Economic Geology
Hadi Mohammadian; vartan simmonds; kamal Siahcheshm
Abstract
The Sarikhanloo area is located within the Qaradagh metallogenic zone in northwest Meshgin Shahr. Igneous rocks cropped out in this area include successions of Paleocene-Eocene pyroclastic rocks (tuff and andesitic-dacitic lavas with intercalations of ignimbrite) and basaltic andesite lava flows. Igneous ...
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The Sarikhanloo area is located within the Qaradagh metallogenic zone in northwest Meshgin Shahr. Igneous rocks cropped out in this area include successions of Paleocene-Eocene pyroclastic rocks (tuff and andesitic-dacitic lavas with intercalations of ignimbrite) and basaltic andesite lava flows. Igneous rocks show high-K calc-alkaline to shoshonitic nature and are mainly metaluminous, formed in a post-collisional uplift tectonic setting. Hydrothermal activities in this area brought about formation of vast silicic veins and caps, along with silicic, propylitic, phyllic (non-pervasive) and intermediate argillic alterations around the veins, as well as intermediate to advanced argillic alteration halos at the margins of silicic caps. Ore minerals in the silicic veins includes pyrite, arsenopyrite and Fe-oxides, accompanied by minor malachite, formed during four mineralization stages. Fluid inclusion studies indicate that the homogenization temperature of fluid inclusions ranges from 175 to 355 °C, considering the low pressure of fluid inclusions (≤ 0-40 bars), can signify the fluid temperature at the time of entrapment. The estimated salinity values are between 0.2 and 3 wt% NaCleq.
Remote Sensing
Mina Zamyad; Peyman Afzal; Mohsen Pourkermani; Reza Nouri; Mohammadreza Jafari
Abstract
Tirka area is situated in NE Iran as a part of the TCMB which consists of Paleogene sediments and volcanic rock units with a combination of Eocene intermediate to basic rocks. The research aim is to determine the alteration zones using C-N fractal model based on ASTER satellite images. First, the ASTER ...
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Tirka area is situated in NE Iran as a part of the TCMB which consists of Paleogene sediments and volcanic rock units with a combination of Eocene intermediate to basic rocks. The research aim is to determine the alteration zones using C-N fractal model based on ASTER satellite images. First, the ASTER data was processed using SFF method for determination of iron oxide, propylitic, phyllic, and argillic alteration zones. The C-N fractal model is utilized for the separation of different parts of alteration zones. The results derived via the C-N fractal model showed that the main trend of the alteration zones is in NE-SW direction. Also, based on the C-N log-log plots, there are six geochemical populations for iron oxide alteration, four geochemical populations for argillic and phyllic alterations, and five geochemical populations for propylitic alteration. There is a high intensity of alteration zones commences with 223 for iron oxide, 204 for argillic, 199 for propylitic and phyllic alteration zones. In order to validate the results, field observations and petrographical studies based on thin-polish sections were carried out. These data confirmed the alteration zones obtained by the modeling. the data obtained from the combination methods, were verified by Logratio matrix,
Negin Fazli; Majid Ghaderi; David Lentz; Jianwei Li
Abstract
The North Narbaghi deposit is located approximately 26 km northeast of the city of Saveh in the central part of Urumieh-Dokhtar magmatic arc of Iran. In this area, the Oligo-Miocene intrusive rocks cut the Eocene volcano-sedimentary rocks intruding into the surrounding rocks causing extensive alteration ...
