قاسم نباتیان

The Qanli laterite-bauxite horizon is located in the Central Iranian Zone, at a distance of 80 km from Zanjan city. The studied units at this area include sequences of the Ruteh and the Shemshak Formations. Based on sedimentary facies analysis and study of skeletal and non-skeletal allochems, it can be concluded that the sedimentary environment of this formation is a ramp-type carbonate platform. According to the fieldwork studies, the Qanli laterite-bauxite horizon is stratiform and and located at the final section of the Ruteh and below the Shamshak Formation. Mineralogical studies show that the laterite-bauxite horizon consists of hematite, goethite, boehmite and kaolinite with a few amounts of lipdocrosite, rutile, chlorite and ilmenite. Microgranular, pletiomorphic, flow-colloform, pisoidic, ooidic, peloidic and extraclast are the most important textures in these strata. Different chemical diagrams show that the laterite-bauxite horizon of Qanli deposit is located in the range of bauxite, bauxite clay and laterite. According to the mineralogical studies, it seems that the formation of laterite-bauxite horizon of Qanli occurred at pH between 3.5 to 6 and Eh about 0.4 to 0.7 and it has undergone moderate degrees of lateritization process. Current research indicate that the laterite-bauxite horizon of Qanli is the most similar to the karst bauxite deposits. Due to the expansion of Permian and Jurassic units in this area and nearby areas, the study and investigation of the Qanli laterite-bauxite horizon can be considered as an exploration key for similar areas in the Central Iranian zone.

The Qazikandi iron ore mineralization is located in the 70 km northwest of Zanjan and belongs to the Central Iran Zone. The rock units in the study area include Precambrian to Cenozoic formations as well as Cretaceous granite bodies. Iron mineralization in the Qazikandi area has occurred in the form of lensoid and vein in the basal part of the Barout Formation with carbonate and shale composition. The main ore minerals consist of magnetite, primary hematite, pyrite, secondary hematite and goethite. The secondary minerals which formed through supergene process and evolved during weathering of magnetite and pyrite are secondary hematite, goethite and lepidocrocite. The alteration in the study mineralization includes chloritization, epidotization, silicic, sericitization and argillic. The current research suggests that the intrusion of plutonic body with granite to quartz-monzonite composition into the Barout Formation has led to the formation of iron mineralization in the area. Due to the intrusion of the plutonic body into the shale parts of the Barout Formation, the hornfels developed and anhydrous minerals such as phlogopite were formed. Following the mineralization in this area, magnetite and then small amounts of primary hematite were formed. The mentioned alteration products developed simultaneously with this stage of mineralization. It is noteworthy that the silicic veins and veinlets which formed after mineralization, have cut the primary phases of mineralization. The field and microscopic evidence suggest that the Qazikandi ore deposit is classified as the magnesian skarn iron ore deposit.

Ghezeljeh deposit is located in the Central Iranian zone, in the Zanjan province and northeast of the Mahneshan city. The rock units in this area belongs to the Oligo-Miocene, which contain Lower Red, Qom and Upper Red formations. The Upper Red Formation in Ghezeljeh region has about 750 m thickness and mainly consists of brown to green marl intercalations with sandstones. In this area, the alternation of marl and sandstone sequences contain sandstone layers with thickness about 2 to 8 meters, which in two horizons, the copper-lead and zinc mineralization has occurred. Copper mineralization, in addition to being observed inside the sandstone unit. In the Ghezeljeh deposit, the host rocks of the copper ores, are gray sandstones and conglomerates which are intercalated with red and gray marl units. According to field and microscopic studies, the main ore mineral consist of pyrite, chalcocite, chalcopyrite, bornite, galena and sphalerite which associated with the secondary minerals such as serosite, malachite, azurite, covellite, smithzonite and goethite. The ore mineral textures consist of disseminate, framboidal pyrite, solution seams, interparticle cement, replacement and relict. Preliminary fieldwork studies in the Ghezeljeh region also show that organic matter including plant remains and diagenetic pyrite are the effective factors to concentrate and mineralization. It is considerable that the grade of lead, zinc and copper, in Ghezeljeh deposit are 6%, 3% and 1%, respectively. Generally, host rock, tectonic setting, sedimentary environment, mineralogy, texture, mineralization control factors all confirm that the studied mineralization has more similarities with Redbed type copper deposits.

At the northeastern end of the Sabzevar ophiolitic zone and the southern edge of the Binalud zone and south of Quchan, a 200 km long young magmatic arc consisting mostly of calc-alkaline to adakitic volcanic-intrusive rocks are exposed which extended to Esfarayen. In the present study, the Shotorsang hypabyssal granitoids in the northeast of Sabzevar and the Binalud structural zone are investigated. No dating data and comprehensive geochemical study of these units have been published, and the origin of hypabyssal units is unclear. Accordingly, new petrographic and geochemical data and U–Pb zircon ages of intermediate-acidic intrusives of Shotorsang in the northeast of Iran are reported.

Geology:

The hypabyssal Shotorsang granitoids, as a part of the magmatic arc in the north of the Sabzevar ophiolitic belt, are located 82 km northeast of Sabzevar and in the Binalud structural zone. Based on the field studies and 1:5000 geological map, the rock units of the Shotorsang area include early Cretaceous limestone, Eocene sedimentary and volcanic rocks, the Miocene hypabyssal stocks and dykes, and new Plio-Quaternary deposits. Intrusive units including dikes and hypabyssal stocks composed of dacite, granodiorite, and quartz monzonite. The dikes with acidic composition crosscut the Eocene sedimentary and volcanic succession.

During the field investigations in the Shotorsang area, 80 samples were taken from most of the geological units, and 40 thin sections were studied by a polarizing microscope for petrographic studies. Six representative and least altered samples from the Shotorsang hypabyssal granitoids were analyzed for major oxides and trace elements using XRF and ICP-MS in the Acme Laboratories (Canada). Two samples from dacite dike and granodiorite stock (samples Ab8 and Ab59) were selected for dating studies according to the suitable size and abundance of zircon crystals.U-Pb dating was conducted by laser ablation-multiple collector-inductively coupled plasma-mass spectrometry (LA-MC-ICP-MS) in the Laboratory of Isotope Geology at the Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing, China.

Petrography:

Based on petrographic studies, the Shotorsang hypabyssal units can be divided into three groups including granodiorite and quartz monzonite stocks as well as dacite dikes. The granodiorite is composed mainly of quartz, plagioclase, orthoclase, hornblende, and biotite with accessory zircon, sphene, and apatite. This unit dominantly displays a porphyritic to glomeroporphyric texture.Dacite dikes have mineralogical and textural similarities with those of the granite stocks. Mineralogically, these units include quartz, plagioclase, orthoclase, biotite, and hornblende with a felsitic porphyry texture.Magmatic fluids released during the intrusion of quartz monzonite bodies are the main factor for skarnization in the area.

Geochemistry:

On the total alkali-silica diagram (Middlemost, 1985), the intrusive bodies and dikes are plotted in the fields of quartz monzonite, granodiorite, and granite, which is consistent with their petrographic observations. On the SiO2 versus K2O discrimination diagram (Peccerillo and Taylor, 1976), the Shotorsang hypabyssal granitoids fall mainly in the medium- to high-K calc-alkaline domains. On chondrite and primitive mantle-normalized diagrams, the investigated samples display enrichment in LILE and LREE and depletion in HFSE and HREE.On Rb versus Nb+Y tectonomagmatic discrimination diagram (Pearce et al., 1984), the Shotorsang hypabyssal granitoids are plotted in volcanic arc granite field.U-Pb datingThe two samples from the dacitic dike and granodioritic stock yielded zircon U-Pb ages of 22.52±0.38 and 22.56±0.35 Ma, respectively. The Th/U ratio for zircons from the dacitic dike and granodioritic stock is more than 0.1, which is different from metamorphic zircons and compatible with magmatic zircons.

