Economic Geology
Shohreh Hassanpour; Susan Ebrahimi
Abstract
Astmal deposit is located in the northwest of Iran and is structurally located in the Arasbaran Magmatic zone. Skarn mineralization related to the Eocene-Oligocene granodiorite rocks which have been permeated to the Upper Cretaceous rocks. Mineralization has formed in the exoskarn zone, and the metasomatic ...
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Astmal deposit is located in the northwest of Iran and is structurally located in the Arasbaran Magmatic zone. Skarn mineralization related to the Eocene-Oligocene granodiorite rocks which have been permeated to the Upper Cretaceous rocks. Mineralization has formed in the exoskarn zone, and the metasomatic process has started immediately after the penetration of the granodiorite into the limestone. Significant amounts of Si, Mg, and Fe elements lead to the development of anhydrous calc-silicate minerals with medium to coarse grains, and also significant amounts of Cu, Fe elements along with volatile substances such as CO2, H2S are added to the skarn system. As a result, hydrated calcsilicates (epidote, tremolite, and actinolite), sulfides (pyrite and chalcopyrite), oxides (magnetite and hematite) and carbonates (calcite) have been replaced anhydrous calcsilicates. The results of δ34S isotope analysis on pyrite and chalcopyrite ores are in the range of -1.8 to +6.1 ‰, which indicates the magmatic source of sulfide. Also, the results of δ18O and δD isotope data on magnetite, sericite and epidote minerals, which are in the range of -56 to -73 ‰ for hydrogen and -0.5 to +6.8 ‰ for oxygen, indicate a mixture of magmatic fluids associated to the small amounts of meteoric fluids.
Economic Geology
Mehrdad Movahedi; Mohammad Yazdi; Mehrdad Behzadi
Abstract
The Oshvad skarn type deposit was formed during the intrusion of a felsic mass into the Permian and Triassic carbonate rocks and ion exchange occurred between the intrusion mass and these units. In order to determine the properties of the mineralizing fluid in this skarn, several fluid inclusions in ...
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The Oshvad skarn type deposit was formed during the intrusion of a felsic mass into the Permian and Triassic carbonate rocks and ion exchange occurred between the intrusion mass and these units. In order to determine the properties of the mineralizing fluid in this skarn, several fluid inclusions in quartz and calcite minerals of the mineralization zone were analyzed. The results show that these minerals have two types of fluids inclusion. The first group includes L+V type, low to medium salinity, and with homogenization temperature of 194 to 480°C. The second group includes V+L type, low to moderate salinity, and homogenization temperature of 338 to 448°C. The origin of L+V type fluid inclusions are magmatic-meteoric and metamorphic type and V+L fluid inclusions are metamorphic type. Mixing and dilution of fluids occurred during the mixing of meteoric waters with magmatic-metamorphic fluids. These processes are the main factors of mineralization in this deposit. Fluid inclusions data show that fluid pressure has been 50 to 150 bars during the ore-forming minerals. Also, the fluid temperature has been between 200 to 360°C. The data suggest that the ore minerals have been formed in depth of 650 meters lower than the old water table.
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.
Economic Geology
nasrin khajehmohammadlou; Ali Asghar Calagari; Kamal Siahcheshm; Ali Abedini
Abstract
The Aghbolagh iron-copper skarn is located in ~21 km north of Oshnavieh, southwest of West-Azarbaidjan province. The intrusion of Cretaceous granitic body into the Cambrian Barut, Zagun, and Lalun Formations (carbonate, shale, and sandstone) was accompanied by development of calcic-type skarn, hornfels, ...
