M Abdi; M.H Karimpour; M.H Zarinkoob
Abstract
The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by ...
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The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by gold, high primary sulfide bearing area, secondary iron oxide and sericitic and silicic alterationrevealed that the third factor of factor analysis is the agent of mineralization in the study area. The suitable tectonic setting, shallow depth intrusiveswithintermediate composition, calc-alkalineand oxidant magmatism, anomaly of gold and disseminated mineralization in thehost rock and sulfide veinlet accompanied byabundant secondary iron oxide providedproperconditions for porphyry and epithermal type gold mineralization in the study area.
F Kangarani Farahani; A.A Calagari; A Abedini
Abstract
The Shahbolaghi laterite deposit is located in ~40 km southeast of Damavand, Tehran province. This deposit was developed as stratiform horizons within the shales and sandstones of Shemshak formation (Jurassic). Mineralogical investigations show that the major minerals in this deposit include hematite, ...
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The Shahbolaghi laterite deposit is located in ~40 km southeast of Damavand, Tehran province. This deposit was developed as stratiform horizons within the shales and sandstones of Shemshak formation (Jurassic). Mineralogical investigations show that the major minerals in this deposit include hematite, boehmite, and anatase accompanied by lesser amounts of goethite, magnetite, chamosite, kaolinite, quartz, calcite, diaspore, zircon, pyrite, and rutile. The microscopic evidences such as development of spastoidic textures within the ores suggest a high energy water-saturated sedimentary environment during the lateritization processes. By considering the mineral assemblage and textural characteristics, deposition and diagenesis of this horizon occurred in an oxidizing and almost near surface environment. Based on the obtained data from the field observations, geochemistry of major, trace, and rare earth elements the lateritic horizon at Shahbolaghiwas developed probably byalteration of parent rocks with basaltic composition. The bauxitization process was occurredintrends of kaolinization, destruction of kaolinite, and deferrugenization. The geochemical investigations indicated that the distribution of trace elements in this horizon was controlled by clays and minor mineral phases.
S Soltaninejad; B Shafiei
Abstract
The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, ...
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The Now-Chun deposit, in the Kerman porphyry copper belt, with proved reserve of 268 Mt ore grading 0.034% Mo (100 ppm cut off) and 62 Mt ore grading 0.43% Cu (0.25 cut off), is the first known occurrence of Mo-rich,relatively Cu-poor porphyry mineralization in Iran which is studied from the mineralogical, l, and genetic point of view. The alteration and mineralization of the Now-Chun deposit is related to the highly differentiated porphyritic stock (rhyodacite) belonging to the Oligo-Miocene Mamzar batholith. Based on the present study, the main part of Mo and Cu mineralization in the Now-Chun deposit occurred more in the form of cross-cutting veinlets (stockwork) and less as dissemination type. The presence of molybdenite with/without chalcopyrite association in quartz-anhydrite-orthoclase-biotite potassic veinlets and chalcopyrite occurrence in primary quartz-magnetite veinlets is indicative of the priority of part of the Cu mineralization respect to the Mo during the primary stage of mineralization. The initial mineralization of Mo in the form of molybdenite occurred in quartz-anhydrite-orthoclase-biotite-pyrite-chalcopyrite. The weak correlation between Mo and Cu in the potassic alteration zone (r= -0.2) especially in the high grade ores indicates the difference between the enrichment conditions of both elements in responsible hydrothermal fluids for this alteration and mineralization zone. The presence of thick quartz-pyrite-chalcopyrite veinlets with sericitic halo and quartz-molybdenite without alteration halo either as independent or as intruded within early veinlets (quartz-molybdenite-anhydrite-orthoclase-biotite) have been associated with increasing of Mo and Cu grades in moderately phyllic alteration zone (sericitic and silicified rocks). The positive correlation between Mo and Cu in moderate phyllic zone (r≥ 0.0 to +0.5) which affected potassic ores indicates the similar behavior of both Mo and Cu during formation and evolution of the hydrothermal solution, which is responsible for the alteration and mineralization in the phyllic zone. This study revealed that the main concentration of Mo occurred in deep parts (potassic zone) of the deposit; whereas, Cu is associated with the shallow parts, especially with moderate phyllic zone which affected the potassic zone. As a result, the high grade Mo ores are not Cu-rich and vice versa. The present study indicated that the Now-Chun deposit in comparison with the Sar Cheshmeh deposit (Cu-Mo porphyry) is categorized within the Mo-Cu porphyry deposits. This sub-group of porphyry Cu and Mo deposit is attributed to the function of the Mo-rich and relatively Cu-poor hydrothermal fluids. The more differentiated composition of the ore-hosting porphyry in the Now-Chun deposit (rhyodacite) in comparison with the Sar Cheshmeh porphyry stock (granodiorite-quartzmonzonite), which indicates the late water saturation in its parent magma, was probably the factor of generating such fluids that could segregate the significant proportion of Mo in respect to Cu from the residual melts into H2O, alkalies and silica-enriched fluid phase which ultimately resulted in forming the Mo-Cu porphyry deposit.
