Economic Geology
Negar Kaboudmehri; Hossein Kouhestani; Mir Ali asghar Mokhtari; Afshin Zohdi
Abstract
The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the ...
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The Toryan occurrence is located in the Central Iran zone, 120 km northwest of Zanjan. Pb–Zn mineralization at Toryan occurred as laminated and lens-shaped parallel to lamination of grey sandstone units of the Upper Red Formation. Mineralization often formed around and within the fragments of the plant fossils, and shows disseminated, replacement, solution seems, intergranoular cement, framboidal, and vein-veinlet textures. At Toryan, ore horizon has 1 m thickness and approximately 350 m length and contains three zones include the red oxidized zone, the bleached zone and the mineralized reduced zone. Galena, sphalerite, pyrite and arsenopyrite are the main ore minerals at Toryan occurrence. Cerussite and goethite are formed during supergene and wethering processes. Comparison of trace elements and REE patterns of barren red and grey host sandstones and mineralized samples indicate that mineralized samples show lower concentrations of trace elements and REE. Based on tectonic setting, sedimentary environment, host rock, presence of plant fossils, geometry, ore texture and mineralogy and alteration, Toryan occurrence can be classified as sediment-hosted Cu deposits of Redbed type, and is comparable with another Redbed type of Cu and Pb–Zn deposits in the Avaj-Zanjan-Tabriz-Khoy belt.
Petrology
Tahereh Parsa; Monireh Kheirkhah; Mir Ali asghar Mokhtari
Abstract
Cenozoic acidic volcanic rocks at the south of Qezel Ozan River are located within the Western Alborz-Azarbaijan magmatic zone and northern part of the Iranian-Turkish Plateau. The Oligocene acidic lavas in north part of Zanjan show rhyolitic to dacitic composition. Hyaloporphyritic to hyalomicrolithic ...
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Cenozoic acidic volcanic rocks at the south of Qezel Ozan River are located within the Western Alborz-Azarbaijan magmatic zone and northern part of the Iranian-Turkish Plateau. The Oligocene acidic lavas in north part of Zanjan show rhyolitic to dacitic composition. Hyaloporphyritic to hyalomicrolithic porphyritic textures are the main texture in these rocks. They were erupted along the main faults in this area. Feldspars, biotites and hornblendes are the major phenocrysts which are embedded in a glass matrix or micro phenocrysts of felsic and mafic minerals. By Geochemical studies it is indicated that these rocks have high-K calc-alkaline to shoshonitic nature and classified as meta-aluminous and I-type acidic rocks. In the chondrite normalized rare earth elements diagram, these rocks demonstrate LREE enrichment and high LREE/HREE ratio. Enrichment in LREE and depletion in HREE is characteristic of the calc-alkaline rocks in active continental margins. Furthermore, these rocks show enrichment in LILEs and negative anomalies of HFSEs (Ti, Nb and Ta) which is the feature of magmatic rocks associated with Post-COLG subduction zones. The geochemical evidences suggest that the parental acidic magma is resulted from partial melting of lower crust as a result of pressure reduction during the local tension mechanism.
Economic Geology
Fatemeh Naderlou; Mir Ali asghar Mokhtari; Hossein Kouhestani; Ghasem Nabatian
Abstract
North Chargar Cu-Au mineralization located within the Tarom-Hashtjin sub-zone. This area composed of andesite and quartz-andesite lavas alternated with tuffaceouce rocks. The volcanic rocks have calc-alkaline nature and were formed in an active continental margin. Mineralization present as ore-bearing ...
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North Chargar Cu-Au mineralization located within the Tarom-Hashtjin sub-zone. This area composed of andesite and quartz-andesite lavas alternated with tuffaceouce rocks. The volcanic rocks have calc-alkaline nature and were formed in an active continental margin. Mineralization present as ore-bearing quartz vein-veinlets within a silicified zone. Based on mineralogical studies, chalcopyrite and pyrite are the main ore minerals, and malachite, covellite, chalcocite and goethite were formed by supergene processes. Quartz, barite and chlorite present as gangue minerals. Hydrothermal alterations include silicification, chloritization, sericitization and argillic. Ore and gangue minerals show disseminated, vein-veinlet, brecciated, cockade, comb, replacement, relict and open space filling textures. Based on field and microscopic studies, Cu-Au mineralization in the north Chargar can be divided into four stages: 1- the first stage is silicification of volcano-sedimentary host rock along with disseminated pyrite mineralization, 2- the second stage present as chalcopyrite and pyrite-bearing quartz vein-veinlets and hydrothermal breccia cement, 3- the third stage includes barite vein-veinlets crosscutting the previous stages of mineralization, 4- the last stage is related to supergene processes. Geological features, mineralogy and ore structure-textures in the north Chargar Cu-Au occurrence indicate most similarity with base metal epithermal (intermediate sulfidation) deposit type.