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The Aghbolagh iron-copper skarn is located in ~21 km north of Oshnavieh, southwest of West-Azarbaidjan province. The intrusion of Cretaceous granitic body into the Cambrian Barut, Zagun, and Lalun Formations (carbonate, shale, and sandstone) was accompanied by development of calcic-type skarn, hornfels, and marble in the study area. The garnets of the Aghbolagh skarn belong to solid solution series of grossularite-andradite in which andradite is the dominant phase (>80%). These garnets are isotropic and lack zonation. The pattern of REE distribution in these garnets shows the enrichment of LREE relative to HREE and also the occurrence of negative anomalies of Eu/Eu* and Ce/Ce*. The comparison of the distribution pattern of REE in garnets with those in igneous (granite and monzonite) and sedimentary (carbonates and sandstones) rocks demonstrates that the REE in garnets were derived mainly from the igneous rocks rather than the sedimentary units. The increase in Pr/Yb ratios in parallel with increase in the ƩREE is indicative of the magmatic origin of the ore-forming fluids in the Aghbolagh skarn. However, the lack of sensible variations between Ce/CE* and ƩREE values indicate that the meteoric waters might have also played a part in skarn-forming fluids at Aghbolagh.
Remote Sensing
Seyedeh Sakineh Mousavi; Mehdi Honarmand; Hadi Shahriari; Mahdiye hosseinjanizadeh
Abstract
Mineral exploration in Esfandagheh area, located in south east of Kerman province is complicated due to verity of metallic deposits including volcanogenic massive sulfide copper, skarn iron, and volcanic manganese. This research was carried out with the aim of defining a model for mineral exploration ...
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Mineral exploration in Esfandagheh area, located in south east of Kerman province is complicated due to verity of metallic deposits including volcanogenic massive sulfide copper, skarn iron, and volcanic manganese. This research was carried out with the aim of defining a model for mineral exploration and providing mineral potential map using remote sensing data. ASTER and OLI images along with various image processing techniques including color composite of band ratios, principal component analysis (PCA), and QI and SI indices were applied to recognize the hydrothermal alteration halos. Result validation was done through field and laboratory studies. Argillic, phyllic, propylitic, and iron oxides/hydroxides alterations were enhanced using color composite ratios of ASTER bands like (B4+B7)/B6 in red, (B4+B6)/B5 in green, and (B7+B9)/B8 in blue. Hydrothermal alteration mapping was also accomplished using selected PCA of OLI 2, 4, 6, and 7 bands, ASTER 4 to 9 bands and a combination of OLI 2 and 4 bands along with ASTER 4 to 9 bands. ASTER thermal infrared bands applied to determine QI and SI indices for enhancing silicic halos. Mineral potential map was produced through integrating alteration maps by fuzzy logic method in which seven areas were identified such as Sargaz Kuh copper mine, Hossein Abad manganese mine, and Esfandagheh iron mine. Results showed the possibility of establishing mineral exploration model and producing mineral potential map in reconnaissance and prospecting stages using appropriate sensors and image processing techniques.
Petrology
S. M. Tabatabaei Manesh; M. A. Mackizadeh; saeideh ranjbar; R. Gholinezhad
Abstract
Javinan skarn is located at 115 km north west of Isfahan (40 km south of Kashan and east of Ghohrud), is included in Central Iran structural zone and spread in contact with Ghohrud granitoid (Middle Miocene age) with shale, sandstone and limestone succession of the Jurassic age known ...
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Javinan skarn is located at 115 km north west of Isfahan (40 km south of Kashan and east of Ghohrud), is included in Central Iran structural zone and spread in contact with Ghohrud granitoid (Middle Miocene age) with shale, sandstone and limestone succession of the Jurassic age known as Shemshak Formation. Skarnification is made up of endo- and exoskarn subzones. Wide mineralization in these skarns hasn’t observed. Endoskarn subzone has limited occurence (from a few millimeters to a few centimeters) and exoskarn has the greatest development (from 1 meter to more than 10 meters). Endoskarn with the formation of the skarn minerals garnet, pyroxene, plagioclase, epidote and sphene, is formed in the intrusive host rock and is in the vicinity of the carbonate part. In its immediate neighborhood, exoskarn subzone starts with the formation of minerals garnet, pyroxene, idocrase, epidote, phlogopite, chlorite, quartz and calcite in the carbonate section. Mineralogical studies and textural relationship of minerals have shown that the metamorphic facies اhas reached to pyroxene hornfels in skarn rocks of this area.
