ارزیابی نقش تکتونیک در برونزد گنبدهای نمکی منطقه زاگرس

نوع مقاله: مقاله پژوهشی

نویسندگان

1 دانشگاه شهید باهنر کرمان

2 دانشجوی کارشناسی ارشد مخاطرات طبیعی دانشگاه شهید باهنر کرمان

چکیده

زون ساختاری زاگرس تعداد 123 گنبد‏ نمکی وجود دارد، وجود گسل‌های فراوان در این محدوده از ایران احتمال تاثیر و نقش این ساختار‌های تکتونیکی در رخنمون یافتن گنبد‌های نمکی را افزایش می‌دهد. در این تحقیق سعی بر آن شده است تا با استفاده از پردازش تصاویر ماهواره‌ای و تکنیک‌های GIS میزان تاثیر و نقش تکتونیک در بالاآمدگی و برونزد این ساختارهای ژئومورفولوژیکی منحصر به فرد بر روی سطح زمین، مورد مطالعه قرار گیرد. بدین منظور بر اساس تجزیه و تحلیل‌های سنجش‌از دور شامل اعمال فیلتر‌های جهت دار، استفاده از مدل سایه-برجسته و شواهد مورفولوژیکی و ریخت‌زمین‌ساختی نظیر ایجاد خمش و جابجایی در راستای چین‌ها، تعداد 34 خطواره گسلی در منطقه زاگرس شناسایی شد، که از این بین تعداد 14 گسل برای اولین بار مورد شناسایی قرار گرفت. برای تعیین ارتباط بین این ساختارهای تکتونیکی و برونزد گنبدهای نمکی از روش آماری به نام وزنهای نشانگر در محیط GIS استفاده شد. بطوری که با اعمال بافرهای مختلف در اطراف گسل‌ها و روی هم اندازی آن با لایه رستری موقعیت گنبدهای نمکی منطقه، ضرایب مربوطه محاسبه شد به طوری که برای فاصله هزار متری از امتداد گسل‌ها، ضریب C/s(C) بالاترین مقدار را به دست می‌دهد. در نتیجه بر مبنای روش وزن‌های نشانگر بیشترین ارتباط بین گنبدهای نمکی و گسل‌های منطقه در فاصله یک کیلومتری بدست می‌آید، این ارتباط هرچند ضعیفتر تا فاصله 9 کیلومتری نیز ادامه دارد. بنابراین می‌توان عامل تکتونیک را یکی از عوامل بسیار موثر و مهم در جایگیری و رخنمون یافتن گنبدهای نمکی بر روی سطح زمین قلمداد کرد.

کلیدواژه‌ها


عنوان مقاله [English]

Assessment the role of tectonics in the outcrops of the Zagros area salt domes

نویسندگان [English]

  • mohsen pourkhosravani 1
  • Ali Mehrabi 1
  • Amirtakin Mohebi 2
1 Assistant Professor, Department of Geography Shahid Bahonar University of Kerman. Kerman Iran
2 MA student of natural hazards, Department of Geography Shahid Bahonar University of Kerman. Kerman Iran
چکیده [English]