The remarkable geochemical criteria of hypabyssal Shotorsang granitoids are Sr (382.5-607 ppm), high Sr/Y ratios (26.4-62.5), LaN/YbN (9.5-17.1). The low values of Y (9.7-16.3) and HREE are similar to those of adakites. The low values of Yb and Y, and high ratios of Sr/Y, as well as La/Yb, could be attributed to the presence of residual garnet and hornblende or as fractionated minerals.The LILE (large-ion lithophile elements) enrichment and HFSE (high-field strength elements) depletion are typical features of calc-alkaline magmas related to subduction zones, which originated from partial melting of a subducted oceanic slab or a supra-subduction mantle wedge.The lack of Eu anomaly in adakites, as well as the Shotorsang hypabyssal granitoids with abundant plagioclases, is related to magma ƒO2. Under oxidizing conditions, Eu occurs dominantly as Eu3+, leaving lesser Eu2+ to be incorporated into plagioclase.There are evident changes in Sr-Nd isotopic ratios of the magmatic rocks of the northern Sabzevar ophiolitic belt, and it seems that the (87Sr/86Sr)i ratios increase, however, the εNdi values decrease from the old to the young rocks, which likely indicates the effect of the crustal materials on the source magma.It can be inferred that the Cretaceous-Paleocene magmatism is subduction-related, and from Eocene onwards, the igneous rocks of this zone, including the Miocene Shotorsang adakites with an age of 22.5 million years, have a post-collisional nature.

The Shotorsang hypabyssal granitoids, as a part of the magmatic arc of the northern Sabzevar ophiolitic belt, formed as dike and stock with dominantly porphyritic textures and intruded the Cretaceous-Eocene volcano-sedimentary succession. The two samples from the dacitic dike and granodioritic stock yielded zircon U-Pb ages of 22.52±0.38 Ma and 22.56±0.35 Ma, respectively, indicating the importance of Miocene time in iron mineralization in this zone. The geochemical features of the Shotorsang hypabyssal granitoids correspond to the field of post-collisional volcanic arc rocks (VAG) and possess similarities with those of the adakitic rocks, originating from the subducting slab.These rocks probably have an eclogite or amphibolite garnet origin resulting from the metamorphism of the Sabzevar Neotethyan oceanic lithosphere, which was subducted under the Alborz zone.

Dohneh area is located in the northeast of Zanjan and in the Western Alborz-Azarbayjan zone along the Tarom subzone. The outcropped rock units in the Dohneh area include Eocene volcanic and volcano-sedimentary rocks (equivalent to the Karaj Formation) which consist of tuff units including lithic crystal tuff and crystal lithic tuff as well as basaltic lava flows (amygdaloidal basalt and porphyritic basalt). Rock forming minerals in the Dohneh basalts include plagioclase, pyroxene and olivine. The secondary minerals in the basalts are chlorite, zeolite, carbonate (calcite), epidote, serpentine and iron oxides. The opaque minerals and apatite are present as minor minerals. The data resulted from electron microprobe suggest that the pyroxene composition in the Dohneh basalts are as Ca-Mg-Fe bearing pyroxene (low Na) and mostly show diopside, augite and minor clinoenstatite compositions. The feldspar composition is labradorite and sanidine. Based on microprobe analyses on chlorites, their composition is Mg rich which are grouped as diabantite and pininite. Moreover, the clinochlore is also detected in this area by XRD analysis. The results obtained from the electron microprobe analysis on zeolites show that zeolites of Dohneh area are low-content to medium-content silica. Na bearing zeolite namely natrolite is also recognized by XRD analysis. The chemical composition of pyroxene from the Dohneh area suggests that these minerals crystallized in pressure lower than 5 Kbar from alkaline to sub-alkaline magmas in the back-arc and subduction related setting.

The Maher abad and Khopik porphyry Cu deposits occurred in the Upper Eocene (39-37 Ma) in Lut block. All of them associated with intermediate (mostly monzonite) rocks. Porphyry deposits are closely associated with oxidized magmas. Oxygen fugacity (fO2) is a key factor that controls the formation of porphyry Cu deposits. The composition of the major and trace elements of zircon grains related to several ore-bearing monzonite were measured in Maher abad and Khopik porphyry copper indices. Zircon grains show moderate to low Ce4+/Ce3+ with a range of 19 to 610 and an average of 155. The average of oxygen fugacity (logfO2) values of Meher abad and Khopik ore-bearing magmas, range ∆FMQ -3.2 to MFMQ -1.3 with mean ∆FMQ -2.2, indicate formation under moderate oxidation conditions (between Ni-NiO (NNO) and Faylite magnetite-quartz (FMQ) buffers, but magnetite-hematite (HM) buffer, which ), which is not ideal for the formation of porphyry deposits. This is supported by whole-rock and Sr-isotopic data, and absence of high oxidation minerals such as hematite, and the poor adakitic charactristic of rocks in both deposits, which are due to factors involved in magma origin such as rock type and partial melting rate (possibly peridotite with low participation of slab).

Rock units in the Madabad celestite deposit are composed of medium to thick-bedded and massive limestone interlayered with marly limestone and marl units of the Qom Formation (lower Miocene). Mineralization occurs as lens-shaped orebody, hosted by limestone units of member of the Qom Formation usually crosscutting bedding of the host rocks. Three stages of mineralization occurred in the Madabad deposit. The first stage is characterized by calcite formation during syn-depositional to syn-diagenesis processes. The second stage is related to hydrothermal processes that are distinguished by formation of fine-grained and sugary crystals of massive stage-1 celestite, vein-veinlets of coarse-grained stage-2 celestite along with minor strontianite and barite, coarse-grained euhedral crystals of stage-3 celestite with vug infilling texture, and finally late-stage quartz and calcite vein-veinlets. Stage three includes supergene processes. Hydrothermal alteration includes dolomitization, calcitization and silicification. Celestite along with minor strontianite and barite are ore minerals, and calcite, dolomite, quartz and iron oxides-hydroxides are gangue minerals at Madabad. The ore minerals show vein-veinlets, vug infilling, brecciated and cataclastic textures. Microthermometric measurements of two-phase liquid-rich fluid inclusions hosted in celestite II indicate that salinities values range from 6 to 18 wt.% NaCl equiv. (avg. 10.6 wt.% NaCl equiv.). These inclusions have homogenization temperatures range from 248 to 365 °C, with an average of 278 °C. These data indicate a minimum trapping depth of 510 m for the Madabad deposit. Sr was originated from evaporate units within the marly parts of the Qom Formation and volcanic units of the Karaj Formation. Characteristics of the Madabad deposit are similar to epigenetic replacement celestite deposits.

