Petrology
Hamid Karimzadeh; Mohammad Rahgoshay; Iman Monsef
Abstract
The petrographical examination of peridotites of the Nehbandan ophiolitic complex revealed that the peridotites of Kalateh Shahpouri, Qadamgah, Lah-Kouh, Cheshmeh anjir, Bandan, and Zolfaghari were of harzburgite type and Sefid-Kouh and Nasfandeh-Kouh were of lherzolite type. Generally, the types of ...
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The petrographical examination of peridotites of the Nehbandan ophiolitic complex revealed that the peridotites of Kalateh Shahpouri, Qadamgah, Lah-Kouh, Cheshmeh anjir, Bandan, and Zolfaghari were of harzburgite type and Sefid-Kouh and Nasfandeh-Kouh were of lherzolite type. Generally, the types of clinopyroxenes in the peridotites of this complex were diopside. The geochemical investigation of clinopyroxenes in Mg# vs. Al2O3, Cr2O3, and TiO2 graphs and Ti vs. Nd, Zr, and Sr graphs shows that the peridotites of Nasfandeh-Kouh, Bandan, Zolfaghari, and Sefid-Kouh with a low degree of partial melting belong to the Abyssal tectonic setting and back-arc basin.on the other side, the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were formed in the Supra-subduction zone tectonic setting and fore-arc basin and have a high degree of partial melting. The study of incompatible elements, LILE and HFSE in spider diagrams normalized to the primary mantle and as well as the study of REEs in spider diagrams normalized to the chondrite for clinopyroxenes confirm this issue. Therefore, Nasfandeh-Kouh and Sefid-Kouh lherzolites as well as Qadamgah, Lah-Kouh, Bandan, and Zolfaghari harzburgites with a low degree of depletion were more consistent with the Mid-oceanic ridgestectonic setting, and the harzburgites of Kalateh Shahpouri and Cheshmeh anjir were close to the Supra-subduction zone tectonic setting with a high degree of depletion.
Stratigraphy and Palaeontology
Zahra Khajehjavaran; Gholam Reza Ghadami; Mohammad Poosti; Abbas Moradian; Behrouz Karimi Shahraki
Abstract
Andesites are located in the north of shahr-e-babak , central Iran, Urumieh- Dokhtar belt. The main texture in these rocks is porphyry and their phenocrysts are plagioclase (Andesine to Labradorite), pyroxene (Augite), amphibol (Tschermakite and Magnesiohornblende). These properties are signatures of ...
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Andesites are located in the north of shahr-e-babak , central Iran, Urumieh- Dokhtar belt. The main texture in these rocks is porphyry and their phenocrysts are plagioclase (Andesine to Labradorite), pyroxene (Augite), amphibol (Tschermakite and Magnesiohornblende). These properties are signatures of calc- alkaline series formed in a volcanic arc setting. Based on geochemical studies, the rocks show enrichment in LREE rather than HREE. The lack of significant Eu anomalies in REE pattern indicates oxidation state of magma during crystallization. Based on geochemical studies, the clinopyroxenes are Augite and have been crystallized from magma with almost 10% H2O. Fe3+ values of the clinopyroxenes reveal high oxygen fugacity in the magma. Based on the mineral chemistry data, pressure estimates from the clinopyroxenes in the range of 6-10 Kbr and composition yield the crystalization temperatures that range from 900-1100 OC. Typically, clinopyroxenes occure at calc-alkaline orogenic igneous rocks. The plagioclase composition yield the crystalization temperatures that range from 650-750 OC. According to the present study, the rocks are probably the result of the subduction of the Neo-Tethys oceanic lithosphere below the Sanandaj-Sirjan zone, during the Eocene and in a volcanic arc environment.
Petrology
Ali Lotfi Bakhsh
Abstract
In the north of Ardabil (from Namin to Lahroud) there are widespread sequences of Eocene and Quaternary mafic to intermediate and felsic magmatic activities with different compositions. The composition of these rocks varies from basaltic lavas as well as dacitic and rhyolitic domes in Namin to basalt ...
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In the north of Ardabil (from Namin to Lahroud) there are widespread sequences of Eocene and Quaternary mafic to intermediate and felsic magmatic activities with different compositions. The composition of these rocks varies from basaltic lavas as well as dacitic and rhyolitic domes in Namin to basalt and basaltic andesite in Lahroud area. The chemical composition of olivine from olivine basaltic lavas indicates a forsterite composition changing from 67.8 to 92.7. Clinopyroxenes show diopside composition whereas plagioclase has labradorite to bytownite composition. Garnet xenocrysts in the rhyolitic domes have an almandine composition. These rocks are characterized by the enrichment in LREEs compared to the HREEs. Mafic-intermediate rocks show shoshonitic to high-K calc-alkaline composition whereas dacitic and rhyolitic domes show adakitic signature. Geochemical and isotopic characteristics of basaltic-andesitic rocks indicate their genesis are related to the partial melting of a metasomatized mantle wedge, re-fertilized by sediments and fluids from the subducting slab in the Eocene subduction zone of Iran. The geochemical and isotopic signatures of dacitic-rhyolitic domes indicate their origin from partial melting of the lower parts of the thickened continental crust of Iran.