Extended Abstract
Introduction
The Zagros fold-thrust belt belongs to the part of the Alpine-Himalayan system, represented by the southern Zagros-Dinaride branch of the orogenic belt. This is an orogenic segment NW-SE trending to a distance of nearly 2000 km and structurally consists of many synclines and anticlines. However, as basement faults are hidden from view under the more recent sedimentary units scarcely reach the surface. As a consequence, the identification and study of basement faults has mostly relied on indirect information such as anomalies in topography. Within the Zagros fold-thrust belt, there are many pierced salt plugs that are known as Hormoz series. Hormoz Salt Basin includes many diapirs of Cambrian salt that have risen through the Permian to Recent sediments. The aim of this paper is identification of basement faults in the Zagros fold-thrust belt using interpretation of satellite images, and determination of relationship between basement faults and salt plugs of Hormoz series using Geographical Information System (GIS) techniques such as the weights of evidence modeling.
Methodology
In this research, we examined many techniques of remote sensing for the recognition of faults, and then we did field checking to determination of the accuracy of the work. Remotely sensed data, including Landsat Enhanced Thematic Mapper plus (ETM+) images, were used to obtain information on structural features and for deriving lineaments of the study area by production of color composite images and applying some filters, such as Laplacian and Sobel and also some directional filler. Usually, the basement faults are hidden by sedimentary cover, and their location is uncertain, but there is some evidence for identification of them, such as deflections in trends of fold axes, offset markers and alignments of salt diapirs. In the study area, most of the folds have a general east-west trend that some detachment folds are cut by basement faults. There are deflection in general trend of folds and have been classically interpreted as the effect on the cover of strike-slip movement along underlying basement trends. Some conceptual models for the evolution of the fold structures affected by basement faults, offered by Leturmy et al. that in this research are confirmed.
Results and discussion
In the studied area, 34 normal and strike slip faults were recognized. Some of these basement faults could have an important role for salt uplifting. Fault No.1 is strike-slip fault with 26o azimuth crosses Larak salt plug and Hormoz salt plug and caused deviation and sinistral displacement of east of Namak anticlinal axes. Based on this fault activity, some minor faults formed parallel to the major fault. Fault No. 2 the strike-slip fault with 129o azimuth caused a deviation of the Faraghon and Namak anticline axes. This fault crosses Darbast, Takhu, Kushk kuh-West, and Gahkum salt plugs. In some tectonics text, this fault is known as Oman line. Fault No.3 This fault is known as a Minab fault, the trend of the Minab anticline and the deviation of that axis can be considered as this fault's function. The fault has a 165o azimuth. However some of the mentioned basement faults, such as fault numbers 1, 9, 11, 13, 15, 16, 17, 18, 19, 23, 24, 26, 28 and 33 may already identified, but the influence of them on the salt diapirism in the Zagros region have not been discussed. Based on the result of weights of modeling method, there is positive spatial association between the Basement faults and the salt diapirs as indicated by the contrasts C. So, findings of this research to be consistent with the aim of the plan. The positive spatial relationship is statistically considerable within 1000 to 10000 m; so, following to the highest Studentised C, it is optimal within 1000 m.
Conclusion
The interpretation of satellite images based on remote sensing techniques such as shaded-relief images analysis, filtering, and deflections in trends of fold axes, shows that some structures have a character of regional photolineaments (especially NNW-SSE and NE-SW trending. Such structures were considered to be main fault systems of the study area. Finally, 34 basement faults have been identified that among them 14 faults are introduced as the first time. Also, there is a rectilinear pattern of salt diapir emplacements. These implicit lines of weakness are approximately indeed related to basement structural trends, based on weights of evidence method; pierced salt diapirs are associated spatially with basement faults within a distance of 1 km. Also among 123 detected salt diapirs in the region, forty-five of them, 36 percent, have a maximum relationship with basement faults. So, tectonic condition is an important factor in the exposure of salt diapirs in the study area.

کلیدواژه‌ها [English]

