GEOSCIENCES
Year:2017 | Volume:27 | Issue:105 |Papers Count:30

The Cretaceous limestone with abundant cracks is located on the Jurassic shales in the studied area. Skarn forming fluids had influx into these cracks from a long distance, whichcreated distal skarns. The presence of a recrystallized and skarnified limestone layer within the shale, separates the studied skarn from the most well-known skarns in Iran and puts it in the category of reaction skarns. There are some lenses of mineral deposits within the skarn which is consisting mostly of magnetite and hematite. Iron-rich solutions which are derived from intrusive rocks, left iron as magnetite in carbonate. In addition to the formation of magnetite by hydrothermal solutions, it can also be created in retrograde stage by andradite alteration. This skarn is consisting mostly of pyroxene, garnet, tremolite-actinolite, chlorite and epidote. Skarnification process occurred in two successive stages: progressive and regressive. In progressive stage, carbonate - anhydrous silicate minerals such as garnet and pyroxene were formed. At the later stages, due to meteoric water influence, garnet altered to epidote, magnetite, calcite and quartz and pyroxene altered to tremolite-actinolite, calcite, quartz and opaque minerals. There are two sets of garnets in the studied skarn, the first one is massive (formed at the progressive stage) and the other one is as veinlet (formed at the regressive stage with epidote and is formed in quartz- calcit veins along with sulfide mineralization). Garnet composition in iron deposit of the studied area lies in grossular - andradite series. The compositions of studied garnet is similar to garnet compositions from Cu-Fe skarns worldwide.

In the east of high Zagros – in Faraghan Anticline- sedimentary cover with more than 10 km thickness has been decoupled from basement above the Hormuz salt and has been deformed. This anticline is cut by High Zagros Fault. A lack of paleostress studies and kinematic interpretation of structures in northeast of the Fars Arcled us to investigate stress field changes and its role in the evolution of the Faraghan Anticline. Inversion method was used for determination of reduced stress tensor parameters and discrimination of faults developed in each brittle tectonic phase. Maximum shortening axis was determined by using stylolites and orientation of the minimum principal stress axis was determined from tension gashes. The present stress field was calculated by inversion of earthquake focal mechanism data. According to our data and the deduced results, before the late Miocene folding and faulting some of veins or tension gashes developed within an stress field with s1 orientated along N27° - 29°E. During the late middle Miocene, sedimentary cover was deformed under a general compressional stress regime with a N27°-29°E direction of s1, leading to the development of detachment and fault-related folds . The basement faults were reactivated during the latest Miocene- early Pliocene in a general strike-slip regime with direction of s1 along N4°E. The High Zagros Fault was reactivated at that time and cut the entire cover section existing structures. In the late Pliocene, direction of σ1 stress axis was temporally modified to N025°W in a strike-slip tectonic regime. Former strike- slip and reverse faults were therefore reactivated in this new stress field. The analysis of earthquake focal mechanism data indicates that direction of present s1 stress axis is N-S.

The Asmari Formation was measured and sampled at Ghar-e Agha Seyyed in Farsan area in order to determine sedimentary environment based on facies analysis. In the study area, the Asmari Formation has a thickness of 183 m and conformably overlain the Pabdeh Formation. Based on microfacies studies, eight microfacies were recognized including: 1) Porcelanouse foraminifera – bioclastic – red algal wackestone / packstone, 2) Rotalia grainstone, 3) Bioclastic –red algal grainstone, 4) Red algal – coral boundstone, 5) Red algal wackestone (Floatstone), 6) Red algal –large hyaline foraminifera – intraclast packstone, 7) Red algal – bioclastic - large hyaline foraminifera wackestone / packstone, 8) Large hyaline foraminifera packstone. These microfacies represent three facies belts including Inner ramp, Middle ramp and Outer ramp. Based on the presence of benthic foraminifera, age of Oligocene (Rupelian – Chatian) is determined for the Asmari Fm. at this section.

Significant damages have been caused by dust storm in Iran, particularly in Khuzestan province. Thus, as a primary step to fight with dust storms, it is necessary to map dust sources. The purpose of this study is to identify dust sources using a combination approach of remote sensing, GIS and sedimentology in Khuzestan province. For this, spatial data of soil, land use, climate, slope (collected from related organizations) and sedimentology were used as constraint layers, and vegetation, land surface temperature (LST) and soil moisture constitute the main layers. Sedimentology map was prepared by field sampling (900 samples) and remote sensing techniques. Also the main layers were extracted by performing the necessary computational processes on Landsat 8 satellite images. The constraint layers were applied to remove the areas without any potential of dust source. In next step, main layers weighting was done using pairwise comparison and Fuzzy Analytic Hierarchy Process (FAHP) methods. For preparing map of dust sources, each major layer was multiplied by corresponding weight and were then integrated to present a dust source zonation map. To validate the results, a field work was carried out in 180 points of source areas that verifies high accuracy of the prepared map. Results showed that 9 percent of Khuzestan plain, equivalent to 349254 hectares, are dust-generating sources. Based on land use type and area, the identified zones include destroyed range, rainfed agriculture lands, bare lands, wetlands, dried ponds and irrigated agriculture lands, respectively.