Around The Karik village, east of Meiduk mine, Eocene volcanic rocks (andesitic basalt, andesite, dacite and rhyolite) and pyroclastic rocks (agglomerate and tuff) are exposed. These rocks are cut by several andesitic dikes. The major textures in the volcanic rocks are porphyritic and flow textures. The minerals such as plagioclase, alkali feldspar, quartz, pyroxene, amphibole, biotite and opaque are present as phenocrysts and fine grains. Sometimes, feldspar crystals (mainly plagioclase) are found as oriented microlites. In some cases, within the plagioclase phynocrysts disequilibrium textures such as sieve texture, corrosion and zoning are observed. Quartz crystals are corroded. Amphibole and biotite crystals are changed into Fe-Ti oxides on their rims. These textures are probably attributed to magma mixing, water vapor changes and decompression due to rapid ascent of magma. The Karik volcanic rocks are calc-alkaline and mainly metaluminous in nature. Primary mantle and chondrite normalized multielement diagrams for the study rocks are spiked and they have several peaks and troughs. In the diagrams, the depletion of the high field strength elements such as Nb, Ta, Ti and P is obvious which is characteristic of the subduction magmatism. The sharp positive anomaly of Pb might be attributed to crustal contamination. The chondrite normalized RRE pattern of the study rocks is relatively smooth with enrichment of LREEs relative to HREEs that is due to the high abundance of LREEs in the source or crustal contamination. According to the petrological and geochemical evidence, the Karik volcanic rocks are formed in an active continental margin setting due to the subduction of Neothetys oceanic lithosphere beneath the Central Iran micro–continent.

Oxygen fugacity (fO2) and zircon crystallization temperatures (Ti-in-zircon) of ore-bearing quartz monzonite intrusive rocks of ChahShaljami and Dehsalam Cu-Mo porphyry deposits were measured by using calculations of zircon trace element values and oxidation conditions of parental magma were investigated. The Ce4+/Ce3+ values for ChahShaljami and Dehsalam are in a range of 8 to 295 with an average of 125 and 3 to 171 with an average of 35, respectively, therefore they were not in the favorable range for porphyry mineralization. The estimated fO2 values for ChahShaljami and Dehsalam are in the range of ∆FMQ -1.8 to MFMQ +0.6 with an average of ∆FMQ -0.6 and ∆FMQ -1.3 to ∆FMQ -0.4 with an average of ∆FMQ -0.8 which is at least ∆FMQ +1 less than the values of porphyry copper mineralization in the world.. Based on the zircon log fO2 values of ore-bearing intrusive rock, the parental magma originated from partial melting of supra-subduction mantle peridotite zone within oceanic slab. Melting under unfavorable conditions (under magnetite-hematite (HM) buffer and in faylite-magnetite-quartz (FMQ) buffer condition, and lack of sufficient Cu and sulfur at the source), which is supported by evidences in deposit such as lack of magnetite-hematite intergrowths, was not ideal for porphyry Cu porphyry mineralization in the two regions. The results are supported also by previous whole-rock major and trace element geochemistry and Sr-Nd isotopic values.

North Chargar Cu-Au mineralization located within the Tarom-Hashtjin sub-zone. This area composed of andesite and quartz-andesite lavas alternated with tuffaceouce rocks. The volcanic rocks have calc-alkaline nature and were formed in an active continental margin. Mineralization present as ore-bearing quartz vein-veinlets within a silicified zone. Based on mineralogical studies, chalcopyrite and pyrite are the main ore minerals, and malachite, covellite, chalcocite and goethite were formed by supergene processes. Quartz, barite and chlorite present as gangue minerals. Hydrothermal alterations include silicification, chloritization, sericitization and argillic. Ore and gangue minerals show disseminated, vein-veinlet, brecciated, cockade, comb, replacement, relict and open space filling textures. Based on field and microscopic studies, Cu-Au mineralization in the north Chargar can be divided into four stages: 1- the first stage is silicification of volcano-sedimentary host rock along with disseminated pyrite mineralization, 2- the second stage present as chalcopyrite and pyrite-bearing quartz vein-veinlets and hydrothermal breccia cement, 3- the third stage includes barite vein-veinlets crosscutting the previous stages of mineralization, 4- the last stage is related to supergene processes. Geological features, mineralogy and ore structure-textures in the north Chargar Cu-Au occurrence indicate most similarity with base metal epithermal (intermediate sulfidation) deposit type.

Increasing demand for ore minerals needed for economic development and the desire to find a suitable rank in the international community has forced developing countries such as Iran employ more mining activities which has led to creation of a large amount of waste minerals. Given the existing equipment establishing the necessary situation and economic solutions for the exploitation of valuable elements from these waste minerals can be considered as a source for economic development of the country. The Angouran Zn-Pb mine is located west of the Zanjan province and northwest of the magmatic- metamorphic Sanandaj-Sirjan zone. The wurtzite mineral can be used as an indicator mineral for trace elements such as IGG (indium, gallium, germanium) in this mine. The economic concentration of metal elements in the Angouran mine can be divided into two parts of sulfide and gangue carbonate. The sulfide part of this mine is enriched with silver, cadmium and selenium (higher than their cut-off grade) and the gangue carbonate part is enriched in arsenic element. The foot-wall schists show some concentration of elements which are related to sulfide mineralization.

More than 30 rock samples were collected from cross sections in the open-pit part of the Angouran mine which covers all different parts such as foot-wall schist, sulfide mineralization, carbonate mineralization and hanging-wall carbonate (marble). About 30 samples were prepared for petrographic studies and geochemistry analysis which were analyzed at the Zarazma laboratory (Tehran, Iran). The ArcGIS, Geosoft Oasis Montaj and Excel software packages were also used for interpretation of data.

Geology of the study area:

The Angouran Zn-Pb mine is located west of the Zanjan province and northwest of the magmatic- metamorphic Sanandaj- Sirjan zone. The rock units in the study area include foot-wall quartz schist and hanging-wall marble with Precambrian age, Mesozoic diorite and granite, Cenozoic pyroclastic units such as white tuffs and Quaternary travertine sediments. It should be mentioned that the white tuffs and, in some cases older units are crosscut by younger diabetic sills and dikes (Ghorbani, 2008; Pirkharrati and Farhadi, 2014; Fallah et al., 2019).

The Angouran deposit has been formed as breccia structure on the boundary between thrusted hanging-wall marble and foot-wall quartz schist. According to this study, mineralization in the Angouran deposit has occurred during two hypogene and supergene stages. Hypogene mineralization in the Angouran deposit has been formed as successive phases of sulfide and carbonate. The hypogene mineralization continued by the formation of supergene mineralization. According to the geochemical analysis, a high concentration of trace elements such as silver, cadmium and selenium was detected in the Angouran deposit. These elements are concentrated in the sulfide ore mainly in the sphalerite mineral with poor lead minerals. The carbonate part of the Angouran mine which is considered to be waste contains enrichment of arsenic. The foot-wall schists are not enriched with trace elements and just concentrate in some elements such as iron, antimony, cadmium, cobalt and selenium, which are related to sulfide mineralization.