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The North Narbaghi deposit is located approximately 26 km northeast of the city of Saveh in the central part of Urumieh-Dokhtar magmatic arc of Iran. In this area, the Oligo-Miocene intrusive rocks cut the Eocene volcano-sedimentary rocks intruding into the surrounding rocks causing extensive alteration zones such as phyllic, argillic, propylitic and tourmalinization. The intrusive rocks include diorite, monzodiorite, megadiorite with calc-alkaline nature which formed as a result of subduction of the Neo-Tethyan oceanic crust beneath the Central Iranian block. The epithermal Ag-Cu mineralization at North Narbaghi, with vein-veinlet and breccia geometries is mainly hosted in andesite, lithic tuff, diorite and monzodiorite. At the North Narbaghi deposit, ore minerals can be divided into four groups: sulfides (chalcopyrite, pyrite, sphalerite, bornite), sulfosalts (tetrahedrite, tennantite), carbonates (azurite, malachite) and oxides (hematite, goethite). The alteration shows a relative concentration pattern at the North Narbaghi deposit; the argillic, sericitic and calcite alteration types are in close connection with the Ag-Cu mineralization and the propylitic and tourmalinization alteration types occur at the margin of mineralization. The main characteristics of mineralization such as geodynamic environment, host rocks, mineralogy, metal content, geometry, alteration and comparing these features with the characteristics of epithermal deposits, show that the North Narbaghi deposit can be classified as a typical intermediate-sulfidation (IS) epithermal mineralization.
Economic Geology
Mitra Eftekhari; Mohammad reza Hosseinzadeh; Mohsen Moayyed
Abstract
The Studied area is located in vicinity of the Sherbit village, about 28 km to the northwest of Ahar (in Eastern Azerbaijan province. Quartz monzonite intrusion is the host rock of hydrothermal tourmaline in this area. On the basis of their textural features, the tourmalines can be divided into four ...
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The Studied area is located in vicinity of the Sherbit village, about 28 km to the northwest of Ahar (in Eastern Azerbaijan province. Quartz monzonite intrusion is the host rock of hydrothermal tourmaline in this area. On the basis of their textural features, the tourmalines can be divided into four groups: 1) tourmaline veins, 2) tourmaline-breccias, 3) massive tourmaline and 4) pore space filling tourmaline. Based on the petrography and electron microprobe analysis studies, tourmalines of Sherbit area are correspond to intermediate schorl-dravite with more tendencies toward dravite composition and have been formed in hydrothermal conditions. According to reasons such as more Mg values compared to Fe, low Al amounts, fine scale zoning, content of fluorine, tendency toward outer side of alkali- and proton-deficient vectors and lack of negative correlation between Fe and Mg. Separated tourmaline from the quartz– tourmaline vein shows a very similar pattern to the quartz monzonite samples, which are characterised by a pattern with depletion in HREEs relative to LREEs. It can be concluded that REE concentrations and patterns of tourmaline from the different studied tourmaline rocks are controlled by the host rock and not by the hydrothermal fluid causing boron metasomatism.
A Abedini
Abstract
The Basir-Abad area (northeast of Ahar, East-Azarbaidjan province) is a part of the Cenozoic Ahar-Arasbaran magmatic belt in northwest of Iran. Intrusion of granitic and granodioritic igneous rocks of Oligocene age into the Eocene volcanic rocks (andesite, trachy-andesite, andesi-basalt and basalt) resulted ...
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The Basir-Abad area (northeast of Ahar, East-Azarbaidjan province) is a part of the Cenozoic Ahar-Arasbaran magmatic belt in northwest of Iran. Intrusion of granitic and granodioritic igneous rocks of Oligocene age into the Eocene volcanic rocks (andesite, trachy-andesite, andesi-basalt and basalt) resulted in occurrence of metallic mineralization along with development of widespread alteration zones in this area. Mineralogical studies indicate that these alteration zones include silicic (quartz), intermediate and advanced argillic (kaolinite, smectite, quartz and alunite), and propylitic (chlorite, epidote, albite and calcite). Hypogene ores within veins and veinlets of silicic alteration zone contain pyrite, chalcopyrite and galena accompanied by covellite, copper-carbonate minerals (malachite and azurite) and iron-oxides and- hydroxides (goethite, limonite and hematite) of supergene origin. The distribution patterns of REEs normalized to chondrite display differentiation and enrichment of LREEs relative to HREEs and occurrence of variant negative Eu anomalies in all alteration zones. Mass balance calculations of elements, using isocon method, indicate that during development and evolution of the silicic and the intermediate argillic alteration zones, REEs experienced enrichment in the former and depletion in the latter. Furthermore, development of advanced argillic and propylitic alteration zones was accompanied by enrichment of LREEs and selective depletion of HREEs. Further investigation revealed that occurrence of negative Eu anomaly (0.20-0.23) in silicic alteration zone is related to abundance of chloride ions, increase of oxygen fugacity of hydrothermal system and highly acidic nature of the fluid. The results obtained from geochemical studies (mass balance calculations, changes in values of Eu and Ce anomalies and ratios of REEs) suggest that changes of pH, temperature, oxygen fugacity, difference in abundance and type of complexing ions in solution, fluid/rock ratio, and presence of minerals such as kaolinite, goethite, smectite, hematite and alunite played important role in differentiation, mobilization and distribution of lanthanides in the studied alteration system.
