Economic Geology
Mahdi Ghorbani- Dehnavi; Azadeh Malekzadeh -Shafaroudi; Mohammad Hassan Karimpour
Abstract
Chah-Nar Pb-Zn deposit is located south of Rutchun plain, 110 km SW Baft, within Sanandaj- Sirjan Zone. Mineralization occurs at calitic-dolomitic marble of Rutchun complex as epigenetic with structural control. Paragenetic minerals are galena and minor sphalerite and pyrite associated with ...
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Chah-Nar Pb-Zn deposit is located south of Rutchun plain, 110 km SW Baft, within Sanandaj- Sirjan Zone. Mineralization occurs at calitic-dolomitic marble of Rutchun complex as epigenetic with structural control. Paragenetic minerals are galena and minor sphalerite and pyrite associated with quartz, and minor calcite and dolomite, as gangue minerals. These minerals show veinlets, open space filling, breccia, and disseminated textures. Galena can be seen in the form of coarse grain crystal and cuboctahedral texture and fine grain crystal. Silicification and carbonatization are the most important alteration zones. Galena chemistry indicates galena is Ag, As, Cd and Zn -rich and Sn, Bi-poor. Sb/Bi ratio in galena is close to 3, which is indicator of low temperature deposits. Host rock type, stratabound and epigenetic mineralization, postsedimentary fault controlling, texture, ore types and gangue minerals, and lack of significant correlation between mineralization and igneous activities, chemistry of galena, indicate that Chah-Nar deposit is similar to MVT deposits, although it has some differences with this deposits type.
Stratigraphy and Palaeontology
Ebrahim Mohammadi; Mohammad Javad Hassani
Abstract
Paleoecology of the Qom Formation ostracods in the Bojan and Varkan sections have been studied. The age of the sections has determined base on foraminifera and is Rupelian-chattian for the Bujan and Chattian for the Varkan Section. Ostracoda content of the Bujan and Varkan sections include 44 and 33 ...
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Paleoecology of the Qom Formation ostracods in the Bojan and Varkan sections have been studied. The age of the sections has determined base on foraminifera and is Rupelian-chattian for the Bujan and Chattian for the Varkan Section. Ostracoda content of the Bujan and Varkan sections include 44 and 33 species respectively. The pecies of genus Cytheridea are the most abundant and the most dominant ostracods of the Bujan section. In the lower part of the Bujan section, different species of Cytherella and Cytheridea constitute the dominant ostracods, but upward the abundance of Cytherella is declined and Cytheridea, Neonesidea, and Bairdia are dominant. Podocopids constitute 76% and 86% of the Bujan section ostracods during Rupelin and Chattian, respectively. Neonesidea elegans, Bythocypris pseudoreniformis, Paracypris pandyai, Paracypris sapperi and Paracypris naalunensis constitute the dominant ostracods of the Varkan Section. Podocopid ostracods are dominant in the Varkan marls and constitute 77% of the ostracods. The high percentage of podocopid ostracods indicates that the environment was oxygen-rich and without the ecological stresses in both section; while in the Varkan Section, the ecological conditions are stable but in the Bujan section, the oxygen enriches upward and ecological conditions become closer to normal marin basins.
Petrology
Atefeh Nimroozi; gholamreza ghadami; Jamshid Hassanzadeh; Mohammad posti
Abstract
The study area is located near Abarkoh city and in Sanandaj –Sirjan zone. The volcanic activity of this region is in the form of dacite and rhyolite domes and lava flow and in the petrographic studies includes coarse plagioclase, quartz and hornblende. The volcanic rocks are considered as the separate ...
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The study area is located near Abarkoh city and in Sanandaj –Sirjan zone. The volcanic activity of this region is in the form of dacite and rhyolite domes and lava flow and in the petrographic studies includes coarse plagioclase, quartz and hornblende. The volcanic rocks are considered as the separate units interlayered with calcareous sedimentary units. Geochemical classification confirms the rhyolitic and dacitic composition of the volcanic unites and show their belonging to the calc-alkaline magmatic series, which is the characteristic of the subduction tectonic setting. Significant characteristics observed in spider and multi-element diagrams, such as their enrichment in LREE, high LREE / HREE ratio, Nb and Ti trough, and enrichment of Pb, Rb and Th elements demonstrate the continental crustal contribution to the development of the volcanics and their formation in the subduction environment in the active continental margin setting. Tectonic setting diagrams confirm this idea and determined a continental arc setting for the volcanic rocks of the area. The dating studies on zircon minerals yield the age of about 17.7.2 ± 7.6 ma equivalent to Jurassic for this part of the Sanandaj-Sirjan zone, which matches with the subduction stage of the Neotethyan Ocean below the central Iran zone.
