نشریه کواترنری ایران
پیاپی 24 (زمستان 1399)

Damavand volcano is a large composite cone (≥ 400 km3) with height elevation (5678m) above sea level, in Central Alborz. This volcano consists of two buildings including old lavas between 1.8 to 0.8 Ma in the northern and eastern part of the current cone and young lavas with about 0.4 to 7 ka years in the south and west part. Trachytic and trachy-andesitic lavas are the most abundant lavas of this Quaternary volcano. The current Damavand cone, which is about 600,000 years old, is located above the old and eroded building which include periodically of andesitic-trachyte lava flows and pyroclastic flows with small eruptions of mafic lavas. Geological studies of this volcanic cone have been mostly based on geochemistry and petrogenesis, and a little data on mineral chemistry and termo-barometry are available. Geologically, the Damavand volcano bed rock has been formed since the Precambrian deposits, mainly on Mesozoic deposits (Shemshak and Lar Formations), and formed in the youngest geological period (Quaternary), about 10,000 years ago to the present. Late Cretaceous volcanic activity in Alborz is covered by shallow and progressive Eocene sediments in most places, but the Middle Eocene activity with Tofit composition is significant. The intensity of Alborz volcanic activity continues during Tertiary, but is not uniform, as its maximum is in the late Eocene and Oligocene, and after a period of relative inactivity, activity re-intensifies in the Pliocene.

After initial microscopic studies, suitable samples of thin section were prepared and sent to Iran Mineral Processing Research Center for analysis. The analysis performed in this center is performed by the electronic microprocessor model CAMECA-SX 100 made by the French company Cameca. This device is equipped with a spectrometer with an electron diode receiver and works automatically based on a high accuracy of 1% and the simultaneous operation of several diode detectors and electron beam stability with a carbon coating.

Volcanic activities in the middle part of the Central Alborz Mountain were started about 1.8 million years ago with the eruption of lava and pyroclastic rocks, which has caused the formation of the current Damavand cone, in the northern part of of Tehran. Damavand trachyandesites in Lar region have hyaloporphiric and microlitic porphiric texture with main phenocrysts include feldspar (oligoclase to labradorite), clinopyroxene and amphibole, and mica, apatite and opaque titanomagnetite to ilminite minerals. Mineral chemistry studies of clinopyroxenes show that these minerals with a percentage (Wo14-47, En0.1-47, Fs7-85) show the composition of diopside, which are in the range of calcium pyroxenes, magnesium-iron and alminodiopside. High Magnesium Number (80-79 = Mg #) of studied clinopyroxenes, shows that trachyandesites of Lar region generated from the low evolution and low-silica parent magma. The zonation of clinopyroxenes with Fe3 + fluctuations indicates the oxidant environment of the magmatic reservoir of these rocks, which is also confirmed by the high amounts of Fe3 + mica. Changes in the amounts of calcium and silica from the core to the rim of these minerals indicate crustal contamination of these rocks. The amphiboles composition is magnesium hostengite and mica show the composition of phlogopite. Phlogopites are characterized by Fe # <0.33, TiO2 6.03 - 7.7% and high Mg # number. Mineral chemistry studies indicate the sub-alkaline nature of the host magma. Thermo-barometric studies of clinopyroxenes show these minerals form at temperature range between 1112 to 1191 (± 50) ° C and pressure range of 6.2 to 6.9 kb, at depths of 20 to 22 km, with a water content of about 10%. Amphibole has a water content of about 4 to 7% and high oxygen fugacity range from -5.83 to -6.15. Thermal anomalies related to geothermal activity have been revealed based on remote sensing models that theoretically confirm the existence of hot zones containing melt at shallow depths. According to other researches, there is an unexposed igneous mass at a depth of about 22 to 35 km, which is somewhat consistent with the results of geophysical models based on a high-velocity P-wave mass at a depth of about 20 km below Damavand volcano (old cone area). Existence of non-equilibrium textures such as co-occurrence of aqueous and anhydrous minerals, reactive margins of phlogopites and amphiboles, non-equilibrium corrosion texture in feldspar, oscillatory and normal zoning and oscillation of iron oxides between the core to the rims of clino-pyroxene minerals indicate that Magmatic evolution of Lar lavas take place in an open system with different pressure, temperature, oxygen fugacity, and water content. Oxygen fugacity and water content of magma have increased during ascent to higher sections. Multiple magmatic chambers at different depths can be a justification for the local thickening of the crust under Damavand volcano.

