Economic Geology
Shaghayegh Sadat Hashempour; Sajjad Maghfouri; Ebrahim Rastad
Abstract
The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern ...
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The Goft and Mohammadabad manganese deposits are located in the southwestern part of Sabzevar, whitin the Late Cretaceous volcano-sedimentary sequences. This sequence is located inside a 100 km long folded structure with northeast-southwest trend. Mohammadabad manganese deposit located in the southeastern edge of the southern anticline in the unit 4 of regional stratigraphic column and Goft manganese deposit is occurred in the southeastern edge of the northern anticline in the first unit of the regional stratigraphic column. The host rocks of Goft and Mohammadabad deposits include red tuff and Marly tuff and limy tuff, respectively. According to geochemical studies, tectonic environment of manganese deposits in the southwest of Sabzevar is a rifting environment that has been formed in the Sabzevar back-arc basin. The rocks of the region have a wide range of basalt, rhyolite, dacite, olivine-basalt, andesite-basalt and trachy-andesite, which formed aligned with pyroclastic sediment and Late Cretaceous sedimentary units. Dacite rocks are the thickest felsic rock unit in the area. The values of major oxides, the pattern of rare earth elements (REE), and the changes in trace elements in spider diagrams indicate the bimodal and tholeiitic nature of the volcanic rocks of the region, which are deposited in extension environment with a mixed range from basalt to rhyolite.
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.
Tectonics
Firouzeh Shavvakhi; Saeed Madanipour; Ebrahim Rastad
Abstract
South Natanz Area is structurally located in the western part of the Central Iranian structural zone and central part of the Orumieh-Dokhtar magmatic belt at southwestern termination of the Qom-Zefreh Fault. Our structural data represents older generation of E-W to NW-SE thrust faults as Fasakhod Fault ...
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South Natanz Area is structurally located in the western part of the Central Iranian structural zone and central part of the Orumieh-Dokhtar magmatic belt at southwestern termination of the Qom-Zefreh Fault. Our structural data represents older generation of E-W to NW-SE thrust faults as Fasakhod Fault that juxtaposes Permian- Triassic (Jamal, Nayband and Shotori Formations) over younger rock units. Most of the thrust faults have been cross cut with younger generation of strike-slip fault system. These mainly post Eoene strike slip fault systems are structurally linke to Qom-Zefreh Fault zone. On the other hand, they developed as strike slip orders of the Qom-Zefreh Fault system in central part of the Orumieh-Dokhtar magmatic belt. Integration of the structural data set with stratigraphic unconformities observed in the south Natanz represet regional folding of the area during pre Early Cretaceous time. Subsequently, it has experienced regional extension as observed in the other parts of the central Iran during Early Cretaceous time. Major thrust faulting of the area has been occuered during post Late Createcous time. The final post Oligocene strike slip faulting related to the activation of the Qom- Zefreh fault has overprinted and cross cut older structural features.
Economic Geology
Mohammad Jafar Kupayi; Ebrahim Rastad; Saeed Madanipour; Sajjad Maghfouri
Abstract
Cretaceous sedimentary sequence in the Yazdan area is consisting of four rock units as, from the old to the new, clastic-carbonate (Kc), carbonate (Kl), Shale and marl (Km) sequences, and Sandy limestone and sandstone (Kls). The Kls unit is host of ore mineralization in the study area and formed from ...
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Cretaceous sedimentary sequence in the Yazdan area is consisting of four rock units as, from the old to the new, clastic-carbonate (Kc), carbonate (Kl), Shale and marl (Km) sequences, and Sandy limestone and sandstone (Kls). The Kls unit is host of ore mineralization in the study area and formed from four members. Ore mineralization in the Yazdan Deposit has occurred as a stratiform horizon in the sandstone units of the third member. Texture and structures studies, shown three ore facies with elemental zonation in the Yazdan Deposit. These ore facies includes, stringer zone, massive ore facies and the bedded ore facies. This ore facies formed from laminated and layered sulfide and sulfate minerals. Fluid inclusions studies represents 255-136 ° C of homogeneity temperature with an average temperature of 189 ° C. Also, the salinity of fluid inclusions was calculated to be between 14.6-6% NaCl (on average, 9.5% NaCl). Geological evidence, host rocks type, texture and structures, existence of ore facies with elemental zoning as well as fluid inclusion investigations indicate the Yazdan Deposit has most similarity with Sedex-type deposit.