Petrology
Jalil Ghalamghash; Meysam Akbari; Reza Jamal
Abstract
The Taftan volcano hosts an extensive volcanic activity during Late Miocene to Quaternary where took place over Makran-Chagai subduction zone. Taftan rocks are mainly basaltic andesite, andesite, trachyandesite, and dacite that occur as lavas and pyroclastic rocks. They are characterized by basic-intermediate ...
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The Taftan volcano hosts an extensive volcanic activity during Late Miocene to Quaternary where took place over Makran-Chagai subduction zone. Taftan rocks are mainly basaltic andesite, andesite, trachyandesite, and dacite that occur as lavas and pyroclastic rocks. They are characterized by basic-intermediate inclusions enclosed by acidic groundmass, and disequilibrium textures in plagioclase phenocrysts including sieve texture, zoning, and dissolution margin, which may reflect magma mixing. These rocks record high-K calc-alkaline to calc-alkaline affinity with enrichment in LREE and LILE relative to HREE and HFSE, respectively. These features, coupled with the clear depletion in HFSE (such as Nb, Ta, and Ti) are consistent with typical subduction-related volcanic arcs. Taftan primary melts might have been produced by ~15% partial melting of spinel lherzolite mantle. The normalized multi-element patterns which mimic the upper continental crust values, and enrichment in Pb, Th, U, and Rb agree well with magma evolution by assimilation and fractional crystallization (AFC). The available isotopic geochronology dataset reveal that the youngest volcanoes of the Makran-Chagai magmatic arc are Bazman and Kuh-e-Sultan volcanoes. A geochemical comparison of these volcanoes highlights that magmatism in the Taftan where the crust is thick, underwent a higher degree of crustal assimilation en route to the surface.
Petrology
Ziba Khodaean Chegeni; Nematollah Rashidnejad Omran; Ali Akbar Baharifar; Reza Nozaem; Carmela Vaccaro; José Francisco Santos
Abstract
Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or ...
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Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or their intrusive equivalents with calc- alkaline to tholeiitic affinity and even a peridotite could be their protoliths. Trace element and Sr-Nd ratios imply that these rocks were from mantle melt sources. In chondrite normalized plots, these amphibolites can be classified into at least two groups. The first group is characterized by LREE depletion relative to HREEs and some with flat patterns. The second has an enrichment of LREEs relative to HREEs. These two different patterns and some other geochemical characters suggest MORB or MORB-like and arc affinities of the parental magmas. This can be related to the time progressive evolution of magmatism either from MORB or Back-arcto Arc or from Arc to Back-arc setting.
Sedimentology
Mohammad Shalalvand; Mohammad Adabi; Afshin Zohdi
Abstract
In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of ...
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In this study, the Late Paleocene Taleh Zang Formation in the southwest of Kermanshah hasbeeninvestigatedfor elemental geochemistry and effective diagenetic processes during burial. The thickness of the studied section is 282 meters that mainly composed of shallow marine limestones with interbedded of marl and dolomite. The main diagenetic processes affecting the TalehZangFormation include micritization, various types of porosity, cementation, dolomitization and compaction. Due to the texture and the abundance of unstable skeletal particles (green algae and bivalve), porosity and cementation aremorecommon among the identified processes. Microscopic and geochemical studies have shown that these processes have taken place in eogenesis and early mesogenesis stages in marine, meteoric and shallow burial environments. Evidences indicate that the carbonates of the TalehZangFormation didnot tolerate deep burial after the deposition during diagenesis. Fluids that affected the lower parts of the formation during burial were mainly marine. Moreover, tothetop ofthe sequence in addition to seawater less meteoric fluids have affected the marine carbonates of the Taleh Zang Formation during diagenesis. The high amounts of Sr/Mn (mean27/51) and Sr/Ca (mean 1/61) and also low Mn (mean 27ppm) and Fe (mean 78ppm) values indicate close digenetic system with low water/rock interaction for the carbonate samples of the TalehZangFormation.
Sedimentology
Hadi Amin-Rasouli; Hossein Azizi; shahla mahmodyan
Abstract
The Upper Cretaceous succession (UCS) of the north Sanandaj-Sirjan zone consists of five units. The units are 2000 m thick, including shale, sandstone, limestone, intrafomational conglomerate with interbedded basaltic- andesitic lava. This succession is unconformably underlain by Lower Cretaceous and ...