  • Tectonics
  • Salt domes
  • Remote Sensing
  • Weight of evidence
  • احمد زاده هروی، محمد.، هوشمندزاده، علی.، نبوی، محمدحسن 1369، مفاهیم جدیدی از چینه شناسی سازند هرمز و مسئله دیاپیریزم در گنبدهای نمکی جنوب ایران. مجموعه مقالات سمپوزیوم دیاپیریسم با نگرش ویژه به ایران، وزارت معادن و فلزات، جلد اول، ص 22-1.
  •  قربانی ارجنلی، موسی.،  قاسمی، محمدرضا 1394، نقش زمین‌ساخت گنبدهای نمکی در تحول حوضۀ رسوبی زاگرس (حدفاصل گسل کازرون و گسل میناب)، مجله علوم زمین خوارزمی، جلد ۱ شماره ۲ ص. ۲۱۷-۲۳۴
  • مطیعی، همایون 1374، زمین‏شناسی ایران: زمین‏شناسی نفت زاگرس-1. سازمان زمین‏شناسی کشور. 1009 ص.
  • مهشاد نیا، فاطمه 1381، استفاده از رهیافت دورسنجی در شناخت گسل های پنهان و دگرریختی های آنها در جنوب خاوری زاگرس. پایانامه کارشناسی ارشد، دانشگاه تربیت مدرس. 234 ص.
  • یساقی، علی.، داوودی، زهرا 1384، شناسایی گسله ها و پهنه های عرضی-برشی زیرسطحی و تحلیل اثر دگرریختی های آن ها بر کمربند چین خورده- رانده شده زاگرس در پهنه دزفول. مجله علوم دانشگاه تهران، جلد سی و دوم، شماره ۲.
  • Agard, P., Omrani, J., Jolivet, L., Whitechurch, H., Vrielynck, B., Spakman, W., Monie, P., Meyer, B. & Wortel, R., 2011, Zagros orogeny: a subduction dominated process, Geological Magazine, 148: 692–725.
  • Alavi, M., 2004, Regional stratigraphy of the Zagros fold-thrust belt of Iran and its proforeland evolution, American Journal of Science, 34 (1): 1-20.
  • Bahroudi, A. & Koyi, H. A., 2003, Effect of spatial distribution of Hormuz salt on deformation style in the Zagros fold and thrust belt: An analogue modeling approach, J. Geol. Soc., 160: 719–733.
  • Bonham-Carter, G. F., 1994, Geographic Information Systems for Geoscientists: Modelling with GIS, Pergamon Press, Oxford, 398 p.
  • Chowdari, S., Singh,  B., Rao, N., 2017, Structural mapping based on potential field and remote sensing data, South Rewa Gondwana Basin, India,  J. Earth Syst. Sci. 126(84): 57-68.
  • Dastanpour, M., Mehrabi, A., Derakhshani, R., Radfar, S. & Vaziri, M. R., 2012, Stratigraphy of Hormoz Formation in Gachin salt dome in Iran, Proceedings of the Annual International Conference on Geological & Earth Sciences, Singapore, 48-50.
  • Farhoudi, G., Faghih, A., Mosleh, H., Keshavarz, T., Heyhat, M. R. & Rahnama-Rad J., 2008, Using GIS/RS techniques to interpret different aspects of salt domes in southern Iran, Geophysical Research Abstracts, 10: 652-661.
  • Farzipour-Saein, A., Nilfouroushan, F. & Koyi, H., 2013, The effect of basement step/topography on the geometry of the Zagros fold and thrust belt (SW Iran): an analog modeling approach, International Journal of Earth Sciences, 102(8): 2117-2135.
  • Ghasemi-Rozveha, T., Khatiba, M., Yassaghib, A., Gholamia E., 2017, Using airborne geophysical data in identifying tectonic lineaments in east of Iran,  Geotectonics, 51(3): 331–339.
  • Jahani, S., Callot, J. P., Frizon de Lamotte, D., Letouzey, J. & Leturmy, P., 2007, The salt diapirs of the eastern Fars province (Zagros, Iran): A brief outline of their past and present, in Thrust Belt and Foreland Basin, edited by O. Lacombe et al., pp. 287 – 306, Springer, Berlin.
  • Jahani, S., Callot, J. P., Frizon de Lamotte & D., Letouzey, J., 2009, The eastern termination of the Zagros Fold-and-Thrust Belt, Iran: Structures, evolution, and relationships between salt domes, folding, and faulting, Tectonics, 28: TC6004.
  • Joudaki, M., Farzipour-Saein, A., Nilfouroushan, F. 2016, Kinematics and surface fracture pattern of the Anaran basement fault zone in NW of the Zagros fold-thrust belt. International Journal of Earth Sciences 105, 869–83.
  • Koyi, H. A., Nilfouroushan, F., Hessami, K. 2016, Modelling role of basement block rotation and strike-slip faulting on structural pattern in cover units of fold-and-thrust belts, Geological Magazine,153 (5): 827-844.
  • Koyi, H. A., Ghasemi, A., Hessami, K. & Dietl, C., 2008, The mechanical relationship between strike-slip faults and salt diapirs in the Zagros fold–thrust belt, Journal of the Geological Society, London, 165: 1031–1044.

