Petrography and mineral chemistry of the Eocene granodiorites in the Toveireh area (Southwest of Jandaq, Isfahan province)

Document Type : Research Article

Authors

• Masumeh Sargazi
• Ghodrat Torabi

Isfahan

10.22067/econg.v10i2.60825

Abstract

Introduction
Granitoids are the most common igneous rocks that are found in all parts of the continental crust and play an important role in the formation and evolution of the Earth’s continental crust (Clarke, 1992). Granitoid plutons contain useful information on factors and processes related to their generation and differentiation (Castro, 2013). The wide range of sources and processes that may be involved in the formation of granitoids is reflected in their compositional range. Although yet there is a long way to achieve a consensus about the origin of granite, different interpretations of the geochemical granitoid data represents geological understanding of the complexities of these rocks.
Large parts of Iran and Central - East Iranian Microcontinent (CEIM) structural zone have suffered from the Eocene granitoid magmatism. Toveireh granitoid intrusive body cropped out in the southwest of the Jandaq city (NE of Isfahan Province) and is one of the Eocene granitoid bodies. It is hoped that this mineralogical and petrological research will be useful in understanding the nature of Eocene acidic magmatism of Central Iran.
 
Material and methods
Chemical analyses of minerals in the Toveireh granodiorites were carried out by a JEOL JXA-8800R (WDS) electron probe micro-analyzer (EPMA) at the Cooperative Center of Kanazawa University, Kanazawa, Japan. The analyses were performed under an accelerating voltage of 20 kV and a beam current of 20 nA with a counting time limit of 40 seconds. Natural minerals and synthetic materials were used as standards. The ZAF program was used for data correction. The amounts of Fe2+ and Fe3+ contents of minerals were estimated by assuming ideal mineral stoichiometry in structural formula. Mineral abbreviations in petrographic photomicrographs and tables are taken from Whitney and Evans (2010).   
 
Results and discussion
Petrographic studies show that the Middle Eocene Toveireh granitoid intrusive consists of granodiorite and granite. Granodiorites are coarse grained, mesocratic and have microgranular mafic enclaves in hand specimen. They are composed of plagioclase, amphibole, quartz, orthoclase and biotite. Accessory minerals are zircon, apatite, sphene and magnetite. Chlorite, actinolite, epidote and sericite are present as the secondary minerals. In the study area, the most dominant texture of the granodiorites are granular but graphic, perthite, anti-perthite, anti-rapakivi textures are common. The plagioclase (An0.8-48) occurs mainly as medium to coarse grains, subhedral, with zoning and polysynthetic twinning that represent varying degrees of saussuritization. Quartz occurs commonly as medium to fine anhedral grains. Graphic texture intergrowths of quartz and feldspars are present. Graphic texture possibly indicate rapid and simultaneous crystallization of quartz and K–feldspar from an under-cooled liquid at shallow depths (Clarke, 1992; Barker, 1983). Hornblende is present as subhedral to anhedral grains and in some cases partly altered to chlorite and actinolite. Biotites are subhedral and sometimes altered to chlorite, titanite and epidote. Based on mineral chemistry data, amphiboles in the investigated plutons are calcic in composition and classify as magnesio-hornblende and actinolite. Amphiboles are characterized by Mg# 0.67 to 0.47 and present geochemical features of subduction zone-related amphiboles. Biotite is characterized by variable and high Fe contents, with Fe# [Fe2+/(Fe2+ + Mg)] ratios between 0.52 to 0.60. Using the nomenclature scheme of Foster (1960), they are Mg-biotite, and have composition range of the calc-alkaline granites among the different granitoid suites in discriminative trend defined by Abdel-Rahman (1994). Chlorites are brunsvigite in composition and have negligible K2O and TiO2 but show similar Fe/(Fe+Mg) ratios with amphibole and biotite. Therefore, it can be concluded that they are alteration products of mafic minerals. Chlorite alteration temperature is estimated to be 245 to 262°C from chlorite geothermometry. The chemistry of hornblende and biotite imply that Toveireh granodiorites have I-Type nature and are products of crust-mantle, mixed-source magma crystallization. Barometry calculations of amphiboles indicate that these rocks were emplaced at an average pressure of 1-1.5 kbars corresponding to approximately 3.5-6 Km depth. Plagioclase-amphibole and biotite thermometry suggests an equilibrium temperature of 700 to 800°C. Estimation of Oxygen fugacity by Fe# of amphibole and biotite indicate high value of Oxygen fugacity (+1< ∆FQM < +2.0) and suggest that the Toveireh granitoids belong to the magnetite-series of granites. Petrography and mineral chemistry of the studied rocks indicated their subduction-related tectonic setting.
 
