Petrology
Afsaneh Naseri-Esfandagheh; Mohammad Rahgoshay; Sasan Bagheri
Abstract
The Haji-Abad-Esfandagheh-Faryab ophiolitic belt is one of the most famous chromite-bearing occurrences in the south of Iran that has received considerable attention. Golashkard ultramafic unit includes dunite, highly serpentinized harzburgites, chromitite and wehrlite layers in the Faryab ophiolitic ...
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The Haji-Abad-Esfandagheh-Faryab ophiolitic belt is one of the most famous chromite-bearing occurrences in the south of Iran that has received considerable attention. Golashkard ultramafic unit includes dunite, highly serpentinized harzburgites, chromitite and wehrlite layers in the Faryab ophiolitic complex located in the southeast of Sanandaj-Sirjan as one of the chromite-bearing areas of the Haji-Abad-Esfandagheh-Faryab ophiolitic belt. Ultramafic rocks and chromitites of Golashkard area consist of 20 to more than 50% of chromite. The studied chromites have variable massive, banded and scattered textures. The geochemistry of Golashkard ultramafic rocks shows that the average Cr# enrichment of chromite in serpentinite rocks (probably dunite and harzburgite) and wehrlite is to Cr/ (Cr + Al) ×100= 70-80 and in chromitite is relatively higher (Cr/ (Cr + Al) ×100= 81). Based on the lithological and mineral chemistry characteristics, Golashkard ultramafic rocks are part of mantle related to ophiolite, which was produced by a homogeneous boninitic melt in the suprasubduction zone and formed high chromium chromitites and related peridotites.
Petrology
Seyed Mohsen Kashfi; Saeed Alirezaei; Mohammad Reza Hosseini; Iraj Rasa
Abstract
The Zaghdareh area in the Esfandagheh-Faryab ophiolitic complex, southern Sanandaj-Sirjan belt, embraces extensive outcrops of mafic-intermediate lava flows and a felsic intrusive body. The volcanic rocks are calc-alkaline to tholeiitic, metaluminous, and distinguished by depletions in light rare earth ...
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The Zaghdareh area in the Esfandagheh-Faryab ophiolitic complex, southern Sanandaj-Sirjan belt, embraces extensive outcrops of mafic-intermediate lava flows and a felsic intrusive body. The volcanic rocks are calc-alkaline to tholeiitic, metaluminous, and distinguished by depletions in light rare earth elements and relatively flat patterns for heavy rare earth elements in chondrite-normalized diagram; the (La/Yb)N ratio is lower than unity for most samples. The chemical attributes for the Zaghdareh volcanic rocks are comparable to those developed in suprasubduction zones. The Zaghdareh intrusive body is distinguished by abundant plagioclase and quartz, and subordinate hornblende, phenocrysts in quartz-feldspar rich matrix. Representative samples from the intrusion plot in the trondhjemite-tonalite fields in the normative An-Ab-Or diagram. The intrusion is calc-alkaline to tholeiitic, peraluminous, and marked by enrichments in Na2O and CaO and depletions in K2O, Rb, and most other LILEs, as well as low K2O/ Na2O ratios, very low Rb/Sr ratio, and distinct depletions in light rare earth elements, which are typical of the oceanic plagiogranites. Results from this study and a comparison with other ophiolitic suites in Iran suggest that the occurrence of plagiogranites is a recurring feature associated with the development and evolution of ophiolitic suites in suprasubduction zones.
Petrology
Amir Esna-Ashari; Massimo Tiepolo
Abstract
The Malayer-Boroujerd plutonic complex (MBPC) is part of the Sanandaj-Sirjan continental arc of Iran resulted from subduction of Neotethys oceanic crust below Central Iran microcontinent. A number of adakitic samples have recently been reported in the MBPC. This study shows that among the various petrogenetic ...
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The Malayer-Boroujerd plutonic complex (MBPC) is part of the Sanandaj-Sirjan continental arc of Iran resulted from subduction of Neotethys oceanic crust below Central Iran microcontinent. A number of adakitic samples have recently been reported in the MBPC. This study shows that among the various petrogenetic processes responsible for the formation of adakitic rocks, two have been suggested in the genesis of those from the MBPC. i) interaction of crust-derived magma with ultramafic rocks and ii) crystallization of amphibole from a more basic magma. The former process leads to formation of intermediate to basic magma that subsequently crystallized amphibole in the ultramafic rocks. Amphibole growth was associated with textural and chemical changes toward the rim. Chemical modeling shows that amphibole growth was coeval with assimilation of olivines that their residue are remained as inclusions in the amphibole. The magma that formed the rim of amphiboles had higher Th, Zr, Ta and LREE but lower Ti and HREE than the core-forming magma. Assimilation of olivine during the amphibole growth prevented a decrease in Ni and Co content of the remained magma. Comparable chemistry of the rim-forming melt and MBPC adakitic rocks suggest that they are of the same origin.