Economic Geology
Hossein Bagherpour; Mir Ali Asghar Mokhtari; Hossein Kouhestani; Ghasem Nabatian
Abstract
Qoyjeh Yeylaq volcanic rocks is located approximately in the 120 km southwest of Zanjan, within the Central Iranian zone. The rock units in this area belong to the Cenozoic which consist of mainly Oligo-Miocene volcanic (Basaltic- andesitic lavas) and sedimentary rocks. Based on geochemical classification, ...
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Qoyjeh Yeylaq volcanic rocks is located approximately in the 120 km southwest of Zanjan, within the Central Iranian zone. The rock units in this area belong to the Cenozoic which consist of mainly Oligo-Miocene volcanic (Basaltic- andesitic lavas) and sedimentary rocks. Based on geochemical classification, the mentioned volcanic rocks are basalt, basaltic andesite and andesite in composition, and have calc- alkaline to high-K calc-alkaline affinity. In the primitive mantle normalized spider diagrams, all of the volcanic rocks show similar patterns with enrichment in LILE (Ba, Th, K, Pb) and negative anomalies of HFSE (Nb, Ti). These rocks show LREE enrichment relative to HREE and high ratio of LREE/HREE. Based on tectonomagmatic discrimination diagrams these volcanic rocks were formed in a continental arc setting. Based on geochemical data, it seems that volcanic rocks of the Qoyjeh Yeylaq area were formed from 5-20 % partial melting of a garnet- spinel lherzolite enriched mantle by subduction of Neo-Tethys under the central Iran, within the Orumieh- Dokhtar magmatic arc.
Economic Geology
Ali Rajabzadeh; Hossein Kouhestani; Mir Ali Asghar Mokhtari; Afshin Zohdi
Abstract
In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and ...
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In this study, petrography and major and minor elements geochemical data are presented for sandstone layers of the Upper Red Formation (URF) in the Chehrabad Pb-Zn deposit (NW Zanjan) to investigate sandstone composition, tectonic setting and their source rock. In this area, URF has 980 m thickness and is conformably overlies the Qom Formation limestones. Based on the microscopic studies, these sandstones mainly composed of fine- to coarse-grained clastic fragments including sedimentary and metamorphic rock fragments (45 %), quartz (38 %) and feldspar (17 %). Based on petrographic studies, these sandstones are feldspathic litharenite and litharenite (mainly chertarenite). Based on the main components and major and minor elements geochemical data, the tectonic setting of these sandstones is an active continental margins and foreland basins. These data represent an intermediate to felsic source rock for these sandstones which was affected by the semi-humid to semi-arid climate and a low chemical weathering.
Fariba Asiay Soufiani; Hossein Kouhestani; Amir Morteza Azimzadeh
Abstract
Qarachilar Cu-Mo-Au mineralization is located within the Qaradagh batholite in the Arasbaran metalogenic zone. This area is a part of southern margin of Lesser Caucasus. Qaradagh batholite at the Qarachilar mineralization area composed of granodiorite- quartz monzodiorite (as the main phase and host ...
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Qarachilar Cu-Mo-Au mineralization is located within the Qaradagh batholite in the Arasbaran metalogenic zone. This area is a part of southern margin of Lesser Caucasus. Qaradagh batholite at the Qarachilar mineralization area composed of granodiorite- quartz monzodiorite (as the main phase and host rock of mineralization), diorite, quartz monzonitic stocks, apophyses of porphyritic granite and acidic to intermediate dykes. These intrusions have Upper Eocene- lower Miocene age. All of the mentioned intrusion phases have calc-alkaline to high-K calc-alkaline nature and classified as metaluminous I-type granites. The porphyritic granite apophyses and dykes, and quartz monzonitic stocks have adakitic nature and can be classified as high silica adakites. Chondrite normalized REE patterns in granodiorites- quartz monzodiorites indicate enrichment in LREE and flat trend in MREE and HREE, while porphyritic granites show steep pattern with enrichment in LREE and depletion in HREE. Based on field investigation, geological, petrological, geochemical and tectonomagmatic discrimination diagrams, it can be conclude that granodiorite- quartz monzodiorite phase was formed in active continental margin as a result of Neo-Tethyan ocean subduction beneath the Eurasia. The quartz monzonite stocks and porphyritic granites were formed in a post collisional setting from metasomatized lithospheric mantle wedge.
