Petrology
Leila Maleki; Nematollah Rashid Nejad-e-Omran; Abdolrahim Houshmandzadeh; John Cottle
Abstract
In this article, metabasic and gneissic rocks of Gelmandeh and Zamanabad mountain (Boneh-Shurow complex, Saghand region) have been used for U-Pb dating. Analyses of zircon crystals yielded concordant U–Pb ages with weighted mean 206Pb/238U ages of 545.4 ±3.6 Ma (MSDW=1.7) for garnet amphibolite, ...
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In this article, metabasic and gneissic rocks of Gelmandeh and Zamanabad mountain (Boneh-Shurow complex, Saghand region) have been used for U-Pb dating. Analyses of zircon crystals yielded concordant U–Pb ages with weighted mean 206Pb/238U ages of 545.4 ±3.6 Ma (MSDW=1.7) for garnet amphibolite, 541.2 ± 4.4 Ma (MSDW=1.8) for metagabbro, 541.3 ±3.5 Ma (MSDW=0.26) for quartz-feldspatic gneiss and 549.2 ± 2.6 Ma (MSDW=0.28) for amphibole- biotite gneiss. The studied zircon crystals has continental, crustal nature and show a strong affinity to magmatic zircons in Chondrite-normalized patterns. The ages that approximately ranges between 541-549 Ma are interpreted as the Crystalline age of the garnet amphibolite and gneissic parental magma. These ages previously assumed as the timing of peak-metamorphism of the Boneh-Shurow garnet-amphibolite and emplacement ages for the granitic precursor of gneissic rocks.
Economic Geology
Monireh Sakhdari; Mehrdad Behzadi; Mohammad Yazdi; Nematollah Rashidnejad-Omran; Morteza Sadeghi Naeini
Abstract
The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences ...
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The Godar Sorkh area is located in the central part of the Sanandaj-Sirjan zone, 20 km southwest of the Muteh region. Gold mineralization at Godar Sorkh occurs in quartz-sulfide veins that hosted in metasedimentary rocks. Veins of mineralization typically formed along normal faults. Rock sequences are affected by several deformation phase, gold mineralization occurs in ductile to ductile-brittle shear zones and had been under poly-phase metamorphism. The main alterations are Sulfidation, carbonization, silicification, chloritization, and sericitization. Ore-mineral assemblages include pyrite and chalcopyrite, arsenopyrite, sphalerite, galena, and Fe-oxide. Mean homogenization temperature in gold-bearing quartz range between 275oC and 300oC. Fluid inclusions in quartz veins are dominated by CO2-H2O-NaCl fluid. Salinity ranges from 9 to 17 wt. % NaCl equivalent. Corresponding to a depth of <2 km, Godar Sorkh deposit is formed in epizonal environment. Measured δ18O values for the gold-bearing quartz range between 12.7 to 14.3 permil, estimated δ18Ofluid values range from +6.4 to +7.3 permil, δ34S values range from –16 to +5 permil, and estimated δ34Sfluid values range from +4.2 to -17.3 permil. Fluid inclusion and stable isotope studies on ore-bearing quartz-sulfide veins indicating the major role of metamorphic fluids. Gold derived from metasedimentary rocks. Gold mineralization in the Godar sorkh deposit classified as an orogenic gold deposit.
Petrology
Ziba Khodaean Chegeni; Nematollah Rashidnejad Omran; Ali Akbar Baharifar; Reza Nozaem; Carmela Vaccaro; José Francisco Santos
Abstract
Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or ...
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Takhte-Soleyman ortho-amphibolites as a part of Takab metamorphic complex are located in Northeast Takab. These rocks consist of amphibolite, Garnet-amphibolite, Kyanite-Garnet-amphibolite, Hornblendite and Epidote-amphibolite. Petrography and whole- rock geochemistry show that basalt, andesite and/or their intrusive equivalents with calc- alkaline to tholeiitic affinity and even a peridotite could be their protoliths. Trace element and Sr-Nd ratios imply that these rocks were from mantle melt sources. In chondrite normalized plots, these amphibolites can be classified into at least two groups. The first group is characterized by LREE depletion relative to HREEs and some with flat patterns. The second has an enrichment of LREEs relative to HREEs. These two different patterns and some other geochemical characters suggest MORB or MORB-like and arc affinities of the parental magmas. This can be related to the time progressive evolution of magmatism either from MORB or Back-arcto Arc or from Arc to Back-arc setting.
Petrology
Leila Maleki; Nematollah Rashidnejad Omran; Abdolrahim Houshmandzadeh
Abstract
Boneh shurow metamorphic complex is located in the east of Saghand area, Central Iran. This complex consists of quartz-feldspatic gneiss (mafic minerals < 5%), biotite-amphibole gneisses, metabasics rocks, schists, subordinate dolomitic marble and quartzite interlayers and mafic and felsic magmatic ...
