AFM diagram, the samples lie near the boundary between tholeiitic and calc-alkaline series. Based on K2O versus SiO2, they range from medium-K calc-alkaline to low-K tholeiitic compositions.The chondrite-normalized REE patterns show enrichment in LREE relative to MREE and HREE, with flat MREE-HREE trends. The spider diagram normalized to the primitive mantle reveals LILE enrichment and HFSE depletion.Source and Tectonomagmatic SettingThe gentle slope between HREEs and MREEs in the REE pattern is consistent with the magma's origin from a spinel lherzolite mantle with little or no garnet involvement. Furthermore, in the Dy/Yb versus La/Yb diagram, the studied rocks fall within the range of melts originating from a spinel lherzolite mantle, and in the Nb/La versus La/Yb diagram, they lie within the lithospheric mantle field.Based on Nb/Th ratio versus Nb and the Ba/Nb ratio versus La/Nb, the studied rocks are located in the volcanic arc-related rocks field. In the Th-Hf-Ta diagram, the samples are placed within the magmatic arc-related rocks field. Also, based on the Nb/La ratio versus La/Yb, the samples fall within the active continental margin-related rocks field. However, in the Th/Yb versus Ta/Yb diagram, the samples fall within both the island arc and active continental margin-related rocks fields. Overall, the studied rocks display some characteristics to those of Island arcs and some others to those of active continental margins.ConclusionThe rare earth element patterns indicate that the magma associated with these igneous rocks originated from partial melting of the shallow lithospheric mantle in the spinel peridotite facies, with minimal or absent garnet involvement. Additionally, the observed characteristics in the incompatible element patterns, such as enrichment of mobile elements over rare earth elements and depletion of immobile elements, along with analyses in various geochemical diagrams, suggest their association with subduction-related magmatism. However, the studied rocks display geochemical criteria belonging to island arc as well as active continental margin magmatismThe intermediate geochemical features of island arc and active continental margin magmatism, along with other evidence including the association of these igneous rocks with a thick sequence of green tuffs and other shallow marine sediments indicate that the rocks under study originated in an intra-continental back-arc basin

The Tangedozdan zinc and lead deposit is located 25 km northeast of Fereydounshahr and in the middle part of the Sanandaj-Sirjan zone. The rock units from old to new include greenish volcanics, calcareous sandstone, crystalline limestone, limestone to dolomitic limestone, and gray limestone belonging to the Jurassic-Cretaceous and alluviums of the Holocene time. The limestone to dolomitic limestone unit with normal contact sits on greenish volcanic and hosts zinc mineralization. The Zincian-dolomite in this area can be recognized by different amounts of zinc, smaller amounts of lead and, cadmium in its structure. In the studied area, a set of formed zinc and fewer lead ores, the most important in the exogenous part are smithsonite, hemimorphite, and cerussite, and in the endogenous part are sphalerite and, pyrite. Performing XRD analysis with the conventional method shows the presence of dolomite, smithsonite, and sphalerite. By changing the decomposition conditions, the structure parameters in Zincian-dolomites increased simultaneously with the amount of zinc, based on of this, there is a direct relationship between the zinc amount in the dolomite and the structure parameters. The study of the Zincian-dolomite sample by differential thermometry method shows the reduction of endothermic point and the zinc effect substitution in the dolomite structure. EPMA analysis of Zincian-dolomite samples show the substitution of Mg with Zn. Based on this, the replacement of dolomite by exogenous zincian-dolomite is a part of the mineralization process, and with the progress of zincian-dolomite formation and dolomitization, it eventually leads to the formation of non-sulfide zinc minerals such as smithsonite.

The Dogan copper-molybdenum deposit is located in the northern Central Iranian magmatic arc, south of Shahrood. Mineralization in this area is caused by the injection of a microdioritic subvolcanic intrusion into Eocene volcanic rocks. Mineralization occurs frequently as veins, veinlets, and disseminated ores and is mineralogically composed of primary minerals like pyrite, chalcopyrite, bornite, and molybdenite as well as secondary minerals like chalcocite, iron oxides and hydroxides, and malachite. The alteration zoning in the Dogan deposit is circular and concentric and changes from potassic in the central part to phyllic alteration and then propylitic alteration in the margins. Some parts of argillic alteration are observed in the upper and surface parts of the phyllic zone. The fluids producing potassic alteration were rich in liquid and a small amount of steam (L + V), had a high temperature (398 to 513ºC), and a high salinity (50 wt% NaCl), according to fluid inclusions studies. These fluids were most likely magmatic in origin and were responsible for the formation of the V1 and V2 veins. The activity of meteoric fluids containing liquid vapor phases (V + L) with lower temperature (210 to 360°C) and salinity less than 10 wt % NaCl causes phyllic alteration (V3 veins). In terms of geochemistry, the studied igneous samples are adakititc in nature and are located in the domain of calc-alkaline magmas of the active continental margin. The presence of potassic alteration in surface and deep cores, the high salinity and temperature of hydrothermal fluids, the type of mineralization (disseminated and vein-veinlet), the high potential of copper and molybdenum, and the zonation of existing alterations are all indicative of a porphyry system. The Dogan mining area is similar to copper-molybdenum porphyry deposits in terms of tectonic environment of formation, host rock type, texture and structure, mineralogy, and alteration zonation.