Based on the geochemistry analysis and microscopic studies, the economic concentration of metal elements in the Angouran mine can be divided into two parts of sulfide and carbonate. The sulfide part of this mine has been enriched with silver, cadmium and selenium (higher than their cut-off grade) and the carbonate part has been enriched with arsenic. This element can be considered to be a major threat to human health, along with its numerous uses, such as pesticides, medicine, electronics, etc.The wide distribution of arsenic in the open pit mine along with the other toxic elements such as cadmium and selenium (mainly related to the sulfide mineralization and host quartz schist) are too dangerous for the villagers who live near the mine due to the seepage of these toxic elements to underground water aquifers and their surrounding environment. It should be mentioned that, in the Angouran mine, the waste minerals are abandoned as deserted mountains irrespective of their relationship to groundwater and the surrounding environment.It is hoped that with the continuation of the exploitation process in the Angouran mine, the waste minerals are classified according to their type and element enrichment in a suitable manner by environmental standards. This could help prevent seepage of toxic elements (As, Cd, Se) to groundwater. Furthermore, the economic elements such as Ag, Cd, Se can be used as byproducts and be sold as raw material for other uses or extracted by using the necessary equipment. This is due to the fact that what is considered to be waste minerals for a mine, can be considered as useful material for another mine, either now or in the future.

The studied chromite mineralization in the Gharanaz-Alamkandi area is located in the west of Zanjan province and Sanandaj-Sirjan zone. The outcrops rock units consist of amphibolite, granitic gneiss, marble, amphibol schist, garnet mica schist and also ultrabasic sequences. Chromite mineralization occurred as lenzoid, veinlets and disseminated within the peridotite rocks such as serpentinized dunite, serpentinized harzburgite and serpentinit. Olivine, orthopyroxene, clinopyroxene, serpentine, asbestos, chromite and magnetite are the main minerals at these rock units. Mineral chemistry of olivines indicate that the olivines in the peridotites are rich in magnesium and show forsterite composition. Clinopyroxene in the peridotites of the study area are iron- magnesium-calcium rich with mainly are augite in composition. Orthopyroxene minerlas show mainly brunzite composition with minor amounts of hypersthene composition. The mineral chemistry of chromspinels indicate that the chromite mineralization in the study area is podiform type which enriched in Cr and Mg and depleted in Ti. In addition, the mineral chemistry studies in this area show that the host rocks of chromite mineralization and dunite- lherzolite sufferd at least 20% and 40% partial melting, rspectively. On the other hands, it can be state that both of partial melting and depleted mantle melthad important role in the formation of peridotite in the study area. According to this study, it can be note that the chromite mineralization in the study area is ophiolite type mineralization and formed from a boninitic magma in the supra subduction zone during the subduxtion of Proto-Tethys ocean beneath the Iranian block Precambrian-Cambrian time.

Qoyjeh Yeylaq volcanic rocks is located approximately in the 120 km southwest of Zanjan, within the Central Iranian zone. The rock units in this area belong to the Cenozoic which consist of mainly Oligo-Miocene volcanic (basaltic- andesitic lavas) and sedimentary rocks. Based on geochemical classification, the mentioned volcanic rocks are basalt, basaltic andesite and andesite in composition, and have calc- alkaline to high-K calc-alkaline affinity. In the primitive mantle normalized spider diagrams, all of the volcanic rocks show similar patterns with enrichment in LILE (Ba, Th, K, Pb) and negative anomalies of HFSE (Nb, Ti). These rocks show LREE enrichment relative to HREE and high ratio of LREE/HREE. Based on tectonomagmatic discrimination diagrams these volcanic rocks were formed in a continental arc setting. Based on geochemical data, it seems that volcanic rocks of the Qoyjeh Yeylaq area were formed from 5-20 % partial melting of a garnet- spinel lherzolite enriched mantle by subduction of Neo-Tethys under the central Iran, within the Orumieh- Dokhtar magmatic arc.

Malek Ghasemi and Karimzadeh Somarin (2005) reported that Chromite deposits in Iran occur in Paleozoic and Mesozoic ophiolite complexes in association with serpentinite and serpentinized peridotites and dunites (Ghazi et al., 2004; Shafaii Moghadam and Stern, 2014). There are more than 74 chromite deposits that have been explored in these complexes and they are mainly of alpine-type (Ghorbani, 2013). These ophiolite complexes are part of the Tethyan belts which link to other Asian ophiolite belts such as Pakistan and Tibet in the east as well as ophiolites in the Mediterranean region such as Turkey, Troodos, Greek, and east Europe in the west (Yaghoubpur and Hassannejhad, 2006; Hassanipak and Ghazi, 2000).New data in the current research study are used to infer the geology, mineralization, mineralogy, mineral chemistry and origin of the Qaranaz-Alamkandi chromite.

After preparing 72 samples from the study area, microscopic studies were carried out on 18 thin sections and 23 polished-thin sections for recognition of the microscopic features of the host rock as well as the mineralogy and texture of the ore body. Then, two chromite samples were analyzed at the Iran Mineral Processing Research Center, Karaj, Iran using electron microprobe and scanning electron microscope (SEM) methods.

The Qaranaz-Alamkandi chromite occurrence is located in the west of the Zanjan province and in the northern part of the Sanandaj-Sirjan zone. This area is composed of ultramafic sequences associated with Precambrian metamorphosed rocks such as amphibolite, marble, granitic gneiss and schist.According to petrographic studies rock units in the Qranaz-Alamkandi area consist of serpentinized harzburgite, serpentinized lherzolite, serpentinized dunite, serpentinite, amphibolite, amphibole schist, gneissic granite and mica shcist. This study show that the peridotitic rocks in this region include dunite, harzburgite and lherzolite. Olivine, orthopyroxene and lesser amounts of clinopyroxene associated with secondary minerals (such as serpentine, chlorite and calcite) and opaque minerals (chromite and magnetite) are the main minerals in peridotites.Mineral chemistry of olivines in the peridotites shows magnesium rich olivine with forsterite composition, slightly tending to chrysolite. The composition of olivines falls in the olivine spinel mantle array. Moreover, the olivines of dunites are comparable with those from the oceanic supra-subduction zone peridotites.Clinopyroxenes and orthopyroxenes are Fe-Mg-Ca rich. Furthermore, clinopyroxenes show augite composition and are mainly of the calcium- magnesium type. Orthopyroxenes show mainly bronzite and minor samples showing hypersthene composition. The composition of clinopyroxenes is similar to those of boninites and arc related magmas. This result and the given fact of the low contents of TiO2 and high contents of SiO2 in the structural formula of the pyroxenes suggest that the pyroxenes of the study area are comparable with those from the subduction tectonic settings.Chromite mineralization in the Qaranaz-Alamkandi area has occurred within the ultramafic rocks with serpentinized harzburgite and serpentinite composition. Due to the limited expansion of the peridotitic host rocks, chromite mineralization is also limited and it has occurred as lenses with maximum length up to two meters and one meter width. Chromite mineralization has occurred as massive, disseminated, lenzoid and vein- veinlets form in this area.Mineral chemistry of Chrome spinels from the Qaranaz-Alamkandi area indicate that the chromite samples plot within the ophiolite complexes and high- magnesium chromite field (Leblanc and Nicolas, 1992), which classifies them as podiform chromite deposits in terms of mineralization type (Arai et al., 2004).Chromite mineralization in the Qaranaz-Alamkandi area indicates an Alpine type deposit which is enriched in Cr and Mg and depleted in Ti. The Qaranaz-Alamkandi chromite mineralization has been formed from boninitic magmas which were derived from the subduction process in a supra-subduction zone and fore-arc tectonic settings (Ahrabian, 2018).