M Norouzi; M. Lotfi; M. H. Emami; H. Jamali; A. Abedini
Abstract
Mesgarabad area is located in ~10 km southeast of Tehran, the Central- Alborz structural zone (CASZ) of Iran. The rock units exposed in the area consist of Eocene volcanics, volcano-sedimentary and sedimentary rocks intruded by post upper Eocene granodiorite to quartz monzo-diorite. These subvolcanic ...
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Mesgarabad area is located in ~10 km southeast of Tehran, the Central- Alborz structural zone (CASZ) of Iran. The rock units exposed in the area consist of Eocene volcanics, volcano-sedimentary and sedimentary rocks intruded by post upper Eocene granodiorite to quartz monzo-diorite. These subvolcanic intrusive bodies show porphyroid to microgranular textures and have calc-alkaline magmatic nature. These bodies produced hydrothermal fluids causing extensive alteration zones developed along the Se-Darreh-e-Bozorg strike-slip fault. The effects of hydrothermal fluids on the entire Eocene rock units and subvolcanic intrusive bodies are remarkable. The main alterations are silicification, sericitization, chloritization, epidotizaton, actinolitization, argillization, carbonatization, and alunitization-jarositization, which provided suitable physico-chemical conditions for ore-mineralization. The penetration of subvolcanic intrusive bodies into the Eocene volcanics, volcano-sedimentary and sedimentary rocks brought about skarn mineralization and epithermal barite veins. Microscopic studies and advanced analysis showed that the principal mineral phases in the epithermal zones are magnetite, pyrite, chalcopyrite, bornite, chalcocite, barite, Cu+Sn+Fe alloy, hematite, psilomelane, jacobsite, martite, geothite, and lepidochrosite. The skarnification processes occurred at two distinct stages, (1) progressive and (2) retrogressive. The pyrometasomatic anhydrous minerals such as andradite-grossularite formed during progressive stage and the hydrous minerals like epidote, chlorite, tremolite- actinolite, calcite, quartz, pyrite, chalcopyrite and chalcocite were developed during retrogressive stage. Fluid inclusion studies on primary aqueous inclusions trapped in barite crystals revealed fluid that mixing of two fluids having different physico-chemical conditions played an important role for ore deposition.
F. ayati
Abstract
In the studied area, the Cretaceous limestone rocks with abundant cracks are located on the Jurassic shales. Skarn producer fluids have influx into these cracks from a long distance and created distal skarns. The presence of a recrystallized and skarnified limestone rock layer within the shale, distinct ...
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In the studied area, the Cretaceous limestone rocks with abundant cracks are located on the Jurassic shales. Skarn producer fluids have influx into these cracks from a long distance and created distal skarns. The presence of a recrystallized and skarnified limestone rock layer within the shale, distinct the studied skarn from the most well-known skarns in Iran and puts it in the category of reaction skarns. There are some lenses of mineral deposites within skarns which is consisting mostly of magnetite and hematite. Iron-rich solutions which are drived from intrusive rocks, have left iron as magnetite in carbonate. In addition to the formation of magnetite by hydrothermal solutions, it can also be created in retrograde step by andradite alteration. These skarn is consisting mostly of pyroxene, garnet, tremolite-actinolite, chlorite and epidote. Skarnification process has occurred in two successive stages: progressive and regressive. In progressive stage, carbonate - silicate anhydrous minerals like garnet and pyroxene have occured. At later stages, because of the atmospheric water influence, garnets are altered to epidote, magnetite, calcite and quartz and pyroxenes are altered to tremolite, actinolite, calcite, quartz and opaque minerals. There are two set of garnet in studied skarn, the first one is massive (in progressive stage) and the other one is as veinlet (in regressive stage with epidote and has been created in quartz- calcit veins along with sulfide mineralization). Garnet compositions in iron deposits of studied area lie in grossular - andradite series. The compositions of studied garnet are the same as garnet compositions in Cu-Fe skarns in worldwide.
N Shirdashtzadeh; G Torabi; R Samadi
Abstract
Some dark green fragments of amphibolites are found within skarns at the south of Nain Ophiolite at the northeast of Nain city. They are similar to ortho-amphibolites (metamorphosed basic rocks) of this ophiolite in hand specimen, but mineralogically they are composed of amphibole (magnesio-hornblende, ...
