نشریه علوم زمین
پیاپی 121 (پاییز 1400)

Accurate estimation of the rotary drilling rate of the rock can save time and cost on exploration operations of the geotechnical projects such as dams, tunnels, oil and gas wells and building stone mines. In this study, the rotary drilling rate in limestone is estimated based on brittleness indices. To achieve this goal, the values of rotary drilling rate, Uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) were determined in three exploratory wells drilled in limestone. Based on the data, the regression relationships of one, two and three variables between rotary drilling rate as a dependent parameter and brittleness indices as an independent parameter were developed. The results suggest that based on one- and two-variable regression relationships, rotary drilling rate can be estimated based on brittleness indices with relatively good accuracy. In addition, the results showed that the three-variable regression relationship was more accurate than the one- and two-variable in estimating the rotary drilling rate. Finally, the three-variable relationship presented in this study could be appropriate in the early stages of exploration operations for geotechnical projects in limestone, which saves time and money.

The Zagros suture zone is one of Key regions. Continent - Continent collision between Arabian plate and Iranian Block. This region is coincided by High Zagros and Zagros Simply Fold Zones in Western side and in other side is the Sanandaj- Sirjan Zone. The region of this research in situated in Northern part of suture zone. The Zagros suture is oriented parallel to the other collision Structures as passive and active margins of Neo- Tethys Basin and also to Magmatic Arc (Urmiyeh - Dokhtar Arc).The main Faults in this region which we can mention by name are Zagros Main Thrust Fault and Zagros Main Recent Fault, Which they are also parallel to others structures. This region of suture zone in highly deformed and structures as folds, faults and nappes are the evident of a long compression Tectonics. The aim of this research firstly is analysing of folds and secondly is calculation of shortening rate of crust in this part of collision Zone. Three structural section (Eslam Abad- e- Gharb - Mahidasht, Kamyaran and Gazorkhani) have been balanced and the rate of shortening which is obtained respectively is 6252m , 6530m and 2040m.

Zarrin Mafic dikes, which outcrop in the Western Yazd block, Central Iran, trending NW–SE, emplaced into the Zarrin granitoid. They are sub-alkaline gabbro; characterized by intergranular and mylonitic foliated texture. Geochemical data reveal the Zarrin mafic dikes are from the partial melting lithospheric mantle, a spinel-peridotitic source. Furthermore, they are characterized by 87Sr/86Sr ratio of (0.7044-0.7028) and 144Nd/143Nd ratio of (0.5123- 0.5122), that consistent with the derivation from a lithospheric mantle. Their primitive mantle normalized trace elemental patterns display enrichment in LILEs compared to HFSEs, and positive Rb, Ba, and U but negative Ta, Nb, Th, and Zr anomalies, carrying characteristics subduction-related magmatism and metasomatism by subduction-related fluids. The petrogenesis of the Zarrin mafic dikes are related to melting of the lithospheric mantle, and upwelling asthenospheric mantle in the extensional basin which was associated with the subduction.

In the present study, In order to study of the planktonic foraminiferal biostratigraphy of Qom Formation in north of Khoy city, West Azarbayjan province (Sanandaj-Sirjan fore-arc basin), stratigraphic section of Sagatlu was selected and sampled. Thickness of Sagatlu section 216 meters was measured. Lithology of this section contain shale, siltstone, conglomerate and sandstone. The lower boundary of these deposits is alluvium, and its upper boundary is hard limestone deposits of Qom Formation. Study of the planktonic foraminifera communities found in the mentioned section to identify 16 genera and 37 species of planktonic foraminifers. In this research, 4 biozone are included, Subbotina linaperta assemblage Zone, Paragloborotalia opima Highest-occurrence Zone, Ciperoella ciperoensis Partial-Range Zone, Globigerinoides italicus assemblage Zone were identified as being age equivalent to Priabonian-Burdigalian and comparable to world standard biozones..

