Petrogenetic processes, crystallization conditions and nature of the Lower-Oligocene calc-alkaline spessartitic lamprophyres from Kal-e-kafi area (East of Anarak, Isfahan province)

Document Type : Research Article

Authors

• Ghodrat Torabi
• Gholam Hossain Nazari

Isfahan

10.22067/econg.v9i2.47493

Abstract

Introduction
Lamprophyres are mesocratic to melanocratic igneous rocks, usually hypabyssal, with a panidiomorphic texture and abundant mafic phenocrysts of dark mica or amphibole (or both) with or without pyroxene, with or without olivine, set in a matrix of the same minerals, and with alkali-feldspar restricted to the groundmass (Woolley et al., 1996). Lamprophyres are frequently associated with orogenic settings and a mantle modified by dehydration of subducted slab (Gibson et al., 1995).
Small outcrops of lamprophyres with Paleozoic to Oligocene age are reported from the central parts of Iran (Torabi 2009 and 2010). The primary magmas of these lamprophyres were derived from decompression melting of the mantle induced by a tensional regime of continental crust (Torabi, 2010). Bayat and Torabi (2011) called the western part of the CEIM (Central-East Iranian Microcontinent) (Anarak to Bayazeh) a “Paleozoic lamprophyric province” and suggested that the lamprophyre magmas were formed by subduction of Paleo-Tethys oceanic crust from the Early to late Paleozoic which resulted in the mantle metasomatism and enrichment.
Lamprophyric dykes and stocks of the Kal-e-kafi area (Central Iran, Northern part of Yazd Block) cross-cut the Eocene volcanic rocks and other older rock units such as Cretaceous limestone. These lamprophyres are mainly composed of hornblende (magnesio-hastingsite), clinopyroxene (diopside) and plagioclase (labradorite to bytownite) as phenocryst, in a matrix of fine to medium grained of the same minerals and orthoclase, apatite, magnetite, chlorite and epidote.
In this paper that is a report on the first study on the calc-alkaline lamprophyres of Central Iran, the petrography and mineral chemistry of calc-alkaline lamprophyric dykes of the Kal-e-kafi area are discussed.

Materials and methods
Chemical composition of minerals were conducted at Kanazawa University (Kanazawa, Japan) using the wavelength-dispersive electron probe microanalyzer (EPMA) (JEOL JXA-8800R), with 20kV accelerating potential, 20 nA beam current and a counting time of 40 seconds. Natural minerals and synthetic materials were used as standards. The ZAF program was used for data correction. The Fe3+ content of minerals was estimated by stoichiometry. The Mg# and Fe# were calculated as [Mg/(Mg+Fe2+)], and [Fe2+/(Fe2++Mg)] atomic ratio of minerals, respectively.
Trace element values of phenocrystic clinopyroxene, amphibole and plagioclase were analyzed by LA-ICP-MS (laser ablation-inductively coupled plasma-mass spectrometry) using an ArF 193 nm Excimer Laser coupled to an Agilent 7500S at the Earth Science Department of the Kanazawa University (Japan). The diameter of the analyzed points was 60 micrometers for clinopyroxene and 120 micrometers for amphibole and plagioclase.
Mineral abbreviations are adopted from Whitney and Evans (2010).

Results and Discussion
Lamprophyres of the Kal-e-kafi area (Central Iran, West of Yazd Block) are exposed as dykes and stocks which cross-cut the Eocene volcanic rocks and other older rock units such as Cretaceous limestone. Field studies indicate that calc-alkaline lamprophyric dykes of the Kal-e-kafi (east of Anarak) are younger than the other igneous rocks.
According to the results of petrography and mineral chemistry, the mesocratic lamprophyres of Kal-e-kafi area are calc-alkaline spessartite.
Unique values of Al2O3 and TiO2 associated with oscillatory zoning of clinopyroxenes reveal the crystallization of clinopyroxenes during ascending of magma.
Plagioclase phenocrysts are labradorite to bytownite in composition and the plagioclases of matrix are labradorite. Chemical composition diversity of plagioclase indicates the fractional crystallization of these lamprophyres.
Amphibole thermometry estimate average temperature of 860°C and barometry by Anderson and Smith (1995) shows 1.5 to 3 kbars pressure. Clinopyroxene thermobarometry calculate 1150 °C temperature and pressure between 2 to 5 kbars.
The geochemical features and thermobarometry of the Kal-e-kafi spessartite minerals suggest that the primary lamprophyric magma was derived from partial melting of a lithospheric mantle spinel lherzolite. Changes in values of pressure, water content, and Oxygen fugacity during magma ascending lead to oscillatory zoning minerals.
Based on the mineral chemistry, it can be concluded that the Kal-e-kafi lamprophyres were formed in a subduction-related environment by a calc-alkaline magmatism.