Sungun and Haftcheshme mines are located in the Arasbaran volcano-plutonic complex at the North West of Azarbaijan province. Lamprophyric dikes of Sungun with ages younger than Oligo-Miocene contain biotite, plagioclase and pyroxene with porphyritic texture and are classified as calc-alkaline and kersantite. They are intruded into the Sungun quartz - monzonite. Lamprophyric dikes of Haftcheshme with ages younger than Oligo-Miocene include minerals such asbiotite, alkali feldspar and pyroxene. The main textures are microlithic porphyry and flow texture. These calc-alkaline lamprophyres are classified as minette, intruding the Haftcheshme quartz - diorite. The behavior of trace elements studied by the means of spider diagrams show low enrichment of LREE relative to MREE and HREE. Investigations on geochemical characteristics of the studied lamprophyres show that the lamprophyric rocks are of calc-alkaline type, formed in a magmatic arc tectonic setting. These lamprophyres are generated from low degree partial melting of a garnet lherzolite source.

Seismic source zones have an important role in hazard assessment in probabilistic seismic hazard analysis. These zones are often determined according to judgments by the experts and in most cases, seismic source delineations by several experts across a specific region typically leads to non-uniform and controversial results. Thus, most of the uncertainty in probabilistic seismic hazard analysis can be related to the delineation of seismic sources. Another problem of probabilistic seismic hazard analysis is the way earthquakes are visually taken by experts to relate with the seismic sources. Even though it is well known that earthquakes happen on faults, the causative fault of a given earthquake is not precisely constrained, so that makes unconstrained the realization and assessment of seismic risks by experts. This paper attempts to determine seismic sources and associate events to faults using a fuzzy particle swarm optimization clustering algorithm. The algorithm works based on the minimization of two objective functions: distance of events from fault, and distance of events from their center of density (i.e. cluster center). The algorithm is applied by two approaches to the seismic data acquired from northwest of Iran; the distance was Euclidean in the first approach and Mahalanobis in the second one. In order to test reliability of the algorithm, its performance was evaluated based on the events assigned to the faults by previous researchers. Comparing associated earthquakes to faults by the algorithm in northwest of Iran with known and documented earthquakes revealed that 79.2% of the events are correctly induced by faults considering the Euclidean distance approach. In the case of using Mahalanobis distance, 87.5% of the events were properly reproduced, implying its higher efficiency. Final results show that this methodology will help seismological engineers take a step forward in hazard analysis by determining seismic sources and assigning earthquakes to different active faults.

The Kupal oil anticline is one of the most important structures in Dezful embayment that is located in northeast of the Ahvaz city and north of the Marun oil field. Recent deposits and Lahbari member of the Aghajari fonnation have formed the surface outcrops, and the Asmari formation with 7 reservoir layers is the main reservoir rock in this oil field. In this research fractures of the Asmari formation in this anticline have been analyzed based on well data, subsurface maps and seismic profiles. The Kupal oil anticline is a fault-related (detachment fold) and asymmetric fold, in which the middle parts have been distinguished as potential zones of dense fractures development due to longitudinal curvature. The southwest limb in much parts and northeast limb in middle parts indicate zones with high fracture density, and the axial bending of the Kupal anticline is a result of movement of deep faults.