Acknowledgments
The authors thank the University of Isfahan and Kanazawa University for financial supports and laboratory facilities.
 
References
Abdel-Rahman, A., 1994. Nature of biotites from alkaline, calcalkaline and peraluminous magmas. Journal of Petrology, 35(2): 525–541.
Barker, D.S., 1983. Igneous rocks. Prentice Hall, New Jersey, 417 pp.
Castro, A., 2013. Tonalite –granodiorite suites as cotectic systems: A review of experimental studies with applications to granitoid petrogenesis. Earth-Science Reviews, 124: 68–95.
Clarke, D.B., 1992. Granitoid Rocks. Chapman and Hall, London, 283 pp.
Foster, M.D., 1960. Interpretation of the composition of the trioctahedral micas. United States Geological Survey Professional Paper, 354(B): 11-49.
Whitney, D.L. and Evans, B.W., 2010. Abbreviation for names of rock-forming minerals. American Mineralogist, 95(1): 185–187.

Keywords

• I-type granitoid
• Granodiorite
• Mineral chemistry
• Thermobarometry
• eocene
• Toveireh
• Jandaq

20.1001.1.20087306.1397.10.2.7.2

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References

Abdel-Rahman, A., 1994. Nature of biotites from alkaline, calcalkaline and peraluminous magmas. Journal of Petrology, 35(2): 525–541.

Aganabati, A., 2004. Geology of Iran. Geological Survey of Iran, Tehran, 586 pp. (in Persian)

Ague, J.J., 1997. Thermodynamic calculation of emplacement pressures for batholithic rocks, California: Implications for the aluminum-inhornblende barometer. Geology, 25(6): 563–566.

Aistov, L., Melanikov, B., Krivyakin, B., Morozov, L. and Kiristaev, V., 1984. Geology of the Khur area, Central Iran. Geological Survey of Iran, Tehran, Report 20, 131 pp.

Anderson, J.L., 1996. Status of thermobarometry in granitic batholiths. Earth and Environmental Science Transactions of The Royal Society of Edinburgh, 87(1-2): 125-138.

Anderson, J.L., Barth, A.P. and Mazdab, J.L.W.F., 2008. Thermometers and thermobarometers in granitic systems. Reviews in Mineralogy and Geochemistry, 69(1): 121–142.

Anderson, J.L. and Smith, D.R., 1995. The effects of temperature and ƒO2 on the Al-in-hornblende barometer. American Mineralogist, 80(5–6): 549–559.

Bahktiyari, S., 2005. Atlas of Iran Road 1:1000000. The Institute of Geography and Cartography Gitashenasi of Iran, Tehran, 256 pp. (in Persian)

Barker, D.S., 1983. Igneous rocks. Prentice Hall, New Jersey, 417 pp.

Castro, A., 2013. Tonalite –granodiorite suites as cotectic systems: A review of experimental studies with applications to granitoid petrogenesis. Earth-Science Reviews, 124: 68–95.

Chappell, B.W. and White, A.J.R., 1974. Two contrasting granite types. Pacific Geology, 8:173–174.

Chappell, B.W. and White, A.J.R., 2001. Two contrasting granite types: 25 years later. Australian Journal of Earth Sciences, 48(4): 489–499.

Chappell, B.W., White, A.J.R. and Wyborn, D., 1987. The importance of residual source material (restite) in granite petrogenesis. Journal of Petrology, 28(6): 11–38.

Clarke, D.B., 1992. Granitoid Rocks. Chapman and Hall, London, 283 pp.

Clemens, J.D., Holloway, J.R. and White, A.J.R., 1986. Origin of an A-type granite: experimental constraints. American Mineralogist, 71(3–4): 317–324.

Clemens, J.D. and Stevens, G., 2012. What controls chemical variation in granitic magmas? Lithos, 135(1): 317–329.

Clowe, C.A., Popp, R.K. and Fritz, S.J., 1988. Experimental investigation of the effect of oxygen fugacity on ferric-ferrous ratios and unit-cell parameters of four natural clinoamphiboles. American Mineralogist, 73(1–2): 487–499

Collins, W.J., Beams, S.D., White, A.J.R. and Chappell, B.W., 1982. Nature and origin of A-type granites with particular reference to southeastern Australia. Contributions to Mineralogy and Petrology, 80(2): 189–200.

Coltorti, M., Bonadiman, C., faccini, B., Gregoire, M., O'Reilly, S.Y. and Powell W., 2007. Amphiboles from suprasubduction and intraplate lithospheric mantle. Lithos, 99(1–2): 68–84.

