جستجوی مقالات مرتبط با کلیدواژه « pb » در نشریات گروه « زمین شناسی »

Separation of geochemical anomalies from the background has always been a major concern of exploration geochemistry. The search for methods that can make this analysis quantitative and objective aims not only at the reduction of but also at providing an automatic routine in exploration, assisting the interpretation and production of geochemical maps (Nazarpour et al., 2015). The Malayer-Isfahan metallogenic belt with the north-west-south-east trend is the largest and most important Pb-Zn belt of MVT type in Iran (Rajabi et al., 2012). In this study, separation of Pb and Zn geochemical anomalies was performed using the methods named further in the study area.

1. Classical statistics Various statistical methods have been used to process geochemical data in order to determine threshold values. Statistical quantities, such as the mean, standard deviation (SDEV) and percentiles, have been used to define thresholds for separating anomalies form the background. For example, geochemical anomalies have been defined as values greater than a threshold value defined as the 75th or 85th percentile, and Mean+SDEV or Mean+nSDEV (Nazarpour et al., 2015). The boxplot and median+2MAD techniques of the EDA approach have been widely used to separate geochemical anomalies from the background. In exploratory data analysis (EDA) of geochemical exploration data, the median+2MAD value was originally used to identify extreme values and serve as a threshold for further inspection of large data sets (Carranza, 2009). The MAD (is the median of absolute deviations of individual dataset values (Xi) from the median of all dataset values (Tukey, 1977). 2. Multifractal models Fractal and multifractal models have also been applied to separate anomalies from background values. These methods are gradually being adopted as effective and efficient means to analyze spatial structures in metallic geochemical systems (Cheng et al., 1994). The concentration-number (C-N), concentration-area (C-A) multifractal methods have been used for delineation and description of relations among mineralogical, geochemical and geological features based on surface and subsurface data (Nazarpour et al., 2015). Fractal/multi-fractal models consist of frequency distribution and spatial self-similar or self-affine characteristics of geochemical variables. These fractal/multifractal models have been demonstrated to be effective tools for decomposing geological complexes and mixed geochemical populations and to recognize weak geochemical anomalies hidden within strong geochemical background (Cheng et al., 1994).3. Singularity Index (SI) The Singularity technique is another important process for fractal/multifractal modeling of geochemical data (Zuo et al., 2015). This technique is defined as the characterization of the anomalous behavior of singular physical processes that often result in anomalous amounts of energy release or material accumulation within a narrow spatial–temporal interval. The Singularity can be estimated from observed element concentration within small neighborhoods based on the following equation (Cheng, 2007): (1) The Singularity Index is a powerful tool to identify weak anomalies, but it is influenced by the selection of the window size. (Zuo et al., 2015).

In this study, a total of 19946 stream sediment geochemical samples were analyzed using the ICP-MS and XRF methods. In the maps derived from the Singularity Index (SI) the higher accuracy of this method compared to other applied methods was employed. Therefore, the hidden and weak anomalies are better represented, and a better overlap with limestone as the major host rock of Pb and Zn deposits (MVT type) in the study area were observed. A comparison among all of the applied methods indicates that the concentration of Pb and Zn increased toward the and south east and northwest parts, respectively. In these regions there is a high potential for the occurrence of promising mining areas. Moreover, the obtained Pb and Zn anomalies have a good correlation with the exposure of limestone in the study area.

The Khondab 1:100000 geological map as one of the high-potential areas for Pb and Zn ore deposits is located in the northern part of the Malayer-Aligudarz-Isfahan metallogenic belt in iran. In this study, classic statistical, Singularity Index analysis, remote sensing, weight of evidence (WofE) and structural analysis methods, have been applied for the separation of geochemical anomalies from background of the Pb and Zn metals in the studied area. In general, 2006 stream sediment geochemical samples analyzed using the ICP-MS method have been used. the classic statistical method (Mean+nSTEV) indicates that the threshold values for the Pb and Zn metals 30.75 ppm and 153.18 ppm, respectively. In the maps derived from the Singularity Index (SI) hidden and weak anomalies are better represented, and a better overlap with limestone as the major host rock of Pb and Zn deposits (MVT type), fault density and alterations in the study area are shown. Moreover, the anomalies obtained from this method high overlap with the Pb and Zn mines and deposits in the region. In general, in this study, it has been founded that lead in the south and northeast, and zinc in the northeast and center of the region exhibit the highest anomaly, in which the probability of the presence of MVT deposits is very high. On the other hand, the obtained anomalies show a high correlation with the Cretaceous limestone units and fault zone of the region, which are directly related to the Pb and Zn mineralization.

