Iranian Journal of Earth Sciences
Volume:9 Issue: 2, Oct 2017

The stress configuration and tectonic analysis of the Pan – African orogeny is drawn from the Igarra schist belt, southwestern Nigeria. The analysis of conjugate shear fractures of the schist belt indicates that two distinct compressive events (NE – SW and E – W) occurred in this Pan – African mobile zone. The palaeostress systems reveal a clockwise rotation of compressional axis from D1 (NE – SW) to D2 (E – W) during the propagation of the schist belt. The dominance of E – W compression related structures and the identification of E – W compressive stress in other Pan – African regions suggest that only the E – W compression probably had a strong regional effect during the Pan – African orogeny, other episodes of deformation most likely had a partially regional or local effect. The occurrence of structures related to the E – W compression in the younger rocks (granite and syenite) and the absence of structures related to the NE – SW compression in these rocks indicates that the E – W σ1 is a younger episode of deformation (D2) than the NE – SW σ1 deformation (D1) and probably lasted for a longer period. The dihedral angles (2ϴ) of the conjugate shear fractures range from 350 to excess of 800 and this situation shows that the orogeny produced a combination of both brittle and ductile deformation.

The Sungun copper porphyry deposit is hosted by a Tertiary magmatic complex in the Azarbayjan province , northwestern Iran. The Sungan mine in its southern and eastern parts is limited by early Miocene volcanic and by Late Cretaceous limestone rocks in northern and eastern parts respectively . The Sungun deposit is associated with a suite of porphyritic granitoids and late dikes intruding within Oligo-Miocene andesitic and upper Cretaceous limestone. The Sungun porphyry system developed in multi-stage, central intrusive rocks of the early Miocene age in the Tertiary Arasbaran Magmatic Zone (AMZ). A late post-mineralized dike (DK1a) is the first dike system after the replacement of the Sungun porphyry. It has been dated with a 20.57±0.27 Ma (±2 σ). New zircon SHIRIMP U-Pb data indicates that the Sungun porphyry crystallized within the time span from 20.69±0.37 Ma (±2 σ), and the Sungun porphyry and DK1a represent a near-dated intrusive with an age difference of about 0.12 Ma (120,000 y). Their range of 87Sr/86Sr ratios (0.70467 to 0.72278), 143Nd/144Nd ratios (0.51275 to 0.51214), 87Rb/86Sr (0.67497 to 0.67415 values), lead isotopes ranges from 18.67 to 18.86, 15.65 to 15.66, and 38.93 to 39.06 for the ratios of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb respectively, suggest the high contributions of depleted mantle-derived magmas in the generation of Sungun stock, but crustal-contaminated origin for monzonitic body in late magmatic activities in the area. This study shows that the source of the Sungun stocks is categorized in the upper crust, typically similar to the source of porphyry deposits.

Morphotectonic investigations were carried out by the use of morphometric indices which serve as a tool of identification in regions with active tectonic warp. Landforms in active deformation area are produced from relations of tectonic and surficial processes. One of the most significant landforms underground is rivers that are extremely responsive to tectonic movements mainly uplift and tilting. Accordingly, based on investigation of the rivers and interrelated drainage networks by the use of morphometric indices, we will be able to achieve valuable information about tectonic record of the study area. In this study, in order to find out the tectonic activities of the study area, geomorphic indices were surveyed in Garehbagh basin. In order to determine tectonic movement of Garehbagh basin area, six different morphometric indices including Mountain Front Sinuosity (Smf), Valley Floor Width to Height Ratio (Vf), Index of drainage basin shape (Bs), Stream Length Gradient Index (Sl), Hypsometric integral (Hi), Drainage basin asymmetry (Af) were applied to the study area. According to generated results, SL values change between Smf value according to generated outcome; the most active mountain fronts faults of the study area.. Deep and narrow valleys show low Vf values

The Zagros orogeny in Iran is associated with two successive geodynamic events during the Tertiary period, a Paleogene NE-directed regional crustal extension followed by a Miocene NW-directed regional crustal extension and a magmatic flare-up. The current study was undertaken to reanalyze previous structural work developed on the extensional Chapedony metamorphic core complex in Central Iran exhumed during Paleogene times. A new strain framework based on progressive dextral transtensional tectonics is proposed to explain the recorded structures. Its regional significance with other extensional areas in Iran is examined and an improved tectonic model is proposed to explain the southwestward drift of extension. This study emphasizes the key role of strain partitioning on the overriding plate as it relates to the increase in convergence obliquity during the Tertiary period. It is proposed that the regional extension is related to development of transtensional tectonics.

