شناسایی منشا و مسیر انتقال ماسه به محدوده تپه‎های ماسه‎ای دروازه‌قرآن یزد

بررسی و شناخت  ماسه‌های روان در مدیریت منابع طبیعی و  کنترل مخاطرات ناشی از آن‌ها، از اهمیت بالایی برخوردار است. هدف این پژوهش، بررسی ریگزار دروازه‌قرآن، در شمال شهر یزد است که به دلیل مجاورت با شهر یزد و استفاده ازآن‌جهت توسعه گردشگری، از اهمیت بالایی برخوردار است. در این پژوهش، به‌منظور منشایابی ماسه‌های روان، از داده‌های باد ایستگاه سینوپتیک یزد، طی یک دوره 20ساله (2001-2021)، نقشه‌های توپوگرافی 1:50000، نقشه‌های زمین‌شناسی 1:100000، تصاویر ماهواره‌ای tm سال 1993 ،etm+ سال 2008 و 2017 و مطالعات میدانی، جهت نمونه‌برداری استفاده شده است. روش تحقیق نیز بر اساس تحلیل ویژگی‌های باد (جهت و سرعت)، کانی‌شناسی دانه‌های رسوبی و استفاده از تصاویر ماهواره‌ای انجام شده است. نتایج حاصل از بررسی باد در منطقه موردمطالعه نشان داد که بادهای شدید در فصول خشک با امتداد شمال غربی، نقش مهمی در شکل‌گیری، توسعه و جابه‌جایی ماسه‌ها ایفا می‌کنند. بررسی کانی‌شناسی و آنالیز xrf حاکی از آن است که کانی‌های کوارتز و سپس کربنات‌ها با میانگین 45 و 33 درصد بیشترین فراوانی را در بین رسوبات منطقه موردمطالعه داشته و طبقه‌بندی مبتنی بر انعکاس طیفی تصاویر ماهواره‌ای ماسه‌های روان نشان داد که نسبت‌های باندی 4.5، 3.4 و 3.5 در تصاویر tm، می‌تواند در شناسایی کانی‌های مذکور استفاده شود. در نهایت نتایج نشان داد که دشت‌های آبرفتی و سیلابی، همراه با مخروط ‌افکنه‌های واقع در بخش شمال غربی و غرب محدوده این ریگزار، منشا اصلی تغذیه تپه‌های ماسه‌ای ریگ دروازه‌قرآن به شمار می‌آیند.

identification of the origin and route of sand transfer to the area of sand dunes of yazd darvazeh quran

investigating and understanding sand dunes is of great importance in the management of natural resources and the control of risks caused by them. the purpose of this research is to investigate the sand dunes of darvazeh quran, in the north of yazd city, which is of great importance due to its proximity to yazd city and its use for the development of tourism. in this research, in order to determine the origin of sand dunes, from the wind data of yazd synoptic station, during a period of 20 years (2001-2021), topographic maps 1:50000, geological maps 1:100000, tm satellite images of 1993, etm+ year 2008 and 2017 and field studies have been used for sampling. the research method is also based on the analysis of wind characteristics (direction and speed), the mineralogy of sedimentary grains, and the use of satellite images. the results of the wind survey in the studied area showed that strong winds in the dry seasons along the northwest play an important role in the formation, development, and movement of sand. mineralogical investigation and xrf analysis indicate that quartz minerals and then carbonates with an average of 45 and 33% are the most abundant among the sediments of the studied area and the classification based on spectral reflection of satellite images of loose sands showed that the band ratios are 4.5, 3.4 and 3.5 in tm images can be used to identify the mentioned minerals. finally, the results showed that the alluvial and flood plains, along with alluvial deposits located in the northwestern and western part of this reservoir, are the main sources of nutrition for the sandy dunes of darvazeh quran.extended abstract1-introductionsince the fight against wind erosion in dry land harvesting areas is more successful than the transport and sedimentation areas, in addition to being less expensive, so knowing the harvesting points or the origin of sand dunes is considered the most important and fundamental way to fight against wind erosion. sand dunes are scattered in all regions of the globe, from beaches and salty lakes to dry desert areas, and they occupy about 10 percent  of latitudes from 30 degrees north to 30 degrees south. based on this, knowing the amount of displacement, the way of transformation, and the effective factors in this displacement and their transformation is considered one of the most important pillars of the study in the field of this condition. the first studies on the movement of sand dunes were carried out by bagnold in 1941. regarding the origin of wind sands, he believed that wind energy cannot produce wind sand particles on a dense rock surface. 2-materials and methodsthe area of yazd darvazeh quran is part of the yazd-ardakan watershed basin in central iran, where yazd quran gate is located in the center of yazd province and in the northwest of yazd city. in this research, to investigate the origin of sand dunes from field studies and surveys, analysis of topographic (50,000) and geological (100,000) maps, wind data, mineral analysis of sand sediments taken from the surface of sand dunes, satellite images, and google earth images have been used. since the transfer of sand streams is carried out by wind currents carrying sands, it is of great importance to study and understand the prevailing wind regime in the areas dominated by sand streams. in order to study the prevailing wind regime in a region, different methods can be used such as wind rose and storm rose. because all winds are not able to erode and only strong winds have the ability to erode and transport wind-blown sands., therefore, in the case of wind erosion, wind speed is more important than its frequency. in order to identify the mineral deposits of yazd qur’an gate, 21 thin sections prepared from windy sands were analyzed by a polarizing microscope. considering that xrf is a non-destructive x-ray analysis method and provides comprehensive information about the chemical composition of samples, two composite samples were prepared from all 21 sand samples and analyzed in the laboratory through the xrf method. finally, for the purpose of the mineralogy of samples by remote sensing method, the band ratio of satellite images was done by envi software, and the mineralogy of sand dunes was analyzed by this software. in the following, in order to better analyze sand dunes in terms of identifying their origin and harvesting and feeding areas, and more importantly in terms of their changes and developments (displacement) over time, the etm+ images of the landsat satellite in 2017 were used. became. also, in order to improve the appearance of the image in order to increase the power of visual analysis and analysis, highlighting algorithms and applying filter commands and principal component analysis (pca) were used to increase the visual interpretation of images in the envi 5.3 environment. 3- results and discussionthe results of the analysis of the winds in the region showed that the winds, especially the strong winds of the dry season, play the main role in the formation, development, and movement of the sand sediments of sand dunes. based on the analysis of seasonal and annual mud storms, it can be stated that northwesterly winds play the main role in moving the sand sediments of the koran gate. the results of petrography and xrf analysis show a similar pattern in abundance. this issue shows the relative compatibility between petrographic laboratory studies and geochemical analyses using the xrf method. also, mineralogy using the method of remote sensing and processing of satellite images also showed that it is possible to recognize the areas covered with sand dunes with the dominant quartz mineral through their band ratios. therefore, according to the spectral reflection range of quartz minerals and carbonates, two spectral ratios of 4.5 and 2.7 were found suitable for the detection of sand dunes in the region. 4- conclusionthe mineralogical results of sand sediments and xrf analysis of sediments indicate that quartz minerals and then carbonates with an average of 45 and 33% were the most abundant among the sediments of the studied area. the classification results based on the spectral reflection of the satellite images of the sediments of the sand dunes in the study area showed that the band ratios of 4.5, 3.4, and 3.5 in the tm images clearly show the mentioned minerals. to give based on the final results obtained from the three methods used in this research, it was observed that the alluvial and flood plains along with the alluvial cones located in the northwest and west parts of this region are the origin of the sediments of the sand dunes in the region. has been studied.