فهرست مطالب بهنام شفیعی

Sulfur source tracing based on of sulfide (galena and pyrite) and sulfate (barite) mineralization in fluorite deposits of Elika Formation (East of Mazandaran Province) is studied. In present research. δ34S values vary between -1.82 – +12.49 ‰, +13.22 – +25.83 ‰ and +22.69 – +32.91 ‰ for galena, pyrite and barite, respectively. Regionally, although wide range of δ34S in sulfides is interpreted as isotopic heterogeneity of source and/or processes of reduced sulfur supply for sulfide mineralization in the studied area, but each deposit has narrow range of δ34S. Compared to sulfides, barites show isotopic homogeneity in heavier δ34S which are corresponding to evaporates from coexisted sea water (Middle-Upper Triassic; Paland Formation). Based on stratigraphic and mineralogical data of host rocks, co-existing evaporates of Triassic sea water and also diagenetic primary sulfates in matrix of host rocks (anhydrite, gypsum, barite) are introduced as the most probable sources of sulfur for sulfide mineralization in Shesh Rodbar and Era deposits. In contrast, contribution of organic matter and/or diagenetic primary pyrites had main role in generation of light δ34S values in Pachi Miana and Kamarposht deposits. Thermo-chemical reduction of digenetic primary sulfates and thermal decomposition of diagenetic primary sulfides as well as sulfur bonds in organic matter-bearing laminaes in the host rock are introduced as main processes for reduced sulfur supply in sulfide mineralization.

Upper parts of Elika carbonate Formation belonging to middle Triassic in central part of structural- sedimentary zone of Alborz in East of Mazandaran province (Savadkuh, Khatirkuh and Kiasar regions) are hosted some of important F-Pb-Ba ore deposits contain of PachiMiana, SheshRudbar, Era(Alikola) and Kamarposht. Based on of field observations in study, main localization of ore bodies within carbonate rocks are as acrostic, irregular, and discordant respect to bedding that are displayed in fractures and/or karstic cavities in the form of vein, lenses and bodies. Mineralogy in studied ore deposits generally is simple and mainly composed of galena, barite, fluorite, calcite and minor sphalerite. Macroscopic and microscopic observations are shown variety of syngenetic and epigenetic structures and textures. Disseminate, stylolite and micro-veinlet textures of galena and calcite with or without other mainly minerals are recognized as syn-genetic textures respect to host rocks. Epigenetic structures and textures as open space filling type such as vein-veinlet, zebra, lamination, primary replacement and colloform are dominant textures of high-grade ores that formed main and economic zones of ore body concentration in deposits. Existence of secondary textures such as curvature and wind in triangle cleavage of coarse-grained galenas and also replacement of galena by cerussite and covellite show deformation and supergene oxidation after the main stage of mineralization. Based on current research, mineralization in F-Ba-Pb ore deposits of central Mazandaran is formed and evolved at two steps (1) primary or syn-diagenetic, and (2) main or epigenetic. According to structural signatures of ore body appearance in deposits environment and also textural evidences in macroscopic and microscopic scales, the main and economic stage of mineralization in studied ore deposits is introduced as epigenetic.

Present study is the first report of the rhenium and osmium isotopic data in the hypogene Cu-Fe sulfides (chalcopyrite and pyrite) from the Kerman porphyry copper deposits. Although data set was limited in this study, their interpretation helped to understand the possible sources of the metal for mineralization in the porphyry copper system. Based on this study, initial 187Os/188Os value in deposits recorded at least 0.1 to maximum 10 that the variation range for this ratio is much larger than the range detected in the Chilean porphyry copper deposit (from 0.15 to 5.2). The recorded non-radiogenic to radiogenic values for initial osmium ratio in primary sulfides of the Kerman porphyry copper deposits revealed isotopic heterogeneity and diversity in metal source for mineralization in these deposits. The record of the non-radiogenic values for initial 187Os/188Os (0.10- 0.15) in sulfides of the Miduk and Now Chun deposits, in the range of mantle values (0.13- 0.15), showed the main role of ore-forming fluids derived from mantle-derived magma (intrusive body) for supplying of the metal required for mineralization in these deposits. In contrast, too large deviation observed in initial 187Os/188Os values in sulfides of the Kerver (10) and Abdar (1) deposits respect to the mantle values showed the greater share of crustal sources (continental crust) rather than mantle sources in supplying of the metal for mineralization in these deposits. The Sar Cheshmeh deposit revealed less radiogenic value of initial osmium ratio in potassically sulfides (0.22) respect to phyllically sulfides (0.79), showing the contribution both the mantle and the crustal materials in supplying of the metal for mineralization, although the role of crust during the final stages of mineralization has been more important. The observed general trend in 187Os/188Os values being more radiogenic from old, high-grade deposits (middle Miocene) to young, low-grade deposits (upper Miocene- Pliocene) in the Kerman porphyry copper belt is attributed to increasing of the crustal sources contribution in generation of the young sub-productive-to-barren magmas and also in supplying of the metal for associated weak mineralization. This relationship can be suggested as a key for distinguishing and exploration of porphyry copper deposits with economic grades, the deposits that have been inherited greater share of the mantle source for generation of productive magma and also required metal for mineralization in porphyry system.