In this paper a part of the Shahr-e-Babak area in NW-Kerman is studied, which is geologically located in Central Iran and Urumiyeh- Dokhtar Belt. The basin was strongly affected by compression in Miocene times, in which deformation is characterized by development of NW-SE trending fold and thrust belt. In this paper, we aim atdeciphering polyphase deformation and paleostress history of part of the Central Iran in the Shahr-e-Babak area, and that how various geological aspects may be related to a stress field that has been reoriented through time. Also, we indicate how the brittle deformation studies and paleostress analyses may contribute in the interpretations of the post-collisional tectonic evolution of this area. In this paper, by using systematic brittle tectonic analyses, including stress tensor inversion form fault-slip data, we decipher the succession of deformational events that resulted in present-day structures. Therefore, a statistical view of the brittle tectonic reconstructions taken as a whole leads one to better understand the relationships between the different stress fields and folding events that governed the history of compression in this area .The systematic reconstruction of brittle tectonic regimes led us to characterize an anticlockwise change in the main direction of compression through time. Thus, it can be seen that the late Cretaceous to late Miocene pre-folding NOS5° and N084° compression was followed by syn-folding N040° compression in the Miocene. The Miocene compression then continued into the Pliocene post-folding N029° direction, and changed afterward to the Pleistocene-Recent post-folding N003° direction. Although this general anticlockwise rotation of compression has probably been progressive through time, our data suggest three distinct stress regimes that (1) predate, (2) are contemporaneous with, and (3) post-date the more consistent compressional stress regime of the folding and thrusting process. According to this reconstruction, it is confirmed that many local right-lateral st: rike--slip faults were reactivated from NW-SE reverse faults in the Sahahr-e-Babak area of SW Central Iran. These results could properly support the hypothesis of a significant anticlockwise change in the movement direction of the Arabian plate with respect to the Eurasian plate and block rotation in Central Iran.

Pabdeh Formation comprised carbonate-siliciclastic succession of Zagros fold-thrust belt in south west of Iran. The studied area is located in Lar Mountains (North East of Khami anticline) which extend in a northwest-southeast direction Parallel to the Zagros sedimentary basin trend. Microfacies analysis especially in phosphate-bearing horizons and semiquantitative investigations of foraminiferal contents as an aid to determining the depositional environment of marine deposits was the aim of this study. For this purpose, 300 samples were collected from the 410-m thick pabdeh Fm. at the Lar anticlilne north east of Gachsaran. From these 126 were selected based on lithology and facies alternations and thin sections were prepared. Petrographical studies and microfacies analysis of the Pabdeh Formation demonstrate that eight lithofacies can be recognized in this interval. Planktonic foraminiferal mudstone and presence of turbidite microfacies suggest deposition in a ramp setting. On the other words the depositional environment of the Pabdeh Formation evolved into an outer ramp setting. Microfacies of the upper part of the Pabdeh Formation reveal deposition in a shallowing-upward depositional environment. With attention to the items mentioned above the Pabdeh Formation is dominated by a pelagic microfauna that deposited in a deep ramp setting (Outer ramp) that passed into a shallower ramp in the middle parts.

The Takht-e-Soleyman metamorphic complex is located at NE of Takab town, West Azerbaijan province. This complex having Precambrian-Cambrian age has been formed from low to high grade metamorphic rock types. The retrograde granulites are subject of this study. The retrograde metamorphic assemblages of the granulites are including Amp+Grt+Spl+Opaque phases. Amphibole highly overprinted primary mafic phases of clinopyroxene and orthopyroxene. Spinel at the klyphitic texture around garnet porphyroblast forms the main feature for retrograde metamorphism of granulites. Rutile occurs as inclusions within amphibole. The compositional profile of garnet indicates chemical variations from the core to the rim. Compositional variations from the core to the middle part is characterized by a minor increase in XMg but decrease in XCa and XMn. This feature of garnet is indicative of decompression with small increase of temperature. Due to complete overprinting of high temperature phases by the retrograde phases as well as lack of preserved pick metamorphic minerals, it is indeterminate to estimate pick metamorphic P-T conditions for M1 stage. On the basis of chemical compositions of porphyroblasts, retrograde evolution of the investigated granulites is considered at two stages: (1) pressure decompression and exhumation (M2-a) and (2) cooling (M2-b). The retrograde P-T conditions are obtained as T=810±10˚C at P=10.5±0.7kbar for the first and the second retrograde stages, respectively. Relatively coarse-grained phases at the klyphitic margin are indicative of low cooling rate during uplifting of rocks from lower to upper levels. Extensive overprinting of high temperature phases by amphiboles supports this idea. Time of pick and retrograde metamorphism for the investigated granulites are not clear accurately. It seems reasonable to attribute pick metamorphic and granulite formation time to Oligocene-Miocene, related to crustal thickening due to collision between the Central Iran micro-continent and the Arabia plate. The granulites are metamorphosed under retrograde conditions in relation to thrusting and post collisional extensions which caused uplifting, crustal thinning and exhumation of the rocks. However correct conclusions on tectonometamorphic evolution need more precise studies.