Despite the undeniable contribution of small-scale and artisanal mines (ASMs) in the mining industry and small-scale enterprises (SMEs), no clear and comprehensive definition has been provided. Each country and governorate have defined this sector. However, ASMs are entirely different from large-scale mines (LSM). Therefore, collective decision making will not lead to successful results for this sector. A review of previous definitions provided by the various developing countries is a sign of disagreement over a single definition in the first part of the paper. Therefore, in the next section, the objectives of presenting a definition and its effects at different levels for different countries, especially developing countries (Africa, Asia, and Latin America), are examined. Then, the definitions to obtain the main criteria of a single definition were gathered. Apart from this, it should be noted that the presentation of a single definition also depends on internal criteria and inter-organizational interactions to achieve the most appropriate case. Therefore, in the last section, a multi-criteria definition consisting of four elements of mineral characteristics, amount of human resources, amount of investment, and an annual financial statement was presented.

Cenozoic acidic volcanic rocks at the south of Qezel Ozan River are located within the Western Alborz-Azarbaijan magmatic zone and northern part of the Iranian-Turkish Plateau. The Oligocene acidic lavas in north part of Zanjan show rhyolitic to dacitic composition.  Hyaloporphyritic to hyalomicrolithic porphyritic textures are the main texture in these rocks. They were erupted along the main faults in this area. Feldspars, biotites and hornblendes are the major phenocrysts which are embedded in a glass matrix or micro phenocrysts of felsic and mafic minerals. By Geochemical studies it is indicated that these rocks have high-K calc-alkaline to shoshonitic nature and classified as meta-aluminous and I-type acidic rocks. In the chondrite normalized rare earth elements diagram, these rocks demonstrate LREE enrichment and high LREE/HREE ratio. Enrichment in LREE and depletion in HREE is characteristic of the calc-alkaline rocks in active continental margins. Furthermore, these rocks show enrichment in LILEs and negative anomalies of HFSEs (Ti, Nb and Ta) which is the feature of magmatic rocks associated with Post-COLG subduction zones. The geochemical evidences suggest that the parental acidic magma is resulted from partial melting of lower crust as a result of pressure reduction during the local tension mechanism.

The Chomalu Polymetallic deposit is located in western part of Alborz magmatic belt (Alborz-Azarbaijan) and central part of Tarom-Hashtjin metallogenic province. Eocene volcanic settings in the Chomalu deposit consist of basic rocks (olivinebasalt), intermediate (andesite basalt, andesite to trachyandesite) and acidic rocks (dacite to rhyolite) which is intruded by quartz monzodiorite, monzosyenite and quartz monzonite intrusive rocks of Eocene. The main texture of volcanic rocks is more porphyritic. Olivine and plagioclase are the main phenocrysts in the olivinebasalt, andesite rocks compose of plagioclase and clinopyroxene and dacite to rhyolite consist of plagioclase, alkali feldspar and quartz. On the basis of AFM diagram, Chomalu volcanic rocks located in the high- K calc- alkaline to shoshonitic affinities in relation to subduction zone magmatism. Primitive mantle-normalized of volcanic rocks indicate that LILE enrichment and HFSE depletion in consistent with subduction zone magmatism. Chondrite-normalized REE patterns show LREE/HREE enrichment. Geochemical results suggesting primary source magmas source for volcanic rocks were generated by partial melting of the metasomatized lithospheric mantle-wedge in relation to subduction arc and were subsequently affected by both fractional crystallization and crustal contamination during magmatic evolution.