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Some dark green fragments of amphibolites are found within skarns at the south of Nain Ophiolite at the northeast of Nain city. They are similar to ortho-amphibolites (metamorphosed basic rocks) of this ophiolite in hand specimen, but mineralogically they are composed of amphibole (magnesio-hornblende, Mg#>0.95), clinopyroxene (diopside, Mg#~0.61), garnet (grossular – andradite, with Grs~63-87 And~12-35), quartz, and minor amount of calcite and wollastonite. Accessory minerals are including chlorite and prehnite, mostly filling the fractures. Field studies, petrography and mineral chemistry indicate that amphibolitic fragments mineralogically differ from the skarns and ortho-amphibolites of this ophiolite; so they can be considered as olistoliths with sedimentary origin (calcic marls of sea floor), turned into amphibolitic rocks (para-amphibolite) during the regional metamorphism at amphibolite - granulite facies and low oxygen fugacity.
M Hajibahrami; N Taghipour; G Ghorbani
Abstract
The Hamyerd iron deposit is located in the northeast of Semnan in the boundary of the southern Alborz and Central Iran structural zones. A sub-volcanic body of monzonite and monzodiorite composition intruded limestone and pyroclastic rocks (equivalent to the middle Eocene Karaj formation). The iron mineralization ...
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The Hamyerd iron deposit is located in the northeast of Semnan in the boundary of the southern Alborz and Central Iran structural zones. A sub-volcanic body of monzonite and monzodiorite composition intruded limestone and pyroclastic rocks (equivalent to the middle Eocene Karaj formation). The iron mineralization occurred at the contact between intrusive bodies and these sedimentary rocks. The extensive hematite content along with minor amounts of magnetite, goetite, limonite, pyrite, dolomite, barite and calcite are important characteristics of the Hamyerd ore deposit. Mineralization occurred as veins and also hematite lenses with minor magnetite content. Fluid inclusion and stable isotope (S, C and O) studies were integrated to explore the Hamyerd iron ore genesis. Petrographic studies display five types of fluid inclusions in quartz and 4 types in barite. Fluid inclusions in quartz include single-phase liquid, single-phase gas, two-phase liquid-rich, two-phase gas-rich, and three-phase (liquid-solid-gas) inclusions. Three-phase liquid-solid-gas inclusions were not detected in barite. Microtermometry studies in two-phase liquid-rich inclusions revealed homogenization temperatures of 200-250 ˚C and 100-200 ˚C, and salinities of 10-20 and 0.5-5 wt% NaCl equivalent for quartz and barite fluid inclusions, respectively. Microthermometry of halite-bearing three-phase fluid inclusions showed homogenization temperature from 200 to 350 ˚C and salinity from 30 to 40 wt% NaCl equivalent. δ34SCDT values of pyrites at Hamyerd iron deposit are in the range of 2.2 to 7.4‰. The isotopic values of barites range from 13.6‰ to 20.2‰ for δ34SCDT and 10.2‰ to 12.1‰ for δ18OVSMOW, respectively. The carbon and oxygen isotopic values of calcite are in the range of -3.4‰ to -4.5‰ and 17.7‰ to 19.1‰, respectively. Microthermometry of fluid inclusions and stable isotopes (S, O, C) at Hamyerd iron deposit suggested mixing of magmatic and meteoric fluids as origin of hydrothermal solutions. Mineralization in the Hamyerd iron deposit is probably similar to Fe-skarn deposits.
H Mohammaddoost; M Ghaderi; N Rashidnejad-Omran
Abstract
Qamsar cobalt deposit is located 26 km south of Kashan, in the middle part of Urumieh-Dokhtar magmatic arc. Exposed rock units in the area include Eocene volcanics, Qom Formation marine sediments and plutonic bodies. The intrusive bodies have quartz-diorite to granodiorite composition as well as porphyry ...