Pb mineralization in Horeh area is located in 25 km northeast of Shahrekord, the middle part of Sanandaj-Sirjan zone in the mineralization belt of Malayer-Isfahan, in the geology map of 1/100000 of Chadgan (Ghasemi et al., 2005). There are nine mineralization belts, and 120 index mineralization of Pb-Zn has been identified based on paragenesis of mineralogy, time and type of mineralization in the Sanandaj-Sirjan zone. The Malayer-Isfahan mineralization belt is in the middle part of the Sanandaj-Sirjan zone, which formed in Mesozoic in carbonate sequences along with deep faults (Shahabpour, 1385). Often, this type mineralization is similar to Mississippi Valley-type (MVT) Pb-Zn deposits that many of these deposits have been created simultaneously with orogeny so that topographic slope is an essential factor in the ore fluids displacement (Leach et al., 2005, 2003, 2001; Appold and Gruven, 1999). The lithostratigraphy units in Horeh area include dolomite and limestone Permian, conglomerate, sandstone and shale Jurassic, limestone cretaceous, low grade metamorphic and young alluvium. The primary trend of the structure of the Hore Pb mineralization is NW-SE as same as the trend of the Sanandaj-Sirjan zone and the Zagros fault. This paper aims to identify the geological, geochemical and petrogenesis of the Pb mineralization on the base of the mineralogy, geochemistry, geophysics and fluid inclusion data. 

There are taken 35 samples and the number of 10thin section and 5 polished sections were prepared and studied in order to petrography and mineralogy. Major oxides (XRF method) elements were analyzed for 5 samples. 3 samples (calcite) were selected for Fluid inclusion study by linkam THMS-600 in Isfahan University. Data Geophysics was taken by  IPRSw-888 set and was measured Rs, Ip, Sp. 

Horeh Pb Mineralization occurred as lens and veins with a thickness of several centimeters to several meters in sedimentary rocks, with slopes and stretches of NW-SE and angle of 45°. This deposit is sulfide-type consists of galena, pyrite, and chalcopyrite as the primary ore and malachite, calcite and iron oxides as gangue. There are observed galen as fine-coarse grain, euhedral to xenomorph with triangular cleavage cavities, pyrite, and chalcopyrite as finely-coarse-grain, calcite as open space filling and comb texture, and veins in other rocks. Malachite often is formed by oxidation of the pyrite and chalcopyrite. Also, there are goethite, hematite, magnetite, illite, dolomite, and quartz. The mineralogical paragenesis sequence in Horeh area is two stages: the initial phase of the reduction that caused to deposit the sulfide minerals such as galena, and the second phase of the oxidation, which led to the formation of oxides and hydroxides minerals by initial carbonate and silicate minerals. Based on geochemical data, SiO2 =38.31% indicates to low maturity of sedimentary rocks compared to the upper crust (Taylor and McLennan, 1985; SiO2 = 64.8%). The high mean value of CaO = 25.22% (upper crustal crust = 4.19%) indicates to high amounts of carbonate cement, which cause to decrease of the relative amounts of SiO2 and Al2O3 in the samples. Al2O3 amounts are due to the clay and mica and Al-rich mineralogy, especially illite (Elsass et al., 1997). Fluid inclusion data of mineral calcite indicate to the two-phase of the fluid include (L + V) with irregular shapes in the size of 4 to 10 μm, and 136.6 ° C average homogeneity, -14.5° to -20° ice melting and 20.15% average salinity ( weight equivalent to NaCl)( Bodnar,1993). The result of fluid inclusion indicates to the basinal brines that is similar to the Pb deposits of the Mississippi Valley type. Geophysical investigations identified 4 Pb anomalies in the region, which begins at depths of 10 m and extends along NS and steep slope toward the west to the depth of 50 m by measure chargeability (PI), electrical resistivity (RS) and metal coefficient map (FM). 

The Pb mineralization in the Horeh area is as Galena with chalcopyrite and pyrite. Based on field study and petrography data, Galena is the main mineral and carbonate, and silicate minerals are gangue. Pb Mineralization has occurred as the replacement, bedding and tangential in the Jurassic formations by basin brine fluid.  The combinations of field study and mineralogy, geochemical and geophysical data indicated to the similarity Pb deposit of the Horeh to the Mississippi type that was formed during the two-stage reduction and oxidation. Geophysical data were indicated to the, 4 Pb anomalies from 10 m the topography level with 50m thick with the steep slope to the west.

