تعیین شرایط و عوامل موثر بر رخداد ذوب بخشی در زنولیتهای میگماتیتی چاه بازرگان (شمالشرق نیریز) با استفاده از نمودارهای فازی ترمودینامیکی | ||
| پژوهشهای دانش زمین | ||
| مقاله 2، دوره 14، شماره 1 - شماره پیاپی 53، 1402، صفحه 18-31 اصل مقاله (1.55 M) | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.48308/esrj.2023.103056 | ||
| نویسندگان | ||
| عبدالناصر فضل نیا1؛ میر محمد میری* 2؛ عادل ساکی2 | ||
| 1گروه زمینشناسی، دانشگاه ارومیه، ارومیه، ایران | ||
| 2گروه زمینشناسی، دانشکده علوم زمین، دانشگاه شهید چمران اهواز، اهواز، ایران | ||
| چکیده | ||
| قطعات فرو افتاده گارنت – بیوتیت - کیانیت شیستها از مجموعه دگرگونیهای ناحیهای قوری نیریز با سن 187 میلیون سال پیش(بخش جنوبی زون سنندج - سیرجان) به داخل توده نفوذی لوکودیوریتهای چاه بازرگان با سن 173 میلیون سال پیش، باعث شد تا این قطعات(زنولیت) درجات دگرگونی مجاورتی شدیدی را تحمل و به زنولیتهای میگماتیتی تبدیل شوند. بخشهایی از مذابهای تولید شده، تجمع یافتند و در نتیجه منجر به ایجاد غلافها و عدسیهای لوکوگرانیتی درون این نفوذیها شدند. براساس بررسیهای سنگنگاری گردهماییهای متعادل اسپینل + گارنت + فلدسپار پرتیتی + کردیریت + سیلیمانیت و اسپینل + گارنت + فلدسپار پرتیتی + کردیریت در شرایط اوج دگرگونی شکل گرفتهاند. نمودارهای فازی محاسبه شده برای نمونه زنولیتی، نشان میدهد که در حضور مقادیر آب کافی، ذوب بخشی در دمای 700 تا 750 درجه سانتیگراد و فشار کمتر از 5 کیلوبار صورت میگیرد. اگرچه، ترکیب شیمیایی کانیهای گارنت و بیوتیت و ایزوپلتهای محاسبه شده برای آنها، نشان میدهد که ذوب بخشی میتوانسته در دماهای کمتر نیز آغاز شود. نمودارهای فازی T-XCO2، T-XO2 و T-XMg آشکار ساختند که افزایش کربن دیاکسید سیال، اکسیژن و نسبت آهن به منیزیم در ترکیب سنگمادر میتوانستهاند سبب رخداد ذوب بخشی در دماهای پائینتر گردند. | ||
| کلیدواژهها | ||
| چاه بازرگان؛ دگرگونی مجاورتی شدید؛ میگماتیت؛ نمودار فازی | ||
| عنوان مقاله [English] | ||
| Determining the conditions and factors affected partial melting in the Chah-Bazargan migmatitic xenoliths (NE Neyriz) using thermodynamic phase diagrams | ||
| نویسندگان [English] | ||
| Abdolnaser Fazlnia1؛ Mirmohammad Miri2؛ Adel Saki2 | ||
| 1Department of Geology, Urmia University, Urmia, Iran | ||
| 2Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz, Iran | ||
| چکیده [English] | ||
| Introduction Migmatites are silisic rocks form in middle to high degree metamorphic territories, at lower to middle continental crust and through water producing reactions (Makrygina, 1977; Brown, 1979; Ashworth, 1985). During intrusion of Chah-Bazargan batholith in the Barrovian-type Qori-Neyriz regional metamorphic rocks at 170 Ma (Fazlnia, 2017), some pieces of these rocks were trapped in the magma and endured intense metamorphism and anatexis. They show stromatic and nebulitic magmatic structures. In the present study, the stable mineral assemblages, conditions, and factors affected partial melting in the Chah-Bazargan migmatites are investigated using phase diagrams and petrographic evidence. Materials and methods The nebulitic migmatites representing the highest metamorphic degree and close and gradational relationships with peraluminous granites in the area were sampled. Petrographic studies were performed on the thin sections to determine mineral assemblages of peak metamorphic condition. The phase diagrams were calculated using whole-rock analyses reported in Fazlnia (2017) and TheriakDomino software (de Capitani, 2010). Results and discussion Petrography The main textures of nebulitic