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Qamsar cobalt deposit is located 26 km south of Kashan, in the middle part of Urumieh-Dokhtar magmatic arc. Exposed rock units in the area include Eocene volcanics, Qom Formation marine sediments and plutonic bodies. The intrusive bodies have quartz-diorite to granodiorite composition as well as porphyry microdiorite. Intruding bodies into the Eocene volcanics and Qom Formation units caused recrystallization and metamorphism and formed assemblages of skarn minerals such as garnet, pyroxene, epidote, tremolite and actinolite. Mineralization occurred as endo-skarn and exo-skarn in massive, vein, brecciated, open space filling and diffusion forms. Magnetite is the main ore mineral and is accompanied by cobaltite, chalcopyrite and pyrite. Fluid inclusion microthermometry studies were performed on prograde stage garnet and pyroxene and retrograde stage quartz. Microthermometry studies show homogenization temperatures from 400 to more than 600°C and from 180 to 200°C as well as salinities between 12 and 20% and between 5.8 and 11.9% wt NaCl equiv. for prograde and retrograde phases, respectively. Isotopic thermometry on pyrite-chalcopyrite pair minerals gives 241 to 528°C and that for quartz-magnetite pair minerals gives 441 to 549 °C. Sulfur and oxygen isotopic ratios offer magmatic origin which mixed with basinal fluid for this mineralization.
A Zahedi; M Boomeri
Abstract
The Panah-Kuh skarn is situated in 50km NW of Taft City in Yazd province. Inrtusion of granodioritic stock into the calcareous-dolomitic rocks of Permian Jamal Formation led to formation of calcic and magnesian skarns. The REE patterns of skarns and its forming garnets show Eu/Eu* and Ce/Ce*ratios increase ...
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The Panah-Kuh skarn is situated in 50km NW of Taft City in Yazd province. Inrtusion of granodioritic stock into the calcareous-dolomitic rocks of Permian Jamal Formation led to formation of calcic and magnesian skarns. The REE patterns of skarns and its forming garnets show Eu/Eu* and Ce/Ce*ratios increase with increasing of ∑REE, implying that skarn forming fluids were dominantly of magmatic origin, whereas (Pr/Yb)cn ratio decrease almost with increasing of ∑REE that implying the magmatic fluids granitoid-derived had not much REE during the Panah-Kuh skarn formation. Based on the fluid inclusion data from garnet, fluid temperature and salinity in the prograde stage vary between 308-380oC and 12.6-23.8 wt.% NaCl equivalent, respectively. Inclusion fluids in the calcite had lower temperature (T<280°C) and fluid salinity decline to 3.5 wt.% NaCl equivalent. Mixing and dilution of early magmatic fluids with external fluids (e.g., meteoric waters) caused a decrease in fluid temperature and salinity in latest stage of the skarn formation. Therefore, both REEs and fluid inclusions data suggest the dominant role of magmatic water in the formation of Panah-Kuh skarn.
S Shahbazi; M Ghaderi; N Rashidnejad-Omran
Abstract
The Bashkand iron deposit is located in 16 km southwest of Soltanieh, in Central Iran Structural Zone. The rock units in the area include alternations of metamorphosed sedimentary rocks of the Kahar Formation, Khorramdarreh granite and an andesitic dike. The major alteration types are argillic, potassic, ...
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The Bashkand iron deposit is located in 16 km southwest of Soltanieh, in Central Iran Structural Zone. The rock units in the area include alternations of metamorphosed sedimentary rocks of the Kahar Formation, Khorramdarreh granite and an andesitic dike. The major alteration types are argillic, potassic, chloritic, sericitic and quartz-carbonatic in composition. N30-50W trend and S30-50W dip mineralization conforms primary bedding, foliation of phyllites as well as parallel faults. Mineralogical paragenesis includes: 1) Grossularite, pyroxene, idocrase; 2) Andradite, pyroxene, forsterite, phlogopite, magnetite; 3) Tremolite, serpentine, epidote, talc, biotite, magnetite, specularite and sulfides, and they have been cut by quartz-carbonate veins. The presence of magnetite synchronous with quartz and feldspar in the intrusive body, unconformity in behavior pattern of Fe2O3 with SiO2 and Al2O3, and its conformity with other major oxides as well as Cu and Zn, similarity of REE pattern in the ore, the intrusive body and skarnized host rocks as well as no similarity with the less altered host rocks, are the signs of sourcing ore from the intrusive-deriven fluids. Mixing of these fluids with meteoric water together with increasing in oxygen fugacity in the retrograde metasomatism stage led to ore mineralization.