This study deals with the results of Raman laser spectroscopy, BSE electron images, EPMA and WDS elemental mappings to characterize the micromorphology, mineral chemistry, and the distribution pattern of Mn, Fe, Mg, Al, Cu, Ni, Co, Sr, Ti, P, Si, V, and Pb in the Mn-nodules of Nasirabad manganese occurrence located to SE of Zagros thrust belt near the Neyriz ophiolite. The results of micromorphology indicated that the studied nodules are of multi-core structure dominated by the accumulation of siliceous microfossils and spheroidal colloform textures. In the core areas, Mn-minerals are fine-grained containing mostly todorokite, pyrochroite, pyrolusite, and ramsdellite. On the contrary, to the marginal parts, the Mn-minerals are coarser and consist mainly of pyrolusite, and ramsdellite. Results imply for the depletion of Fe, Pb with Cu, Ni, and Co, which may indicate the contribution of distal hydrothermal fluids in the formation of nodular structures. Additionally, evidences such as the diagenetic replacement of siliceous microfossil shells with manganese oxide minerals, especially todorokite, shows the role of diagenetic fluids in the evolution of nodular structures. No sighting of rhodochrosite along with the absence of enrichment patterns in the bio-essential elements (e.g., iron, arsenic, barium, strontium, cerium and cobalt) imply for the absence or insignificant role of biological-microbial processes in the formation of studied nodules.

The study area is located in the south of Mamouniyeh and middle part of the Urumieh-Dokhtar magmatic Arc. The Oligo-Miocene intrusive rocks have combined domain of gabbro, gabbroic diorite, diorite, monzonite, monzodiorite and quartz monzonite with calc-alkaline nature and they are metalaluminous type, which microscopic evidence shows granular, heterogranular, hypidiomorphic, intersertal and porphyry textures in them. A notable feature is the LILE enrichment in comparison to HFSEs, a characteristic of calc-alkaline rocks from continental margin subduction zones. Positive Pb anomaly indicates contamination of the magma by crustal material, while the scarcity of elements such as Ti, Nb implies an altered lithospheric mantle source located above the subduction zone. The Ba/Nb > 28 and Ba/Ta >450 indicate an active continental margin. A faint Eu anomaly, bending chondrite-normalized REE pattern, and balanced La/Yb ratios suggest a high-water content in the source magma. It appears that the origin of the magma involves the partial melting of low-grade spinel lherzolite mantle at a depth of 60-70 km. Geochemical analyses, align these granitoids with the active continental margin, stemming from Neotethys oceanic crust subduction beneath the central Iranian plate. This subduction facilitated mantle wedge metasomatism and partial melting through fluids released from the subducting oceanic crust.

Abundant intermediate volcanic rocks – andesite and basaltic andesite – are exposed in the Bukan area in northwestern Iran. Major and minor element analyses of bulk rocks show they have subalkaline and High-K calc-alkaline features. Both compositional groups have phenocryst assemblages that include pyroxene, amphibole and plagioclase feldspar with porphyritic and glomeroporphyritic textures. The patterns of multi-trace-element and REE diagrams are enriched in large ion lithophile (LILE) and light rare earth elements (LREE) compared to high field strength elements. Depletion in Nb, Ti, Ta are comparable to those observed in subduction zone volcanics. Tectonomagmatic discrimination diagrams show the formation of these rocks in the active continental margin. The averaged values of geochemical parameters Ce/Pb, Th/Ce and Ba/Nb indicate the characteristics of subduction zones, interpreted to reflect enrichment by sediments and contamination with continental crustal material. The interpretation of geochemical diagrams shows that Bukan intermediate lavas were formed by partial melting of lithospheric and spinel lherzolitic mantle.