This study has focused on the result of seismic data. The first stage of basin formation is the opening of Neo- Tethys Sea which is Simultaneous with Dashtak, Kangan and Khaneh kat Formation and after that on the early to middle Triassic sediments an unconformity that can be named as an expansion of sedimentary basin in the upper Triassic happened. This stage of basin opening caused the formation of big faults and probably basement faults in the area that studying on this faults and their movements is the main goal of this study. The next stage of evolution of basin starts when the basin began to closure and still there is disagreement about the exact time; but the obvious thing is the four compressional events: first, from Cenomanian- Turonian up to Masstrichtian; second, Late Paleocene- Early Eocene; third, Late Oligocene-Miocene and the forth, Miocene up to Quaternary. All events caused to obduction of Ophiolite and sedimentation of Gurpi with partly erosion and Pabdeh with regional erosion, then disappearing formations such as Asmari and Gachsaran and at the end, the late Zagros orogenic phase which is the compression that is continues to this day.

Miocene siliciclastic sediments with 338m thick are studied in the southern Neka of Northern Alborz flank. Detailed sedimentology study allows recognition four facies associations consist of delta plain, distributary channel, delta front and pro-delta. Delta plain and tidal flat include heterolithic shale-silt-sand and limestone with fenestral fabric. Distributary channel and delta front associations consist of thin to thick channel shape sandstone, which display coarsening-thickening upward cycles with pro-delta/offshore association. Scares Ophiomorpha nodosa and Thalassinoides in these sandstones indicate a stressful condition such as sandy mobile substrate, turbidity and highly salinity fluctuation in the sedimentary environment. Shale-silty sediments of the pro-delta association with abundant framboidal and chamber filling pyrite and organic material display anoxic condition of the sedimentary substrate. Introducing Miocene hydrocarbon sediments in the neighboring region like Turkmenistan and Russia and sedimentary characteristics of the pro-delta/offshore shale of the studied succession allow us to introduce those as high potential candidate for hydrocarbon source.

The study area is located in the N Turood, S Shahrood, and NE of Central Iran structural zone. Many basaltic dikes in this area intruded into the Eocene volcanic rocks and they also contain many gabbroic enclaves. Plagioclase (labradorite, bytownite-anorthite), amphibole (calcic, pargasite- magnesiohastingsite), and pyroxene (calcic, diopside-augite) are the essential minerals of these rocks. With the attention of the minerals chemistry, magma forming of these rocks has mainly subalkaline nature and during their crystallization fugacity of oxygen has been high. Geothermometry of these rocks suggest crystallization equilibrium temperatures are at 1100-1200°C for pyroxenes, and 825-888°C for amphiboles. Geobarometry calculation by using of Altot of amphiboles in host basaltic rocks, basaltic dikes and enclaves estimated between 8.51 to 9.21 kbar (depth of 30 to 33 km), 7.41 to 9.16 kbar (depth of 27 to 33 km) and 6.84 to 7.46 kbar (depth of 25 to 27 km), respectively. The chemical characteristics of studied minerals in differents diagrams show strong compositional similarities and indicate that nature and origin of these rocks are the same and most likely the magmatic reservoir or reservoirs of the studied basaltic rocks were at depths of 33 to 25 km of the lower crust.

Identifying landslide-prone areas provides a basis for slope-stabilization and mitigation programs. In Hablehroud watershed, artificial neural network and fuzzy logic (FL) as one of the methods of multicriteria-decision analysis based on ArcGIS were used in the scientific evaluation of landslide-prone areas. For this purpose, MATLAB, IDRISI and ArcGIS software were used. After preparing landslide-susceptibility maps, the prone zones predicted by FL and multilayer perceptron artificial neural network (MLP-ANN) were compared with the Hablehroud landslide database (distribution map). The results indicate a good overlap between the prone zones predicted by the MLP-ANN and landslide field observations. Finally, the performance of different methods in generating landslide-susceptibility maps were compared to each other using the validation indicators of "quality-sum index (Qs)" and "receiver-operating-characteristic curve (ROC)" to specify the optimal and applicable method for the landslide risk management of the Hablehroud watershed. By analyzing the obtained zoning maps and considering the Qs and "area-under curve (AUC)" values of different FL operators and MLP-ANN for the landslide-susceptibility maps, it is observed that the Qs (1.6299) and AUC (0.806–very good) values of the MLP-ANN are higher than those calculated for the sensitivity maps by different FL operators.