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Boneh shurow metamorphic complex is located in the east of Saghand area, Central Iran. This complex consists of quartz-feldspatic gneiss (mafic minerals < 5%), biotite-amphibole gneisses, metabasics rocks, schists, subordinate dolomitic marble and quartzite interlayers and mafic and felsic magmatic intrusions that they have been retrogressed to lower amphibolite facies. In MORB-normalized plots, the metabasic samples can be classified into two groups: first group does not display Nb-Ta anomaly and second group displays negative Nb-Ta anomaly. Whole rock geochemistry and Sr– Nd isotopic composition of metabasic unites suggest derivation from two different mantlic sources in the back arc setting. A source enriched in Ti, such as plume tail, and an old enriched mantle that has been affected by subduction, can be involved in generation of the first and second group, respectively
H. Rahbari; N. A. Rashidnejad Omran; M. Khalatbari-Jafari
Abstract
As a part of Takab Metamorphic Complex (TMC), Belqeis Mountain has a variety of metamorphic rocks including orthogneiss, pelitic schists, meta-ultramafics and mafic rocks and dolomitic marbles. This complex was metamorphosed, faulted and folded during Late Neoproterozoic-Early Cambrian ...
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As a part of Takab Metamorphic Complex (TMC), Belqeis Mountain has a variety of metamorphic rocks including orthogneiss, pelitic schists, meta-ultramafics and mafic rocks and dolomitic marbles. This complex was metamorphosed, faulted and folded during Late Neoproterozoic-Early Cambrian Pan-African orogeny and invaded by granitoid pertinent to the subduction of the Neo-Tethys oceanic crust beneath the Iranian crust during Tertiary. Geochemically, the protolith of orthogneiss of Belqeis Mountain is high K and has calc-alkaline affinity and both fractional crystallization and magma mixing have been incorporated significantly to produce the protolith of them. The pattern of trace elements normalized to chondrite and primitive mantle points to enrichment in LILE and LREE, depletion of HFSE and HREE and shows negative anomalies in Eu, Ba, Nb, Sr, Ti and P. Depletion in HFSE was accompanied with enrichment of LILEs and LREEs indicating the generation of protolith in subduction setting related to active continental margins. Tectonic discrimination diagrams suggest a combination of volcanic arc and continental collision settings for the studied samples. There are many evidence including La/Nb>1 and relatively high values of several ratios such as Zr/Nb (14.7), Th/Nb (1.5), Ba/Nb (58), La/Nb (3), Ti/Zr (14.9), Nb/Ce (0.24) and (La/Sm)n (3.76),close to crust values, confirming that mantle was not incorporated solely but both crust and mantle sources were contributed in origin of these rocks. All aforementioned points in addition to occurrence of paleo-suture zone and ophiolitic rocks (i.e. serpentinites, meta-mafic and meta-ultramafic rocks) around these medium to high grade metamorphic rocks confirm that subduction of an oceanic lithosphere followed by collision in the study area.
B. Shahsavari Alavijeh; N. Rashidnejad Omran; J. Ghalamghash
Abstract
The Nodoushan intrusive complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt (UDMB). This complex consists of four main intrusives, including diorite, granite-granodiorite, diorite porphyry and granodiorite. Mafic microgranular enclaves ...
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The Nodoushan intrusive complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt (UDMB). This complex consists of four main intrusives, including diorite, granite-granodiorite, diorite porphyry and granodiorite. Mafic microgranular enclaves (MMEs) are abundant in the diorite porphyry and granodioritic intrusives and also in some parts of Granitegranodiorite intrusives, which consist of diorite, monzodiorite and rarely gabbro -diorite. According to geochemical data, the Nodoushan intrusive complex is metalominous to moderately peraluminous, I-type and shows medium to high potassium calc-alkaline affinity. Geochemical investigations show that contamination and mafic-felsic magma mixing played significant role in the evolution and petrogenesis of the mentioned intrusions magmas and formation of MMEs. Using U-Pb zircon dating method, the obtained magma crystallization ages are about 30 Ma for the dioritic and granite-granodiorite intrusives, 24 Ma for the diorite porphyry and 25 Ma for the granodioritic intrusives. In addition, the age for part of the granite-granodiorite unit that is located in the northeast corner of the region, at the north of the Nain-Dehshir fault (NDF) and the western part of the Central Iranian Microcontinent (CIM), was determined 40 Ma. The geochemical evidences suggest that the studied intrusions magmas were derived from partial melting of continental crust caused by the mantle melts in an active continental margin. It seems that the melting of rocks with combination of metabasalt and metagraywacke in the lower crust in balance with the residual consisting of clinopyroxene, amphibole and to a lesser extent plagioclase; have the greatest harmony with geochemical characteristics of the studied intrusions.
T Salehi; M Ghaderi; N Rashidnejad-Omran
Abstract
Gomish-Tappeh Zn-Pb-Cu (Ag) deposit is located in northwestern part of Urumieh-Dokhtar volcano-plutonic zone, 90 km southwest of Zanjan. Exposed rocks at the area include Oligo-Miocene volcano-sedimentary and sedimentary sequences as well as Pliocene dacitic subvolcanic dome, rhyodacitic volcanics and ...