Deer, W.A., Howie, R.A. and Zussman, J., 1991. An Introduction to Rock forming Minerals. Longman, London, 969 pp.

DePaolo, D.J., 1981. Trace element and isotopic effects of combined wallrock assimilation and fractional crystallization. Earth and Planetary Science Letters, 53(2): 189–202.

Elliston, J.N., 1984. Rapakivi texture: an indication of the crystallization of hydrosilicates, II. Earth–Science Reviews, 22(1): 1–99.

Foster, M.D., 1960. Interpretation of the composition of the trioctahedral micas. United States Geological Survey Professional Paper, 354(B): 11-49.

Frost, B.R., Barnes, C.G., Collins, W.J., Arculus, R.J., Ellis, D.J. and Frost, C.D., 2001. A geochemical classification for granitic rocks. Journal of Petrology, 42(11): 2033–2048.

Frost, C.D. and Frost, B.R., 1997. Reduced rapakivi-type granites: the tholeiite connection. Geology, 25(7): 647–650.

Frost, C.D. and Frost, B.R., 2011. On ferroan (A-type) granitoids: their compositional variability and modes of origin. Journal of Petrology, 52(1): 39–53.

Giret, A., Bonin, B. and Leger, J.M., 1980. Amphibole compositional trends in oversaturated and undersaturated alkaline plutonic ring complexes. The Canadian Mineralogist, 18(4): 481–495.

Hammarstrom, J.M. and Zen, E., 1986. Aluminum in hornblende: An empirical igneous geobarometer. American Mineralogist, 71(11–12): 1297–1313.

Helmy, H.M., Ahmed, A.F., El Mahallawi, M.M. and Ali, S.M., 2004. Pressure, temperature and oxygen fugacity conditions of calc-alkaline granitoids, Eastern Desert of Egypt, and tectonic implications. Journal of African Earth Sciences, 38(3): 255–268.

Henry, D.J., Guidotti, C.V. and Thomson, J.A., 2005. The Ti-saturation surface for low-to-medium pressure metapelitic biotite: Implications for Geothermometry and Ti-substitution Mechanisms. American Mineralogist, 90(2–3): 316–328.

Hey, M.H., 1954. A new review of the chlorites. Mineralogical Magazine, 30(224): 277–292.

Hibbard, M.J., 1995. Petrography to petrogenesis. Prentice Hall, New Jersey, 587 pp.

Holland, T. and Blundy, J., 1994. Non-ideal interactions in calcic amphiboles and their bearing on amphibole plagioclase thermometry. Contributions to Mineralogy and Petrology, 116(4): 433–447.

Hollister, L.S., Grissom, G.C., Peters, E.K., Stowell, H.H. and Sisson, V.B., 1987. Confirmation of the empirical correlation of Al in hornblende with pressure of solidification of clac-alkaline plutons. American Mineralogist, 72(3–4): 231–239.

Holton, T., Jamtveit, B. and Meakin, P., 2000. Noise and oscillatory zoning of minerals. Geochimica et Cosmochimica Acta, 64(11): 1893–1904.

Hyndman, D.W., 1985. Petrology of Igneous and Metamorphic Rocks. McGraw- Hill Book Company, New York, 786 pp.

Jarrar, G.H., 1998. Mineral chemistry in dioritic hornblendite from Wadi Araba, southwest Jordan. Journal of African Earth Sciences, 26(2): 285–295.

Jiang, C.Y. and An, S.Y., 1984. On chemical characteristics of calcic amphiboles from igneous rocks and their petrogenesis significance. Journal of Mineralogy and Petrology, 33(1): 1–9.

Jiang, Y.H., Jiang, S.Y., Ling, H.F., Zhou, X.R., Rui, X.J. and Yang, W.Z., 1994. Petrology and geochemistry of shoshonitic plutons from the western Kunlun orogenic belt, Xinjiang, northwestern China. Journal of Petrology, 35(2): 525–541.

King, P.L., Chappell, B.W., Allen, C.M. and White, A.J.R., 2001. Are A-type granites the high‐temperature felsic granites? Evidence from fractionated granites of the Wangrah Suite. Australian Journal of Earth Sciences, 48(4): 501–514.

Kranidiotis, P.Y. and MacLean, W.H., 1987. Systematics of chlorite alteration at the Phelps Dodge massive sulfide deposit, Matagami, Quebec. Economic Geology, 82(7): 898–911.