Tectonics
Mohammad Reza Sheikholeslami
Abstract
Bajgan metamorphic complex is located at the southeastern termination of the Sanandaj-Sirjan zone in north of Makran. The metamorphic rocks, having igneous and sedimentary origins, are in tectonic contact with ophiolite assemblages and colored mélange. The rocks can be divided in four units based ...
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Bajgan metamorphic complex is located at the southeastern termination of the Sanandaj-Sirjan zone in north of Makran. The metamorphic rocks, having igneous and sedimentary origins, are in tectonic contact with ophiolite assemblages and colored mélange. The rocks can be divided in four units based on lithological characteristics. These units are covered by Pliocene and Quaternary sediments. Structural study indicates the presence of three syn-metamorphic stages of deformation in ductile condition. The main structures elements are different generation of folds, foliation and lineation, each of them has been generated during a specific stage and superimposed on each other. The structural elements in this complex have emerged during subduction, ophiolite obduction and exhumation, respectively.
Economic Geology
Hossein Ali Tajeddin; Ebrahim Rastad; Abdolmajid Yaghoubpour; Mohammad Mohajjel
Abstract
The Mirgenaghshineh gold deposit is located 43 km northwest of Saqqez in the northwestern part of the Sanandaj–Sirjan zone. The rocks in the deposit area predominantly consist of Precambrian volcanosedimentary sequences of schist, metasandstone, slate and metaandesite which are intruded by granitoid ...
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The Mirgenaghshineh gold deposit is located 43 km northwest of Saqqez in the northwestern part of the Sanandaj–Sirjan zone. The rocks in the deposit area predominantly consist of Precambrian volcanosedimentary sequences of schist, metasandstone, slate and metaandesite which are intruded by granitoid bodies. The Gold mineralization in the Mirgenaghshineh deposit is hosted mostly in Northwest-Southeast shear zone. The high grade gold ores occure in highly deformed mylonitic and ultramylonitic rocks that are associated with quartz, sericite-muscovite and sulfide alteration minerals. Ore mineral assemblages of the deposit are simple and consist of pyrite, arsenopyrite, sphalerite, chalcopyrite, galena and electrum. The electrum grains range in size from less than 5 µm to 140 µm and occur in quartz and also in the form of inclusion and veinlet in pyrites. According of geochemical data, gold-bearing ores carry up to 64.3 ppm Au, 9.9 ppm Ag, 2096 ppm As, 506 ppm Pb, 354 ppm Zn, and 244 ppm Cu. Fluid inclusion studies on gold-bearing quartz indicate homogenization temperatures between 158 and 215°C and salinity between 3.3 to 14.5 wt% NaCl eq. for the ore fluid. The study indicates that main characteristics of the geology and mineralization of the Mirgenaghshineh are similar to those of the epizonal orogenic gold deposits.
Economic Geology
Monireh Sakhdari; Mehrdad Behzadi; Mohammad Yazdi; Nematollah Rashidnejad-Omran; Morteza Sadeghi Naeini
Abstract
The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences ...
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The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences are affected by several deformation phase, gold mineralization occurs in ductile to ductile-brittle shear zones and had been under poly-phase metamorphism. The main alterations are Sulfidation, carbonization, silicification, chloritization, and sericitization. Ore-mineral assemblages include pyrite and chalcopyrite, arsenopyrite, sphalerite, galena, and Fe-oxide. Mean homogenization temperature in gold-bearing quartz range between 275oC and 300oC. Fluid inclusions in quartz veins are dominated by CO2-H2O-NaCl fluid. Salinity ranges from 9 to 17 wt. % NaCl equivalent. Corresponding to a depth of <2 km, Godar Sorkh deposit is formed in epizonal environment. Measured δ18O values for the gold-bearing quartz range between 12.7 to 14.3 permil, estimated δ18Ofluid values range from +6.4 to +7.3 permil, δ34S values range from –16 to +5 permil, and estimated δ34Sfluid values range from +4.2 to -17.3 permil. Fluid inclusion and stable isotope studies on ore-bearing quartz-sulfide veins indicating the major role of metamorphic fluids. Gold derived from metasedimentary rocks. Gold mineralization in the Godar sorkh deposit classified as an orogenic gold deposit.
Sedimentology
hajar ghafleh maramazi; Fardin mousivand; alireza zarasvandi
Abstract
The Gol-e-Zard zinc-lead deposit is located in the Malayer-Isfahan belt of Sanandaj-Sirjan zone in northeast of Aligudarz, Lorestan province. Mineralization occurred as two different ore horizon within metamorphosed Jurassic shale and sandstone. Generally, two ore facieses were distinguished in the deposit: ...
