فصلنامه زمین شناسی ایران
پیاپی 66 (تابستان 1402)

The geometrical and kinematic characteristics of structural elements of north Makran have been measured and analyzed in five structural sections. Then, by using of balance cross sections and restoring the structures to their original state, the amount of shortening was determined in different parts of the area. The Bashagard, Dranar, Abenma, Koh Bahark and Vernach thrust faults with a WNW-ESE trend and 20 to 35 degrees dip towards the NNE are the main deformation controllers in this region and are the main cause of shortening. The excellent fit between N209/09 principal stress axis calculated based on the geometry of thrust faults and compression axis that formed folds, indicates that these structures were formed as a result of the same tectonic regime. The difference in the amount of shortening in different parts of the north Makran ophiolite mélange is also directly related to the thrust faults. So that, in western part of north Makran, thrust faults caused shortening amount 22.66, 22.85 and 14.32% in structural sections A-A', B-B' and C-C' respectively,. In the eastern parts, due to the lack of thrust faults and the presence of more strike-slip faults, the amount of shortening has decreased to 4.52% and 6.67%, respectively, in the sections D-D' and E-E'. Balanced cross sections and restoring the structures to the pre-deformation stages represent the narrow width of the early oceanic basin in the north of Makran.

Rock beds containing plant macrofossils of Norian in Alborz region belong to two stratigraphic units of Lalehband and Shahmirzad. The same beds in Kopeh-Dagh area belong to Mian-Kuhi Formation and in Central Iran belong to Qadir submember in Tabas region and Dehroud member in Kerman region. In general, plant diversity and vegetative cover during the Norian stage is less than Rhaetian especially Jurassic (Shemshak group) and the highest plant diversity of Norian in the Alborz basin is related to the phyllum of Pteridospermophytes (seed ferns) and in the Central Iran basin is related to the phyllum of Pteridophyta (ferns) indicating the higher humidity of the mentioned time in Central Iran basin and the drier climate in Alborz basin. The highest diversity of vegetation in Norian sediments throughout Iran belongs to the seed ferns (Pteridospermophyta) and the lowest diversity belongs to Ginkgophytes so that they comprise 32% (one third of the vegetation) and 6.5% of the total vegetation, respectively. Plant-covered areas throughout Alborz were interconnected during the Norian period and there was no extensive separation between them. The plant macrofossils assemblage in both Alborz and Central Iran basins confirms the relatively humid subtropical to tropical climate for the Norian but less humidity compared to the Rhaetian. Also, the vegetation of Norian in Alborz was less dense and scattered than Central Iran during Norian.

The carbonate interval of the Asmari formation along with sandstone deposits were deposited in most areas of the Zagros sedimentary Basin, including the Ahvaz area, in Oligo-Miocene. In this study, the effects of depositional and post-depositional environments on the reservoir quality of zone A7 of the Asmari Formation in well No. 4 in Ahvaz oil field were studied. The study of the sequences of the Asmari Formation in this section led to the identification of 11 carbonate facies, one evaporite facies, one mixed carbonate-siliciclastic facies, and one siliciclastic facies. Sedimentary environments of tidal zone, lagoon, coral reef and open sea were introduced for the depositional environment of identified facies. Due to the absence of sudden changes, it seems that the studied deposits were deposited in a ramp-type carbonate platform that was influenced by siliciclastic sediments from the Zagros river systems. The immature sedimentary texture of the sandstone facies indicates the proximity of the origin of the quartz sources to the carbonate basin. Among the diagenetic processes that have affected the examined sequences, the following processes can be mentioned: micritization, cementation, neomorphism, physical and chemical compaction, dissolution, fracture development and filling, dolomitization, and anhydritization. These diagenetic processes occurred in post-depositional marine, meteoric and burial diagenetic environments. Many fractures were filled with petroleum, which indicates that fractures, along with dolomitization, chemical compaction, and fenestral pores, are among the most important post-sedimentation complications to increase reservoir quality. While cementation and anhydritization resulted in reducing the reservoir quality by closing the pore spaces .

The studied Ghoshchi complex gabbros are located in the north of Uromiyeh city and NW of Central Iran structural zone. These rocks are intruded into the Cadomian basement, and late diabasic, granitic and aplitic dikes crosscut these gabbros. Clinopyroxene and plagioclase are the main minerals of the gabbros. These rocks are characterized by relatively low 87Sr/86Sr (0.703280-0.704343) ratios. Their isotopic signatures indicate a within plate environment for the formation of gabbros and derivation from an enriched mantle source. 40Ar-39Ar dating shows 316.55±1.68 Ma (Carboniferous period) as minimum age and are related to almost early phases of Neotethys opening. The Ghoshchi gabbros are originated more likely from a spinel-garnet lherzolitic mantle source with about 5% partial melting.

Sabalan is one of dormant stratovolcanoes of Iran with likely eruption, because there are many thermal springs around it. It has a slightly- eroded cone and, geologically, a short time has passed from its last eruption. According to eruption regime of such volcanoes, as well as its former activities, Sabalan volcanic eruptions may happen along with such hazards as tephra, lava, pyroclastic flows and lahars. Its eruption intensity on VEI scale is anticipated to be 3 to 5. Whenever this volcano shows awakening evidence, it would be necessary to take appropriate actions according to hazard zoning maps which are the subject of this study. That is, these maps are necessary for taking emergency actions. In this study, digital elevation data (DEM); satellite pictures; Arc GIS, ENVI and VORIS softwares; as well as atmospheric data of NCEP/NCAR center were used. For construction of pyroclastic density current spreads, the Malin and Sheridan (1982) model was employed. For preparation of lava flow hazard map, simulation model was used, and for preparation of lahar hazard zones, major valleys on the cone and its surroundings were identified and buffered using DEM and satellite data. According to this study, volcanic ashes will move eastward and threat Ardabil city and several nearby villages. Lahars would threaten many surrounding land uses and probably Meshkinshahr and Ardabil cities. Lava flows would damage many mountaineering shelters and ski facilities of Alvares. Additionally, Meshkinshahr, Moil, ski resorts as well as many shelters are at the threat of nuee ardentes.

The Pliocene-Quaternary sediments of the southern plain of Rafsanjan (west of Kerman province), have a variety of sedimentary copper minerals which can be used as gemstones and suitable for minerals/rocks colledctioners. The most important copper identified minerals include malachite, azurite, atacamite and paratacamite. Copper mineralization in this sequence is observed in three forms: cement (in conglomerates), nodules (in sandstones and tuffaceous mudstones), and alternating parallel to cross-laminations with calcite (travertines). The first two groups have only a decorative value, but the third group has the potential for jewelry making and is therefore presented as a gemstone. The leaching of copper from porphyry copper deposits in the upstream area (related to the Dehj-Sardouyeh belt) followed by the enrichment and deposition of copper in the young deposits downstream is considered the most probable model for the copper mineralization in the studied deposits. These deposits are called as exotic copper deposits.