Document Type : Original Research Paper


Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran


The Kashmar granitoid (42.5 Ma) occurs in NE Central Iran Plate (CIP). It mainly includes felsic metaluminous (ASI ≤ 1) I–type granite and granodiorite plutons. Microprobe analyses show that the Kashmar amphiboles are low in Ti and (Na+K)A contents (all < 0.5 apfu), indicating magnesio–hornblende, a distinct mafic mineral of low–temperature I–type granites. Also, the content of Al2O3 is low, suggesting low–pressure crystallization. The Mg* ratio is high (0.60–0.75) and the AlVI is extremely low (< 0.1 apfu), but Fe3+ is much higher than AlVI, features confirming low–pressure and low–temperature conditions. Utilizing the modern thermo–barometers, the pressures of ≤ 3 kb and average temperature of 655 oC were calculated for Kashmar amphiboles. The attributed log fO2 values are negative, ranging from –16.59 to –19.40 and plotting above the QFM stability. Results of this study propose a thermal boundary of ~700 oC between felsic (~600–700 oC) and mafic (~700–800 oC) low–temperature I–type granites, and reinforce the modern granite subdivision.


Main Subjects

[1] Soltani A. ″Geochemistry and geochronology of I– type granitoid rocks in the northeastern Central Iran Plate″. PhD Thesis, University of Wollongong, Australia (unpubl.), 300 p, 2000. [2] Robinson P., Spear F. S., Schumbacher J. C., Lared J., Klein C., Evans B. W., Doolan B. L., ″Phase relations of metamorphic amphiboles: natural occurrence and theory″: In Veblen D. R. & Ribbe P. H. (eds). Amphiboles: Petrology and Experimental Phase Relations, Mineralogical Society of America, Review in Mineralogy, 9B: pp. 1–227, 1982. [3] Leake B. E., Woolley A. R., Arps C. E. S., Birch W. D., Hawthorne F. C., Kato A., Kisch H. J., Krivovichev V. G., Linthout K., Laird J. Mandarino J. A., Maresch W. V., Nikel E. H., Rock N. M. S., Schumacher J. C., Smith D. C., Stephen N. C. N., Ungaretti L., Whittaker E. J. W., and Youzhi G., ″Nomenclature of amphiboles″: Report of the Subcommittee on Amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names. American Mineralogist, v. 82, pp. 1019–1037, 1997. [4] Leake B. E., Woolley A. R., Birch W. D., Burke E. A. J., Feraris G., Grice J. D., Hawthorne F. C., Kisch H. J., Kerivovichev V. J., Schumacher J. C., Stephenson N. C. N., Whittaker J. W., ″Nomenclature of amphiboles″: Additions and revisions to the International Mineralogical Association’s amphibole nomenclature. American Mineralogist, v. 89, pp. 883–887, 2004. [5] Hammarstrom J. M., Zen E., ″Aluminum in hornblende″: An empirical igneous geobarometer. American Mineralogist, v. 71, pp. 1297–1331, 1986. [6] Johnson M. C., Rutherford M. J., ″Experimentally calibration of the aluminum–in–hornblende geobarometer with application to Long Valley caldera (California) volcanic rocks″. Geology, v. 17, pp. 837–841, 1989. [7] Gribble C. D., ″Rutley’s Elements of Mineralogy″. 27th editions, Unwin Hyman, London 1988. [8] Anderson J. L., Smith D. R., ″The effect of temperature and fO2 on the Al–in–hornblende barometer″. American Mineralogist, v. 80, pp. 549–559, 1995. [9] Schmidt M. W., ″Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al–in–hornblende barometer″. Contribution to Mineralogy and Petrology, v. 110, pp. 304–310, 1992.
[10] Al’meev R. R., Ariskin A. A., Yu. Ozerov A., Kononkova N. N., ″Problems of the stoichiometry and thermobarometry of magmatic amphiboles″: An example of hornblende from the andesites of Bezymyannyi Volcano, eastern Kamchatka, Geochemistry International, v. 40, No. 8 pp. 723738, 2002. [11] Bachmann O. and Dungan M. A., ″Temperature– induced Al–zoning in hornblendes of the Fish Canyon magma, Colorado″. American Mineralogist, v. 87, pp.1062–1076, 2002. [12] Wones D. R., ″Significance of the assemblage titanite + magnetite + quartz in granitic rocks″. American Mineralogist, v. 74, pp. 744–749, 1989. [13] Holland T., Blundy J., ″Non–ideal interactions in calcic amphiboles and their bearing on amphibole–plagioclase the rmometry″. Contribution to Mineralogy and Petrology, v. 116, pp. 433–447, 1994. [14] Stone D., ″Temperature and pressure variations in suites of Archean felsic plutonic rocks, Berens River Area, northwest superior province, Ontario, Canada″. The Canadian Mineralogist, v. 38, pp. 455–470. 2000. [15] Burkhard D. J. M., ″Temperature and redox path of biotite–bearing intrusives: a method of estimation applied to S– and I–type granites from Australia″. Earth and Planetary Science letters, v. 104, pp. 89–98, 1991. [16a] Chappell B. W., ″High– and Low–temperature Granites″. The Ishihara Symposium: Granites and Associated Metallogenesis, GEMOC, Macquarie University, NSW, 2010, Australia, pp. 43, 2004. [16b] Chappell, B. W., ″Towards a unified model for granite genesis″. Transactions of the Royal Society of Edinburgh: Earth Sciences, v. 95, pp.1-10, 2004. [17] Anderson J. L., ″Regional tilt of the Mount Stuart Batholith, Washington, determined using Al–in– hornblende barometry″: Implications for northward translation of Baja British Columbia: Discussion and Reply. Geological Society of America Bulletin, v. 109, pp. 1223–1227, 1997. [18] Femenias O., Mercier Jean–Claude C., Nkono C., Diot H., Berza T., Tatu M., Demaiffe D., ″Calcic amphibole growth and compositions in calc– alkaline magmas: Evidence from the Mortu Dike Swarm (Southern Carpathians, Romania)″. American Mineralogist, v. 91 pp.73–81, 2006. [19] Popp R. K., Hibbert H. A., Lamb W. M., ″Oxy– amphibole equilibria in Ti–bearing calcic amphiboles: Experimental investigation and petrologic implications for mantle–derived amphiboles. ″ American Mineralogist, v. 91 pp.54– 66, 2006 .[20] Mesto E., Schingaro E., Scordari F., Ottolini L., ″An electron microprobe analysis, secondary ion mass spectrometry and single–crystal X–ray diffraction study of phlogopites from Mt. Vulture,
Potenza, Italy: Consideration of cation partitioning″. American Mineralogist, v. 91 pp. 182–190, 2006.