The composition of phlogopites with Fe # <0.33, TiO2 6.3 to 7.7% and magnesium number (Mg #) is high and the formation temperature is 912 to 995. Mineral chemistry indicates the sub-alkaline nature of the host magma. Earth-temperature barometric studies of clinopyroxenes show that these minerals are formed in the temperature range of 1112 to 1191 (± 50) ° C and pressure of 6.2 to 6.9 kg, at depths of 20 to 22 km, with a water content of about 10%. Amphibole water content is about 4 to 7% and its fugacity is -5.83 to -6.15.

The vertical and horizontal movements of the Earth crust have caused extensive changes in surface phenomena, in the active tectonic regions. In order to measure some of these changes, morphometry analyses have been used to evaluation of the amount of tectonic activity. These analyses are useful tools for analyzing existing feature at the ground level and provide a proper understanding of the condition of drainage network, changes of mountain front and uplifting. The anticlines of the Zagros fold and thrust belt indicate some evidences of tectonic activity. The Ghalajeh anticlines is one of the folded structures in the Zagros fold and thrust belt. So, this study has focused on assessment of tectonic activity along the northeastern and southwestern of limbs of this anticline, using quantitative study and analytical hierarchy analysis of stream patterns. These analysis as an indicator of geomorphic systems can help us to understand the behavior of tectonically drainage basins.

In this study, Google Earth images, digital elevation model (DEM) and GIS software have been used for extraction of drainage network pattern and divide of the area around the Ghalajeh anticline into seven basins. Then, the streams of each basin were ordered and the order and length of each stream were measured. The indexes of hierarchical anomaly (Δa), drainage density (Dd), drainage frequency (Df), bifurcation ratio (R), bifurcation index (Rb), direct bifurcation ratio (Rbd), crescentness index (CI), precent of basin asymmetry (PAF), basin shape (BS), basin length to mean width ratio (Bl/Bmw), mean length of first order streams (LN1), Hinge spacing (Hs), Hypsometry integral (Hi), for each basins was calculated separately and the obtained results were analyzed in the Spss software.

The Zagros fold and thrust belt is the result of convergence between the Arabian plate and Iranian micro-continent due to closure of the Neotethys Ocean and subsequent continent continent collision. This belt is composed of long and asymmetrical anticlines with NW–SE trend and most of these folded structures indicate asymmetric geometry (the steepest limbs are on the southwestern limbs). The rate of tectonic activity is not same in all parts of the Zagros fold and thrust belt, and the uplift and shortening rate on each anticline is different. These mentioned changes caused differences in the amount of morphometric indexes as the indexes related to the drainage network. The study of drainage network pattern of the study area exhibits three types of drainage pattern along the Ghalajeh anticline. The first is the dendritic drainage pattern which are usually observed in wide or circular basins (basins1, 4, 6, 7).The second cluster is a parallel drainage pattern that is usually seen in long and narrow basins, such as the basins 5, 2. The third category of these drainage patterns is a parallel - trellis pattern that is integrated from the parallel drainage pattern and trellis (basin 4). The surface outcrop of the southwest limb of the anticline are the Gachsaran formation and the quaternary deposits and the Asmari-Shahbazan and Aghajari formations and quaternary deposits cover the surface outcrop of the northeast limb. Because of, existence of the evaporative rocks (salt and gyps) in the southwest limb, erosional basins (basins 6 and 7) have formed (sensitive to erosion and weathering) along this limb. But in the northeastern limb, most of the rock units are made of thick layer of limestone and resistant to erosion. Due to the deep drilling and erosion in the southwest of the limb, the number of stream order 1 decreases and the index values LN1 are reduced and consequently the index of DF is decreased. The minimum and maximum value of Hat index is 185 (basin 1) and 527 (basin 5) respectively. Result show an increase in Hat values suggest increase in the number of low order streams (order1) which is connected to the upper order (4 or 5). The maximum and minimum calculated values for Bs and Bl /Bmw indexes are in the basin 5 in southwest limb and basin 3 on the northeast limb respectively, showing the straight relationship between these two indexes. Also, calculated values for Hi index indicate medium tectonic activity and low tectonic activity of basins. The basin 4 contains the highest number of R and Rb indexes while the basin 6 contains the minimum value of the R, the basin 2 shows the lowest numeric value for the Rb index.