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The Upper Cretaceous succession (UCS) of the north Sanandaj-Sirjan zone consists of five units. The units are 2000 m thick, including shale, sandstone, limestone, intrafomational conglomerate with interbedded basaltic- andesitic lava. This succession is unconformably underlain by Lower Cretaceous and overlain by Paleocene conglomerates. The geochemistry of the samples represents ratios of Al2O3/TiO2 (18-22), La/LuCN (5.43-24.4), La/Sc (0.51-2.53), Th/Sc (0.42-0.68), LREE/HREE (Nd/ErCN > 5), and negative anomalies of Eu/Eu* (0.26-0.89) and Nb/Nb* (0.14-0.82). These characteristics indicate that the samples are immature, first-order sediments, and were eroded from intermediate to acidic arcs in the subduction zone. The volcanic rocks were formed during the intracrustal melting of an altered oceanic slab at high pressures in the garnet-amphibolite facies. The geochemical compositions and vertical lithofacies stacking patterns of the UCS imply that the depositional environment has changed during sedimentation from a trench to trench slope and forearc basins arising from continent-ward migration of the magmatic arc. The activities of Late Cretaceous volcanism resulted in the upwelling of anoxic water, demise of planktonic, and formed pyrite in the deposits. Samples on the Th/Yb-Ta/Yb diagram fall in the ACM and WPVZ fields, indicating tectonic evolution from low-gradient subduction to extensional volcanic conditions.
Remote Sensing
Mahya Nazarian; Mohammad Lotfi; Arash Gourabjeripour; Majid Ghasemi Siani
Abstract
The Chomalu Polymetallic deposit is located in western part of Alborz magmatic belt (Alborz-Azarbaijan) and central part of Tarom-Hashtjin metallogenic province. Eocene volcanic settings in the Chomalu deposit consist of basic rocks (olivinebasalt), intermediate (andesite basalt, andesite to trachyandesite) ...
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The Chomalu Polymetallic deposit is located in western part of Alborz magmatic belt (Alborz-Azarbaijan) and central part of Tarom-Hashtjin metallogenic province. Eocene volcanic settings in the Chomalu deposit consist of basic rocks (olivinebasalt), intermediate (andesite basalt, andesite to trachyandesite) and acidic rocks (dacite to rhyolite) which is intruded by quartz monzodiorite, monzosyenite and quartz monzonite intrusive rocks of Eocene. The main texture of volcanic rocks is more porphyritic. Olivine and plagioclase are the main phenocrysts in the olivinebasalt, andesite rocks compose of plagioclase and clinopyroxene and dacite to rhyolite consist of plagioclase, alkali feldspar and quartz. On the basis of AFM diagram, Chomalu volcanic rocks located in the high- K calc- alkaline to shoshonitic affinities in relation to subduction zone magmatism. Primitive mantle-normalized of volcanic rocks indicate that LILE enrichment and HFSE depletion in consistent with subduction zone magmatism. Chondrite-normalized REE patterns show LREE/HREE enrichment. Geochemical results suggesting primary source magmas source for volcanic rocks were generated by partial melting of the metasomatized lithospheric mantle-wedge in relation to subduction arc and were subsequently affected by both fractional crystallization and crustal contamination during magmatic evolution.
Petrology
Mahsa Jamshidnia; manijeh Asadpour; Masoumeh Ahangari
Abstract
Qushchi gneisses in the north of Urmia city are a part of magmatic-metamorphic complex in NW of Sanandaj-Sirjan zone. Gneiss, with eldsparses and schist, form Precambrian basement of the area. These rocks contain lipidogranoblastic, augen, porphyroblastic and myrmekite textures, and composed of quartz+ ...
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Qushchi gneisses in the north of Urmia city are a part of magmatic-metamorphic complex in NW of Sanandaj-Sirjan zone. Gneiss, with eldsparses and schist, form Precambrian basement of the area. These rocks contain lipidogranoblastic, augen, porphyroblastic and myrmekite textures, and composed of quartz+ alkaline eldspars (orthoclase and microcline perthites) + plagioclase+ biotite± pyroxene, muscovite± amphibole± epidote +zircon+ opaque. Field, petrography and geochemical evidences were used to know the genesis of igneous (ortho) or sedimentary (para) of these gneisses. All the evidences imply an igneous origin (ortho) for the studied gneisses. In fact, the protolith of these gneisses are porphyritic granite to monzonite rocks and has calcareous-alkaline and peraluminous nature. It can be inferred that the protolith of these rocks which formed in the late Neoproterozoic, belong to the calc-alkaline magmas in active continental margins or volcanic arcs (VAG). Further tectonic events have transformed them into gneisses.
Petrology
Ayoub Veisinia; Mohammad Ebrahimi; Bahman Rahibzadeh; rasoul Esmaeili
Abstract
Kamyaran ophiolitic complex located in the northeast Zagros orogeny along the crush zone between Arabian-Iranian plates. This complex outcropped between the Harsin ophiolites in southeast and Sarwabad ophiolite in northwest. Field observation reveal the fact that the Garmab Ophiolite in the northeast ...