migmatites are granoblastic and poikilioblastic, although porphyroblastic texture can be observed in places. Stabe mineral assemblage cordierite + spinel + garnet + prtithic K-feldspar + plagioclase together with dissolved silimanites and biotites inclusions represent the peak metamorphic condition. Corundum + spinel sympetectic around the cordierites also form in high metamorphic degrees (Whittington et al, 1998). With increasing metamorphic degree, the biotites and cordierites become less and the more, respectively. Phase diagrams The P-T phase diagram was calculated in Na2O-CaO-K2O-FeO-MgO-SiO2-H2O (NCKFMASH) chemical system with fluid as pure water and in excess. According to it, mineral assemblage feldspar + chlorite + biotite + muscovite + quartz was stable at temperatures below 550 °C and represents hornblende hornfels zone of the area metapelitic rocks. Partial melting occurs at 700 that increases up to 750 °C with pressure increasing. The assemblage feldspar + garnet + biotite + cordierite + quartz melt + H2O observed in the xenoliths occurs a pressures below 5 kbar. Although, comparing calculated almandin isopleth for garnet and phlogopite for biotite with chemical compositions of these minerals represented in Fazlnia (2017) indicates that anatexis could onset in lower temperatures. According to the calculated T-XCO2 diagram, the partial melting occurs in lower temperatures with increasing in CO2 content of the fluid. Also, T-XO2 diagram show that presence of sufficient O2 in the environment could decrease the partial melting temperatre to below 700 °C. Moreover, the T-Mg# diagram (Mg# = MgO/MgO+FeO) reveals that low Mg# contents of these rocks (0.2 – 0.3) could trigger anatexis in temperatures below 700 °C. Conclusion Falling of metapelitic xenoliths in Chah-Bazargan batholith producing magma caused intense contact metamorphism and partial melting. In the peak condition, the assemblage cordierite + spinel + K-feldspar + garnet + palgiocasle together with corundum + spinel intergrowth on cordierite formed. Based on the calculated phase diagrams, anatexis occured in temperatures 700 – 750 °C and pressures less than 5 kbar, however, chemical compositions of the garnets and biotites from the xenoliths show that it could onset in lower temperatures. The T-XCO2, T-XO2, T-Mg# diagrams reveal that increasing CO2 and O2 and high FeO contents of the protolith probably triggered anatexis in lower temperatures. | ||
| کلیدواژهها [English] | ||
| Chah-Bazargan, High-grade contact metamorphism, Migmatite, Phase diagram | ||
| مراجع | ||
|
-Alavi, M., 1994. Tectonic of the Zagros orogenic belt of Iran: new data and interpretations: Tectonophysics, v. 229, p. 211-238. -Ashworth, J.R., 1985. Migmatites. First edition, Blackie, Glasgow, 302 p. -Bea, F., 1996. Controls on the trace element composition of crustal melts: Transactions of the Royal Society of Edinburg, Earth Sciences v. 87, p. 133-141. -Berberian, M. and King, G.C.P., 1981. Towards a paleogeography and tectonic evolution of Iran: Canadian Journal of Earth Sciences, v. 18(2), p. 210-265. -Bucholz, C.E., Stolper, E.M., Eiler, J.M. and Breaks, F.W., 2018. A Comparison of Oxygen Fugacities of Strongly Peraluminous Granites across the Archean–Proterozoic Boundary, Journal of Petrology, v. 59 (11), p. 2123-2156. -Brown, M., 1979. The petrogenesis of the St. Malo