A Zahedi1; M Boomeri; M.A Mackizadeh
Abstract
The garnets from the KhutSkarn in the west of Yazd have been formed as a result of hydrothermal activity ofOligo-Miocene calc-alkaline plutons. The chemical composition of garnets in the Khutskarn are divided into two solid solution of grossularitic-andraditic and almost pure andradite different types. ...
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The garnets from the KhutSkarn in the west of Yazd have been formed as a result of hydrothermal activity ofOligo-Miocene calc-alkaline plutons. The chemical composition of garnets in the Khutskarn are divided into two solid solution of grossularitic-andraditic and almost pure andradite different types. The Fe-rich garnets are isotropic (Adr>96), whereasgrossularitic-andraditic garnets are anisotropic and show compositional zoning and sectorial twinning(Ad74.3Gr24.8-Ad32.1Gr66.6). The compositional zoning of anisotropic garnets may result from hydrothermal overgrowths on contact metamorphic minerals, variations in P, T, XCO2, concentrations of Fe3+ and Al, or kinetic factors. The Laser Ablation ICP-MS results show isotropic garnets exhibit LREE-enriched and HREE-depleted patterns, with a positive Eu anomaly. These garnets grow rapidly under relatively high W/R ratios from the magmatic-derived fluids during infiltration metasomatism process, whereas anisotropic garnets have much lower enrichment in LREE and show a weak negative Eu anomaly. These garnets formed by prolonged interaction of pore fluids with the host rocks during the diffusive metasomatism process.
M. A. A. Mokhtari; H. Moinvaziri; M. R. Ghorbani; M. Mehrpartou; G. Hosseinzadeh
Abstract
Kamtal skarn zone is located in the 20km north of Kharvana in the Eastern Azarbaijan. Skarn-type metasomatic alteration is the result of Kamtal monzonitic intrusion into the Upper Cretaceous impure carbonates. Kamtal skarn include exoskarn and endoskarn zones. Exoskarn is the major zone that its thickness ...
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Kamtal skarn zone is located in the 20km north of Kharvana in the Eastern Azarbaijan. Skarn-type metasomatic alteration is the result of Kamtal monzonitic intrusion into the Upper Cretaceous impure carbonates. Kamtal skarn include exoskarn and endoskarn zones. Exoskarn is the major zone that its thickness varies between 100-600m. Field and mineralogical studies demonstrate that exoskarn zone composed of garnet rich sub-zone (garnet skarn), epidote rich sub-zone (epidote skarn) and marble sub-zone. Garnet is the most important calc- silicate mineral within the garnet skarn sub-zone. They are mainly grossularitic in composition (Ad33-35), but along the fractures, andraditic composition (Ad66-73) is predominant. Clinopyroxene is the other dominant mineral within garnet skarn sub-zone that has diopsidic composition (Di82.8-85.7). In the epidote skarn sub-zone, epidote is the predominant mineral while garnet and clinopyroxene present in some places and have low concentration. Petrographic studies indicate that marly limestone was the primary rocks of the garnet skarn sub-zone while clay-bearing marl was the primary rocks of the epidote skarn sub-zone. Skarnification process can be categorized into two discrete stages: 1) prograde and 2) retrograde stages. Prograde stage began immediately after the initial emplacement of the Kamtal monzonitic magma into the enclosing impure carbonate rocks. The effect of heat flow from the intrusion caused the enclosing rocks to become isochemically marmorized in almost homogeneous limestone layers and bimetasomatized (skarnoid–hornfels) in thin interlayers of clay-rich carbonates. Invasion of segregated fluid phase of Kamtal intrusion into the fractures and micro-fractures of the marmorized and skarnoid–hornfelsic rocks incorporate considerable amounts of Fe, Si and Mg into the metasomatic aureole. During retrograde stage, due to relatively low temperature hydrothermal fluids and processes such as hydrolysis, carbonation and sulfidation, considerable amounts of hydrous calc-silicates, sulfides, oxides and carbonates replaced the anhydrous calc-silicates. Garnet and clinopyroxene are the most abundant mineral assemblage in Kamtal skarn zone, which were formed in temperature lower than 550°C. Lack of wollastonite in this mineral assemblage, intergrowth of garnet and clinopyroxene crystals and lack of any reaction rim between these crystals, and lack of emplacement texture indicate that they formed contemporaneously within the temperature and ƒO2 ranges of 430–550ºC and 10-26–10-23, respectively.