Economic Geology
Zahra Kaboodi; Majid Ghaderi; Ebrahim Rastad
Abstract
The Kahak copper deposit occurs in the Eocene volcano-sedimentary sequence of Qom region, Urumieh-Dokhtar magmatic arc. The oldest rock unit in this sequence is a crystal tuff, overlain by tuff, andesite, sandstone, conglomerate, and limestone. Host rocks to the Kahak deposit include andesite and tuff, ...
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The Kahak copper deposit occurs in the Eocene volcano-sedimentary sequence of Qom region, Urumieh-Dokhtar magmatic arc. The oldest rock unit in this sequence is a crystal tuff, overlain by tuff, andesite, sandstone, conglomerate, and limestone. Host rocks to the Kahak deposit include andesite and tuff, and the geometry of mineralization is stratabound. Mineralographical studies show that the ore minerals are pyrite, chalcopyrite, chalcocite, native copper, bornite, galena, covellite, digenite, and malachite accompanied by magnetite, and hematite. Based on mineralogical studies, two types of alteration are recognized in the volcanic rocks of the area, general alteration, and ore mineral alteration. The propylitic alteration is an indication of general alteration. The main alteration types in the mineralized zone of the deposit include carbonatization, silicification, chloritization, epidotization, and zeolitic. Dissemination, open space filling, vein-veinlet, pseudo-lamination, and replacement are the major textures and structures of the ore minerals at Kahak. Two major stages are distinguished for mineralization at the Kahak deposit. The first stage is volcanism and pyrite formation in the host rocks (andesite and tuff), producing reduction state. The second stage involves diagenesis and entering Cu-rich oxidant fluids replacing Cu for Fe in the pyrite and forming Cu-sulfides and hematite and mineralization. The Kahak copper deposit shows high similarities in geometry, host rock, mineralogy, texture and structure and genetic model with the Manto-type copper deposits worldwide.
Economic Geology
H Tajeddin; Ebrahim Rastad; Abdolmajid Yaghoubpour; Mohammad Mohajjel; Richard Goldfarb
Abstract
Barika gold (and silver)-rich volcanogenic massive sulfide deposit is located 18 km east of Sardasht city in the northwestern of Sanandaj–Sirjan metamorphic Zone. The rocks in the vicinity of the Barika deposit predominantly consist of Cretaceous volcanosedimentary sequences of phyllite, slate, ...
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Barika gold (and silver)-rich volcanogenic massive sulfide deposit is located 18 km east of Sardasht city in the northwestern of Sanandaj–Sirjan metamorphic Zone. The rocks in the vicinity of the Barika deposit predominantly consist of Cretaceous volcanosedimentary sequences of phyllite, slate, andesite and tuffite, metamorphosed under greenschist facies grade. Barika deposit is composed of stratiform ore and stringer zone that both are hosted in an altered and sheared metaandesite unit. Fluid inclusion studies indicated that quartz (stringer zone) and barite (stratiform ore) samples homogenized between 132° and 283°C. Salinities of the fluids inclusions show a range from 1.4 to 9.6% wt NaCl equivalent that are close to that of normal seawater. The study indicates the colling occurred in the initial ore fluids, as a result of mixing with sea water, is an important process in the formation of Barika deposit. The δ34S values of sulfide minerals (pyrite, sphalerite and galena) from stockwork mineralization in the Barika deposit range from -0.8 to +5.6 per mil and fall within the range of values observed for volcanogenic massive sulfide deposits. The narrow range of measured δ34S values from the sulfide minerals suggests that similar to almost of Kuroko VMS deposits, the ore-forming sulfur derived from the leaching of igneous sulfur from the underlying andesitic rocks. Calculated sulfur isotope temperatures for twelve coexisting galena-sphalerite and galena-pyrite pairs range from 146-293 ْ C that is consistent with temperatures estimated from fluid inclusion studies.
Economic Geology
Pouria Mahmoodi; Ebrahim Rastad; Abdorrahman Rajabi; Mehran Moradpour
Abstract
The Early Cretaceous Eastern Haft-Savaran Zn-Pb (Ba) deposit situated in the Arak mining district and occurred within the extentional back-arc of Malayer-Esfahan basin. Mineralization occurred in two horizons in the Estern Haft-Savaran deposit. First horizon is major horizon that formed within the most ...
