GEOSCIENCES
Year:2021 | Volume:30 | Issue:118|Papers Count:22

Jurassic deposits are well spread in the north of Karim Abad village, north of Bahabad, central Iran. These deposits contain 41 species of palynomorphs in which there are 15 spore species (12 genera), 15 pollen species (10 genera), and 10 species of cyst of dinoflagellate (three genera). Vertical distribution of miospores and cyst of dinoflagellate, and the first observed occurrence (FOO) and the last observed occurrence (LOO) of selected taxa allow erection of two biozone: Klukisporites variegatus-Chasmatosporites apertus Interval zone and Nannoceratopsis triceras-Nannoceratopsis gracilis Assemblage zone. The relative abundance of dinoflagellate cyst, spore, and pollen is 86. 21%, 7. 2%, and 6. 6%, respectively. Based on relative abundance of miospores’ parent plant fossils, ferns, cycads, and conifers are 37%, 31. 5% and 11. 82%, respectively, and related sporomorph ecogroups (SEGs) indicate that they occurred in different environments such as upland, wetter / drier lowland, river and coastal with temperate-sub-tropical and humid climate. Furthermore, based on the absence of coals in the Hojedk Formation and the high relative abundance of dinoflagellate cysts, it can be concluded that the shallow sea water was prominent here and spores and pollen were transported and sedimented there.

A stratigraphic section from the upper part of Ziveh Formation (Middle Miocene) has been surveyed in north Ojagh Kandi village, northeast Kalibar, Azarbaijan province. Ziveh Formation overlayed by Tortonian sediments as an angular unconformity in the studied section and its lower boundary covered by recent alluvium. A diverse body fossil assemblage includes molluscan, plants, and vertebrate collected from this section. Among them, abundant ichnofossils of bivalves on woodground, Teredolites longissimus discovered in a horizon. Occurrence of wooden substrate in this horizon shows first events of rising of the sea level, and its basal background is considerable for the lower boundary for TST. On the other hand, Teredolites bearing horizon indicates beginig of transgressive event in the sequence stratigraphic interpretation of the studied section.

The peridotites from Marivan-Kamyaran ophiolite suite (MKO), outer Zagros ophiolite belt, western Iran, are studied for the petrological and geochemical characteristics. Both mantle and crustal peridotites are present in the Marivan-Kamyaran ophiolitic sequence. Extensive compositional variations in MgO, Al2O3, Cr, Ni and Al2O3 / SiO2, combined with the abyssal (MOR) and supra-subduction zone (SSZ) nature of the peridotites, are indicative of variant degrees of depletion of the mantle peridotites. Various degrees of depletion are consistent with a wide range of partial melting percentages (10-15%) obtained from non-modal backward partial melting models. The enrichment in HFSE such as Hf, Ti, Ta and Th indicates melt-rock interaction in the mantle peridotites; while, the enrichment in U and LIL elements such as Cs, Rb, Pb is most probably related to the fluid-rock interaction. It is suggested here that MOR nature of a part of the mantle peridotites in the region has been changed to SSZ characteristics in later stages through processes such as melt-rock interaction. It is likely that, similar to other occurrences of outer Zagros ophiolite belt, mantle peridotites from MKO with MOR and SSZ characteristics had been originated in MOR setting, before their composition were modified in a SSZ environment.

The Mahneshan Basin is one of the syntectonic Neogene sub-basins of the Central Iran. The basin is filled by about 4 km of the Miocene Upper Red Formation deposits, showing a combination of halokinetic and growth strata patterns. To assess the provenance evolution of sediments in north of the Mahneshan basin named the Hesar section, we conducted remote sensing mapping, field survey, as well as petrographical and modal analyses of sandstones. Our results reveal that the sandstones are fine to medium-grained sedarenites (Q46F10Rf44) and mainly derived from fine-grained siliciclastics, metamorphic, carbonate, chert and andesitic volcanic rocks, which were exposed in an orogenic tectonic setting (Qm34F10Lt56 and Qt49F10L41). The combination of provenance data and northeastward paleocurrent direction, reflect that the sediments mainly supplied from basement rocks of the Takab Complex and Qom Formation in southwest of Mahneshan Basin. The unchanged provenance of sediments along the studied succession, indicate that regional shortening and uplift of parent rocks has begun before deposition of the Upper Red Formation (Miocene) and continued during deposition of these sediments. This is in agreement with previous age assumption for exhumation of Takab Complex during Oligocene time.