1-Introduction Separation of geochemical anomalies from background has always been a significant concern of exploration geochemistry. The search for methods that can make this analysis quantitative and objective aims not only at the reduction of subjectiveness but also at providing an automatic routine in exploration, assisting the interpretation and production of geochemical maps (Nazarpour et al., 2016). Arak 1:100000 geological sheet is located in the north of Malayer-Aligoudarz-Efsahan Pb-Zn metalogenic belt, so this sheet has been studied. In this study, we compared the methods of classical statistics (Mean+2SDEV), exploratory data analysis (MAD), concentration-number (C-N) and concentration-area (C-A) fractal models. Also, singularity index models were used to separate the Pb and Zn anomalies in Arak 1:100000 geochemical sheet. The results of mentioned methods, showed that the singularity index method has a higher accuracy. Also, indicates the higher concentration of Zn in area of study. 2-Methodology 2-1 Classical statistics Various statistical methods have been used to process geochemical data in order to determine threshold values. Statistical quantities, such as the mean, standard deviation (SDEV) and percentiles, have been used to define threshold for separating anomalies form background. For example, geochemical anomalies have been defined as values higher than a threshold defined as the 75th or 85th percentile, and Mean+SDEV or Mean+2SDEV (Nazarpour et al., 2015). 2-2 EDA (Exploratory Data Analysis) In exploratory data analysis (here after named EDA) of geochemical exploration data, the median+2MAD value was initially used to identify extreme values and act as threshold for further inspection of large data sets (Carranza, 2009). The EDA was first established by Tukey (1977), was developed further by, and then was used by many researchers in modeling of geochemical anomalies (Carranza, 2009). The MAD is the median of absolute deviations of individual dataset values (Xi) from the median of all dataset values (Tukey, 1976): (1) MAD = median 14 [│Xi-median Xi│]"> 2-3 Multifractal Fractal and multifractal models have also been applied to separate anomalies from background values. These methods are gradually being adopted as an effective and efficient means to analyze spatial structures in metallic geochemical systems (Afzal et al., 2017). The concentration-number (C-N), concentration-area (C-A) multi-fractal methods has been used for delineation and description of relations among mineralogical, geochemical and geological features based on surface and subsurface data (Nazarpour et al., 2015). Fractal/multi-fractal models consist of the frequency distribution and the spatial self-similar or self-affine characteristics of geochemical variables and have been demonstrated to be useful tools for decomposing geological complexes and mixed geochemical populations and to recognize weak geochemical anomalies hidden within strong geochemical background (Cheng et al., 1994). 2-4 Singularity index The singularity technique is another vital progress for fractal/multifractal modeling of geochemical data (Zuo et al., 2012). It is defined as the characterization of the anomalous behaviors of singular physical processes that often result in anomalous amounts of energy release or material accumulation within a narrow spatial–temporal interval. The singularity can be estimated from observed element concentration within small neighborhoods based on the following equation (Cheng, 2007): (2) 14X=c·εa-E"> The singularity index is a powerful tool to identify weak anomalies, but it is influenced by the selection of the window size. When applying this method, one should use different window sizes to process the geochemical data and find an appropriate window size which can highlight the interesting results (Zuo et al., 2012). 3- Results and discussion Threshold values obtained using mentioned methods were used to map the spatial distribution of element concentrations. These interpolated maps were produced by means of inverse distance weighted (IDW) method (Nazarpour et al., 2016). In classical statistics and MAD methods, anomalies are usually detected, regardless of the location of each instance, and only by formulating relationships (Hashemi marand et al., 2018). In these methods, it is possible that some of the proposed ranges are false anomalies (Tukey, 1977). The geochemical anomalies of the Pb and Zn elements were separated using fractal methods of concentration-number (C-N), concentration-area (C-A), and according to the fitting line of each element on the logarithmic graphs. The singularity index estimated through a small window mainly reflects the fluctuation of the element concentration (Afzal et al., 2017). The singularity index estimated through a large window mainly reflects regional changes but it does not focus on the local weak anomalies (Zuo et al., 2012). There is probably a significant effect of the contact between exposed bedrock and covered areas, or there could be other deterministic trends as well, which should be studied further (Cheng, 2007). The results of the named methods are shown in Fig. 1. 4-Conclusions Singularity index analysis, indicated that the hidden anomalies are better coincidence with indices and mineral deposit occurrence in the study area. In general, the comparison between these methods indicate that the concentration of Pb and Zn increased toward the and southwest and south-northeast parts, respectively. In these regions there is high potential for the occurrence of promising mining areas. Moreover, the obtained Pb and Zn anomalies have a reasonable correlation with the exposure of limestone in the study area, which is a suitable host rock for the formation of MVT type Pb and Zn deposits. a b c d e Figure 1. Maps of spatial distributions of Pb, Zn elements. a) Classic statistics, b) MAD, c) Multifractal (C-N), d) Multifractal (C-A), e) Singularity index References Afzal, P., Ahmadi, K., Rahbar, K., 2017. Application of fractal-wavelet analysis for separation of geochemical anomalies. Journal of African Earth Sciences 128, 27-36. Carranza, E.J.M., 2009. Controls on mineral deposit occurrence inferred from analysis of their spatial pattern and spatial association with geological features. Ore Geology Reviews 35(3-4), 383–400. Cheng, Q., 2007. Mapping singularities with stream sediment geochemical data for prediction of undiscovered mineral deposits in Gejiu, Yunnan Province, China. Ore Geology Reviews 32, 314- 324. Cheng, Q., Agterberg, F.P., Ballantyne, S.B., 1994. The separation of geochemical anomalies from background by fractal methods. Journal of Geochemical Exploration 51(2), 109-130. Hashemi marand ,G., Jafari, M., Afzal, P., Khakzad, A., 2018. Determination of relationship between silver and lead mineralization based on fractal modeling in Mehdiabad Zn-Pb-Ag deposit, Central Iran. Journal of Earth Sciences 27, 111-118.‎ Nazarpour, A., Paydar, G.R., Carranza, E.J.M., 2016. Stepwise regression for recognition of geochemical anomalies: Case study in Takab area, NW Iran. Journal of Geochemical Exploration 168, 150-162. Nazarpour, A., Sadeghi, B., Sadeghi, M., 2015. Application of fractal models to characterization and evaluation of vertical distribution of geochemical data in Zarshuran gold deposit, NW Iran. Journal of Geochemical Exploration 148, 60-70. Tukey, J.W., 1977. Box-and-whisker plots. Exploratory data analysis 39-43. Zuo, R., Carranza, E.J.M., Cheng, Q., 2012. Fractal/multifractal modelling of geochemical data 122, 1–3.