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The Early Cretaceous Eastern Haft-Savaran Zn-Pb (Ba) deposit situated in the Arak mining district and occurred within the extentional back-arc of Malayer-Esfahan basin. Mineralization occurred in two horizons in the Estern Haft-Savaran deposit. First horizon is major horizon that formed within the most upper portion of the massive limestone and second horizon occurred in the thin limestone which is alternate with shale and marl. Textures of the mineralization in this deposit are replacement, massive and vein- veinlets, and main alterations are silisification, dolomitization and calcitization. Sphalerite, galena, chalcopyrite, tetrahedryte, pyrite, bornite, chalcosite and covelite are the sulfide minerals and quartz, calcite, dolomite and sericite are gangue minerals in the ore deposit. Cathodoluminescence study in this deposit indicates three dolomites and one calcite generations. First generation of dolomite associated with weak mineralization and second generation of dolomite is Fe-rich and associated with main mineralization. Third generation of dolomite is late dolomitization and formed with calcite and cross-cutted the mineralization. Presence of framboidal pyrite with galena and sphalerite in its matrix and fine-grain euhedral barite suggest mineralization began during sedimentation and early diagenesis stage near seafloor. In continuum, main ore is identified as replacement occurrence of first generation sulfides by second generation coarse-grained sulfides under seafloor. With regarding to the formation of the Eastern Haft-Savaran deposit in the extentional tectonic setting, massive limestone as the host rock, and mineralization formation as replacment during diagenesis of the host rock under the seafloor, this deposit would be classified as Irish type deposit.
Economic Geology
M. Movahednia; E. Rastad; A. Rajabi; F. Choulet
Abstract
The Ab-Bagh Zn-Pb deposit is located in the central part of the Sanandaj-Sirjan zone (SSZ) and at the southeastern part of the Malayer-Esfahan metallogenic belt. This deposit is hosted by Upper Jurassic-Lower Cretaceous sedimentary sequence. Zinc and lead mineralization occurred within two horizons. ...
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The Ab-Bagh Zn-Pb deposit is located in the central part of the Sanandaj-Sirjan zone (SSZ) and at the southeastern part of the Malayer-Esfahan metallogenic belt. This deposit is hosted by Upper Jurassic-Lower Cretaceous sedimentary sequence. Zinc and lead mineralization occurred within two horizons. The ore horizon 1 is hosted by Late Jurassic-Early Cretaceous black shale and siltstone. The ore body displays a wedge-like shape and is located close to syn-sedimentary fault. The ore horizon 2 occurs in lower Cretaceous carbonates and includes a massive ore facies that is concordant with host rock layering. It is also underlain by a stockwork facies. Weathering processes led to a supergene ore stage at Ab-Bagh deposit in parts toward the surface. Based on geology, mineralogy and geochemistry, two types of non-sulfide ore were distinguished: the white ore and the red ore. The white ore is a wall-rock replacement mineralization that contains high Zn, low Fe and a very low concentration of Pb. To the opposite, the red ore formed after the direct replacement of sulfide protore and it typically contains low Zn, high Fe and medium Pb± As concentrations. Supergene ore consists of smithsonite and hydrozincite. Minor cerussite, Zn-rich clays, greenockite, covellite and Fe-Mn oxides were also identified. The supergene part of the Ab-Bagh deposit formed as a consequence of long time weathering of a SEDEX-type sulfide protore. Oxidation of sulfide minerals (mainly pyrite and sphalerite), carbonate buffering reactions and precipitation of secondary Zn-bearing minerals are the main geochemical process involved. The REE patterns of the white non-sulfide ore are similar to that recorded in the host rocks but REE patterns of red ore, is similar to sulfide ore. The comparison with other major non-sulfide Iranian deposits suggests that Ab-Bagh deposit is very similar to Kolahdarvazeh and Mehdiabad deposits; it also shows lots of similarities with other worldwide examples (e.g. Moroccan non-sulfide ore deposits).
