پتروژنز سنگ‌های آداکیتی پس از تصادم پلیو کواترنری در شمالغرب مرند

نویسندگان

1 انشگاه محقق اردبیلی

2 دانشگاه تبریز

3 دانشگاه نیو برانزویک

چکیده

در شمال­غرب مرند در بخش شمالی نوار آتشفشانی ارومیه-دختر مجموعه­ای از سنگ­های آتش­فشانی با ترکیب آندزیت، داسیت، بازالت­های سدیک، پتاسیک و اولتراپتاسیک قلیایی برونزد دارند که در گستره­ی زمانی میوسن بالائی تا کواترنری به سطح زمین راه یافته­اند. این مقاله به بخش ترکیب­های آندزیتی و داسیتی این سنگ­ها می پردازد که به­طور پراکنده از داخل مجموعه آذرآواری بیرون ریخته­اند. این سنگ­های آتشفشانی دارای بافت پرفیری هستند که شامل فنوکریست­های پلاژیوکلاز، هورنبلند، پیروکسن و به مقدار کم بیوتیت هستند. از لحاظ ژئوشیمیایی این سنگ­ها دارای مقادیرSiO2  در گستره­ی 8/67 – 5/57 درصد وزنی، Al2O3 (5/14 تا 3/16)،Sr  (577- 1185) بالا، نسبت­های بالای Sr/Y (7/30- 46/84) و La/Yb (27/13- 36/61) و مقادیر پایین Y (2/11-2/20) هستند که نشان­دهنده ویژگی آداکیتی این ماگماها هستند. ویژگی­های ژئوشیمیائی نمونه­های منطقه­ی با آداکیت­های پر سیلیس (Sr<1100 ppm, Na2O+K2O<11 %wt, MgO = 0.85-3.5)  همخوانی دارد که نشان می­دهد آداکیت­های منطقه­ی مورد بررسی همانند آداکیت­های پرسیلیس از ذوب صفحه­ی بازالتی فرورونده به وجود آمده­اند. همچنین این سنگ­ها از عناصر LILEs و LREEs غنی­شدگی نشان می­دهند (33/6- 39/26(Ce/Yb)N=) و دارای تهی­شدگی نسبی از عناصر انتخابی HFSEs مانند Ta, Ti و Nb هستند. الگوی شدید جدایشی در REE و نیز مقادیر پایین HREEs و Y ممکن است به دلیل وجود گارنت و یا آمفیبول در پسمانده­ی جامد ماگمای این سنگ­ها باشد. همچنین مقادیر بالای استرانسیم و بیهنجاری منفی تانتالیم، نیوبیوم و تیتانیم می­تواند نشانگر عدم حضور پلاژیوکلاز و حضور اکسیدهای آهن و تیتان در تفاله­ی باقیمانده­ی ذوب باشد. ویژگی­های ژئوشیمیائی سنگ­های منطقه نشان می­دهند که شکسته شدن صفحه­ی اقیانوسی فرورونده و ذوب باقیمانده­ی این صفحه موجب تولید ماگماتیسم آداکیتی منطقه­ی شمال­غرب مرند شده­اند. همچنین بالا بودن مقادیر باریم، توریم و روبیدیم می­تواند در اثر آغشتگی ماگما با مواد پوسته­ای در طول صعود ماگماست.

کلیدواژه‌ها


عنوان مقاله [English]

Petrogenesis of Plio-Quaternary post-collisional adakitic rocks in northwest Marand

چکیده [English]

In northwest of Marand northern part of Urumieh Dokhtar Magmatic Arc (UDMA) a set of volcanic rocks crop out with composition of andesite, dacite, and sodic, potassic and ultrapotassic alkaline basalts with Upper Miocene until Plio-Quaternary in age. This paper report the andesitic and dacitic lavas erupted within pyroclastic rocks. These rocks have porphyritic texture and consist of plagioclase, hornblende, pyroxene and a minor biotite phonocrysts. Based on geochemical study, these rocks have SiO2 in rang of 57.5-65.2, high Al2O3 (14.5-16.2) and Sr (557-1185), high Sr/Y (30.7-84.46), La/Yb (13.27-67.36) ratios, and low Y (11.2-20.2) that show adakitic characteristic for the parent magmas. On the base of geochemical characters, these rocks are high- SiO2 adakites which is considered to represent subducted basaltic slab-melts that have reacted with peridotite during ascent through mantle wedge. Also these samples are enriched in LILEs and LREEs and are depleted in some HFSEs like Ta, Nb, and Ti. Intensive fractionated pattern of REEs and low quantities of HREEs and Y may prove existence of garnet or amphibole in the residua of melt. High Sr and negative anomalies of Ta, Nb, and Ti may be resulted from lack of plagioclase and having iron and titanium oxides in the residua phase. Breaking of oceanic slab during subduction and melting of this slab product adakitic magmatism in NW of Marand. High Mg#, Cr, and Ni in rocks indicate metasomatism of melt with mantle wedge. High Ba, Rb, and K2O contents of studied rocks indicate assimilation of magma with crust during rising of magma.