The Iranian plateau is part of the Alpine-Himalayan orogenic belt, which consists of several continental fragments separated from each other by major boundary faults and/or ophiolitic suture zones (Gansser, 1981). Generally, the tectonic evolution of Iran has been controlled by the opening and closure of the Proto-Tethys, Paleo-Tethys and the Neo-Tethys during the Precambrian-Cambrian, Paleozoic and Cenozoic, respectively.The study area is located in the northwest of Iran (the Kurdistan province) and 20 km northeast of the city of Saqez. This area is a part of the northern Sanandaj-Sirjan Zone (Aghanabati, 2005). This belt is response to opening and subduction of Neo-Tethyan oceanic crust beneath the Central Iran (Alavi, 1994). During Cretaceous-Tertiary eras, numerous granitoid bodies were formed in this belt. The Saheb granitoid is one of these granitoid bodies which mainly consists of monzogranite, quartz monzonite and quartz monzodiorite. The aim of this research study is to discuss the evolution of the Late Cretaceous-Early Paleocene Saheb granitoids in the Sanandaj-Sirjan zone based on geology, petrography and geochronology results.

In this study, 70 rock samples were collected from different types of intrusive rocks from which 30 thin sections were prepared for petrographic studies. Furthermore, four samples from the granitoid bodies (quartz monzonite, quartz monzodiorite and monzogranite) were selected for U-Pb dating. Approximately 100 to 150 zircon grains were hand-picked by a binocular microscope from each sample. Cathodo-luminescence imaging and dating of zircon grains were examined at the China University Geosciences (Wuhan branch). Geochronological analysis were performed by using the (LA)-ICP-MS method at the China University Geosciences (Wuhan branch). The detailed analytical method is presented in Liu et al. (2010a, 2010b).

Geology of the study area:

The Saheb granitoid body is located in the Sanandaj-Sirjan zone. According to the geological map of Chapan (scale: 1/100000, Kholghi khosraghi, 1999), the Precambrian to Quaternary units are exposed in the study area. The oldest units are the Kahar, Bayandor and Soltanieh Formations with Precambrian to Cambrian age. The Permian sediments, the Ruteh and Doroud Formations, include sandstone, shale and carbonate. The Jurassic units are found in the northwest of the region, and include sandstones and shale. The Cretaceous sedimentary units are located in the south of the study area. These sediments contain sandstone, limestone, silty-limestone, shale and dolomitic limestone. During Late Cretaceous-Early Paleocene era the Saheb granitoid intruded within the oldest units and caused Fe skarn type deposits in the Saheb area. The Saheb granitoid have been cut by a series of diabasic dikes.

The Saheb granitoid consists of several intrusive bodies containing quartz monzonite, quartz monzodiorite and monzogranite. The major minerals in the quartz monzodiorite consist of plagioclase (35- 40%), quartz (15- 20%), orthoclase (20- 25%), and mafic minerals such as biotite and amphibole (10-15%) with granular texture. The quartz monzonitic rocks show granular and poikilitic textures. Plagioclase (25- 35%), quartz, orthoclase (30- 40%), biotite and amphibole (10-15%) are the main important minerals in the quartz monzonite. Plagioclase (20-25%), quartz (20-30%), orthoclase (30-40%), biotite and amphibole (15%) are the major minerals in the monzogranite.Zoning in zircon crystals from all four samples is well developed representing their magmatic origin (Hancar and Miller, 1993). Measurements of U-Pb in the Saheb granitoid zircon grains of quartz monzonite samples show their ages to be 62.03±0.56 Ma and 58.9±0.9 Ma. The age of monzogranite is 67.9±1.3 Ma and the age of quartz monzodiorite is 61.1±0.56 Ma. Generally, the age of this granitoid body indicates that the Saheb granitoid has occurred during the Cretaceous- Paleocene time.

Based on field and microscopic studies, the Saheb granitoid bodies have been divided into three types of quartz-monzonite, quartz-monzodiorite and monzogranite. The field and mineralogical studies suggest that the Saheb granitoid is an I-type granitoid. The mineralogical variations in this granitoid suggest that the fractional crystallization has played an important role in differentiation of different compositional phases in the Saheb granitoid.According to the geochronological results, during Late Cretaceous to Early Paleocene, the Saheb granitoid intruded within the Permian and Cretaceous units in the magmatic-metamorphic Sanandaj-Sirjan zone. These granitoids were formed by subduction of Neo-Tethys Ocean beneath the Iranian plateau. It should be mentioned that the intrusion of these granitoids into the Permian carbonates and Cretaceous carbonate and shale caused formation of skarn type iron oxide mineralization.

Ghezeljeh area is located in the northeastern part of Mahneshan at 70 km northwest of Zanjan. The rock units exposed in the area are including the Lower Red, Qom, and Upper Red formations which the Upper Red Formation is the purpose of current research. According to field studies, the Upper Red Formation with 750 meters thickness includes 250 meters of evaporative units with intercalations of marls at the bottom and 500 meters of alternation of marls and sandstones intercalations at the top. According to microscopic studies, the grain size of the studied samples ranging from very fine sandstone to gravel. These sandstones show poorly orientation and well to poor sorted and are angular to sub-angular. The sorting and roundness parameters as well clay content show that these sandstones are immature and in some cases are sub mature. Based on a high percent of components and the Folk classification, the middle part of the Upper Red Formation displays lithic-arenite (sed-arenite) and feldspathic-lithic-arenite with an average composition of Q38F15Rf47. Geochemical studies show that these sandstones sourced from intermediate to felsic igneous rocks and deposited on the active continental margin. Furthermore, the weathering index shows an arid and semi-arid climatic condition during their deposition.

Geology, geochronology and tectonic setting of the Moghanlou mylonite gneiss and granite bodies, west of Zanjan Abstract The Moghanlou mylonite gneiss and granite assemblage is located in the west of Zanjan forming a part of the magmatic-metamorphic association in the Takab area. The Moghanlou assemblage comprises of leucogranite and biotite granite intrusions which have surrounded the gneiss body. The zircon U-Pb dating shows the ages of 563±6.5 Ma for the mylonite gneiss, 576±13 Ma for the biotite granite and 559±6 Ma for the leucogranite intrusions. Moreover, the samples from the Moghanlou assemblage display high-K calc-alkaline and slightly peraluminous affinities, except those from the leucogranite which are low potassium samples due to the sodic alteration and albitization of the K-feldspars. The trace element patterns suggest LILE and LREE enrichment and HFSE and HREE depletion as well negative anomaly of Nb, Ta and Ti. In general, the geochemical features of the Moghanlou intrusions are comparable with the melts formed from crustal partial melting in magmatic arc environment. The Moghanlou assemblage is analogues to other Late Neoproterozoic-Early Cambrian igneous and metamorphic associations in Iran and Turkey which are related to the igneous activity along the Cadomian magmatic arc, in north of Gondwana supercontinent.

The Qom Formation was deposited at the north-eastern coast of the Tethyan Seaway, in the Oligocene - Miocene, during the final sea transgression, in Central Iran (Reuter et al., 2009). Although the Mohammadi et al. (2013) believe that above 35˚N (including the study area in this research) deposition of the Qom Formation started during the Miocene. It is essential and important to study different properties of the oil-bearing Qom Formation because of economic importance and communicative role between Eastern Tethys (the proto-Indian Ocean) and the Western Tethys region (the proto-Mediterranean Sea) in the Iranian Plate at the same time (Mohammadi et al., 2013). Furrer & Soder (1955) subdivided the Oligocene-Miocene marine strata of the Qom Formation in the type locality of the formation near the town of Qom, into six members (a-f members: a-member basal limestone, b-member sandy marls, c-member alternating marls and limestones, d-member evaporites, e-member green marls and f-member top limestone). In the Zanjan area, only f-member of the Qom Formation has been deposited (Aghanabati, 2004). In general, the f-member consists of light colored, porous, in part chalky and in part cemented limestone. Although many studies have carried out for nearly four decades on the f-member of the Qom Formation outcrops in Central Iran back-arc basin (which they are listed in Mohammadi et al., 2013), stratigraphical, microfacies analysis and sedimentary environments studies of the f-member of the Qom Formation deposits of the Zanjan area has been the subject of only a few studies. So, here for the first time, we document and discuss the results of detailed fieldwork and microfacies analysis from the early Miocene carbonate platform succession in the south of Zanjan (f-member of the Qom Formation).