S Maghfouri; E Rastad; F Mousivand; Y Lin
Abstract
Copper mineralization in Nudeh Cu deposit and Frezy, Garab, Kalateh lala (Nieran) and Chun occurrences, located in southwest of Sabzevar hosted by a Upper Cretaceous volcano-sedimentary sequence formed in a rift environment. The main is host rock of the Nudeh Cu sulfide deposit includes alkali olivine ...
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Copper mineralization in Nudeh Cu deposit and Frezy, Garab, Kalateh lala (Nieran) and Chun occurrences, located in southwest of Sabzevar hosted by a Upper Cretaceous volcano-sedimentary sequence formed in a rift environment. The main is host rock of the Nudeh Cu sulfide deposit includes alkali olivine basalt flow and subordinate tuffaceous silty sandstone. Host rock of the Ferizy and Garab occurrences is andesite flow. The rock forming mineral of Kalateh lala (Nieran) and Chun occurrences is tuffaceous silty sandstone. Sulfide mineralization in the Nudeh deposit and occurrences within an Upper Cretaceous volcano-sedimentary sequence occurs as sheet-like &tabular shape within three ore horizons. Based on nature of sulfide mineralization, mineralogy and textures of sulfide minerals, the Nudeh deposit can be divided into three different ore facies. Based on their situation towards the vent of mineralizing fluid, these facies include: A) Vein-veinlets facies (Stringer zone) includes sulfide veins and silica that form as a scissors of host rocks under the massive ore facies. Vein-veinlets and replacement textures formed main features of this facies. B) Massive ore facies that forms the thicker part of generally massive higher grade ores in west of the deposit and includes sulfide mineralization with heterogeneous nature and stratabound, limited in the alkali olivine basalt flow. C) Bedded ore facies which is thinner than the massive ore facies and is characterized by layered and banded apparent and low grade ore. The rock forming mineral of this facies is tuffaceous silty sandstone. This facies occurs as laminated and banded sulfides contemporaneous with the host rocks layering at eastern part of the deposit. Mineralogy of Nudeh deposit includes chalcopyrite, pyrite, bornite, sphalerite, boulangerite and magnetite wall rock alterations are dominated by silicification, chloritization, sericitization and epidotization. The most important characteristics of mineralization at the Nudeh deposit such as tectonic setting, host rocks, mineralogy, metal content as well as wall rock alterations, show similarities with volcanogenic massive sulfide (VMS) deposits. Accordingly, Nudeh Cu deposit is regarded as a Besshi - or pelitic mafic VMS deposit.
S Ghaderi; E Rastad; N Rashidnejad-Omran; M Mohajjel
Abstract
Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle ...
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Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle Jurassic volcano-sedimentary sequences, and their distribution is indicated by layering. These deposits are located in a specific stratigraphic position and are concentrated in contact of volcanic units with carbonate rocks. The geodynamic setting of this category probably is intracontinental rifting. The second category contains deposits located in metamorphosed sedimentary rocks of the Shemshak group and Jurassic granitoids. These deposits have vein-veinlet geometry and their formation is controlled by faults, fractures and shear zones. The geodynamic setting of this category probably is active continental margins. The mineral paragenesis of the first group generally contains scheelite and Cu-Fe-Zn sulfides, whereas the paragenesis of the second group is wolframite, scheelite, chalcopyrite, arsenopyrite, with gold and specifically bismuth.
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.
M Boveiri Konari; E Rastad; N Rashidnejad-Omran
Abstract
Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, ...