Today, alkaline rocks are a more important perspective for the largest gold deposits relative to normal calc-alkaline andesites (Müller and Groves, 1993; Sillitoe 1993, 1997, 2002). Specifically, four of the nine largest epithermal gold-silver deposits and four of the ten largest porphyry copper-gold deposits are associated with high-K calc-alkaline and shoshonitic rocks (Sillitoe, 1997, 2002). The high-K igneous rocks only comprise between 5 and 10 vol.% of volcanic arc rocks and are associated with 40% of the largest epithermal and porphyry deposits, indicating their importance for mineral exploration (Müller and Groves, 2019). The Siahouki Cu-Au deposit is located 50 km north of Bam, in the southern part of the Urumieh-Dokhtar magmatic belt of Iran. Considering the potential of shoshonitic volcanic rocks as suitable host rocks for epithermal Au-Cu deposits and also the vastness of the rocks in the area, the petrography, and geochemistry of volcanic rocks in the Siahouki Cu-Au deposit is chosen as the subject of the present research. It is hoped that the study of changes in the Cenozoic volcanism from the Siahouki area can reveal part of the geodynamic and subsequently metallogenic development in this part of Iran.

Field investigations including the preparation of a 1:5000 geological map (Figure 3) as well as collection of rock samples. were performed for this study. At this stage, over 50 specimens were taken, of which 25 samples were selected for preparation of thin sections. Using XRF and ICP-MS techniques, the abundance of major oxides, minor, and trace were determined on 22 representative samples. All the samples were then crushed in a jaw crusher in sizes smaller than 5 mm and were then sent to the laboratories. The analysis of major oxides was carried out by XRF at the Geology Department of Tarbiat Modares University and the analysis of major, minor, and trace elements was performed using ICP-MS at the laboratory of Zarazma Minerals Studies Company. Excel, Minpet, and GCDkit 6.2 software were used to process and analyze the data obtained from the geochemical analyses of the major oxides, minor, and trace elements (Table 1) and drawing diagrams as well.

Regional Geology:

The Siahouki deposit located in the Urumieh-Dokhtar Magmatic Belt of Iran (Eftekharnejad et al., 1993), is mainly covered by Eocene volcano-sedimentary rocks and Quaternary alluvium, based on the 1:100,000 Bam geological map.Ev2d unit: includes dacitic lavas, which are partly associated with rhyolitic and rarely andesitic lavas. The unit locally has undergone chlorite alteration. In the places where the argillic alteration is intense, the lavas are light gray to white, and appear cream to light brown in satellite images. The phenocrysts of the unit are mainly replaced by sericite or opaque minerals.Unit (d) consists of banded-welded tuff associated with Eocene dacitic lava and well-layered sediments including conglomerate, sandstone, and siltstone.Unit (t) is also mainly composed of dacite and partly associated with rhyolitic to andesitic lavas, tuff, and ash intercalations.The Eocene volcano-sedimentary units are surrounded by Quaternary alluvial fans (Qf1 and Qf2). These units are cut by younger faults.Alteration and MineralizationBased on field observations along with drilling core data, Cu-Au mineralization in the Siahouki area occurred as quartz and carbonate veins with stockwork and breccia textures, accompanied by silicic, carbonate, and argillic alteration types. The mineralization is exposed along NW-SE structures in the dacitic crystal tuff (Ed) and andesitic lithic tuff (Elt) units, as ore zones up to 200m length and 0.1-2m (average 1 meter) thickness. Field and microscopic studies indicate that ore mineralization is controlled by silicic, carbonate, argillic, and propylitic alteration features. Silicic and carbonate are the most important types of alteration associated with ore (sulfide)-bearing veins. The hypogene ore minerals formed with the quartz and carbonate veins including chalcopyrite, tetrahedrite, bornite, pyrite, and native gold, respectively. During supergene processes, oxidation, and decomposition of sulfide minerals gave rise to the formation of malachite, azurite, chalcocite, and iron oxide-hydroxides as well.

Based on the chemical analytical results of the host rock (Ed unit) in the Siahouki area, the composition of Ed unit plots on the dacite and rhyolite domains (i.e., 61.17 to 76.28 wt.% SiO2) (Table 1). The samples are characterized by the high Al2O3 contents (0.9 to 17.33 wt.%), very high K2O (˃ 4.26 wt.%), and a high ratio of K2O/Na2O, consistent with the chemical characteristics of typical shoshonitic rocks (Morrison, 1980). The studied samples show negative Ta anomalies, and low Nb/Ti ratios, as well as high contents of Al2O3 and P2O5 and the high LILE/HFSE ratios. Also, enrichment in Pb can be related to crustal contamination. The formation of potassic magmatism took place with the release of fluids from the subducted Neo-Tethyan crust, the metasomatism of the lithospheric mantle, and the subsequent melting of the metasomatized mantle, which is the result of an extension phase and fault systems in the region, the parent shoshonitic magma rose to the earth's surface.