Economic Geology
Fattaneh Pourmohammad; Hossein Kouhestani; Amir Morteza Azimzadeh; Ghasem Nabatian; Mir Ali Asghar Mokhtari
Abstract
Mianaj Fe ore occurrence is located in the Takab-Angouran-Takht-e-Soleyman metallogenic zone, 100 km southwest of Zanjan. In this area, Fe mineralization occurs as lens-shaped bodies parallel to the foliation of schist and rhyolitic meta-tuff units (equal to Kahar Formation). Based on mineralography, ...
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Mianaj Fe ore occurrence is located in the Takab-Angouran-Takht-e-Soleyman metallogenic zone, 100 km southwest of Zanjan. In this area, Fe mineralization occurs as lens-shaped bodies parallel to the foliation of schist and rhyolitic meta-tuff units (equal to Kahar Formation). Based on mineralography, ore mineral is magnetite, and quartz present as gangue mineral at Mianaj. The ore minerals show disseminated, laminated, banded, massive, vein-veinlet and replacement textures. Three stages of mineralization can be distinguished at Mianaj. The first stage is recognized as stratiform and stratabound lenses, laminated and disseminated crystals of magnetite parallet to the foliation of host rocks. Stage-2 mineralization is recognized by folding of ore bands, σ microfabric and boudinage of magnetite crystals, quartz pressure shadows and surrounding of foliation around magnetite crystals, and recrystallization of quartz and magnetite crystals. Stage-3 is recognized by quartz vein-veinlets that cut previous mineralization stages. Chondrite-nonmineralized REE pattern of host rocks and the mineralized samples indicate that mineralized samples are depleted in REE. This signature indicates mobility of REE by Cl and F-rich oxidized fluids during mineralization processes. Characteristics of Mianaj occurrence are comparable with metamorphosed and deformed volcano-sedimentary type of iron deposits.
Economic Geology
Hossein Kouhestani; Mir Ali Asghar Mokhtari
Abstract
Tashvir ore occurrence, 75 km northeast of Zanjan, is located in the Tarom-Hashtjin subzone. Mineralization occurs as ore-bearing quartz vein-veinlets within the Eocene tuffs and andesitic lavas (equal to Karaj Formation). Ore minerals include chalcocite, chalcopyrite and galena, and quartz, calcite ...
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Tashvir ore occurrence, 75 km northeast of Zanjan, is located in the Tarom-Hashtjin subzone. Mineralization occurs as ore-bearing quartz vein-veinlets within the Eocene tuffs and andesitic lavas (equal to Karaj Formation). Ore minerals include chalcocite, chalcopyrite and galena, and quartz, calcite and chlorite are present as gangue minerals at Tashvir. The ore show vein-veinlets, breccia, disseminated, replacement, relict, colloform, crustiform, dog tooth and plumose textures. Four stages of mineralization can be distinguished at Tashvir. These stages are progressed from quartz- chalcocite- chalcopyrite- galena‒cemented veins and breccias (stage-1), individual or sets of quartz veinlets (stage-2), and vug infill calcite (stage-3) and chlorite (stage-4) vein-veinlets. Hydrothermal alteration consist of silicified, argillic, carbonatic and chloritic. In the outer parts of the mineralization zones, alteration is propylitic. Similar REE patterns of the mineralized veins and the host rocks indicate they are genetically related. Enrichment of ore-forming elements (Ag, Cu, Pb, Zn) in ore zones is specifies leaching of elements from altered host rocks to ore zones. Characteristics of Tashvir ore occurrence are comparable with intermediate-sulfidation style of epithermal base metal (Ag) deposits. Mineralization at Tashvir and other epithermal deposits of the Tarom-Hashtjin subzone took place as a result of hydrothermal activity related to the late Eocene magmatism, and is controlled by fault systems. Therefore, investigation of the altered Eocene volcanic and volcano-sedimentary rocks, especially at the composite place of granitoid intrusions and along the fault structures, became the most favorable locus for epithermal ore bodies at Tarom-Hashtjin subzone.