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Kamyaran ophiolitic complex located in the northeast Zagros orogeny along the crush zone between Arabian-Iranian plates. This complex outcropped between the Harsin ophiolites in southeast and Sarwabad ophiolite in northwest. Field observation reveal the fact that the Garmab Ophiolite in the northeast of Kamyaran is a tectonic mélange including peridotites and gabbros cut by microgabbroic dikes. Olivine, clinopyroxene and orthopyroxene with chromian spinel made the peridotites minerals with mesh and porphyroclastic fabrics and Gabbros include plagioclase, clinopyroxene and minor amphibole with intergranular, pegmatoidic and interstitial texture. According to the geochemical results, gabbros have tholeiitic to calk-alkaline nature and show the MORB to island arc characteristics. According to the geochemical and geotectonic results, Garmab peridotites plotted to the abyssal peridotites area that represent from the residual mantle spinel lherzolite after extraction of 15–20% partial melting. The break-off of Neo-Tethyan slab and subduction of this slab branch beneath the oceanic lithosphere during cretaceous led to cessation of the Neo-Tethyan subduction beneath the Sanandaj-Sirjan block, and forming arc-back arc basin (second step of subduction) and related rocks in the Kamyaran ophiolite. Presence of tholeiitic to calc-alkaline magmatism is in response to the slab retreat in the Eurasian continental margin.
Petrology
hojjat hajhassani; Jalil Ghalamghash; Mansour Vousoughi Abedini; Rahim Dabiri; Hamideh Rashid
Abstract
The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite- muscovite granites with alkaline and peraluminous affinities. They ...
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The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite- muscovite granites with alkaline and peraluminous affinities. They show enrichments of LREEs relative to HREEs and LILE relative to HFSE with negative anomalies in Nb, Ta and Ti, in normalized trace element diagrams. The leucocratic granite of the Alvand batholith resemble A-type and can be further classified in two of A and A' types granite. The trace elements content of A-type is much higher than A'-type granite. Based on geochemical data, it seems that A- and A'-type granites were generated from partial melting of mantle source. As mantle magma ascends, fractionate and empalce into the crust, A-type leucocratic are formed with minimal contamination and A'-type leucocratic with significant contaminant with continent crust are formed. Field and geochronology data suggest that the leucocratic granite were generated in the late Jurassic, which is contemporaneous with the subduction of the Neo-Tethys oceanic crust beneath the central Iran. It seems that the leucocratic granites were emplaced during a local extensional phase as dykes and small bodies in the Alvand batholith.
Economic Geology
afshin akbarpour; Masoud Moslehi
Abstract
Yapal iron ore body is located in northwest of Sanandaj-Sirjan zone. A complex of Paleozoic metamorphed rocks including green schist, mica schist, chlorite schist with green schist facies degree, plus skarn and marble outcrop in this area.. Iron mineralization generally occurs as magnetite with the shapes ...
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Yapal iron ore body is located in northwest of Sanandaj-Sirjan zone. A complex of Paleozoic metamorphed rocks including green schist, mica schist, chlorite schist with green schist facies degree, plus skarn and marble outcrop in this area.. Iron mineralization generally occurs as magnetite with the shapes of lentoid, veins, veinlets and dots in garnet schist and greenschist and near marble outcrop in area. Ore textures are observed as dispersed, stock, replacement and network like. The iron oxide grade varies between 30 to 60 percent. Iron element negatively correlates with sulfur and positively correlates with titanium, magnesium, manganese and the other main oxides. Based on the relation between cobalt and nickel, this ore body is located within hydrothermal-originated category. Some samples are located in the hydrothermal-volcanogenic boundary. Based on distribution patterns of rare earth elements, Yapal iron ore has more similarities with skarn type mineralizations. Geochemical evidences of magnetite and the variations of cobalt, nickel, silica and aluminum suggest the skarn origin for Yapal iron ore. That means the iron has been mobilized by the hot fluids originated by intrusive stocks and precipitated in contact of metamorphic and marble units.
Petrology
Mahboobeh Jamshidibadr; Narges Sadat Faramarzi
Abstract
Hormuz Island, a salt diapir in southern Iran, mostly composed from evaporite-carbonate sediments of Neoproterozoic. So far, no significant studies have been done belong to the petrography and geochemistry of the Hormuz evaporite-carbonate sediments. Moreover, Salt movements made it difficult to distinguish ...