N. Khanmohammadi; A. Khakzad; J. Izadyar
Abstract
Zaker iron deposit is located in the northeast of Zanjan city and is a part of Tarom volcano – plutonic belt in Azarbaijan – West alborze structural zone. The main rocks of the area consist of folded volcanic - volcanoclastic rocks including breccia tuff, lapilli-tuff and andezitic – ...
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Zaker iron deposit is located in the northeast of Zanjan city and is a part of Tarom volcano – plutonic belt in Azarbaijan – West alborze structural zone. The main rocks of the area consist of folded volcanic - volcanoclastic rocks including breccia tuff, lapilli-tuff and andezitic – basaltic lava of Amand member of Karaj formation with Eocene age that folded. Plutonic rocks with probably Oligocene age with various lithology changing from quartzmonzodiorite, quartzmonzonite to quartzsyenite with NW-SE trend were intruded into the volcanic – volcanoclastic rocks. Fe-mineralization occurred in interval of plutons and volcanic - volcanoclastic rocks. The main ore mineral is magnetite – apatite with minor amounts of quartz and calcite. As well as magnetite- apatite mineralization, pyrite with minor amounts of chalcopyrite occurred in sulphide veinlets. The mineralization has been seen in five forms: veinlets of magnetite in form of stock- work, massive magnetite- apatite, banded magnetite- apatite, coarse grained magnetite- apatite veins and sulphide veinlets. Intrusion of ore deposit into host volcanic rocks, are associated with skarn metasomatism that form actinolite, talc, chlorite, phlogopite, quartze, calcite and epidote. Geothermobarometry for the skarn part, indicate that XCO2 is about 0.9, pressure of 2 kbar and the temperature is about 400-500 0C for metamorphic reactions. Detailed studies on textures and structures suggest the source of the iron from Zaker granitoid body and volcanic rocks are host rocks for iron deposit. Mineralography investigations are indicative of magmatic origin and show the best correlation with "Kiruna–type" iron ores.
A. R. Ghiasvand; M. Ghaderi; N. Rashidnejad-Omran
Abstract
The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of ...
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The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of calc-alkaline and metaluminous composition, representing I-type granite characteristics, has intruded the Eocene volcanopyroclastic rocks in the north of Semnan. Skarn development and iron mineralization have occurred at the contact of the intrusive body and the volcanopyroclastic rocks. Mineral Paragenesis consists of magnetite accompanied by hematite, oligist, pyrite, chalcopyrite, garnet, pyroxene and epidote. Geometry of the ore bodies is massive, lenticular and vein type and their texture is disseminated, brecciated, vein-veinlet and massive. Dominant alterations in the area are propylitic, argillic, silicic, sericitic, chloritic and pyritic, respectively. The intrusive body has many similarities with intrusive bodies which form Fe-skarn deposits. Variations in the calculated parameters for REE indicate contribution of magmatic origin hydrothermal fluids to mineralization and that the intrusive body has had the dominant role as source of the skarn ore materials. Along with the intrusion, emplacement and crystallization of intrusive body, Fe-bearing fluids have intruded the volcanopyroclastic rocks, forming sodic metasomatism and deposited iron ores in the north of Semnan which have many similarities with calcic Fe-skarn deposits.
H. Jamali; A. Yaghubpur; B. Mehrabi
Abstract
Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising ...