M Roohafza; S Alipour; A Abedini
Abstract
Ghareh-bolagh area is located in 20 Km of east of Mahabad, south of West-Azarbaidjan province. Carbonate rocks of Bayandour formation and dolomites of Soltanieh formation in this area are the host of mineralizations from Barium, iron and manganese. Based upon mineralogical investigations, barite, magnetite, ...
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Ghareh-bolagh area is located in 20 Km of east of Mahabad, south of West-Azarbaidjan province. Carbonate rocks of Bayandour formation and dolomites of Soltanieh formation in this area are the host of mineralizations from Barium, iron and manganese. Based upon mineralogical investigations, barite, magnetite, hematite, goethite, limonite, pyrolusite were major mineral assemblages of these mineralizations which that is accompanied by chalcopyrite, malachite, azurite, and calcite in low amounts. The most important geochemical characteristic these mineralizations are relative weak differentiation of LREE from HREE in barite and iron-manganese ores, Eu negative anomalies in iron-manganese ores (0.26-0.76) and Eu positive anomalies in barite (7.7-10.51). Incorporation of the obtained results from investigations of field, petrographic and geochemical (analytic data and correlation coefficients between elements) indicate that factors such as changes in physicochemical conditions of environment (pH, Eh, temperature), activity of complexing ligands, and presence of minor mineral phases (clay minerals, zircon, zenotime, and monazite) played important role in distribution of rare earth elements during mineralization and development of these ores.
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 Kouhestani; M.H Ghaderi; M.H Emami; S Meffre; V Kamenetsky; J McPhie; Kh Zaw
Abstract
The Chah Zard Ag-Au deposit, a typical breccia-hosted low- to intermediate-sulfidation epithermal system, is located within late Miocene andesitic to rhyolitic volcanic complex in the central part of the Urumieh-Dokhtar magmatic belt. The orebodies are emplaced in breccia bodies dominantly hosted by ...
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The Chah Zard Ag-Au deposit, a typical breccia-hosted low- to intermediate-sulfidation epithermal system, is located within late Miocene andesitic to rhyolitic volcanic complex in the central part of the Urumieh-Dokhtar magmatic belt. The orebodies are emplaced in breccia bodies dominantly hosted by rhyolite porphyries. Systematic whole-rock geochemical investigations on the volcanic rocks show that both intermediate and felsic rocks are characterized by significant Large Ion Lithophile Elements (LILE) and Light Rare Earth Elements (LREE) enrichment coupled with High Field Strength Elements (HFSE) depletion. These geochemical data indicate subduction-related magmatic arc affinity for the volcanic rocks, and suggest that hornblende fractionation appears to be an important controlling factor on the evolution of mineralized subvolcanic rocks. Although the rhyolite porphyry has relatively high 87Sr/86Sr ratios, the volcanic rocks have similar Sr and Nd isotopic compositions, displaying 87Sr/86Sr range of 0.704910-0.705967 and εNd(i) values of +2.33 to +2.70. These data suggest that the rhyolitic magmas probably represent the final diffetentiates of parental andesitic magmas with minor crustal contamination. The andesitic magmas generated from partial melting of a mixture of an incompatible element depleted anhydrous asthenospheric mantle source and a hydrous LILE and LREE enriched lithospheric mantle source in response to slab-break-off and upwelling of asthenospheric mantle. The rhyolite porphyry is inferred to have supplied heat that drove the convective hydrothermal system at Chah Zard deposit, but also provided some of the fluid sources responsible for the development of the Chah Zard epithermal system.
Habib Alimohammadian; F Mahdipour Haskouei; J Sabouri
Abstract
The study area is situated at about 8 km away of Neka city, on the main road of Sari-Behshahr, in MazandaranProvince, north of Iran. It is bounded by Alborz fault in the south and Caspian Sea coast line in the north. We applied new environmental magnetism technique and methods including magnetic susceptibility, ...