migmatite belt, Amorican Massif, France: Neues Jahrbuch fur Mineralogie Abhandlungen, v. 135, p. 48-74. -Bucher, K. and Grapes, R., 2011. Petrogenesis of Metamorphic Rocks. Springer-Verlag, Heidelberg, 428 p. -Coggon, R. and Holland T.J.B., 2002. Mixing properties of phengitic micas and revised garnet-phengite thermobarometers: Journal of metamorphic Geology, v. 20, p. 683-696. -De Capitani, C. and Petrakakis, K., 2010. The computation of equilibrium assemblage diagrams with Theriak/Domino software: American Mineralogist, v. 95, p. 1006-1016. -Diener, J., 2014. Low-P-high-T metamorphism of the Aggeneys terrane, Namaqua Metamorphic Complex, South Africa: South African Journal of Geology, v. 117(1), p. 31-48. -Fazlnia, A.N., 2010. Geochemical modeling of partial melting on the Tall-e-Pahlevani migmatitic xenoliths, Shahr-e-Babak: Petrology v. 1, p. 11-26 (in Persian). -Fazlnia, A.N., 2017. Geochemical characteristics and conditions of formation of the Chah-Bazargan peraluminous granitic patches, ShahrBabak, Iran: Geologica Carpathica, v. 68, p. 445-463. -Fazlnia, A.N., Schenk, V., van der Straaten, F. and Mirmohammadi, M.S., 2009. Petrology, geochemistry, and geochronology of Trondhjemites from the Qori complex, Neyriz, Iran: Lithos, v. 112, p. 413-433. -Greenfield, J.E., Clarke, G.L. and White, R.W., 1998. A sequence of partial melting reactions at Mt Stafford, Central Australia. Journal of Metamorphic Geology, v. 16, p. 363-378. -Hassanzadeh, J. and Wernicke, B.P., 2016. The Neotethyan Sanandaj-Sirjan zone of Iran as an archetype for passive margin-arc transitions: Tectonics, v. 35, p. 586-621. -Holland, T.J.B., Baker, J.M. and Powell, R., 1998. Mixing properties and activity-composition relationships of chlorites in the system MgO-FeO-Al2O3-SiO2-H2O: European Journal of Mineralogy, v. 10, p. 395-406. -Jones, K.A. and Brown, M., 1990. High-temperature ‘clockwise’ P-T paths and melting in the development of regional migmatites: an example from southern Brittany, France: Journal of Metamorphic Geology, v. 8, p. 551-578. -Kretz, R., 1983. Symbols for rock-forming minerals: American Mineralogist, v. 68, p. 277-279. -Mahmoudi, S. and Baharifar, A.A., 2018. Phase equilibria and P-T-t path of metapelitic rocks in SE-Hamedan, Sanandaj-Sirjan Zone, Iran: Mineralogy and Petrology, v. 113, p. 135-154. -Makrygina, V.A., 1977. Role of metamorphic zonation in distribution of pegmatites and migmatites of different composition: International Geology Reviews, v. 19, p. 1133-1141. -Milord, I., Sawyer, E.W. and Brown, M., 2001. Formation of diatexite migmatite and granite magma during anatexis of semi-pelitic metasedimentary rocks: an example from St. Malo, France: Journal of Petrology, v. 42, p. 487-505. -Mohajjel, M. and Fergusson, C.L., 2014. Jurassic to Cenozoic tectonics of the Zagros Orogen in northwestern Iran: International Geology Review, v. 56, p. 263-287. -Nyman, M.W., Pattinson, D.R.M. and Ghent, E.D., 1995. Melt extraction during formation of K-feldspar sillimanite migmatites, west of Revelstoke, British Columbia: Journal of Petrology, v. 36, p. 351-372. -Patino Douce, A. and Bread, J.S., 1996. Effects of P, fO2 and Mg/Fe ratio on dehydration melting of model metagreywackes: Journal of Petrology, v. 37, p. 999-1024. -Powell, R. and Holland, T.J.B., 1985. An internally consistent dataset with uncertainties and correlations: 1. Methods