M Ebrahimi; H Kouhestani; M.A.A Mokhtari; M Feizi
Abstract
The Aqkand area is located at 48 km north of Zanjan and is a part of the Tarom subzone within the Western Alborz-Azerbaijan structural zone. Acidic rocks exposed in this area consist of Oligocene rhyolite-rhyodacite, perlite, pitchstone and ignimbrite. Rhyolites and rhyodacites are exposed as domes and ...
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The Aqkand area is located at 48 km north of Zanjan and is a part of the Tarom subzone within the Western Alborz-Azerbaijan structural zone. Acidic rocks exposed in this area consist of Oligocene rhyolite-rhyodacite, perlite, pitchstone and ignimbrite. Rhyolites and rhyodacites are exposed as domes and lava flows. Perlites are located at the lower parts of the rhyolitic-rhyodacitic domes. Geochemical investigations indicate calc-alkaline nature along with magmatic arc affinity for the studied rocks. These rocks are characterized by LREE-rich patterns with high LREE/HREE ratio and distinctive negative Eu anomaly. Positive anomalies of Rb, Pb and Th on the spider diagrams suggest continental crust involvement in the genesis and evolution of the parental magma. Based on tectonic setting discrimination diagrams, Aqkand acidic rocks are plotted in the post-collision tectonic setting. In overall petrographic, petrologic and geochemical evidence demonstrate that during the final stages of the continental collision, the thickened sub-continental lithosphere in the Alborz was delaminated and replaced by hot asthenospheric mantle. Rapid upwelling of hot asthenosphere gave rise to the partial melting of sub-continental lithosphere which produced the Oligocene basaltic rocks of the study area. Emplacement of basaltic magma in the upper part of the continental crust led to the partial melting of the crust and generation of the acidic magmas. Rapid cooling of acidic lavas led to the generation of glassy rocks such as obsidian which are changed to perlite in contact with meteoric and warm waters.
Economic Geology
R. Amirkhani; M. Ebrahimi; M. A. A. Mokhtari; A. M. Azimzadeh
Abstract
The study area which is introduced as Homeijan magnetite- apatite mineralization in this paper, is a part of the Posht-e-Badam block in the Central Iranian Zone and is located at ~12Km southwest of Behabad. This area is composed of volcano-sedimentary rocks and acidic- basic intrusions of Precambrian ...
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The study area which is introduced as Homeijan magnetite- apatite mineralization in this paper, is a part of the Posht-e-Badam block in the Central Iranian Zone and is located at ~12Km southwest of Behabad. This area is composed of volcano-sedimentary rocks and acidic- basic intrusions of Precambrian and Cambrian age. Magnetite- apatite mineralizations are present as lenses near the southwestern part of the Homeijan village, which are hosted by acidic- intermediate tuffaceous rocks and dolomites. Magnetite, oligist (hematite), pyrite and chalcopyrite are the main ore minerals and apatite, pyroxene, tremolite- actinolite, calcite and quartz are as gangue minerals in the Homeijan Fe mineralization. Based on field and mineralogical studies, this mineralization texturally includes massive, brecciated, vein- veinlets and replacement textures. Chemical analyses of samples indicate that the mineralization has high concentrations of REEs up to 2.5 % in the apatite crystals. Geochemical studies demonstrate that Fet have high negative correlation with P2O5, SiO2 and ∑REE while there is a high positive correlation between ∑REE and P2O5. SEM-EDS qualitative analyses of apatite crystals indicate two REE bearing minerals including monazite and allanite as inclusions within the apatites. Furthermore, this study demonstrates that the apatite crystals are flour- apatite. Fluid inclusion studies within the apatite crystals indicate that main salinity varies between 7.86-13.9 wt.% NaCl and homogenization temperature is between 240-370°C. Comparing of REE patterns of Homeijan magnetite- apatite mineralization with other iron oxide- apatite mineralizations of Posht-e-Badam Block and Kiruna- type iron ores indicate similarities between these patterns. Generally, based on field and geochemical studies, the Homeijan magnetite- apatite mineralization classified as Kiruna- type Fe deposit.