The Eocene volcanic units at Siahouki are mainly composed of lavas and tuffs with an acidic to intermediate (rhyolite, dacite, and andesite) composition associated with intercalations of intermediate to basic (trachy-andesite, basaltic trachy-andesite and basaltic andesite) lavas. The chemical features of the host rocks (Ed unit) at the Siahouki deposit, which are dacite and rhyolite in composition, are comparable with typical shoshonitic rocks. Other geochemical characteristics of the volcanic-hosted Cu-Au mineralization in the Siahouki deposit (including low Nb/Ti ratios, negative Ta anomalies, and the high contents of Al2O3, P2O5, and LILE/HFSE ratios) suggest that the deposit generated in a continental volcanic arc environment and display close genetic relationship with shoshonitic composition.

Evaporitic formation of Gachsaran (Early Miocene) is known as the most important caprock of Middle East hydrocarbon reservoirs in Tertiary. This formation has good outcrops in the south of Bandar Lange embayment in the south-eastern folded Zagros, and in the east of Bandar Khamir, it includes three units: Chehl, Champeh and Mol. In this area, two sections of the 40th section of Gachasaran Formation, which includes evaporite deposits, were studied from a geochemical point of view, with an emphasis on paleoclimate and origin. For this purpose, 22 samples were taken from the vapors of both sections and subjected to XRF and ICP analysis. The results obtained from the main oxides show a negative correlation of Al2O3, K2O, Fe2O3 and a positive correlation of CaO with SO3, which indicates the prevailing conditions for are sulfate deposits and on the other hand, an increase in salinity in the basin. Investigations also show a negative correlation of secondary elements with SO3 oxide, which indicates the existence of 4 stages of drying and regression of the index in the period of settling of these evaporites. The outcrops of Hormoz series diapirs upstream and close to the studied area are proof of the impact of Hormoz series deposits on increasing the amount of secondary elements in the studied sequence.

The Shahvali granitic pluton is one of the numerous intrusive bodies in the Sanandaj-Sirjan zone. The pluton is dominated by leucogranite and small volume of granite and granodiorite. The major minerals include quartz, plagioclase, K-feldspar, biotite as well as muscovite, tourmaline, garnet and rarely sillimanite. The medium to high amount of potassium, calc-alkali series and peraluminous S-type nature of these rocks is verified by their high content of normative corundum (average=2.1), and high molar A/CNK>1.1 ratio. Low CaO amounts, CaO/Na2O ratios (0.10-0.36), negative Eu anomalies imply that the melts originated under vapour-absent conditions from a metapelitic source. Depletion in Sr, Ba, HFSE and enrichment in LILE are remarkable characteristics of the rocks under discussion. The geochemical data and petrogenesis of the Shahvali granite mass indicate similar to the impact environment granites such as the Himalayas, which were formed from the partial melting of metapellites and muscovite dehydration in the absence of fluids. Therefore, the mentioned mass was most likely formed in connection with the collision of the Afro-Arabian continental crust with Central Iran during the Laramide orogeny phase and during the Late Cretaceous-Eocene, and the presence of shear zones played a very important role in its formation and uplift. Therefore, their whole rock geochemical features are broadly consistent with partial melting of middle to upper crustal metasedimentary rocks in an active continental margin related to collision between the Afro-Arabian continental plate and the Central Iranian microplate.

The Persian Gulf is the most important aquatic ecosystem in West Asia and the Middle East region. The beach of this Gulf in Bushehr port is one of the most important recreational and commercial beaches in the country. In order to investigate the sedimentology and geochemistry of the Persian Gulf coastline deposits in the area of this port, 28 surface sediment samples were collected and grain size analysis and XRF geochemical analysis was done. The results showed that the sediments of this beach were sand with a small amount of gravel, which indicated continuous energy in this beach and the washing of mud particles. The geochemical results showed that the highest concentration of oxides were SiO2 and Cao. Investigating the source rock and tectonic position of these deposits showed the primary composition of lite arenite and greywacke and the tectonic position of the active continental margin. Hydraulic melting also indicated the immature to medium maturity composition of these sediments, which indicate semi-arid weather conditions with medium chemical maturity. In general, the similarity of the tectonic conditions and ancient climate of these deposits with the Zagros sequence indicated the existence of Zagros as the main source of these deposits.

The Cenozoic Urumieh-Dokhtar magmatic arc has characteristics similar to those of Andean-type magmatic arcs. Various types of magmatism occurred in this arc including calc-alkaline and K-rich calc-alkaline magmatism and less of them alkaline magmatism (Shahabpour, 1982). Kerman porphyry copper belt (KPCB) in the southern part of this arc includes two types of granitoids: (1) Jebal Barez-type (late Eocene–early Miocene) associated with minor Cu-mineralization, and (2) Kuh Panj-type (middle Miocene–Pliocene), which is associated with major porphyry copper deposits (Mirzababaei et al., 2016). Kuh-kapout porphyry deposit (Eocene) in the southern part of KPCB is affected by Jebal Barez type granitoids. This deposit has been studied to determine the genesis of magmatism, mineralization and tectonic setting, by the whole rock geochemistry of quartz diorite intrusions, this evaluation is based on trace and REEs geochemistry data.