and a worked example: Journal of Metamorphic Geology, v. 3, p. 327-342. -Qiu, J. and Qiu, L., 2016. Geochronology and magma oxygen fugacity of Ehu S-type graniticpluton in Zhe-Gan-Wan region, SE China, Chemie der Erde, v. 76, p. 441-448. -Saki, A., Moazzen, M. and Baharifar, A.A., 2012. Migmatite microstructures and partial melting of Hamadan metapelitic rocks, Alvand contact aureole, western Iran: International Geology Review, v. 54, p. 1229-1240. -Sawyer, E.W., 1991. Disequilibrium melting and the rate of meltresiduum separation during migmatitization of mafic rocks from the Grenville Front, Quebec: Journal of Petrology, v. 32, p. 701-738. -Sawyer, E.W., 1996. Melt segregation and magma flow in migmatites: implications for the generation of granite magmas: Transactions of the Royal Society of Edinburg, Earth Sciences, v. 87, p. 85-94. -Sawyer, E.W., 2008a. Atlas of migmatites. Special publication, NRC Research Press, the Canadian Mineralogist, 389 p. -Sawyer, E.W., 2008b. Working with Migmatites: Nomenclature for the Constituent Parts. In Sawyer E.W. (Ed.). Working with Migmatites: Mineralogical Association of Canada, Short Course Series, v. 38, p. 1-28. -Sawyer, E.W., 2014. The inception and growth of leucosomes: microstructure at the start of melt segregation in migmatites: Journal of Metamorphic Geology, v. 32, p. 695-712. -Sepahi, A.A., Jafari, S.R., Osanai, Y., Shahbazi, H. and Moazzen, M., 2018. Age, petrologic significance and provenance analysis of the Hamedan low-pressure migmatites; Sanandaj-Sirjan Zone, west Iran: International Geology Review, v. 61, p. 1446-1461. -Shafaii Moghadam, H., Li, X.H., Stern, R.J., Ghorbani, G. and Bakhshizad, F., 2016. Zircon U–Pb ages and Hf–O isotopic composition of migmatites from the Zanjan–Takab complex, NW Iran: Constraints on partial melting of metasediments: Lithos, v. 240-243, p. 34-48. -Sheppard, S., Occhipinti, S.A. and Tyler, I.M., 2003. The relationship between tectonism and composition of granitoid magmas, Yarlarweelor Gneiss Complex, Western Australia: Lithos, v. 66, p. 133-154. -Spear, F.S., 1993. Metamorphic phase equilibra and pressure-temperature-time paths. Mineralogical Society of America, Washington DC, 799 p. -Stöcklin, J., 1968. Structural history and tectonics of Iran: a review: The American Association of Petroleum Geologists Bulletin, v. 52, p. 1229-1258. -White, R.W., Powell, R. and Clarke, G.L., 2003. Prograde metamorphic assemblage evolution during partial melting of metasedimentary rocks at low pressures: migmatites from Mt. Stafford, central Australia: Journal of Petrology, v. 44, p. 1937-1960. -White, R.W., Powell, R. and Holland, T.J.B., 2007. Progress relating to calculation of partial melting equilibria for metapelites: Journal of Metamorphic Geology, v. 25, p. 511-527. -Whitley, S., Halama, R., Gertisser, R., Preece, K., Deegan, F.M. and Troll, V.R., 2020. Magmatic and metasomatic effects of magma–carbonate interaction recorded in calc-silicate xenoliths from Merapi volcano (Indonesia), Journal of Petrology, v. 61(4), p. 1-38. -Whittington, A., Harris, N. and Bake, J., 1998. Low-pressure crustal anatexis: the significance of spinel and cordierite from metapelitic assemblages at Nanga Parbat, northern Parkistan: Geological Society, London, Special Publications, v. 138, p. 183-198. | ||
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