نشریه علوم زمین
پیاپی 131 (بهار 1403)

Middle Devonian to Lower Carboniferous siliciclastic-carbonate successions in Eastern Alborz are characterized by Khoshyeilagh Formation. It is underlain by the Devonian red siliciclastic sequences and is overlain by the Carboniferous Mobarak Formation, can be divided into three different members; lower carbonate, middle siliciclastic, and upper carbonate. The Khoshyeilagh Formation comprises various fossil groups of invertebrates, conodonts, palynomorphs and fish remains. In the present study, a collection of microscopic fish remains, obtained from the lower and upper carbonate members in Mighan, north of Shahrood, have been determined and described. This assemblage contains 14 different taxa of chondrichthyan fish including: Cladodoides cf. wildungensis, Ctenacanthiformis gen. et sp. indet, Dalmehodus turnerae, Deihim mansureae, Lissodus lusavorichi, Phoebodus aff. turnerae, Phoebodus fastigatus, Phoebodus gothicus gothicus, Phoebodus gothicus transistans, Roongodus phijani, Siberiodus mirabilis, Squatinactis glabrum, Stethacanthus resistens and Thrinacodus ferox. Some specimens of scales and teeth of actinopterygian and osteichthyan fishes are also present which all indicate a shallow environment of the continental shelf. The associated conodonts with this assemblage demonstrate the age of Frasnian (rhenana biozone) to early Tournaisian (duplicata biozone) for the whole succession.

Numerous Proboscidean footprints have been discovered in the outcrop (135 m) of lower rock unit of the Upper Red Formation (Middle-Late Miocene) in the north Avaj (Qazvin province), central Iran. These footprints are preserved as circular concave epi-relief in the upper bedding planes with smooth or levee rims or with sediment accumulation in the front of the footprints. Five digit imprints present in some of the footprints. The frequency of footprints is considerable the most of the upper surface of layers which was resulted by movement of proboscis herds. Ichnotaxonomically these footprints identified as Proboscipedaen igmatica. The footprints are classified as two sizes as small (15 cm) and large (25 cm) categories, and based on the geometric relationships, the height of shoulder was estimated as 140-170 cm for adult and 76-106 cm immature individuals. According to reports of Miocene Proboscidean body fossils from Iran, and based on the distributions of the Proboscidean in this time, it seems that the Choerolophodon (Gomphotheriidae) is candidate as track-maker of the Avaj footprints. Among the Proboscidean footprints, there are crocodile and fish swimming imprints which were left in the shallow pools.

The geochemical separation pattern and environmental behavior of rare earth elements (ΣREE) have been investigated in 5 different sedimentary systems related to the Dar-e-Allo copper mine. For this purpose, the total concentration and sequential patterns of ΣREE elements were determined using multi-acid digestion and mBCR (Modified Community Bureau of Reference, European Commission) selective extraction method. The normalization patterns of the total concentration of ΣREE are drawn based on the average North American Shale Composition (NASC) and Upper Continental Crust (UCC). General trends of concentration changes in the five sedimentary systems are very similar to each other, and the concentration of LREEs is higher than that HREEs, just a sample taken from under the rock dump that contains sulfide-leached elements shows a pattern different from other samples and standard patterns. Opposite of the changes in the concentration of ΣREEs, more enrichment is seen in HREEs compared to LREEs. This pattern of enrichment changes is consistent with the higher tendency of HREEs than LREEs for mobility during weathering and oxidation. The geochemical separation patterns of ΣREEs in natural sediment and samples containing iron and manganese oxides are mainly dominated by the residual fraction. Surprisingly, considering the different conditions of formation and stability in the samples taken from the waterways leading to the mine, evaporite deposits and sediments washed from the rock dump, the separation pattern of ΣREEs is controlled mainly with two parts soluble in Acid and reducible fraction. According to the enrichment trends, the trend of mobility and bioavailability from LREEs to HREEs increases with an upward slope. These results show that speciation, geochemical separation pattern and environmental behavior for ΣREEs without considering key environmental factors lead to a lack of understanding or even misinterpretation. The results of this study can be used as a reference in organizing the mine development and environmental planning of the Dar-e-Allo copper mine.

The Haji-Abad-Esfandagheh-Faryab ophiolitic belt is one of the most famous chromite-bearing occurrences in the south of Iran that has received considerable attention. Golashkard ultramafic unit includes dunite, highly serpentinized harzburgites, chromitite and wehrlite layers in the Faryab ophiolitic complex located in the southeast of Sanandaj-Sirjan as one of the chromite-bearing areas of the Haji-Abad-Esfandagheh-Faryab ophiolitic belt. Ultramafic rocks and chromitites of Golashkard area consist of 20 to more than 50% of chromite. The studied chromites have variable massive, banded and scattered textures. The geochemistry of Golashkard ultramafic rocks shows that the average Cr# enrichment of chromite in serpentinite rocks (probably dunite and harzburgite) and wehrlite is to Cr/ (Cr + Al) ×100= 70-80 and in chromitite is relatively higher (Cr/ (Cr + Al) ×100= 81). Based on the lithological and mineral chemistry characteristics, Golashkard ultramafic rocks are part of mantle related to ophiolite, which was produced by a homogeneous boninitic melt in the suprasubduction zone and formed high chromium chromitites and related peridotites.

