Petrography and mineral chemistry of layered pegmatite-aplite dykes from east of Boroujerd

Abstract

Pegmatite-aplite dykes from north east of Lorestan Province is located about 25 km east of Boroujerd city and consists of three major zones, from outside to inside including graphic, layered and core zone that obviously shows the effect of fractional crystallization in pegmatites. Microprobe analysis performed on minerals (tourmaline, plagioclase and muscovite) from each three zones. Tourmalines from marginal zone have schorlite to foitite composition and tourmalines from layered zone have foitite composition that both of them lie in magmatic tourmalines category. These tourmalines plotted on FeO/FeO+MgO vs. MgO diagram have Fe# between 0.8 to 1 indicate that  they formed in magmatic conditions and external hydrothermal fluids did not effect  in formation of Tourmalins. Compositions of analyzed plagioclases from all three zones are rich in albite and the average compositions are; marginal zone (Ab98.05), layerd zone (Ab98.78) and core zone (Ab98.43), indicating a high degree of fractionation in source magma.

Keywords


[1] Fenn P.M., “The nucleation and growth of alkali feldspars from hydrous melts”, Canadian Mineralogist 15 (1977) 135-161.

[2] London D., “Pegmatites”, Canadian Mineralogist Special Publication 10 (2008) 368.

[3] Rockhold J.R., Nabelek P.I., Glascock M.D., “Origin of rhythmic layering in the Calamity Peak satellite pluton of the Harney Peak Granite, South Dakota: the role of boron”, Geochimica et Cosmochimica Acta 51 (1987) 487–496.

[4] Kleck W.D., Foord E.E., “The chemistry, mineralogy, and petrology of the George Ashley Block pegmatite body”, American Mineralogist 84 (1999) 695–707.

[5] احمدی خلجی ا.، "پترولوژی توده گرانیتوئیدی بروجرد"، رساله دکتری، دانشکده علوم، دانشگاه تهران (1385).

[6] میرسپهوند ف.، طهماسبی ز.، شاهرخی س.، احمدی خلجی ا.، خلیلی م.، "ژئوشیمی و تعیین خاستگاه تورمالین‌های منطقه‌ی بروجرد"، مجله بلورشناسی و کانی شناسی ایران، شماره2 (1391) ص 281 – 292.

[7] Ahmadi Khalaji A., Esmaeily D., Valizadeh M.V., Rahimpour-Bonab H., “Petrology and geochemistry of the granitoid complex of Boroujerd, Sanandaj-Sirjan Zone, Western Iran”, Journal of Asian Earth Sciences 29 (2007) 859–877.

[8] Masoudi F., “Contact metamorphism and pegmatite development in the region S.W of Arak- Iran”, Thesis, University of Leeds. England. (1997) 321p.

[9] Masoudi F., Yardley B.W.D., Cliff R.A., “Rb-Sr geochronology of pegmatites, plutonic rocks and a hornfels in the south- west of Arak, Iran”, Journal of Sciences, Islamic Republic of Iran 13(3) (2002) 249-254.

[10] Afsharianzadeh A.M., Sahbaei M., “1/250000 map of Khorramabad, Geological Survey of Iran (in Persian)”, (1992).

[11] واعظی‌پور م.ج.، اقلیمی ب.، "یافته‌های نوین در نهشته‌های ژوراسیک ناحیه لکان (چهار گوش گلپایگان)"، گزارش داخلی، سازمان زمین‌شناسی و اکتشافات معدنی کشور(1363).

[12] Kertz R., ˝Symbol for rock- forming minerals˝, American Mineralogist 68(1983)277-9.

[13] London D., “The origin of primary textures in granitic pegmatites”, Canadian Mineralogist 47 (2009) 697–724.

[14] Pesquera A., Torres-Ruiz J., Gil-Grespo P. P., Velilla N., “Chemistry and genetic implications of tourmaline and Li-F-Cs micas from the Valdeflores area (Caceres, Spain)”, American Mineralogist 84 (1999) 55-69.

[15] Cameron E.N., Jahns R.H., McNair A.H., Page L.R., “Internal structure of granitic pegmatites”, Economic Geology Monograph 2 (1949) 115.

[16] Jahns R.H., “The study of pegmatites”, Economic Geology, 50th Anniversary (1955) 1025–1130.

[17] Jahns R.H., Tuttle O.F., “Layered pegmatite–aplite intrusive”, Mineralogical Society of America Special Paper 1 (1963) 78–92.

[18] Jahns R.H., “Internal evolution of pegmatite bodies”, Mineralogical Association of Canada Short Course Handbook, vol. 8 (1982) 293-327.

[19] Webber K.L., Falster A.U., Simmons W.B., Foord E.E., “The role of diffusion controlled oscillatory nucleation in the formation of line rock in pegmatite–aplite dikes”, Journal of Petrology 38 (1997) 1777–1791.

[20] London D., “A petrologic assessment of internal zonation in granitic pegmatites”, Lithos 184–187 (2014) 74–104.

[21] Van hinsberg V.J., Henry D.J., Marschall H.R., “Tourmaline an ideal indicator of its host environment”, The Canadian mineralogist, 49 (2011) 1-16.

[22] Slack J.F., Palmer M.R., Stevens B.P.J., Barnes R.G., “ Origin significance of tourmaline-rich rocks in the Broken Hill district, Australia”, Economic Geology 88 (1993) 505-541.

[23] Hawthorne F.C., Henry D.J., “Classification of the minerals of the tourmaline group”, European Journal of Mineralogy 11 )1999( 201-215.

[24] Trumbull R.B., Chaussidon M., “Chemical and boron isotopic composition of megmatic and hydrothermal tourmalines from the Sinceni granite-pegmaite system in Swaziland”, Chemical Geology 153 (1999) 125-137.

[25] London D., Manning D.A.C., “Chemical Variation and Significance of tourmaline from southwest England”, Economic Geology 90 (1995) 495-519.

[26] Pesquera A., Velasco F., “Mineralogy, geochemistry and geological significance of tourmaline-rich rocks from the Paleozoic Cinco Villas massif (western Pyrenees, Spain)”, Contributions to Mineralogy and Petrology 129 (1997) 53– 74.

[27] Pirajno F., Smithies R.H., “The FeO/ (FeO+MgO) ratio of tourmaline: A useful indicator of spatial variations in granite-related hydrothermal mineral deposits”, Journal of Geochemical Exploration 42 (1992) 371-381.

[28] Deer W.A., Howie A., Zussman J., “An introduction to the rock-forming minerals”, Long man, London (1991) 528p.

[29] Cavarretta G., Puxeddu M., “Schorl-Dravite- Ferridravite Tourmalines Deposited by Hedrothermal Magmatic Fluids during Early Evolution of the Larderico Geothermal Field”, Italy. Economic Geology 85 (1990) 1236-1251.

[30] Henry D.J., Guidotti Ch.V., “Tourmaline as petrogenetic indicator mineral: an example from staurolite-grade metapelites of NW Mains”, American Mineralogist 70 (1985) 1-15.