The current study was conducted on sedimentary units of the 1: 100000 sheet of Jam and Sorkheh in Semnan Province, northeast of Iran. Because of its special geochemical properties, lithium can be concentrated in sedimentary rocks with clay minerals. Samples were collected from stream sediments and lithogeochemical in three steps and were processed using Concentration-Number fractal modeling. Concentration-Number fractal modeling is a suitable geochemical exploration method to separate anomaly from the background. It was utilized to identify anomalous areas for lithum and the results were presented in the form of maps. As a result, The Gharavol kooh area of Biabanak in central part of sheet of Sorkheh. According to the lithology of the area, which contains marl and clay minerals (Illite and Cholorit), It was main anomaly between the two sheets. This area should be further investigated in Detailed exploration studies.

The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite-muscovite granites with alkaline and peraluminous affinities. They show enrichments of LREEs relative to HREEs and LILE relative to HFSE with negative anomalies in Nb, Ta and Ti, in normalized trace element diagrams. The leucocratic granite of the Alvand batholith resemble A-type and can be further classified in two of A and A' types granite. The trace elements content of A-type is much higher than A'-type granite. Based on geochemical data, it seems that A-and A'-type granites were generated from partial melting of mantle source. As mantle magma ascends, fractionate and empalce into the crust, A-type leucocratic are formed with minimal contamination and A'-type leucocratic with significant contaminant with continent crust are formed. Field and geochronology data suggest that the leucocratic granite were generated in the late Jurassic, which is contemporaneous with the subduction of the Neo-Tethys oceanic crust beneath the central Iran. It seems that the leucocratic granites were emplaced during a local extensional phase as dykes and small bodies in the Alvand batholith.

Geochemical investigation of Kazhdumi and Pabdeh formations suggest a shaly and carbonate lithology as well as a suboxic-anoxic marine depositional environment for both formations. On the other hand, the thermal maturity of the Kazhdumi Formation is equivalent to the mid of oil window while thermal maturity-related parameters show that the Pabdeh Formation has not entered the oil window. Biomarkers are indicative of derivation of the four oil samples from a carbonate-shaly or marly source rock. Also, thermal maturity-related biomarkers reflect a peak mature stage for all of the four samples. Different values of oleanane index in oil samples is implying a more significant role of the Pabdeh Formation in hydrocarbon embedded in 36, 56, 55 wells in compare to well number 22. In general, oil-source correlation introduces both Kazhdumi and Pabdeh formations as source rocks for the crude oils.

The Late Neoproterozoic-Early Cambrian albite-bearing metasomatite, rhyolites and rhyodacites predominantly constitute the host rocks of the Choghart magnetite-apatite deposit in Central Iran. The geologic evidences show three types of albites in the host albite-bearing metasomatite. The performed mineralogical and geochemical investigations display enrichment of REE-Y-Ti-Th in the pink and fleshy red albites, whereas the white albites are barren without any ore mineralization. The concentration of REE-Y-Ti-Th-U bearing minerals along the fractures, the variation of Th/U ratio and result of stable isotopes studies of the calcites syn-paragenesis with the abiltes reveal the involvement of mixed magmatic and high-midium temperature hydrothermal processes play an important role in the ore genesis. The similarity pattern of the REEs and trace elements in different types of abilte-bearing metasomatite and rhyolite manifest the origin of REE-Y-Ti-Th mineralization as the rhyolitic-rhyodacitic magmas, related to a continental/oceanic subduction zone. According to this research, tectono-magmatic setting of the albite-bearing metasomatite in the Choghart deposit is suggested as a Calc-alkaline magmatism, associated with the active continental margin and oceanic island arcs.