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The Gol-e-Zard zinc-lead deposit is located in the Malayer-Isfahan belt of Sanandaj-Sirjan zone in northeast of Aligudarz, Lorestan province. Mineralization occurred as two different ore horizon within metamorphosed Jurassic shale and sandstone. Generally, two ore facieses were distinguished in the deposit: 1) vein-veinlet/stringer facies, and 2) bedded facies. Primary minerals of the ores involve pyrite, sphalerite, galena and chalcopyrite, and the secondary minerals include cerussite, smithsonite, azurite, malachite and goethite. The gangue minerals are quarts, chlorite, calcite and clay-mineral. In the stringer facies, chalcopyrite replaced mainly pyrite and other minerals indicating influx of a copper-rich hot fluid influx into a pyrite-rich ore called as “zone-refining process”. In the Gol-e-Zard deposit metal and mineralogical zonation was observed. Alteration zones have distinct pattern, silicic-carbonatic at core to chloritic at margins. Based on textures and structures, mineralogical, ore facies, alterations and geochemical characters, the zinc-lead mineralization in the Gol-e-Zard region is of Selwyn-type sedimentary-exhalative (SEDEX) deposits, deformed and metamorphosed by the Late Cimmerian and Laramid Orogenies at green schist facies.
Petrology
sara shakiba; ali asghar sepahi; Mohammad reza Ghasempour; kazu nakashima
Abstract
Alvand plutonic body is one of the largest intrusive plutons in northern part of Sanandaj-Sirjan zone which is located in south of Hamadan city. It is composed of porphyroid and leucocratic granitoids, basic intrusive rocks, and abundant enclaves in various sizes and in a variety of forms. Biotites of ...
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Alvand plutonic body is one of the largest intrusive plutons in northern part of Sanandaj-Sirjan zone which is located in south of Hamadan city. It is composed of porphyroid and leucocratic granitoids, basic intrusive rocks, and abundant enclaves in various sizes and in a variety of forms. Biotites of porphyroid monzogranite, diorite, felsic microgranular enclave, mafic microgranular enclave and surmicaceous enclaves are located in magnesian biotites and biotites of norites in phlogopite field. Orthopyroxenes of norite are clinoenstatite and orthopyroxenes of mafic microgranular enclaves are clinofrosilite. Based on the Ti-in-biotite thermometer, temperature of monzogranite porphyroid is 662 to 734 oC, norite is 688 to 776 oC, diorite is 598 to 724 oC, surmicaceous enclaves temperature is 662 to 687 oC, felsic microgranular enclaves is 694 to 712 oC and mafic microgranolar enclaves is 635 to 737 oC. the enclaves of the Alvand plutonic body and their host rocks are located in the field of calc-alkaline suite. Orthopyroxenes in the norite and mafic microgranular enclaves indicate that rocks of the Alvand intrusive complex are located in the field of high oxygen fugacity rocks. It is in accordance with calc-alkaline property of rocks and is consistent with the subduction-related tectono-magmatic environment.
Petrology
Fahollah Mossavvari; Reza Zarei Sahamieh; Adel Saki; Amirali Tabakh Shabani; Ahmad Ahmadi-khalaji
Abstract
The metamamorphic rocks of Sanandaj-Sirjan Zone (SSZ) in the west part of Hamedan at CheshmehGhassaban village were intruded by olivine gabbro- gabbro at the middle Jurassic. The rocks consist of olivine, clinopyroxene, plagioclase, phologopite, brown amphibole and biotite and belong to alkaline series, ...
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The metamamorphic rocks of Sanandaj-Sirjan Zone (SSZ) in the west part of Hamedan at CheshmehGhassaban village were intruded by olivine gabbro- gabbro at the middle Jurassic. The rocks consist of olivine, clinopyroxene, plagioclase, phologopite, brown amphibole and biotite and belong to alkaline series, derived from partial melting in the stability field of a garnet peridotite. Moreover,LREE enrichment in chondrite normalized REE pattern, and relatively high ratios ofLaN/YbN (6.65-11.25)، Nb/Yb(22-22.38),Th/Nb(0.07-0.16) and Nb/Y (>1)indicate that the rocks originatedfrom an ocean island basalt like (OIB-like) sublithospheric mantle source and juxtaposed with and intruded into continental crust. With respect to geodynamic model of SSZ in the Alvand area in the middle Jurassic, ascribed to the subduction of the Neo-Tethys oceanic crust below the SSZ, the "Ridge-Trench" subduction model is proposed for thes egabbros. Based on this model, the subduction of the active spreading center of the Neo-Tethys oceanic crust produceda slab window in the subducted oceanic lithosphere, allowing infiltration of astenospheric hot OIB-like melt into SSZ. In addition, the development of a very substantial volume of S-type granitoid rocks in the Alvand granitoid complex of Hamedan region can be attributed to the melting of the metapilitic rocks due to ridge subduction events
Petrology
Sanaz Yajam; jalil Ghalamghash
Abstract
The easts Sanadaj- Galali plutons of the northern Sanandaj-Sirjan Zone, Zagros Orogeny, are composite, polyphase bodies that generated during subduction of Neotethys beneath the Eurasian plate. A-type magmatism in this area presents by Alkaline, high K, ferroan leucogranites. Despite having mineralogical ...