This study involves one stratigraphic section that was measured bed by bed and investigated sedimentologically.During the fieldwork study, detailed stratigraphic sections were measured, sampled and described with respect to carbonate facies and biota. The petrographic description is based on approximately 73 thin sections. Thin sections were stained using the method of Dickson (1965) to distinguish ferron and non-ferron calcite from dolomite. The petrographic classification for carbonates is based on Dunham limestone classification (Dunham, 1962). Flügel (2010) facies belts and sedimentary models were also used. The composition of associated fauna (presence of red-algae, coral, benthic foraminifer and echinoderm) and non-skeletal grains (e.g. intraclasts and peloids) was considered. Sedimentologic texture and structure (e.g. crossbedding, dolomitization, presence of silt-size quartz grains, boring and burrowing) have been considered qualitatively.

The Qom Formation in the Madabad celestite deposit (south of Zanjan), lithologically composed of 190 m of medium to thick-bedded and massive limestone and marly limestone. In this area, the Qom Formation is conformably overlies the clastic rocks of the Lower Red Formation and is in turn conformably overlain by the Upper Red Formation. In detail, the Qom Formation in the study area consist of 7 lithostratigraphic units as follow from base to top of the formation: 1) thin to medium-bedded limestone with interbedded of thin-bedded argillaceous limestone, 2) thick-bedded coral-bearing limestone, 3) thick-bedded limestone with interlayers of marly limestone, 4) thin-bedded marly limestone, 5)  thick-bedded echinoderm-bearing limestone with interlayers of marly limestone, 6) thin-bedded marly limestone and finally  and 7) thick-bedded to massive limestone with interlayers of marly limestone.The main components of the Qom Formation contain benthic foraminifera with hyaline test, coral, red algae with less frequency of planktonic foraminifera. Due to the abundance of red-algae, larger benthic foraminifera and micrite, the Qom Formation platform facies is referred to as “red algae foraminifera dominated packstone”. Field and microscopic studies led to identification of five microfacies in the limestone units of the Qom Formation in the Madabad area. These microfacies, ordered from shallower to deeper environments, include: A) red algae coral packstone, B) red algae bioclast packstone to wackestone, C) perforate benthic foraminifera packstone to wackestone, D) red algae echinoderm wackestone and E) planktonic foraminifera red algae bioclast wackestone.In general, microanalysis and paleoenviornmental interpretation of the Qom Formation show that this formation was deposited in a variable depositional system. The Qom Formation facies are dividable to four facies as follow: alluvial-deltaic facies carbonate platform-evaporatic facies, slope facies and basin facies (deep sea facies) (Rahimzadeh, 1994). Microfacies analysis including abundant hyaline-test benthic foraminifera as well as the lack of restricted lagoon microfacies show that in the Madabad section, the Qom Formation was deposited in open marine environment. According to recognized microfacies and absences of gravity deposits (turbidites), real and continuous reef, barrier and storm structures, carbonate platform of the Qom Formation developed on an open shelf without effective barriers separating it from the sea. In detail, the distribution of foraminifera and other components, in addition to the vertical microfacies relationships indicate that facies model of the Qom Formation in this section was distal-inner to middle shelf. The distal inner shelf including only the (A) microfacies and the other recognized microfacies (B-E) deposited through the proximal to distal parts of the middle shelf. Proximal middle shelf is characterized by larger benthic foraminifera with hyaline wall in addition to red algae and distal middle shelf is dominated by planktonic foraminifera and red algae.

The Qom Formation in the Madabad celestite deposit (south of Zanjan), lithologically composed of 190 m limestone and marly limestone. Field and microscopic studies led to identification of five microfacies. Distribution of foraminifera and other components, in addition to the vertical microfacies relationships indicate that facies model of the Qom Formation in this section was distal-inner to middle shelf platform.

Halab manganese deposit is located in the Sanandaj- sirjan zone, 100 km southwest of Zanjan. The rock units in the study area include Precambrian Kahar and Jangoutaran marble Formations. Manganese mineralization in the Halab area, occurred as veins and massive in the Jangoutaran marble and minor amount in the schist unit. The main important minerals in the Halab manganese mineralization consist of pyrolusite, psilomelane, manganite and goethite, which calcite and quartz occurred as associated gangue minerals. The ore textures include cloform, vein-veinlets, massive, comb, dogtooth, botryoidal, replacement and relict. Actinolite, carbonate and silicic are the main important alterations in this area. Primitive mantle normalized of the rare earth elements (REE) patterns in the orebody and hydrothermal carbonate samples show that the samples relatively enrichmed in light REE. The analyzed samples show significant negative anomaly in Ce and weak negative anomalies in Eu. Furthermore, the primitive mantle normalized pattern of trace elements in the orebody and hydrothermal carbonate show significant enrichment in Ba, U, La, Pb, Sr and negative anomaly in Rb, Th, Nb, Ce, P, Zr and Ti. The field and microscopic studies as well geochemical evidences suggest that the mineralization formed by hydrothermal fluids. The circulation of meteoric and/or magmatic fluids within the Precambrian units provide the important elements such as Mn, Fe and Ca for mineralization. When the mineralizing fluid contact with reactable rocks, caused the formation of Mn mineralization in the Halab area.

The Qoyjeh Yeylaq Pb-Zn (Ag) deposit located 120 km southeast of Zanjan, is situated in the Urumieh-Dokhtar magmatic arc.apart from Prior to this research no work has been published on Pb-Zn (Ag) mineralization at the Qoyjeh Yeylaq except for small scale geological maps of the area, i.e. 1:250,000 geological maps of Kabudar Ahang (Bolourchi and Hajian, 1979), 1:100,000 geological maps of Marzban (Majidifard and Shafei, 2006) and a number of unpublished Pb-Zn exploration reports.The present paper provides an overview of the geological framework, mineralization characteristics, and results of geochemistry study of the Qoyjeh Yeylaq deposit with application to ore genesis. Identification of these characteristics can be used as a model for exploration of this type of Pb-Zn (Ag) mineralization in this area and elsewhere.

Detailed field work has been carried out at different scales in the Qoyjeh Yeylaq area. About 26 polished- thin and thin sections from host rocks, mineralized and altered zones were studied by conventional petrographic and mineralogic methods at the University of Zanjan. In addition, a total of 11 samples from fresh and altered host rocks and ore zones at the Qoyjeh Yeylaq deposit were analyzed by ICP-MS for trace elements and REE compositions at Zarazma Co., Tehran, Iran.