Leake, B.E., Woolly, A.R., Arps, C.E.S., Birch, W.D., Gilbert, M.C., Grice, J.D., Hawthorne, F.C., Kato, A., Kisch, H.J., Krivovichev, V.G., Linthout, K., Laird, J., Mandarino, J., Maresch, W.V., Nickel, E.h., Rock, N.M.S., Schmucher, J.C., Smith, D.C., Stephenson, N.C.N, Unungaretti, L., Whittaker, E.J.W. and Youzhi, G., 1997. Nomenclature of Amphiboles, report of the subcommittee on amphiboles of the international mineralogical association commission on new minerals and mineral names. Europian Journal of Mineralogy, 9(3): 623–651.

Loiselle, M.C. and Wonse, D.R., 1979. Characteristics and origin of anorogenic granites. Geological Society of America, 11(7): 461– 468.

Mahmoodabadi, L., 2009. Petrography and petrology of Eocene volcanics from southwest of Jandaq (Northeast Isfahan). M.Sc. Thesis, University of Isfahan, Isfahan, Iran, 220 pp. (in Persian)

Nachit, H., Ibhi, A., Abia, E.H. and Ohoud, M.B., 2005. Discrimination between primary magmatic biotites, reequilibrated biotites and neoformed biotites. Copmtes Rendus Geoscience, 337(16): 1415–1420.

Offler, R. 1984. Subcalcic, Fe-rich amphiboles in meta-doleites, Glencrock Station, NSW, Australia. Mineralogical Magazine, 48(346): 47–52.

Papoutsa, A. and Pe-Piper, G., 2014. Geochemical variation of amphiboles in A-type granites as an indicator of complex magmatic systems: Wentworth pluton, Nova Scotia, Canada. Chemical Geology, 384: 120–134.

Rajabi, S. and Torabi, G., 2013. Mineralogy and Geochemistry of xenoliths in the Eocene volcanic southwest of the Jandaq. Journal of Economic Geology, 5(1): 65–82. (in Persian with English abstract)

Raymond, L.A., 2002. Petrology : the study of igneous, sedimentary, and metamorphic rocks. McGraw-Hill, Boston, 720 pp.

Schmidt, M.W., 1992. Amphibole composition in tonalite as a function of pressure an experimental calibration of the Al-hornblende barometer. Contributions to Mineralogy and Petrology, 110(2–3): 304–310. Shabbani, A.T. and Lalonde, A., 2003. Composition of Biotite from Granitic Rocks of the Canadian Appalachian: A potential tectonomagmatic indicator? The Canadian Mineralogist, 41(6): 1381–1396.

Sharkovski, M., Filichev, I., Selivanov, E., Susov, M., Dvoryankin, A., Amidi, S.M. and Davoudzadeh, M., 1984. Tectonic map of Anarak, scale: 1/250000, V/O Technoexport. Geological Survey of Iran.

Shirdashtzadeh, N., Torabi, G. and Samadi, R., 2017. Petrography and mineral chemistry of metamorphosed mantle peridotites of Nain Ophiolite (Central Iran). Journal of Economic Geology, 9(1): 57–72. (in Persian with English abstract)

Sisson, T.W. and Grove, T.L., 1993. Experimental investigation of the role of water in calc-alkaline differentiation and subduction zone magmatism. Contributions to Mineralogy and Petrology, 113(2): 143–166.

Takin, M., 1972. Iranian geology and continental drift in the Middle East. Nature, 235(5334): 147–150.

Torabi, G., 2010. Early Oligocene alkaline lamprophyric dykes from the Jandaq area (Isfahan Province, Central Iran): Evidence of Central-East Iranian microcontinent confining oceanic crust subduction. Island Arc, 19(2): 277–291.

Tulloch, A.J. and Challis, G.A., 2000. Paleozoic-Mesozoic plutons from western New Zealand

estimated by hornblende-Al geobarometry. New Zealand Journal of Geology and Geophysics, 43(4): 555–567.

Whitney, D.L. and Evans, B.W., 2010. Abbreviation for names of rock-forming minerals. American Mineralogist, 95(1): 185–187.

Wones, D.R., 1989. Significance of the assemblage titanite +magnetite +quartz in granitic rocks. American Mineralogist, 74(7–8): 744–749.

Zhao, K.D., Jiang, S.Y., Jiang, Y.H. and Wang, R.C., 2005. Mineral chemistry of the Qitianling granitoid and the Furong tin ore deposit in Hunan Province, South China: implication for the genesis of granite and related tin mineralization. European Journal of Mineralogy, 17(4): 635–648.

Zen, E., 1988. Phase relations of peraluminous granitic rocks and their petrogenetic implications. Annual Review of Earth and Planetary Sciences, 16(1) :21–52.

Zhou, Z.X., 1986. The origin of intrusive mass in Fengshandong, Huibei Province. Acta Petrologica Sinica, 2(1): 59–70.