The Sarvak Formation is one of the most important carbonate reservoirs of Iran. The main objective of this study is to evaluate reservoir quality of the formation by integration of petrographic studies and core porosity-permeability data in three key wells in a giant oilfield of the Abadan Plain, SW Iran. Petrographic studies led to the identification of 13 microfacies that are grouped into three main facies belts including lagoon, shoal, and open marine (talus and slope) which deposited in an isolated carbonate platform. The main diagenetic processes affecting the Sarvak Formation are micritization, bioturbation, recrystallization, dissolution, cementation, physical and chemical compaction, dolomitization and silicification, along with fracturing. According to the results, the reservoir quality of the Sarvak reservoir is a function of both primary depositional facies and secondary diagenetic processes. Evaluation of impacts of depositional facies on reservoir quality indicated that the rudist-bearing intervals (especially rudist debris zones) have high reservoir quality. Dissolution and cementation are the most pervasive diagenetic processes affecting the formation, and occurred due to widespread meteoric diagenesis. Dissolution and fracturing are the chief factors that lead to the improvement of porosity-permeability, whilst calcite cementation and compaction have destructed reservoir quality of the studied interval. This study may assist better understand and the geological parameters controlling reservoir quality of Sarvak Formation in the Abadan Plain oilfields.

Engineering geological characteristics of Gachsaran Formation in Dam Khersan 3 reservoir site was investigated in order to evaluate the solubility of gypsum and leakage problems and select a suitable method for sealing the Gachsaran formation as part of the reservoir. The under construction Khersan 3 dam is a concrete arch dam with a height of 195 meters over the Khersan river 40 km south of Lordegan city. Geological formations in the reservoir site includes (1) the Asmari limestone, (2) marl, gypsum and marly gypsum of the Gachsaran Formation, (3) marls and shales of the Pabdeh and Gurpi formations and (4) river alluviums. In some of the samples, XRF and XRD studies were carried out, and seepage and dissolution properties of the samples were also determined. In addition, leakage of water from the reservoir was evaluated using numerical analysis. Results indicate the presence of large amounts of marl, Lugeon less than 3 and high RQD of the Gachsaran Formations. Therefore, it is suggested not to construct cut-off wall or grout curtains.

The Bahr Aseman volcanic-plutonic complex is located to the southeast of the Kerman magmatic belt. Unlike Kerman magmatic belt which formed and evolved during Cenozoic in a dominantly continental arc and post-collision tectonic setting, Bahr Aseman complex formed during Late Cretaceous in an oceanic island-arc setting. The complex is composed of andesitic and andesitic-basaltic lava flows and subordinate pyroclastic materials and carbonate interlayers, as well as abyssal tonalite to quartz-diorite and quartz- monzodiorite intrusive bodies and shallow dioritic intrusions. Vein- type copper deposits, iron skarn and copper skarn are the main ore deposit types in Bahr Aseman. Chalcopyrite is the main ore mineral in vein-type and skarn-type copper deposits; the mineral is converted to oxide copper ores at surface and shallow depths. Magnetite is the main commodity in skarn type iron deposit. Highly altered porphyritic bodies associated with copper oxide ore were identified that are comparable, in some aspects, with porphyry type copper deposits; subsurface data, however, is required for conclusive remarks. The various types of deposits are distinguished by distinct fluid inclusion characteristics. In the vein type copper deposits, fluids in association with mineralization represent dominant homogenization temperature (Th) of 150-220ºC and salinity of 5-10 and 25-30 wt% NaCl. Fluids in the skarn type copper deposits represent 170-250ºC and ranges of 5-15 and 27-35 wt% NaCl as dominant Th and salinity, respectively. The d34S values in the vein-type copper deposits vary between +3.9 and +5‰, suggesting a magmatic origin for sulfur and probably metals (directly derived from magma or leached from magmatic rocks). Sulfur isotope ratios for two samples from Moka are +4.3 and +7.1‰, slightly different from typical magmatic d34S ranges. Oxygen and hydrogen isotope ratios for the vein-type copper deposits, measured on quartz and fluids extracted from inclusions in the mineral, are -6.6 to +1.9‰ and -79.4 to -51.8‰, respectively. This values suggest mixing of magmatic and meteoric fluids and/or fluid-rock interactions at different ratios. It appears that larger deposits have more shares of fluids with magmatic origin. With regards to the island-arc tectonic setting, recognized deposit types and ore minerals paragenesis, finding new copper and iron and probably gold deposits are possible in the Bahr Aseman area.