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Hormuz Island, a salt diapir in southern Iran, mostly composed from evaporite-carbonate sediments of Neoproterozoic. So far, no significant studies have been done belong to the petrography and geochemistry of the Hormuz evaporite-carbonate sediments. Moreover, Salt movements made it difficult to distinguish rocks relationship only based on field observations. In the recent study, with the understanding of field evidences (e.g. the salt thickness, type and amounts of enclaves, as well as field relationship between evaporite unit and volcanic rocks), mineralogical studies (such as studying fluid inclusions within evaporite unit, studying enclaves from evaporite-carbonate unit as well as the mineralogy of dolomite, pyrite and rhyolitic tuffs) and doing geochemical analysis (e.g. Inductively coupled plasma- mass spectrometry and Scanning Electron Microscope), not only the evaporite-carbonate sediments, but also the reconstruction of the events occurring in the Hormuz sedimentary basin, have been investigated. The existence of evaporites with different thicknesses, enclaves and interlayers indicate that deposition of evaporites occurred in two separate stages. The island’s rhyolitic volcanism happened in the gap between sedimentation of lower and upper evaporite units. The volcanoclastic rocks are coexistence with deposition of upper evaporite unit. The deposition of both evaporite units occurred during the upper Ediacaran.
Sedimentology
Javad Anjerdi; Mahdi Jafarzadeh; Adel Najafzadeh; Rahim Mahari
Abstract
In this research, a combination of petrography, geochemistry and heavy minerals analysis methods are implemented for investigating the provenance of quartzarenitic and subarkosic sandstones of Ilanqareh Formation with Late Devonian age in Azerbaijan, south of Jolfa. Investigation of the quartz types ...
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In this research, a combination of petrography, geochemistry and heavy minerals analysis methods are implemented for investigating the provenance of quartzarenitic and subarkosic sandstones of Ilanqareh Formation with Late Devonian age in Azerbaijan, south of Jolfa. Investigation of the quartz types in the studied sandstones, geochemical characteristics of sandstones and shales of Ilanqareh Formation including Al2O3/TiO2 ratio and La/Sc against Co/Th ratios, illustrates that the dominant parent rocks of most of these deposits are granitic igneous ones. The presence of granitic parent rock along with the presence of euhedral zircon and tourmaline among the well-rounded indicate the erosion of uplifted blocks of Iranian basement in the rifted basin of Paleotethys as effective factor in providing sediments. However, geochemistry and heavy mineral assemblages confirm the recycling of sediments from older formations as another source of sediment. The petrography, geochemistry and heavy minerals also indicate the craton provenance and passive margin tectonic setting at the deposition time of the Ilanqareh sediments. According to the present study, one can consider a combination of uplifted source rock (Cadomian basement) and sedimentary recycling of older formations as main sources and Arabian craton as a subsidiary source in the supply of detritus sanstones of Ilanqareh Formation.
Economic Geology
Sanaz Ahmadi; Mohammad Ali Salehi; H Jamali
Abstract
The Hassan Abad Zn-Pb deposits is located in the northeast of Isfahan, Central Iran zone. The host rock of this mineralization is the dolomite of Middle Triassic Shotori Formation. Mineralization included galena, sphalerite, sulfosalts, pyrite and barite which associated with dolomitization. Based on ...
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The Hassan Abad Zn-Pb deposits is located in the northeast of Isfahan, Central Iran zone. The host rock of this mineralization is the dolomite of Middle Triassic Shotori Formation. Mineralization included galena, sphalerite, sulfosalts, pyrite and barite which associated with dolomitization. Based on petrographic studies six types of dolomites (in terms of shape and size of the crystals, the distribution of crystal size and shape of the border crystal) has been identified, that including very fine, medium, coarsely crystalline dolomite, Saddle dolomites and filling pore spaces and veins. The first and second type of dolomites were formed as synsedimentary or diagenetic dolomite with sabkha origin. The third type of dolomite in the late stages of diagenesis was formed in shallow burial conditions due to recrystallization of small crystalline dolomite. Coarse-grained and saddle dolomites have been created under the conditions of deep burial and as hydrothermal dolomites and are related to mineralization. Move over, the origin of magnesium for fine crystalline dolomites were seawater, and for coarse crystalline dolomites are probably the brine fluids of the compacted Sorkh Shale Formation and hydrothermal fluid.
Economic Geology
Z. Zandi; A. R. Jafari rad; A. Gourabjeripour; M. Lotfi
Abstract
The Saheb Fe-Cu skarn deposit is located in the Sanandaj-Sirjan metamorphic belt, SE Saqqez, western Iran and has been formed along the contact between the Oligo-Miocene aged Saheb granitoid and the Permian aged impure calcareous rocks and includes endoskarn and exoskarn. Exoskarn is widely developed ...