Petrology
J. Ghalamghash; Sara Houshmand; Sayad Jamal Shaikhzakariaee; Hamideh Rashid
Abstract
The Kharsare intrusive mass (South of Ghorveh) is located in the middle part of the Sanandaj–Sirjan zone. The batholith comprises three plutonic units including gabbro- diorite, granite and syenite. In addition, the hybrid rocks with a lot of mixing and minling evidences (including lobate or/and ...
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The Kharsare intrusive mass (South of Ghorveh) is located in the middle part of the Sanandaj–Sirjan zone. The batholith comprises three plutonic units including gabbro- diorite, granite and syenite. In addition, the hybrid rocks with a lot of mixing and minling evidences (including lobate or/and ellipsoidal micro granular mafic enclaves sometimes with chilled margins in granite or in hybrid rocks; net-veining granite; and synplutonic brecciated mafic dikes) crop out in interaction zone between granites and gabbros. The calc-alkaline and metaluminous gabbro-diorite and High-K calc-alkaline and peraluminous granites emplaced in Late Jurassic, simultaneously. The peraluminous A-type syenite formed later and intrude two above mentioned plutonic rocks. Geochemical features suggest that gabbro-diorites and granites formed in an active continental margins. It seems the pioneer mafic magma formed in a subduction setting by partial melting of metasomatized mantle. It ascent and emplace in lower crust to produce the granitic melt. The mingling and mixing evidences that may support local crustal contamination of the mafic melt. The younger syenite is resulted from heating by intrusion of the mafic magma in the end phase of continental arc magmatism.
Economic Geology
Fattaneh Pourmohammad; Hossein Kouhestani; Amir Morteza Azimzadeh; Ghasem Nabatian; Mir Ali Asghar Mokhtari
Abstract
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, ...
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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.
R. Roshanak; A. R. Zarasvandi; H. Pourkaseb; F. Moore
Abstract
Main Travertines of Iran are located in a NW-SE trending belt (Urmia-Dokhtar Belt), extending from Tabriz to Zahedan. Neo-tectonic activities (Plecene to now) with travertine deposits around hot springs and volcanic features can be seen along this belt. In this study, East Azerbaijan travertines (northern ...
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Main Travertines of Iran are located in a NW-SE trending belt (Urmia-Dokhtar Belt), extending from Tabriz to Zahedan. Neo-tectonic activities (Plecene to now) with travertine deposits around hot springs and volcanic features can be seen along this belt. In this study, East Azerbaijan travertines (northern of Urmia-Dokhtar structural zone) is investigated and are compared with Kurdistan and West Azerbaijan travertine (northern of Sanandaj-Sirjan structural zone). The studied samples classify in thermogene category, using geochemical, mineralogical and 18O and 13C isotopes studies. Based on facies studies, northern Urmia-Dokhtar travertines fall in oncoid crystalline while Sanandaj-Sirjan travertines show oncoid, crystalline crust and pebbly facies. Using the measured δ13C values of travertine gives the δ13C of the CO2 released from the water during travertine deposition. Source of the CO2 in the water springs was crustal magmatic water. The stable isotope composition of two areas were compared with Turkey travertines and they show similar genesis, CO2 source and isotopic composition.
Tectonics
E. Haji; H. Safari
Abstract
The Saqqez-Baneh area, as a part of the NW Sanandaj-Sirjan zone, is selected for investigation of different deformation stages. In this research, firstly, the lithology of outcropped rock units and visible lineaments were mapped using remote sensing approach. Then, field surveys were carried out for ...