One of the essential studies in exploration, exploitation and development of hydrocarbon fields is to evaluate the fault and fracture systems and the role that they can play in reservoir quality and geometry. If the hydrocarbon reservoir is a fractured carbonate reservoir, assessing the mentioned properties is of great importance. Assessment of the structures should be done simultaneously because of their close relations, and the their probable genesis connection should be revealed. In this research, subsurface data including 2D seismic profiles, underground contour maps and F: MI log and eventually analogue modeling have been used for evaluation of probable scenarios explaining formation of faults and fractures. The studied area is located at the front of Zagros deformation belt and the Zagros stresses have apparently not affected it. TWo sets of filults of different geometry and role have been detected; the first reverse set (N-S trending) was apparently controller of the reservoir geometry in the structure; the second normal set (NW-SE trending) are most likely causative of the main fractures in the field. It is likely that positive inversion tectonic of the basin led to the development of this field in form of a pop-up structure. Based on the interpretations, the internal normal filults have been formed probably by the rise ofHormuz salt or by local stretching due to left-lateral component of the boundary reverse faults. Using interpretation of drilling-induced fractures and break-outs derived from F: MI, trends of the Shmax and Shmin are determined. Also it was revealed that the natural fractures and the main set 2 of filults are sub-parallel with the fractures induced by drilling. Therefore, the compatibility between trends of the natural fractures, breakouts and local normal faults can suggest a tectonic origin for the natural fractures.

Shotor-Kuh metamorphic - igneous complex is located at 80 km SE of Shahrood and at the northern edge of the central Iran structural zone. This complex includes a wide lithological composition range such as metapelite (micaschists and gneisses), metapsammites, metabasites (amphibolite and garnet amphibolite), metacarbonate (limestone and dolomitic marbles) and metarhyolites. Protolith of metabasites was basaltic lavas, diabasic swarm dikes and small scale gabbro-dioritic intrusions. With respect to abundance and importance of metamorphosed basaltic intercalations and diabasic dikes swarm in comparison to the other basic rocks, this article specially advocated to investigate their evolution. Based on the field evidence and petrography, increasing the degree of metamorphism of metabasites resulted in producing of amphibole schist, amphibolite, garnet amphibolite and eventually amphibolitic migmatites. Thermobarometery based on the chemical analysis of garnet, amphibole and plagioclase of the metabasites indicates the temperarure range of 602-711 °C and pressure of 9-11 Kbar for their formation and final equilibrium, which corresponds to P-T conditions of amphibolite and upper amphibolites facies. From the geochemical points of view, the magmas forming these metabasites had tholeitic to calc-alkaline nature. These magmas originated from the subcontinental lithospheric mantel source. Submarine basaltic lava flows and diabasic dikes swarm originated during extensional tectonic regimes which affected Late Neoproterozoic Iranian Gondwanan terrains. These extensional tectonic regimes are associated with producing of intracontinental sea to oceanic basins (rift or back arc). These basins closed in a short time and lead to generation of tectonic melange or accretionary prisms on the continental crust. Based on the U- Pb age dating on Zircons separated from these metasbasites, metamorphism event occurred in the interval time of 526-577 Ma (corresponding to the late Neoproterozoic and Cadomian orogeny in the Iranian Gondwanan terrains).

Nowadays ground water is the main source of drinking, agriculture and other uses in arid and semi-arid areas. The demand for this critical and strategic natural resource has increased with population growth and society developments. This process decreases water resources and damages aquifers environment. Therefore, we need to manage aquifers and understand the hydrogeological parameters to deal with water crisis and prevent distraction of the aquifers. Hydraulic conductivity is one of the most important parameters for aquifer management. The ground water system is complex and estimation of hydrogeological parameters is associated with inherent uncertainty and also is costly and time consuming that is usually done with classical methods such as laboratory tests, slug test, tracing test and pumping tests. Therefore recently estimation of hydroulic conductivity by artificial intelligence methods has reduced the uncertainty of this parameter and add up some accuracy, so that it can overcome the shortcoming of classical methods. In this study, four artificial intelligence methods including Mamdani fuzzy logic (MFL) system, Sugeno fuzzy logic (SFL) system, Wavelet-neural network method and Least square support vector machine (LS-SVM) method were used as individual models to estimate the hydraulic conductivity using surface geophysical data in Maragheh-Bonab aquifer. Given that each of these models based on their inherent properties presented good results in some parts of area, therefore, for parallel use of the four models the nonlinear combination method as a supervised committee machine artificial intelligence (SCMAI) model was used to estimate the hydraulic conductivity in the Maragheh-Bonab aquifer. The result of this model showed that this new combinational model has higher performance than other single models presented by using different evaluation criteria. The SCMAI model was tested against 15 data. The RMSE and R2 for SCMAI prediction were computed as 0.045 and 0.97, respectively. A comparison between the values estimated by this model with those by individual mentioned models indicated that SCMAI model performs better than individual AI models supported by lower RMSE and higher R2. This result implies that SCMAI model shows high performance for estimatiing the hydraulic conductivity values in the heterogeneous unconfined aquifer in the Maragheh-Boanb plain.