The early Cretaceous sedimentary sequence in south of Yazd hosts numerous Zn-Pb-Ba mineralization horizons. The sequence based on the stratigraphic position, age and composition of the rocks, can be divided into tree lower, middle and upper parts. The lower part or Sangestan formation mainly formed from clastic sedimentary rocks such as conglomerate, sandstone, shale, siltstone and oolitic limestone. The thick Sangestan sedimentary sequence is well exposed resting unconformably on the Jurassic Shir-Kuh granite and metamorphic Shemshak Group. The middle part or the Taft formation include organic matter-rich shale, siltstone, limestone and dolomite. The upper part or the Abkuh (Darreh-Zanjir) formation comprised of shale, chert-bearing bedded limestone and marls, overlying concordantly on the Taft formation. The Zn-Pb-Ba mineralization horizons within the sedimentary sequence, based on stratigraphic position, relative age and type of host rocks involved the two horizons: the first horizon consisting of Mehdiabad, Farahabad and Mansourabad deposits, occurred in the lower part of the Taft formation and hosted by organic matter-rich shale, shaly limestone, siltstone, silty limestone and dolomite. The second horizon comprising Mehdiabad and Mansourabad deposits are hosted by black shale and chert-bearing bedded limestone locates within the middle part of the Abkuh formation.