The results show that there is a strong positive correlation between Bs-Bl/Bmw indices as a result of a direct linear relationship with coefficient 0.93. Also, positive correlation between the R - Rb indices, resulting in a direct linear relationship with the 0.93 coefficient. There is a negative correlation between the R-DF indices and a strong negative correlation between the Δa-Hs indexes. It can be concluded that the southwestern limb of the Ghalajeh anticline is more active than the northeastern limb, according to the index values obtained for each basin and correlation between these indexes. The basin number 6 and 7 in the southwestern limb and basin number 1 in the north northeastern limb are affected by the intensive erosional processes resulting from tectonic activity.

Damavand volcano was formed by explosive and non-explosive eruptions on the old eroded rock units (Mesozoic and older) of Central Alborz during the Quaternary period and formed two huge cone (Old and Young Damavand).Davidson et al. (2004) determined the time of Old-Damavand activity from 1800 to 800 thousand years ago by measuring Ar/Ar and U-Th/He methods. According to their report, following subsidence of the Old Damavand cone, the Young Damavand cone has formed by continuing eruptions during 600 to 7.3 thousand years ago (Fig. 1).Several mechanisms have been proposed to explain Damavand volcano with subduction-like geochemical signatures including: 1) Subduction of Neo-Tethys crust under Iranian continental crust, 2) intracontinental rifting, 3) hot spot, and 4) lithospheric mantle delamination. To better understand the source and tectonic setting, and differences between several eruptions, we investigated field relations of major eruptive units of Damavand volcano, and carried out petrographic and whole-rock geochemical (including a wide range of trace elements) data for several key stratigraphic units. Based on these results, we present here a geodynamic model for post-collision volcanism during Quaternary time for northern Iran.

More than 500 non-weathered and unaltered samples were collected from multiple localities covering Damavand volcano to reconnoiter the variability of rock compositions over the major stratigraphic units. We collected 35 samples (~ 2 kg) for X-ray fluorescence (XRF) and ICP-MS analysis. Rock powders were analysed for loss on ignition (LOI) and major elements using X-Ray refractory fluorescence (XRF) at the Geological Survey of Iran laboratory. Following lithium metaborate fusion, the trace elements were analysed using ICP mass spectrometry (MS) analytical protocols at the Applied Research Center of the Geological Survey of Iran laboratory. Analyses of a selection of 35 representative samples from the different layers are presented in Table 1.