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Miveh – Rud area is located 50 km north of Tabriz and 65 km west of Ahar at 36ْْ 33′ 02″to 38ْ, 34′ 52″ N and 46 ْْ 12′ 20″ to 46 ْْ 14′ 35″ E. The oldest rock unit in the area includes a thick sequence of Paleocene sedimentary rocks comprising of sandstone, shale, siltstone, marl and marly limestone that have been intruded by a porphyritic intrusive body and dykes of granodioritic to diabasic composition (probably Oligocene in age). The intrusive rocks resulted in the formation of hornfels, skarn and alteration in Paleocene rocks. All of the mentioned rock units are unconformably covered by Pliocene age trachyte, trachyandesite. Alteration of potassic, sericitic, argillic, propylithic and silicification types occurred in the subvolcanic and sedimentary rocks, while there is no observed alteration in the volcanic cover. Anomalies of Au, Ag, Sb, Cu, Bi, W and Mo detected by geochemical investigations are confirmed by field evidences.
The anomalies of Sb, Ag, Au and As are located in the northern part, while the Cu, Co, W and Mo anomalies are in the southern part of the area. The degree of the contact metamorphism decreases toward the north and the potassic alteration can be shown mostly in the southern part of the area. This may suggest uplift and erosion of the southern part compared to northern part of the studied area. Composite halos of As, Pb, Ag / Cu, W and Co confirm the results.The mineralization includes formation of skarn, epithermal and sheeted veins. The epithermal veins cut the skarn and other contact metamorphic rocks.
M. H. Karimpour; A. Malekzadeh Shafaroudi
Abstract
Sangan Iron ore deposit is located 300 km southeast of Mashhad (Eastern Iran). Based on the high grade, low P- content and big ore reserve, Sangan is an important Iron mine in Iran. It is a magnetite skarn and can be classified as iron-oxide type deposit. Based on the surface exposure, the western magnetite ...
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Sangan Iron ore deposit is located 300 km southeast of Mashhad (Eastern Iran). Based on the high grade, low P- content and big ore reserve, Sangan is an important Iron mine in Iran. It is a magnetite skarn and can be classified as iron-oxide type deposit. Based on the surface exposure, the western magnetite skarn (A´), a Ca-rich type skarn, was formed at the contact of intrusive. Eastward, the skarn gradually becomes distal and Mg-type. The A´ magnetite skarn contains andradite, magnetite, K-rich amphibole, hedenbergite and calcite. Magnetite skarn in A, B, and C- south contain magnetite, repidolite, ferro-actinolite, siderite and minor pyrite. Baghak and C- north magnetite skarn comprise Mg-rich- magnetite, phlogopite, chinochlore, talc, dolomite, forsterite, dolomite, pyrite ± chalcopyrite ± arsenopyrite ± pyrrhotite. High S-content is found mainly in Baghak and C-north deposits. In this research, the igneous source rock is found in A´ deposit and identified as ultra-potassic type (K2O> %9). Sarnowsar granite which used to be the source rock for Iron, contains less than %5 K2O, therefore it cannot be the source. The K2O content of Sarnowsar granite increases near the magnetite skarn due to alteration. The Fe-ore bearing solution moved along the contact between Sarnowsar granite and the limestone. Sarnowsar granite was altered and skarn formed in the limestone.
The source rock is quartz biotite-hornblende alkali syenite to quartz hornblende syenite porphyry. The younger intrusive rocks are biotite granite, biotite-hornblende quartz monzonite porphyry and quartz syenite porphyry. Potassium within the ore bearing solution controlled the mineralogy of skarn. Contact skarn in A´ magnetite deposit comprises K-rich amphibole and distal skarn (Baghak and C-north) contains phlogopite.
Comparison of trace elements from source rocks with Sarnowsar granite indicates that the Nb, Zr, Zn and Rb contents are high in the former rocks and Cu and Sr ones are higher in the latter rock. Furthermore, comparison of some trace elements from source rocks with younger intrusive rocks indicate that Cr, Ni, Zr, Ce, Cu, Sr, and La contents are higher in younger intrusive and Rb content is higher in source rocks.