M.A.A Mokhtari; H Kouhestani; A Saeedi
Abstract
Aliabad Mousavi- Khanchy Cu occurrence is located in the Tarom area, 30 km east of Zanjan. Rock units exposed in this area consist of Eocene volcanic and volcano-sedimentary units (equal to Karaj Formation) which are intruded by Oligocene quartz-monzonitic plutons. In this area, Cu mineralization occurs ...
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Aliabad Mousavi- Khanchy Cu occurrence is located in the Tarom area, 30 km east of Zanjan. Rock units exposed in this area consist of Eocene volcanic and volcano-sedimentary units (equal to Karaj Formation) which are intruded by Oligocene quartz-monzonitic plutons. In this area, Cu mineralization occurs as Cu-bearing quartz veins and veinlets within the intermediate tuffs and andesitic lavas. Based on microscopic studies, ore minerals are include chalcopyrite with minor pyrite and oligist, and quartz and chlorite are present as gangue minerals at the Aliabad Mousavi- Khanchy Cu occurrence. The ore minerals show disseminated, vein and veinlets, breccia, open space filling and replacement textures. Alteration is restricted to the silicified and chloritic altered parts of the ore zones. Two stages of hypogene and supergene mineralization can be distinguished at the Aliabad Mousavi- Khanchy Cu occurrence. The hypogene stage of mineralization is progressed from disseminated crystals of pyrite and chalcopyrite within the tuffs and lavas (substage 1) to quartz- chalcopyrite- pyrite‒cemented veins and breccias (substage 2), individual or sets of quartz veins and veinlets (substage 3) and finally quartz- oligist veins and veinlets (substage 4). Malachite, azurite and Fe-hydroxides with veins and veinlets and open space filling textures are formed during supergene stage. REE pattern of the host rocks and the mineralized samples indicate that mineralized samples are enriched in REE. This signature may indicates high concentration of REE in ore-forming fluids and/or high W/R interaction at Aliabad Mousavi- Khanchy area. Enrichment of ore-forming elements (Cu, Pb, Zn) in ore zones is also specifies leaching of elements from altered host rocks to ore zones by ore-forming fluids. Characteristics of Aliabad Mousavi- Khanchy Cu occurrence are comparable with vein type of Cu deposits.
S Enayati Kolaie; M Yazdi; M.A.A Mokhtari
Abstract
Tazeh-Kand Cu mineralization area is located in ~20 km northeast of Tabriz, eastern Azarbaijan province. The area is a part of Central Iranian geo-structural zone in the eastern margin of the Tabriz 1:100000 geological map. Lithological units in this area composed of green- grey sandstones (redox zone), ...
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Tazeh-Kand Cu mineralization area is located in ~20 km northeast of Tabriz, eastern Azarbaijan province. The area is a part of Central Iranian geo-structural zone in the eastern margin of the Tabriz 1:100000 geological map. Lithological units in this area composed of green- grey sandstones (redox zone), red sandstones and marl (oxidized zone), salt domes and conglomerate (Miocene) along with dacitic domes (Pliocene). Based on petrographical investigations, the host sandstones are sub- mature to immature lithic arkos and were deposited in a tidal environment. Cu mineralization in this area occurred as stratiform type within the redoxed sandstones. The thickness of mineralized horizons vary between 30cm to 1m which are crops out up to 500m in some horizons. Concentration of Cu mineralization has direct relation with organic matter concentration. Mineralized horizons composed of three zones include: mineralized redox zone, bleached zone and red oxidized zone. Mineralogical investigations show that this mineralization composed of primary sulfide minerals include pyrite, chalcocite and digenite along with supergene minerals include covellite, malachite and Fe- hydroxides. Texturally, these minerals present as lenticular, disseminated, replacement, inter- grain cement and solution seems textures. According to petrographical and mineralogical results such as pyrite and primary chalcocite bearing redox sandstone, structural and textural evidences, stratigraphy, mineralization controlling factors, presence of organic matter as a redox material, permeability of host rock and salt diapirism, mineralization in the Tazeh-Kand area is mostly similar to RedBed type mineralization which is formed during the early to late diagenesis.
F Mohamadi; M Ebrahimi; M.A.A Mokhtari
Abstract
The study area,~12 km to the southwest of the city Behabad, is a part of the Posht-e-Badam Block in Central Iran. Igneous rocks in the area occur as intrusive, sub-volcanic and volcanic bodies and exhibit a wide range of composition from felsic to mafic. The intrusive and sub- volcanic rocks include ...