The host rocks at the Qoyjeh Yeylaq deposit consist of Oligo-Miocene volcano-sedimentary rocks which are overlain conformably by Oligo-Miocene sedimentary rocks. Volcanic rocks are mostly basaltic andesite and andesite lava flows. Basaltic andesites with porphyritic texture consist of predominantly plagioclase (70 vol%) and clinopyroxene (25 vol%) phenocrysts with accessory Hornblende (<5 vol%) crystals. Andesites consists of plagioclase (75 vol%), hornblende (15 vol%), and clinopyroxene (10 vol%) phenocrysts set in fine-grained groundmass. The Oligo-Miocene sedimentary units consist of alternation of sandstone, red marl, and siltstone as well as medium-bedded to massive limestone with interlayers of tuff and shale. The Miocene sedimentary units consist mostly of alternations of red and green marl and red to grey sandstone.Mineralization at Qoyjeh Yeylaq occurs as quartz-sulfide veins in Oligo-Miocene basaltic andesite and andesite lavas. The ore zone reaches up to 150 m in length and 10 m in width. It has NNW-trending and mostly dips 70-80o to SW. Three stages of mineralization can be distinguished at the Qoyjeh Yeylaq deposit. Stage-1 is the most abundant, widespread, and economically important ore forming stage at Qoyjeh Yeylaq and is represented by quartz and sulfide (galena, sphalerite, and chalcopyrite) veins (up to 5 mm wide) plus breccias cement. Stage-2 is represented by 2 mm wide individual or sets of late calcite veins and veinlets that usually cut stage-1 mineralization. No sulfide minerals are recognized with stage-2. Covellite, cerussite, Fe-oxides and hydroxides are formed during the supergene stage (stage-3). They usually show replacement and vug infill textures.The hydrothermal alteration assemblages at Qoyjeh Yeylaq grade from proximal quartz and calcite to distal sericite, epidote, calcite and chlorite (propylitic alteration). The quartz and calcite alteration types are spatially and temporally closely associated with Pb-Zn (Ag) mineralization. The propylitic alteration marks the outer limit of the hydrothermal system.The ore minerals at Qoyjeh Yeylaq are formed as vein-veinlet and hydrothermal breccia cements, and show vein-veinlet, vug infill, and disseminated textures. Galena, sphalerite, and chalcopyrite are the main ore minerals; covellite, cerussite, and goethite are supergene minerals. Quartz, and calcite are present in the gangue minerals that represent vein-veinlet, breccia, vug--infill, and replacement textures. Comparison of Chondrite normalized (Nakamura, 1974) REE patterns of Oligo-Miocene fresh and altered basaltic andesite, andesite lavas, and the mineralized samples at Qoyjeh Yeylaq indicate that mineralization is probably genetically related with basaltic andesite and andesite lavas. In this case, leaching of some elements from the host basaltic andesite and andesite lavas may have been involved in mineralization.The geological, mineralogical, geochemical, textural and structural characteristics of the Qoyjeh Yeylaq deposit reveals that mineralization at the Qoyjeh Yeylaq deposit is an example of intermediate-sulfidation type of epithermal base metal (Ag) mineralization.

The authors are grateful to the University of Zanjan Grant Commission for research funding. The Journal of Economic Geology reviewers and editor are also thanked for their constructive suggestions on modifications of the manuscript.

According to Hitzman et al. (2005) and Hayes et al. (2015), the sediment-hosted copper deposits (SHC) are stratiform disseminated to veinlet copper mineralization within the reduced black shale, sandstone, and carbonate rocks. These deposits have formed during the middle-late Paleoproterozoic (e.g., Udokan, Russia: Volodin et al. 1994, Yinmin, South China: Zhao et al. 2013) to Tertiary (e.g., Corocoro, Bolivia: Flint 1989). The SHC deposits, frequently labeled as “stratiform” or “stratabound” and/or “diagenetic” deposits have been subdivided into three types (Cox 1986, Cox et al. 2003, Hitzman et al. 2005): 1- reduced-facies (RF), 2- Redbed (RB) and 3- Revett (RV). There are several SHC deposits in the Zanjan region hosted by the Upper Red Formation. The Chehrabad, Cherlangoush, Ghezeljeh, Halab, Ortasou and Sarikand deposits are the most important ones and are well-developed in this district. These deposits consist predominantly of bedding-parallel replacement and disseminated Cu-Pb-Zn sulfides, roughly concordant with stratification. The average Cu and Pb values of these deposits are ~3 and 2 wt.%, respectively. These deposits are small but they are actively mined at present. The aim of this work is to expand knowledge on the geological framework, mineralization features, geochemistry and genesis of the Ortasu Pb-Zn deposit. The study of the Ortasu deposit can be used as an exploration model for similar deposits in the Zanjan district and other places.

Detailed field studies have been done at different scales in the Ortasou area. Polished thin and thin sections from mineralized zones and host rocks were studied by conventional petrographic and mineralogic methods at the University of Zanjan. Furthermore, a total of six samples from mineralized host rocks were analyzed by ICP-MS for major and trace elements and Rare Earth Elements (REE) at Lab West Co., Australia.

The Ortasu Pb-Zn deposit is located in the northwest of Zanjan and Central Iran zone. The outcrop formations in this region involve Lower Red, Qom and Upper Red Formations from which the Upper Red Formation hosts the mineralized zones. In this region, the Upper Red Formation consists of alternation of red to brown and grey to greenish marl associated with interbedded sandstone sequences. Based on petrographic studies, composition of the mineralized host rocks are litharenite which consist of sedimentary, metamorphic and igneous fragments, quartz and feldspar. In the Ortasu Pb-Zn deposit, mineralization has occurred within two horizons of reduced-grey sandstone with about five to six m thickness and about 100 m length. These horizons contain both red oxidized zone and bleached zone with a mineralized reduced subzone which is located within the bleached zone. The red oxidized zone consists of red marl and sandstone layers containing iron oxides which is located adjacent to the reduced horizons. The red color of this zone is caused by the presence of iron oxides around the grains. The oxidized pyrite crystals are the main important minerals in this zone. The bleached zone is part of sandstone sequences whose color has changed by the alteration processes. Grey and green colors in the bleached zone have occurred due to the presence of organic materials and diagenetic pyrites. The mineralization subzone has occurred within the organic materials-bearing bleached zones. Plant debris, plant fossils, diagenetic pyrites and permeability of host rock have the main important role for Pb-Zn mineralization. Galena, sphalerite, pyrite and chalcopyrite are the main important minerals in the Ortasu Pb-Zn deposit in some parts. They have been replaced by secondary minerals such as cerussite, chalcocite, covellite and iron oxides due to the supergene and weathering processes. The most important textures in this deposit are disseminated and cemented textures. It should be mentioned that the laminated-like, framboidal pyrite, replacement and relict textures are also observed in this deposit. The presence of fining-upward sequences is due to the sediment cycles of channels, layered structures, abundant organic materials in paleochannels and debris of plant fossil all of which indicate that the Ortasu Pb-Zn deposit is formed in a continental to tidal environment. Geochemical studies show that the sandstones were deposited in an active continental margin. These sandstones originated from felsic magmatic rock and were deposited in an arid climate condition. According to host rock, geometry, structure and texture, and mineralogy it can be concluded that the Ortasu Pb-Zn deposit has more similarity with the distal parts of Redbed type of sediment-hosted copper deposits

The Dohneh copper deposit is located northeast of Zanjan within the Tarom subzone and the western Alborz-Azarbayjan magmatic belt. There are several reports of copper mineralization in the Tarom region such as the Aliabad Mousavi-Khanchay Cu deposit (Saeedi, 2015),the Lolan Cu-Au deposit (Zamanian et al., 2016), the Mari Cu deposit (Hosseinzadeh et al., 2016) and the Gheshlagh Cu deposit (Abbaspour, 2017) which make this subzone an important metallogenic zone in Iran. Prior to the present research, there was no detailed study done on the Dohneh Cu deposit. Thus, the aim of this research is to present detailed characteristics of geology, mineralogy and geochemistry of the host rock as well as the origin of Cu mineralization in the Dohneh area. The results of this study can be considered as an exploratory pattern in the Tarom-Hashtjin metallogenic belt in terms of time and space.

