The mechanism of fibrolite formation in the contact aureole of Mashhad granite

Abstract

The mechanism of fibrolite formation in metapelitic rocks of the contact aureole of Mashhad granite is examined in this study. According to textural features, fibrolite considered to be disharmonious. Textural evidence strongly suggests that most of the fibrolite in this aureole are formed by decomposition of biotite. Fibrolite produced late in the thermal history of the aureole through a reaction involving acidic volatiles emanating from the adjacent intrusion. Textural evidence suggest that the fibrolite formed at temperatures within the andalusite stability field in the aureole investigated in this study.

Keywords


[1] Tozer C.F., "The mode of occurrence of sillimanite in the Glen District, Co. Donegal. Geological Magazine", 92, 310-320. 1955.

[2] Vernon R. H., Flood R. H., D,Arcy., "Sillimanite and andalusite produced by base-cation leaching and contact metamorphism of felsic igneous rocks. Journal of Metamorphic Geology". 5, 439-450. 1987.

[3] Kerrick D. M., "Fibrolite in contact aureoles of Donegal, Ireland", American Mineralogist. 72, 240-254. 1987.

[4] Homam S. M., Boyle A. P., Atherton M. P., "Syn- to post-kinematic fibrolite-biotite intergrowth in the Ardara aureole NW Ireland", Journal of Sciences Islamic Republic of Iran. 13, 327-337. 2002.

[5] Wintsch, R. P., Andrews M. S., "Deformation induced growth of sillimanite: “stress” mineral revisited", Journal of Geology. 96, 143-161. 1988.

[6] Kerrick D.M., "The Al2SiO5 polymorphs." Rev. Mineral., 22, 406p. 1990.

[7] موذن م.، همام م.، قادری زفره ع.، "بررسی مسئله فیبرولیت و شرایط تشکیل آن در هاله دگرگون گابرودیوریت چاه قند، شمال شرقی نیریز"، مجله بلورشناسی و کانی‌شناسی ایران شماره یک بهار و تابستان 1385 ص 128-114.

[8] Alavi M., "Sedimentary and structural characteristics of the Paleo-Tethys remnants in northeastern Iran.", Geological Society of America Bulletin, V. 103, p. 983-992. 1991

[9] Majidi B., "The geochemistry of ultrabasic and basic lava flow occurrences in northeast Iran", In Geodynamic project (geotraverse) in Iran. Geological Survey of Iran Report No. 51, p. 463-477. 1983.

[10] Majidi B., "The ultrabasic lava flows of Mashhad, NE Iran. Geological Magazine", V. 118, P. 49-58. 1981.

[11] Alberti A., Moazzez S., "Plutonic and metamorphic rocks of the Mashhad area (Khorasan, north-eastern Iran).", Bulletine Societa Geologica Italiana, V. 93, p. 1157-1196. 1974.

[12] Alberti A., Nicoletti M., Petrucciani C., "K/Ar ages of mica of Mashhad granite (Khorasan, NE







Iran).", Periodico di Mineralogia. V. 42, p. 483-493. 1973.

[13] Vernon R. H., Flood R. H., "Interpretation of metamorphic assemblages containing fibrolitic sillimanite", Contribution to Mineralogy and Petrology. 59, 227-235. 1977.

[14] Vernon R. H., "Growth and concentration of fibrous sillimanite related to heterogeneous deformation in K-feldspar-sillimanite metapelites", J. of Metamorphic Geology. 5, 51-68. 1987.

[15] Chinner G.A., "The origin of sillimanite in Glen Clova, Angus.", J. Petrol., 2, 312-323. 1961.

[16] Speer J.A., "Metamorphism of the pelitic rocks of the Snyder group in the contact aureole of the Kiglapait layered intrusion", Labrador: Effects of buffering partial pressures of water. Canadian. J. Earth Sci., 19, 1888-1909. 1982.