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The study area,~12 km to the southwest of the city Behabad, is a part of the Posht-e-Badam Block in Central Iran. Igneous rocks in the area occur as intrusive, sub-volcanic and volcanic bodies and exhibit a wide range of composition from felsic to mafic. The intrusive and sub- volcanic rocks include the relatively large Homijan granitoid, Ferdows granitoid, gabbro- diorite stocks and Kuh-Siah sub- volcanic rhyolitic dome. The Homijan granitoid is composed of a shallow-level intrusion in the center to rhyolitic lavas and tuffs in the margins. The whole assemblage is covered by dolomites of the Rizu series, with no thermal metamorphism in the covering rocks. Homijan granitoid displays porphyritic, porphyroid and graphic textures composed of coarse plagioclase, alkali feldspar and quartz in a fine- grained quartz- feldspatic matrix; the marginal rhyolitic lavas have porphyritic and spherolitic textures with quartz and alkali feldspar phenocrysts. Rhyolitic tuffs have porphyroclastic texture. Ferdows granite has hetero-granular, graphic and perthitic texture composed of quartz, orthoclase and plagioclase. Kuh-Siah rhyolites have porphyric, felsophyry and felsitic textures with small quartz and alkali feldspar phenocrysts. Geochemical studies demonstrate that Homijan and Ferdows granitiods and the marginal rhyolites of the Homijan, as well as the Kuh-Siah rhyolitic dome have high- K calc- alkaline to shoshonitic nature and can be classified as S-type peraluminous granitoids with some tendency to I-type granitoids. Based on the spider diagrams, all rocks have similar trend which is indicative for their genetic relation. These diagrams indicate enriched LILEs (Rb, K, Th and Pb) along with negative anomalies of HFSEs (Nb and Ti). Chondrite normalized REE patterns demonstrate LREEs-enriched patterns with high ratios of LREE/HREE.The positive and negative anomalies of the mentioned elements in the studied rocks probably are related to lower partial melting degrees of a metasomatized mantle along with crustal contamination of the magma. Based on field investigation, petrographic studies and geochemistry, and using the granitoid discrimination tectonic setting diagrams, it seems that Homijan granitiods and related felsic rocks formed in a post- collisional setting within the Posht-e-Badam Block.
M Lotfi; M Hekmatian; A.A Shabani; M.A Mokhtari
Abstract
Oras-kuh lead-zinc deposit is located at about 79 km north-east of Semnan city. This deposit is considered as stratabound and occurs in the upper part of the Triassic dolomitic limestone of the Elika formation. Oras-kuh structure includes a northeast - southwest trending normal anticline and follows ...
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Oras-kuh lead-zinc deposit is located at about 79 km north-east of Semnan city. This deposit is considered as stratabound and occurs in the upper part of the Triassic dolomitic limestone of the Elika formation. Oras-kuh structure includes a northeast - southwest trending normal anticline and follows the general trend of the eastern Alborz. Folding in the area has generatedthree sets of jointsincludingjoints trending parallel to the direction of anticline axis, extensional joints perpendicular to anticline axis and the conjugate joint systems. The first two setsof the joints host vein form mineralization. In addition, breccia and karst filling mineralization can be detected. Major minerals are galena, sphalerite and pyrite that altered to secondary minerals such as cerussite, goethite, hydrohetarolite and rosasite under the supergene processes. Gangue minerals are dolomite, calcite, barite, quartz, and small amounts of fluorite. The majority of the temperature data are between 298 to 323°C based on the fluid inclusion geothermometry of calcite and barite minerals. The relatively high temperatures of fluid inclusions are attributed most likely to a concealed deep intrusion in the crust inferred byairborne geomagnetic survey. Fluid salinities show a wide range from 0.6 to 15wt% equivalent weight of NaCl formed through mixing of basinal brines with meteoritic water. In general based on the present evidences, Oras-kuh lead-zinc deposit can be comparable with MVT deposits that its primary mineralogy and elemental ratios have been changed through secondary supergene processes.
M.R Omidvar Eshkalak; A.A Mokhtari
Abstract
The studied area is located in the southeastern end of the Sahand- Bazman Magmatic Belt in the north of Bazman volcano. This area composed of Miocene volcanic rocks including andesitic to dacitic lavas along with tuffaceous sandstone, ignimbrite, agglomerate, tuff and siltstone that underwent propyilitic, ...