The Ahangaran Pb-Ag deposit is located in the Hamedan province, west Iran, 25 km southeast of the city of Malayer. . The deposit lies in the strongly folded Sanandaj-Sirjan tectonic zone, in which the ore bodies occur as thin lenses and layers. The host rocks of the deposit are Early Cretaceous carbonates and sandstones that are unconformably underlain by Jurassic rocks. Ore minerals include galena, pyrite, chalcopyrite, pyrrhotite and supergene iron oxide minerals. Gangue minerals consist of barite, dolomite, chlorite, calcite and quartz. The mineralization occurs as open-space fillings, veins, veinlets, disseminations, and massive replacements. Alteration consists of silicification, sericitization, and dolomitization. In this study, we carried out studies of mineralogy, microthermometry of fluid inclusions and sulfur isotopes to determine the source of sulfur and the physico-chemical conditions of formation. Seventy samples of different host rocks, alteration, and mineralization were collected from surface outcrops and different tunnels. Twenty of the samples were prepared for mineralogical studies at Tarbiat Modarres University in Tehran and 25 for petrological studies at the University of Bu-Ali Sina. Fluid-inclusion studies were done on 5 samples of quartz and calcite at Pouya Zamin Azin Company in Tehran using a Linkam THM 600 model heating-freezing stage (with a range of -196 to 480ºC). The accuracy and precision of the homogenization measurements are about ±1°C. Salinity estimates were determined from the last melting temperatures of ice, utilizing the equations by Bodnar and Vityk (1994) and for CO2 fluids using equations by Chen (1972). Nine samples of sulfides and barite were crushed and separated by handpicking under binocular microscope and powdered with agate mortar and pestle. About one gram of each sample was sent to the Stable Isotope and ICP/MS Laboratory of Queen’s University, Canada for sulfur isotope analysis. The sulfur isotopes in sulfides and sulfates were run on a Thermo Finnigan Delta Plus XP IRMS mass spectrometer. The analytical uncertainty for δ34S is ±0.2‰. The main types of fluid inclusions in quartz and calcite are as follows: I: dominant liquid + less vapor (L+V); II: dominant vapor + less liquid (V + L); III: liquid + vapor+ CO2 (L+V+CO2)(L+V)); IV: CO2 (L+V); V: liquid + vapor + sylvite (L+V+Sy). Homogenization temperatures of primary fluid inclusions indicate that mineralization occurred at temperatures ranging from 130 to 320 °C (ave., 200°C) and their salinites range from 10 to 15 wt % NaCl equiv. The temperatures and salinities of the mineralizing fluids of the Ahangaran deposit are similar to the Irish type Zn-Pb deposits, and suggest a similar origin. The δ34S values of pyrite and galena are within the range of -25.5 to +11.6 ‰ and -6.3 to -8.5 ‰, respectively and for barite are in the range of 26 to 27.2 ‰. These values indicate that the δ34SH2S values of fluids in that deposited the pyrite and galena are within the range of -6.4 to-2.9 ‰ and 9.4 to 27.9 ‰, respectively. The δ34S values of marine sulfate were 13 to 20 ‰ during the Cretaceous (Hoefs, 2009). The δ34S values of barite are near to that of marine sulfate in the Cretaceous which indicate that the sulfate of the barite may have a marine origin. On the other hand, the δ34SH2S values of galena lie within a narrow range, suggesting that the main source of sulfur may be from thermochemical sulfate reduction (TSR). Acknowledgments: In this research, we thank Sormak Mines Company for its support during field work. We also thank Sormak Mines Managers, especially Mr. Khakbaz for his cooperation and support of this research. Parts of this research were supported by the research department of Bu-Ali Sina University. We also wish to express our appreciation of the isotopic analyses by Queen's University, Canada.

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.

The Aligudarz region is located in middle part of the Sanandaj-Sirjan Zone. During and before the Jurassic time, a variety of Cu, Fe, Zn-Pb and Ba mineralization are formed in this area due to tectono-magmatic activities. This diversity of mineralizations with volcano-plutonic activities caused some complexities and ambiguities in geology-metallogeny evolution of the region. In this way, the aim of this study was investigation of geological evolution and its relation with mineralization and tectono-magmatic evolution of the Aligudarz region. The field and petrographic observations show that mineralization composition consist of barite with sulfide minerals (chalcopyrite, pyrite and covellite) and Fe-oxides in the Farsesh deposit withPermian carbonate host rock in the Farsesh area; sphalerite, galena and chalcopyrite in the Jurassic phylite, slate and meta-sandstone host rocks (Gol-e Zard deposit) and Cu mineralization associated with andesite rocks. In order to approach these aims, sampling for petrographical and geochemical studies with ICP-MS was done from each ore body separately. In addition, the granitoid rocks of the region were considered. In the Gol-e Zard Zn-Pb deposit, REE pattern represent enrichment of LREEs and La/Lu>1. The metamorphic host-rocks show positive Ce and negative Eu anomalies, whereas sphalerite, galena, chalcopyrite and quartz show negative Eu and Ce anomalies. Lack of Eu anomalies indicates high Oxygen fugacity during the precipitation of these minerals. Therefore, according to similarity of REE pattern in host-rock and ores of the Gol-e Zard deposit, it seems REEs extracted from host rock and then added to mineralizing fluid. The chondrite normalized pattern of REEs in barite ores and its host rocks in the Farsesh deposit show LREE enrichment. The positive Eu and negative Ce anomalies indicate that hydrothermal fluids are the main fluids, which caused precipitation of barite inthe host rock. REE pattern of andesite rocks show the same magmatic source for these rocks. LREE enrichment in andesite samples, lack of Eu and Ce anomalies indicate that clinopyroxene and plagioclase were crystallized in the same time and Ce+3 extracted with other REEs from depositional environment. The chondrite normalized pattern of granite rocks in the region show LREE enrichment, negative Eu anomaly and lack of Ce anomaly, which can indicate that diffraction process was controlled by plagioclase crystallization during the granitoid generation. The chondrite normalized spider diagram show the same trend of depletion of HFSE and HRRE and enrichment of LREE and LILE for all of the samples, which represent occurrence of magmatism in the study area and indicate all of these mineralizations are related to the subduction zone. These studies indicate that there is geodynamically a genetic relation between mineralizing fluids and volcano-plutonic activities of the region during or before the Jurassic system.

