منشاء و ژئودینامیک دلریت‌های گنبد نمکی کوهرنگ

نوع مقاله : علمی -پژوهشی

نویسندگان

1 گروه مهندسی طبیعت، دانشکده منابع طبیعی و علوم زمین، دانشگاه شهرکرد، شهرکرد، ایران

2 گروه مهندسی معدن، دانشکده مهندسی، دانشگاه کردستان، سنندج، ایران

چکیده

در این مقاله به بررسی خصوصیات سنگ­شناسی و ژئوشیمیایی سنگ­های مافیک ناحیه کوهرنگ به عنوان بخشی از پهنه ساختاری زاگرس در استان چهارمحال و بختیاری پرداخته می­شود. سنگ­های آذرین گنبد نمکی کوهرنگ دارای بافت اینترگرانولار و گاهی افتیک با کانی­شناسی پلاژیوکلاز، پیروکسن، آمفیبول، تیتانیت و لوکوکسن می­باشند. این سنگ­ها حاوی 10/48 -02/47 درصد وزنی سیلیس بوده و از نظر ترکیبی در محدوده سنگ­های آذرین بازیک قرار می­گیرند. این سنگ­ها میزان K2O متغیر (34/1-28/4 درصد وزنی)، Na2O متوسط (11/1–37/2 درصد وزنی)، MgO (21/5–29/6 درصد وزنی) و *Fe2O3 (93/3- 60/4 درصد وزنی) را نشان می­دهند. میزان TiO2 در آنها نسبتا بالاست. در نمودار به هنجار شده به کندریت غنی­شدگی از LREES نسبت به عناصر HREES مشاهده می­شود که بیانگر ماهیت E-MORB برای ماگمای منشا این سنگ­هاست. نمودارهای ژئوشیمیایی، شکل­گیری سنگ­های منطقه در محیط درون صفحه و ریفت قاره­ای را نشان می­دهد که دارای منشا مانتوی آستنوسفری بوده و آلایش پوسته­ایی چندانی را متحمل نشده است. نسبت CaO/Al2O3 برابر 66/00-48/0 به همراه الگوی تخت در HREE موید یک منشا مانتویی اسپینل­دار است.

کلیدواژه‌ها

عنوان مقاله [English]

Source and geodynamics of dolerites of Kuhrang salt dome

نویسندگان [English]

  • Pardis Jafari 1
  • Nahid Shabanian Boroujeni 1
  • Alireza Davoudian Dehkordi 1
  • Hossein Azizi 2
1 Department of Natural Engineering, Faculty of Natural Resources and Earth Sciences, Shahrekord University, Shahrekord, Iran
2 Department of Mining Engineering, Faculty of Engineering, University of Kurdistan, Sanandaj, Iran
چکیده [English]

IntroductionFormation and rocks of Kuhrang salt dome in Zagros zone, Chaharmahal Va Bakhtiari province, are equivalent to the same units in the Hormuz Formation of Persian Gulf. Evaporate basins of Late Precambrian – Early Cambrian resulted in the deposition of Hormuz and similar series (Arian and Noroozpour, 2015; Motiei, 2001). The basins were formed due to the extensional tectonic phase, as a continental rift, in the continental crust of Iran and neighboring countries occurred during Infracambrian (Nabavi, 1976; Stöcklin, 1968; Berberian and King, 1981). Acidic and mostly alkaline magmatism is dominated in the rifts resulting from the extensional phase (Berberian and King, 1981).Magmas of the continental rifts mainly have alkaline nature and they are rich volatile material (e.g. halogens and CO2) and LILE (Lithophile large ion elements), indicating they are driven from enriched sources of the mantle (Wilson, 1989; Bailey, 1983). In the continental rift regions, the lavas mostly form during the fractional crystallization of basaltic magmas which are contaminated by the variant degree of crustal sources (Wilson, 1989).The aim of the paper is the determination of geochemical characters, tectonic setting and source of the doleritic rocks of Kuhrang salt dome by using whole-rock analyses.Materials and methodsAfter field sampling and microscopic studies, 8 fresh samples were analyzed for whole-rock geochemical determination by ICP-ES and ICP-MS methods in ACME lab (Vancouver, Canada). Results and discussionThe igneous rocks of Kuhrang salt dome display the including textures (intergranular and sometimes ophitic). Their mineralogy consists of plagioclase, pyroxene, amphibole, titanite and leucoxene. Compositionally, the rocks have 47.02-48.10 %wt. of SiO2. Therefore they plot in field of basic igneous rocks. The rocks display variable contents of K2O (3.34-4.28 wt.%), medium values of Na2O (1.11-2.37 wt.%), MgO (5.21-6.29 wt.%) and Fe2O3*(3.93-4.60 wt.%).In the Zr/TiO2-Nb/Y diagram (Winchester and Floyd, 1977), the studied rocks are plotted in basalt field and have sub-alkaline nature. Also, the samples display tholeiitic nature on the Ce/Yb-Ta/Yb diagram (Pearce, 1982). The chondrite normalized REE patterns show low enrichment in the LREEs relative to HREEs, which confirm E-MORB nature for their origin. Geochemical diagrams (e.g. Zr/Y-Zr (Pearce and Norry, 1979); Zr/4-Y-2 Nb (Meschede, 1986); Zr/117-Th- Nb/16 (Wood, 1980); Ti-Zr (Pearce, 1982)) show that the rocks have occurred in tectonic setting of intracontinental rift. TiO2 concentrations (2.38-2.48 wt.%) are relatively high in the rocks suggesting asthenospheric mantle (enrichment mantle) as their source. Moreover, flat patterns in HREEs (TbN/YbN= 1.58-1.74) and CaO/Al2O3 ratios (0.48-0.66) demonstrate spinel-mantle sources rather than garnet ones. Enrichment of Ba, Rb, K and K2O>Na2O and Rb/Sr-Ba/Rb diagram (Furman and Graham, 1999) reveal a mantle source involvement of phlogopite (Rosenthal et al., 2009).ConclusionBasic magma of Kuhrang salt dome doleritic rocks, show sub-alkaline nature (tholeiite) with various K2O contents. It has been formed in tectonic setting of intra- continental rift due to low partial melting of phlogopite spinel lherzolite of asthenospheric mantle. 

کلیدواژه‌ها [English]

  • Intra continental rifts
  • Dolerite
  • Salt dome
  • Zagros

مراجع

-اصفهانی، ف.، 1372. پترولوژی سنگ آذرین و دگرگونی گنبد نمکی چهارمحال بختیاری، رساله کارشناسی‌ارشد، گروه زمین‌شناسی، دانشگاه اصفهان.
-مدیریت اکتشاف شرکت ملی نفت ایران، نقشه زمین‌شناسی 1:100000 باباحیدر.
-نبوی، م.، 1۳۵۵. دیباچه‌ای بر زمین‌شناسی ایران، انتشارات سازمان زمین‌شناسی کشور، 110 ص.
-Agrawal, S., Guevara, M. and Verma, S.P., 2008. Tectonic discrimination of basic and ultrabasic volcanic rocks through log-transformed ratios of immobile trace elements: International Geology Review, v. 50, p.1057-1079.
-Alici, P., Temel, A., Gourgaud, A., Vidal, P. and Gundogdu, M.N., 2001. Quaternary tholeiitic to alkaline volcanism in the Karasu Valley, Dead Sea Rift Zone, Southeast Turkey: Sr-Nd-Pb-O isotopic and trace-element approaches to crust-mantle interaction: International Geology Review, v. 43, p. 120-138.
-Arian, M. and Noroozpour, H., 2015. Tectonic Geomorphology of Iran’s Salt Structures: Open Journal of Geology, v. 5 (02), p. 61-79.
-Ayalew, D., Jung, S., Romer, R., Kersten, F., Pfänder, J. and Garbe-Schönberg, D., 2016. Petrogenesis and origin of modern Ethiopian rift basalts: Constraints from isotope and trace element geochemistry: Lithos, v. 258, p.1-14.
-Bailey, D., 1983. The chemical and thermal evolution of rifts: Tectonophysics, v. 94, p. 585-597.
-Berberian, M. and King, G., 1981. Towards a paleogeography and tectonic evolution of Iran: Canadian journal of earth sciences, v. 18, p. 210-265.
-Boynton, W.V., 1984. Cosmochemistry of the rare earth elements: meteorite studies, Rare earth element geochemistry: Elsevier.
-Chukwu, A. and Obiora, S.C., 2014. Whole-rock geochemistry of basic and intermediate intrusive rocks in the Ishiagu area: further evidence of anorogenic setting of the Lower Benue rift, southeastern Nigeria: Turkish Journal of Earth Sciences, v. 23(4), p. 427-443.
-Clague, D.A. and Frey, F.A., 1982. Petrology and trace element geochemistry of the Honolulu Volcanics, Oahu: implications for the oceanic mantle below Hawaii: Journal of Petrology, v. 23(3), p.447-504.
-Dostal, J., Wilson, R.A. and Keppie, J.D., 1989. Geochemistry of Siluro-Devonian Tobique volcanic belt in northern and central New Brunswick (Canada): tectonic implications: Canadian Journal of Earth Sciences, v. 26(6), p. 1282-1296.
-Fitton, J., James, D., Kempton, P., Ormerod, D. and Leeman, W., 1988. The role of lithospheric mantle in the generation of late Cenozoic basic magmas in the western United States: Journal of Petrology, v. 1, p. 331-349.
-Foley, S., Venturelli, G., Green, D.H. and Toscani, L., 1987. The ultrapotassic rocks: characteristics, classification, and constraints for petrogenetic models: Earth-Science Reviews, v. 24 (2), p. 81-134.
-Furman, T. and Graham, D., 1999. Erosion of lithospheric mantle beneath the East African Rift system: geochemical evidence from the Kivu volcanic province: Lithos, v. 48(1), p. 237-262.
-Hofmann, A., Jochum, K., Seufert, M. and White, W., 1986. Nb and Pb in oceanic basalts: new constraints on mantle evolution. Earth and Planetary science letters, v. 79, p. 33-45.
-Harangi, S., 1994. Geochemistry and petrogenesis of the Early Cretaceous continental rift-type volcanic rocks of the Mecsek Mountains, South Hungary: Lithos, v. 33(4), p. 303-321.
-Haynes, S.J. and McQuillan, H., 1974. Evolution of the Zagros suture zone, southern Iran: Geological Society of America Bulletin, v. 85, p. 739-744.
-Hellman, P.L., Smith, R.E. and Henderson, P., 1979. The mobility of the rare earth elements: evidence and implications from selected terrains affected by burial metamorphism: Contributions to Mineralogy and Petrology, v. 71, p. 23-44.