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The study area is situated at about 8 km away of Neka city, on the main road of Sari-Behshahr, in MazandaranProvince, north of Iran. It is bounded by Alborz fault in the south and Caspian Sea coast line in the north. We applied new environmental magnetism technique and methods including magnetic susceptibility, magnetic mineralogy, IRM and S-IRM to reconstruct the past 50 ka climate conditions and also investigate relationship between climate change and magnetic variations. We also compared the geochemistry and magnetic analysis of the loess/palaeosol deposits and the results were used to correlate these variations with climate change in the study area. The pattern of variation of geochemical data shows similarity with those of magnetic one. The increase/decrease in magnetic susceptibility is coinciding with palaeosol/loess sequences. Plotting magnetic susceptibility variation versus lithological column of Kolet section enabled us to recognize short period of climatically cycles known as stadials/interstadials in loess/palaeosol sequences. We recognized 4 stadials for upper palaeosol, single stadial for lower palaeosol, 6 interstadials for upper loess and one interstadial for lower loess deposites.
F. Khaleghi; Gh. Hosseinzadeh; I. Rasa; M. Moayyed
Abstract
The Syah kamar molybdenum deposit is a porphyry molybdenum system which has been explored during the recent research of author in the northwest of Iran and is being reported for the first time and its ore mineralization is explained and discussed in this paper on the basis of geological data, mineralization ...
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The Syah kamar molybdenum deposit is a porphyry molybdenum system which has been explored during the recent research of author in the northwest of Iran and is being reported for the first time and its ore mineralization is explained and discussed in this paper on the basis of geological data, mineralization evidences, geochemistry and fluid inclusions thermometry data. A porphyry quartz-monzonitic stock, which belongs to the K-rich (alkali-rich) calc-alkaline rock series and on the basis of geochemical data and tectonic setting viewpoint, formed as the post-collision granites is considered as the mineralization parent rock of this system. According to the emplacement pattern of productive intrusive bodies of the region, the mineralization of molybdenum have occurred after Eocene time, about the Oligocene time, and the mineralization process has taken place most probably at the last stage of magma emplacement, and on the basis of microthermometery and salinity data, its metaliferous hydrothermal solution have had low salinity and medium homogenization temperature. In addition, according to the host rock type, accompanying alterations and some other evidences, the mineralization characteristics of Syah kamar molybdenum prospect are comparable with the molybdenum deposits of the quartz-monzonitic type. During the tectonic processes, the ore-bearing hydrothermal solution ascended along weak zones and suitable fault structures, and intruded into the joints and fissures of surrounding rocks, and as a result of physiochemical changes of environment and some other effects, finally the Syah kamar molybdenum deposit has been formed.
Seyed Javad Moghaddasi; Y. Negahban
Abstract
Robat Karim manganese deposit is located in 7 km northwest of Robat Karim (southwest of Teharan), within northeastern margin of Orumiyeh-dokhtar volcanic belt. Based on regional geology, the studied area is situated in the northern Saveh Eocene volcanic assemblage, composed of rhyolite, trachyte, andesite ...
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Robat Karim manganese deposit is located in 7 km northwest of Robat Karim (southwest of Teharan), within northeastern margin of Orumiyeh-dokhtar volcanic belt. Based on regional geology, the studied area is situated in the northern Saveh Eocene volcanic assemblage, composed of rhyolite, trachyte, andesite and basalt. Manganese mineralization is occurred as veins, in faults, joints and fractures that crosscut the volcanic rocks. According to mineralogical studies, the manganese ore of the studied area is composed of pyrolusite, psilomelane, ramsdelite and hollandite, as well as calcite and quartz. Intergrowths of manganese oxides and quartz (or calcite) associated with various open space filling textures support the epithermal origin of the ore forming fluids in this area. Geochemistry of major and trace elements in Robat Karim manganese ores, similarity of their chondrite normalized REE pattern with volcanic host rocks and other hydrothermal manganese deposits of the world, as well as negative Ce anomaly indicate a probable epithermal origin of the deposit. Ore forming fluids could be originated from meteoric and/or magmatic waters circulating through Eocene volcanic rocks, dissolve manganese and other metals and deposit them in fault planes and major fractures. High pressure of the ore forming fluid has caused the formation of brecciated trachyte.