Regional Geology:

This area is located in the southern part of the Urumieh–Dokhtar magmatic belt and in the Kerman porphyry copper belt. Arc-related magmatism events in this region include Paleocene to Oligocene magmatism and including andesite- dacite volcanic-sedimentary rocks with porphyry texture and quartz diorite intrusions with porphyry texture. In these rocks on the surface, there are intermediate argillic alteration events, and with increasing depth, quartz-sericite-pyrite zone and then potassic and alkali (potassium)-feldspar-sericite-chlorite-anhydrite zone are observed. Quartz diorite rocks include plagioclase and hornblende crystals (about 30 to 40 percent), biotite (10 to 15 percent), and potassium feldspar and quartz. Potassic alteration zone in depth is recognized by hydrothermal biotite, K-feldspar, magnetite and anhydrite. Mineralization in quartz diorite intrusions is more in the form of pyrite, chalcopyrite, and magnetite in association with the potassic alteration zone. Andesite-dacite volcanic-sedimentary rocks and quartz diorite rocks intruded by post-mineralized and barren micro diorite intrusion.

The samples were selected based on field observations and changes in mineralization-alteration rates from the weak alteration section of the quartz-sericite zone. For analyzing trace and rare earth elements, Samples were analyzed by the multi-acid method and used the Microwave Digest. Many of handpick and drill core samples were prepared to form thin sections for microscopic studies

Alteration and mineralization:

In this area, different types of hydrothermal alteration events including potassic, phyllic, propylitic, argillic and K-feldspar- chlorite- sericite, occurred that was influenced by fractures and faults. Quartz diorite intrusive rocks shows intense potassic and phyllic alteration zone, the main type of hydrothermal alteration zone is potassic and contains quartz ± chalcopyrite ± pyrite ± magnetite as mineralized veins and scattered event of pyrite, chalcopyrite, and magnetite. The phyllic alteration zone includes pyrite, which increases with depth. In the quartz-sericite-pyrite alteration zone, abundant chlorite and plagioclase are observed in the groundmass along with the occurrence of pyrite and anhydrite, and Cu mineralization in the form of scattered chalcopyrite.

Whole rock chemistry:

In this study, it seems that due to the presence of phases such as garnet and hornblende in the magma in the origin, a fractionation between HFSEs and LILEs has occurred (Green, 2006). Remaining of HFSEs and HREEs in the origin lead to low amounts of these elements in the resulting magma. The occurrence of negative anomalies in these elements, on the other hand, can be due to crustal contamination with mantle magmatism during their ascent to the surface. Anomaly in trace elements and ratios of REEs and trace elements, emphasizes that magmatism originated from the volcanic arc and subsequent events, according to the Th/Nb-Ba/Th diagrams and the La/Sm-Sm/Yb diagram, including the presence of lower crustal contamination and the significant role of fluid in the production of metasomatized magmatism. According to the studies on data normalized to the primary mantle, a depletion in Ba and Nb values and an enrichment in Rb and Cs have occurred.

Studying trace and rare earth elements in porphyry copper deposits is useful for determining the mineralization and fertility of magmatism, tectonomagmatism-setting, crustal contamination, and mantle metasomatism. Th-Co diagram (Hastie et al., 2007) and Th/Yb-Ta/Yb diagram (Hastie et al., 2007) indicate that most of the samples in this study area were plotted in the calc-alkaline magma region of the diagrams. Using the Sm/Yb versus La/Sm diagram (Aldanmaz et al., 2000) in the quartz diorite rocks shows a magmatism with higher Sm/Yb ratios than what is usually found for the spinel lherzolite. The plotting of the samples on diagrams indicates that the samples are located near the spinel + garnet lherzolite trend, indicating that the early magmatism originated from the spinel + garnet lherzolite mantle. High values of Ba/Th compared to low values of Th/Nb emphasize the contamination of subducting material or lower crust with magma; the (Dy/Yb)CN-Sr/Nd (Kelemen et al., 2003) diagram indicated that the process of fractional crystallization of plagioclase was effective in the evolution of magma; and finally, the study of samples in this deposit shows the relatively high water content in the magmatism, associated with the presence of garnet in the source and magma contaminated with the lower crust (Temel et al., 1998). In order to investigate the tectonic environment of the deposit, the diagrams of Pearce et al. (1984) were used. The samples are located in the active continental margin and associated with collision magmatism.