The present study deals with the ammonites from the upper part of the Chaman Bid Formation, member 4 (Middle-Upper Jurassic) at the type locality. Lithostratigraphicall, it is consites alternation of limestone and marls. Following ammonite families are present: Perispinctidae, Ataxioceratidae, Haploceratidae, Oppeliidae and Aspidoceratidae, which indicate the Biozones: Hybonoticeras hybobotum, Semiformiceras semiforme, Semiformiceras fallauxi, Microcanthoceras ponti and Micracanthoceras micracanthum Zones. Paleobiogeographicall, the ammonite fauna is closely related with the Submeditteranean Provice, with few affinities to South Tethys (Ethiopian province ), migrated during the Tithonian. Following taxa are reported for the first time fromthe Tithonian strataNorth Iran: Zappalia cf. zapalensis, Paraulacosphinctes transitorios, P. seneoides.

there are Discontinuous outcrops of volcanic rocks in the northern regions of Maku. The volcanic rocks were metamorphosed in the green schist facies. These volcanic complex were bimodal and compose of acidic and basic lava and pyroclastic rocks. The lava of this unit covers the Cambrian and equivalent of Lashkarak rock units and is progressively covered by Devonian dolomitic units. The geochemical data of metabasic and metarhyolite rocks signify transitional to alkaline nature of the primary magma and they have a negative gradient of REE and LREE / HREE ratio of those rocks are high and enriched inHFS elements. Metarhyolite rocks are similar to the rift setting rhyolites (A1-Type). Geochemical data indicate that the studied rocks are due to fractional crystallization of basic magma with crustal contamination, and in particular, the studied rocks have a genetic relationship and originate from a commen magma. The magma of the studied rocks generated by 3-10 percent partial melting of an enriched garnet peridotitic mantle source in an intra-continental extensional rift setting. This tectonic setting is concordant with the known extensional rift setting governed on other parts of Iran during the early Paleozoic, primary stages of generation and development of the Paleotethys.

The kaolin occurrence in the Abolhasani-Zereshkouh area (south of Shahroud, northeast of Iran) is a product of alteration of Eocene andesitic rocks. With attention to mineralogical studies, kaolinite, quartz, chlorite, montmorillonite, illite, rutile, calcite, orthoclase, albite, vermiculite, palygorskite, jarosite, and hematite are the mineral assemblege of this alteration occurrence. Calculations of mass balance of elements with assuming Zr as monitor immobile element show that elements such as Si, Fe, Mg, Na, K, Ti, Cr, Ba, Be, Co, Cs, Rb, Sn, U, V, W, Ni and REE were partially depleted and elements such as Hf, Zn and Cd enriched during the kaolinitization processes of andesitic rocks. Other elements including Al, Ca, P, Mn, Ga, Nb, Sr, Ta, Th, Y, Cu, Pb and Tl were undergone both leaching and fixation processes. The mass decrease of Si, Fe, K, Rb, Cs and Ba reveals destruction of plagioclase and hornblende by highly acidic hydrothermal fluids. The presence of two abnormal decreasing and increasing trends for the elements Al, Ga, P, Nb, Ta, and Y can be attributed to the low pH of the altering fluids, the high water-to-rock ratio and the abundance of complexing legands.