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Gomish-Tappeh Zn-Pb-Cu (Ag) deposit is located in northwestern part of Urumieh-Dokhtar volcano-plutonic zone, 90 km southwest of Zanjan. Exposed rocks at the area include Oligo-Miocene volcano-sedimentary and sedimentary sequences as well as Pliocene dacitic subvolcanic dome, rhyodacitic volcanics and andesite porphyry dykes. The main mineralization at Gomish-Tappeh deposit has occurred in a steeply deeping normal fault and fracture system defined by NE-SW trend in three stages including hydrothermal breccias, silicic-sulfidic, silicic-sulfidic-carbonate veins and veinlets and late banded veins (rich in silica and specularite). Host rocks to mineralization include dacitic crystal lithic tuff, dacitic subvolcanic dome, and specifically acidic tuff. Paragenetic minerals at the deposit consist of pyrite, arsenopyrite, chalcopyrite, bornite, galena, low-Fe sphalerite, tetrahedrite, tennantite and specularite. The main alteration types at the area are silicic, silicic-sulfidic, sericitic, carbonate, argillic and propylitic. Based on element distribution and frequency patterns in the ore samples, among base metals, Zn, Pb, Cu and Ag show the highest concentrations. Average grades in the ore veins at Gomish-Tappeh deposit are: 6% Zn, 4% Pb, 2% Cu, 88 ppm Ag and 44 ppb Au. Fluid inclusion microthermometric studies on quartz crystals of the first and second stages of mineralization indicate homogenization temperatures of 260-367 °C, salinities of 9.1-16.9 wt% NaCl equiv., and approximate mineralization depth of 956 m below the paleowater table. Considering high salinity fluids and base metal contents, it is likely that base metals and silver were transported by chloride complexes. Fluid inclusion studies, hydrothermal breccias, banded-colloform-crustiform textures and amorphous silica indicate that boiling is the main factor for instability of the complexes and eventually, ore deposition.
S. M Masoudi; E Ezati; N Rashidnejad Omran
Abstract
Before the Cold War, strategic materials supply and studies related to them were more affected by military competition between East and West, the example was the assessment of the geopolitical risk factors by Anderson for the North Atlantic Treaty Organization. But after the Cold ...
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Before the Cold War, strategic materials supply and studies related to them were more affected by military competition between East and West, the example was the assessment of the geopolitical risk factors by Anderson for the North Atlantic Treaty Organization. But after the Cold War and the collapse of the Berlin Wall in 1989 and the development of Chinese economy, more and more Western countries were concerned of the vulnerability against the suppliers of minerals. The main reason for it is geopolitical developments and turning of militarism and Geostrategy to Geoeconomics and priority the economy. The methods of assessment the post-Cold War based on confrontation between the north and south and provide more economic security or economic power and provide needed goods and protection of the environment. New methods started with research of the National Council of United States of America by novation the criticality matrix with two-dimensional in economic importance and supply risk, and Graedel studies was actually follow its principles. According to investigations of Geological Survey and Department of Defense in the United States and the European Union and German industry represent fluorspar is strategic mineral in the world. Economic value of fluorspar is used in the production of steel, aluminum, hydrofluorocarbon, Teflon, new and clean energy. In this research with investigations of fluorspar producer countries in the last fifteen years, however, Iran has achieved tenth grade with one percent, but still one of the main importers of intermediate goods made of this mineral is between neighboring countries. Therefore, the first step is essential the investment for systematic and in-depth exploration in the country and especially in the central Alborz, with the goal of increasing fluorspar reserves and supply raw materials for the aluminum industry of the country. The industrial that south competitors of Iran, due to the low cost of energy in the region, have been activated by investing in it seriously.
M Fereidoni; M Lotfi; N Rashid nejad; M Rashidi
Abstract
The Qalikuh area,~35 km southwest of Aliqudarz, contains oil shale deposits in Garue and Sargelu formations(Jurassic-Cretaceous). Some 20 samples across two sections(Charun3-Deh ye Qali3) were selected and analyzed(Rock Eval – ICP – XRD – XRF) to study organic and mineral parameters(to ...
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The Qalikuh area,~35 km southwest of Aliqudarz, contains oil shale deposits in Garue and Sargelu formations(Jurassic-Cretaceous). Some 20 samples across two sections(Charun3-Deh ye Qali3) were selected and analyzed(Rock Eval – ICP – XRD – XRF) to study organic and mineral parameters(to determine type of organic material and kerogen, total organic carbon, thermal evolution, concentration, and classification of elements and minerals) and to model the relations between these parameters. The Qalikuh oil shale has a great potential for oil production with high levels of TOC (13.5 wt%), type 2 kerogen, low thermal maturity. However Qalikuh oil shale has metallic and nonmetallic element anomalies and high concentrations of strategic elements compared to Clark values. Dendritic diagrams suggest variable origins for elements and minerals in the samples. Some are associated with development of organic materials, TOC parameters, Resin and Asphaltene, and some are associated with clastic materials, aluminosilicates and source rock weathering.