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The Saheb Fe-Cu skarn deposit is located in the Sanandaj-Sirjan metamorphic belt, SE Saqqez, western Iran and has been formed along the contact between the Oligo-Miocene aged Saheb granitoid and the Permian aged impure calcareous rocks and includes endoskarn and exoskarn. Exoskarn is widely developed and include garnet and epidote skarn zones. The majority of mineralized zones are concentrated in garnet skarn. The relatively oxidizing mineralogical assemblage of the Saheb skarn includes garnet (andradite-grossular), pyroxene (diopside-hedenbergite), magnetite and hematite. Magnetite is the main and abundant ore mineral throughout the ore deposit. Based on field evidences and microscopic studies of skarn zone samples, two stages of prograde and retrograde alteration are distinguishable. According to the results of sample analysis of Saheb skarn productive intrusive body by XRF and ICP-MS techniques, the combination of this body is chiefly granite to granodiorite-diorite and belong to the I-type granitoids, metaluminous and K-rich calc-alkaline series. The Saheb granitoid is related to the VAG (Volcanic Arc Granite) tectonic setting.
Economic Geology
Maryam Honarmand; Ghasem Nabatian; Mahtab Aflaki; Mohammad Ebrahimi
Abstract
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 ...
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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.
Economic Geology
faraj fardoost; Akbar Abdollahi Hydarbaghi; Solmaz Baluchi
Abstract
The Robaei Iron deposit is located in 96km south of Damghan. Host rocks of deposit are Late Cretaceous limestones (part I) and Eocene volcano- sedimentary rocks including sandy tuff (part II.( The alterations include chloritization, epidotization, argillation, silicification, carbonatization and hematitization. ...
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The Robaei Iron deposit is located in 96km south of Damghan. Host rocks of deposit are Late Cretaceous limestones (part I) and Eocene volcano- sedimentary rocks including sandy tuff (part II.( The alterations include chloritization, epidotization, argillation, silicification, carbonatization and hematitization. Minerals forming can be divided into three groups; iron minerals (hematite, magnetite, pyrite, pyrrotite goethite and limonite), copper- minerals (chalcopyrite, chalcocite, covellite and malachite) and gangue minerals (calcite, dolomite, quartz, garnet, epidote and chlorite). The structure and textures of ore minerals are massive, vein- veinlet, open space filling and disseminated. In part I, the metals grade of Fet is about 60%, Cu 0.7 % and Au 2.7 ppm and in the part II, the Fet are variables between 5.88 to 82.91% (average 31.2%), Cu between 275 to 20761 ppm and Au 0.89 ppm. Fluid inclusion studies were carried out on quartz mineral from the part II that homogenization temperature is frequency variables between 200 to 249°C with salinity of 2-4% wt. %NaCl. Based on the results of this investigation, part I has similarities with calcic skarn of low temperature and part II showed more similarities with iron oxide- copper- gold (IOCG) deposits.
Petrology
Mahnoush Bahjati; A. Ahmadi; Habib Biabangard
Abstract
The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline ...
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The volcanic rocks of Kuleh sangi-Malek siah kuh igneous complex consist of alkalibasalt, basalt, basaltic andesite, andesite, dacite and trachyte. In the SiO2 versus K2O diagram, the basaltic samples are plotted in the shoshonitic field and the subalkaline samples are plotted in the medium K calc alkaline series field. The average La/Yb, Rb/Zr and Cs/Hf ratios in basalts are 7, 47 and 63 times those of N-MORB, respectively. Considerable enrichment of LILEs, LREEs and relative depletion of HREEs indicate that the magmas originated from a mantle source more enriched than that of OIB, where phlogopite and garnet are stable. Using non-modal batch melting model, the compositions of the mafic samples are mainly consistent with about 5% melting of a phlogopite-bearing and garnet-bearing lherzolite with a mixture of about 80% and 20%, respectively. AFC models using Pb versus Ce/Pb and Rb versus K/Rb, show that the fractionated samples have undergone simultaneous crustal assimilation and fractional crystallization. It seems that the assimilation and the fractionation had been taken place with the same rate. Depletion in Y and elevated ratio of Sr/Y of fractionated rocks in addition to Rb/Nb ratio more than 8, could be considered as evidence for crustal assimilation.
Sedimentology
Yazdan Golestan; Umid Kakemem; Mohammad Adabi; E. Dehyadegari
Abstract
Carbonate-evaporate succession with siliciclastic sediments and mixed siliciclastic carbonate deposits of Asmari-Pabdeh reservoir in Karanj Oil Field with Oligo-Miocene in age was studied to determine diagenesis, microfacies and original carbonate mineralogy. Micritization, dissolution, compaction, neomorphism, ...