The Old- and Young-Damavand volcanic rocks are olivine basalt-trachyandesite and trachyandesite, respectively. Plagioclase and alkali feldspar phenocrysts with ferromagnesian mineral inclusions are common in young lavas that have not seen in the old rocks. The young specimens often have clinopyroxene phenocrysts with twining which have not observed in old ones. Orthopyroxene has been observed in some of the old rocks that had not been seen in young specimens.
Rocks from the Damavand volcano have SiO2 contents ranging from 46 to 67 wt% (Table 1). On the Zr/TiO2 versus Nb/Y diagram (Winchester and Floyd, 1977), the compositions of Old-Damavand rocks classify as alkali-basalt to trachyandesite, whereas the Young-Damavand rocks are trachyandesite. On the basis of the Peccerillo and Taylor (1976) classification, all rocks of Damavand volcano are assigned to the shoshonitic trend.Primitive mantle-normalized trace element variation diagrams (Sun and McDonough, 1989) further highlight the geochemical similarities between the Old- and Young-Damavand rock suites. All volcanic suites show spider diagrams with prominent enrichments in large ion lithophile elements (LILE), although the LIL/HFS ratios of 1800-800 ka volcanic rocks (exception of olivine basalts) are smaller than the younger suites. Old- and Young-Damavand rocks are all enriched in light REE relative to heavy REE and with a small positive Eu anomaly, in the chondrite normalized of rare earth elements pattern (Sun and McDonough, 1989). These are characteristic for enriched mantle sources and/or continental crustal contamination. As major elements, similar features in trace element abundance patterns for trachyandesitic rocks imply that they are derived from parental magmas which remained uniform through time, and which contaminated with crustal materials.Moreover, trace element chemical characteristics of Damavand trachyandesitic rocks resemble those of high-silica adakitic magmas (Defant and Drummond, 1990), specifically high Sr/Y and high (La/Yb)N.The geochemical characteristics of Damavand volcanic rocks, including high values ​​of LIL elements (e.g. Rb, Ba, K, Sr) and negative anomalies of Nb, Ta and Ti in primary mantle normalized spider diagrams, and the enrichment of LREE relative to HREE in the chondrite normalized of rare earth elements pattern are similar to subduction zones magmas. The high content of U and Pb elements is a feature of upper continental crust (Radnik and Gao, 2003), which are also found in Damavand adakite rocks.Because the average of Ba/Th and Pb/Ce ratioes in Old- and Young-Damavand adakitic rocks are 136.82 and 0.073, respectively and with low Ba/La, therefore, the these volcanic rocks were not formed in subduction zone, either by the melting of the oceanic crust sediments or metasomatized mantle. Obviously, the volcanic rocks of Damavand could not have originated from the melting of the lithospheric mantle about 20 million years after finishing of subduction.The comparative normalized spider diagrams and normalized REE distribution patterns show acceptable similarity between Damavand samples with upper-crust composition. Moreover, the lower crust has a more depleted composition relative to Damavand samples.
Investigation of Damavand tectonic setting based on Th versus K2O diagram (Ayuboglu et al., 2012), shows that they have formed in the layered lithosphere.Due to lithosphere delamination and local pressure reduction at this point of Alborz, the mantle had melted and formed the primary magma of Damavand. This new generated hot magma ascent through the lower crust and then emplace in the upper crust, where it assimilate crust rocks, mixed and contaminated with them. It seems the early olivine basaltic magma of Old-Damavand has passed rapidly through the crust with minimal contamination (Figure 12a), however, the Damavand trachyandesitic rocks (adakites) of stayed for a long time in crust and undergo higher contamination.

- According to field investigations and a newly established geochemistry, the lithology of Old- and Young-Damavand volcanic rocks are olivine basalt to trachyandesite and trachyandesite, respectively, with shushonite affinity, except the olivine basalts that are alkaline.
- All volcanic rocks have enrichment of LILE to HFSE and LREE to HREE in normalized multi element diagrams. Moreover, the Damavand volcanic rocks have negative anomalies in Th, Nb, Ce, Pr, Sm, Dy, Yb and positive anomalies in Ba, Eu, U, K, Pb, Sr, Zr, Y in multi elements diagrams. The amount of Sm to Lu elements in Old-Damavand rocks is closer to mantle values, while Young-Damavand rocks are more depleted.
- The olivine basalts- trachyandesitic rocks are formed by melting of enriched mantle. The trachyandesitic (Old-and Young-Damavand) adakitic affinities seem to have originated from a similar source of enriched mantle at different depths with different amounts of crust contamination, by locally pressure drop related to lithosphere delamination. The Young-Damavand volcanic rocks probably stopped longer in the upper crust than the older and undergo more contamination with the crust, so it resembled the composition of the upper crust.

The rather limited Neogene-Quaternary olivine basaltic lava flows are outcropped in the Dehaj-Javazm area, north of Share-Babak, in the NW of Dehaj-Sarduieh magmatic belt as a part of the Urumieh-Dokhtar magmatic assemblage (UDMA). The rocks contain significant amounts of plagioclase both as phenocrysts and microliths in the microlithic groundmass which play an important role in the reconstruction of magmatic processes. The goal of this research is to determine the three-dimensional shape, growth time, and nucleation rate of the plagioclase crystals by using the crystal size distribution (CSD) method to determine the evolution of the magma during cooling and crystallization. Moreover, the plagioclase crystals residence time is also calculated to achieve the temporal aspects of the analysis.
Method

Field studies carried out by sampling from each outcrop and finally 60 samples were collected. After thin sections preparation and using polarizing microscopes, detailed petrographic studies for quantitative analysis of crystal sizes of the samples were performed. This led to the separation of the four least altered samples as the representative of the study area. Due to the homogeneous texture of the rocks, one image was prepared for each sample as the characteristic texture of the whole thin section. Image processing was performed to separate plagioclase crystals in binary images using Adobe Photoshop CS6 software. Then, measurements, data processing and analyzes were performed using Image j, CSD Slice 5 spreadsheet and CSD Correction 1.40 programs.