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.
M Abolipour; E Rastad; N Rashidnejad Omran
Abstract
The Koshkoiye district is located in Dehaj-Sardoiye subzone of Uromieh-Dokhtar Magmatic Arc in Kerman region. There are five active mines including Palangi, Cheshmeh Khezr, Tale Dozi, Abedini, and Eghbali. The geometry of mineralization is strata-bound and hosted in the Eocene Pyrobitumen-bearing porphyritic ...
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The Koshkoiye district is located in Dehaj-Sardoiye subzone of Uromieh-Dokhtar Magmatic Arc in Kerman region. There are five active mines including Palangi, Cheshmeh Khezr, Tale Dozi, Abedini, and Eghbali. The geometry of mineralization is strata-bound and hosted in the Eocene Pyrobitumen-bearing porphyritic andesite. Bornite, chalcocite and chalcopyrite are important Cu-sulfides together with hematite. The textures and structures of mineralization are open space filling, disseminated, vein-veinlet and replacement. According to geochemical study, tectonic setting of Koshkoiye copper district is extensional back-arc, which generated together with subduction of the Dehaj-Sardoiye subzone. Abundant of Cu, Pb and Ag elements is up to 600, 5 and 2 ppm in fresh porphyritic andesite. Fluid inclusion microtermometry indicates probably basinal brine source for ore-forming fluids. The copper mines in the Koshkoiye district have a lot of similarity in mineralogy, minor element, host rock, textures and structures, geometry and genesis with each other and the Manto-type copper mineralization of the world. This type of copper mineralization in the Koshkoiye district of Rafsanjan indicates the importance of volcanic processes in copper mineralization plus plutonic processes that produces porphyry systems in the Dehaj-Sardoiye subzone. The presence of pyrobitumen in porphyritic andesite host rock causes these deposits exposure in a few pyrobitumen-bearing andesitic hosted copper deposits of the world. There are only a few of these deposits in the world and dominantly located in Chile. Two important stages could be separated for mineralization in these deposits like the other Manto-type copper mineralization. The first stage includes processes, which caused to generate pyrite and pyrobitumen in matrix of porphyritic andesite and produced a reduction state in it. The Second stage was related to importance of generation of the Cu-rich oxidation fluids, which replaced the first stage pyrite and pyrobitumen by Cu-sulfides and hematite and caused copper mineralization.
S Ghaderi; E Rastad; N Rashidnezhad-Omran
Abstract
Tungsten (Cu-Au) mineralization of Southern Chah Palang (SCP) deposit, located in middle part of the Yazd block, occurred as vein-veinlet in normal fault zones, which cut the sandstones and shales of Early-Middle Jurassic Shemshak formation. Based on the mineral paragenesis and quartz type, color and ...
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Tungsten (Cu-Au) mineralization of Southern Chah Palang (SCP) deposit, located in middle part of the Yazd block, occurred as vein-veinlet in normal fault zones, which cut the sandstones and shales of Early-Middle Jurassic Shemshak formation. Based on the mineral paragenesis and quartz type, color and texture, ore-bearing veins can be divided into 1) k-feldspar, apatite (I) bearing milky-white quartz veins, 2) white quartz veins contain apatite (II), 3) hematite- white quartz veins and 4) late carbonate veins. Wolframite is the main tungsten ore mineral in the SCP deposit, which occurred in type 1 vein. Wolframite crystals are riched in Fe and have ferberite composition. Scheelite, as next tungsten ore mineral in SCP deposit, formed in 2nd generation and show significant enrichment in As. Scheelite (I) coexist with Wolframite in type 1 veins, and Scheelite (II) replace wolframite in its fractures and rims, also with arsenic-bearing phases occurred in type 2 veins. Gold in SCP deposit occurred as coexist with and/or fine inclusions in Scheelite (II). Other ore minerals that formed in type 2 veins include base metals and Fe sulfides, cobaltite, niccolite, Cu-Ni-Fe sulfides and native bismuth. Type 3 and 4 veins are white quartz-hematite and barren carbonate veins.
δ18 O of ore-forming fluids, which milky-white and white quartz and wolframite formed from them are 7.91-8.61‰, 5.86-6.76‰ and 3.44-6.94‰ respectively. Based on the oxygen isotope studies, progressive mixing of original magmatic fluids with meteoric waters cause precipitation of metals in veins.
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.
M Honarmand; N Rashidnejad Omran; M.H Emami; Gh Nabatian
Abstract
The Marfion Granitoid Complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt. This complex consists of four main intrusives, including the Mozvash micro-dioritic to micro-monzodioritic intrusive, which scattered as separate outcrops ...