Dasht-e-Arjan is a northeast trending graben located 65 km west of Shiraz. It was formed along active segments of the Korrehbas fault, perpendicularly to the Shahnesh in and Salamati anticlines. Oriented sampling from bordering fault planes and striations was carried out to evaluate the relative amounts of paleostress/strain needed to form the graben. Measurements of e-twins and c-axis of calcite properties on XY and XZ planes, using five universal stages in a polarizing optical microscope, showed the presence of type I and II calcites. Because the calcite e-twins and fault striations register the last deformation phase, measurements of calcite e-twins show the plane strain K=1 in the last graben deformation phase. The inversion method, applied for the analysis of fault striation data, showed a plane stress ellipse (φ=1), (σ1=σ2), and a plane strain ellipse (r0=1). The mean orientation of the sub-vertical maximum principal-stress (σ1) was N23°.70°E, and the mean orientation of minimum principal-stress (σ3) was S58°.26°E. Based on the analysis of twinned calcite crystals, the mean direction of the determined compression and tension were S55°E ± 9.−32° and N35°E±11.−72°, respectively. Using multiple inversion methods, and based on the investigation of fault striation data, we can expect two stress phases. The paleostress phase, acting as a tensional regime, caused the formation of SW trending faults, while the recent phase caused the formation of new fractures within the study area. Based on field and laboratory analyses, it is suggested that a tension tectonic regime is dominant in the studied graben.

In this research, a high porous silicate mining waste that was prepared from Syah Kamar Polymetal Porphyry mine in order to malachite green dye (MG) removal has been applied. The characterization of this natural mineral was determined using the XRD, XRF, SEM and FT-IR analysis. The MG adsorption onto high porous activated waste was studied based on the parameters of pH, temperature, adsorbent dosage, initial dye concentration and contact time. The equilibrium and kinetic adsorption models were experimentally investigated. The obtained data have suggested that the process of MG removal followed up the Sips isotherm and pseudo-second order kinetic. The thermodynamic parameters values consist of ΔG˚, ΔH˚ and ΔS˚ confirms that the adsorption of MG is spontaneous and exothermic reaction. In the optimal condition the removal of MG was more than 93%. This method has a number of advantages, including being low-cost and non-toxic and the availability of natural adsorbent.

A calcareous nannofossils biostratigraphic study has been carried out on the chalky limestones located in South Gorgan, north of Iran. The study is aimed at determining the age and nannofossil biozonations of the well. The samples were prepared using smear slide technique. Thirty seven calcareous nannofossils species were identified and used to make biostratigraphic zonations and dating of the strata. The distribution of the calcareous nannofossils enabled the establishment of five zones: Quadrum trifidum (CC22),Tranolithus phacelosus (CC23), Reinhardtites levis (CC24), Arkhangelskiella cymbiformis (CC25) and Nephrolithus frequens (CC26) belonging to late Late Campanian – late Late Maastrichtian following standard zonation schemes of previous workers. The zones were based on the first and last occurrences of marker species.

The northeast region of Birjand is located in Lut structural and geological province. In this area we can distinguish two separate volcanic rock groups: intermediate to acidic volcanic rocks, including dacite, andesite, rhyolite and trachyandesite; and basic rocks, including basaltic andesite, mugearite and basalt. In this region, intermediate to acidic rocks, which belong to the Eocene-Miocene period according to dating results, are the main formation, and we can see the second, younger (evidently Pliocene) volcanic rock group as outcrops with a northwest-southeast trend in the background of the intermediate to acidic volcanic rocks. Geochemical studies show the differences between these two distinctive groups clearly, and reveal that intermediate to acidic rocks belong to active continental margin calc-alkaline rocks. Studies also show the related mantle magma has been influenced by subducted lithospheric slab and metasomatized by crustal materials. The second volcanic rock group belongs to within-plate alkaline rocks. The linear successions and the arrangement of the basic volcanic rocks’ outcrop in a northwest–southeast trend is in relation to the right lateral fault zones that have branched out of the Nehbandan fault system. As a result of the extensional regime development, and the high depth of these faults, alkaline magma could have formed and ascended to the surface. Considering with accepted ideas concerning eastern Iran geodynamic evolution and our new data, we have tried to complete the previous findings and present a seven-stage model for geological evolution of eastern Iran.

The Behabad region is located within a tectono–sedimentary zone in southeast Yazd province, Central Iran. The tectonic activities have deformed and faulted the Mesozoic and Quaternary formations in this area. The faults in Kuhbanan and Behabad have played a key role in the evolution of geological events, mineralization, and the formation of Behabad–Kuhbanan horst. These faults have separated the Posht-e-Badam block from the Tabas block and the Behabad zone from the Abdoghi–Ravar tectonic zone, respectively. Remote-sensing techniques and field observations show that the Pb–Zn veins share similar trends with the structures. The compressional system induced by the activities of the Behabad-1 and 2 fault systems have caused the formation of thrusts, drag, and sigmoidal folds, the North Behabad horst, and shear zones containing Pb–Zn mineralization. The Mississippi Valley-type (MVT) deposits and strata band mineralization types are present in the study area. In terms of the temporal phase controller, it is consistent with the tectonic-magmatic model of the Late Paleozoic–Triassic period; in terms of the spatial controller, mineralization is situated in the tectonic–metallogeny province of Central Iran and the ore deposits that mainly follow the geometry of the thrust faults’ crushed zones. The thrust fault that drives the dolomite unit over the limestone is the main cause of the ore solutions migration. According to the MVT mineralization and the correlation between structures and mineralization, the sulfide deposits can be potentially found at the base of the Permo–Triassic units in the studied area. There are several active and non-active Zn–Pb mines such as Abheydar, Rikalaghi, and Tapesorkh.