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Carbonate-evaporate succession with siliciclastic sediments and mixed siliciclastic carbonate deposits of Asmari-Pabdeh reservoir in Karanj Oil Field with Oligo-Miocene in age was studied to determine diagenesis, microfacies and original carbonate mineralogy. Micritization, dissolution, compaction, neomorphism, cementation and dolomitization are the main diagenesis processes that effect Asmari-Pabdeh successions. Petrographic studies led to identification of three types of dolomite such as dolomicrite, dolomicrosparite and dolosparite, in which dolomicrosparite and particulary dolospatite caused increase in reservoir quality. Eleven carbonate-evaporate microfacies were identified. These deposited in four major environments comprises of tidal flat, lagoon, carbonate shoal and open marine. Sedimentary environment of the Asmari Formation recognized as a homoclinal ramp. Diagenetic studies reveal impact of marine, meteoric and burial diagenesis on the deposits. Geochemistry of minor and major elements reveal original aragonite mineralogy for carbonates of the Asmari Formation. The high Sr/Mn and Sr/Ca and minor amounts of manganese implying close diagenetic system with low Water/Rock interaction for the Asmari Formation succession.
Economic Geology
yegane khoramtash; farajolah fardoost
Abstract
The Saghari copper deposit is located 120 Km at Southwest of shahrood, within in the eastern part of Toroud-Chahshirin magmatic arc. Mineralization in the Saghari area occured within volcanic and pyroclastic units of Eocene. Based on the field, laboratory investigations and geochemical analysis, the ...
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The Saghari copper deposit is located 120 Km at Southwest of shahrood, within in the eastern part of Toroud-Chahshirin magmatic arc. Mineralization in the Saghari area occured within volcanic and pyroclastic units of Eocene. Based on the field, laboratory investigations and geochemical analysis, the outcropped rocks in the Saghari deposit are andesite, andesite-basalt, basalt, dacite and several exposures of pyroclastic rocks such as tuff and agglomerate. The rocks are high-k, calc-alkaline to a small amount of shoshonitic in nature, and are formed at a magmatic arc setting in a subduction zone. Basic to intermediate dyke bodies intruded Eocene volcanic-pyroclastic sequences. The host rocks have been affected by argillitic, sericitization, chloritzation, carbonatization and oxide-Fe (limonite, hematite and goethite). The textures and structures of mineralization are vein-veinlet, replacement, open space filling and disminated. According to the mineralography studies, main minerals of copper are malachite, chalcocite, covellite, chalcopyrite, chrysocolla and rare native copper. Malachite and chalcosite are the most abundant minerals. Geochemical studies indicate that copper has a relative correlation with silver.also based on studies of fluid inclusion, the depth of the ore, formation temperature and salinity are 100-200 meter, 100-140 °c and 5-15 WtNaCl%. Copper mineralization in the Saghari deposite has similarities in mineralogy, host rock, texture, structure and geometry with manto-type and volcanic red bed copper deposits.
Economic Geology
Fardin mousivand; Fayeq Hashemi; Mehdi Rezaei-Kahkhaei; Amir Pakizeh
Abstract
The Darreh Amrood Pb (Ag) deposit is located in south of Ghohrood, in the Urumieh-Dokhtar magmatic arc (UDMA). Host rockes to the deposit are Middle to Late Eocene grey-green siliceous tuff and crystal lithic tuff. Geometry of orebodies is stratabound, irregular, and semiconcordant to discordant to layering ...
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The Darreh Amrood Pb (Ag) deposit is located in south of Ghohrood, in the Urumieh-Dokhtar magmatic arc (UDMA). Host rockes to the deposit are Middle to Late Eocene grey-green siliceous tuff and crystal lithic tuff. Geometry of orebodies is stratabound, irregular, and semiconcordant to discordant to layering of the host rocks. Ore structures and textures are dominated by semi-massive to brecciated, banded and vein-veinlets. Main primary minerals are galena, pyrite and chalcopyrite, and secondary minerals are dominated by covelline, goethite and hematite. Gangue minerals are epidote, chlorite, sericite, clay minerals, quartz, calcite and barite. Wall rock alterations are dominated by epidote-chlorite and sericitic. The rare earth element (REE) pattern of ores is not similar to that of volcanic rocks in the footwall and hangingwall that is concordant with sub-seafloor replacement process for ore formation. Also Ce showed negative anomaly that can be attributed to Ce in the seawater. Also based on structural, stratigraphic, petrographic, textures, mineralogical, alteration and geochemical studies, it is inferred that the Pb (Ag) mineralization in the Darreh Amrood area occurred as bimodal felsic- or Kuroko-type volcanogenic massive sulfide (VMS) mineralization, and formed as sub-seafloor replacement. It should be noted that the Darreh Amrood deposit is the first recognition of base metal-rich and poor barite VMS mineralization in the UDMA.
Petrology
Siavash Omidianfar; mohammad rahgoshay; Iman Monsef
Abstract
Koudakan Granitoid located in 100 km South of Birjand and 18 km North of Ghaleh-Zari mine in eastern Iran. It belong to the Lut Block volcanic–plutonic belt. These intrusive rocks (Eocene-Oligocene) petrogaphicaly composed of Diorite, Monzodiorite, Quartzmonzodiorite, Tonalite, Porphyritic Tonalite, ...