R. Deevsalar; M. V. Valizadeh; V. Ahadnejad
Abstract
Granitic rocks of Malayer plutonic complex contain varieties of enclaves with different shapes, sizes, mineralogy andchemical composition. The interpretation of bivariant geochemical diagrams of major oxides and trace elements with respect to higher values of some of oxides such as MnO, TiO2, MgO, ...
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Granitic rocks of Malayer plutonic complex contain varieties of enclaves with different shapes, sizes, mineralogy andchemical composition. The interpretation of bivariant geochemical diagrams of major oxides and trace elements with respect to higher values of some of oxides such as MnO, TiO2, MgO, CaO& FeOt than host rocks in one groups of enclaves and moreover linear trend of these oxides and some of trace elements such as Ni, Cr, V indicate to different nature and mafic source of these enclaves (Mafic type) than host rocks and other enclaves (Felsic type).The study of chemical composition of this enclaves by using of univariant and bivariant statistical methods (bivariant regression analysis, correlation coefficients, cluster analysis and principle component analysis) indicate clear chemical contrast between mafic enclaves with felsic enclaves and granitic host rocks and in other side chemical affinity of felsic enclaves and their host rocks. Distinctive distribution of the majority of oxides and trace elements of mafic enclaves and host rocks and low values for R2 in regression analysis, low value of correlation coefficient of major element oxides and trace elements between enclaves and their host rocks, separate position of samples in cluster pattern and special direction of variants and samples of vectors in bivariant diagram of principle component analysis (PCA) are outputs of different geochemical characteristics of enclaves and host rocks. Moreover this correlates with different trends of each major oxides and trace elements in bivariant geochemical diagram (Harker diagram).
H. A. Tajeddin; E. Rastad; A. Yagoubpour; M. Mohajjel
Abstract
Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green ...
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Barika deposit is the first and only recognized gold (and silver) rich – massive sulfide deposit in Iran which is located at 18 km east of Sardasht city, north western part of Sanandaj-Sirjan metamorphic zone. Rock units outcropped in this area are volcano sedimentary metamorphosed rocks in green schist facies, and include association of metaandesite, metatuffite, phyllite and slate rocks, among which the metaandesitic unit (KMv1) is host rock of the deposit. Ore mineral assemblages in stratiform part of the deposit, which contain massive and banded pyrite and barite associated with subordinary silica bands, are very variable in composition and consist of pyrite, sphalerite, galena, stibnite and a variety of sulfosalt minerals and electrum. Ore mineral assemblage in silicic veins in stringer zone, are simpler and consist of pyrite, galena, sphalerite, tetrahedrite and rare chalcopyrite. Average gold and silver grades in stratiform ore are 4.2 and 260 g/t respectively and in silica stringer veins are 0.7 and 30 g/t. Base metal content in both part of the deposit is less than 1%. Lithotectonic study and trace and rare earth elements diagrams associated with Ce/Pb and Nb/U ratios of the metavolcanic rocks in the deposit area indicate that the rocks were generated from a lithospheric mantle source in the active continental margin of the SSZ. A geochemical study of Barika deposit reveals that distribution patterns and correlation coefficient of ore elements in parts of the Barika stratiform ore and stringer zone are completely in correlation with an undeformed massive sulfide deposit. The geochemical documents indicate that despite the metamorphism and highly deformation on the deposit, the primary distribution patterns and proportion of the ore elements are well conserved, as geochemical characteristics of the Barika deformed deposit is as well as correlated with an undeformed gold- rich volcanogenic massive sulfide deposit. However there is clear textural evidence for remobilization of As, Sb, Ag and Pb minerals together with Au in Barika deposit, but, remobilized constituents of the ores do not appear to have moved beyond the margins of the ore bodies and primary metal zonation.
A. M. Ali Khasi; M. Hosseini Barzi; M. Shadan
Abstract
Determination of sedimentary environment, provenance and tectonic setting of Ab-Haji Formation sandstones (Lower Jurassic) have been carried out in Cheshmeh Bakhshi and Sartakht-e-Shotoran sections which are located in Kalmard Block. Facies analysis of sedimentary facies in mentioned sections implies ...