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Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, which are unconformably overlain by the Lower Cretaceous progressive sequence with basal conglomerate, sandstone and silty shale. Copper (-Ag) mineralization occurred in the Lower Cretaceous pyroclastics and volcanic lava. The host rock is a crystal lithic tuff with trachyandesite-andesite affinity in which the stratabound and lenticular ore body is extended discontinuously over 35 km that laterally and vertically changed into orbitolina limestone. Ore minerals include chalcocite, bornite, native copper, digenite, chalcopyrite, pyrite, Ag-bearing clausthalite, covellite, anilite, malachite and azurite. Ore textures and structures are open space filling, vein-veinlet, replacement, disseminated and laminated-like. The lithogeochemical studies in 6 lithostratigraphic profiles from NW to SE of Safashahr indicated Cu (-Ag) mineralization occurrence in a specific stratigraphic unit and a positive relationship with Zn. The lithological, mineralogical, lithogeochemical and microscopic investigations revealed that mineralization initially occurred contemporaneously with volcanism in volcano-sedimentary sequences (absorption of Cu by ferric hydroxide, clay minerals and replacement in feldspar lattice) and then in burial diagenesis during dehydration of pyroclastic and detrital units and alteration resulting from this hydrothermal fluid, Cu released and transported by hydrothermal diagenesis fluids. When this ore-bearing hydrothermal fluid received by the rock unit with high permeability (pyrite-bearing crystal lithic tuff) and reduced conditions resulted from abundance of pyite, replaced them as copper sulphide minerals. S isotopic data of sulphidic minerals indicated that the bacterially sulfate reduction of sea water as an important role provided the nessecary sulfur for sulfide mineralization. Geochemical features of volcanic and pyroclastic units indicated that they formed in an intra-arc rift. On the basis of this study and with respect to some evidences such as tectonic setting, host rock, lenticular shape of the ore body, structure and texture as well as mineral paragenesis we suggest that Keshtmahaki Cu (-Ag) mineralization and surrounding occurrences are Volcanic Red Bed (VRB) type deposit that formed and concentrated contemporaneously with submarine volcanism to deep burial diagenesis processes.
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.
E. Rastad; H. Tajedin; A. Yaghubpur; M. Mohajel
Abstract
The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, ...
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The Barika gold (and silver) rich-massive sulfide deposit is located 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are metamorphosed volcano-sedimentary rocks in green schist facies, and include association of meta-andesit, meta-tuffite, phyllite, and slate rocks. The Barika deposit is metamorphosed to greenschist facies, and underwent Barika shear zone- related deformation. The metamorphism/deformation events have superimposed on the synvolcanic stratiform ore and resulted in a variety of mineralogy and textures. Ore minerals in the deposit were originally composed of pyrite, sphalerite, galena, tetrahedrite- tenantite and stibnite which were deposited during synvolcanogenic hydrothermal activity. Gold probably was occurred as submicroscopic inclusions or invisible gold locked in pyrite and electrum in barite. Prograde metamorphism/deformation obliterated almost the sedimentary textures in the stratiform ore. the regional metamorphism have resulted in the development of granoblastic textures with triple junctions in pyrite which lead to migration of submicroscopic gold to the crystal boundary to form microscopic electrum. Shear zone - related deformation, lead to chemical remobilization of pre-existing mobilizable metallic constituents (e.g., Au, Ag, Pb, Sb, As and Hg) and eventually reconcentrated them as visible electrums associated َwith Ag, As, Sb, Pb, Hg – rich sulfosalt minerals at microfractures and open spaces which have developed during the shearing deformation. Metamorphic/deformation remobilization was important in releasing refractory Au from sulfides and locally concentrating it in a recoverable form (electrum).
H. A. Tajeddin; E. Rastad; A. Yagoubpour; M. Mohajjel
Abstract
Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green ...
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Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green schist facies, and include association of metaandesite, metatuffite, phyllite and slate rocks, among which the metaandesitic unit (KMv1) is host rock of the deposit. Ore mineral assemblages in stratiform part of the deposit, which contain massive and banded pyrite and barite associated with subordinary silica bands, are very variable in composition and consist of pyrite, sphalerite, galena, stibnite and a variety of sulfosalt minerals and electrum. Ore mineral assemblage in silicic veins in stringer zone, are simpler and consist of pyrite, galena, sphalerite, tetrahedrite and rare chalcopyrite. Average gold and silver grades in stratiform ore are 4.2 and 260 g/t respectively and in silica stringer veins are 0.7 and 30 g/t. Base metal content in both part of the deposit is less than 1%. Lithotectonic study and trace and rare earth elements diagrams associated with Ce/Pb and Nb/U ratios of the metavolcanic rocks in the deposit area indicate that the rocks were generated from a lithospheric mantle source in the active continental margin of the SSZ. A geochemical study of Barika deposit reveals that distribution patterns and correlation coefficient of ore elements in parts of the Barika stratiform ore and stringer zone are completely in correlation with an undeformed massive sulfide deposit. The geochemical documents indicate that despite the metamorphism and highly deformation on the deposit, the primary distribution patterns and proportion of the ore elements are well conserved, as geochemical characteristics of the Barika deformed deposit is as well as correlated with an undeformed gold- rich volcanogenic massive sulfide deposit. However there is clear textural evidence for remobilization of As, Sb, Ag and Pb minerals together with Au in Barika deposit, but, remobilized constituents of the ores do not appear to have moved beyond the margins of the ore bodies and primary metal zonation.