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The Saqqez-Baneh area, as a part of the NW Sanandaj-Sirjan zone, is selected for investigation of different deformation stages. In this research, firstly, the lithology of outcropped rock units and visible lineaments were mapped using remote sensing approach. Then, field surveys were carried out for structural measurements, during which major and minor faults and shear zones (as ductile zones) were measured and mapped. These data were then entered to GIS environment as vector layers (and attributed descriptions), resulting in preparation of a structural map. The results of field surveys along with geometric and kinematic analyses show that the major faults together with their related fault orders formed a curved shape of structures, outcropped rock unit patterns and intrusive localities. Geometric and kinematic analyses demonstrated three stages of movement: with north-south (in ductile environment), northeast-southwest (in ductile to brittle environment) and east-west (in brittle environment). These three stages caused three stages of faulting with trends along N140-150, N70-80 and N10-20 directions, which can be attributed to three orogenic phases in Precambrian and/or late Triassic (Katangai and/or Cimmerian), Cretaceous (Laramide) and Neogene (late Alpine events such as Savian to Pasadenian).
F Mousivand; E Rastad; M.H Emami; J Peter; M Solomon
Abstract
The Bavanat (Jian) pelitic-mafic- / Besshi-type Cu-Zn-Ag volcanogenic massive sulfide deposit locates in the Bavanat area, South Sanandaj-Sirjan zone. Mineralization occurs as two stratigraphic ore horizons discontinuously within the Surian metamorphosed volcano-sedimentary complex through more than ...
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The Bavanat (Jian) pelitic-mafic- / Besshi-type Cu-Zn-Ag volcanogenic massive sulfide deposit locates in the Bavanat area, South Sanandaj-Sirjan zone. Mineralization occurs as two stratigraphic ore horizons discontinuously within the Surian metamorphosed volcano-sedimentary complex through more than 35 km in the area. Stratigraphicaly, from footwall toward hangingwall, four ore facieses were distinguished within the Bavanat (Jian) orebodies including: 1) vein-veinlets or stringer, 2) vent complex, 3) bedded-banded, and 4) hydrothermal-exhalative sediments. The ores have various primary and secondary textures and structures, although most of the primary ones were obscured during metamorphism and deformation. The relict primary textures include massive, semi-massive, banded, brecciated, disseminated and vein-veinlet ores. In the stringer and specially in the vent complex facies, chalcopyrite replaced pyrite indicating influx of a hot copper-rich fluid into the pyrite-rich massive ores during zone refining process. Also, a metal and mineralogical zonation is obsereved in the Bavanat deposit. The major wall rock alterations in the Bavanat deposit from center to margins are silicic, quartz-chlorite, chloritic, chlorite-carbonate and chlorite-sericite, which show zonal pattern. Based on electron microprobe studies, chlorite is of iron-rich type. The abundant pyrrhotite in the Bavanat deposit might be due to low oxygen and sulfur fogacity, and occurrence of abundant chlinochlor in the alteration zones may indicate low pH (between 4.3 and 5.3) conditions for the ore-forming fluids. The high amounts of Cu and Zn, and low amounts of Pb, along with fluid inclusion studies results indicate high temprature (300-350 °C) for the ore fluids. Based on this study, the ore fluids responsibe for formation of the Bavanat deposit were hot, reduced and acidic, which entered into a confined marine basins, followed by ore deposition.
S Saki; H Ghasemi; M Sadeghian
Abstract
Bouin- Miandashtgranitoid pluton with an area of 40 Km2, outcropped in the north of Bouin Miandasht- Aligoudarz road, was emplaced into Triassic to early Jurassic low to medium grade metapelitic rocks of Sanandaj - Sirjan structural zone. This pluton composed of alkali feldspar granite to leucogranite. ...
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Bouin- Miandashtgranitoid pluton with an area of 40 Km2, outcropped in the north of Bouin Miandasht- Aligoudarz road, was emplaced into Triassic to early Jurassic low to medium grade metapelitic rocks of Sanandaj - Sirjan structural zone. This pluton composed of alkali feldspar granite to leucogranite. For the first time, variation of anisotropy of magnetic susceptibility (AMS) is applied to investigate magnetic fabric of this pluton. The Mean magnetic susceptibility values (Km in µSI) of the different rock groups of Bouin- Miandasht pluton are as follows: alkali feldspar granites (158), fine granites (120), coarse granites (166), and leucogranites (34). The lower Km values for the main compositions of this pluton (< 500 µSI) suggesting the paramagnetic nature of these granites. Biotite is the main carrier of magnetic properties in the studied rocks. The magnetic anisotropy (P %) varies from 1 to 15. Aalkali feldspar granites have the highest P value and show positive correlation with degree of deformation. Shape parameter of magnetic ellipsoid (T) values varies from -0.43 to 0.85 and most of the magnetic ellipsoids are oblate. Seventy five percent of specimens have positive T value. This subject indicates that magnetic ellipsoids are oblate and then foliation is prevailing, and also field evidence confirms this conclusion.