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Determination of sedimentary environment, provenance and tectonic setting of Ab-Haji Formation sandstones (Lower Jurassic) have been carried out in Cheshmeh Bakhshi and Sartakht-e-Shotoran sections which are located in Kalmard Block. Facies analysis of sedimentary facies in mentioned sections implies three clastic faceis associations including delta plain, delta front and prodelta and two carbonate facies, relevant to bar. The obtained results from modal analysis and geochemical data point to cratonic tectonic setting and presence of qurtzose rocks in the source area in the course of recycling processes. Moereover, using the tectonic discrimination diagrams suggest that Ab-Haji sandstones have been deposited in a passive continental margin. The calculated chemical index of alteration (CIA) and the plagioclase index of alteration (PIA), based on major element oxides, denote moderate to intense weathering in the hinterland. This consequence is conformed with the modal analysis and petrographic evidence referring to humid and semi-humid climate.
A. Imamalipour
Abstract
The Khoy ophiolite complex in northwest Iran hosts several podiform chromitite bodies. The chromitite deposits of Aland area in this ophiolite have lenticular, tabular and irregular vein shapes and emplaced in depleted mantle hurzburgite. Chromitites have different textures including disseminated, massive, ...
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The Khoy ophiolite complex in northwest Iran hosts several podiform chromitite bodies. The chromitite deposits of Aland area in this ophiolite have lenticular, tabular and irregular vein shapes and emplaced in depleted mantle hurzburgite. Chromitites have different textures including disseminated, massive, nodular, banded and cataclastic textures. The ore bodies are surrounded by dunitic envelopes of variable thickness. Mineral chemistry of chromite grains indicate that they are recognized by #Cr [Cr/(Cr+Al)] values range between 0.66 and 0.88, #Mg [Mg/( Mg +Fe+2)] values range between 0.42 and 0.66. Cr2O3, Al2O3 and MgO values range between 45.89 and 54.95 %, 8.53-17.18 % and 8.38-14.29% respectively. There is a negative correlation among #Cr and #Mg of chromites, typical of podiform chromitites. The composition of chromites including #Cr, #Mg, their contents of Cr2O3, Al2O3, Fe2O3, MgO and TiO2 and also correlation coefficients between different components of them have conformity with total composition of podiform chromitites. Compositions of chromites in Aland area correspond to Cr-rich chromites with #Cr>0.6 and Al2O3<25%. Their lower content of TiO2 accompanied with their compositional location in TiO2 vs. Cr/(Cr+Al) and TiO2 vs. Al2O3 diagrams may reflect the crystallization of chromites from boninitic magmas in supra-subduction geotectonic setting. The bulk rock analyses of chromitites indicate that their Cr2O3 values have widespread range, 19-51.6 wt %. Compositional variations in their Cr2O3, Al2O3, Fe2O3, SiO2 and MgO components are reflections of their textural characteristics.
A. Bayet goll; M. Hosseini-Barzi
Abstract
Geochemical analysis of major elements from 12 sampels from Shirgesht Formation sandstones and shales with Ordovicien age in sections of kuh-Asheghan and Kuh-Rahdar at Kalmard block in Central Iran zone, and plotting these data on silisiclastic rocks classification diagrams, show that they are quartzarenite ...
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Geochemical analysis of major elements from 12 sampels from Shirgesht Formation sandstones and shales with Ordovicien age in sections of kuh-Asheghan and Kuh-Rahdar at Kalmard block in Central Iran zone, and plotting these data on silisiclastic rocks classification diagrams, show that they are quartzarenite and shale. Moreover, the use of discrimination, biplot triangular diagrams determined the quartzose recycled provenance (craton and recycled orogen) and passive margin tectonic setting for these deposites. These data suggest the quartzose sedimentary provenace for sandstones and intermediate to felsic ignious provenance for shale. Furthermore, determination of weathering influence in source area, by using CIA index, indicated that the source area of these deposites has been exposed to intense weathering. This can be explained by humid weather in source area of passive continental margin.
F. Ehya; M. Lotfi
Abstract
The Sarfaryab bauxite deposits occur in karstic depressions at the top of the limestones of the Cenomanian to Lower Turonian Sarvak Formation, which are overlain by the limestones of the Santonian Ilam Formation. In order to determine the possible source rocks of the Sarfaryab bauxite deposits, a few ...