F. Mousivand; E. Rastad; M. H. Emami; J. M. Peter; M. Solomon
Abstract
Zn-Pb-Cu mineralization in the Chahgaz area, located 60 km south of Shahre Babak, occurs within a Middle Jurassic metamorphosed bimodal volcano-sedimentary sequence in the South Sanandaj-Sirjan zone. Mineralization occurs associated with exhalites within units 1and 2 of the host sequence as numerous ...
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Zn-Pb-Cu mineralization in the Chahgaz area, located 60 km south of Shahre Babak, occurs within a Middle Jurassic metamorphosed bimodal volcano-sedimentary sequence in the South Sanandaj-Sirjan zone. Mineralization occurs associated with exhalites within units 1and 2 of the host sequence as numerous occurrences, and within unit 3 as Chahgaz deposit and some occurrences hosted by meta-rhyolitic tuff, meta-rhyolite, and meta-pelites, as predominantly stratiform, tabular and sheeted-like orebodies at specific stratigraphic horizons. Ore textures include massive, semi-massive, banded, laminated, disseminated and vein-veinlets. Ore minerals are predominantly pyrite, sphalerite, galena, chalcopyrite, tetrahedrite, arsenopyrite, and minor bornite and pyrrhotite, and gangue minerals include dominantly sericite, quartz, chlorite and barite. Wallrock alteration is dominated by sericitic and chloritic and minor carbonatic and silicic types. Altered host rocks have been foliated due to metamorphism and deformation, and along with the associated ores have been folded and faulted and show cataclastic, triple junctions, pressure shadows, crenulations, and boudinage features. Based on geological, mineralogical, geochemical and alteration studies, it is inferred that Zn-Pb-Cu mineralization in the Chahgaz area has occurred as volcanogenic massive sulfide (VMS)-type in an arc rift basin, and has subsequently been metamorphosed under greenschist facies conditions during the Late Cimmerian and Laramid orogenies and younger events. This mineralization, in comparison with similar deposits in the world, has the most similarities with those deposits of siliciclastic felsic-type in the Bathurst Mining Camp, Canada, and Iberian Pyrite Belt in Spain and Portugal; and it is the first recognition of this type in Iran.
B. Mehri; E. Rastad; F. Fayyazi
Abstract
The Khanjar Pb– Ag (Zn) deposit is one of the stratabound deposits of Cretaceous age in Central Iran. The ore bodies may be grouped into two main geometric types: 1) Lenses of ore bodies congruent with bedding, 2) Ores as open space filling or with brecciate fabric due to faulting. Both types occur ...
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The Khanjar Pb– Ag (Zn) deposit is one of the stratabound deposits of Cretaceous age in Central Iran. The ore bodies may be grouped into two main geometric types: 1) Lenses of ore bodies congruent with bedding, 2) Ores as open space filling or with brecciate fabric due to faulting. Both types occur in limestone unit (k2b).Three ore bearing facies have been distinguished in the Khanjar area: 1) Siliceous limestone facies; galena, sphalerite and pyrite are the main ore minerals. Minor amounts of chalcopyrite are also visible. 2) Mullusca, Echinoderm wackstone facies with galena and sphalerite. 3) Rudist limestone facies with large amount of galena. As with other stratabound and stratiform Pb- Zn deposits, the main ore minerals are simple and few in number. In addition, galena, sphalerite and pyrite, some tetrahedrite, barite and minor amounts of copper minerals are observed. Pyrite often with framboidal texture and sphalerite with spheroidal texture form always part of paragenesis. Fluid inclusion investigations on saddle dolomite located in fractures with galena and sphalerite demonstrated the homogenization temperature of 145-230 centigrade and salinity of 17.5-23% NaCl equivalent.Geometry of ore bodies, occurrence of ore horizons in certain sedimentary facies, ore textures and structures, depositional environment (Lagoonal), paragenetic sequence of minerals and fluid inclusion data, all suggest that Khanjar Pb- Ag(Zn) deposit is an MVT deposit.