M Kazemirad; E Rastad; M Mohajjel
Abstract
The Goshti-Heneshk, Goli and Cheshmeh Esi iron-manganese deposits are located in the northeast of Dehdib (Safashahr), 175 km northeast of Shiraz. These deposits are situated in the Heneshk Shear Zone, which is a part of the ComplexDeformationSubzone of the Southern Sanandaj-Sirjan Zone. The oldest outcrops ...
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The Goshti-Heneshk, Goli and Cheshmeh Esi iron-manganese deposits are located in the northeast of Dehdib (Safashahr), 175 km northeast of Shiraz. These deposits are situated in the Heneshk Shear Zone, which is a part of the ComplexDeformationSubzone of the Southern Sanandaj-Sirjan Zone. The oldest outcrops in the area consist of the metamorphosed Permian shale, sandstone and crystalline limestone. The Middle Triassic dolomite units (equivalent to the Shotori Formation) have been thrusted on the Upper Triassic metamorphic and deformed volcano-sedimentary rocks and chert by thrust faults. The ore-bearing dolomites are often repeated due to imbricate thrust system in the area. The host rock to the ore is only dolomite, and ore bodies formed as lenses concordant by layering. The ore texture is massive, open space filling, lamination, and disseminated. The ore minerals include hematite, magnetite, goethite, kriptomelan, psilomelan and ramsdelite together with dolomite, calcite, quartz and barite. In the geochemical studies to determine the source of mineralization, Mn/Fe, Si/Al and Na/Mg ratios of major elements indicated that Fe-Mn ore formation occurred through the hydrothermal processes in shallow marine volcano-sedimentary environment. The trace element diagrams show low contents of elements such as Ni, Co, and Cu in the Fe-Mn ores. In these diagrams, the deposits of the study area plot in the field of hydrothermal deposits. Rare Earth Element distribution patterns of the deposits are quite similar to those of hydrothermal deposits. Two ore types are distinguished based on geometry and shape of the ore bodies: primary mineralization occurred parallel and concordant with layering of the host rocks. The ore textures of this type include massive, laminated and disseminated occurring in folded chert and dolomite. The vein-type mineralization is associated with the faults and has brecciated or cataclastic texture occurring in the Middle Triassic dolomite and Permian meta-carbonates. Based on the stratigraphic location, layer form of the ore body, texture, paragenetic sequence, ore-bearing chert-dolomite facies and geochemistry, the iron-manganese ores of the northeast Dehbid are stratabound carbonate-hosted deposits, which were precipitated in the shallow marine environment in the dolomites equivalent to the Middle Triasssic Shotori Formation.
E Moosavi; M Mohajjel
Abstract
The North Esfajerd ductile shear zone is exposed in NE Golpaygan in the Sanandaj-Sirjan zone. The shear sense indicators are observed in the both outcrop and microscopic scales in this shear zone. These indicators are representing a NW striking dextral shear. The dynamic analysis and outcrop- scale indicators ...
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The North Esfajerd ductile shear zone is exposed in NE Golpaygan in the Sanandaj-Sirjan zone. The shear sense indicators are observed in the both outcrop and microscopic scales in this shear zone. These indicators are representing a NW striking dextral shear. The dynamic analysis and outcrop- scale indicators of extension direction exhibit a NW extension sub-parallel to the dextral shear and a compression perpendicular to it. The relative simultaneity and parallelism between North Esfajerd ductile shear zone and North Varzaneh thrust shear zone propose the partitioning of strain components in a transpressional deformation. Regarding the geochronologic data and the angular unconformity between the middle Cretaceous and Eocene rock units, the transpressional deformation and its related mylonitization occurred during the Laramide orogeny in late Cretaceous-Paleocene. The gently dipping mylonitic foliations with dextral shear imply an incompatibility between geometry and kinematics in the North Esfajerd ductile shear zone. However, the kinematic and dynamic characteristics of the North Esfajerd ductile shear zone are accommodated with lateral extrusion of material in a dextral domain.