The Neogene-Quaternary olivine basaltic rocks in the Dehaj-Javazm area contains phenocrysts of olivine, clinopyroxene, and rarely of plagioclase in a matrix of microlithic plagioclase. The main textures of the rocks are porphyry, glomeroporphyritic, and flow texture which are accompanied by disequilibrium features. Based on geochemical data, the composition of the rocks varies from basalt and trachytic basalt to tephrite/ basanite.The texture and size of crystalline phases in magmatic rocks preserve essential information about the conditions of crystallization processes. So, by studying the igneous rock textures with the crystal size dispersion (CSD) method, it is possible to realize the governing processes during magma crystallization. The number of crystals in a rock can indicate information on the nucleation and growth rate of the crystal. Therefore, the three-dimensional shape, growth time, and nucleation rate of plagioclase crystals were investigated in the studied rocks by using the CSD method. The length, width, area, angle, and location of the center of the crystals (coordinates of X and Y points) were measured by Image j software. Then, the CSDSlice 5 spreadsheet program was used to convert 2D data to 3D. Thus, the crystal dimensions were calculated based on the ratio of short, medium, and long axes (S: I: L). The shape of the crystals was determined in Zingg's diagram. In this diagram, the crystals based on the ratio of their short, medium, and long axes were divided into four categories of tabular, bladed, prolate (acicular), and spherical (equant). So, it was found that in the studied samples, plagioclase crystals are mainly bladed in shape.Eventually, using CSD Correction 1.40 software, the semi-logarithmic diagram of CSD was drawn for each sample. Using the amounts of slopes in each CSD plots, the residence time of the crystals for each sample was calculated based on the formula Tr= (-1/G*m) / 31536000. In this formula, Tr and m are calculated residence time (year) and crystal population trend line slope respectively; whereas G is crystal growth rate (mm/s). The G value is selected based on the proposed value for the basaltic magma with a cooling time of 3 years (G = 10-9 mm/s), while 31.536000 is the conversion factor from seconds to years.Studies show that plagioclase crystals in the CSD diagram have a non-linear trend with a distinct break in slope, which indicates two growth stages with different nucleation rates and cooling times for the crystals. The first stage is characterized by plagioclase phenocrysts with low amounts of nuclei and a gentle slope; whereas in the second stage, they developed as microlith with a high nucleation rate and steeper slope. The higher slope of the microlith population compared to the phenocryst ones shows that the microlith population underwent higher undercooling which might be happened in low depths and also in a shorter period of time. The nonlinear CSD trends represent two different rates of crystal growth. This may indicate the multi-stage crystallization of magma during its ascent, the textural coarsening process during the crystallization, the modification in the course of crystallization due to changing environment, and also magma degassing.The nucleation rate and cooling time for plagioclase crystals were determined from 9.65×10-9 to 12.46×10-9 and 1.00 to 2.33 years, respectively. This indicates short residence time of plagioclase crystals in the magma chamber, rapid cooling, and a high rate of cooling of plagioclase in a volcanic system.

The presented results generally support that the plagioclase crystals in the Neogene-Quaternary olivine basaltic rocks of Dehaj-Javazm are mainly bladed in shape and their calculated growth time indicates the high cooling rate and short residence time of magma in the magma chamber. The nonlinear CSD trend represents two different rates of crystal growth, which may indicate the multi-stage crystallization of magma during its ascent, textural coarsening process throughout the crystallization, the modification in the course of crystallization due to changing environment, and also magma degassing. The orientation of plagioclases in the rose diagrams show a flow texture developed due to the low viscosity of magma.