The Abbasabad Eocene volcano-sedimentary belt in the east of Shahrood includes of basaltic-andesitic rocks and related pyroclastics along with interlayers of sedimentary rocks. The volcanic rocks include olivine basalt, trachybasalt, trachy andesybasalt, trachyandesite and andesite with various textures such as hyallomicrolitic porphyry, microlitic porphyry, glomeroporphyry, trachytic and sieve textures. The main minerals of the rocks are clinopyroxene and feldspar. Pyroxene composition ranges from diopside to augite and feldspar composition is in the ranges of orthoclase and oligoclase to bytownite. The 87Sr/86Sr(Initial) and 143Nd/144Nd(Initial) ratios of these rocks, taking into account the age of 40 Ma for them, range from 0. 7042 to 0. 7047 and 0. 5127 to 0. 5130 respectively. Also, the values of Ԑ Nd(0) and Ԑ Nd(t=40Ma) of them range between 2. 67 to 7. 72 and 3. 8 to 8. 8, respectively, indicate an enriched mantle source for them. Whole rock, isotopic and clinopyroxene chemistry indicate arc-related calc-alkaline-alkaline nature and basaltic composition of the parental magma originated from partial melting of an enriched OIB source in an extensional intra-arc setting. Geothermobarometry calculations on clinopyroxene indicate a temperature range of 1100-1150 Cº and pressures of 2-13 kb for crystallization of the magma.

climate change is known as one of the most important environmental crises which has made many problems. Considering the undeniable impact of humans in the production of greenhouse gasses, in this paper the situation of the climate change of Tehran is predicted by modeling three different scenarios, for the period of 2046 until 2065. Based on optimistic, pessimistic and neither pessimistic nor optimistic scenarios, the alterations of climate parameters are forecasted. It is concluded that the amount rainfall will decrease, while, the amount of temperature will go up. To do this research the software of LARS-WG is used for modeling the climate change. This software is a sample of Meteorological generating models which is useful for simulation of climate data for now or future in an area. Then, considering the significant role of fossil fuels in deteriorating this phenomenon and determining the proportion of the effects of different modes of transportation in generating carbon, the existing policies on reduction of burning fossil fuels is investigated. At the end, based on the necessity of cooperation of people in various aspects of formulation of policies including behavioral-social and technological-technical, some suggestions are proposed to decrease the production of carbon.

The Gol-e-Zard zinc-lead deposit is located in the Malayer-Isfahan belt of Sanandaj-Sirjan zone in northeast of Aligudarz, Lorestan province. Mineralization occurred as two different ore horizon within metamorphosed Jurassic shale and sandstone. Generally, two ore facieses were distinguished in the deposit: 1) vein-veinlet/stringer facies, and 2) bedded facies. Primary minerals of the ores involve pyrite, sphalerite, galena and chalcopyrite, and the secondary minerals include cerussite, smithsonite, azurite, malachite and goethite. The gangue minerals are quarts, chlorite, calcite and clay-mineral. In the stringer facies, chalcopyrite replaced mainly pyrite and other minerals indicating influx of a copper-rich hot fluid influx into a pyrite-rich ore called as zone-refining process. In the Gol-e-Zard deposit metal and mineralogical zonation was observed. Alteration zones have distinct pattern, silicic-carbonatic at core to chloritic at margins. Based on textures and structures, mineralogical, ore facies, alterations and geochemical characters, the zinc-lead mineralization in the Gol-e-Zard region is of Selwyn-type sedimentary-exhalative (SEDEX) deposits, deformed and metamorphosed by the Late Cimmerian and Laramid Orogenies at green schist facies.

The Mesozoic sequence in the Zagros Region (SW Iran) consists dominantly of carbonates especially dolomite that play the role of reservoir in many oil and gas fields of the region. To investigate the function of sedimentary and diagenetic processes in the formation of Triassic-Neocomian dolomites of the easthern High Zagros, this study focuses on petrography and geochemistry of the carbonates crop out in the Khaneh Kat anticline. Field and laboratory data led to the recognition of four different dolomitization models within the studied carbonates. The Lower-Middle Triassic and Upper Jurassic dolomites are medium to thick-bedded and composed of fine to medium-grained relatively ordered dolomite. The stoichiometric chemistries and heavier oxygen isotope ratios of these dolomites as well as the considerable presence of evaporites indicate the favorable conditions for the formation of early dolomite due to downward-percolating of concentrated evaporate brines (reflux model). The Upper Triassic dolomitic portion of the Zagros consists of medium to coarse-crystalline, massive-bedded dolomites with relatively light isotopic composition. Mineralogy and geochemistry of these dolomites indicate a high temperature origin as well as their relationship to diagenetic processes, including recrystallization in a deep-subsurface environment (burial model). In the Upper Jurassic portion of the succession, dolomites are. . .

