Geopersia
Volume:10 Issue: 1, Winter-Spring 2020

Coralline red algae are highly abunadant and well diversified in the well exposed carbonate deposits of the Lower Pliocene Shagra Formation at Wadi Wizer, Red Sea coast, Egypt. Lithostratigraphically, the Shagra Formation unconformably overlies the Late Miocene Marsa Alam Formation and underlies the Quaternary deposits. This carbonate facies is dominated by different assemblage of coralline red algae in the form of in situ crusts, rhodoliths, fragments and corals, bivalve shell fragments, bryozoans, benthonic and palnktonic foraminifera. The systematic study and the taxonomic investigations carried out on the coralline red algae, twenty one coralline algal species were recognized and described for the first time (most of which belonged to nongeniculated coralline algae, . Detailed microfacies analysis of the Lower Pliocene Shagra Formation led to the recognition of eight microfacies types (six of carbonate facies and two of siliciclastic facies) on the basis of Lithological characters, faunal content and sedimentary strutcures, indicating that the Lower Pliocene sequence was deposited in transgressive – regressive cycles ranged from near shore, warm shallow inner to middle neritic marine water environments with development of reefal facies.

Stable isotopes (Deuterium and Oxygen-18) have a broad application in many of water related sciences. Precipitation is the most important input to the water cycle which shows considrable spatial and temporal variability in its isotope content. To study the precipitation isotope content, 51 samples from August 2015 to July 2016 have been collected mainly on a monthly basis with few events based samples at five stations in Haraz basin, north of Iran. A local meteoric water line (LMWL) of the Haraz basin is expressed by the equation δD=7.66δ18O -8.48‰. Both slope and interception of LMWL are lower than corresponding values for the Global Meteoric Water Line (GMWL). The isotope composition of precipitation generally shows a seasonal fluctuations and it has been influenced by rainfall amount and ambient air temperature. Considering the precipitation chemistry at Haraz basin shows that the Ca^(2+)and HCO_3^- are the main ionic species accounting for 70.8% of total ionic concentration. Total ionic concentration shows a seasonal trend of lower values in wet and higher concentrations at the dry months. The absence of strong correlation between ion species, suggests that precipitation’s chemistry affected by crustal elements, marine salt and anthropogenic activities.

Ultramafic rocks of the ophiolitic complexes are prone to alteration and degradation, and therefore, ease of mobility of heavy metals such as nickel (Ni), chromium (Cr), cobalt (Co), lead (Pb), and vanadium (V), resulting in environmental hazards. The ultramafic rocks of the ophiolitic realm of Kurdistan province, west of Iran, show field and compositional evidence for such hazardous conditions. The ultramafic rocks are extremely rich in Mg, Fe, Ni, Cr, and Co and they are severely altered and decomposed, resulting in the formation of Serpentine minerals including chrysotile (white asbestos). Comparison of the heavy metal concentrations with standard data indicates that the samples are enriched in Ni, Cr, Co, and V. Natural processes such as alteration and anthropogenic factors such as mining, facilitated the release and mobility of these heavy metals. For reactive contaminant species, attenuation of the pollutant transport occurs by various processes including chemical precipitation, sorption, redox reactions and changes in pH.

Ahwas sandstone and Kalhur evaporate members are two main constituents of the best reservoir unit of Zagros region, i.e. Asmari Formation. Poorly cemented to loose nature of the sandstone member and it’s well textural maturity provide highly porous and permeable zones, whereas highly compacted nature of the evaporate member provide impermeable zones in the reservoir. This paper aims to study the lithological characteristics of these members and their lateral and vertical distribution in two main zones of the Zagros, i.e. Dezful Embayment and Abadan Plain.The sandstone member is well developed in central part of the northern Dezful Embayment and Abadan Plain. It is poorly developed in the southern Dezful Embayment, except for its NW. Based on its distribution patterns, the bordering fields around the central part of the northern Dezful Embayment and Abadan Plain are found more susceptible for development of the stratigraphic traps. On the other hand, The evaporate member is well developed in NW of the northern Dezful Embayment but is absent in southern Dezful Embayment, except Parsi and Karanj fields. Therefore based on its distribution pattern in the studied area, the NW bordering fields between northern and southern Dezful Embayment have greater potential for stratigraphic traps development.