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 thepresent 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 Moin 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 quartzmolybdenite 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.

The Alborz structural zone in northern Iran is the host of a number of bauxite deposits. The Gheshlagh bauxite deposit is one of them with more than 2 km long and a thickness of about 20 m in the eastern part of the Alborz structural zone. This deposit has been developed as a stratiform horizon along the contact zone of Permian limestones and Triassic dolomitic limestones. The basal contact zone of the bauxite horizon is mainly undulatory, whereas the upper contact zone is concordant with the hanging-wall dolomitic limestones. Based on mineralogical and textural evidences, the horizon can be divided from top to bottom into five distinct units: (1) upper bauxite unit with a thickness of about 5 m, is composed of boehmite, hematite, kaolinite, rutile and svanbergite, 2) upper kaolinite unit approximately 2-3 m thick and is composed mainly of clay minerals, 3) hard bauxite unit with a thickness of approximately 1.5 m, mainly consists of hematite, kaolinite, boehmite and diaspore, 4) lower kaolinite unit approximately 1-4 m thick and is composed of kaolinite, boehmite and diaspore, and 5) lower bauxite unit about 4-6 m thick. Textural analyses indicate both allochthonous and autochtonous origins for these deposits. Combination of geological, textural and mineralogical data of the Gheshlagh bauxite deposit correspond to a boehmitic-diasporic karst bauxite deposit type.   

Productive and non-productive intrusive of Oligocene-Miocene age with similar mineralogical composition in Kerman porphyry copper belt exhibited important geochemical differences in terms of trace and rare earth element geochemistry. The productive intrusives are best characterized by low contents of MnO (≤0. 1 wt. %)، Y (≤18ppm)، ΣHFSE (≤100ppm)، heavy rare earth elements (Yb≤1. 9 ppm)، high Sr content (≥406-1015ppm)، high (Sr/Y≥30)، significant REE fractionation (La/Yb≥20)، as well as positive Eu anomalies (Eu/Eu≥1)، when compared with non-productive intrusives (MnO≥0. 1wt. %،Sr=184-576ppm،Y=12-50ppm، Sr/Y<30، La/Yb<15،Eu/Eu*<1). These signatures are indicative of hydrous and oxidized magmas that formed in a condition which has been different from that of the non-productive intrusives. Based on the present study، the discrimination diagrams which can be used as a tool for identification of productive intrusives، where they are accompanied by nonproductive intrusives، in other copper provinces in Iran، are as follows: MnO-Y، ΣHFSE-Y، Sr/Y-Y، Sr/Y-SiO2، La/Yb-SiO2، La/Yb-Yb، Eu/Eu*-SiO2.

Paleosols of the study area is a part of the Eastern-Alborz Zone which is located about 50 km southeast of Azadshahr. These paleosols developed on floodplain and lacustrine facies of the Devonian Padeha Formation. Based on the field and textural evidences, two major paleosol horizons identified as A and B horizons. The A horizon consists of calcrete and noncalcrete paleosols which is located in the floodplain facies of the Padeha Formation. The B horizon identified in the lacustrine facies and consists of calcrete paleosols. Quartz, calcite, dolomite, microcline, hematite, albite, sericite, illite, chlorite and montmorilonite were identified in the paleosols. Geochemical analyses of the paleosols reveal the enrichment of immobile elements and depletion of mobile elements. Investigations of chemical alteration and effective chemical alteration indices indicate intermediate weathering in the study area. The occurrences of noncalcrete and calcrete paleosols suggest a climate change from humid to dryer condition occurred during soil formation. Combinations of textural, mineralogical and geochemical data indicate an origin of basic igneous rocks for the paleosols of the study area.

