نشریه علوم زمین
پیاپی 129 (پاییز 1402)

A conformable passage between Sarvak and Surgah Formations in Lurestan sedimentary basin reveals the potential of studying the Turonian–Coniacian boundary within Surgah Formation. Two sections of the Surgah Formation at Posht-e-Jangal and Pasan anticlines situated on the southeast of the Lurestan sedimentary basin have been studied on the basis calcareous nannofossils, and based on the observed distribution of nannoflora, the presence of CC12 to CC16 nannofossil biozones is documented which points to the latest Turonian to Coniacian age for the base of this Formation, while the top boundary is estimated approximately at earliest Santonian. Due to the absence of Micula staurophora, however, separation of CC13 and CC14 biozones is not possible and therefore, the Turonian–Coniacian boundary is placed somewhere within the said undivided interval. The FO of Calculites obscurus as the marker event for the top of CC16 biozone is not identified but on the basis of suspected LO of Lithastrinus septenarius as the marker event of the top of UC11 and onset of UC12, the record of early Santonian beds seems probable.

In order to biostratigraphic studies of Gurpi Formation, a section was selected in the north-east of Noorabad city in Fars. Structurally, this section is located in the folded-thrust zone of Zagros and geographically in the Fars zone (coastal Fars). The Gurpi Formation is extended of 229 meters in thickness, contains limestone, shale, marly limestone and argillaceous limestone. Its lower boundary with Sarvak Formation and its upper contact with Pabdeh Formation are discontinuous. The study conducted on foraminiferal biostratigraphy in this section led to the identification of 20 species belonging to 7 genera of planktonic foraminifera. Based on the stratigraphic distribution of the planktonic foraminifera, five biozones are determined which correspond with global biozonation. Described biozones are comprised of: 1-Globotruncanita elevata Partial range zone; 2-Globotruncana ventricosa Interval zone; 3-Radotruncana calcarata Total range zone; 4-Gansserina gansseri Interval zone; 5-Contusotruncana contusa, Contusotruncana walfischensis, Globotruncanita conica Assemblage zone. Based on these biozones, the age of Gurpi Formation is assigned to early Campanian to late Maastrichtian. The absence of the Marginotruncana and Dicarinella  asymetrica in the lower part of the Gurpi Formation indicates of the Santonian-Campanian boundary and the determination of the early Early Campanian age for the base of this Formation.

To prepare sedimentological data, 98 surface sampling stations have been designed from the seabed in the continental shelf in the southern part of the Caspian Sea and along the coast of Iran. Indicators such as the type and amount of sediment load transported to the sedimentation environment, the energy of waves and sea currents, as well as how the slope of the seabed changes, play a role in the production and diversity of the sedimentary facies. 9 sedimentary facies are the most abundant in the surface deposits of this area and on average, in the sediments of the continental shelf, there are 1% by weight of coarse-grained particles, 25% by weight of medium-grained particles and 74% by weight of fine-grained particles. The composition of sedimentary facies in this area is controlled by indicators such as the size of sedimentary particles, the amount of sedimentary load carried to the environment, the energy of waves and sea currents, and how the slope of the seabed changes. In the marine environment of the study area, sub-sedimentary environments, Backshore, Foreshore, Shoreface, Offshore transition zone and offshore can be identified. The two facies of slightly gravelly Mud and Mud are more abundant than other facies.

In the present study, in order to reconstruct the paleoenvironmental and climatic changes of Jiroft during the last 4000 years, several evidences of sedimentology and biogeochemistry on a sedimentary core have been investigated. Around. 3950 cal yr BP, low values of Ti/Al, Si/Al, C/N and CPI along with high values of δ13COM, and Paq indicate a wet period in Jiroft. evidence indicates a relative decrease in humidity between about 3900 and 3293 cal yr BP. Between 3293 and 2897 cal yr BP, Jiroft was dry and dusty. The results show very dry conditions with a significant increase in the amount of dust around 3200 cal yr BP. A long-wet period from about 2897 to 2302 cal yr BP can be recognized with high Paq values. The highest Ti/Al values along with the lowest δ13COM values indicate increased wind activity and dry conditions between 2100 and 1650 cal yr BP. Jiroft experienced wet conditions between 1540 and 1315 cal yr BP. With the relative decrease of rainfall, a semi-humid climate prevailed in Jiroft between 1315 and 854 cal yr BP.

