معرفی و بررسی ساختاری پهنه گسلی عرضی- برشی عزالدین- راهجرد؛ یکی از ساختارهای با توان فعالیت در گستره شهرستان تفرش

نوع مقاله : Articles

نویسنده

گروه زمین‌شناسی، دانشکده علوم پایه، دانشگاه بین‌المللی امام خمینی (ره)، قزوین

چکیده

شناسایی دقیق چشمه و پتانسیل‌های لرزه‌ای از مهم‌ترین اقدامات لازم و قدم نخست برای مطالعات لرزه‌خیزی هر منطقه به شمار می‌رود. گستره مورد مطالعه که در بخش میانی کمان ماگمایی ارومیه دختر واقع است، یکی از مناطقی است که شناسایی و مطالعه دقیق چشمه‌های لرزه‌ای آن ضروری به نظر می‌رسید. در این پژوهش با تفسیر تصاویر ماهواره‌ای و بازدیدهای میدانی و بررسی‌های ریخت‌زمین‌ساختی منطقه، برای نخستین بار سامانه گسلی عزالدین- راهجرد با روند 150-N و طول بیش از 70 کیلومتر معرفی می‌شود. این پهنه گسلی، همروند با گسله­های عرضی- برشی دیگر همچون گسله‌های بیدهند، قم- زفره و دهشیربافت، سنگ‌های آتش‌فشانی کمان ماگمایی را بریده است. خش لغز گسلی، خمش راست‌بر روند محور چین‌های اصلی در راستای گسله و تشکیل ساختارهای فرعی مرتبط با آن بیانگر حرکت راست­بر این گسله است. بررسی زمین‌ریخت‌شناسی و جابه‌جایی راست‌بر آبراهه‌ها با گسله، بیانگر فعالیت گسله در زمان کواترنری است. انطباق مرکز سطحی زمین‌لرزه‌ها بر روی این گسله، اهمیت شناسایی و معرفی این پهنه گسلی را در مطالعات لرزه‌خیزی منطقه نشان می‌دهد. لذا احتمال وقوع زمین‌لرزه ویرانگر در اثر فعالیت پهنه گسلی عرضی-برشی عزالدین- راهجرد به‌عنوان گسلی که فعالیت کواترنری داشته است، دور از انتظار نیست و ممکن است در خطر لرزه‌ای شهرستان تفرش و مناطق هم‌جوار نقش تعیین‌کننده داشته باشد.

کلیدواژه‌ها


عنوان مقاله [English]

Introduction and Structural Study of the Ezedin-Rahjerd Transverse Fault Zone, One of the Seismic Potential Structures in Tafresh Area

نویسنده [English]

  • Zeinab Davoodi
Department of Geology, Faculty of Science, Imam Khomeini International University, Qazvin, Iran
چکیده [English]

Accurate identification of seismic potential is the first step and one of the most important for seismic studies in each region. The study area, located in the middle part of the Urmia-Dokhtar magmatic arc belt, is one of the areas where identify and study of its seismic sources is necessary. In this study, for the first time, the Ezedin-Rahjerd fault system is introduced according to the interpretation of satellite images, field study and tectonic surveys of the area. The Cenozoic (Eocene) volcanic rocks of the Tafresh area, which are covered with Lower and Upper Red Formations have been cut by this N-150 transverse fault of 70 km. This fault system, like other transverse faults such as the Bidhend, Qom-Zefreh and Dehshir-baft faults, has cut volcanic rocks of the magmatic arc belt. Geometry pattern detection of the structures using satellite images and field observations in the area showed that the effect of this fault are observed as the change of the main structure trends such as the reverse faults and fold axes bending and the formation of minor structures with a different trend from the main structures trends of the Urmia-Dokhtar belt. The slicken lines of the fault plane and the right-lateral bending of the main fold axes along the fault zone and the formation of minor structures indicates the right lateral movement of the Ezedin-Rahjerd fault zone.
One of the prominent features of the study area is the existence of several parallel dyke sets that are not very distant and sometimes outcropping at a distance of less than 200 m. These dykes with a thickness of about 2-5 m and a length of about 15-20 m with dip of more than 80 degrees are divided into two sets with dominant trends N40-45W and N20-30E. The first set of dykes with N40-45W trending are a semi-deep dolerite and porphyro gabbro diorite that exposed around the Gyan and Lalaein villages and cutting Eocene and older units. Whereas, the second N20-30E trending shallow dikes with combining of hornblende, andesite and basaltic andesite also cuts Miocene volcanic-sedimentary rocks, Qom Formation and Lower Red Formation. Alteration of the second dyke set is significant. The trend, including rocks and tectonic setting of the dykes, show their influence in several stages. These intrusive dikes also show tension fractures, so will assist in structural analysis of the area. In such a right lateral transverse fault zone, development of the tension fractures with N20-30E trend is not unexpected. Therefore, the second shallow N20-30E dyke set are formed in these tension fractures due to the Ezedin-Rahjerd transverse fault activity. While the first set with N40-45W trending that is older than the second one, has been created due to the main structures of the Urmia-Dokhtar magmatic belt.
The most important geomorphological feature observed along the Ezedin-Rahjerd fault is the conformity of the Kamar (Tafresh) river as the main river of the area with the fault trend. The Kamar River flows north-south along the Ezedin-Rahjerd fault, passing through the Barezjan, Dadghan, and Ezedin villages, and then reaches the Ghareh-Chai River in Jalaier. Instrumental earthquakes of the area show 2