The Kuh-e Dom intrusion with calc-alkaline nature, in the northeast of Ardestan is located in the central part of the Urumieh-Dokhtar Magmatic Arc and includes the felsic and intermediate-mafic units. The felsic unit consists of monzogranite, granodiorite, quartz monzonite and quartz monzodiorite, whereas the intermediate-basic rocks comprise gabbro, diorite, quartz diorite, monzodiorite and monzonite. The acidic dykes intruded this intrusion and its surrounding rocks. The various mafic microgranular enclaves of dioritic, quartz dioritic, monzodioritic and quartz monzodioritic composition exposed in the acidic rocks. The zircon U-Pb dating by the LA-ICP-MS method indicates that the ages of the felsic rocks, intermediate-mafic rocks, acidic dikes and enclaves are 51.1±0.4 Ma, 53.9±0.4 Ma, 49.95±0.64 Ma and 50.3±0.8 Ma respectively. These ages are in good agreement with the lower-middle Eocene age of the intrusive body, which is simultaneous with subduction of the Neotethys oceanic crust underneath the Central Iran. This result is in agreement with the previous geochemical result.

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.

The Takht- e baz granitoid in the northwest of Birjand is cropped out in the vicinity of pyroclastic units composing of tuff، marly tuff and breccia. Petrography and major elements analysis show that this intrusion is alkali granite to granite in nature. Common textures in these rocks are granular، graphic، myrmekite، granophyric and perthitic. Potasium feldspars (perthitic orthoclase and microcline)، quartz and sodic plagioclases are essential minerals. Biotite as the only mafic mineral and zircon، titanite and Fe-oxide are the accessory minerals of these rocks. Biotite is altered to chlorite، and feldspars to sericite، calcite and clay minerals. Age dating with zircon uranium-lead method indicated that the alkali granite is 55. 7 ± 0. 6 Ma (early Eocene) old. Chemically، the rock suite is characterized by high total alkali، Fe/Mg، Ga/Al، Hf، REE (except for Eu)، SiO2 and Zr and low contents of Ba، CaO، MgO، P2O5 and Sr. These features along with various geochemical discrimination diagrams suggest that the Takht-e baz granitoid is post-collisional A-type (A2-type). This suite may be derived from melting of continental crust in an extensional setting after collision of the Lut and the Afgan continental blocks in the east of Iran.

Hezarabad area is located 5 km at south east of Ashtian, Markazi Province. Structurally, the area is located in the Urmia-Dokhtar magmatic belt of Iran. The basement rocks of the area are pelagic limestone, lithic tuffs, and limestone to sandy limestone, marl, conglomerate, andesite lava and shale. Andesitic and tuff are the main host rock of mineralization. The mineralization mostly is vein types in four trends which follow NE-SW trend of local faults. The mineralization can be seen also as disseminated, breccia to fills fractures and pore-spaces types. The most important ore minerals are galena, cerosite and sphalerite. The galena is associated mostly barite in local faults. The second important mineral is sphalerite which can be seen mostly intunnels. 40 samples were analyzed by Inductive Coupled Plasma Mass Spectrometry (ICP-MS) for Pb, Zn, Ag, As, Cd, Co, Cr, Cu, Mo, Ni. The data processing indicates high anomaly for Zn and Pb and relatively anomaly for Cu, Ag, As, Mo. The average value of Pb is 34525 ppm and average value of Zn is 6108 ppm. The Mo content is reach up to 1182 ppm. According to correlation diagrams, there is a high correlation between Pb and Ag and also Ag and As. It shows that the galena is the main host of these elements.