In present study، Re concentration determined in 30 hexagonal (2H) and trigonal (3R) molybdenite samples belong to veinlets of different stages of hypogene mineralization from 7 porphyry Cu and Mo deposits from Kerman region. Re concentration in molybdenites of these ore deposits varied from 49 g/t to 1449 g/t which are in Re concentration range of other porphyry Cu and Mo deposits around the world. In general، 3R molybdenites show the higher Re concentration (average ~ 563 g/t) than those of 2H molybdenites (average ~ 479 g/t). Variations of Re concentration in molybdenite types deposited during different stages of hypogene mineralization indicate more concentration of Re in molybdenites precipitated with transitional (B-type veins) and late (D-type veins) stages of mineralization than those of early stage veinlets (A-type veins). This distribution suggest that Re with more acidic and cooler hydrothermal fluids at the transitional and the late stages of porphyry system evolution is more concentrated with silicification، sericitization، and argillization alterations. Present study indicated that molybdenites with high Re content are associated with porphyry copper deposits which are characterized by low average grade of Mo، limited contents of molybdenite، and also their productive intrusive is resulted from significant contribution of mantle-derived magmas respect to crustal materials. In addition to abovementioned signatures، frequency of 3R poly-type of molybdenite in ore deposits، less fractionated and more calcic composition of productive intrusive of ore deposits with their less radiogenic of Sr and Pb isotope ratios، as well as occurrence of late stages of acidic and low temperature hydrothermal alteration and mineralization processes in formation and evolution history of ore deposits are signatures of porphyry copper and molybdenum deposits with high Re contents.

The Argash antimony ore deposit is located at south of Neyshabour and the eastern part of the Sabzevar zone. This deposit occurs within a sequence of Eocene-Oligocene volcanic-intrusion rocks. The mineralization occurs as open space filling, taking place as irregular veins, veinlets and hydrothermal breccias. The mineralogy of the veins is comparatively simple. The primary antimony-bearing mineral is stibnite. Other sulfides have been found in association with stibnite are pyrite, chalcopyrite and sphalerite. Quartz, illite, adularia, chlorite, epidote and kaolinite are the main hydrothermalg gangue minerals occurring around the veins. Hydrothermal alteration is zoned around the veins and consists of three major types including silicification within the immediate veins, argillic alteration enveloping the veins, and propylitic alteration distal to the veins. The intensity of silicification and argillic alteration decreases with depth and away from the veins. The evaluation of the geochemical data set based on multivariate statistical analyses indicates positive correlation between Zn, Ag, As and Sb and the same distribution pattern of these elements in the boreholes. The mineralogic, alteration and geochemical characteristics of the studied area and comparison with epithermal ore deposits indicate that the Arghash quartz-antimony veins represent an epithermal system of the low-sulfidation type. This data suggests that boiling and cooling were the main ore deposition processes in the area.

In order to assess the potential of copper mineralization and its associated elements in Soltan Meydan basaltic formation situated in the north of Shahrud، the method of stream sediment and heavy mineral has been used. To achieve this aim، totally 68 samples of sediments (-80 mesh in particle size) and 6 samples of heavy minerals (-20 mesh in particle size) have been collected in an optimized network of sampling. Stream sediment samples have been analyzed in for Cu، Pb، Zn، Co، Mn، Fe and Ni. Statistical processing of geochemical data resulted in identifying of elements with anomaly values، discrimination between anomalous and background values، and also assigning the inter-element relationships. Among the elements، Cu and Ni show first and second order anomalies in the samples. Results show that Fe، Pb، and Zn are associated together and also indicate positive correlation with Co and Mn، strongly (r≥0. 5). The study of heavy mineral samples indicates the presence of magnetite، hematite، goethite، limonite، pyrite، oxidized pyrite، ocher، barite، apatite، rutile، zircon، nigrine، anatase، sphene، leucoxene، gold and ferromagnesian silicates. Statistical processing of heavy mineral data shows the association of Au، Ti، and Fe-oxides. The results of geochemical data processing and their integration with results of distribution pattern of fractures indicates good correlation between geochemical anomalies and highly fractured regions، as a result promising area for Cu and Ti mineralization has been identified and suggested for performing of further exploration.