The occurrence of historical and instrumental earthquakes near the North Tabriz Fault in NW Iran is an evidence for seismic activity of this fault, which recorded historical earthquakes with magnitudes greater than 7.Inthis study, existing experimental relations, historical seismicity, and the fault geometry were used to define a Mw 7.7 earthquake scenario. The stochastic finite fault modeling based on a dynamic comer frequency shows a good agreement between maximum estimated acceleration and common attenuation patterns. The derived shake map illustrates that the stongest ground motion is observed in the NW, Nand NE of the tabriz city along a zone parallel to the fault. In addition, the maximum acceleration derived from simulation is almost equal to that computed from attenuation patterns.

Collected geochemical data from stream sediments, can be used in regional exploration and identifying anomalies in reconnaissance stages. In this research in order to carry out regional exploration studies, multifractal modeling approaches including concentration-area and concentration number are used and geochemical anomalies for index elements (As, Sb, Au and Cu) are examined. 855 of stream sediment samples were collected in the Alut 1:100,000 sheet area and were analyzed by ICP-MS method in the laboratory of Geological Survey of Iran (GSI). Then, statistical parameters and histograms were performed on the elements. Then, using fractal methods concentration-area and concentration number, related anomalies in this sheet are calculated and anomaly maps were drawn. Respect to the geological setting, existing structures and predominant lithology, the results of two methods (concentration - area and concentration – number) were compared in the area. The results of the two methods showed that concentration of these elements has increased in central and southeast parts of the region and formed promising prospects. Although concentration-number method, due to more extensive geochemical halos, included well-known deposits (Barika mine) and also accommodated expected mineralization in the Sanandaj - Sirjan zone.

One of the factors reducing the chemical quality of groundwater used in the industry is a gradual increase of ions concentration. These ions can affect the mineral processing and reduce mining efficiency by corrosion or sedimentation in the path of water circulation. In Gol Gohar Iron ore mine, the rate of salinity in groundwater has increased significantly in recent years. Because brine groundwater in the mine is used to produce pulp in concentrators, its quality has beena matter of concern. In this study, different factors affecting the groundwater quality and causing salinity increase are studied These factors include quality of groundwater inflow, surface water infiltration, lithology of the region, depth of mining, saturated thickness of the aquifer, changes of hydraulic gradient, ground water circulation path, water budget, isotopic properties of water and groundwater evaporation.

The Nodoushan intrusive complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh-Dokhtar Magmatic Belt (UDMB). This complex consists of four main intrusives, including diorite, granite-granodiorite, diorite porphyry and granodiorite. Mafic microgranular enclaves (MMEs) are abundant in the diorite porphyry and granodioritic intrusives and also in some parts of Granitegranodiorite intrusives, which consist of diorite, monzodiorite and rarely gabbro -diorite. According to geochemical data, the Nodoushan intrusive complex is metalominous to moderately peraluminous, I-type and shows medium to high potassium calc-alkaline affinity. Geochemical investigations show that contamination and mafic-felsic magma mixing played significant role in the evolution and petrogenesis of the mentioned intrusions magmas and formation of MMEs. Using U-Pb zircon dating method, the obtained magma crystallization ages are about 30 Ma for the dioritic and granite-granodiorite intrusives, 24 Ma for the diorite porphyry and 25 Ma for the granodioritic intrusives. In addition, the age for part of the granite-granodiorite unit that is located in the northeast corner of the region, at the north of the Nain-Dehshir fault (NDF) and the western part of the Central Iranian Microcontinent (CIM), was determined 40 Ma. The geochemical evidences suggest that the studied intrusions magmas were derived from partial melting of continental crust caused by the mantle melts in an active continental margin. It seems that the melting of rocks with combination of metabasalt and metagraywacke in the lower crust in balance with the residual consisting of clinopyroxene, amphibole and to a lesser extent plagioclase; have the greatest harmony with geochemical characteristics of the studied intrusions.

