Iranian Journal of Earth Sciences
Volume:17 Issue: 2, Apr 2025

Sequence stratigraphic analysis provides indications of depositional systems and specific cycles of sedimentation. Such studies are useful for the prediction of quality and geometry of reservoir systems. Ditch cuttings and Well log data recovered from the Middle-Late Miocene “OMAH-1 Well”, Offshore Niger Delta, Nigeria were analysed in order to have a proper understanding of rock units’ relationships with chronostratigraphy and depositional environment-significant forms. Results of paleobathymetry of the deposits using benthic foraminifera ranged from coastal deltaic to shallow marine (shallow inner neritic, inner neritic and middle neritic)  settings. Two foraminiferal zones and four palynological zones indicative of Middle–Late Miocene age was identified. Four (4)  sequence boundaries (SBs) were identified and dated: SB 1 at 7250 ft. dated 10.6 Ma, SB 2 at 6530 ft. dated 10.35 Ma, SB 3 at 4400 ft. dated 8.5 Ma and SB 4 at 2210 ft. dated 6.7 Ma. Three (3) maximum flooding surfaces (MFS) were also identified viz: MFS 1 dated 10.4 Ma at 6910 ft., MFS 2 dated 9.5 Ma at 5150 ft. and MFS 3 dated 7.4 Ma at 2930 ft. These surfaces were used to subdivide the stratigraphic column in the well section into five depositional sequences (Sequence I-V) characterized by Lowstand systems tract, Transgressive systems tract and Highstand systems Tract. The depositional sequences identified have quality reservoirs and source rocks with high potential for hydrocarbon generation.

Coal beds are very complex porous media that exhibit heterogeneity, dual-porosity, and stress sensitivity. Simulation models for fluid flow from coal matrix for coal bed methane (CBM) and enhanced coal bed methane (ECBM) recovery have significantly progressed in recent decades. Analytical models have limitations or challenges in application due to assumptions and oversimplification. Therefore, in this study, numerical modeling and simulations were carried out to investigate the fluid flow behavior in the microchannel of the coal matrix. A variation in pressure drop was considered to evaluate the flow pattern in the coal matrix. Analysis was carried out to assess the effect of pressure drop on fluid velocity in the microchannel. The results of the simulations indicated an increased fluid velocity with pressure drop. Well-developed and connected microchannel was significant for transporting fluid in the coal matrix. The Simulation results were found helpful in estimating the critical pressure drop to enhance fluid flow in the microchannel of the coal matrix.

The incorporating frequency measurement technique has a very important role in the determination of achievable sensitivity using NMR-based magnetometers for earth field measurements. This is while, the selection of the frequency calculation algorithm, determines the required resources of the digital processing hardware for such magnetometers. We have previously developed a proton precession magnetometer equipped with a spin echo mechanism that could measure the gradient of the magnetic field as well as the magnitude of the magnetic field. In this magnetometer, a switching field is used for making the spin echo which decreases the effective spin-spin relaxation time constant. The reduction of this time constant increase the decay rate of the NMR signal and so the frequency calculation for obtaining the Larmor frequency should be accomplished in a shorter time. In this work, different frequency calculation methods are investigated for achieving high-sensitivity earth field measurements. In this regard, both time domain and frequency domain analysis of free induction decay (FID) frequency calculation is implemented and compared. The effect of SNR and decay time constant of FID signal on the accuracy of Larmor frequency calculation is discussed. It is shown that frequency domain analysis is much preferred for frequency calculation especially when using the spin echo enhanced proton precession magnetometer.

A comprehensive assessment and evaluation of metallogeny in mafic-ultramafic rocks, which is essential in determining the novelty value and direction, have not yet been found in past studies. This study aimed to determine the trends and opportunities related to the aforementioned subject using bibliometric methods based on the SCOPUS database, through visualization and analysis using the VOSviewer application; so that we can focus on research that has not been done for the next forward (as the benefit). The results showed a total of 972 publications during the 1969-2022 period, with the highest contributing countries being China and Australia, while the Chinese Academy of Sciences is the most productive affiliate. Ore Geology Reviews is the journal with the highest number of publications on this topic. Concurrently, the most productive authors are Santosh M and Mao J. The Earth and planetary sciences, environmental sciences, and engineering dominate the subject areas. Geographically, related research is still focused on China, while gold, zircon, and copper are the metals with the highest focus. In addition, widely used equipment or methods approaches include fluid inclusions, U-Pb zircon dating, and Hf isotopes. Recent trends in research topics include geochemistry, petrogenesis, geochronology, fluid inclusions, and tectonic setting. Low-frequency research topics include ore magmatic systems, reduced intrusion-related, tonalite, palladium, La-ICP-MS, U-Pb dating, lithium, metavolcanic rocks, black shale, hydrocarbons, Rb-Sr geochronology, rare earth elements, Re-Os analysis, Sm-Nd, Sr-Nd-Pb-Hf isotopes, and dunite-peridotite-pyroxenite-gabbro associations.