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The Marfion Granitoid Complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt. This complex consists of four main intrusives, including the Mozvash micro-dioritic to micro-monzodioritic intrusive, which scattered as separate outcrops through the western part of the area, the Marfioun spherical tonalitic intrusive which is the most widespread pluton throughout the area, the Poudalg N-S elongated tonalitic intrusive, and the Ghalhar quartz-dioritic intrusive. The mafic microgranular enclaves with geochemical properties similar to their host granitoid are abundant in the Marfion and also in some parts of Poudalg and Ghalhar intrusives. According to geochemical data, the Marfion granitoid complex is metalominous, I-type and show the low to medium potassium calc-alkaline affinity. Using U-Pb zircon dating method, the obtained magma crystallization ages are about 50 Ma for the Mozvash intrusive and 18 Ma for the Marfion, Poudalg and Ghalhar intrusives. The geochemical evidences suggest that the Eocene Mozvash microdioritic magma is the result of the lower crust’s partial melting and and its mixture with the mantle’s melts in an active continental margin. The Miocene intrusives were derived from partial melting of a common lower crustal mafic source caused by the mantle melts in a post- collisional setting. The Mozvash micro-diorite intrusive shows less fractionated REE pattern than the Miocene intrusives. The geochemical evidences suggest a same petrogenetic model for tonalite and quartz-diorite magmas. The Marfion, Ghalhar and poudalg intrusives and their enclaves show relatively high Al2O3 and Na2O/K2O ratio and LREEs, which suggest partial melting of metabasaltic rocks. The geochemical investigations indicate that the quartz-diorites and tonalites are derived from the process of amphibole dehydration melting reacted in the lower crust.
H Dadashzadeh Ahari; P Afzal; N Rashidnejad Omran
Abstract
Separation of high grade from low grade veins and veinlets is very important operation in vein type deposits, especially in gold deposits because low value variations are very significant in their mineral exploration. In this paper, Concentration-Volume (C-V) fractal model was utilized for separation ...
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Separation of high grade from low grade veins and veinlets is very important operation in vein type deposits, especially in gold deposits because low value variations are very significant in their mineral exploration. In this paper, Concentration-Volume (C-V) fractal model was utilized for separation and classification of gold veins in the Qolqoleh deposit, which is located in the Kordestan province, NW of the Sanandaj-Sirjan metamorphic structural zone. Based on the obtained results from the model, different populations consisting of wall rocks, low grade, moderately grade, high grade and enriched zones were separated in the deposit. Rock types of the deposit were correlated with resulted mineralized zones by log ratio matrix. The most parts of the deposit have Au values lower than 3.98 ppm including low and moderately grade veins. However, mineralized veins hosted in chlorite-schists and this can be one of the exploration keys for gold prospecting in other parts of the Sanandaj-Sirjan zone.
S Ghaderi; E Rastad; N Rashidnejad-Omran; M Mohajjel
Abstract
Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle ...
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Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle Jurassic volcano-sedimentary sequences, and their distribution is indicated by layering. These deposits are located in a specific stratigraphic position and are concentrated in contact of volcanic units with carbonate rocks. The geodynamic setting of this category probably is intracontinental rifting. The second category contains deposits located in metamorphosed sedimentary rocks of the Shemshak group and Jurassic granitoids. These deposits have vein-veinlet geometry and their formation is controlled by faults, fractures and shear zones. The geodynamic setting of this category probably is active continental margins. The mineral paragenesis of the first group generally contains scheelite and Cu-Fe-Zn sulfides, whereas the paragenesis of the second group is wolframite, scheelite, chalcopyrite, arsenopyrite, with gold and specifically bismuth.
M Boveiri Konari; E Rastad; N Rashidnejad-Omran
Abstract
Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, ...