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The easts Sanadaj- Galali plutons of the northern Sanandaj-Sirjan Zone, Zagros Orogeny, are composite, polyphase bodies that generated during subduction of Neotethys beneath the Eurasian plate. A-type magmatism in this area presents by Alkaline, high K, ferroan leucogranites. Despite having mineralogical and isotopic similarities, these leucogranites show a clear division, based on the geochemical and SHRIMP zircon crystal dating results. Qalaylan leucogranite with the crystallization age of 159 ± 3Ma is A1-type. Other leucogranites are A2-type and crystalized about 20 million years later (140-149 Ma). In fact, mantle derived mafic magma, as heat source, caused partial melting of heterogeneous pre-fertilized Sanadaj-Sirjan basement and creates Qalaylan leucogranites. Younger leucogranites are A2-type and present different evolution path. These rocks generate in a post collisional setting as a result of partial melting of heterogeneous pre-fertilized Sanadaj-Sirjan basement, about 20 Ma later. In post collisional setting, asthenosphere upwelling do to the slab roll back or slab steepening could be a heat source of crust melting and generates the younger leucogranites.
Reza Emami; Reza Rezaei
Abstract
In this study, for estimating of coda wave attenuation in the North of Sanandaj-Sirjan Zone the seismograms of earthquakes recorded at the seismic stations which located at the longitude of 48°-50° and latitude of 38°-40° have been used. The data with an epicentral distance less than ...
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In this study, for estimating of coda wave attenuation in the North of Sanandaj-Sirjan Zone the seismograms of earthquakes recorded at the seismic stations which located at the longitude of 48°-50° and latitude of 38°-40° have been used. The data with an epicentral distance less than 200 km and a signal to noise ratio equal to or greater than 3 were used. Due to the volumetric percolation of the coda waves from the medium, the variation in coda waves quality factor was investigated in both lateral and depth, and the results were compared with the values obtained for other regions of Iran and the world. After applying the intermediate filter on waveforms in 10 frequency bands, the quality factor was estimated, and finally, the mean values of the quality factor and frequency dependence factor in the region by using two single-back-scattering and single-isotropic-scattering obtained QC꞊149 ± 9f0.66 ± 0.03 and QC꞊152 ± 12f0.66 ± 0.03 respectively. The comparison of the results with the values have been obtained in Central Iran (Qc꞊94f0.97), Alborz (Qc꞊79f1.07) and Southeast Zagros (Qc꞊72f1.19) indicate more homogeneity in the shallow depth layers and seismicity is lower than Central Iran, Alborz and Zagros. Also, for investigating the depth variations of the quality factor in the region, 11 lapse time window lengths were used in 5 seconds increments. The window lengths are begin from 10 seconds. In the lower window lengths, the low Q0 values represent high heterogeneity in shallow depths of the earth.
Afsaneh Badr; Nahid Shabanian; Alireza Davoudian; Hossein Azizi
Abstract
The North Shahrekord Metamorphic Complex (NSMC) in the center of Sanandaj-Sirjan Zone includes metagranite bodies, which has been intruded in some metamorphic rocks, especially schists. The NSMC metagranites display metamorphic and distinctive ductile deformation characteristics. These rocks are composed ...
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The North Shahrekord Metamorphic Complex (NSMC) in the center of Sanandaj-Sirjan Zone includes metagranite bodies, which has been intruded in some metamorphic rocks, especially schists. The NSMC metagranites display metamorphic and distinctive ductile deformation characteristics. These rocks are composed of quartz, alkali feldspar, plagioclase, biotite, amphibole, epidote, garnet, zircon, allanite, titanite, apatite and magnetite. Ages of the NSMC metagranites by zircon U–Pb shows the age of 523.92 [+ 5.03 – 5.73] Ma, and the whole rock Rb–Sr isotopes represents the age of 504 ± 47. The ages of NSMC metagranites (middle Cambrian) are younger than the Late Neoproterozoic - Lower Cambrian granitoids of the Sanandaj-Sirjan Zone, the NSMC metagranites are formed in the post-collisional setting, while the older granitoids are mostly related to volcanic arc. According to the morphology and shape of zircon crystals in NSMC metagranites, most of zircons are placed on S19 and S15 areas in morphology classification of zircon crystals, therefore, the granite magma of the area has hybrid (crust and mantle) origin. The crystallization temperature of metagranites, according to zircon morphology studies, is 750 to 850 °C, based on Zircon saturation calculation method, is 753.2 to 828.5 °C, and based on the graphical method (results of total rock chemical analyses), is 760 to 830 °C.
H. Shahbazi; H. Barjasteh; A. A. Sepahi; A. Mottaghi Tavana
Abstract
The Alvand batholith is located in the south of the Hamedan city and in the northern part of the Sanandaj-Sirjan metamorphic zone. Porphyroid granite, quartz diorite and diorite are formed rock members of the mesocratic granitoids in the Alvand plutonic complex. Porphyroid coarse-grained granites make ...