·         Leturmy, P.,  Molinaro, M. &  Lamotte, D. F., 2010, Structure, timing and morphological signature of hidden reverse basement faults in the Fars Arc of the Zagros (Iran), Geological Society, London, Special Publications, 330: 121-138.

·         McQuarrie, N., 2004, Crustal scale geometry of the Zagros fold–thrust belt, Iran, Journal of Structural Geology, 26: 519–535.

  • Motamedi, H., Sepehr, M., Sherkati, S. & Pourkermani, M., 2011, Multi-phase hormoz salt diapirism in the southern zagros sw Iran, Journal of Petroleum Geology, 34(1): 29-43.
  • N.I.O.C. (National Iranian Oil Company), 1977, "Tectonic map of Iran", National Iranian Oil Company.
  • Nogol-e-Sadat M. A., Ahmadzadeh Heravi, M., Almasian, M., Poshtkouhi, M., Hushmandzadeh, A., 1993, Tectonic Map of Iran, Scale 1:1000000 Geological Survey of Iran.
  • Pirouz, M., Simpson, G., Bahroudi, A., Azhdari & A., 2011, Neogene sediments and modern depositional environments of the Zagros foreland basin system, Geological Magazine, 148: 838–53.
  • Player, R.A., 1969, The Hormuz Salt Domes of southern Iran, MS, PhD. Thesis, Reading University, 300 pp.
  • Poursoltani, R., Pourkermani, M., Yazdjerdi K., Almassian, M., 2016, Investigating the Impress of the Active Tectonics and the Rate of Fractures in Ilam Formation, Fars Area, SW Iran, Earth & Environmental Sciences, 6 (6): 498-515.
  • Rahnama-Rad, J., Derakhshani, R., Farhoudi, G. & Ghorbani, M., 2008, Basement Faults and Salt Plug Emplacement in the Arabian Platform in southern Iran, Journal of Applied Science, 8(18): 3235-3241.
  • Sabins, F. F., 2007, Remote Sensing Principles and Interpretation, Waveland Pr. Inc., New York, 512 p.
  • Sepehr, M. & Cosgrove, J. W., 2005, Role of the Kazerun Fault Zone in the formation and deformation of the Zagros Fold-Thrust Belt, Iran, Tectonics, 24(5): 1-13.
  • Sherkati, S.,  Molinaro, M., Lamotte, D. F. &  Letouzey, J., 2005, Detachment folding in the Central and Eastern Zagros fold-belt (Iran): salt mobility, multiple detachments and late basement control, Journal of Structural Geology, 27: 1680–1696.
  • Talebian, M. & Jackson, J. A, 2004, reappraisal of earthquake focal mechanisms and active shortening in the Zagros mountains of Iran, Geophysical Journal Inernational, 156: 506-526.
  • Waltham, T., 2008, Salt terrains of Iran, Geology Today, 24(5): 188-194.
  • Yassaghi, A., 2006, Integration of landsat imagery interpretation and geomagnetic data on verification of deep-seated transverse fault lineaments in SE Zagros, Iran, Int. J. of Remote Sensing, 56(12): 152-167.
  • Yousefi, E. & Friedberg J. L. 1978, Aeromagnetic Map of Iran, Quadrangle No. G12, H11, H12, H13, H14, I12, I13, Scale 1:250000, Geological Survey of Iran.
  • Zadeh, R. M.& Sarkarinejad, K., 2013, Webster R. Spatial Heterogeneity of Tectonic Features in the Area between the Qatar-Kazerun and the Minab Faults, the Southeast of the Zagros Fold-and-Thrust Belt, Iran, Geoinformatics & Geostatistics: An Overview 1(3): 247-256.