analysis of the trace and REEs of the quartz diorite rocks in the region, a magmatism related to the arc with the calc-alkaline series can be recognized. In terms of the evolution of magmatism, according to the interpretation of trace element data, from the origin to the surface, it can be considered a magmatism that originated from the partial melting of magma with the metasomatized spinel + garnet lherzolite composition in the source with the presence of garnet and amphibole phases. In terms of geochemical properties magmatism is more similar to Kuh-Panj type granitoid than the Jabal Barez type; and it is placed in the category of semi-economic to economic magmatism. Based on studies of trace elements from whole rock data, the tectonomagmatism of the rocks in the region is in the range of the active continental margin to collision setting.

Zircon is a significant mineral due to its ubiquitous occurrence, chemically resistant and refractory, that can survive both weathering and transport processes as well as high-temperature metamorphism and anatexis (Ballard et al., 2002). It can, therefore, be found in many igneous, metamorphic, and sedimentary rocks and is particularly common in plutonic rocks. Zircon acts as a valuable archive of geochemical information regarding geochronology studies (Hoskin and Schaltegger, 2003), a record of the parent rock oxygen isotopic ratio (Hawkesworth and Kemp, 2006), provide a proxy for processes such as crustal recycling by Hf isotopic composition (Scherer et al., 2007), reflect the oxidation state of parent magma by Ce and Eu anomalies (Trail et al., 2012), and temperature estimation by Ti content (Hofmann et al., 2014).The Sangan mining district, the largest skarn iron ore district in Iran, is located in the northeastern part of the Alborz Magmatic Arc. Fourteen skarn anomalies occur along the contact of the syenite to the syenogranite Sarnowsar pluton in the north and the Sarkhar and the Bermani plutons in the southeast (Mehrabi et al., 2021).Previous works have used the zircon U–Pb geochronology, whole rock geochemistry, and zircon chemistry to constrain the emplacement age, fertility of magmatism, and petrogenesis of these granites (Malekzadeh Shafaroudi et al., 2013; Golmohammadi et al., 2015; Mazhari et al., 2017; Mehrabi et al., 2021; Ghasemi Siani et al., 2022), but neglected the importance of zircon trace element concentrations when interpreting the parental magma evolution. Here, we examine the trace elements of zircons from Sarnowsar and Sarkhar-Bermani intrusions, to verify the origin of these zircons and the evolution of the parent magma.

Regional Geology:

The oldest rocks in the Sangan mining district include weakly metamorphosed Precambrian slates and metasiltstones. The Lower Jurassic Shemshak Formation consists of chert, weakly metamorphosed and metasomatized shale, siltstone, and red sandstone. The Middle Jurassic rocks are characterized by limestones and marls of the Dalichay Formation. The overlying Upper Jurassic Lar Formation composed of limestone, dolostone, and dolomitic limestone. Cretaceous formations are dominated by massive limestone, conglomerate, and intercalated crystal tuff. These metasedimentary formations are uncomfortably covered by the intermediate to felsic volcanic rocks crosscutting by plutonic rocks. Intermediate to felsic volcanic rocks cover an area of 10 km2 in the southwestern part of the Sangan mining district and extended within central ore bodies. Volcanic rocks include dacite, andesite, rhyolite, latite, and their pyroclastic equivalents.

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 a laser ablation system, ICP-MS instrument (Agilent 7700a ICP-MS instrument). 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.

Analytical data of zircon trace element concentrate are presented in the supplementary Table. Results are plotted against the 206Pb/238U date for each zircon grain. Zircons from the intrusions have scattered geochemical signatures that show no correlation with U–Pb dates. Conversely, some geochemical parameters of zircons from the intrusive rocks show distinct temporal trends. For example, zircon Yb/Dy and Ce/Nd values broadly increase with age younging. It should be noted that the Th/U and Ce/Nd of the Sarnowsar zircons are higher than those of Sarkhar and Bermani intrusions.

