محاسبه مقدار كوتاه شدگي و رانش در بخش شمالي پهنه زميندرز سيستان جهت تعيين بردارهاي جنبشي همگرايي

Estimation of shortening and vergence in northern part of Sistan Suture Zone for determination of kinematic convergent vectors

در ﻃﯽ ﻓﺮﮔﺸﺖ ﮐﻤﺮﺑﻨﺪﻫﺎي ﮐﻮﻫﺰادي، ﺷﺎﻫﺪ دﮔﺮرﯾﺨﺘﯽ در واﺣﺪﻫﺎي ﺳﻨﮕﯽ ﻣﯽﺑﺎﺷﯿﻢ. ﺑﺮاي ﭘﯽﺑﺮدن ﺑﻪ ﻣﯿﺰان و ﻧﺤﻮه دﮔﺮرﯾﺨﺘﯽ، ﻣﯽﺑﺎﯾﺴﺖ ﺗﻮزﯾﻊ ﮐﺮﻧﺶ، در ﻓﺎزﻫﺎي ﻣﺨﺘﻠﻒ ﻣﺤﺎﺳﺒﻪ ﮔﺮدد. ﺑﺎ اﺳﺘﻔﺎده از ﺳﺎﺧﺘﺎرﻫﺎي ﺳﻄﺤﯽ، ﮐﺮﻧﺶ ﺻﻮرت ﮔﺮﻓﺘﻪ را ﻣﯽﺗﻮان در ﻣﻘﯿﺎسﻫﺎي ﻣﺨﺘﻠﻒ، از رﯾﺰﺳﺎﺧﺘﺎري ﺗﺎ ﻧﺎﺣﯿﻪاي ﻣﺤﺎﺳﺒﻪ ﻧﻤﻮد. در اﯾﻦ ﭘﮋوﻫﺶ، ﺑﻪ ﮐﻤﮏ ﺑﺎز ﻧﻤﻮدن ﭼﯿﻦﻫﺎ و ﮐﺮﻧﺶ اﯾﺠﺎده ﺷﺪه در زﻣﺎن ﺗﺸﮑﯿﻞ ﮔﺴﻞﻫﺎ، ﻣﯿﺰان ﮐﻮﺗﺎهﺷﺪﮔﯽ ﻣﺤﺎﺳﺒﻪ ﮔﺮدﯾﺪ. ﻫﻤﭽﻨﯿﻦ ﺑﺮآوردي از ﻣﯿﺰان راﻧﺶ ﺻﻮرت ﮔﺮﻓﺘﻪ ﺑﻪ ﻣﻨﻈﻮر ﺗﻌﯿﯿﻦ ﺑﺮدارﻫﺎي ﺟﻨﺒﺸﯽ ﻫﻤﮕﺮا اﻧﺠﺎم ﮔﺮدﯾﺪ. اﯾﻦ اﻣﺮ در ﭘﻬﻨﻪ ﺷﻤﺎﻟﯽ زﻣﯿﻦدرز ﺳﯿﺴﺘﺎن در ﺧﺎور اﯾﺮان، ﺑﺮروي ﻣﻘﻄﻊ ﻋﺮﺿﯽ ﺑﺎ روﻧﺪ 60 N از روﺳﺘﺎي ﻧﺎزدﺷﺖ در ﺑﺎﺧﺘﺮ ﺗﺎ ﺧﺎور روﺳﺘﺎي ﺧﻮﺷﺎب، اﻧﺠﺎم ﺷﺪه اﺳﺖ. ﺑﺮاﺳﺎس ﻣﺤﺎﺳﺒﺎت ﻣﯿﺰان ﮐﻮﺗﺎهﺷﺪﮔﯽ ﺑﺮروي ﭼﯿﻦﻫﺎ، 27/3 درﺻﺪ و ﻣﯿﺰان ﮐﻮﺗﺎهﺷﺪﮔﯽ ﺑﺮروي ﮔﺴﻞﻫﺎ، 13/6درﺻﺪ ﻣﯽﺑﺎﺷﺪ. ﻣﯿﺰان ﺑﺮدارﻫﺎي راﻧﺸﯽ در ﭼﯿﻦﻫﺎ، ﺑﺴﻮي ﺷﻤﺎل ﺧﺎور و ﺟﻨﻮب ﺑﺎﺧﺘﺮ ﺑﻪ ﺗﺮﺗﯿﺐ 7/4 و 11/6درﺻﺪ ﻣﯽﺑﺎﺷﺪ. ﻫﻤﭽﻨﯿﻦ ﻣﯿﺰان ﺑﺮدارﻫﺎي راﻧﺸﯽ ﮐﻪ ﺑﻪ واﺳﻄﻪ ﻋﻤﻠﮑﺮد ﮔﺴﻞﻫﺎ ﺻﻮرت ﮔﺮﻓﺘﻪ، ﺑﺴﻮي ﺷﻤﺎل ﺧﺎور و ﺟﻨﻮب ﺑﺎﺧﺘﺮ ﺑﺘﺮﺗﯿﺐ19/35 و 22/82 درﺻﺪ اﺳﺖ. ﺑﻨﺎﺑﺮاﯾﻦ از زﻣﺎن ﺷﺮوع ﻫﻤﮕﺮاﯾﯽ دو ﺻﻔﺤﻪ اﻓﻐﺎن و ﻟﻮت، ﻣﯿﺰان ﺑﺮدارﻫﺎي ﺟﻨﺒﺸﯽ ﺻﻔﺤﻪ اﻓﻐﺎن ﻧﺴﺒﺖ ﺑﻪ ﺻﻔﺤﻪ ﻟﻮت، 7/7 درﺻﺪ ﺑﯿﺸﺘﺮ ﻣﯽﺑﺎﺷﺪ و ﺟﻬﺖ اﻧﺘﻘﺎل زﻣﯿﻦﺳﺎﺧﺘﯽ و ﻓﺮوراﻧﺶ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺴﻮي ﺟﻨﻮب ﺑﺎﺧﺘﺮ و ﺷﻤﺎل ﺧﺎور ﻣﯽﺑﺎﺷﺪ.

Estimation of shortening and vergence in northern part of Sistan Suture Zone for determination of kinematic convergent vectors During the evolution of orogenic belts, the rock units are deformed. Aim to the understanding of the amount and condition of deformation, the strain states should be estimated which took place during different deformation phases. By means of superficial sturctures, strain states can be estimated in verious scales from microscopic to regional scale. In this study, estimation of shortening has been measured by using unfolding folds and measurement of strain states during making of faults. Amount of vergence states also evaluated which occurred, for purpose of determining the kinematic convergent vectors. For this reason, in the northern part of strurctural Sistan province in the east of Iran, the study has been done on the section which begins from Nazdasht village in west to eastern part of Khoshab village in east, with trending of N60°. Based on the estimations, the folds and faults experienced 27.3 and 13.6 percent shortening respectively. The vergence vectors situations for folds show 7.4 and 11.6 percent for NE and SW direction, respectively. The vergence vectors situations also which has been made by faulting are 19.35 and 22.82 percent for NE and SW direction, respectively. From beginning of converging between Afghan and Lut plates, the vergence vectors situations of Afghan plate is 7.7 percent more than Lut plate. Finally, direction of subduction and tectonic transfer direction have NE and SW trends, respectively.