The present research focuses on a detailed facies description and interpretation of five alluvial fans of the Qazvin Plain. Beside the tectonic activity that leads to the localization of the fans on the northern margin of the Qazvin Plain, the climate has a significant role in the occurrence of their facies. The alluvial fans are divided into three facies groups: group 1, group 2, and group 3. Alluvial fan 1 is dominated by the episodic matrix to clast-supported gravel, interbedded with a subordinate, and red matrix-supported gravel deposited by non-cohesive debris flow. Groups 2 and 3 are characterized by deposits of debris flow, mud-rich debris flows, channelized, non-cohesive debris flows, hyperconcentrated flows, and sheet floods. The hallmark of fan 3 is disorganized, very poorly sorted gravel, lack of erosional bases, and a wide particle-size range from clay to outsized-boulders. The facies interpreted as a result of debris flow following episodic localized tectonic activity of the Kavendaj Fault along the fan head during Quaternary. Relatively insignificant changes of the sedimentary facies of the studied fans from debris-flows to sheet floods during the accumulation of the three groups are attributed to a slight variation of climatic conditions, source rocks, and tectonic activity.

Gazestan magnetite-apatite deposit is located in Central Iran and Bafq region, which has been occurred in form of veins, veinlets, and small apatite lenses as well as magnetite in metasomatic rock types such as green chlorite-actinolite rock units. These rocks are situated in the carbonate-volcanic complex of Upper Precambrian-Lower Cambrian Rizo formation. In this study, staged factor analysis and Concentration-Number (C-N) fractal model were used based on core samples for determination of main rock type for Rare Earth Elements (REEs) mineralization. Hence, after normalizing the data by staged factor analysis, the target factors were determined and the factorial map was generated using the C-N fractal modeling. The results showed that the first factor of the sixth step (F1-6) is contained of the REEs with phosphorous. Afterwards, results obtained by the C-N fractal method on the F1-6 indicated that there are five populations for REEs which are compared with different lithological units by evaluation matrix. The evaluation matrix confirmed the compliance of magnetite-apatite units with the high values of mineralization factor. The REEs were accumulated in magnetite-apatite units based on highest Overall Accuracy (OA).

This study is an attempt to investigate the effect of the nano-kaolinite concentration on the liquefaction resistance of liquefiable sand from Gorgan city of Iran. To examine the influence of the nano-kaolinite concentration on the liquefaction resistance of nano-kaolinite-sand mixtures, three different nano-kaolinite concentrations: 3%, 6% and 9% were prepared. Cyclic triaxial tests were conducted on pure sand and nano-kaolinite-sand mixtures. Triaxial test was repeated two times for each nano-kaolinite-sandy soil mixtures and the mean values and standard deviation was obtained. Based on the obtained results, nano-kaolinite concentration has a contradictory effect on the liquefaction resistance of the studied soil. It was found that the influence of nano-kaolinite concentration on liquefaction resistance of the sand should be evaluated using a critical value of nano-kaolinite concentration. Below critical value (under 3% nano-kaolinite content), liquefaction resistance decreases with the increase of nano-kaolinite concentration. Above this value, liquefaction resistance enhances with the increase of nano-kaolinite concentration. The results showed that the liquefaction resistance of 9% nano-kaolinite-sand samples was higher than pure sand sample. It was found that at the same cyclic stress ratio, liquefaction resistance and axial strain of samples decreases with the increase of the confining pressure.

In Western Kopet Dagh, the lower Cretaceous carbonate series contains distinctive assemblages of calcareous algae, chiefly Dasycladales which are primarily studied in this work. Based on the significant presence of certain species, the Zard Formation, assigned to the Valanginian and, in its upper part, to the Hauterivian or base of the Barremian, is subdivided into two intervals, respectively A and B. Higher up, the Urgonian-type Tirgan Formation, assigned to the Barremian and Lower Aptian, is subdivided into intervals C and D. On this occasion, the taxonomy and systematics of 17 species of Dasycladales and one incertae sedis found in the series are discussed, in relation to some recent standpoints. Out of this inventory, the biogeographic distribution of 11 species is particularly interesting. During the Lower Cretaceous, the Kopet Dagh region was quite isolated, northeast of the Izanca, a branch of the Tethys. Assemblages encountered in this region are compared with other areas, encompassing Iberia to the northern margin of West Gondwana. Finally, the stratigraphic and/or biogeographic distribution of two species appears to be partially related, in one case to the Valanginian OAE1 event, in another case to one or more obstacles in relation to the paleotectonic context.