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The Alvand batholith is located in the south of the Hamedan city and in the northern part of the Sanandaj-Sirjan metamorphic zone. Porphyroid granite, quartz diorite and diorite are formed rock members of the mesocratic granitoids in the Alvand plutonic complex. Porphyroid coarse-grained granites make up the main volume of the Alvand bathilith. For study of minerals chemistry and thermobarometry of the mesocratic granitoids of the Alvand bathilith, microprobe analyses were carried out on the orthoclase, plagioclase and biotite in the porphyroid granites and were carried out on the amphibole, plagioclase and biotite in the quartz diorites and diorite. Mineral chemistry study shows that amphiboles in the quartz diorites are often of the magnesio-hornblende type and in the diorite are magnesio-hornblende and tschermakite type. Plagioclases in the porphyroid granite are albite and oligoclas type, in the quartz diorites are oligoclas and in the diorite are andesine type. Biotites in the mesocratic granitoids of these rocks are primary type and they are filled in the annite area. Results of thermobarometric study show that average of P-T conditions of amphibole crystallization in the mesocratic granitoids of the Alvand batholith are ~787 oC and ~1.46 Kb. Results of biotite thermobarometric study estimate that average of temperature and pressure of biotite solidification in mesocratic granitoids of the Alvand batholith are ~ 679 oC and 1.56 Kb. According to the pressure formation (~1.5 Kb) of the Alvand batholith, depth of its emplacement is estimated ~ 4.7 Km.
H. Rahimi Sadegh; S. H. Moein Zadeh; M. Moazzen
Abstract
The study area is a part of the Sanandaj-Sirjan zone which is mainly composed of metamorphic rocks, a variety of igneous basic rocks and sediments. the metamorphic rocks studied at west of Kheyrabad, North of Gol-e Gohar mine in Sirjan, Kerman Province are slate, phyllite, schist (garnet schist, amphibole ...
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The study area is a part of the Sanandaj-Sirjan zone which is mainly composed of metamorphic rocks, a variety of igneous basic rocks and sediments. the metamorphic rocks studied at west of Kheyrabad, North of Gol-e Gohar mine in Sirjan, Kerman Province are slate, phyllite, schist (garnet schist, amphibole schist, micaschist, kyanite schists), epidote amphibolite, amphibolite, gneiss, quartzite and marble. Amphibolite facies is the highest metamorphic grade in the region experienced by the rocks. Protolith of amphibolites is basic to intermediate igneous rocks with chemical composition of calc-alkaline. Based on Ti against V diagram and Nb-Zr-Ydiagram, amphibolites of the study area belong to mid-ocean ridges (MOR) and Volcanic arc tectonic environments in relation to Neotethys ocean.Mineral chemical features classify amphiboles as calcic amphiboles. average temperature of amphiboles is 630°C and maximum pressure is 7.5 kbar for the studied amphibolites. Geothermal gradient of ~ 28°C/Km indicates a continental crust setting for metamorphism.
R Jamali Ashtiani; Hassanzadeh J; M Rahgoshay; A Sharifi
Abstract
The Sanandaj-Sirjan zone is a NW-SE trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. This zone includes a Pan-African basement similar to the various terranes to the north in Central Iran. The crystalline basement is nonconformably ...
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The Sanandaj-Sirjan zone is a NW-SE trending orogenic belt immediately north of the Zagros suture, which represents the former position of the Neotethys Ocean. This zone includes a Pan-African basement similar to the various terranes to the north in Central Iran. The crystalline basement is nonconformably overlain by the Paleozoic-Triassic platform sediments, which in turn are unconformably covered by sedimentary and volcanic strata of the Jurassic arc. The Cretaceous carbonates overlie the older rocks with a regional angular unconformity. The Chadegan high-P metamorphic complex exposed along the upper Zayanderoud and consists of quartz schists, amphibolites, gneisses, marbles and eclogites, and is nonconformably underlain by the fossiliferous Permian carbonates, suggesting a Pre-Permian age. In this paper we present new data including whole rock major and trace element compositions, mineral chemistry and radiogenic isotope data for the selected metabasites. The high field strength element (HFSE) abundances and Sr-Nd-Hf ratios suggest tholeiitic compositions with distinct within plate affinity rather than MORB. We also present new 206Pb/238U zircon age of 568.0 ± 5.3 Ma for a crosscutting orthogneiss reconfirming the Late Neoproterozoic age for the granitic protolith. We conclude that previously presented Ar-Ar ages for white-micas in eclogites and gneisses are indicative of metamorphic crystallization due to the regional plutonic arc activity. A comparison is made with the well-investigated Menderes Massif in Turkey where an orthogneiss-metabsite association with similar age and chemistry makes extensive exposures. We also conclude that this rock complex is extended from Zayanderoud to Khoy and beyond to the Menderes Massif and discuss the connection with the final amalgamation tectonics of the Gondwana near the beginning of the Cambrian Period.