In this research the biostratigraphy and lithostratigraphy of the Talou section (northwest Damghan) have been studied based on brachiopods of Lower Carboniferous in Mobarak Formation. The 580 me thick Mobarak Formation in Talou section consists of dark gray limestone with intercalation of organic rich black shale. This formation in the studied area is conformably overlie on Jeirud Formation. Vermiculate limestone of Elika Formation overlies the Mobarak Formation with an erosional surface. In the studied interval 25 genera and 30 species of brachiopods were identified. 4 assemblage zones have been identified in the early Carboniferous.Biozone 1 (Early Tournaisian): this zone is characterized by the following indicator species community. Spinocarinifera nigra, Rugosochonetes cf. hardrensis (Phillips,1841), Rossirhynchus adamantinus, Shumardella sp., Cleiothyridina transversa., Rossirhynchusadamantinus, Shumardella sp.; Biozone 2 (Middle Tournaisian): Spirifermissouriensis, Spirifer attenuatus (Sowerby,1839), Spirifer cf. trigonalis (Martin, 1809), Athyrishibernica Syringothyriscospidata; Biozone 3 (Late Tournaisian): Tomiproductus elegantulus, Marginatia aff. burlingtonensis (Hall,1893), Leptagonia cf. regularis, Fusellatornacensis, Marginatiaburlingtonensis; Biozone of 4 (Early- Middle Visean): Buxtonia cf. praejuresanensis, Marginatia cf. kinghirica, Cleiothyridina cf. okensis (Grunt,1980). therefore, the age of Mobarak Formation in the Talou section, is Tournaisian to Middle Visean. The sedimentary environment of Brachiopods of the Mobarak Formation are lagoon, bar or reef and fore-reef.

Anticline axes in both orogenic belts of the Zagros and Kopeh Dagh are offset by NW-SE trending transvers faults. These faults are rotating anticlockwise due to their oblique orientation relative to maximum stress vector, causing shortening across the belt and elongation along the strike. The transverse faults move right laterally and known as prominent faults of Bajgiran, Quchan, Shokranlou, Baghan in central Kopeh Dagh; and Kazerun, Karehbas, Sabzpushan, Sarvestan in central Zagros. Faults in two regions, however, show different pattern of offset. We proposed two different physical models, consist of rotating blocks at the base overlaid by sand with and without silicon layers, resembling variation of stratigraphy in two belts. In the Zagros model, where we have more incompetent layers, offset on the basement faults causes bending of the fold axes at the surface prior to any offset. While in the Kopeh Dagh, where we have less incompetent layers, the fold axes are offset with no major change in their orientation.

The sediments are generally limestone and marl. The lower boundary with the loer red Formation is disconfomity and the upper boundary with the equivalent formatin of Bakhtiari Firmation is paraconformity. The total number of fossils found in this section is 69 species, 72 genera and 46 families. These sediments are formed in an open shelf and under the open sea and lagon environment. The variety and abundance of bentic foraminifer’s forms and the low presence of plagic forms testify to the shallow basin in this section, which is also confirmed by the study of other fossils. One of the Markable features of this section is the presence of Ammonia species, especially Ammonia parkinsonia. This section has a complete sequence of members of Qom Formation. This species are profe of shallow water and continental shelf for this carbonates. This section consist all of members of Qom Formation and based on identified foraminifera comparable to assemblage zone 1 & 2 introduced by Adams & Bourgeois (1967). These zones that inclod: 1-Borealis Melo Group- Meandropsin; 2- Miogypsinoides- Archaias- Valvulinid. Based on index foraminifer's species and their stratigraphic distribution the age of this section is Chatian- Burdigalian (Upper Oligocene-Lower Miocene)