کلیدواژه‌ها [English]

  • Transverse Fault Zone
  • Ezedin-Rahjerd Fault
  • Seismic Potential
  • Central Iran
  • Tafresh
  1. Zanchi, A., Zanchetta, S., Balini, M., and Ghassemi, M.R. (2016) Oblique convergence during the Cimmerian collision: Evidence from the Triassic Aghdarband Basin, NE Iran. Gondwana Research, 38, 149-170.
  2. Pirozi, H., Davoodi, Z., and Asiabanha, A. (2015) Tectonic setting of the analcime basalts of Taleghan area. 33th Geosciences Congress, Geological Society of Iran, Tehran (in Persian).
  3. Davoodi, Z. (2016) Influence of the basement strike-slip fault on the 2005 and 2014 Earthquakes, Qeshm Island, Iran. Journal of Seismology and Earthquake Engineering, 18(4), 219-230.
  4. Cornell, C.A. (1968) Engineering seismic risk analysis. Bull. Seis. Soc. Am., 58(5), 1583-1606.
  5. Talebian, M., Biggs, J., Bolourchi, M., Copley, A., Gassemi, A., Ghorashi, M., Hollingsworth, J., Jackson, J., Nissen, E., Oveisi, B., Parsons, B., Priestley, K., and Saiidi, A. (2006) The Dahuiyeh (Zarand) earthquake of 2005 February 22 in central Iran: reactivation of an intra-mountain reverse fault. Geophysical Journal International, 164, 137-148.
  6. Sella, F., Dixon, H., and Mao, A. (2002) REVEL: A model for Recent plate velocities from space geodesy. Journal of Geophysical Research, 107(B4).
  7. Vernant, P., Nilforoushan, F., Hatzfeld, D., Abassi, M., Vigny, C., Masson, F., Nankali, H., Martinod, J., Ghafory-Ashtiany, M., Bayer, R., Tavakoli, F., and Chery, J. (2004) Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman. Geophys. J. Int., 157, 381-398.
  8. Kohansal, R. and Radfar, J. (2003) Geological Map of Farmahin in 1:100000, Geological Survey of Iran.
  9. Alai Mahabadi, S. (2000) Geological Map of Salafcheghan in 1:100000, Geological Survey of Iran.
  10. Radfar, J. and Kohansal, R. (2004) Geological Map of Arak in 1:100000, Geological Survey of Iran.
  11. Hadjian, J. (1970) Geological Map of Tafresh in 1:100000, Geological Survey of Iran.
  12. Agard, P., Omrani, J., Jolivet, L., and Mouthereau, F. (2005) Convergence history across Zagros (Iran): constraints from collisional and earlier deformation. International Journal of Earth Sciences, 94, 401-419.
  13. Allen, M. and Armstrong, H.A. (2008) Arabia-Eurasia collision and the forcing of Mid-Cenozoic global cooling. Palaeogeography Palaeoclimato-logy Palaeoecology, 265(1), 52-58.
  14. Horton, B.K., Hassanzadeh, J., Stockli, D.F. , Axen, G.J., Gillis, R.J., Guest, B., Amini, A., Fakhari, M.D., Zamanzadeh, S.M., and Grove, M. (2008) Detrital zircon provenance of Neoproterozoic to Cenozoic deposits in Iran: Implications for chronostratigraphy and collisional tectonics. Tectonophysics, 451(1-4), 97-122.
  15. Morley, C.K., Kongwung, P., Julapour, A., Abdolghafourian, M., Hajian, M., Waples, D., Warren, J., Otterdoom, H., Srisuriyon, K., and Kazemi, H. (2009) Structural development of a major late Cenozoic basin and transpressional belt in central Iran: the central basin in the Qom-Saveh area. Geosphere, 5, 1-38.
  16. StÓ§cklin, J. (1974). Possible ancient continental margins in Iran. In: The Geology of Continent Margins (Eds. Burke, C.A. and Darke, C.L.), 873-887.
  17. Farhoudi, G.H. (1978) A comparison of Zagros geology to island-arcs. Journal of Geology, 86, 323-334.