M Boveiri Konari; E Rastad; M Rastad; A Nakini; M Haghdoost
Abstract
Tappehsorkh Zn-Pb-(Ag) deposit, hosted by Lower Cretaceous siltstone, tuff and dolomite, is located in the northern part of the Irankuh mountain range, south of Esfahan. Sulphides in this ore have a relatively simple mineralogy including sphalerite, galena, tetrahedrite, pyrite and to a lesser extent, ...
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Tappehsorkh Zn-Pb-(Ag) deposit, hosted by Lower Cretaceous siltstone, tuff and dolomite, is located in the northern part of the Irankuh mountain range, south of Esfahan. Sulphides in this ore have a relatively simple mineralogy including sphalerite, galena, tetrahedrite, pyrite and to a lesser extent, chalcopyrite, marcasite and bornite. Gangue minerals are predominantly dolomite, quartz and barite. Based on zoning in the sulphide mineralization, texture and structure and location of ore facies relative to syn-sedimentary normal faults, theses ore facies are classified as vein-veinlet, laminated and massive. Dolomitic-silicic alteration is among the major processes concomitant with sulphide mineralization. The greatest degrees of alteration and related ore mineralization occur at the vicinity of the normal faults and decrease away from it. Geochemical studies indicate that the ore-bearing fluids were of oxidized composition, which were reduced once reaching favorable host rocks and consequently deposited sulphide minerals. Minor and trace element studies in the various sulfide ore facies demonstrate that the ore-bearing fluid in all the ore facies has a similar composition. Textures such as framboidal pyrite, contemporaneous folding of organic matter along with sulphide lamination in the laminated ore facies, and diagenetic structures such as load casts in the host siltstone indicate that sulphide mineralization has occurred in the sedimentary-diagenetic stage. However, sulphide mineralization in the regional dolomite is considered to have occurred in a shallow diagenetic environment because of replacement of regional dolomite by hydrothermal dolomite. Based on features of ore mineralization such as the extensional tectonic setting, siltstone and carbonate host rocks, and occurrence of various sulphide facies such as vein-veinlet, laminated and massive, the Tappehsorkh deposit is very similar to Sedex-type deposits.
M.R Hosseinzadeh; S Maghfouri; M Moayyed; M Lotfehnia; B Hajalilou
Abstract
The studied area is located in Tarom metallogenic zone (NW of Iran). This area illustrate widespread hydrothermal alteration and disseminated and vein-veinlet type copper, lead and zinc mineralization.Injection of qm Intrusive body into Eocene volcano clastic complex (Karaj Formation) along linear Faults ...
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The studied area is located in Tarom metallogenic zone (NW of Iran). This area illustrate widespread hydrothermal alteration and disseminated and vein-veinlet type copper, lead and zinc mineralization.Injection of qm Intrusive body into Eocene volcano clastic complex (Karaj Formation) along linear Faults caused intense hydrothermal alterations such as phyllic, argillic, propylitic and silicification. The major minerals of this rock are plagioclase, biotite, pyroxene, hornblende, alkali-feldespar, quartz with Lesser amount apatite, zircon, opaq minerals, rutile and sphene. Based on microscopic and geochemical assessments this rock is quartz- monzonite, tonalite, quartz- monzodiorite, and has calk-alkaline to shoshonitic and meta-aluminous character. This Pluton belongs to a volcanic arcs regime. The hydrothermal activities of penetrate intrusion causes the creation of two system vein and veinlet: ore bearing quartz vein- veinlet’s and non-ore bearing carbonate vein- veinlets. The mineralization in loubin- zardeh occured in quartz vein- veinlet along faults created via the intrusion of the intrusive. The main mineralizations of area are oxide (illmenite), sulfide (pyrite, Chalcopyrite, galena, sphalerite), sulfate (barite) and the supergene minerals are oxides and hydroxide, (hematite, goetite), sulfide (covelite), sulfate (anglesite) and carbonate (malachite and azourite). The most important characteristics of mineralization at the Lubin- Zardeh area such as tectonic setting, host rocks, mineralogy, metal content as well as wall rock alterations, and to compare these characteristics with the basic features of Epithermal deposits, the polymetal vein- veinlet mineralization in Lubin- Zardeh placed in the Epithermal category.