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Lower Cretaceous volcano-sedimentary sequence in the northwest and southeast of Safashahr (Dehbid) in marginal subzone of southern Sanandaj-Sirjan Zone comprises the Keshtmahaki deposit and few other occurrences of copper (-silver). The oldest rock units in the region are Jurassic shale and sandstone, which are unconformably overlain by the Lower Cretaceous progressive sequence with basal conglomerate, sandstone and silty shale. Copper (-Ag) mineralization occurred in the Lower Cretaceous pyroclastics and volcanic lava. The host rock is a crystal lithic tuff with trachyandesite-andesite affinity in which the stratabound and lenticular ore body is extended discontinuously over 35 km that laterally and vertically changed into orbitolina limestone. Ore minerals include chalcocite, bornite, native copper, digenite, chalcopyrite, pyrite, Ag-bearing clausthalite, covellite, anilite, malachite and azurite. Ore textures and structures are open space filling, vein-veinlet, replacement, disseminated and laminated-like. The lithogeochemical studies in 6 lithostratigraphic profiles from NW to SE of Safashahr indicated Cu (-Ag) mineralization occurrence in a specific stratigraphic unit and a positive relationship with Zn. The lithological, mineralogical, lithogeochemical and microscopic investigations revealed that mineralization initially occurred contemporaneously with volcanism in volcano-sedimentary sequences (absorption of Cu by ferric hydroxide, clay minerals and replacement in feldspar lattice) and then in burial diagenesis during dehydration of pyroclastic and detrital units and alteration resulting from this hydrothermal fluid, Cu released and transported by hydrothermal diagenesis fluids. When this ore-bearing hydrothermal fluid received by the rock unit with high permeability (pyrite-bearing crystal lithic tuff) and reduced conditions resulted from abundance of pyite, replaced them as copper sulphide minerals. S isotopic data of sulphidic minerals indicated that the bacterially sulfate reduction of sea water as an important role provided the nessecary sulfur for sulfide mineralization. Geochemical features of volcanic and pyroclastic units indicated that they formed in an intra-arc rift. On the basis of this study and with respect to some evidences such as tectonic setting, host rock, lenticular shape of the ore body, structure and texture as well as mineral paragenesis we suggest that Keshtmahaki Cu (-Ag) mineralization and surrounding occurrences are Volcanic Red Bed (VRB) type deposit that formed and concentrated contemporaneously with submarine volcanism to deep burial diagenesis processes.
S.T Delavar; I Rasa; M Lotfi; G Borg; N Rashidnejad Omran; P Afzal
Abstract
Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized ...
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Tangedezan Zn-Pb deposit is located in 22 km west of Booeen Miandasht city, in western part of Isfahan province and in Malayer–Isfahan Pb-Zn mineralization belt. This deposit is one of the stratabound deposits in a Jurassic-Cretaceous carbonate sequence. Two main ore body geometries have been recognized in the deposit: 1-layers and lenses, concordant with layering; and 2-discordant secondary forms along the fractures. In Tangedezan deposit two mineralized carbonate facies have been distinguished: 1- dolomitic limestone facies (Microsparite) containing three major mineralization horizons with simple ore mineral paragenesis such as galena, sphalerite and pyrite replacing the host rock and filling the porosities and fractures; and 2- crystallized argillaceous limestone facies with very weak Zn-Pb mineralization in disseminated form. The deposit includes two parts of supergene in surface and sulfides in depth. The simple ore paragenesis comprises of hemimorphite, smithsonite, cerussite, galena, sphalerite and pyrite. Ag and Cd elements have noticeable grade and could be contemplated as by product. All accomplished investigations and evidences such as geological characteristics, mineralized facies, supergene and sulfide development, ore body geometry, ore minerals paragenesis, texture and structures in different scale, existing alterations specially dolomitization and lithogeochemical studies all reveal that Tangedezan deposit is a Zn-Pb Mississippi Valley Type (MVT) deposit.
R Dabiri; M.H Emami; H Mollaei; M Ghaffari; M Vosougi Abedini; N Rashidnejad Omran
Abstract
Quaternary volcanic rocks are widely developed in NW of Ahar, NW Iran. Based on geochemical data, these rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. The major- and trace-element chemistry indicates that the lavas are dominantly alkaline in character. ...
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Quaternary volcanic rocks are widely developed in NW of Ahar, NW Iran. Based on geochemical data, these rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. The major- and trace-element chemistry indicates that the lavas are dominantly alkaline in character. The studied rocks display microlithic porphyritic texture with phenocrysts of olivine, clinopyroxene, and plagioclase ± amphibole ± biotite. Major and trace element abundances vary along continuous trends of increasing SiO2, Al2O3, K2O, Na2O, Ba and Rb decreasing CaO, Fe2O3* and Cr with decreasing MgO.The volcanic rocks in this area are characterized by the LILE and LREE enrichments and negative HFSE anomalies. The Sr and Nd isotopic ratios vary from 0.704463 to 0.704921and from 0.512649 to 0.512774, respectively.CaO/Al2O3 ratios versus MgO, La/Sm ratios versus Rb and Ba and Zr versus Th suggest that that fractional crystallization was a major process during the evolution of magmas. AFC modeling and isotopic data as well as microscopic evidence, clearly indicate that crustal contamination accompanied by the fractional crystallization played an important role in petrogenesis of the trachyandesites. Also, geochemical and isotopic compositions indicate that magma mixing was not essential process in the evolution of Ahar magmas. Alkali basaltswith high 143Nd/144Nd ratio, low 87Sr/86Sr ratio and high MgO, Ni and Cr contents indicate that they crystallized from relatively primitive magmas. REE modelling and Trace element ratios indicate that the alkali baslats were derived by small degrees (~1-3%) of partial melting from the spinel lherzolite.
H Harati; A Khakzad; N Rashidnejad Omran; H Asadi Harouni; S.J Javad Moghaddassi
Abstract
The kahang Copper porphyry deposit on Urumieh-Dokhtar magmatic arc, is located in NE of Esfahan. Around of this deposit, Eocene volcanics and pyroclastic rocks ranging in composition from basaltic trachy-andesitic to dacitic are exposed. Granitoids subvolcanic and volcanoplutonic, the causes of alteration ...