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The Sarfaryab bauxite deposits occur in karstic depressions at the top of the limestones of the Cenomanian to Lower Turonian Sarvak Formation, which are overlain by the limestones of the Santonian Ilam Formation. In order to determine the possible source rocks of the Sarfaryab bauxite deposits, a few samples were collected from Sarvak Formation, terra rossa and bauxite ore and geochemically and geostatistically analyzed. Plots of chemical data and correlation coefficients show that Al, Ti, Zr, Nb, Cr and V were immobile during the bauxitization process. In the scatter diagrams of Zr and TiO2 versus Al2O3, regression lines pass through the origin and terra rossa falls between the Sarvak Formation and bauxite. Based on this research, it can be stated that the source rock of the Sarfaryab bauxite deposits is the Sarvak Formation and terra rossa is an intermediate product during limestone-bauxite transformation. Post-Turonian uplift had exposed recently deposited limestones of the Sarvak Formation to karst weathering, and a layer of argillaceous debris accumulated on its surface and was partly converted to bauxite. Subsidence followed, and the bauxite was preserved by the deposition of limestones of the Ilam Formation. Uplift in Pliocene time, with ensuing erosion, exposed the bauxite deposits to their present situation.
Z.K. Mossadegh; M.H. Adabi; A. Sadeghi
Abstract
We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the ...
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We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the Pabdeh Formation. The Late Oligocene to Early Miocene Asmari Formation lies above the Pabdeh Formation and is overlain by the Gachsaran Formation. Elemental geochemistry (Fe, Mg, Na, Sr, Mn, Ca), and Oxygen and Carbon isotope analyses indicate that meteoric diagenesis affected carbonates of the Asmari Formation. The δ18O/δ13C data plots in an inverted J-trend suggesting that meteoric diagensis occurred in a closed to semi-closed system. The geochemistry also suggests that the original mineralogy was Aragonite. The boundary between the Pabdeh and Asmari Formations can be recognized by changes in the δ 18O and δ 13C. In the Pabdeh Formation the δ 18O and δ 13C values are mostly negative, but in the Asmari Formation values range from positive to negative. Strontium is much higher in the Pabdeh Formation than in the Asmari Formation. Changes in isotope and elemental geochemistry clearly show the Chattian-Aquitanian and Aquitanian-Burgidalian boundaries.
M. A. Salehi; M. H. Adabi; H. Ghalavand; M. Khatibi-Mehr
Abstract
The Fahliyan Formation with the age of Lower Cretaceous (Berriasian-Hauterivian) were studied for microfacies analysis, diagenesis and original carbonate mineralogy in the type section at Fahliyan Anticline and subsurface section in well number 55 of Gachsaran Oil Field. Petrographic studies led to the ...
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The Fahliyan Formation with the age of Lower Cretaceous (Berriasian-Hauterivian) were studied for microfacies analysis, diagenesis and original carbonate mineralogy in the type section at Fahliyan Anticline and subsurface section in well number 55 of Gachsaran Oil Field. Petrographic studies led to the recognition of 10 microfacies that were deposited in four facies belts: tidal flat, lagoon, shoal and open marine. The observed facies patterns indicated a carbonate rimmed-shelf depositional environment. Recognition of different type of cements shows that the Fahliyan Formation has mostly undergone meteroric diagenesis. Major and minor elements and carbon and oxygen isotope values indicate that aragonite was the original carbonate mineralogy in the Fahliyan Formation, and suggests that alteration occurred in a closed diagenetic system, with low water/rock interaction.
M. Advay; A. Jahangiri; M. Mojtahedi; J. Ghalamghash
Abstract
The study area as a part of Maku-Tabriz zone is located in about 20 km NE of Khoy, NW Iran. Shah Ashan Dagh granite covers about 60 km2 of the area and emplaced into Permian host rocks and covered by Oligo-Miocene sedimentary rocks (Qom Formation). The Shah Ashan Dagh intrusive rocks composed of gabbro ...
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The study area as a part of Maku-Tabriz zone is located in about 20 km NE of Khoy, NW Iran. Shah Ashan Dagh granite covers about 60 km2 of the area and emplaced into Permian host rocks and covered by Oligo-Miocene sedimentary rocks (Qom Formation). The Shah Ashan Dagh intrusive rocks composed of gabbro and alkali-feldspar granite. Porphyric and granophyric textures indicate shallow depth emplacement and perthitic texture shows hypersolvous nature of this body. The studied mafic rocks have high LREEs relative to HREEs and they indicate relatively enrichment of LILEs and depletion in HFSEs (exception Hf, Ta, Nb). The studied mafic rocks based on positive Nb and Ta anomalies show similarity to plum type MORB. These rocks are tholeiitic and they have mantle plum enriched source. Shah Ashan Dagh granite characterized with high-K, sub-alkaline, metaluminous to peraluminous and weakly peralkaline nature. They have high content of LILEs, especially Th and Rb, and low content of Eu, Sr, Ta, Nb, Ba, and Ti, implying the granites may have been derived from crustal melts.