The Gheshlagh bauxite deposit is located 110 km southeast of Gorgan. The deposit has been developed as a stratiform horizon with more than 2 km length and a thickness of about 25 m along the contact of Ruteh and Elika carbonate formations. Textural analysis indicates both allochthonous and autochtonous origins for the bauxites. Bohemite, diaspore, anatase, rutile, hematite, goethite, kaolinite, svanbergite, pyrite, and quartz were identified in the ore paragenesis. Based on textural and mineralogical evidence, the deposit can be divided into five distinct units including upper bauxite, upper kaolinite, hard bauxite, lower kaolinite and lower bauxite. Accumulation coefficients of trace elements and geochemical indices such as Ti/Cr, TiO2/Al2O3, Zr/Ti and Nb/Y, combined with the geological evidence suggest the basaltic rocks of the Soltanmeidan Formation as the main source of bauxite materials. Combination of mineralogical and geochemical data shows that the deposit formed in two main stages. First, bauxite materials, Fe and Ti oxides and clay minerals developed as authigenic bauxitization processes of basaltic parent rock. Then, these materials were transported to karst depressions and were accumulated as a bauxite horizon.

The Emarat and Muchan zinc-lead ore deposits are located in southwest of Arak within the middle part of the Malayer-Esfahan belt. These deposits have formed as stratabound within carbonate strata of Lower Cretaceous. Mineralization in these deposits is mainly open space filling, which consists of sphalerite, galena, pyrite and minor quantities of chalcopyrite associated with host rock silicification. The most abundant sulfide mineral is sphalerite, which occurs in two generations. Galena as an accessory mineral has been formed during and after formation of sphalerite. Based on textural evidence, silicification occurs in two separate stages. First, microcrystalline quartz replaces nearly all the original carbonate host rock. During the second stage, the vugs and fissures of the silicifed host rock were filled with macrocrystalline quartz associated with mineralization. The sulfur isotopic data indicated the δ34S values of sulfide minerals varies from +4.8 to +11.8 per mil. Based on these results, the Lower Cretaceous seawater acted most likely as the source of sulfide mineralization. The isotopic temperatures from two sphalerite-galena pairs at Emarat deposit varied from 121.1˚C in stage I to 112.8˚C in stage II, which are lower than the isotopic temperature of the Muchan deposit (134.3˚C). Combination of geological, mineralogical and sulfur isotope results suggest that connate water, metals and silica have been derived from diagenesis of Jurassic shales and sandstones. Furthermore, thermochemical sulfate reduction, interaction of the ore fluids with the host rock, and cooling were proposed to be the main ore depositional mechanisms.

Kerman Cenozoic magmatic arc has gone through a different tectonic and magmatic evolution from that of central and northwestern parts of the Urumieh-Dokhtar volcanic belt and has particularly been influenced by the subduction of Neo-Tethys oceanic crust to the east of Nain-Baft transform fault beneath the rotating central Iran micro-continent and its surrounding circum ocean. The arc magmatic activities started from early Eocene with extensive volcanism of Bahr Asemen and Razak complexes which are characterized by silica-satureated magmas with ranges mafic to felsic compositions without feldspathoides, calc-alkaline and locally tholeiitic-like affinity, low enrichment in LILE, weak to moderately REE fractionation (La/Yb<20), non-radiogenic Sr isotopic ratios (0.7041-0.7049), and high? Nd (6-2.3).

Based on this study, the avcfiige gold and silver graJcs in the SaT Chesbmeh porphyry copper deposil arc 0.06 and 1.22 gil re.chr('39')ipcct ivcly which arc very different from the o nes repon ed previously. In the bioti lic andes ite and a!ICrcd phyllic/potassic samples from the siock, the high positin: correlation between the hypogene copper and gold grades ( r=0.81 ), and gold chr('39')lIld silw.f grades (1"=0.6 1), and gold and si lver with the hypogene copper grade (r;:::U.72), indicatc:( I) the contemporaneous deposition of C(lpper, gold ami silver, <lnd (2) gold is probably prescnt in the form of exsolution, invisihle solid solution and nalive or elect rum within the chalcopyri te gwins. Within the secondary sulfide enrichment zone, the gold grade is two times more than the hypogene grade, Silver also indicates the highest concentration within the lellched/oxidc and secondary sulfide enrichment w nes. This st udy indicm(:s th ~l t the Sar Chcshmeh deposit is a gold and silver poor porphyry COPP!;;I - molybdenum deposit.