M. H. Ahmadi; G.H Shamanian; H. Azmi
Abstract
The Motrabad vein system is located 30 Km southwest of Bajestan in the northern part of the Lut Block. The vein host rocks consist of intermediate to silicic volcanic rocks. The mineralization occurs as irregular veins, veinlets and hydrothermal breccias. Based on field geology and textural evidences ...
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The Motrabad vein system is located 30 Km southwest of Bajestan in the northern part of the Lut Block. The vein host rocks consist of intermediate to silicic volcanic rocks. The mineralization occurs as irregular veins, veinlets and hydrothermal breccias. Based on field geology and textural evidences four types of quartz veins (A, B, C and D) were identified. Hydrothermal alteration is developed around the veins and tends to be more intense in the vicinity of the veins. Hydrothermal alteration consists of silicic, sericitic, propylitic and argilic assemblages. The plot of the Ishikawa alteration index (AI) Vs. chlorite-carbonate-pyrite index (CCPI), known as alteration box plot, display the main alteration trends. The hydrothermal alteration assemblage of quartz, adularia, chlorite, illite, calcite, and pyrite that envelopes the Motrabad vein system formed from the upwelling of near-neutral to weakly alkaline chloride waters. The mineralogic, alteration and geochemical characteristics of the studied area and their comparison with epithermal ore deposits represent an epithermal system of the low-sulfidation type.
D. Esmaeily; S. Z. Afshooni
Abstract
The Astaneh granitoid massif in the Sanandaj-Sirjan zone, covering an area of about 30 km2, located in 40 km to Arak city, is mainly composed of granodioritic rocks. They are widely affected by hydrothermal alteration and six alteration zones including phyllic (sericitic), chloritic, propylitic, argillic, ...
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The Astaneh granitoid massif in the Sanandaj-Sirjan zone, covering an area of about 30 km2, located in 40 km to Arak city, is mainly composed of granodioritic rocks. They are widely affected by hydrothermal alteration and six alteration zones including phyllic (sericitic), chloritic, propylitic, argillic, albitic and tourmalinization zones are identified in this area. Calculations of chemical index of alteration (CIA) indicates that phyllic (sericitic), chloritic, propylitic, argillic, albitic and tourmalinization alteration zones underwent the hydrothermal alteration about 63.47%, 59.73%, 61.54%, 63.69%, 60.61%, 65.43% respectively. The mass changes of elements, based on Al (as a monitor immobile element), indicate that considerable amounts of oxides such as Fe2O3, MgO, CaO and TiO2 and also LFSEs such as K, Rb, Sr, Cs and Ba in all of the alteration zones were depleted. The results show that SiO2 was added to the phyllic (sericitic), argillic and tourmalinization alteration zones by metasomatizing fluids. Al2O3 was immobile and its mass was essentially unchanged during alteration. Other oxides such as MnO, Na2O, K2O and P2O5 and also LOI show dissimilar behaviors in the different zones. In all of the zones there is depletion in Sc and Y (HFSE). Also the Ga (except in chloritic zone) and U (except in phyllic zone) were depleted. In the phyllic zone, La, Ce, Pr, Nd (LREE), Sm, Eu, Gd (MREE) and Yb (HREE) were added; however, Dy, Er and Ho were depleted, whereas Tb and Lu were unchanged. In all zones the REEs were depleted except in the chloritic zone where Eu and Yb were added and Lu was essentially unchanged during alteration.