N. Khodaei; M. H. Adabi; S. A. Moallemi; M. Moradpour
Abstract
The Kangan Formation is a carbonate-evaporate sequence that is considered as a part of the largest carbonate reservoir in the South Pars Field at Persian Gulf. Petrography analysis led to the recognition of 5 different dolomite types: such as dolomicrite, dolomicrospar, dolospar, dolomite cement and ...
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The Kangan Formation is a carbonate-evaporate sequence that is considered as a part of the largest carbonate reservoir in the South Pars Field at Persian Gulf. Petrography analysis led to the recognition of 5 different dolomite types: such as dolomicrite, dolomicrospar, dolospar, dolomite cement and saddle dolomite. Elemental studies on dolomicrite and dolomicrospar samples show a relative increase of Sr and Na and relative decrease of Fe and Mn in comparison with the dolomicrosparite samples. It is notable that the oxygen-carbon isotope trend in dolomite samples are due to slight influence of meteoric diagenesis (about dolomites type I, II and III) and burial diagenesis (about dolomites type IV and V). The dolomicrites have been undergone slight meteoric diagenesis, although they have formed in sabkha environment. The source of Mg for dolomicrites is the magnesium of seawater and interstitial waters equilibrium with seawater and on the other hand probably for the coarser grain dolomites in the Kangan Formation is connate waters and basinal brines. Based on the heaviest oxygen isotope in dolomicrite samples, paleotemperature of depositional environment of the Kangan Formation was around 44.5°C.
A. R. Ghiasvand; M. Ghaderi; N. Rashidnejad-Omran
Abstract
The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of ...
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The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of calc-alkaline and metaluminous composition, representing I-type granite characteristics, has intruded the Eocene volcanopyroclastic rocks in the north of Semnan. Skarn development and iron mineralization have occurred at the contact of the intrusive body and the volcanopyroclastic rocks. Mineral Paragenesis consists of magnetite accompanied by hematite, oligist, pyrite, chalcopyrite, garnet, pyroxene and epidote. Geometry of the ore bodies is massive, lenticular and vein type and their texture is disseminated, brecciated, vein-veinlet and massive. Dominant alterations in the area are propylitic, argillic, silicic, sericitic, chloritic and pyritic, respectively. The intrusive body has many similarities with intrusive bodies which form Fe-skarn deposits. Variations in the calculated parameters for REE indicate contribution of magmatic origin hydrothermal fluids to mineralization and that the intrusive body has had the dominant role as source of the skarn ore materials. Along with the intrusion, emplacement and crystallization of intrusive body, Fe-bearing fluids have intruded the volcanopyroclastic rocks, forming sodic metasomatism and deposited iron ores in the north of Semnan which have many similarities with calcic Fe-skarn deposits.
M. Abdi; Majid Ghaderi; N. Rashidnejad-Omran; A. Najafi
Abstract
Two cases of tungsten-copper vein-type mineralization have been studied in the Nezam-abad and Deh-hossein areas, in southwest of Shazand. The hydrothermal quartz-tourmaline mineralized veins have different host rocks (biotitic-granite and meta-sandstone). Considering similar ore metals (tungsten-copper-tin-lead-zinc) ...
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Two cases of tungsten-copper vein-type mineralization have been studied in the Nezam-abad and Deh-hossein areas, in southwest of Shazand. The hydrothermal quartz-tourmaline mineralized veins have different host rocks (biotitic-granite and meta-sandstone). Considering similar ore metals (tungsten-copper-tin-lead-zinc) in the Nezam-abad and Deh-hossein areas, same mineralogy of veins (quartz-dravite) and similar REE variation patterns in the two areas, it is suggested that the Nezam-abad and Deh-hossein mineralized veins have the same origin. It means, when the Br-bearing fluids were active, they caused the quartz-tourmaline vein-type mineralization in this area. Considering the barren intrusions in the area and other mineralogical-geochemical evidences in this study, it could be concluded that tungsten and other metallic elements in the Nezam-abad and Deh-hossein ore-bearing veins have a sedimentary/metamorphic origin.
G. Ghorbani; H. Ghasemi
Abstract
Bagho granitoid is located in the southeast of Damghan and has been cut by many quartz-tourmaline veins with about 1 mm to 30 cm thickness. Based on petrography and electron microprobe analyses, these tourmalines show schorl– dravite– foitite composition with a tendency toward schorl end ...