References
Anderson, J.L. and Smith, D.R., 1995. The effects of temperature and Oxygen fugacity on the Al-in-hornblende barometer, American Mineralogist, 80 (5-6): 549-559.
Bayat, F. and Torabi, G., 2011. Alkaline lamprophyric province of Central Iran. Island Arc, 20(3): 386 – 400.
Gibson, A.S., Thompson, R.N., Dickin, A.P. and Leonardos, O.H., 1995. High-Ti and low-Ti mafic potassic magmas: key to plume-lithosphereinteractions and continental flood-basalt genesis. Earth Planetary Science Letters, 136(3): 149–165.
Torabi, G.H., 2009. Late Permian lamprophyric magmatism in North-East of Isfahan Province, Iran: A mark of rifting in the Gondwanaland. Comptes Rendus Geoscience, 341(1): 85–94.
Torabi, G.H., 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.
Whitney, D.L. and Evans, B.W., 2010. Abbreviations for names of rock-forming minerals. American Mineralogist, 95(1): 185-187.
Woolley, A.R., Bergman, S.C., Edgar, A.D., Le Bas, M.J., Mitchell, R.H., Rock, N.M.S. and Scott-Smith, B.H., 1996. Classification of lamprophyres, lamproites, kimberlites and the kalsilite mellitic and leucitic rocks. The Canadian Mineralogist, 34(2): 175-186.

Keywords

• Spessartite
• Lamprophyre
• calc-alkaline
• Oligocene
• Kal-e-kafi
• Central Iran

20.1001.1.20087306.1396.9.2.7.5

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References

Ahmadian, J., Hasckke, M., Mc Donald, I., Regelous, M., Ghorbani, M.R., Emami, M.H. and Murata, M., 2009. High magmatic flux during Alpine-Himalayan collision: Constraints from the Kal-e-kafi complex, centeral Iran. Geological Society of America, 121(5): 857-868.

Ahmadian, J., Sarjoughian, F., Lentz, D., Esna-Ashari, A., Murata, M. and Ozawa, H., 2016. Eocene K-rich adakitic rocks in the Central Iran: Implications for evaluating its Cu–Au–Mo metallogenic potential. Ore Geology Reviews, 72(1): 323-342.

Aistov, L., Melnikov, B., Krivyakin, B. and Morozov, L., 1984. Geology of the Khur area (central Iran), Geological Survey of Iran, Tehran, TE Report 20, 131 pp.

Alavi, M., 1991. Tectonic map of the Middle East, Scale 1:5000000, Geological Survey of Iran, Tehran.

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

Aoki, K.I., and Kushiro, I., 1968. Some clinopyroxenes from ultramafic inclusions in Dreiser Weiher, Eifel. Contributions to Mineralogy and Petrology, 18(4): 326−337.

Bahadoran, N., 2007. Petrology and geochemistry of volcanic rocks in west of the Arousan-e -Kaboudan area (south of Choupanan - North east of Esfahan). M.Sc. Thesis, University of Esfahan, Esfahan, Iran, 120 pp. (in Persian with English abstract)

Bayat, F. and Torabi, G., 2011. Alkaline lamprophyric province of Central Iran. Island Arc, 20(3): 386 – 400.

Baziotis, I., Mposkos, E. and Leontakianakos, G., 2012. Amphibole chemistry from the Penteli metamorphic core complex: implication for the metamorphic evolution of eastern Attica. First European Mineralogical Conference, Frankfurt, Germany.

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., 1996. An introduction to the rock-forming minerals. Longman, London, United Kingdom, 696 pp.

Femenias, O., Mercier, J.C., Nkono, C., Diot, H., Berza, T., Tatu, M. and Demaiffe, D., 2006. Calcic amphibole growth and compositions in calc-alkaline magmas: Evidence from the Motru Dike Swarm (Southern Carpathians, Romania). American Mineralogist, 91(1): 73-81.