The Origin of Iron Oxide-Apatite deposits (IOA) with low Ti or Kiruna type deposits has long been a matter of debate. In this case, several origins have been proposed for these deposits which include: magmatic, magmatic-hydrothermal, hydrothermal, banded iron formations, and sedimentaryexhalative. Bafq-Saghand metallogenic zone is located in central Iran and hosts several large IOA type deposits including Chadormalu, Choghart, Se-Chahun, and Esfordi with nearly ~1500 mt ore with an average grade of 55%. Mineralization of REE-rich apatite is very common in these deposits, an issue that could be utilized for the study of their genesis. Fifteen apatite samples from the deposits of Chadormalu, Choghart, Se-Chahun, and Esfordi were taken and analyzed using LA ICP-MS. According to the geochemical analysis, the apatite of the above mentioned deposits show high enrichment of Y, Na, and Si, while very low content of Cl. Total REE content varies from 0.36-2.25% in which the LREE show an enrichment indicating strongly fractionation from HREE. Strong negative Eu anomaly (0.69-0.256) is observed. Sr and Y contents in apatites are 165-365 and 743-1410 ppm, respectively. The Fe-OH-Cl diagram shows that apatites are platted in the Hydroxil-fluoroapatite domain. The results show that these deposits are similar to those of IOA type deposits (e.g. Kiruna, El Laco, Abagong, Avnik, etc.). Apatite mineralization is unlikely related to carbonatitic magmatism, but plotted in the Kiruna type and mafic rocks domain. The main mineralization event was likely related to tonalitetrondhjemite- granodiorite (TTG) and diorite-granite of arc magmatism (525-532 Ma) which were intruded into the Cambrian volcano sedimentary units, as country rock. Then the hydrothermal processes following alkaline intrusion (syenite and monzosyenite) led to mineralization. In general, the iron oxide-apatite (IOA) mineralization with low Ti occurred through the magmatic-hydrothermal processes in the Bafgh-Saghand zone.

The Gurpi Formation was studied from different aspects at two sections, Farhadabad and Kavar, in southwest and southeast of flam where it is composed of 205m and 158m of grey to blue marl and shale beds and occasionally thin beds of argillaceous limestones with two formal members of Seymareh (Lopha) and Emam-Hassan. In order to reconstruct paleoclimate during depositional course of the formation, paleontological and palynological data (ratio of specialist to generalist foraminifera (e.s/e.g) and warm-temperate waters dinocysts and spore and pollen grains) were used statistically. The results show that the Gurpi Formation is mainly deposited in a warm-humid climate with two sharp decreases happening in temperature in early Maastrichtian and Danian.

Gole-Gohar, Ruchun and Khabr metamorphic complexes (South-west of Baft, Kermanprovince), form apart of the Sanandaj-Sirjan metamorphic zone and contain an alternation of metamorphosed impure limestone, sedimentary rocks and basic igneous rocks. Different studies show that the first metamorphic event has been associated with the first deformational phase and orientation of muscovite, garnet, quartz and feldspar in these rocks. At this stage, a foliation parallel to the primary bedding (SO) formed. The second metamorphic event which has accompanied with the second deformational phase, caused the formation of microfolds and preferred orientation of muscovite, biotite, garnet and amphibole in the second foliation (S2), but the third event has been acted as retrograde metamorphism that are corresponding to early Cimmerian orogenic phase. Geochemical characteristics of metamorphosed sedimentary rocks in the area suggest a shale origin for them. Correlations between units and lithological variations in stratigraphic columns from north-west to the south-east, indicate that in Gole-Gohar complex (western part of the area), metamorphosed detrital sedimentary rocks are frequent. This means that the primary sediments have been settled in a turbulent shallow environment and the basic magmas have been entered into the basin simultaneously. With the passing of time, toward the east and at the time of the formation of Ruchun complex protolith rocks, sedimentary basin has been deepened more and occasionally, limestone layers were formed between detritic sediments and igneous rocks. Then the basin became very deep and large volume of limestone precipitated during formation of Khabr protolith rocks. At this time, igneous activity had been ceased. Stratigraphic relationships in the studied complex suggest that Gole Gohar complex rocks formed first and placed at deeper levels at the time of the formation of their parental rocks. Therefore, the highest grade of metamorphism occurred at the western part of the area (Gole Gohar complex) and the lowest grade is observed at the eastern part (Khabr complex).