Parallelism between the trends of dominant stretching lineations and the second generation large scale fold axes document that the major mylonitization in the North Esfajerd shear zone occurred during the second generation deformation. These mylonitic fabrics were folded due to the third generation deformation. Two generations of crenulation cleavages, respectively in relation to two refolding events, can be recognized in this shear zone. One of the refolding events with type III interference patterns (coaxial refolding) occurred during the second stage deformation in the late Cretaceous- Paleocene interval, caused the formation of the North Esfajerd shear zone, and can be observed in an outcrop scale. The other has emerged during the third stage of deformation, probably in the post Paleocene-pre Miocene interval, folded the North Esfajerd shear zone and formed the type II (boomerang shape) interference pattern in a map scale.
F Mohammadi; S Alipour; M Ghazanfari
Abstract
Gold as a strategic element has a strong exploration potential in KurdistanCounty. This investigation for gold has carried out in N.W. Sanandaj- Siirjan geological zone. 351 samples has been taken from drainages and analyzed by ICP-MS in Canada for 22 elements. Based on results, anomaly map and enrichment ...
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Gold as a strategic element has a strong exploration potential in KurdistanCounty. This investigation for gold has carried out in N.W. Sanandaj- Siirjan geological zone. 351 samples has been taken from drainages and analyzed by ICP-MS in Canada for 22 elements. Based on results, anomaly map and enrichment ratio for gold and related paragenetic elements have been prepared. The result indicate an enrichment factor of 1-99 times for gold and 1-3, 1-19, 1-3, 1-3, 1-6, 1-2, 1-7, and 1-4 for elements Ag, As, Pb, Zn, B, Ba, Bi and W, respectively. Data resulted to a distribution pattern for Au and other elements such as. Gold anomaly is recognize in 36 Km2 associated up to 19 times enrichment for As. Therefore As is a good indicator element for Au her and in similar environments. Tectonically gold showed a very strong relation with breccias zones and par genetic minerals.
R. Arfania
Abstract
The study area, located in 40 km southeast of Eghlid town, is a metamorphozed terrain situated between the Eghlid fault and the Zagros Main Thrust and is a part of the southeastern Sanandaj-Sirjan Zone. The area consists of the highly deformed rocks which have been emerging clearly in dextral ...
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The study area, located in 40 km southeast of Eghlid town, is a metamorphozed terrain situated between the Eghlid fault and the Zagros Main Thrust and is a part of the southeastern Sanandaj-Sirjan Zone. The area consists of the highly deformed rocks which have been emerging clearly in dextral shear zones. Mesoscopic scale analysis carried out for determining the paleostress directions and deformation history of the area. Thus mesoscopic faults, joints and veins were measured and analyzed based on the field measurements and statistical methods. Then fitting structural models were presented for each of them. Furthermore, formation ages of the structures were considered based on relative time scale. According to the results, it can be concluded that two different deformation phases were effective in formation of the analyzed structures.
zahra badrzadeh; M. Sabzehei; E. Rastad; M. H. Emami; D. Gimeno
Abstract
The Sargaz massive sulfide deposit is situated near Jiroft (south-east Kerman), in the southern Sanandaj-Sirjan Zone. The host rocks are Upper Triassic to lower Jurassic(?) pillow basalt. The occurrence of mineralization in basaltic to basaltic andesite, the existence of Jaspilite and Fe-Mn horizons ...