Earthquakes are one of the natural hazards that have caused many casualties and financial losses around the world. This is why earthquake risk analysis studies need to be conducted more seriously. Iran is located in one of the seismogenic regions of the world, the Himalayan-Alpine belt, which is subject to many earthquakes every year. The Arias intensity, as one of the important seismic parameters, helps in seismic hazard analysis, and can be used to estimate structural performance, slope stability, and liquefaction during an earthquake. The region under study is in Khoy area in the northwest, near the Iran-Turkey border. The geographical area covers 38.5°N, 43.5°E to 39°N, 45°E. The main features of the region are the presence of the major lakes of Van and Ercek in the west, and also the Iran-Turkey border in the middle of the map.Arias (1970) created an equation for measuring the intensity of an earthquake based on the time-integral of the of the square of the ground acceleration, which was later used by some researchers to evaluate the damage potential. Harp and Wilson (1995) found out that the Arias Intensity is reliably linked with the distribution of landslides caused by an earthquake. Later on, Kayen and Mitchell (1997) proposed a method for evaluating the soil liquefaction during an earthquake’s strike with the help of the Arias Intensity. In another work (Cabañas et al., 1997), a noticeable correlation was found between the Arias Intensity and MSK scale. It was also revealed that for certain structures, such as the ones found in villages and adobe and brick buildings, the damage could be linked to the Arias Intensity. More recently, Borja et al. (2002) used the Arias Intensity as a measure for comparing the results of two seismic response analyses. Additionally, for determining damage indexes, such as the value of destructiveness potential factor , where la is the Arias Intensity, and V0 is the amount of the zero crossings of the acceleration–time history, this parameter is used (Araya and Saragoni, 1984).

The Arias Intensity is one of the seismic parameters which is usually used in seismic hazard analysis to shed light on the potential damage earthquakes may cause. The Arias Intensity, as a scale of the shakings linked with an earthquake in terms of the amount of cumulative energy, is defined as an infinite set of single degree-of-freedom oscillators of unit weight with the frequency of zero to infinity (Elnashai and Sarno, 2004). This parameter correlates with the integral of the square of the module of ground acceleration over the time history of an earthquake. The Arias Intensity is a parameter which includes characteristics such as the domain and duration of ground motion for a wide range of recorded frequencies. Thus, compared to the parameters depending on the maximum value of ground motion, it is far more effective for evaluating earthquake impacts on engineering targets. In fact, evidence (Khademi, 2002; Mamseyedeh et al., 2021) supports that the Arias Intensity is to correlate proportionately with the damage caused by an earthquake, making it a reasonable choice when describing shakings capable of causing instability in structures, landslides (Chousianitis et al., 2014; Travasarou and Bray, 2003), and liquefaction (Kayen and Mitchell, 1997; Orense et al., 2015). 

The a and b values were calculated using the Gutenberg and Richter law (Gutenberg and Richter, 1956) in MapSeis software (Figure 3.). To complete the information about the regions seismic sources, the iso-potential maps shown in Figure 3 were used. As is seen in the figure, the a-b values of the center of the region of the study were higher. These higher values indicate more seismic activity in the area (Kanamori, 1981; Kanamori, 2013; Wyss, 1975; Wyss et al., 2001). On the other hand, the accumulation of energy in the areas with a low b value shows their potential for future earthquake events. Of course, along with the consideration of this variable, other variables such as a and λ, in addition to the seismotectonics of the region, must be observed to locate future earthquakes with minimized error (Jarahi, 2017). Observing Figure 2 and Figure 3, along with noting the location of seismic sources in the region, reveals that three areas (A, B, and C) are to be expected to be subject to future earthquake events. Altogether, the mentioned revelations prove that the region is  highly seismic. The information formed the basis for the analyses done by Ez-Frisk for further calculations. Figures 4 to 6 show the Arias Intensity iso-potential maps for probabilities of 20%, 10%, and 5%, respectively in 100 years.

The Arias Intensity map can be used as one of the most important indexes for measuring the destructiveness of an earthquake. In this study, for the three return periods of 475, 975, and 2475 years, the Arias Intensity was examined and analyzed. During the study, the main seismic sources of the region were identified and their seismic parameters were calculated. Three areas, marked A, B, and C, were introduced as the areas with potential for future earthquake events. In the Arias Intensity of the region, some specific points were noticed. In general, the further the area is from the seismic source, the less is the intensity of the earthquake there. Nevertheless, it is not always true. That is because another important parameter, known as shear wave velocity, can control this pattern or even reverse it. In various regions, such as the land surrounding the Shkriazy fault, this reverse pattern was detected and that displays the effect of shear wave velocity on the Arias Intensity distribution. Considering the history of liquefaction during earthquakes in this region, the results of the current study could serve as the basis for liquefaction and landslide studies conducted there. From among the three recommended areas, area B is adjacent to a relatively large sedimentary basin (northeast of Salmas), where the very low shear wave velocity makes it prone to liquefaction. Therefore, the potential for the occurrence of future earthquakes, on the one hand, and the conditions increasing the likelihood of liquefaction and resonance, on the other hand, make area B the most dangerous one in the region. Moreover, it is recommended that in the three areas discussed in this study, measures be taken for reinforcing and strengthening structures to prepare them for future earthquake events.