کلیدواژه‌ها [English]

  • adakite
  • Neotethys
  • subduction
  • Urumieh Dokhtar Magmatic Arc
  • Northwest Iran
[1] Denfant M.J., Drummond M.S., "Derivation of some modern arc magmas by melting of young subducted lithosphere". Nature 347 1990 662–665.

[2] Wang Q., McDermott F., Xu J.F., Bellon H., Zhu Y.T., "Cenozoic K-rich adakitic volcanic rocks in the Hohxil area, northern Tibet: lower-crustal melting in an intracontinental setting". Geology 33, 2005. 465–468.

[3] Guo Z., Wilson M., Liu J., "Post-collisional adakites in south Tibet: products of partial melting of subduction-modified lower crust.", Lithos 96, 2007. 205–224.

[4] Grove T. L., Baker M.B., Price R.C., Parman S.W., Elkins-Tanton L.T., Chatterjee N., Müntener O., "Magnesian andesite and dacite lavas from Mt. Shasta, northern California: products of fractional crystallization of H2O-rich mantle melts", Contributions to Mineralogy and Petrology, v. 148, 2005, p. 542-565.

[5] Green N.L., Harry D.L, "On the relationship between subducted slab age and arc basalt petrogenesis, Cascadia subduction system", North America: Earth and Planetary Science Letters, v. 171, 1999, p.367-381.

[6] Alavi M., "Regional stratigraphy of the Zagros folded-thrust belt of Iran and its proforeland evolution.", Am. J. Sci. 304, 2004. 1–20.

[7] Ahmadzadeh G.R., "Petrographical and Petrological Studies of Volcanic Rocks in NW of Marand (north of Galleban)". Unpublished M.Sc. thesis, University of Tabriz, 2002. 114pp, (in Persian).

[8] Omrani J., et al., "Arc-magmatism and subduction history beneath the Zagros Mountains", Iran: A new report of adakites and geodynamic consequences, Lithos (2008),. doi:10.1016/j.lithos.2008.09.008

[9] Jahangiri A., "Post-collisional Miocene adakitic volcanism in NW Iran: geochemical and geodynamic implications". Journal of Asian Earth Sciences 30, 2007. 433–447.

[10] Ahmadzadeh G.R., "Petrological Studies of Volcanic Rocks in NW of Marand spatially alkaline rocks. Unpublished P.H.D thesis", University of Tabriz, 2010. 247pp, (in Persian).

[11] LeBas M.J., Le Maitre R.W., Streckeisen A., Zanettin B., "A chemical classification of volcanic rocks on the total alkali-silica diagram", J. Petrol. 27, 745–750.

[12] MacLean W.H., Barrett T.J., "Lithochemical techniques using immobile elements", Journal of Geochemical Exploration 48, 1993. 109–133.

[13] Martin H., Smithies R.H., Rapp R., Moyen J.-F., Champion D., "An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution", Lithos 79, 2005. 1–24.

[14] Boynton W.V., "Geochemistry of the rare earth elements: meteorite studies. In: Henderson", P. (Ed.), Rare Earth Element Geochemistry. Elsevier, 1984. pp. 63– 114.

[15] Pearce J.A., "Role of the sub-continental lithosphere in magma genesis at active 594 continental margins. In: C.J. Hawkesworth & M.J., Norry, eds. Continental 595 Basalts and Mantle Xenoliths. Shiva Press", Nantwich, U.K., 1983. pp 230-249.

[16] Muller D., Rock N.M.S., Groves D.I., "Geochemical discrimination between shoshonitic and potassic volcanic rocks from different tectonic setting: a pilot study", Mineralogy and Petrology 46, 1992. 259-289.