Gibson, A.S., Thompson, R.N., Dickin, A.P. and Leonardos, O.H., 1995. High-Ti and low-Ti mafic potassic magmas: key to plume-lithosphereinteractions and continental flood-basalt genesis. Earth Planetary Science Letters, 136(3): 149–165.

Hammarstrom, J.M. and Zen, E.A., 1986. Aluminium in hornblende: an empirical igneous geobarometer. American Mineralogist, 71(11-12): 1297-1313.

Helz, R.T., 1973. Phase relations of basalts in their melting ranges at pH2O = 5 kb as a function of Oxygen fugacity, Part I. Mafic phases. Journal of Petrology, 14(2): 249-302.

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 calc-alkaline plutons. American Mineralogist, 72(3-4): 231–239.

Ishida, Y., Morishita, T., Arai, S. and Shirasaka, M., 2004. Simultaneous in-situ multi-element analysis of minerals on thin section using LA-ICP-MS. Science Reports of Kanazawa University, 48(1, 2): 31-42.

Johnson, M.C. and Rutherford, M.J., 1988. Experimental calibration of an aluminum-in-hornblende geobarometer applicable to calc-alkaline rocks. Earth and Space Science News, 69(44):1511.

Leake, B.E., Woolley, 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.A., Maresch, W.V., Nickel, E.H., Rock, N.M.S., Schumacher, J.C., Smith, D.C., Stephenson, N.C.N., Ungaretti, L., Whittaker, E.J.W. and Guo, Y., 1997. Nomenclature of amphiboles: Report of the subcommittee on amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names. The Canadian Mineralogist, 35(1): 219-246.

Le Bas, M., 2007. Igneous rock classification revisited 4: Lamprophyres. Geology Today, 23(5): 167-168.

Le Bas, M.J., 1962. The role of Aluminium in igneous clinopyroxenes with relation to their parentage. American Journal of Science, 260(4): 267 - 288.

Li, Y., 1998. Crystal chemistry, microstructures, and petrologic implication of the amphiboles from the blueschists of Southwestern Oregon. M.Sc. Thesis, Brigham Young University, Utah, United States, 74 pp.

Mayer, B., 2013. Petrogenesis of hornblende - bearing lavas (Rhӧn, Germany). Ph.D. Thesis, Hamburg University, Hamburg, Germany, 86 pp.

McDonough, W.F. and Sun, S.-s., 1995. The composition of the Earth. Chemical Geology, 120(3-4): 223 – 253.

Moretti, R. and Baker, D.R., 2008. Modeling the interplay of fO2 and fS2 along the FeS-silicate melt equilibrium. Chemical Geology, 256(3-4), 286–298.

Morimoto, N., Fabrise, J., Ferguson, A., Ginzburg, I.V., Ross, M., Seifert, F.A., Zussman, J., Akoi, K. and Gottardi, G., 1988. Nomenclature of pyroxenes. Mineralogical Magazine, 52(367): 535-550.

Morishita, T., Ishida, Y. and Arai, S., 2005a. Simultaneous determination of multiple trace element compositions in thin (<30 μm) layers of BCR-2G by 193 nm ArF excimer laser ablation-ICP-MS: Implications for matrix effect and elemental fractionation on quantitative analysis. Geochemical Journal, 39(4): 327-40.

Morishita, T., Ishida, Y., Arai, S. and Shirasaka, M., 2005b. Determination of multiple trace element compositions in thin (<30 μm) layers of NIST SRM 614 and 616 using laser ablation-inductively coupled plasma-mass spectrometry. Geostandards and Geoanalytical Reseach, 29(1): 107-22.

Otten, M.T., 1984. The origin of brown hornblende in the Artssjället gabbros and dolerites. Contributions to Mineralogy and Petrology, 86(2): 189 - 199.

Ridolfi, F., Renzulli, A. and Puerini, M., 2010. Stability and chemical equilibrium of amphibole in calc alkaline magmas: an overview, new thermobarometric formulations and application to subduction related volcanoes. Contributions to Mineralogy and Petrology, 160(1): 45-66.

Rock, N.M.S., 1991. Lamprophyres. Blackie and Sons Limited, Glasgow, Scotland, 285 pp.

Rutherford, M.J., 2008. Magma Ascent rates. Reviews in Mineralogy and Geochemistry, 69(1): 241-271.

Schmidt, M.W., 1992. Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblende barometer. Contributions to Mineralogy and Petrology, 110(2-3): 304-310.

Shore, M. and Fowler, A.D., 1996. