کانی‌شناسی، دما – فشارسنجی و تعیین سری ماگمایی مجموعه آذرین نفوذی نطنز

نویسندگان

1 دانشگاه تبریز

2 دانشگاه پیام نور اصفهان

چکیده

توده­های آذرین نفوذی نطنز در شمال اصفهان و در امتداد کمربند ماگمایی ارومیه-دختر رخنمون یافته­اند. بر اساس بررسی­های سنگ­شناختی این توده­ها از گابرو، دیوریت، کوارتزدیوریت، گرانودیوریت، کوارتز مونزونیت و مونزوگرانیت تشکیل یافته­اند، و از نظر سری ماگمایی آهکی- قلیایی و از گرانیتوئیدهای نوع I هستند. داده­های حاصل از آنالیز ریزپردازشی حاکی از آن است که ترکیب الیوین موجود در گابروها در حد Fo67-71  است و پیروکسن­های منطقه از نوع آهن، منیزیم و کلسیم­دار (فقیر از Na) هستند. آمفیبول­ها نیز از نوع کلسیک و بیشتر در رده مگنزیوهورنبلند قرار می­گیرند. پلاژیوکلازهای منطقه در گستره­ای از ترکیبAn11.43   تا An 92.37  قرار دارند. بیوتیت­های تجزیه شده بیشتر در گستره بیوتیت­های غنی از منیزیم قرار می­گیرند. با استفاده از روش فشار سنجی Al در هورنبلند، فشاری که برای تشکیل توده­های آذرین نفوذی منطقه برآورد می­شود در حدود 2 کیلوبار است. همچنین دمای بدست آمده برای تشکیل کانی­های آمفیبول و پیروکسن، با استفاده از روش­های مختلف، نسبتاً پایین (در حدود °C 800، در دیوریت) است که احتمالاً دمای مربوط به برقراری دوباره تعادل بین کانی­ها در مراحل آخر ماگمایی و یا پس از ماگمایی است.

کلیدواژه‌ها


عنوان مقاله [English]

Mineralogy, geothermobarometry and magmatic series of Natanz plutonic complex

چکیده [English]

The Natanz plutonic complex is located in north of Isfahan and in the Orumieh – Dokhtar magmatic belt. Based on petrographic studies, the Natanz complex is composed of six rock types, which are granodiorite, quartz-diorite, diorite, gabbro, quartz-monzonite and granite monzogranit. The intrusive rocks of Natanz are related to the calc-alkaline magmatic series and I-type granitoids. These rocks are mainly composed of plagioclase, quartze, amphibole, alkali-feldspar, biotite, and pyroxene. The composition of olivine is Fo67-70. Pyroxene is Na-poor. The Composition of clinopyroxenes is in the diopside – augite range and orthopyroxenes are enstatite. All clinopyroxene analyses display compositional differences between cores and rims. Calcic amphibole with magnesiohornblende composition is one of the mafic minerals in the rocks. Composition of plagioclase is An11 (the minimum value in granite) to An92 (the maximum value in gabbro) and in some samples this mineral has normal zoning. Micas are Mg-rich biotite. Application of Al in hornblende barometry indicates a pressure of » 2 kbar for the intrusion. Thermometry yields low temperatures, which probably reflects late stage, post - magmatic re-equilibration of the minerals.

کلیدواژه‌ها [English]

  • Mineral chemistry
  • geothermometry
  • geobarometry
  • calc-alkaline
  • Orumieh – Dokhtar
  • Natanz
[1] هنرمند، م.، "مطالعات پتروگرافی، پترولوژی و پتروژنز توده‌های نفوذی غرب و جنوب غرب نطنز با نگرشی بر تعیین شرایط ترمودینامیکی تبلور"، پایان نامه کارشناسی ارشد، دانشگاه تبریز، 141 صفحه (1385).

[2] White, A.J.R. and Chappll, B.W., "Ultrametamorphism and granitoid genesis", Tectonophysics 43 (1977) 7-22.

[3] Irvine, T.N. and Baragar, W.R.A., "A guide to the chemical classification of the common volcanic rocks", Canadian Journal of Earth Science 8(1971) 523-548.

[4] Pearce J.A., “Source and setting of granitic rocks”, Episode, 19 (1996) 120-125.

[5] Pourhoseini F., (1981) Ph.D (Cambridge.U.K.) "Petrogenesis of Iranian plutons, a study of the Natanz and Bazman Intrusive complexes", Geological survey of Iran, Report No. 53, 1983.

[6] Morimoto N., Fabries J., Ferguson A.K., Ginzburg I.V., Ross M., Seifert F.A., Zussman J., Akoi K., Gottardi G., "Nomenclature of pyroxenes". Mineralogical Magazine, 52 (1988) 535-550.

[7] Droop, G.T.R., "A general equation for estimating Fe3+ Concentration in ferromanesian silicates and oxides from microprobe analysis, using stochiometric criteria", Mineralogical Magazine 51 (1987) 431-435.

[8] Deer W.A., Howie R.A., Zussman J., "An introduction to the Rock – forming minerals", Longman, London, (1991) 528 p.

[9] Mordick B.E., Glazner A.F., "Clinopyroxene thermobarometry of basalts from the Coso and Big Pine volcanic fields, California", Contributions to Mineralogy and Petrology 152 (2006) 111–124.

[10] PePiper G., "Zoned Pyroxenes from Shoshonite Lavas of esbos, Greece: Inferences concerning Shoshonite Petrogenesis", Journal of petrology, 25 (1984). Part 2, 453-4721.

[11] Bence A.E., Papike J.J., Ayuso R.A., "Petrography of Atlantic island arcs", Bulletin of volcanology 32 (1975) 189-206.