H. Fatehi; H. Ahmadipour
Abstract
Gole-Gohar, Ruchun and Khabr metamorphic complexes (South-west of Baft, Kerman province), form a part of the Sanandaj-Sirjan metamorphic zone and contain an alternation of metamorphosed impure limestone, sedimentary rocks and basic igneous rocks. Different studies show that the first metamorphic event ...
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Gole-Gohar, Ruchun and Khabr metamorphic complexes (South-west of Baft, Kerman province), form a part of the Sanandaj-Sirjan metamorphic zone and contain an alternation of metamorphosed impure limestone, sedimentary rocks and basic igneous rocks. Different studies show that the first metamorphic event has been associated with the first deformational phase and orientation of muscovite, garnet, quartz and feldspar in these rocks. At this stage, a foliation parallel to the primary bedding (S0) formed. The second metamorphic event which has accompanied with the second deformational phase, caused the formation of microfolds and preferred orientation of muscovite, biotite, garnet and amphibole in the second foliation (S2), but the third event has been acted as retrograde metamorphism that are corresponding to early Cimmerian orogenic phase. Geochemical characteristics of metamorphosed sedimentary rocks in the area suggest a shale origin for them. Correlations between units and lithological variations in stratigraphic columns from north-west to the south-east, indicate that in Gole-Gohar complex (western part of the area), metamorphosed detrital sedimentary rocks are frequent. This means that the primary sediments have been settled in a turbulent shallow environment and the basic magmas have been entered into the basin simultaneously. With the passing of time, toward the east and at the time of the formation of Ruchun complex protolith rocks, sedimentary basin has been deepened more and occasionally, limestone layers were formed between detritic sediments and igneous rocks. Then the basin became very deep and large volume of limestone precipitated during formation of Khabr protolith rocks. At this time, igneous activity had been ceased. Stratigraphic relationships in the studied complex suggest that Gole Gohar complex rocks formed first and placed at deeper levels at the time of the formation of their parental rocks. Therefore, the highest grade of metamorphism occurred at the western part of the area (Gole Gohar complex) and the lowest grade is observed at the eastern part (Khabr complex).
S Sedighian; S Dargahi; M Arvin
Abstract
Khunrang intrusive complex, as a one of the largest complexes in the southern part of the Sanandaj-Sirjan zone, is located at northwest of Jiroft, in Kerman province. The complex mainly consists of acidic-intermediate rocks such as diorite, quartzdiorite, tonalite, granodiorite, and granite with subordinate ...
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Khunrang intrusive complex, as a one of the largest complexes in the southern part of the Sanandaj-Sirjan zone, is located at northwest of Jiroft, in Kerman province. The complex mainly consists of acidic-intermediate rocks such as diorite, quartzdiorite, tonalite, granodiorite, and granite with subordinate amounts of mafic members such as hornblende gabbro and microgabbro. Field studies together with mineralogical and geochemical evidence show that the Khunrang intrusive complex belongs to calc-alkaline series and its felsic members are metaluminous to weakly peraluminous which display features typical of I-type granites. On the primitive mantle-normalized spider diagrams, all mafic and felsic samples are enriched in LILE (such as Rb, Cs and K) and depleted in Ti, Ta and Nb which is a main characteristic of subduction-related magmas. Based on geochemical data, the mafic rocks seems to be formed by melting of metasomatised mantle wedge; whereas felsic rocks are formed by melting of lower crust metabasic rocks as a result of the injection of mantle derived mafic magmas. It can be concluded that the Khunrang intrusive complex was formed in a volcanic arc setting due to subduction of the Neotethys oceanic crust beneath the Central Iranian Micro-continent in the Middle-Jurassic time.
B Hosseini; A.R Ahmadi
Abstract
Deformed granitoid rocks from North Saman represent part of magmatic activity in Sanandaj-Sirjan during the Mesozoic. The granitoid rocks intruded as separate intrusions into metamorphosed rocks which have protolith ages of the Palaeozoic and Mezosoic. The intruded granitoid rocks have been deformed ...
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Deformed granitoid rocks from North Saman represent part of magmatic activity in Sanandaj-Sirjan during the Mesozoic. The granitoid rocks intruded as separate intrusions into metamorphosed rocks which have protolith ages of the Palaeozoic and Mezosoic. The intruded granitoid rocks have been deformed as a result of subsequent tectonic activities. Zircon U-Pb ages of crystals extracted from the granitoid rocks gave ages of 182 ± 4 Ma and indicate that the granitoid rocks crystallized in the Toarcian stage of the lower Jurassic. The major and trace element goechemistry suggests a subduction-related, active continental margin setting for the granitoid bodies. The occurrences of numerous Jurassic granitoids reveal the importance of magmatic activities of this period in the Sanandaj-Sirjan zone.
