نشریه زمین شناسی کاربردی پیشرفته
سال دهم شماره 36 (تابستان 1399)

The Geomorphic indices including mountain front sinuosity (Smf), valley floor width to valley height ratio (Vf), basin shape index (Bs), and stream length–gradient index (SL) have been calculated for determination of various tectonic activities along the Aghajari fault. The mountain front sinuosity (Smf) index was calculated about 1.007 to 1.58 respectively in the active and inactive parts of the Aghajari fault. The basin shape (Bs) index has been calculated between 7.83 for the very active parts and, 1.18 for the low active parts of the fault. The amounts of valley floor width to valley height ratio (Vf) index show the range between 0.21 to 5.29 in the active parts with V shape valley morphology and inactive parts with U shape valley morphology respectively. The stream length–gradient (SL) index was calculated between 1414.58 in the high active tectonic and 385.14 in the low active tectonic parts of the study area. With application of the GIS techniques and the overlaying the Smf, Bs, Vf and SL data layers the area was divided into three different tectonic zones and quantitative active tectonic zoning map was prepared for the study area. In this active tectonic map, classes 1 to 3 respectively show the highest to lowest tectonic activity along the Aghajari fault. Results reveal that the Aghajari fault in the central and southeastern parts except for some small areas shows the medium tectonic activity and in the northwestern parts shows the low tectonic activity manner.

The Ruteh Formation with a thickness of 642 m, mainly consisting limestone, dolomitic limestone and shale, disconformably lied on Sandstone and underlied disconformably by Nessen Formation. Based on petrographic studies of 200 thin-sections and sedimentary structures of the Ruteh Formation Identified and separated 18 carbonate microfacies and one clastic facies that deposited 4 facies belt of tidal flat, lagoon, shoal and open marine. The sedimentary environment of middle and late Permian deposits in the Alborz area is very similar to the recent carbonate environments in the Persian Gulf. The sediments are formed in shallow environments in the epicontinental platforms. The sedimentary environment of the Ruteh Formation is identified as a homoclinal ramp. Sequence stratigraphy studies have been carried out based on the accurate determination of sedimentary environments and field studies. From sequence stratigraphy point of view, a third-order sequence of the late morghabin age, three third-order sequences to the early, middle and late midian age and two third-order sequences to early and late Julfian age is determined

The occurrence of barren anticlines in the vicinity of major hydrocarbon fields producing from individual ‎reservoirs in the south of the Dezful Embayment unveils the structural complexity of the area and the ‎intricacy of the processes of hydrocarbon generation, migration and entrapment. In this study, we ‎investigate the possible genetic relationships between the Jurassic-Lower Cretaceous reservoirs on one ‎hand, and the Upper Cretaceous-Tertiary reservoirs on the other. A comprehensive geochemical approach ‎is undertaken to identify genetic oil families in the study area and throw some light on the existing ‎petroleum systems. Bulk geochemical properties and molecular fingerprints support the existence of two ‎distinct oil families within the Khami Group (Jurassic-Lower Cretaceous) and the Asmari-Sarvak (Upper ‎Cretaceous-Tertiary) reservoirs. Source and maturity related biomarker parameters well suggest differing ‎source rocks for these oil families. Oils in the Asmari-Sarvak family indicate a uniform thermal maturity ‎equivalent to the middle oil window. These oils have originated from a marly-carbonate source rock with ‎mixed marine-terrigenous organic matter input that was deposited under anoxic to semi-anoxic ‎conditions. The oils in the Khami Group family are derived from an older Early Cretaceous source rock ‎deposited under dysoxic to semi-anoxic conditions that could receive significant inputs of terrigenous ‎organic matter. These oils are most likely generated at the peak of oil generation window from their ‎parent source rock. Data from this study suggest that the immature Pabdeh Formation is a subordinate ‎source rock of the Asmari-Sarvak oil family that could play a minor impregnating role.‎