Recently, due to the trend of decreasing rainfall and increasing groundwater pumping rate, there have been concerns about the risks caused by the decrease in the volume of aquifer reserves and the drop in the groundwater level, and as a consequence the land subsidence. Also, in Ajabshir plain due to a gradual decrease in the water level, it is necessary to estimate the subsidence and investigate the subsidence potential to prevent its harmful risks in the future. For this purpose, using the ALPRIFT framework, which includes seven layers of parameters affecting subsidence, the subsidence potential map was zoned. The subsidence potential index was obtained in low and moderate ranges. In the next step, using Sentinel-1 satellite images, the subsidence during the years 2020-2021 was estimated to be 2.4 cm, which had a significant correlation with the groundwater level of the water year 2020-2021 and subsidence potential. In addition, artificial intelligence optimization methods including fuzzy logic (Sugeno) and genetic algorithm were used in order to fix the defects of applying expert opinions and increase the correlation between subsidence (Insar) and ALPRIFT, among these models, Sugeno's fuzzy method provided the best correlation between the two subsidence maps and ALPRIFT. The correlation between subsidence with ALPRIFT, ALPRIFT-GA and ALPRIFT-SFL was obtained as 0.46, 0.62 and 0.72 respectively.

The Doruneh fault system with more than 700 km length, after the main Zagros fault, is known as the largest fault in Iran. In this research, this fault system is divided into 3 main parts because the mechanisms of its different parts are different. The western part is reported to have a left lateral strike-slip mechanism with a reverse component, the middle part is a left lateral strike-slip mechanism, and the eastern part is reported to have a reverse mechanism. In this study, seismicity parameters and their temporal and spatial changes along this fault system are analyzed using seismic data collected from 1980 to 2023 and based on the maximum likelihood method. In this regard, the temporal changes of b-value shows two significant drops, which indicate two relatively strong Torbat-e Heydarieh earthquakes in 2010 and the Fariman earthquake in 2017. Despite the fact that the scientific community is not yet able to accurately predict earthquakes, according to the studied method and with the continuous monitoring and analysis of various earthquake parameters, especially b-value, it is not far from expected to predict the occurrence of possible earthquakes in the future.

In this research, using deformed chert nodules in the calcareous units of Sarvak Formation in Pyun anticline, quantitative strain values in different parts of this anticline have been investigated. In a perpendicular fold axis survey, the anticline was divided into seven different areas. At least 40 nodules were measured in each area and finite strain analysis was carried out using Rf/Ø and polar methods. The results of strain studies show an increase mode in strain values from the fold limbs (Rs = 1.7) to the fold hinge (Rs = 2.9). Kinematic vorticity analysis shows the range between 0.68<Wk<0.91 and the effect of both simple and pure shear strain components and the occurrence of the strain partitioning in the Pyun anticline. The amounts of kinematic vorticity number indicate the increase of pure shear strain components in the hinge of anticline and the predominance of simple shear strain components in the limbs of the Pyun anticline. According to the results of strain analyses the amounts of bulk shortening was estimated about 47- 50 percent in the Pyun anticline.

This paper presents the results of a field study aiming to describe and to interpret origin of the vein network in the south of Birjand. Adjacent to Birjand ophiolite in eastern Iran, the Paleocene-Eocene flysch facies was deposited in the Birjand foreland area concomitant with the Alpine orogeny (Laramide). The sandstone unit of this facies contain two orthogonal sets of quartzite veins. The N310-340 striking veins (set 1) are arranged parallel to the Bagheran Kuh range front and perpendicular to the vein set 2 (N215-240). The paleostress reconstruction in the Paleocene-Eocene shows that the regional compression direction N240 is perpendicular to the Bagheran Kuh range front. Structurally, to create orthogonal veins, σ1 should be perpendicular to the layering and σ2 and σ3 should be horizontal. This situation was created in the middle Eocene-Oligocene. The post-collision extensions of this period caused a decrease in regional pressure in the region. As a resault, the maximum principal stress (σ1), was changed to a vertical state and intermediate stress (σ2) was parallel to the orogenic pressure. In these conditions, orthogonal tensile openings (state I) were formed as a result of the local inversion of stress and fluid pressure in the flysch facies.