M Mohajjel; S Niroomand
Abstract
Structural analysis of folds in the Kharapeh area clears tow co-axial folding stages in the Cretaceous metamorphic rocks, in this part of the Sanandaj-Sirjan zone. First stage folds are tight to isoclinal recumbent folds that were co-axially refolded by second stage upright open to close folds. Normal ...
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Structural analysis of folds in the Kharapeh area clears tow co-axial folding stages in the Cretaceous metamorphic rocks, in this part of the Sanandaj-Sirjan zone. First stage folds are tight to isoclinal recumbent folds that were co-axially refolded by second stage upright open to close folds. Normal faults, mafic dykes and abundant quartz veins oriented sub-parallel to the axial surface of the kharapeh antiform implying that the extensions were synchronous with folding perpendicular to the fold axis, during second stage folding process in the area. This is well concordant with tangential longitudinal strain folding mechanism for the second stage folding. By this folding mechanism, tension was produced at the outer arc of the Kharapeh anticline and quarts veins were generated by compression in the core area and filled in the tension fractures that were mostly produced in the fold hinge area during the folding process. In fractures where it was accompanied with shearing, some clasts from wall rocks were engaged in the fault zone breccias. The field observations reveal that the fractures were produced synchronous with the second folding stage in the Kharapeh anticline and filled by the gold bearing quartz veins.
F Mousivand; E Rastad; M.H Emami; J.M Peter
Abstract
Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), ...
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Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), and Chahgaz Zn-Pb-Cu (silicicalstic felsic-or Bathurst-type) deposits, and the north SSZ hosts the Barika gold-rich (bimodal felsic- or Kuroko-type) VMS deposit. Comparison of the VMS deposits, and investigating of possible relationship between formation of these deposits and tectono-magmatic processes within the SSZ indicate formation of all the deposits within intra-arc rift basins related to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate during Mesozoic period. Main reasons for formation of the different VMS types within the SSZ might be due to evolution of magma nature and intra-arc rift basins. Comparison between the deposits in many aspects including host and associated rock types and ore mineral paragenesis indicate clear differences between the Bavanat and Sargaz deposits and the Chahgaz deposit. It is inferred that the differences could be due to variations in magma compositions, i.e., felsic in the Chahgaz, and mafic in the Bavanat and Sargaz host sequences. Indeed, development of the intra-arc rifting was at early/nascent stage in the Bavanat and Sargaz regions and at mature stage in the Chahgaz area.The SSZ (particularly the southern part) due to hosting various VMS type deposits and involving the known largest and majority VMS deposits in Iran is the most attractive structural zone for VMS exploration.
M Asadpour; S Heuss; S. M Pourmoafi
Abstract
The Gharebagh intrusive complex which includes mafic, diorite and acidic rocks is a part of the Sanandaj-Sirjan zone in northwestern of Iran and a part of the Zagros orogenic belt. This complex has intruded into Precambrian metamorphic rocks. U-Pb daiting of zircons of a Lueicogranite has been identified ...
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The Gharebagh intrusive complex which includes mafic, diorite and acidic rocks is a part of the Sanandaj-Sirjan zone in northwestern of Iran and a part of the Zagros orogenic belt. This complex has intruded into Precambrian metamorphic rocks. U-Pb daiting of zircons of a Lueicogranite has been identified 558.6 ± 3.8 Ma. The cores of some zircon grains are aged too old to 2400 Ma in this sample. These are the parts of remained original rocks. It can be inferred that the basement area is older than Precambrian intrusive, and maybe indicate the presence of Panafrican basement similar to which has been found mainly in the central Iran. Ages obtained in five Gabbro samples are 300.0 ± 1.3 Ma to 301.5 ± 1.3 Ma, in two Diorite samples 300.7 ± 1.5 Ma and in a Monzogranite sample 300.7 ± 1.7 Ma. Age obtained in Alkaligranite pach within the Gabbros is 303.4 ± 1.5 Ma. These rocks have the same ages and that can be inferred that all of them have been affected by one geology event in late Paleozoic. Based on chemical analysis data, a mantle source for mafic rocks is understanded. This Mafic magma has a very high temperature so that its heat causes melting of the lower crust and formation the Alkaligranitic magma simultaneously with it intrusion. These datings, shows polotonism of upper Paleozoic in the northwestern part of Sanandaj–Sirjan zone. It can be inferred that this is the beginning of Neotethys opening in Iran.
J Ghalamghash; S. Houshmand Manavi; M. Vousoughi Abedini
Abstract
Oshnavieh Plutonic Complex (OPC), hosted within the northernmost part of the Sanandaj- Sirjan zone, allows distinguishing three suites including diorite, granite and alkalisyenite-alkaligranite (AS-AG). Dioritic rocks formed from partial melting of enriched lithospheric mantle sources on base of minerlogical ...