[17] Martin H., "Adakitic magmas: modern analogues of Archaean granitoids", Lithos 46, 1999. 411– 429.

[18] Plank T., "Constraints from Thorium/Lanthanum on sediment recycling at subduction zones and the evolution of the continents", Journal of Petrology 46, 2005. 921–944.

[19] Wang Q., Wyman D.A., Xu J.F., Wan Y.S., Li C.F., Zi F., Jiang Z.Q., Qiu H.N., Chu Z.Y., Zhao Z.H., Dong Y.H., "Triassic Nb-enriched basalts, magnesian andesites, and adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by slabderived melts in the mantle wedge", Contributions to Mineralogy and Petrology 155, 2008. 473– 490.

[20] Rapp R.P., Watson E.B., "Dehydration melting of metabasalt at 8–32 kbar: implications for continental growth and crust–mantle recycling", Journal of Petrology 36, 1995. 891–931.

[21] Klemme S., Blundy J.D., Wood B.J., "Experimental constraints on major and trace element partitioning during partial melting of eclogite", Geochimica et Cosmochimica Acta 66, 2002. 3109–3123.

[22] Sorensen S.S., Barton M.D., "Metasomatism and partial melting in a subduction complex Catalina schist", southern California. Geology 15, 1987. 115–118.

[23] Kay S.M., Gody E., Kurtz A., "Episodic arc migration, crustal thickening, subduction erosion and magmatism in the south-central Andes", Geological Society of America Bulletin 117, 2005. 67–88.

[24] Peacock S.M., Rushmer T., Thompson A.B., "Partial melting of subducting oceanic crust: Earth and Planetary Science Letters", v. 121, 1994, p. 227-244.

[25] Xu J.F., Shinjio R., Defant M.J., Wang Q., Rapp R.P., "Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China: partial melting of delaminated lower continental crust", Geology 12, 2002. 1111–1114.

[26] Dehghani G.A., Makris J., "The gravity field and crustal structure of Iran, N. Jb. Geol. Palaeont". Abh., 168, 1984. 215–229.

[27] Nicolas A., "Structures in Ophiolites and Dynamics of Oceanic Lithosphere. Kluwer", Dordrecht. 1989. 367 pp.

[28] Searle M.P., Cox J., "Tectonic setting, origin and obduction of the Oman ophiolite. Geological Society of America Bulletin", 111, 1999. 104–122.

[29] Sun S.-s., McDonough W.F., "Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes", In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in the Ocean Basins. Geological Society, London, pp. 313–345.



[1] Denfant M.J., Drummond M.S., "Derivation of some modern arc magmas by melting of young subducted lithosphere". Nature 347 1990 662–665.

[2] Wang Q., McDermott F., Xu J.F., Bellon H., Zhu Y.T., "Cenozoic K-rich adakitic volcanic rocks in the Hohxil area, northern Tibet: lower-crustal melting in an intracontinental setting". Geology 33, 2005. 465–468.

[3] Guo Z., Wilson M., Liu J., "Post-collisional adakites in south Tibet: products of partial melting of subduction-modified lower crust.", Lithos 96, 2007. 205–224.

[4] Grove T. L., Baker M.B., Price R.C., Parman S.W., Elkins-Tanton L.T., Chatterjee N., Müntener O., "Magnesian andesite and dacite lavas from Mt. Shasta, northern California: products of fractional crystallization of H2O-rich mantle melts", Contributions to Mineralogy and Petrology, v. 148, 2005, p. 542-565.

[5] Green N.L., Harry D.L, "On the relationship between subducted slab age and arc basalt petrogenesis, Cascadia subduction system", North America: Earth and Planetary Science Letters, v. 171, 1999, p.367-381.

[6] Alavi M., "Regional stratigraphy of the Zagros folded-thrust belt of Iran and its proforeland evolution.", Am. J. Sci. 304, 2004. 1–20.

[7] Ahmadzadeh G.R., "Petrographical and Petrological Studies of Volcanic Rocks in NW of Marand (north of Galleban)". Unpublished M.Sc. thesis, University of Tabriz, 2002. 114pp, (in Persian).

[8] Omrani J., et al., "Arc-magmatism and subduction history beneath the Zagros Mountains", Iran: A new report of adakites and geodynamic consequences, Lithos (2008),. doi:10.1016/j.lithos.2008.09.008

[9] Jahangiri A., "Post-collisional Miocene adakitic volcanism in NW Iran: geochemical and geodynamic implications". Journal of Asian Earth Sciences 30, 2007. 433–447.