A stratigraphic section (155 meter in the thickness) was selected to determine biostratigraphic and paleoecological features of Qom Formation in southwestern Zanjan province, Central Iran geological zone. Field observations show that the Qom Formation is composed of cream to brown, thin-to thick bedded limestone, sandy limestone, alternation of shale and green marl, reef-coral limestone, and green marl and argillitic limestone.According to paleontological studies, a total of 24 genera and 18 species including 17 genera and 9 species of benthic foraminifera and 7 genera and 9 species of planktonic foraminifera have been identified. Based on the stratigraphic distribution of foraminifera, Borelis melocurdica-Borelis melomelo Assemblage Zone (Burdigalian, Early Miocene) has been recognized with certainty for the Qom Formation and 5-meters in the thickness of basal Qom deposits (Lower boundary on volcanic rocks) is considered to be the possible age of Aquitainian (?). Base on paleoecological features including the abundance of fossil assemblages, morpho-types, shell types of benthic and planktonic foraminifera, and the abundance of reef corals along with algal coexistence, the Qom sea has a normal salinity and semi warm to warm in the temperature. Also, light changes in the Qom Sea have been mainly in the Mesophotic-Oligophotic and Aphotic zones. Base on the fauna bathymetry, sedimentation of the Qom Formation has been occurred in a carbonate shelf ? in the lagoon, barrier to the deep open marine depositional setting.

Darbe Behesht Iron-copper deposit is located in the Dehaj-Sardoiye subzone of Uromieh-Dokhtar Magmatic Arc (UDMA) in Kerman region. The area is covered by Eocene volcanic rocks composed mainly of andesite, trachy-andesite, basalt and pyroclastic rocks (various types of tuffs and agglomerate). Based on major, trace and REE elements, these rocks are very similar to calc-alkaline lava with metaluminous-peraluminous nature. Enrichment of LILE (Such as K, U, Sr, Rb, Th, Pb and Ba) and LREE relative to HFSE (Such as Zr, Y, Ti and Nb) and HREE, high ratios of K2O/Rb and FeO/Mg reveal that the rocks under study were originated in an active continental margin subduction-related tectonic setting. Volcanic rocks affected by hydrothermal fluids which lead to the occurrence of epidotization, silicification with skarn alteration. Magnetite and chalcopyrite are the main ore minerals. The ore textures and structures are open space-filling, disseminated, vein-veinlet and replacement. According to geochemical study, the tectonic setting of the deposit is an extensional back-arc basin, which generated together with subduction of the Dehaj-Sardoiye subzone. Two important stages could be separated for mineralization. The first stage is accompanied by the generation of magnetite in volcanic and pyroclastic rocks and second ones related to reduction fluids that caused copper mineralization.

Ahar aquifer is one of the most active agricultural and livestock areas. The development of these activities has led to an increase in the use of chemical and natural fertilizers. Therefore, in this research, groundwater vulnerability in Ahar aquifer has been investigated using three frameworks; DRASTIC, SINTACS and GODS to identify vulnerable areas and prevent groundwater resources from more contamination. To use the simultaneous advantage of all three frameworks, two unsupervised and supervised combination techniques were applied to combine them. Invalidation step, nitrate concentration data and its correlation coefficient with the vulnerability index were used. The results show that the artificial neural networks (ANNs) model has better performance with a better determination coefficient (R2) and correlation coefficient (CI) than other techniques. Therefore, the supervised method has a higher ability than the weighted averaging method and can be used to determine the vulnerability of other areas.

Dimeh Spring emerges from the Zarab Anticline, Zagros Mountains (Iran), and the mean annual discharge is ~2.5 m3/s. However, preliminary evaluations suggest that the spring recharge is from the Zarab Anticline but in several previous dye tracing tests, that the dye was injected in the Zarab anticline, the dye was not seen in the Dimeh karstic Spring. Then, in order to find the catchment area of this spring, the present study has focused on tectonic aspects. For this purpose the tracing techniques were employed to determine the flow path and isotope studies used to determine the catchment elevation. First, the transverse fractures that extended from Zardkooh Mountains to Dimeh Spring area were identified and 30 kg of Uranine dye was injected in one of them, Khadang Valley. Unlike previous tests, the dye was observed in Dimeh Spring. Furthermore, the relationship between elevation and δ18O in precipitation shows that a big part of Dimeh Spring waters recharges in Zardkooh Mountains.