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The kahang Copper porphyry deposit on Urumieh-Dokhtar magmatic arc, is located in NE of Esfahan. Around of this deposit, Eocene volcanics and pyroclastic rocks ranging in composition from basaltic trachy-andesitic to dacitic are exposed. Granitoids subvolcanic and volcanoplutonic, the causes of alteration and mineralizaton, replacement in Eocene rocks assemblage in afew puls from Oligocene to Miocene. This plutons ranging in composition from monzodiorite quartzdiorite granodiorite to granite with porphyroeidal texture. Alteration and mineralization is classically developed in this deposit. Samples from surface soil were collected in 50m profiles gridding which the distance samplings in along the profile are 25m. The total numbers of samples are 2564 which are analyzed by ICP-OES method for 43 elements. In geochemical anomaly maps, activating of faults with another tectonic factors, environmental conditions alteration and erosion in moving and concentration this anomaly are illustrated. Same as the litho geochemical anomalies the most amount distribution of Cu in the eastern and center of the region, Au in the west and center and Mo in all three region are depicted. In elemental correlation graphs suitable correlation is for Copper and Gold.
M. H. Emami; R. Monsef; N. Rashid Nejad Omran
Abstract
Miocene to Pliocene volcanic rocks in the Raveh region have exposed northern part of the Urumieh - Dokhtar Magmatic Belt. Neogene volcanic rocks are situated on Upper Red Formation. Magmatic activity separated in two phase. The first phase is composed of basic to intermediate volcanic rocks such as basaltic-andesite ...
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Miocene to Pliocene volcanic rocks in the Raveh region have exposed northern part of the Urumieh - Dokhtar Magmatic Belt. Neogene volcanic rocks are situated on Upper Red Formation. Magmatic activity separated in two phase. The first phase is composed of basic to intermediate volcanic rocks such as basaltic-andesite to andesitic lavas and pyroclastics (Ngv1).The second phase has intermediate to acidic rocks as well as andesite, quartz andesite and dacite (Ngv2).According to geochemical data, these samples show magmatic affinities to the calc-alkaline series. REE and trace element patterns show LREE enrichment relative to HREE, depletion in Nb, Ta and Ti, and also high Th/Yb and Th/Nb ratios relative to MORB and OIB. The parent magma of the Raveh volcanic rocks, with calc-alkaline compositions, has been originated probably from the metasomatized mantle with effective of fluids and sediment resulted from the Neothytian subducting slab. After collision between Arabian plate and Central Iran Block in Early Cenozoic, region experienced of crustal thickening and volcanism activity formed in relation to localized extensional basin in Early Miocene to Early Pliocene. The volcanism postdates continental collision, occurring in transtentional tectonic setting.
Gh. Tajbakhsh; M. H. Emami; H. Moine Vaziri; N. Rashidnejad Omran
Abstract
Nepheline syenite intrusive of Kaleybar is located in South and West of the Kaleybar city in eastern Azarbayjan province. This zoned intrusive complex is formed by penetration of two separated silica undersaturated and saturatated magmatic phases with Oligocene-Miocene ages. Undersaturated rocks are ...
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Nepheline syenite intrusive of Kaleybar is located in South and West of the Kaleybar city in eastern Azarbayjan province. This zoned intrusive complex is formed by penetration of two separated silica undersaturated and saturatated magmatic phases with Oligocene-Miocene ages. Undersaturated rocks are composed of alkali pyroxenite, mela alkali-gabbro to nepheline gabbro-diorte, nepheline syenite and nepheline sodalite syenite dikes. Silica saturated rocks is consist of a quartz monzonitic stock, which has penetrated in the center of nepheline syenite intrusive and related quartz syenite - micro syenite dikes. Undersaturated phase has potassic alkaline affinity and nepheline syenites are miaskitic Malignite. In contrast, silica saturated rocks belong to high-K calc-alkaline to shoshonitic magma. Field observation, petrographical and geochemical studies, indicates that undersaturated rocks are comagmatic and crystal fractionation, accumulation and low density minerals floatation processes play significant role in their magmatic evolution. High enrichment of rare elements especially LREE and LILE compare to variable depletion of HREE and HFSE are infer a basanitic parental magma generated from a previously subduction-metasomatised lithospheric mantle source. Silica saturated magma of Kaleybar was probably resulted form the lower crust Partial melting and geochemical similarities resulted from partial melting of lower crust and its geochemical similarities with undersaturated parts is due to magma mixing and contamination. Repeatedly injection of alkaline and calc-alkaline magmas could be occurred in a post collision setting after Eocene in Azerbaijan region.