Arabshah gold deposit formed through hydrothermal activity with an age of -11 Ma (based on zircon U-Pb dating by LA-ICP-MS), in northwestern Iran. This hydrothermal activity is a part of the Urumieh-Dokhtar magmatic arc (UDMA), leading to mineralization in this area, similar to Zarshouran, Aghdarreh and Sarigunay gold deposits. Host rocks are a series of lower Paleozoic sedimentary sequences, cut by calc-alkaline to alkaline (high potassium) dacitic domes. Gold mineralization is mainly observed as vein-veinlets, open space filling, disseminated and brecciation in the deposit. The mineralization in terms of hydrothermal alteration (decalcification, minor argillic, sulfidization, dolomitization and silicification) and mineralization development process is associated with brecciation and deposition of base metal sulfides, iron, arsenic and antimony, similar to deposits associated with geothermal systems (low sulfidation epithermal) in volcanic arcs, but the host rock here is sedimentary. Sulfide minerals in the ore include pyrite, arsenopyrite, orpiment and realgar, stibnite, galena, sphalerite and minor amounts of chalcopyrite. Gold mineralization occurred in the form of released grains of oxidized pyrite, the tiny (invisible) in the sulfide phases such as arsenian pyrite for solid solution. The Arabshah deposit shows characteristic alteration assemblages and ore minerals (As, Sb, Hg, base metals) of epithermal low sulfidation deposits. It has been formed in relation to the mid-upper Miocene, high-level magmatic-hydrothermal activity within an extensional regime at the last stages of the UDMA activity in northwestern Iran.

The Intrusive bodies of the Karaj-Taleghan Axis, situated in the Central Alborz zone have lithological compositions including gabbro, monzogabbro, monzodiorite, monzonite and felsic dikes of alkali feldspar syenite to syenite. Furthermore, they are accompanied by pyroclastic rocks of the Karaj formation, for which Oligocene age is considered. Geological smveys, mineralogical and geochemical studies indicated that the parental magma of this complex had shoshonitic and meta-aluminous nature. Petrological evidence show that fractional crystallization from gabbro to monzonite had main role in genesis of these rocks. Enrichment in LILE) Ba, Rb and Th (and depletion in HFSE (Nb and Ti) in Rare Earth Elements distribution patterns of spider diagrams, indicate an subduction-related environment for formation of these rocks. Also they are enriched in LREE rather than HREE, the characteristics which are usually observed in the rocks from subduction environments and active continental margins. Chemical and petrological studies indicate a common source for these igneous rocks and the main role of fractional crystallization in the evolution of magma, although, minor amounts of assimilation and contamination of magma by crustal rocks occurred. The alkaline magma formed by low degree partial melting of an enriched sub-continental lithospheric garnet-lherzolite mantle. Contribution of both the lithospheric and asthenospheric mantles in petrogenesis of the Karaj-Taleghan basic rocks might be attributed to a tensional geodynamic setting with change in subduction dip in the form of roll back. dominated at the final stage of the subduction of Neotethyan plate beneath Iran in upper Oligocene (Chattian).

The Mahour Zn-Cu-(Pb-Bi-Ag) deposit located in central Lut Block, formed in an intensely crushed fault zone, dominantly in dacite­ rhyodacite volcanic-subvolcanic unit of Late Eocene- Oligocene age. Mineralization occurred as veins, veinlets and breccia massive sulfide and/or as quartz, quartz-carbonate or quartz-muscovite (sericite)- carbonate vein-veinlets. Apart from negligible dark sphalerite, only fine-grained pyrite is observed as disseminated phase within the host rocks. Hypogene mineralization is complex and the main minerals, in order of abundance, are pyrite, Fe-bearing sphalerite and chalcopyrite, with subordinate galena, Cu-sulfosalts, Bi-sulfosalts, Fe-poor sphalerite, and afi:w greenokite, arsenopyrite, digenite and probably covellite. The Considerable amounts of Ag exist in lattice of some sulfosalt and sulfide minerals, as well as locally negligible Au-bearing W minerals. Mineralization is dominantly associated with sericitic, intermediate argillic and propyllitic alterations and rarely with advanced argillic and quartz- adularia that formed at three main stages including: 1- quartz­ pyrite, 2- Fe- bearing sphalerite, and 3- chalcopyrite stage with sulfosalts and minor high sulfidation minerals. Mineralization occurred after silicification and disseminated pyritization that comprise tourmaline (sericitic alteration prior to mineralization) and then weathering process affected it According to very low dissolution of Cu in Cu-Zn-S equilibrium system, high density of chalcopyrite inclusions in Fe-bearing dark sphalerites in Mahour reveals replacement origin of chalcopyrite disease texture. This texture and mineralogy (ore and alteration) indicate formation of Mahour polymetal mineralization at temperature range of 200-400°C and from an intermediate sulfidation state and low acidity fluid which was neutralized to alkaline by interaction with wall rock. Although, a minor evidence for evolution to high sulfidation state, more acidic and oxidation conditions is recorded in Cu- rich zone. Mineralogical features of the Mahour deposit indicate predominantly magmatic origin for mineralizing hydrothermal fluid, and in combination with mineralization structure, association with calc-alkaline to shoshonitic igneous rocks and tectonic setting of host rocks, are very similar to cordilleran style polymetallode deposits.