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Oshnavieh Plutonic Complex (OPC), hosted within the northernmost part of the Sanandaj- Sirjan zone, allows distinguishing three suites including diorite, granite and alkalisyenite-alkaligranite (AS-AG). Dioritic rocks formed from partial melting of enriched lithospheric mantle sources on base of minerlogical and geochemistry. The granite suite is S type that formed from partial melting of metapelitic-greywacke source. The peraluminous A-type granite of AS-AG suite are generated by partial melting of quartzo-feldspatic source at high temperatures. According to the negative Nb, Ta and Ti anomaly in spider diagrams, and tectonic discrimination diagram of Rb-(Y+Nb), the diorite suite formed in active continental margin (VAG) environment. According to the diorite’s formed environment and simultaneously formed granite in 100 M.a., OPC seems to have formed by northeastward subduction of Neo-tethyan oceanic crust under the Iranian continental crust. Following intrusion and setting of mafic magma into the crust, partial melting of pelitic-greywacke, resulted from heating by intrusion of the mafic magma, produced the granitic magma. After 20 Ma the AS-AG suite formed from melting of quartzo-feldspatic rocks of lower crust, probably by heating of mafic magma and/or in relaxation period of subduction and emplaced in the continental volcanic arc.
Behnaz Hosseini; M. Ghorbani; S. M. Pourmoafi; A. R. Ahmadi
Abstract
Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, ...
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Kuh-Sefid anticline trends in NW-SE direction and locates in southern Sanandaj-Sirjan zone, and it contains a sequence of Paleozoic metamorphic rocks with facies ranging from greenschist to lower amphibolite. There are granitoid rocks emplaced in the core of this anticline, which based on their facies, these rocks are divided into two groups of "augen geneiss " and "metagranitoid". During the course of previous studies, these two rock groups had been attributed to a magmatic phase in Mesozoic, which experienced different degrees of deformation. In this study we proceed to determine the age of these two granitoid rock groups based on U-Pb age dating method applied on Zircon minerals. As a result, the age of orthogneiss rocks is 514±24 million years old and they belong to Cambrian, whereas metagranitoid rocks are 173±9 million years old and attributed to Middle Jurassic. Based on geological and structural evidences, the magmatism occurred in Cambrian was related to tension tectonics in Late Precambrian to Early Paleozoic, while the magmatism in Middle Jurassic associated with dextral transpression tectonics in the studied area.
M. Aflaki1; M. Mohajjel
Abstract
Laibid (northwest Esfahan) metamorphic rocks are situated in complexly deformed sub zone of the Sanandaj-sirjan zone, in which bounding faults emplaced Permian metamorphosed, beside the younger Triassic-Jurassic metamorphic rocks. Structural study of these units reveals three deformation stages of a ...
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Laibid (northwest Esfahan) metamorphic rocks are situated in complexly deformed sub zone of the Sanandaj-sirjan zone, in which bounding faults emplaced Permian metamorphosed, beside the younger Triassic-Jurassic metamorphic rocks. Structural study of these units reveals three deformation stages of a progressive deformation in this area. The first stage includes tight to isoclinal folds, the second stage includes open to close folds and the third one includes gentle to open folds. From the first to the third stage, fold's wavelength gradually become longer, so that their aspect ratio change respectively from tall and short, for the first stage, to broad, for the second stage, and to wide, for the third one. Superposition of these fold generations caused in coaxial interference patterns. It seems that during Late Jurassic, these three folding stages consequently formed and passively rotated in a continuous deformation condition, by gradually decreasing deformation depth. Dikes alternatively injected into the extensional fractures and through the axial plane foliation and gradually deformed in to the fold, boudin, folded boudin, and boudined fold.
M. Mohajjel; L. Izadi kian
Abstract
Almabolagh region is located in northwestern part of the Sanandaj-Sirjan zone of Zagros orogen in western Iran. This area is located 15 km to the west of Hamadan. Three rock units consisting of volcani-sediments (Almabolagh sequence) at the lower part, carbonate (Chenarsheikh ...
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Almabolagh region is located in northwestern part of the Sanandaj-Sirjan zone of Zagros orogen in western Iran. This area is located 15 km to the west of Hamadan. Three rock units consisting of volcani-sediments (Almabolagh sequence) at the lower part, carbonate (Chenarsheikh sequence) in the middle, and slate (Hamadan slate) at the upper part are identified. These rocks that are metamorphosed at green schist facies have been exposed in a dome structure. Four stages of deformation (D1, ..., D4) are identified in the tectonites. D1 structures include first generation folds and related axial planar schistosity. D2 structures are recognized by tight to isoclinal, recumbent shallowly plunging folds, with horizontal to sub-horizontal axial plane schistosity which is the predominant foliation in this area. The mechanism of folding in this stage is flexural shearing and passive flow. D3 structures are identified by the third generation foliation that is weakly developed parallel to the axial surface of related upright, open to gentle folds. The third generation folds were produced by flexural slip mechanism. A dome structure generated by intrusion of magmatic batholith in this region and structural elements of the main deformation stages (D2) were rotated.