In this study the Upper Cretaceous sediments in the Zagrous Basins Fars province, the Pyrgheib Section, for the purpose of Biostratighraphy and sea level change studies were investigated. These sediments with about 206 m thickness consist of Limestone, Shale, Marl and limy marl. The investigated foraminifera led to identification of 70 species of planktonic foraminifera that belong to 16genera. Based on planktonic foraminifera the Upper Cretaceous deposits were divided into 6 biozone which are cosmopolitan and respectively are: biozone1-Dicarinella concavata Interval Zone, Biozone2-Dicarinella asymetrica Total Range Zone, Biozone3-Globotruncanita elevata Partial range zone Biozone4-Globotruncana ventricosa Interval Zone, Biozone5-Radotruncana calcarata Interval zone. Biozone6-Globotruncanella havanensis Partial range zone, Biozone7-Globotruncana aegyptiaca Interval zone. Biozone8-Gansserina gansseri Interval zone, Biozone9-Contusotruncana contusa Interval Zone. The Upper Cretaceous sediments in the study area on the basis of Planktonic Foraminifera are of the Late middle Coniacian to theLate Maastrichtian ages. According to the Morphotype groups of planktonic foraminifera deeping the basin from the Coniacian to the Middle Santonian is seen. However, in the late Santonian shallowing the basin and again in the Early Campanian deeping the basin, in the Late Campanian and close to the Campanian-Maastrichtian boundary shallowing the basin and a sea regression is observed.

Yapal iron ore body is located in northwest of Sanandaj-Sirjan zone. A complex of Paleozoic metamorphed rocks including green schist, mica schist, chlorite schist with green schist facies degree, plus skarn and marble outcrop in this area. . Iron mineralization generally occurs as magnetite with the shapes of lentoid, veins, veinlets and dots in garnet schist and greenschist and near marble outcrop in area. Ore textures are observed as dispersed, stock, replacement and network like. The iron oxide grade varies between 30 to 60 percent. Iron element negatively correlates with sulfur and positively correlates with titanium, magnesium, manganese and the other main oxides. Based on the relation between cobalt and nickel, this ore body is located within hydrothermal-originated category. Some samples are located in the hydrothermal-volcanogenic boundary. Based on distribution patterns of rare earth elements, Yapal iron ore has more similarities with skarn type mineralizations. Geochemical evidences of magnetite and the variations of cobalt, nickel, silica and aluminum suggest the skarn origin for Yapal iron ore. That means the iron has been mobilized by the hot fluids originated by intrusive stocks and precipitated in contact of metamorphic and marble units.

Kazhdumi Formation strata in Anguran section (NW Bandar Abbas) are investigated and eight echinoid species belonging to eight genera have been identified. These species are: Tetragramma malbosii, Orthopsis ruppelli, Phyllobrissus aff. angustatus, Epiaster dartoni, Hemiaster sp., Pliotoxaster comanchei, Iraniaster douvillei, Coenholectypus planatus. Iraniaster douvillei that has already been reported from the Coniacian – Santonian beds of Lorestan Zone (West of Iran); is present in the Albian – Cenomanian strata of Anguran section. So; we can propose the new range of Middle Albian – Santonian for this species. Kazdumi Formation in the studied area has the age of Middle Albian to Early Cenomenian on the basis of foraminifers those accompany with echinoids. This formation conformably overlies the Dariyan Formation and disconfomably underlies the Gurpi Formation.