Some researchers defined environment pollution as any change in properties of the environment members in a way that makes not only natural performance and biological balance disordered but also jeopardizes the benefits and the life of living creatures directly and indirectly. For centuries, different heavy metals, whether anthropogenic or earth-made, have been releasing into water and soil resources through different natural processes and industrial activities. In fact, studying water pollution to heavy metals can provide a good way to improve the quality of water, decrease disease, and increase safety and health. One of the natural water polluting activities is the weathering and oxidation processes on ophiolite rocks of special regions. Controlling chemistry processes and water composition, like weathering and dissolution, ion exchange, and absorption-desorption processes, can have high importance.

After field study and making related maps, the samples from the region’s wells and springs were gathered through a field operation. Since the concentration-aqueous concentration of the elements is affected more by evaporation during the dry season, the samples were gathered at the end of September, the time before precipitation when dry summer is finished. Plastic containers with half-liter capacity were used for the samples. Before gathering, the containers were filled and emptied 3 times. After that, 10cc nitric acid was added to the samples for each liter; and then they were sent to Zar Azma Mineral Company for analysis of their heavy elements. Concentration total of 28 light and heavy elements were measured in the water samples by ICP-MS analysis.

Dendrogram diagram and Pearson correlation were applied to classify the samples based on intergroup similarities, to find the probable source of the elements, and to study the correlation among the elements. It can be seen that Cr has a rather high positive correlation (0.54) with Si indicating the fact that they both have the same source, from Si minerals. This table reveals that there is a high correlation between Ca, S, and Sr on one hand, and a high correlation between Cr and Si and somewhat with Mg, on the other hand. Moreover, there is a rather high positive correlation between Ni and P and somewhat between Ni and Mg. These correlations can prove the fact that the elements have the same source. According to ArcGIS maps, the most concentration of calcium, Sr, and S is recorded for zone 1 including Hezarkhani and Yadabad. Moreover, the lowest concentration of these three elements is recorded for Aliabad and Ch-pavleh. These elements are expected to be originated mostly from conglomerate and limestone deposits. It turns out that the second controlling factor of groundwater chemistry includes the weathering and dissolution of source rock of Cr, Mg, and Si. The same-value maps of sampling points have been classified based on the concentration of Cr, Si, and Mg, revealing that the points of highest and lowest concentration of these elements are geographically the same. This fact proves a high correlation and a similar source of these elements. Therefore it can be seen that the highest concentration of these elements is recorded for Ch-pavleh, while the lowest concentration for Aliabad and Gashour. Since chromium has a high positive correlation with Si, it can be concluded that chromium has a silicate source. Based on the geological map of the region, the important silicate source is peridotite. In fact, peridotites, as a representative of the ophiolite collection of the region, can be considered as the source of Cr entrance to the regional waters. Moreover, as these peridotites include ferromagnesian minerals, they are also regarded as the source of Mg entrance to regional waters. Therefore, peridotites are considered as the common source of Si, Cr, and somewhat Mg entrance to regional waters. The existence of Cr- spinel in the geochemistry of peridotite rocks in Ch-pavleh can also prove silicate and peridotite sources of Cr in the region water.

Pearson correlation among elements was calculated to recognize the elements with the most correlation. According to that, the elements with higher correlation are suggested to have the same source. Factor analysis revealed that controlling factors of water chemistry have the highest correlation with the elements which have the highest correlation. Dissolution and weathering of these elements’ source rock are considered the important factors. Besides, focusing on water-rock interaction, the most essential minerals participating in the actions with water were recognized. Same-value maps were applied to determine the source of the elements. Moreover, according to these maps, it is revealed that the elements with the highest correlation come from the same geographical setting.   Based on these stages, the important controlling factors of water chemistry were recognized as the following: weathering and dissolution of conglomerate deposits to the dissolution of gypsum as the common source of calcium, strontium, and sulfide, weathering and dissolution of peridotites, especially ferromagnesian ( as the common source of magnesium and nickel) and chrome-bearing spinel (a common source of chromium, cilice, and magnesium), dissolution of chalcedony, barite, and calcite as three minerals with the highest saturation index.