  18. Berberian, M. (1981) The south Caspian: a compressional depression floored by a trapped, modified oceanic crust. Canadian Journal of Earth Science, 20, 163-183.
  19. Berberian, M. and King, G. (1981) Towards a palaeogeography and tectonic evolution of Iran. Canadian Journal of Earth Sciences, 18, 210-265.
  20. Berberian, F., Muir, F.I.D., Pankhurst, R.J., and Berberian, M. (1982) Late cretaceous and early Miocene Andean type plutonic activity in northern Makran and central Iran. Journal of Geological Society, 139, 605-614.
  21. Alavi, M. (1994) Tectonic of the Zagros orogenic belt of Iran: new data and interpretations. Tectonophysics, 229, 211-238.
  22. Shahabpour, J. (2005) Tectonic evolution of the orogenic belt located between Kerman and Neyriz. Journal of Asian Earth Sciences, 24, 405-417.
  23. Ghasemi, A. and Talbot, C.J. (2006) A new scenario for the Sanandaj-Sirjan zone (Iran). Journal of Asian Earth Sciences, 26, 683-693.
  24. Alavi, M. (2007) Structures of the Zagros fold thrust belt in Iran. American Journal of Science, 307, 1064-1095.
  25. Hassanzadeh, J. (1993) Metallogenic and Tectono-Magmatic Events in the SE Sector of the Cenozoic Active Continental Margin of Iran. PhD thesis, University of California, Los Angeles.
  26. Nilforoushan, F., Vernant, P., Masson, F., Vigny, C., Martinod, J., Abbassi, M., Nankali, H., Hatzfeld, D., Bayer, R., Tavakoli, F., Ashtiani, A., Doerflinger, E., Daignières, M., Collard, P., and Chery, J. (2003) GPS network monitors the Arabia-Eurasia collision deformation in Iran. Journal of Geodesy, 77, 411-422.
  27. Berberian, M. (1976) Documented earthquake faults in Iran. Rep. 39, Geological Survey of Iran, Tehran (in Persian).
  28. Nogol-e Sadat, M.A.A. (1978) Shear zones and structural bending in Iran, Achievements of structural analysis of Qom area. Rep.55, Geological Society of Iran, Tehran (in Persian).
  29. Mohajjel, M. (2000) Role of the en-echelon extensional spaces in intrusive of igneous rocks in Kashan-Ardestan area, a pattern for formation of the Urmia-Dokhtar magmatic arc. 19th Geosciences Congress, Geological Society of Iran, Tehran (in Persian).
  30. Mohajjel, M. and Porouhan, N. (2005) Geometry and kinematics of Qom-Zefreh fault system and its significance in transpresssion tectonics. Geosciences, 14(59), 167-173 (in Persian).
  31. Meyer, B., Mouthereau, F., Lacombe, O., and Agard P. (2006) Evidence of Quaternary activity along the Deshir Fault: implication for the Tertiary tectonics of Central Iran. Geophys. J. Int., 164, 192-201.
  32. Emami, M. and Hadjian, J. (1370) Geological Map of Qom in 1:250000, Geological Survey of Iran.
  33. Khademi, F. (2014) The study of facies and geochemistry of magmatic rocks in the Shahrab-Feshk districts, NE Farmahin. Ms. Thesis, Imam Khomeini International University, Qazvin (in Persian).
  34. Kazemi, H. (2005) Petrology of Dykes in East of Tafresh. Ms. Thesis, Shahid Beheshti University, Tehran (in Persian).
  35. Rajabion, J. (2005) Brittle Deformation Analysis in Tafresh Area. M.Sc. Thesis, Tarbiat Modares University, Tehran (in Persian).
  36. Ramsay, J.G. and Huber M.I. (1987) The Techniques of Modern Structural Geology. 2, Folds and Fractures, Academic Press, London.
  37. Nadri, R., Mohajjel, M., and Bahroudi, A. (2010) Bidhand strike-slip fault system (South of Qom). Geosciences, 18(74), 177-184 (in Persian).