Correlations between rock type and the trace element compositions of zircon from a wide range of igneous rocks can be illustrated with a series of discriminant plots. For example, plots of Nb vs. Ta, Y versus Yb/Sm, and Y vs. Ce/Ce* and similar plots (Belousova et al., 2002) indicate that the studied zircons are classified as granitoid igneous type as a parental magma. The uniformly high Hf contents of zircons in this study point to their crystallization derived from a more evolved felsic magma, particularly Sarkhar and Bermani intrusions. The accompanying low Eu/Eu* ratios are indicative of plagioclase crystallization. The U/Yb ratio of zircons can be used to distinguish their origin (Grimes et al., 2015). Continental-arc zircons have U/Yb ratios mostly between 0.1 and 4, and low U/Yb ratios (<0.1) are characteristic of zircons derived from a mantle source. In the discrimination diagrams of U/Yb vs. Hf and U vs. Yb, all the obtained data are plotted in the continental-series area and are distinguishable from ocean crust zircons. In the U/Yb versus Nb/Yb diagram, both the whole-rock and zircon compositions show the characteristics of a magmatic-arc array. Overall, a continental-crust source for the zircons, mirroring the origin of the parent magma. The disparate geochemical behaviors of Hf, Th, and Nb within zircon provide a potential method for establishing the tectonic setting of host magma. The Nb content of arc magmas is depleted relative to magmas formed in within-plate settings (Pearce and Peat 1995), and as such, arc zircons possess lower Nb/Hf and higher Th/Nb ratios at a comparable degree of magmatic fractionation. Accordingly, bivariate discrimination diagrams of Th/U vs. Nb/Hf and Th/Nb vs. Hf/Th are meaningful tools for distinguishing within-plate (anorogenic) from arc-related (orogenic) settings (Hawkesworth and Kemp, 2006). The majority of zircons are plotted in the orogenic field, signifying a magmatic-arc or orogenic setting and a calc-alkaline parent magma.

Based on the trace-element composition of zircon grains, whole-rock trace-element contents, and patterns of two granitoid intrusions in the Sangan mining district, the following conclusions can be drawn:- The disparate geochemical behaviors of U, Hf, Th, and Nb indicate a continental-crust source in a magmatic-arc tectonic setting. All of the studied zircons are located in the granitoid igneous rocks fields with a series of discriminant plots.The studied zircon grains of the Sarnowsar show relatively high Ce4+/Ce3+ ratios, pointing to their formation in an oxidized magmatic medium.

The Tazekand mineral prospect, as a part of Tarom-Hashtjin metallogenic belt, is located ~45 km northeast of Zanjan City, NW Iran. Based on field, petrographic and geochemistry investigations, the lithological composition of the intrusive rocks in the area varies from monzonite, diorite, granodiorite to gabbro and the volcanic units range of trachy andesite, andesite to basaltic andesite. These rocks with per-aluminous to meta-aluminous nature, are related to High-K calc-alkaline to shoshonitic magmatic series, and belong to I-type granites. Based on the diagrams illustrating the tectonic setting, these rocks formed in a post-collision volcanic arc environment on an active continental margin. In the Harker diagrams, SiO2 has negative correlation with Al2O3, MgO, MnO, CaO, Fe2O3, P2O5, TiO2, Co, V, Sr, Ni and Cr and positive correlation with K2O, Na2O, Zr and Rb. Enrichment of LILE (Cs, Ba, Rb, Th, U and Pb) and LREE and depletion of elements with high field strength (Ti, Y, Zr, Nb and Dy) and HREE are other geochemical features in the Tazekand intrusive rocks. On the basis of geochemical data, both mantle and crust components have been effective in the formation of magma for the studied intrusive rocks. The magma producing of these rocks is formed by the mixing of basaltic melts derived from the mantle and the melt resulting from the partial melting of the lower crust in balance with pyroxene and amphibole residues at a depth of less than 40 km.

The study area is located in the central part of Urumieh-Dokhtar Magmatic Arc and south of Mamouniyeh, Iran. Oligocene-Miocene intrusive rocks have combined domain of gabbro, diorite and monzonite with calc-alkaline nature which have characteristic features of continental margin subduction zones. Extensive siliceous, propylitic-chlorite, sericitic, argillic, carbonate and tourmalinization alteration be seen which mineralization has occurred mainly in siliceous zones in the sulfide-oxide veins form. Chalcopyrite, pyrite, bornite, magnetite, Specularite and Ti-oxides are main minerals of the hypogene stage and chalcocite, covellite, azurite, malachite, chrysocolla, tenorite, hematite, goethite and limonite related to supergene-oxidation stage. The study of 138 fluid inclusions in ore-bearing silica veins shows homogenization temperature from 80-345°C, salinity 0.88 to 11.40 wt% NaCl and formation depth between roughly 1 km and 500 m compared to the water table and the hydrostatic pressure is 10 MPa. Evidences such as fluid inclusions with different liquid-vapor ratios, accompanying vapor-rich fluid inclusions, quartzes with comb-cokade texture, fine-grained muscovite and illite indicate gentle boiling of fluids which together with other evidences such as the and partial mixing of fluids and the instability of sulphide complexes have caused the deposition of copper minerals related to the low sulphidation epithermal mineralization system in the Mamouniyeh.