The Muteh–Golpayegan Metamorphic Complex is located within the center of the Sanandaj-Sirjan Metamorphic Zone. The strain parameter measurements by the strain ellipsoid including strain ratio in the XZ principal plane, strain ellipsoid (RXZ), strain ellipsoid shape (K), and strain intensity (D) exhibit prolate  shape for the amphibole mineral for the deformed amphibolitic rocks in the Muteh–Golpayegan Metamorphic Complex. Several kinematic shear sense indicators consist of the asymmetric fold, kink fold, boudin, S/C fabrics, oblique grain shape, and mineral fishes show a dextral shear sense. The quantitative kinematic analyses highlight that Wk varies between 0.6 and 0.93, implying a general shear flow with 42% < simple shear <74% and 26% < pure shear <58%.

Parkam (Sara) and Abdar porphyry Cu deposits containing mainly dioritic and quartz dioritic stocks are located in the southern part of Urumieh-Dokhtar Magmatic Belt (UDMB). In the Parkam deposit, alterations such as potassic, potassic-phyllic, biotitic, phyllic, argillic and propylitic have been identified, while Abdar deposit is characterized by the limited extent of potassic alteration with widespread occurrence of phyllic alteration. The aim of this study is to characterize the phyllic alteration using sericite and sulfide (i.e., pyrite and chalcopyrite) chemistry. In this way representative phyllic alteration samples were analyzed using Electron Microprobe Analysis (EMPA). Results imply for higher concentrations of Zn, Ag, Au, and as in the chalcopyrite samples (averages in wt. %; 0.07, 0.007, 0.012, and 0.043; respectively). Comparably, pyrite samples exhibit higher concentrations of Re, Te, Co, and Mo (averages in wt. %; 0.01, 0.003, 0.09, 0.07; respectively. Among this, gold concentration in the pyrite samples of studied deposits is analogous to those reported previously for Meiduk porphyry Cu-Mo systems wherein gold occurs as inclusions, and/or nanoparticles (probably as Au0 or Au-telluride). In the both deposits, fine-grained micas are K-rich. Additionally, sericite samples exhibit an increasing trend of Si with Fe2+, Mg2+, and Al3+ substitution in the octahedral sites confirming the changes to celedontie - endmember. In accordance with other mineralized porphyry systems (i.e., Copper Cliff and Copper Flat deposits), most of the data follow the trend of ideal tschermak substitution occurring by the increasing of positive charges in the tetrahedral site of white mica owing to the increasing of Si substitution.

The Sarkuh Porphyry Copper deposit is located about 6 km southwest of Sarcheshmeh porphyry copper deposit. Alterations in the region include advanced potassic, propylitic, phyllic and argillic. Copper mineralization is mainly associated with porphyry granodiorite mass. Minerals include chalcopyrite, pyrite, magnetite and some molybdenite. Fluid inclusion studies were performed on quartz from the sulfide viens of the potassic fraction and showed that the main mineralization phase was present with a homogenization temperature between 250 and 527 ° C, salinity between 13.6 and 52.9 wt٪ NaCl, has a high salinity in Sarkuh deposit (Orthomagmatic phase and hypogene mineralization). The homogenization temperature in the late stages of the receding phase (convective phase and the influence of atmospheric waters in the hydrothermal cycle) is around 132 to 165 degrees Celsius and its salinity is 0.005 to 4.74% equivalent to the weight of NaCl. The observed salinity variation can be attributed to the boiling event. The investigation of sulfur isotope composition on pyrite and chalcopyrite minerals in Sarkoh deposit was between +1 and 2.7‰, which indicates the magmatic source of sulfur. The stable oxygen isotope data on quartz veins, show positive range between 7.6 to +9.3‰ with an average of +8.5, indicates a magmatic source for hydrothermal fluids. Also, due to the limited range of sulfur isotopic composition, it can be concluded that the isotopic composition of sulfur has not undergone changes or contamination by other sources of sulfur, or the mixing of magmatic fluid with other sources has been very insignificant. Isotopic thermometry shows the temperature of 315°C and 476°C for the pair of pyrite-chalcopyrite minerals.