[12] Schweitzer E.L., Papike J, J., bence A.E., "Statitical analysis of clinopyroxenes from deep-sea basalts", American Mineralogist 64 (1979) 501-513.

[13] Cameron M., Papike J.J., "Structural and chemical variations", American Mineralogist, 66 (1981) 1-50.

[14] Zhu Y., Ogasawara Y., "Clinopyroxene phenocrysts (with green salite cores) in trachybasalts: implications for two magma chambers under the Kokchetav UHP massif, North Kazakhstan". Journal of Asian Earth Sciences 22 (2004) 517–527.

[15] LeBas N.J., "The role of aluminium in igneous clinopyroxenes with relation to their parentage", American Journal of Science 260 (1962) 267-288.

[16] Leterrier J., Maury R. C., Thonon P., Girard D., Marchal M., "Clinopyroxene composition as a method of identification of the magmatic affinities of paleo-volcanic series", Earth and Planetary Science Letters 59 (1982) 139-154.

[17] Nosova A. A., Sazonova L. V., Narkisova V. V., Simakin S. G., "Minor elements

in clinopyroxene from Paleozoic volcanics of the Tagil Island Arc in the Central Urals", Geochemistry International 40 (2002): 219-232.

[18] Anderson JL., "Status of thermobarometry in granitic batholiths", Trans Roy SocEdinb: Earth Science 87 (1997) 125-138.

[19] Ramsay R.R., "Geochemistry of Diamond Indicator Minerals". PhD Thesis, University of Western Australia, Perth, WA. 1992.

[20] Thompson R.N., "Some high-pressure pyroxenes". Mineralogical Magazine 39(1974) 768-787.

[21] Wass, S.Y., Multiple origins of clinopyroxenes in alkali basaltic rocks, Lithos 12 (1979) 115–132.

[22] Leake B.E., Woolley A.R., Birch W.c., Gilbert M.C., Grice J.D., Hawthone F.C., Kato A., Kisch H.J., Krivovicher V.G., Linthout K., Laird J., Mandarino J., "Nomenclature of amphiboles: Report of the subcommittee on amphiboles of the International Mineralogical Association Commission on new mineral and mineral names", Mineralogical Magazine 61 (1997) 295-321.

[23] Spear F.S., "Metamorphic phase equilibria and pressure – temperature – time paths" Mineralogical Society of America, Washington, (1993) 799.

[24] Jarrar GH, "Mineral chemistry in dioritic hornblendite from Wadi Araba, Southwest Jordan", Journal of African Earth Sciences 26 (1998) 285-295.

[25] Anderson JL., Smith D.R., "The effects of temperature and ƒ02 on the Al-in-hornblende barometer". Amarican Mineralogist 80 (1995) 549-559.

[26] Stein E., Dietl C., "Hornblende thermobarometry of granitoids from the Central Odenwald (Germany) and their implications for the geotectonic development of the Odenwald", Mineralogy and Petrology 72 (2001) 185-207.

[27] Schmidt M.W., "Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in hornblende barometer". Contributions to Mineralogy and Petrology 110 (1992) 304-310.

[28] Johnson M.C., Rutherford M.J., "Experimental calibration of the aluminum-in-hornblende geobarometer with application to Long Valley Caldera (California) volcanic rocks" Journal of Geology 17 (1989) 837-841.

[29] Blundy J.D., Holland T.J. B., "Calcic amphibole equilibria and a new amphibole-plagioclase geothermometer", Contributions to Mineralogy and Petrology 104 (1990) 208-224.

[30] Wones D.R., “Significance of the assemblage titanite + mognetitet + quartz in granitic rocks”, 74 American Mineralogist, (1989) 744-749.

[31] Coltorti M., Bonadiman C., Faccini B., Grégoire M., O'Reilly S.Y., Powell W., "Amphiboles from suprasubduction and intraplate lithospheric mantle", 99 Lithos (2007)68-84.

[32] Pietranik A., Koepke J., Puziewicz J., "Crystallization and resorption in plutonic plagioclase: Implications on the evolution of granodiorite magma (Gesiniec granodiorite, Strzelin Crystalline Massif, SW Poland)", 86 Lithos (2006) 260-280.

[33] Tegner C., "Iron in plagioclase as a monitor of the differentiation of the Skaergaard intrusion", Contribution to Mineralogy Petrology 128 (1997) 45-51.

[34] Smith JV., "Phase equilibria of plagioclase", In: Ribbe PH (ed) Feldspar mineralogy, 2nd edn Mineralogical Society of America, Washington DC, (Reviews in Mineralogy vol. 2) (1983) 223-239.

[35] Smith J.V., Brown W.L., "Feldspar minerals. Crystal structures, physical, chemical and microtextural properties", Springer, Berlin-Heidelberg-New York, (1988) 828p

[36] Foster M.D., "Interpretation of the composition of trioctahedral micas". U.S. Geological Survey, Prof. Pap, 354 (1960) 11-49.

[37] Abdel – Rahman A. M., "Nature of biotites from alkaline, Calc-alkaline and peraluminous magmas", Journal of Petrology 35 (1994) 525-541.

[38] Spear J.A., "Mica in igneous rocks". In: Micas, Bailey, S.W. (ed); Mineralogical Society of America, Review in Mineralogy 13 (1984) 299-356.

[39] Nachit H., "Contribution a I é tude analytique et experimental des biotite des granitoids Applications typologiques", These de Doctorat De Ľ univesité de Bretagne accidental (1986) 236p.

[40] Helmy H.M., Ahmed A.F., El Mahallawi M.M., Ali S.M., "Pressure, temperature and oxygen fugacity conditions of calc-alkaline granitoids, Eastern Desert of Egypt, and tectonic implications"Journal of African Earth Sciences 38 (2004) 255–268.