N. A. Rashidnejad Omran; A. A. Fattahi; F. Masoudi
Abstract
The late Eocene post-collisional Khoshoumi- Dar-Anjir intrusive complex consist of two adjacent Khoshoumi granite and Dar Anjir diorite plutons in Saghand area, located in 120 km northeast of Yazd in Central Iran structural zone. This complex intruded within high-grade metamorphic rocks of Chapedony ...
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The late Eocene post-collisional Khoshoumi- Dar-Anjir intrusive complex consist of two adjacent Khoshoumi granite and Dar Anjir diorite plutons in Saghand area, located in 120 km northeast of Yazd in Central Iran structural zone. This complex intruded within high-grade metamorphic rocks of Chapedony Complex. Syenogranite, monzogranite, granodiorite, tonalite and quartzdiorite constitiue its lithologies. Aplitic and micromonzonitic to microdioritic dikes crosscutting the entire body. Hybrid rocks and mafic microgranular enclaves with various shapes and sizes are widely seen in this complex. Geochemical investigations show that these rocks are metaluminous to moderately peraluminous, magnesian and high- K calc- alkaline I- and A-type granitoids. Chonderite- normalized REE patterns of both plutons and related dikes display intra-elemental fractionation (2.72 >(La/Yb)N >41.64) and concentration of LREE and Eu negative anomalies (ave Eu/Eu*= 0.63). Trace elements behavior represent depletion in Nb, Ti, P and enrichment in K, Rb, Ba and Th that could be assigned to mafic magma contamination by crustal materials. Their tectonic setting match with Volcanic Arc Granites (VAG) and Within Plate Granites (WPG). Petrographical, geological and tectonomagmatic characteristics of this intrusive complex are very similar to high- K calc- alkaline granites (KGC) and like most of them, fractional crystallization and mafic – felsic magma mixing play significant role in its evolution and petrogenesis.
P. Afzal; A. Khakzad; P. Moarefvand; N. Rashid Nezhad Omran; Y. Fadakar Alghalandis
Abstract
Determination of different zones in porphyry deposits is on of important goals in their exploration because this operation especially determination supergene zone is important for economical study in these deposits. Traditional methods based on alterations and mineralogical studies are not proper in ...
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Determination of different zones in porphyry deposits is on of important goals in their exploration because this operation especially determination supergene zone is important for economical study in these deposits. Traditional methods based on alterations and mineralogical studies are not proper in many cases because these methods are based on petrogaraphical and mineralographical studies, only. Later methods were introduced basis fluid inclusions and isotopes are indirect methods and applied for alterations separation. Fractal methods are applicable in surface geological and geochemical studies for many reasons such as using all data, according to spatial distribution and anomalies geometrical shapes. In this research, concentration-volume method entitled new fractal method is introduced for separation of supergene, hypogene, oxidant and host rock based on major element grade in porphyry deposits. Mathematical base of this method by using of power-law function and partition function for fractal and multifractal modeling, concentration-volume is used for zones separation in Chah-Firuzeh Cu porphyry deposit in Shahrbabak in Kerman province. First, Cu distribution in this deposit was evaluated by geostatistical methods and concentration-volume logarithmic diagram that break points show grade boundaries of different zones and boundary between mineralization and host rock. Also, alteration, mineralogical and zonation models were constructed based on geological observation and compared by results from concentration-volume fractal method. Separated zones by this fractal method are smaller and near to fact and correlated by geological models. Usage of grade parameter that is most important direct and quality parameter constructed reality results.
M. Aghazadeh; M. H. Emami; H. Moin Vaziri; N. Rashidnezhad Omran; A. Castro
Abstract
Khankandi pluton is located in northwestren part of Iran, within Garadagh (Arasbaran) - south Armenia block. Main units of the pluton are monzonite and granodiorite associated with minor gabbro and lamprophyric and dacitic dykes. Granodioritic plutonism is followed by gabbro and monzonite. Lamprophyric ...
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Khankandi pluton is located in northwestren part of Iran, within Garadagh (Arasbaran) - south Armenia block. Main units of the pluton are monzonite and granodiorite associated with minor gabbro and lamprophyric and dacitic dykes. Granodioritic plutonism is followed by gabbro and monzonite. Lamprophyric and dacitic dykes are emplaced at the end of the granodioritic plutonism. Gabbro and monzonites are shoshonitic, and granodiorites and dacites have high K-calc alkaline nature and charactistics of C-type (potassic or continental) adakites and high Ba-Sr granitoides. Lamprophyres are alkaline and have camptonitic composition. The monzonites follow fractionation trend of gabbro with minor crustal assimilation and contamination. Melting of garnet bearing mafic lower crust, metasomatised lithospheric mantle and upwelling asthenosphere produced granodioritic and dacitic, shoshonitic gabbro and lamprophyric magma respectively. The production of various magma types in the Oligocene of the Arasbaran occurred in response to slab break off and/or delamination of lithospheric mantle and upwelling of asthenosphere. Plutonism occurred after collision between Iranian and Arabian plates and crustal thickening in the extensional post collisional tectonic setting.