استخراج خطواره‌ها با استفاده از داده‌هاي ماهواره لندست 8 در پهنه برشي سقز- بانه با تأكيدي بر كانه‌زايي طلا

Lineament extraction using lansat-8 satellite data in the Saqqez-Baneh shear zone with emphasis on gold mineralization

منطقه مورد مطالعه در جنوب‌غرب سقز و بخشي از زون ساختاري سنندج- سيرجان است. اين منطقه شامل تعدادي محدوده‌ي كانه‌‌زايي طلا به اسامي قلقله، قبغلوجه، كرويان، حمزه قرنين، قره‌چر و كسنزان است. هدف از انجام اين پژوهش، بررسي راستاي گسل‌ها و ارتباط آن‌ها با مناطق كانه‌زايي به عنوان معياري براي اكتشافات آتي است. در اين پژوهش با استفاده از تصاوير ماهواره‌اي لندست 8، گسل‌هاي منطقه با سه روش دستي، اتوماتيك و نيمه اتوماتيك استخراج گرديد. در استخراج خطواره‌ها به صورت دستي از چهار روش رايج عمليات فيلتر، مؤلفه‌‌هاي اصلي، نسبت باندي و تركيب رنگي استفاده شد، و با استفاده از نتايج حاصل از چهار روش، يك نقشه خطواره تهيه شد. در استخراج خطواره‌ها به صورت اتوماتيك، از الگوريتم رايج Hough transform استفاده شد. در بررسي حاضر، از باند 4 ماهواره لندست 8 كه در اين باند عوارض زمين‌شناسي مانند انواع سنگ‌ها، مواد معدني، پوشش گياهي و غيره قابل تشخيص است، استفاده شد. در روش نيمه اتوماتيك پس از استخراج خطواره‌ها به روش اتوماتيك، خطواره‌هاي مرتبط به عوارض مورفولوژيكي يا انساني به صورت دستي حذف شده و بعضي عارضه‌هاي خطي اضافه شد. نتايج اين پژوهش نشان مي‌دهد كه سه راستاي گسلي در منطقه مورد مطالعه شناسايي شد. راستاي غالب گسل‌ها، شمال‌شرق-جنوب‌غرب است كه بخشي از سنگ‌هاي ميزبان كانه‌زايي طلا را در بر مي‌گيرد. دومين راستا، راستاي شمال‌غرب-جنوب‌شرق است كه به موازات راستاي غالب زاگرس است و شامل گسل‌هاي راندگي اصلي در منطقه است. سومين راستا، شرقي-غربي است و بخشي از كانه‌زايي طلا و رخداد دگرشكلي شكنا تا شكل‌پذير را شامل مي‌شود.

IntroductionThe purpose of this study is to apply remote sensing technique to extract lineaments in the Saqqez-Baneh shear zone. In this study, lineaments were extracted in three manual, automatic and semi-automatic methods and their density and direction as well as their relationship with gold mineralization were investigated.Materials and methodsIn this study, the extraction of the lineaments was performed in two methods, manual and automatic. Then, on the basis that the semiautomatic method has a better advantage than the other two methods, in this research, after extracting the lineaments automatically, the lineaments related to the morphological or human features are removed manually and some lineament are added based on our investigation. In this study, Landsat 8 satellite images, taken on 16/8/2016 in 168 pass and 35 row, were used. Various software including PCI Geomatica (version 2015), Envi (version 4.8), Arc GIS (version 10.3.1) and (rock version 16) were used during this study. Principal component analysis was performed by Envi software and its output image was imported into PCI Geomatica software for extraction of lineaments. Then extracted lineaments were investigated in Arc GIS software and finally the density and direction of the lineaments were plotted by Rock Work software.Results and discussionIn this study, three methods were used to evaluate the extracted lineaments. (1) Lineament density analysis, (2) lineament length analysis, and (3) lineament orientation analysis. The density of lineaments is mostly concentrated in the center of the study area and in the north, west and southwest of Baneh. The density of faults is higher in the center of the study area and in the north, west and southwest Baneh city. Fault, causes pass ways for hydrothermal fluid, which is one of the effective factors in mineralization. The highest densities of lineaments coincide in the south, west, and northwest of the region, which include dextral faults. The rose diagrams show that there are three directions in the study area. The dominant fault zone is northeast-southwest, which include parts of the host rocks of gold mineralization. These shear zones comprise a range of ductile to brittle structures that are generally reverse and also are the longest lineaments. These faults usually displace Precambrian on Paleozoic units in southwest Saqqez, and are an indicator for subsequent local-scale exploration, especially in the intersections of the EW fault systems with NW-SE directions. Most of the gold mineralization in southwestern Saqqez (eg Qolqoleh, Kervian, Qabaghlojeh and Kasnazan) is related to this fault system. The second is the northwest-southeast direction, which is parallel to the prevailing trend of Zagros fault and contains major thrust faults in the area, which cause older rocks to over thrust on younger formations. The third is the east-west direction, which includes part of the gold mineralization and the occurrence of a brittle to ductile deformation.ConclusionThe results of this study indicate that by using semi-automatic method, faults in this area can be extracted with appropriate accuracy. Fault densities are higher in the center of the study area and in the north, west and southwest of Baneh city, and cause pass ways for hydrothermal fluids, which is one of the effective factors in mineralization. The highest densities of lineaments coincide in the south, west, and northwest of the region, which include dextral thrust, which cause older rocks to over thrust on younger formations. Three major faults were identified in the area. The fault direction and its relation to mineralization have been studied and the results show that the most dominant fault is northeast-southwest which comprises part of the host rocks of gold mineralization. The second, northwest-southeast direction contains thrusts and revers faults parallel to prevailing trends of Zagros fault, and the third is the east-west direction that contains .part of the gold mineralization