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The Sargaz massive sulfide deposit is situated near Jiroft (south-east Kerman), in the southern Sanandaj-Sirjan Zone. The host rocks are Upper Triassic to lower Jurassic(?) pillow basalt. The occurrence of mineralization in basaltic to basaltic andesite, the existence of Jaspilite and Fe-Mn horizons in distal part of the deposit, the occurrence of a stringer zone discordantly under massive ore, the presence of pyrite as the main sulfide mineral, brecciated textures and mineralogical zonation in the massive ore, all suggest that the Sargaz deposit can be classified as a volanogenic massive sulfide deposit. The mineralogy is reasonably simple, with pyrite being the main sulfide mineral, with lesser chalcopyrite and sphalerite. On the basis of different generation of minerals, shape, size, their mutual geometry, relative timing of crosscutting structures and replacement features, brecciated textures and mineralogical zonation indicate that the growth history of the Sargaz deposit was complex due to syn and post depositional processes. Based on mineralogical, textural and paragenetic relationships, four principal stages of mineralization are recognized. Stage I mainly consist of fine grained pyrite (As rich), and locally sphalerite, quartz and barite. Framboidal pyrite, colloform pyrite and sphalerite were formed during this stage. After stage 1 mineralization, collapse of the sulfide mounds took place probably due to dissolution of anhydrite matrix, producing accumulations of pyrite breccias. Following this mound collapse, during stage II, pyrite (Co rich), sphalerite, tetrahedrite-tenantite and galena were formed as euhedral and coarse grains. Stage III deposits consist of chalcopyrite replacements and zone refining process. During this stage, due to zone refining, a chalcopyrite-pyrite zone was developed at the lower part of the massive sulfide lens and a sphalerite-rich zone formed in the upper part. During stage IV, over refining process, led to the dissolution of stage III chalcopyrite and base-metal depleted pyrite body in the lowermost part of the massive sulfide lens and carbonate veins were emplaced into the sulfide lens replacing earlier barite.
A. H. Sadr; Mohammad Mohajjel; A. Yasaghi
Abstract
The style of deformation changes from the hinterland (Sanandaj-Sirjan zone) to the foreland (Zagros) through the Zagros Orogen containing thick-skinned and thin-skinned deformation respectively. NW-SE trending thrust faults dipping to northeast have carried the older rock sequences to the surface. The ...
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The style of deformation changes from the hinterland (Sanandaj-Sirjan zone) to the foreland (Zagros) through the Zagros Orogen containing thick-skinned and thin-skinned deformation respectively. NW-SE trending thrust faults dipping to northeast have carried the older rock sequences to the surface. The Zagros collision zone could be divided into two distinct parts based on deformation mode that is separated by the Main Zagros Thrust. The southwestern part contains imbricate thrust sheets instead, to the northeastern part large amount of shortening is documented by basement deformation with duplex structures. Abundant crystalline deep origin thrust sheets have transported (2 up to 20 km) the metamorphic rock units upon the Zagros suture zone by gravity or tectonic forces. Despite the collision thrust faults, both NW oriented (Main Recent Fault) and NE oriented (named here Azna Fault) basement wrench faults have also activated and caused different style and amount of deformation in the collision zone.
M. H. Razavi1; A. Sayyareh
Abstract
In the south of Bijar, north east of Sanandaj in the Kordestan Province, and in the Sanandaj-Sirjan structural zone, young volcanic rocks are present. In this area, rocks with Cretaceous, Oligocene, Miocene and Pliocene ages are also observed. Based on field observations, volcanic activities occurred ...
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In the south of Bijar, north east of Sanandaj in the Kordestan Province, and in the Sanandaj-Sirjan structural zone, young volcanic rocks are present. In this area, rocks with Cretaceous, Oligocene, Miocene and Pliocene ages are also observed. Based on field observations, volcanic activities occurred during two main stages. In the first stage, eruption of pyroclastic material made a volcanic cone and a crater. In the next stage, lava erupted. Volcanic rocks are a combination of trachy-andesite, andesite, andesite-basalt and basalt. In the magma poor in silica, presence of olivine and analcime and lack of orthopyroxene and pygeonite are the evidence of alkaline type magma series. Petrographical evidences such as the existence of gneiss xenoliths and quartz xenocrysts with reaction rims are the results of contamination processes. In terms of geochemistry, the variations of Rb, Sr, Pb and Hf confirm this phenomenon as well. Based on low topography of volcanic rocks, suture zone, strike-slip faults, and petrologic evidence, low degrees of partial melting in source and crustal contamination in the region, the magmatism occurred in a tensional tectonomagmatic environment. Local tension and opening along the strike-slip fault zone provided a way for ascending of magma to the earth surface.
