Iranian Journal of Geology
Year:2020 | Volume:14 | Issue:53|Papers Count:8

Touyeh-Darvar granitoid pluton is situated in the south of eastern Alborz zone (45Km SW of Damghan in Semnan province). This pluton has intruded into the late Paleozoic formations (including Barut and Lalun). Based on the field observations and petrographic studies, the pluton is composed of monzonites, quartz monzonite and monzodiorite. In terms of mineralogy, the Touyeh-Darvar granitoid consists of plagioclase, orthoclase, quartz, ± hornblende and ± biotite. Accessory minerals consists of ilmenite, magnetite, zircon, apatite, titanite and pyrite. Sericite, epidote, calcite, and chlorite are considered as secondary phases. The iron-rich biotite is the most significant mafic mineral which are situated in the alkaline and anorogenic biotite fields. The total Al content of biotite in granitic rocks can be a useful indicator for distinguishing between mineralized and non-mineralized granitic rocks. The presence of mineral veins from oxides and hydroxides of iron and manganese, fluorite, barite, lead and zinc in the host rock of this pluton also confirms that the biotite composition is useful for mineralization potential study of this pluton. Applying the thermometry based on the Ti content of biotite and barometery based on total Al content of biotite resulted in calculating temperature ranges of 650– 730° C and pressures lower than 1Kb for stopping the exchange and final equilibrium of this mineral in the pluton.

Morphotectonic analysis with the help of geomorphic indices is considered as a tool for the identification of new and active structures affected by tectonic movements in special areas. For this purpose, indicators such as Mountain Front Sinuosity index (Smf), (Vf), (Af), (S), (Sl), (T), form factor basin, basin shape, slenderness ratio and stretch ratio index of basin (Bs) associated with alluvial fans, including fan of bending β , fanning coefficient and longitudinal profile were calculated. The tools in this study include: the topographic maps, field geology invesigations, satellite imagery, digital elevation model (DEM), IRS satellite images of the region, GIS and Global mapper softwares. The results of the analysis of topographic data, evidences from field observations and data obtained from geomorphic indicators, all suggested that the area is active from neotectonics viewpoint. Based on the classification of LAT, the study area is classified in class 1, which indicates intense tectonic activity. Based on the results, the northern part of the Dorud fault is more active than the southern section in terms of neotectonic movements.

Separation of alteration units has an important role in exploration of ore deposits. In the past, classical methods were used for this purpose. Recently, the support vector machine (SVM), one of the most important data driven models, has been applied for geological purpose. This algorithm is a useful learning system based on constrained optimization theory. In this study, the SVM algorithm with various kernels and maximum likelihood method were used to separate the alteration units of the Takht-e-Gonbad district situated in Chahar Gonbad sheet by using satellite images of the ASTER sensor. The results were analyzed and evaluated according to the field studies. Based on the achieved results and field studies, the SVM method with the RBF kernel function compared to other kernels and the maximum likelihood method had the highest accuracy (89. 17%) and kappa coefficient (0. 83). Thus, the SVM method for classification of alteration is more accurate compared to other discussed methods.

The kopet-Dagh zone undergone subsidence and deposition of sediments after middle Cimmerian orogeny in middle Jurassic to Eocene. Its shortening resulted from the Zagros orogeny in Paleogene. In order to identify the minerals at the detachments, XRD analysis was carried on the samples of Shemshak and Chamanbid Formations. On the other hand, the estimated shortening in the west and central Kopet-Dagh in two north-south cross-sections, were calculated in the 3D software of Move-Midland Valley, using previous data, field observation, geological maps and satellite images. The study of the three-dimensional cross sections, which is considered to be the innovations of this research, in the Move software has shown that most of the anticlines of the region are asymmetric due to the operation of detachment horizons. The results of the analyses indicate that the Shamshak Formation has more potential for developing detachment surfaces than the Chamanbide Formation. The reason for this detachment surface is due to thickness and mineralogy of the Shemshak Formation. On the other hand, by using geometric relationships, the depth of detachments was calculated for the main folds. In most of the detachments, this depth was calculated at lower levels of the Shemshak Formation.