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Koudakan Granitoid located in 100 km South of Birjand and 18 km North of Ghaleh-Zari mine in eastern Iran. It belong to the Lut Block volcanic–plutonic belt. These intrusive rocks (Eocene-Oligocene) petrogaphicaly composed of Diorite, Monzodiorite, Quartzmonzodiorite, Tonalite, Porphyritic Tonalite, Granodiorite, Granite and Porphyritic Granite. Plutonic rocks in this area have features typical of high-K calc-alkaline to shoshonite series, metaluminous and belong to I-type Granitoides. Enrichment in LILE rather than HFSE (RbN/YN: 38.12-124.93), negative anomalies of Nb and Ti and enrichment in LREE rather than HREE (LaN/YbN: 6.74-12.03) in all of samples are important evidences for the formation of this rocks in a subduction related magmatic belt. Positive anomalies of Pb and K indicate the involvement of continental crust in evolution of parental magma. Parallel trend of the samples in spider diagrams show that they are co-genetic. Elements ratios and Different discrimination diagrams show the formation of this rocks in an active continental margin with about less than 45 Km crustal thickness in per-collision steps. Parental magma has been generated by low degree partial melting (less than 5%) of an enriched peridotite in mantle wedge (Spinel lherzolite.).
Economic Geology
Hossein Abasnia; M. H. Karimpour; Azadeh Malekzadeh Shafaroudi
Abstract
Damanghor area is located northern Bardaskan, Khorasan Razavi province, and structurally, it is a part of Taknar zone. Geology of the area includes of Taknar metamorphosed sedimentary rocks and metarhyolite, which is intruded by diabasic rocks as stoke and dyke. The texture of metarhyolies is porphyry ...
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Damanghor area is located northern Bardaskan, Khorasan Razavi province, and structurally, it is a part of Taknar zone. Geology of the area includes of Taknar metamorphosed sedimentary rocks and metarhyolite, which is intruded by diabasic rocks as stoke and dyke. The texture of metarhyolies is porphyry and contains of quartz and feldspar, whereas diabas has ophitic texture and contain plagioclas, pyroxene, and hornblend. Age of metarhyolite and diabas determined 550 Ma (Neoprotrozoic) and 8.8 Ma (Miocene), respectively, using zircon U-Pb method. Metarhyolites have peraluminous nature and were formed at intracontinental rift. Low enrichment in LREE relative to HREE and Eu negative anomaly indicates the magma is formed at plagioclase stability depth. (87Sr/86Sr)i (0.700712), (143Nd/144Nd)i (0.511852), and εNdi (–1.51) values show source of magma was mantel or lower crust. Diabases have toleitic to metaaluminous nature and were formed at subduction zone. (87Sr/86Sr)i (0.710527), (143Nd/144Nd)i (0.512716), and εNdi (+1.7) values indicate magma is drived from partial melting of metasomatized mantle wedge by released fluid of subducted slab, which is assimilated with continental crust. Taknar formation acidic Neoprotrozoic magmatism, which is formed at rift setting, associated with Miocene basic magmatism, which is formed at subduction zone, reveals an insight of tectonomagmatic conditions of Taknar zone in different times.
Razieh Rezaei Hamid; Ebrahim Tale Fazel; Shojaedin Niroomand
Abstract
The Baharieh copper deposit with 1 Mt Cu ore, is located in 30 km of NE Kashmar city and it’s belong to Sabzevar zone and Taknar metallogenic area. The copper mineralization as stratabound and 200m length with east-west trending which occurs in porphyric andesitic tuff (middle Eocene). Volcanic ...
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The Baharieh copper deposit with 1 Mt Cu ore, is located in 30 km of NE Kashmar city and it’s belong to Sabzevar zone and Taknar metallogenic area. The copper mineralization as stratabound and 200m length with east-west trending which occurs in porphyric andesitic tuff (middle Eocene). Volcanic to subvolcanic rocks are composed of andesite, dacite and rhyolite and shows calc-alkaline to shoshonitic affinities. According to geochemistry of immobile trace elements (e.g., La, Yb and Zr), the igneous rocks straddle within active continent margin arcs. The vein minerals consist of main sulfide minerals such as chalcopyrite and pyrite, which accompanied with bornite, covelline, and chalcocite. Silicic, calcitic, chloritic and argillic are the main alteration assemblage with mineralization. Two types of fluid inclusions including of liquid-rich (LV-type) and vapor-rich (VL-type) are distinguished in quartz-ore stage of the Baharieh deposit. Homogenization temperature and salinity are recorded varies from 187 to 356°C and 0.99 to 18.7 wt% NaCl eq. Some characteristic as vein, breccia and vuggy textures, volcanic host rocks, low temperature alteration, simple ore minerals and high chalcopyrite content, temperature and salinity of fluids and the other evidences shows Baharieh copper deposit is similar to in Cu (Ag) manto-type (volcanic red bed) deposit at Chile.