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The studied area is located in the southeastern end of the Sahand- Bazman Magmatic Belt in the north of Bazman volcano. This area composed of Miocene volcanic rocks including andesitic to dacitic lavas along with tuffaceous sandstone, ignimbrite, agglomerate, tuff and siltstone that underwent propyilitic, argillic, sericitic, carbonatic and silicified alterations. Predominant form of the mineralization is silica veins and hydrothermal breccia, which crop out within the alteration zones. The textures within the silica veins include coliform, vuggy, stratiform, banded and hydrothermal breccias. The results of sample analysis demonstrate that hydrothermal breccias have the highest grades of Au (up to 27.6 ppm), and the silica veins with banded texture and fine grained sulfide bearing silica veins are other important Au- bearing mineralization in the next orders. The geochemical investigations demonstrate good positive correlation between Au and Ag, Sb, As, Pb, Zn, Mo, Bi and Hg in the Au- bearing silica veins. The fluid inclusion studies on silica veins with banded texture indicate that the salinity of fluids is 1.22-7.77 W% NaCl, and homogenization temperature is 190-296◦C. Based on the field evidences along with mineralogy, textures and structures of silica veins, geochemical and fluid inclusion investigations, the Au mineralization in the north of Bazman can be classified as low sulfidation epithermal gold deposits.
Z Miriyan; M Lotfi; A.A Shabani; M.A.A Mokhtari; E Haj Molla Ali
Abstract
The Kharengun area is located in the Yazd province, Central Iran, 130 km east of Yazd city and 65 km northeast of Bafq city. Mineralization in Kharengun area occurred within calcic and dolomitic units of the Rizou Formation (equivalent to Soltaniyeh Formation) of upper Precambrian- lower Cambrian age. ...
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The Kharengun area is located in the Yazd province, Central Iran, 130 km east of Yazd city and 65 km northeast of Bafq city. Mineralization in Kharengun area occurred within calcic and dolomitic units of the Rizou Formation (equivalent to Soltaniyeh Formation) of upper Precambrian- lower Cambrian age. The ore minerals of this deposit includes smithsonite and hemimorphite, that is stratabound and formed epigenetically along layers and laminations of carbonate host rocks. The maximum grade of zinc in samples taken from the study area exceeds 36% and geochemical studies indicate significant absence of Pb along with Zn in this area. Therefore, the Kharengun mineralization is a monomineral Zn zone.The fluid inclusion microthermometry investments explain the role of meteoric waters in generation of this deposit. The homogenization temperatures and salinity of the inclusions show the similarity between these fluids and the solutions responsiblefor the development of epithermal deposits.The Zn mineralization present in this zone belongs to the nonsulfide supergene deposit class, and a mixture of wallrock replacement and direct replacement subclasses.
M.R Omidvar Ashkalack; A Khakzad; N Nezafati; M.A.A Mokhtari; B Borna; S Rozbeh Kargar
Abstract
The studied area is located in the western part of the Central Alborz structural zone and contains a bauxitic- lateritic horizon between the Elika and Shemshak formations. This horizon belongs to the middle Triassic, and croups out with E-W trend in the four regions (trends) including Zard Kuh- Loriteh, ...
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The studied area is located in the western part of the Central Alborz structural zone and contains a bauxitic- lateritic horizon between the Elika and Shemshak formations. This horizon belongs to the middle Triassic, and croups out with E-W trend in the four regions (trends) including Zard Kuh- Loriteh, Shagol- Sangrood, Abasak- Hir, and Arsheh Kuh- Zakabar. The complete cross section of bauxitic- lateritic horizon contain dark grey pisolites in the lower part, yellowish red laterite in the middle part, and an upper part with light grey color. Kaolinite and quartz are the main mineral components of this horizon. The minerals such as diaspore, bohemite, anatase, hematite and goethite present as minor phase. The grey- colored upper and lower parts contain high grade of Al2O3 and low grade of Fe2O3 while in the middle part, high grade of Fe2O3 and low grade of Al2O3. The average grades of Al2O3, Fe2O3, SiO2 and TiO2 in the samples are in turn 35%, 14%, 35% and 5%. The maximum grades of Al2O3 in the mentioned four trends are 51%, 61%, 48% and 48%. There is a distinctive negative correlation between Al2O3 and Fe2O3, between Fe2O3 and SiO2, and between Fe2O3 and TiO2. Furthermore, there is a positive correlation between Al2O3 and TiO2. The results of laboratory investigations indicated that the best bauxitic- lateritic horizon in the studied area considering grades of major oxides is the Abasak- Hir trend.