Petrographic and mineralogical features of the Dohneh Cu mineralization and host volcanic rocks were determined by studying 52 thin and thin-polished sections. Major and trace element compositions of six volcanic samples (the host of mineralization) were determined by the Iran Mineral Processing Research Center and Zarazma Company using XRF and ICP-MS methods, respectively. Furthermore, four samples were selected for electron microprobe and scanning electron microscope (SEM) analysis in the Iran Mineral Processing Research Center, Karaj.

The main rock units in the Dohneh area include Eocene tuffs and basalts which are related to the Kordkand member of the Karaj Formation. The tuff unit displays basic composition and is comprised of plagioclase, pyroxene, minor olivine and opaque minerals. There are also some basaltic fragments within the tuff unit. The Dohneh volcanic lavas can be divided into two lava flows varying in texture and mineralogy. The amygdaloidal basalt shows porphyritic and amygdaloidal textures and contains plagioclase, clinopyroxene, orthopyroxene, olivine and opaque minerals. The secondary minerals are carbonate, serpentine, epidote, chlorite, zeolite (filling the cavities), sericite and iron oxide. The second lava flow in the Dohneh area is the porphyritic basalt which shows specified porphyry texture which consists of pyroxene phenocrysts enveloped within the fine-grained matrix including plagioclase, olivine and pyroxene. The geochemical features of the Dohneh basaltic lavas show calc-alkaline nature with enrichment in LILE and LREE and depletion in HFSE and HREE. The Dohneh samples show negative anomaly of Nb, Ta and Ti in primitive mantle normalized spider diagrams. This geochemical evidence together with trace element data suggest that the Dohneh lavas have formed through partial melting of metasomatized lithospheric mantle. The status of the Dohneh samples in the tectonic discrimination diagrams shows subduction related magmatism analogous to those reported from the Tarom and Qazvin areas (Nabatian et al. 2014; Asiabanha and Foden, 2012). The Cu mineralization occurred in both amygdaloidal and porphyritic basalt lavas. According to e mineralography studies, the Dohneh deposit includes native copper, native silver, cuprite, malachite and azurite minerals. The minerals occur in the forms of vein-veinlet, open space filling, replacement and residual. The major alteration minerals in the Dohneh deposit include carbonate, chlorite, zeolite, and serpentinite and minor epidote, which have formed as replacement, vein-veinlet and open space filling in the host rocks. The field and microscopic observations, whole rock chemistry and mineral chemistry data from the Dohneh deposit suggest that the mineralization fluids and hot saline aqueous fluids have been generated during the late diagenesis and burial metamorphism in the volcanic sequence. During the ascending of fluids through the fractures and faults, the copper metal leached out of silicate minerals and turned into an elemental Cu2+ which is soluble in the fluid. Then, through the injection of mineralized fluids into the fractures and empty spaces of host rocks which was associated with decreasing pressure, copper and native silver minerals associated with zeolite formed at the end of the diagenetic stage, and in particular in the burial metamorphic phase. Moreover, during the circulation of fluids in the host rock, secondary minerals have formed. Consequently, mineralization of zeolite and part of copper mineralization occurred during burial metamorphism. In the final stages of mineralization and during the supergene and meteoric waters affected the minerals and caused formation of secondary minerals. In the final stages of mineralization and during the supergene and weathering activities secondary minerals have been generated. According to this study and comparing the characteristics of the Dohneh deposit to Michigan copper type deposits, it can be stated that the characteristics of the Dohneh copper deposit is the most similar to those of the Michigan copper deposits.

The Qom Formation is the only hydrocarbon reservoir in the central Iran sedimentary basin. In most parts of the central Iran, the Qom Formation conformably overlies the Lower Red Formation with an erosional discontinuity and is in turn conformably overlain by the Upper Red Formation. In the Madabad celestite deposit (south of Zanjan), the Qom Formation is composed of 190 m of medium to thick-bedded and massive limestone, marly limestone and marl. Five main microfacies are identified in the limestone units of the Qom Formation in the Madabad area. These microfacies probably were deposited on a shelf carbonate platform. Petrographic studies suggest original calcite mineralogy for limestone units of the Qom Formation in the Madabad area. Geochemical studies (Ca, Mg, Na, Sr, Mn and Fe) also represent the original calcite mineralogy in a closed diagenetic system with low dissolution rates. These evidence show significant role of fractures rather than diagenetic processes such as dissolution for increasing the reservoir quality of the Qom Formation for the oil and gas fields (such as Serajeh and Alborz) of central Iran.

Mianaj Fe ore occurrence is located in the Takab-Angouran-Takht-e-Soleyman metallogenic zone, 100 km southwest of Zanjan. In this area, Fe mineralization occurs as lens-shaped bodies parallel to the foliation of schist and rhyolitic meta-tuff units (equal to Kahar Formation). Based on mineralography, ore mineral is magnetite, and quartz present as gangue mineral at Mianaj. The ore minerals show disseminated, laminated, banded, massive, vein-veinlet and replacement textures. Three stages of mineralization can be distinguished at Mianaj. The first stage is recognized as stratiform and stratabound lenses, laminated and disseminated crystals of magnetite parallet to the foliation of host rocks. Stage-2 mineralization is recognized by folding of ore bands, σ microfabric and boudinage of magnetite crystals, quartz pressure shadows and surrounding of foliation around magnetite crystals, and recrystallization of quartz and magnetite crystals. Stage-3 is recognized by quartz vein-veinlets that cut previous mineralization stages. Chondrite-nonmineralized REE pattern of host rocks and the mineralized samples indicate that mineralized samples are depleted in REE. This signature indicates mobility of REE by Cl and F-rich oxidized fluids during mineralization processes. Characteristics of Mianaj occurrence are comparable with metamorphosed and deformed volcano-sedimentary type of iron deposits.

Pirgheshlagh Cu-Zn-Pb deposit is located in the Central Iranian zone, north-east of the Mahneshan in the Zanjan province. The Kahar Formation with Precambrian age is the oldest Formation in the area which cutted by the granitic dykes. The Pirgheshlagh Cu-Zn-Pb mineralization occurred mainly as tabular-shape within the metamorphosed sandstones, meta-andesitic tuff, meta-crystal lithic tuff and meta-andesite rocks. Based on the field and microscopic studies, the main minerals consist of chalcopyrite, sphalerite, galena, pyrite, arsenopyrite and minor magnetite. The ore textures consist of disseminated, laminated, massive and veinlet which the veinlet texture is occurred mainly in the lower part of deposit. Secondary minerals such as smithsonite, cerrusite, chalcocite, covellite, malachite, azurite, goethite and lepidochrosite have formed during supergene processes. The main alterations in the Pirgheshlagh deposit include silicic, sericitic, chlorite and carbonate. The results of this study suggest that the Cu-Zn-Pb mineralization in the Pirgheshlagh deposit is a Besshi-type valcogenic massive sulfide (VMS) mineralization.