-Hofmann, A., Jochum, K., Seufert, M. and White, W., 1986. Nb and Pb in oceanic basalts: new constraints on mantle evolution: Earth and Planetary science letters, v. 79, p. 33-45.
-Kent, P., 1979. The emergent Hormuz salt plugs of southern Iran: Journal of petroleum geology, v. 2, p. 117-144.
-Khodabakhshnezhad, A. and Arian, M., 2016. Salt Tectonics in the Southern Iran: International Journal of Geosciences, v. 7(03), p. 367.
-Kolb, M., Paulick, H., Kirchenbaur, M. and Münker, C., 2012. Petrogenesis of mafic to felsic lavas from the Oligocene Siebengebirge volcanic field (Germany): implications for the origin of intracontinental volcanism in Central Europe: Journal of Petrology, v. 53(11), p. 2349-2379.
-Leat, P., Thompson, R., Morrison, M., Hendry, G. and Dickin, A., 1988. Compositionally-Diverse Miocene—Recent Rift-Related Magmatism in Northwest Colorado: Partial Melting, and Mixing of Mafic Magmas from 3 Different Asthenospheric and Lithospheric Mantle Sources: Journal of Petrology, v. 3, p. 351-377.
-Le Bas, M., Maitre, R.L., Streckeisen, A. and Zanettin, B., 1986. A chemical classification of volcanic rocks based on the total alkali-silica diagram: Journal of petrology, v. 27, p. 745-750.
-Lustrino, M. and Wilson, M., 2007. The circum-Mediterranean anorogenic Cenozoic igneous province: Earth-Science Reviews, v. 81(1), p. 1-65.
-McDonough, W., 1990. Constraints on the composition of the continental lithospheric mantle: Earth and Planetary Science Letters, v. 101, p. 1-18.
-McKenzie, D. and Bickle, M., 1988. The volume and composition of melt generated by extension of the lithosphere: Journal of petrology, v. 29, p. 625-679.
-McKenzie, D. and O'nions, R.K., 1995. The source regions of ocean island basalts: Journal of petrology, v. 36, p. 133-159.
-Meschede, M., 1986. A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb 1bZr 1bY diagram, Chemical geology, v. 56, p. 207-218.
-Motiei, H., 2001. Simplified table of rock units in southwest Iran: Tehran, Keyhan Exploration and Production Services.
-Müller, D. and Groves, D.I., 2000. Potassic Igneous Rocks and Associated Gold-Copper Mineralization, Berlin: Springer, 311 p.
-Murphy, J.B., 2007. Igneous rock associations 8. Arc magmatism II: geochemical and isotopic characteristics: Geoscience Canada, v. 34(1), p. 7-35.
-Norman, M.D., 1998. Melting and metasomatism in the continental lithosphere: laser ablation ICPMS analysis of minerals in spinel lherzolites from eastern Australia: Contributions to Mineralogy and Petrology, v. 130(3), p. 240-255.
-Pearce, J.A., 1982. Trace element characteristics of lavas from destructive plate boundaries: Andesites, v. 8, p. 525-548.
-Pearce, J.A. and Norry, M.J., 1979. Petrogenetic implications of Ti, Zr, Y, and Nb variations in volcanic rocks: Contributions to mineralogy and petrology, v. 69, p. 33-47.
-Pfänder, J.A., Jung, S., Münker, C., Stracke, A. and Mezger, K., 2012. A possible high Nb/Ta reservoir in the continental lithospheric mantle and consequences on the global Nb budget–Evidence from continental basalts from Central Germany: Geochimica et Cosmochimica Acta, v. 77, p. 232-251.
-Polat, A., Kerrich, R. and Casey, J., 1997. Geochemistry of Quaternary basalts erupted along the East Anatolian and Dead Sea fault zones of Southern Turkey: implications for mantle sources: Lithos, v. 40, p. 55-68.
-Rosenthal, A., Foley, S., Pearson, D.G., Nowell, G.M. and Tappe, S., 2009. Petrogenesis of strongly alkaline primitive volcanic rocks at the propagating tip of the western branch of the East African Rift: Earth and Planetary Science Letters, v. 284, p. 236-248.
-Saccani, E. and Photiades, A., 2005. Petrogenesis and tectonomagmatic significance of volcanic and subvolcanic rocks in the Albanide–Hellenide ophiolitic melanges: Island Arc, v. 14(4), p. 494-516.