[10] Ahmadzadeh G.R., "Petrological Studies of Volcanic Rocks in NW of Marand spatially alkaline rocks. Unpublished P.H.D thesis", University of Tabriz, 2010. 247pp, (in Persian).

[11] LeBas M.J., Le Maitre R.W., Streckeisen A., Zanettin B., "A chemical classification of volcanic rocks on the total alkali-silica diagram", J. Petrol. 27, 745–750.

[12] MacLean W.H., Barrett T.J., "Lithochemical techniques using immobile elements", Journal of Geochemical Exploration 48, 1993. 109–133.

[13] Martin H., Smithies R.H., Rapp R., Moyen J.-F., Champion D., "An overview of adakite, tonalite–trondhjemite–granodiorite (TTG), and sanukitoid: relationships and some implications for crustal evolution", Lithos 79, 2005. 1–24.

[14] Boynton W.V., "Geochemistry of the rare earth elements: meteorite studies. In: Henderson", P. (Ed.), Rare Earth Element Geochemistry. Elsevier, 1984. pp. 63– 114.

[15] Pearce J.A., "Role of the sub-continental lithosphere in magma genesis at active 594 continental margins. In: C.J. Hawkesworth & M.J., Norry, eds. Continental 595 Basalts and Mantle Xenoliths. Shiva Press", Nantwich, U.K., 1983. pp 230-249.

[16] Muller D., Rock N.M.S., Groves D.I., "Geochemical discrimination between shoshonitic and potassic volcanic rocks from different tectonic setting: a pilot study", Mineralogy and Petrology 46, 1992. 259-289.

[17] Martin H., "Adakitic magmas: modern analogues of Archaean granitoids", Lithos 46, 1999. 411– 429.

[18] Plank T., "Constraints from Thorium/Lanthanum on sediment recycling at subduction zones and the evolution of the continents", Journal of Petrology 46, 2005. 921–944.

[19] Wang Q., Wyman D.A., Xu J.F., Wan Y.S., Li C.F., Zi F., Jiang Z.Q., Qiu H.N., Chu Z.Y., Zhao Z.H., Dong Y.H., "Triassic Nb-enriched basalts, magnesian andesites, and adakites of the Qiangtang terrane (Central Tibet): evidence for metasomatism by slabderived melts in the mantle wedge", Contributions to Mineralogy and Petrology 155, 2008. 473– 490.

[20] Rapp R.P., Watson E.B., "Dehydration melting of metabasalt at 8–32 kbar: implications for continental growth and crust–mantle recycling", Journal of Petrology 36, 1995. 891–931.

[21] Klemme S., Blundy J.D., Wood B.J., "Experimental constraints on major and trace element partitioning during partial melting of eclogite", Geochimica et Cosmochimica Acta 66, 2002. 3109–3123.

[22] Sorensen S.S., Barton M.D., "Metasomatism and partial melting in a subduction complex Catalina schist", southern California. Geology 15, 1987. 115–118.

[23] Kay S.M., Gody E., Kurtz A., "Episodic arc migration, crustal thickening, subduction erosion and magmatism in the south-central Andes", Geological Society of America Bulletin 117, 2005. 67–88.

[24] Peacock S.M., Rushmer T., Thompson A.B., "Partial melting of subducting oceanic crust: Earth and Planetary Science Letters", v. 121, 1994, p. 227-244.

[25] Xu J.F., Shinjio R., Defant M.J., Wang Q., Rapp R.P., "Origin of Mesozoic adakitic intrusive rocks in the Ningzhen area of east China: partial melting of delaminated lower continental crust", Geology 12, 2002. 1111–1114.

[26] Dehghani G.A., Makris J., "The gravity field and crustal structure of Iran, N. Jb. Geol. Palaeont". Abh., 168, 1984. 215–229.

[27] Nicolas A., "Structures in Ophiolites and Dynamics of Oceanic Lithosphere. Kluwer", Dordrecht. 1989. 367 pp.

[28] Searle M.P., Cox J., "Tectonic setting, origin and obduction of the Oman ophiolite. Geological Society of America Bulletin", 111, 1999. 104–122.

[29] Sun S.-s., McDonough W.F., "Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes", In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in the Ocean Basins. Geological Society, London, pp. 313–345.