Iju porphyry deposit is associated with the emplacement of Miocene tonalite-granodiorite intrusions (zircon U/Pb dating; 9.27±0.50) within Eocene volcanic and pyroclastic sequences including andesite, basaltic andesite, trachyandesite, andesitic breccias, tuffaceous breccias, and agglomerate. In this study, occurrence and chemistry of magnetites in the potassic alteration of Iju deposit were assessed using EMPA analysis. The findings imply for a limited occurrence of magnetite as fine-grained disseminated and/or product of biotite chloritization. Magnetites associated with potassic alteration of Iju deposit don’t show hematite intergrowth (as martitizied margin) and anhydrite paragenesis, indicating the lack of high oxygen fugacity (near magnetite-hematite buffers; ~ΔFMQ+4) during the magnetite crystallization in the potassic alteration. Studied magnetites are high temperature (>500 °C) and according to the Mg + Al + Si contents crystallized under low rate of fluid rock interaction. These evidences accompanied with the absence of reequilibration processes could imply for the lack of repeated stages of hydrothermal fluid exsolving during the evolution of potassic alteration in the in the Iju deposit. Additionally, results represent that there are considerable values of Ga (average; 0.015 wt. %) in the studied magnetites providing insights into the presence of unseen exploration potentials associated with porphyry Cu deposits of UDMB.

In this research, the leaching of REEs from the tailing of the apatite-iron ore processing unit of Morvarid mine (NW Iran), has been investigated using nitric, hydrochloric and sulfuric acids. This tailing contains rare earth elements (REEs) specifically Ce, La, Nd, Y and its accompanying minerals are magnetite, apatite, monazite, hematite, quartz. The appropriate dimensions for apatite release are 80-75μm. Leaching tests were performed for all three acids, and digestion process was also used for sulfuric acid. The leaching in the presence of sulfuric acid, under a temperature of 90°C, an acid concentration of 40% and a time of 60 minutes, leads to the total recovery of REE equal to 40.23%, and in acid sulfuric acid digestion at 200°C, equal to 61.21%. became. The recovery of REE when using hydrochloric acid at 72.64°C, concentration of hydrochloric acid 36.21% and time 56.28 minutes, was equal to 60.57%. In the presence of nitric acid, under the optimal conditions of temperature 61.51°C, acid concentration 40% and time 72.92 minutes. Furthermore, the maximum recovery of total REE equal to 51.9% was obtained. Due to the higher recovery and the lower price of sulfuric acid, this method is suggested for extracting for the extraction of REEs from the tailings.

Population growth and increasing urbanization expose city dwellers to higher degrees of urban pollutants, especially when they spend long time in enclosed environments with inadequate ventilation. This study is the first research on inorganic pollutants in indoor dust particles of Tehran city, which applies geochemical indices to estimate the intensity of dust pollution by potentially harmful elements. A number of 31 indoor dust samples were passively collected from inside the residential and office buildings in the central and densely populated districts of the city and were analyzed by ICP-Ms at the Universitat Rovira i Virgili, Tarragona, Spain. Single geochemical indices of the Contamination Factor, Geoaccumulation Index, Enrichment Factor, and cumulative indices of Pollution Load and Potential Ecological Risk Indices were calculated. The results of elemental analysis showed that the concentration of arsenic, cadmium, copper, mercury, lead and zinc in Tehran indoor dust is higher than that in some cities in the world. On the other hand, cobalt, chromium, nickel and vanadium present low concentrations in the analyzed indoor dust samples. This result was confirmed by the cumulative indices as well as the contamination factor. In contrast, some other factors showed a low to medium degree of pollution for the above-mentioned elements. Based on the obtained concentration of elements in the dust samples, it can be argued that the geochemical indices indicating low to moderate pollution are not applicable and trustable in the current study.

The central Alborz structural-sedimentary area in the middle part of the Alborz Mountain Range has endured geological events from the Precambrian to the present era, and contains numerous geological structures and formations. Among these, sandstone formations also have a significant expansion. In this research, 6 different sandstone formations were sampled in 2 locations and tested to determine their physical and mechanical characteristics. In general, in the sandstone formations of central Alborz, top quartzite has stronger mechanical parameters than other formations. Shemshak Formation has the lowest mechanical parameters among the selected formations. Based on regression analysis, the conversion factor of PLT, BST and CPI parameters to unconfined resistance or UCS showed 20.6, 6 and 20.40 respectively with R2s of 0.75, 0.90 and 0.78. In terms of the Cerchar Abrasivity Index (CAI) as an index that can show the amount of abrasion, top quartzite has the most abrasiveness, which is due to its lithological composition. This sandstone formation is placed in the category of stones with high abrasive ability, and Shemshak Formation has the lowest Cerchar index among the formations and is placed in the group of stones with extremely low abrasiveness.