Porphyry deposits are very important as they contain very large reserves of copper and valuable secondary elements such as molybdenum and gold. Copper-molybdenum or quartz monzonite porphyry deposits are usually structurally related to the magma arc associated with the upper parts of the subduction zone of the continental margin, and copper-gold or porphyry diorite deposits usually form in association with the subduction zone of the island arc (Sillitoe, 2010; Park et al., 2021).
Kahang Cu-Mo deposit is located in the middle section of the Urumieyh-Dokhtra magmatic arc. In 2001, Kahang was identified by processing satellite imagery data and mapping hydrothermal alteration by Rio Tinto Mining and Exploration Limited company. Then, a detailed exploration was carried out by Dorsa mining company from 2002 to 2007 and about 40 million tons of copper ore with a grade of 0.6 percent was established (Asadi, 2007). Since 2008, extensive deep drilling has been performed by the National Iranian Copper Company to increase the proved reserve. The main focus of the previous researchers at the Kahang deposit was mostly based on conceptual studies on magmatic character and hydrothermal alterations (Ayati et al., 2008; Harati, 2011; Azadi et al., 2014; Komeili, et al., 2017; Aliyari et al., 2020). In the present research, ASTER satellite imagery data, geological maps, as well as geochemical and magnetic data were processed and used to identify optimum exploration criteria at the Kahang porphyry Cu-Mo deposit and other similar deposits.

Near-surface mineralization at Kahang deposit is related to altered and brecciated quartz monzonite dykes, and deeper than 200 m is associated with altered quartz monzonite porphyry intrusions showing calk alkaline characteristics. The extensive hydrothermal alteration, from the center to the margin of the Kahang deposit, are phyllic, argillic, and propylitic alterations. Mineralization is mostly related to strong phyllic and potassic alterations.

Detailed geological maps of Kahang area were used to identify geological exploration criteria. Aster satellite imagery data of the area was used to identify hydrothermal alterations. ICP analytical results of elements such as Cu, Mo, Zn, and Pb were used to create uni-element and additive index multi-element geochemical anomaly maps to identify geochemical exploration characteristics. In total 16 rock samples were collected for petrographic studies and XRF analysis. A number of 568 magnetic measurements were used to create magnetic anomalies associated with favorable subsurface hydrothermal alterations possibly associated with Cu-Mo mineralization.

ICP analytical results of the soil samples were used to identify geochemical exploration criteria at Kahang deposit. Basic statical studies were applied to these data to identify the variation of Cu, Mo, Pb, and Zn concentrations in the soil samples that could be associated with subsurface mineralization. Mult-elements additive index geochemical maps of the analytical results of the soil samples showed a Cu-Mo enrichment zone in the central part of the hydrothermal alteration and a Pb-Zn depletion zone in the margin. Based on these additive index maps three porphyry centers were identified at the Kahang deposit for further exploration.

By processing ground magnetic data of the eastern porphyry center at Kahang deposit, residual total magnetic intensity and upward continuation magnetic maps were created to identify magnetic signatures possibly associated with mineralized hydrothermal alterations. These maps showed an ellipsoid-shaped low magnetic anomaly in the eastern porphyry center associated with phyllic alteration hosting Cu-Mo mineralization. These low magnetic anomalies can be used to identify zones of subsurface mineralization at Kahang deposit.

In this research, remote sensing, geological, geochemical, and geophysical studies showed three porphyry centers at Kahang deposit. The world-class economic mineralization only occurred in the eastern porphyry center due to the presence of extensively strongly altered and brecciated quartz monzonite porphyry units showing low magnetic signatures and high Cu-Mo additive index anomalies. By comparing the low magnetic anomalies, high Cu-Mo anomalies, alteration zonation, brecciated rock units, and favorable structures, successful drilling targets can be identified to test subsurface mineralization at Kahang deposit. The integration of this information along with the geochemical and primary drilling information were used to plan systematic drilling. Most of the holes drilled in this zone at depths greater than 150 meters encountered economic mineralization of copper (approximately 0.5%) and molybdenum (approximately 700 ppm). The magmatic arc of Urmia-Dokhtar is considered the most important copper (molybdenum, gold) porphyry province in Iran. Most of the known large porphyry deposits of Iran, such as Sarcheshmeh and Meidok, are located in the southeast of this magmatic arc, and Songun is located in its northwest. In the central part of the Urmia Dokhtar magmatic arc, which is located in Isfahan and Central provinces, no similar deposit was reported prior to the discovery of Kahang deposit. Therefore, these studies have shown that the middle part of this arc may have the potential for many hidden porphyry mineralizations like Kahang deposit. Therefore, the exploration criteria identified in this study can be used for the exploration of similar deposits in this area at various stages of exploration, from identification to detailed exploration.