-Sarkarinejad, K., Godin, L. and Faghih, A., 2009. Kinematic vorticity flow analysis and 40Ar/39Ar geochronology related to inclined extrusion of the HP–LT metamorphic rocks along the Zagros accretionary prism, Iran: Journal of Structural Geology, v. 31(7), p. 691-706.
-Sen, G., Frey, F.A., Shimizu, N. and Leeman, W.P., 1993. Evolution of the lithosphere beneath Oahu, Hawaii: rare earth element abundances in mantle xenoliths: Earth and Planetary Science Letters, v. 119(1), p. 53-69.
-Srivastava, R.K. and Gautam, G.C., 2009. Precambrian mafic magmatism in the Bastar craton, Central India: Journal of the Geological Society of India, v. 73(1), p. 52-72.
-Srivastava, R.K. and Singh, R.K., 2004. Trace element geochemistry and genesis of Precambrian sub-alkaline mafic dikes from the central Indian craton: evidence for mantle metasomatism: Journal of Asian Earth Sciences, v. 23(3), p. 373-389.
-Srivastava, R.K., 2006. Geochemistry and petrogenesis of Neoarchaean high-Mg low-Ti mafic igneous rocks in an intracratonic setting, Central India craton: Evidence for boninite magmatism: Geochemical Journal, v. 40(1), p. 15-31.
-Stöcklin, J., 1968. Structural history and tectonics of Iran: a review, AAPG Bulletin, v. 52, p. 1229-1258.
-Sun, S.S. and McDonough, W.S., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes: Geological Society, London, Special Publications, v. 42, p. 313-345.
-Talbot, C. and Alavi, M., 1996. The past of a future syntaxis across the Zagros: Geological Society, London, Special Publications, v. 100, p. 89-109.
-Thompson, R. and Morrison, M., 1988. Asthenospheric and lower-lithospheric mantle contributions to continental extensional magmatism: an example from the British Tertiary Province: Chemical Geology, v. 68, p.1-15.
-Verma, S.P., 2012. Application of multi-dimensional discrimination diagrams and probability calculations to acid rocks from Portugal and Spain: Comunicações Geologicas, v. 99, p. 79-93.
-Verma, S.P., Guevara, M. and Agrawal, S., 2006. Discriminating four tectonic settings: Five new geochemical diagrams for basic and ultrabasic volcanic rocks based on log—ratio transformation of major-element data: Journal of Earth System Science, v. 115, p. 485-528.
-Wang, X.L., Zhou, J.C., Qiu, J.S., Jiang, S.Y. and Shi, Y.R., 2008. Geochronology and geochemistry of Neoproterozoic mafic rocks from western Hunan, South China: implications for petrogenesis and post-orogenic extension: Geological Magazine, v. 145(02), p. 215-233.
-Wilson, M., 1989. Igneous petrogenesis: A global tectonic approach: London, Unwyn Hyman.
-Winchester, J. and Floyd, P., 1977. Geochemical discrimination of different magma series and their differentiation products using immobile elements: Chemical geology, v. 20, p. 325-343.
-Wood, D.A., 1980. The application of a Th-Hf-Ta diagram to problems of tectonomagmatic classification and to establishing the nature of crustal contamination of basaltic lavas of the British Tertiary Volcanic Province: Earth and planetary science letters, v. 50(1), p. 11-30.
-Wu, Y.W., Li, C., Xu, M.J., Xiong, S.Q., Fan, Z.G., Xie, C.M. And Wang, M., 2016. Petrology and geochemistry of metabasalts from the Taoxinghu ophiolite, central Qiangtang, northern Tibet: Evidence for a continental back-arc basin system, Austrian Journal of Earth Sciences, v. 109(2), p. 166-177.
-Yang, J.H., Sun, J.F., Chen, F., Wilde, S.A. and Wu, F.Y., 2007. Sources and petrogenesis of Late Triassic dolerite dikes in the Liaodong Peninsula: Implications for post-collisional lithosphere thinning of the eastern North China Craton: Journal of Petrology, v. 48(10), p. 1973-1997.

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