In this paper, the structural evolution of Bamu fault zone located in the Zagros folded belt zone is presented as an example of northeast-trending fault zone in the Zagros, using the kinematic and dynamic analysis of accompanied structures. Based on structural and paleostress analyzes two phases of shortening were determined as NE and NNE. In order to define the chronology of the deformation stages in the region, the relationship between fault structures and folds in the folded rock formations has been utilized. The result showed that the first compression stress trend in the area was NE that caused formation of the Bamu transverse Fault with left-lateral strike-slip mechanism and its accompanied structures. Since this stage of deformation has affected the Oligocene-early Miocene formations, more likely occurred at this time. During the next phase the shortening direction, due to change in the collision zone direction of the Arabian-central Iran in the Miocene-Pliocene, has changed to NNE which causes development of younger structures in the form of folding and reverse faulting in the fault zone. This shows that the NE-trending fault zones, like other major NW-faults, in Zagros affected by the change in the convergence of Zagros collision.

Alvand plutonic body is one of the largest intrusive plutons in northern part of Sanandaj-Sirjan zone which is located in south of Hamadan city. It is composed of porphyroid and leucocratic granitoids, basic intrusive rocks, and abundant enclaves in various sizes and in a variety of forms. Biotites of porphyroid monzogranite, diorite, felsic microgranular enclave, mafic microgranular enclave and surmicaceous enclaves are located in magnesian biotites and biotites of norites in phlogopite field. Orthopyroxenes of norite are clinoenstatite and orthopyroxenes of mafic microgranular enclaves are clinofrosilite. Based on the Ti-in-biotite thermometer, temperature of monzogranite porphyroid is 662 to 734 oC, norite is 688 to 776 oC, diorite is 598 to 724 oC, surmicaceous enclaves temperature is 662 to 687 oC, felsic microgranular enclaves is 694 to 712 oC and mafic microgranolar enclaves is 635 to 737 oC. the enclaves of the Alvand plutonic body and their host rocks are located in the field of calc-alkaline suite. Orthopyroxenes in the norite and mafic microgranular enclaves indicate that rocks of the Alvand intrusive complex are located in the field of high oxygen fugacity rocks. It is in accordance with calc-alkaline property of rocks and is consistent with the subduction-related tectono-magmatic environment.

In order to study the biostratigraphy of Sarvak and Ilam in wells A1 and A2 of Binak oilfield, B of Gachsaran oilfield, C of Aghajari oilfield and D of Rag-Sefid oilfield, numerous thin sections have been studied microscopically In the biostratigraphic study of 5 biozones in the Sarvak and Ilam formations, the following fields were introduced: 1-Oligostegina flood zone, 2-Nezzazata – Alveolinids assemblage zone, 3-Rudist debris zone, 4-Nezzazatinella – Dicyclina assemblage zone, 5-Rotalia skourensis – algae assemblage zone and Oligostegina food zone. Based on the study of age of Sarvak Formation from Late Albian to Turonian, and for Ilam Formation from Coniasian to Santonian. Based on the biostratigraphy correlation and thickness analysis of biozones introduced in the two studied formations, the depth of the Zagros basin from northwest to southeast decreases dramatically.

South Natanz Area is structurally located in the western part of the Central Iranian structural zone and central part of the Orumieh-Dokhtar magmatic belt at southwestern termination of the Qom-Zefreh Fault. Our structural data represents older generation of E-W to NW-SE thrust faults as Fasakhod Fault that juxtaposes Permian-Triassic (Jamal, Nayband and Shotori Formations) over younger rock units. Most of the thrust faults have been cross cut with younger generation of strike-slip fault system. These mainly post Eoene strike slip fault systems are structurally linke to Qom-Zefreh Fault zone. On the other hand, they developed as strike slip orders of the Qom-Zefreh Fault system in central part of the Orumieh-Dokhtar magmatic belt. Integration of the structural data set with stratigraphic unconformities observed in the south Natanz represet regional folding of the area during pre Early Cretaceous time. Subsequently, it has experienced regional extension as observed in the other parts of the central Iran during Early Cretaceous time. Major thrust faulting of the area has been occuered during post Late Createcous time. The final post Oligocene strike slip faulting related to the activation of the Qom-Zefreh fault has overprinted and cross cut older structural features.