In this study, the concentration-number fractal method was used for regional exploration studies, and determining the anomalies of copper, lead and zinc elements. For this purpose, 800 samples of stream sediments were selected from the rivers in the area (i. e. from Kahak and Aran geological maps, 1: 100, 000 sheets) and then the anomalies of these elements were mapped. The results show that strong copper anomalies are observed in the northern, central, southern and western parts of the area and the highest lead anomalies are located in the western part of the area. Strong anomalies of the zinc element are located in the central, southern and western parts of the region. These anomalies coincide with the lithological units of andesitic-basalt lava, volcanic breccia, tuffs, dacites, small scale masses of quartz-diorite, and small-scale masses of quartz-monzonite. The obtained map from combining anomalies and faults map reveals that the anomalies are mostly concentrated in fault zones and fault intersection points in the area and faults play a fundamental role in ore mineralization.

Since an annual share of 70 to 90 percent of the water resources are allocated to the agricultural sector, by using appropriate irrigation methods, it is possible to prevent hydrologic unbalance in addition to optimizing water consumption. The main aims of this study is to investigate the effect of two different irrigation methods on water table fluctuation. For this purpose, two laboratory models with a height of two meters and a cross sectional area of 4000 were established. After selecting the plant (Lettuce), flooding method was applied in the first model and a smart drip method was used for irrigation in the second. Smart drip irrigation was applied using a solenoid and a humidity gauge so that when the soil was in less than 30% saturation irrigation was started and automatically disconnected in more than 80% saturation. The water infiltration was monitored in the models by a humidity sensor and simulated using HYDRUS/2D. In a period of four-months, the level of groundwater in the dripping irrigation system model was 10 centimeter higher and water consumption was 68% lower. These results indicated that by replacing smart drip irrigation instead of flooding, products with the same quality could be gained by using less water, which would prevent lowering of the water table in the aquifer.

Garnet– mica schist and hornfels rock units are exposed in the east and southeast of Boroujerd. These rocks consist primarily of quartz, K-feldspar, plagioclase, garnet (almandine– spessartine), chlorite, cordierite, andalusite, sillimanite, biotite, muscovite, and minor amounts of apatite, iron oxides (ilmenite and magnetite), and zircon. Whole-rock geochemical analyses reveal that the dominant protoliths are pelitic rocks. Major and trace element compositions suggest that the Boroujerd pelites were deposited along an active continental margin. Garnet porphryblasts in some hornfels samples are compositionally homogeneous with respect to major, trace and rare earth elements; this is attributed to the diffusional re-equilibration at high temperatures (>600 º C). Garnet in schists and some hornfels samples show reverse compositional zoning with increasing Mn and decreasing Fe and Mg from core to rim. Higher concentrations of Mn in garnet rims are attributed to resorption during retrogression. The presence of chlorite around garnet porphryblasts in these schists also supports resorption during retrogression. In schists, concentrations of HREE and Y in garnet decrease from core to rim. These zoning patterns are interpreted to record garnet growth in a closed system (i. e., Rayleigh fractionation of compatible elements). Core– rim variations in the concentrations of trace elements and rare earth elements in garnet in the hornfels samples is negligible. The lack of prominent zoning of these elements in garnet from hornfels is interpreted as minimal fractionation due to rapid garnet growth.

The study area is geologically located in the northern area of the Sanandaj-Sirjan metamorphic zone. Based on petrographic study, the main minerals consists of plagioclase, pyroxene, amphibole and biotite and the accessory minerals are chlorite, muscovite, ilmenite and zircon. The obtained results from the mineral chemistry in this study indicate that the amphiboles are calcic amphiboles, and in terms of chemical composition they can be called pargasit, tschermakite and magnesiohomblende. Plagioclases are also andesian. Due to the low Na2O content, it can be concluded, that tectonically these amphiboles are of S-Amph type and are related to the subduction zones. Based on the high levels of Al2O3, the origin of amphiboles is mantle-type. Therefore, due to the ratio of Fetot (Fetot + Mg+2) to AlIv, which is less than 0. 6, the oxygen fugacity was high. On the other hand, the water levels vary from 2 to 2. 3 for hornblende crystallization. Different methods were used to perform thermobarometry, the best of which showed that the formation temperature of gabbroic mass has been in the range of 700° C (in average) and a pressure of 4. 45-7. 52 Kb. According to the estimated pressures, the magma was originated at a depth of 25-30 Km, which is near the Moho discontinuity.