The Gano bauxite deposit is located 90 km northeast of Semnan city in the eastern Alborz Mountains, northern Iran. The bauxite ores occur as stratiform discrete lenses with a length of 6 km and thickness of 2–20 m along the contact between carbonates of the Elika Formation and shale, sandstone, siltstone, and coal of the Shemshak Formation. Mineralogical analyses revealed that the bauxite ores consist of diaspore, hematite, kaolinite, chlorite, anatase, illite, zunyite, goethite, quartz, and dolomite minerals. Fluctuations of the groundwater table level, acidic atmospheric waters, and an increase in pH of the weathering solutions close to carbonate bedrocks played an important role in the concentration of Fe-poor ores in the upper parts and Fe-rich ores in the lower parts of the studied profile. An increase in oxidation, the possible presentence of secondary phosphate minerals, fluctuations of the groundwater table level, and the role of carbonate bedrock as an active buffer played an important role in the extent of Ce anomaly in the ores (0.79–12.25). The pH variations of weathering solutions, fluctuations of the groundwater table level, the role of carbonate bedrock as a geochemical barrier, and simultaneous precipitation of Fe-bearing minerals and preferential scavenging of LREE(La–Eu) by hematite played an important role in the distribution and fractionation of rare earth elements in the bauxite ores. According to geochemical considerations (Eu/Eu* vs. TiO2/Al2O3 and Sm/Nd bivariate diagrams), the Gano bauxite deposit probably derived from the weathering of intermediate igneous rocks.

Astmal deposit is located in the northwest of Iran and is structurally located in the Arasbaran Magmatic zone. Skarn mineralization related to the Eocene-Oligocene granodiorite rocks which have been permeated to the Upper Cretaceous rocks. Mineralization has formed in the exoskarn zone, and the metasomatic process has started immediately after the penetration of the granodiorite into the limestone. Significant amounts of Si, Mg, and Fe elements lead to the development of anhydrous calc-silicate minerals with medium to coarse grains, and also significant amounts of Cu, Fe elements along with volatile substances such as CO2, H2S are added to the skarn system. As a result, hydrated calcsilicates (epidote, tremolite, and actinolite), sulfides (pyrite and chalcopyrite), oxides (magnetite and hematite) and carbonates (calcite) have been replaced anhydrous calcsilicates. The results of δ34S isotope analysis on pyrite and chalcopyrite ores are in the range of -1.8 to +6.1 ‰, which indicates the magmatic source of sulfide. Also, the results of δ18O and δD isotope data on magnetite, sericite and epidote minerals, which are in the range of -56 to -73 ‰ for hydrogen and -0.5 to +6.8 ‰ for oxygen, indicate a mixture of magmatic fluids associated to the small amounts of meteoric fluids.

The Hired gold deposit in the Lut block, East Iran, is closely associated with an intermediate-mafic intrusive complex consisting of granodiorite to diorite, hornblende quartz-monzonite, and gabbro-diorite intruded into Eocene volcanic rocks. The intrusions are distinguished by high contents of CaO, FeOt, and MgO, and rather low K2O+Na2O implying they crystallized from weakly differentiated magmas. This subject, and the relatively high Mg# (36.36 to 52.32) imply the involvement of a mantle source in the production of the parent magma. The intrusions are metaluminous, calc-alkaline to high-K calc-alkaline, and distinguished by the occurrence of ilmenite as an accessory mineral. Mineralization occurs in veins and veinlets disseminations in the granodiorite intrusion and the volcanic rocks, closely associated with tourmaline, silicic, and carbonate alterations, and is distinguished by abundant pyrrhotite, arsenopyrite, pyrite, and minor chalcopyrite, galena and sphalerite. Gold occurs mostly as submicroscopic grains in the pyrite and arsenopyrite. The mineralogical and geochemical attributes of the intrusive complex, and the ore mineralogy, allow the Hired to be classified as a gold deposit related to reduced I-type granitoids. The reducing nature of the parent magma can be explained by introduction of reduced crustal materials into the source area, and/or assimilation of carbonaceous metasedimentary rocks.

Chah-Nar Pb-Zn deposit is located south of Rutchun plain, 110 km SW Baft, within Sanandaj- Sirjan Zone. Mineralization occurs at calitic-dolomitic marble of Rutchun complex  as epigenetic with structural control. Paragenetic minerals are galena and minor sphalerite  and pyrite associated with quartz, and minor calcite and dolomite,  as gangue minerals. These minerals show veinlets, open space filling, breccia, and disseminated textures. Galena can be seen in the form of coarse grain crystal and cuboctahedral texture and fine grain crystal. Silicification and carbonatization are the most important alteration zones. Galena chemistry indicates galena is Ag, As, Cd and Zn -rich and Sn, Bi-poor. Sb/Bi ratio in galena is close to 3, which is indicator of low temperature deposits. Host rock type, stratabound and epigenetic mineralization, postsedimentary fault controlling, texture, ore types and gangue minerals, and lack of significant correlation between mineralization and igneous activities, chemistry of galena, indicate that Chah-Nar deposit is similar to MVT deposits, although it has some differences with this deposits type.