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Bagho granitoid is located in the southeast of Damghan and has been cut by many quartz-tourmaline veins with about 1 mm to 30 cm thickness. Based on petrography and electron microprobe analyses, these tourmalines show schorl– dravite– foitite composition with a tendency toward schorl end member, and located in alkali and vacancy groups. Compared with the ideal composition of schorl– dravite, many of tourmaline samples have high Al contents and alkali – site vacancies. The increase in octahedral aluminum reflects a combination of substitutions in tourmaline involving deprotonation (O–OH exchange) and vacancies in the alkali-site and then they have magmatic origin. In contrast, the presence of zoning, its occurrence as vein form, having high Mg compared with Fe in some samples and tendency away from alkali- deficient and proton– deficient tourmaline vectors, show that these tourmalines have hydrothermal origin. Then, based on these results, it appears that tourmaline veins form by interaction of boron-rich magmatic-hydrothermal fluids of granitic-dacitic provenance with various quartz-tourmaline and metapelitic-metapsammitic host rocks.
A. Zohdi; M. H. Adabi
Abstract
Carbonate sequences of the Taleh-Zang Formation mainly consist of large benthic foraminifera (e.g., Nummulites and Alveolina) along with other skeletal and non-skeletal components. In this formation, the water depth during deposition was determined based on the variation and different types of benthic ...
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Carbonate sequences of the Taleh-Zang Formation mainly consist of large benthic foraminifera (e.g., Nummulites and Alveolina) along with other skeletal and non-skeletal components. In this formation, the water depth during deposition was determined based on the variation and different types of benthic foraminifera and other components in different facies. Microfacies analysis led to the recognition of 10 microfacies that are related to 4 facies belts such as: tidal flat, lagoon, shoal and open marine.The absence of turbidite deposits, reefal facies, gradual facies changes and widespread tidal flat deposits indicate that the Taleh-Zang Formation was deposited in a carbonate ramp environment. Due to the great diversity and abundance of larger benthic foraminifera, this carbonate ramp is referred to as "foram-dominated carbonate ramp system". Comparison between elemental and isotopic compositions of biotic (benthic foraminifera) and abiotic (micrite) components in Taleh-Zang Formation shows an equilibrium condition due to minor biological fractionation and kinetic effects such as growth rate or other unknown factors. Thus, palaeotemperature calculation of seawater based on heaviest oxygen isotope values of biotic and abiotic carbonates are similar. Petrographic and geochemical studies illustrate that these carbonates were affected by weak meteoric digenesis in a closed diagenetic system with a low water/rock interaction.
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.
M. H. Adabi; M. Khatibi Mehr; A. Moallemi; A. Sadeghi; M. A. Salehi
Abstract
The Ziyarat Formation is an Upper Paleocene to Middle Eocene carbonate sequences, located in North of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 212.5 m conformably overlies the Fajan conglomerate and is overlain by greenish tufaceous ...
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The Ziyarat Formation is an Upper Paleocene to Middle Eocene carbonate sequences, located in North of Tochal Village (south-east of Tehran), near Emam Zadeh Abdollah. The Ziyarat Formation with the total thickness of 212.5 m conformably overlies the Fajan conglomerate and is overlain by greenish tufaceous siltstone of the Karj Formation. Petrographic studies led to the recognition of 11 microfacies. Different facies and evidences such as the absence of reefal facies, calciturbidite deposits, and widespread tidal flat deposits indicate that the Ziyarat Formation was deposited in a homoclinal carbonate ramp environment. Micritization, cementation, compaction, neomorphism, dissolution, dolomitization, fracturing and silicification are the major diagenetic processes in the Ziyarat Formation, occurring in meteoric and burial diagenetic environments. Major and minor elements and oxygen and carbon isotope values indicate that Ziyarat carbonates were deposited in a shallow warm water tropical environment and original carbonate mineralogy was aragonite. Bivariate plots of Mn versus Sr/Ca and δ18O illustrate that Ziyarat limestones were affected by open system diagenesis with high water/rock interaction. Early burial diagenetic temperature calculation based on heaviest oxygen isotope values of micrite and δw of Eocene seawater of 0.85 SMOW, shows that temperature was around 39˚C. Cathodluminescence studies of carbonate cements illustrated dull luminescence, because these carbonates afftected by both meteoric and burial diagenesis, and thus typical yellow to orange luminescence and zonations, evidence of meteoric diagenesis, are absent. This statement is confirmed by isotropic evidences.