The Eshkavarat intrusive bodies, consisting of monzonite, quartz monzonite and syenite to granite composition, with late Cretaceous age, are located east of Gilan province in western Alborz and formed as 4 large bodies, in the southern part of the study area. Petrographically they show perthitic and micrographic textures and are composed of K-feldspar, quartz, plagioclase and biotite as main minerals with accessory iron oxides and apatite. These rocks have high SiO2, alkalis, FeO(total)/MgO. In the spider diagram show subparallel, linear, and homogeneous REE profiles with enrichment of LILE. Granitoid show high Ga/Al, Zr, Th, Rb, and rare earth elements (REE) (except Eu), low CaO, MgO and strong depletion in Ba, Eu and Sr. They have the typical geochemical characteristics of A1-type granites. Tectonic discrimination diagrams show the tectonic setting of the within-plate granite (WPG). According to the tectonic model presented for the study area, a tectonic window and an extensional regime above the supra-subduction zone appear to have been created by the subduction of the oceanic crust of the southern Caspian Sea after the end of the Upper Cretaceous. The mantle magma then rose up through the tectonic window. Direct release of this mantle magma  has generated oceanic plume-like (OIB) rocks in the region. This mantle magma, arrest under the crust, causing its partial melting, and finally, fractionational crystalisation of mafic minerals and minor crustal assimilation, primarily parent magma of A1 granitoids and syenitic A1 rocks was generated, then, by fractionation felsic minerals A1-type granitic magmas  were created.

In this paper, we introduce the migmatitic rocks in the Qandol area as a part of the Bulfat Igneous Complex (BIC) complex in the Zagros Suture Zone, northeast Iraq for the first time. The main protolith is mafic rocks which are preserved in some areas. Meanwhile, the partially melted parts (leucosomes) have a trondhjemite composition, with plagioclase being the dominant mineral phase. Geochemical analysis reveals that the leucosomes portion exhibits higher concentrations of Na2O and CaO, accompanied by lower levels of K2O, indicating a stronger association with calc-alkaline features. Meanwhile, the melanosome demonstrates a tholeiitic nature, attributed to its elevated content of compatible elements like Mg and Fe within the residual materials such as amphibole and pyroxene. The thermobarometry assessment indicates that the leucosome parts were crystallized at a temperature of 670 –700 °C and a pressure near 0.1 GPa. Furthermore, phase equilibrium modeling using the GeoPS software indicates initial melting has occurred at 790°C – 920°C and 0.1– 0.4 GPa.  The estimating of the P-T of the present migmatite infers that the metamorphism has occurred at high temperature and low pressure either in the root of the mature arc or in a shear zone as a result of hot oceanic subduction beneath the Sanandaj-Sirjan Zone (SaSZ) in the late Cretaceous or younger. The presence of the high-T migmatite in the Zagros Sutures Zone without a clear relation to the sole metamorphism in the base of ophiolite members in the Qandol area would be much more useful to understand the tectono-magmatic processes in the pre- to syn-collision regime during the closer of the Neotethys ocean.

Estimating the boundaries of structures is a critical task in interpreting potential field data. In general, the enhancement filters based on derivatives are used to map these boundaries. The theta and normalized horizontal gradient are two popular filters used in mapping the structural edges, which can balance the signals with different amplitudes lying at different source depths beneath the subsurface. However, the use of vertical derivatives calculated from the traditional technique in these filters often amplifies noise. In this study, the performance of these filters has been improved using stable vertical derivatives from the finite-difference approach. The algorithms are tested on synthetic and real data from the Vredefort dome (South Africa). The findings from the synthetic examples show that finite-difference approach-based filters can provide stable results compared to the traditional calculations. The findings from the real application show that the finite-difference approach can provide a clearer image of the subsurface structures present underneath the study area.

Creating a safe environment is of utmost importance in any project. One crucial aspect of ensuring safety is addressing potential hazards. In the context of road construction projects involving hard rock, one significant risk is flyrock. Flyrock refers to the occurrence of fragments being propelled outside the blast area with high energy and speed during blasting operations. These flying rock fragments have the potential to cause severe and irreversible injuries to both people and equipment. The objective of this research is to identify and assess the risks associated with flyrock in road construction projects involving hard rock. To accomplish this, a collaborative approach was adopted, involving experts, analysis of scientific records, as well as observations and inspections. A thorough examination revealed a total of 54 flyrock events, which were prioritized for further analysis. To quantify the probability of flyrock occurrence, a fuzzy fault tree analysis was employed. This analysis method takes into account various factors and uncertainties to yield a calculated value of 0.4907, indicating the likelihood of flyrock incidents. Additionally, the intensity of flyrock consequences was determined to be 0.2248 using the fuzzy Delphi analytical hierarchical process. These assessments collectively indicate the potential severity of flyrock incidents. Based on the evaluations conducted, the resulting risk number associated with flyrock reached an undesirable level of 12. It highlights the imperative need to recognize and evaluate the risks posed by flyrock during road construction projects. By doing so, appropriate measures can be implemented to mitigate the occurrence of flyrock and minimize potential harm to individuals and equipment. Recognizing and understanding the risks associated with flyrock is a crucial step towards improving safety in road construction projects involving hard rock. Through the insights gained from this research, proactive measures can be taken to prevent flyrock incidents and ensure a safe working environment for all involved.