Major aim of this study is to define the copper and gold anomalies using the combination of the Concentration-Number (C-N) fractal and the stepwise factor analysis, based on stream sediment samples in Lahrud 1:100,000 sheet, NW Iran. The case study is situated in Alborz-Azerbaijan structural zone. Elements related to Au and Cu hydrothermally mineralization were selected for this study, according to ore deposit types of the study region. Staged factor analysis was carried out in four steps. Consequently, all noise elements were removed after applying four steps of factor analysis and As, Sb, Sn, W, Co, Mn, Zn, Ti, Ba, Ni, Cr, Au, Cu, and B were grouped in the five factors. Cu and Au are grouped on factor 4 of the last step (FAC4-4). The C-N log-log plots for factor scores, Au and Cu were plotted and threshold values were determined in order to a generation of elemental distribution maps. The anomalous areas for metallic elements specifically copper and gold, are located in the NW and SW parts of the region which show a correlation between alteration zones, faults, and intrusions.

This work describes a knowledge-guided clustering approach for mineral potential mapping (MPM), by which the optimum number of clusters is derived form a knowledge-driven methodology through a concentration-area (C-A) multifractal analysis. To implement the proposed approach, a case study at the North Narbaghi region in the Saveh, Markazi province of Iran, was investigated to discover porphyry Cu-bearing favorability zones. Whereby, various exploratory indicators were extracted from a multidisciplinary geospatial data set comprising of geology, geophysics and geochemistry criteria. Those indicators were prepared from magnetometry and geo-electrical survey, lithogeochemical samples and geological field operation. The optimum number of clusters was obtained by running the knowledge-based methods of index overlay and fuzzy gamma operators, indicating five clusters from the C-A multifractal curve. Accessing to exploratory drilling lets us to find out the most efficient synthesized favorability map that was generated by a fuzzy algebraic sum operator (or a gamma value equal to one). Assuming the optimum number of clusters, three clustering methods, namely fuzzy C-means (FCM), K-means and self-organizing map were examined for MPM. Note that the FCM as an unsupervised data-driven methodology, had superiority over other clustering analyses by generating mineral favorability map in close association with drilling results.

The the Middle Cretaceous-Lower Miocene petroleum system of the Kupal oil field, located in the Dezful Embayment has been studied. The Kazhdumi and Pabdeh are main source rocks, the Sarvak, Ilam and Asmari formations are reservoir and the Gachsaran formation is the seal rock. According to geochemical analysis the Kazhdumi and Pabdeh contributed to oil production and feeding the Asmari and Bangestan reservoirs. Also, the lateral migration from the Kupal to other fields is ruled out but vertical migration led to feeding the Asmari and Bangestan reservoirs. Considering burial history diagrams in the syncline area between the Marun and Kupal fields, expulsion phases from the Kazhdumi were about 9 and 7 million years ago, respectively. Also in the crestal axis area of these structures (about 6 and 4 million years ago), the hydrocarbon generation and expulsion started from the Kazhdumi Formation. In the syncline area between the Marun and Kupal oil fields, the Pabdeh source rock has entered the hydrocarbon generation and expulsion phases approximately 6 and 3 million years ago, respectively. Based on 3D hydrocarbon system modeling, the oil volume generated from the Pabdeh and Kazhdumi in the Kupal are estimated to be 42 and 113 billion barrels, respectively.

NW-tending faults in Central Iran are expected to represent dominant dextral components due to their orientation with respect to the northward motion of the Arabian Plate with respect to Eurasia. However, previously published works, as well as the focal mechanism solution of the area's earthquakes, indicate evidence of sinistral kinematic along the major faults in Central Iran. Here we present detail structural kinematic data on the eastern part of WNW trending Kushk-e- Nosrat (KN) Fault zone to unravel the structural architecture and regional distribution of kinematic change at the northwestern margin of Central Iran zone. We classified fault data into two dextral and sinistral kinematic categories. Based on cross-cutting relationship and the superposition of kinematic indicators the sinistral related structures are younger than the dextral one. The structural analysis of the KN Fault zone data suggests a kinematic inversion from dextral to young sinistral which is regionally attributed to the clockwise rotation of rigid South Caspian Basement Block (SCB) with respect to Eurasia.

Permian stratigraphic sequences are widely distributed throughout Iranian, making this one of the best locations in the world to study15 this geological time interval. Nevertheless, some units lack detailed biostratigraphic characterization which is essential for16 palaeogeographic reconstructions. This preliminary study comprises a palynological assessment of a Permian stratigraphic section17 cropping out in the Ajabshir area (SW Azerbaijan, NW Iran). The continuous and relatively well-exposed Ajabshir section comprises18 Unit 3 of the Dorud Formation and the Nesen and Ruteh formation In this area, the Dorud Formation starts with the Unit 319 unconformably overlying the Mila Formation, with its lower units missing. Unit 3 (48 m thick) is characterized by sandstones with20 siltstones and shale intercalations and an upward increase of limestones. The overlying Ruteh Formation (192 m thick) consists21 mainly of carbonates with scattered coarse sandstone intercalations and dolomitic limestones