M.A.A Mokhtari; H Moinvaziri2; M.R Ghorbani; M Mehrpartou
Abstract
Au-Cu-Mo mineralization of Aniq-Qarachilar area is located in Arasbaran ore zone within the Qaradagh batholith. Mineralization in this area mainly includes Au-Cu-Mo bearing quartz veins within the granodiorite that cropped out in three areas include: Qarachilar (2 major veins), Zarlidareh (8 veins) and ...
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Au-Cu-Mo mineralization of Aniq-Qarachilar area is located in Arasbaran ore zone within the Qaradagh batholith. Mineralization in this area mainly includes Au-Cu-Mo bearing quartz veins within the granodiorite that cropped out in three areas include: Qarachilar (2 major veins), Zarlidareh (8 veins) and Qaradareh (some narrow and short veins). Alterations around the quartz veins include sericitic and silisification that has limited development. Quartz veins have compact, boxwork and brecciated texture. Sheeted veins of quartz present in some areas especially in the Qarachilar area. Sulfide mineral content of these veins commonly less than 10 percent and includes pyrite, As- bearing pyrite, chalcopyrite, molybdenite, bornite, stibnite, sphalerite and galena. Secondary minerals include coveline, malachite, azurite and iron hydroxides. Geochemical studies and grades of elements indicate that Au, Ag, Cu and Mo have high content in quartz veins. The average grade for Au in two quartz veins in the Qarachilar area is 5.76 and 3.9 ppm. The average grade for Au in the quartz veins in the Zarlidareh area is 4.7, 3.12, 2.6, 0.45, 1.09, 1.34, 1.15 and 0.58 ppm. The highest Au grade is about 359 ppm that belongs to a quartz vein with boxwork texture in the Zarlidareh area (ZV1). Moreover, W and Bi have high concentration in some veins. There is a good correlation between Au and Ag, Mo, W and Bi. Au grades in the Qaradareh quartz veins is low, but Mo grades vary between 0.15- 1.15%. Mineralization as silisic sheeted veins within the granodioritic intrusion, low concentration of sulfide minerals within the quartz veins, limited alteration aureole, Au mineralization together with Mo mineralization and high concentrations of Bi and W and relatively good correlation of Au with Ag, Bi, W and Mo indicate that Au mineralization in the Aniq-Qarachilar area can be classified as an intrusion related gold systems.
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.
M .A. Mokhtari; H. Moein Vaziri; M.R. Ghorbani; M. Mehr Parto
Abstract
Kamtal intrusion is located in East Azarbaijan province, NW of Iran, near the Armenia border. The Kamtal intrusion consist of an acidic part with monzogranitic composition and an intermediate- basic part which compositionally composed of monzonite, monzodiorite, quartz monzonite, quartz monzodiorite ...
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Kamtal intrusion is located in East Azarbaijan province, NW of Iran, near the Armenia border. The Kamtal intrusion consist of an acidic part with monzogranitic composition and an intermediate- basic part which compositionally composed of monzonite, monzodiorite, quartz monzonite, quartz monzodiorite and gabbro. Gabbroic rocks exist in the form of small lenses in the southeast of Kamtal intrusion within the intermediate part. The intermediate- basic part has been intruded by the acidic part. Both acidic and intermediate parts are high-K calc-alkaline, metaluminous in character and classified as I-type granitoids; while, the gabbros have tholeiitic nature.
Both acidic and intermediate rocks show a LREE rich pattern and high LREE/HREE ratio. These two parts have differences in MREE enrichment. From similarity in REE patterns of acidic and intermediate rocks a genetic relation can be discerned. Negative anomalies of Nb and Ti can be seen in all rock phases of the Kamtal intrusion, representing the subduction zone setting. Comparison of trace element variations with those of granitoid rocks of different tectonic settings show similarities between Kamtal intrusion and Andean volcanic arc granitoids. Furthermore, Kamtal intrusion can be classified as VAG based upon tectonic setting discrimination diagrams. It is concluded that, Kamtal intrusion probably is the result of Neotethys oceanic crust subduction beneath the Caucasus continental plate.
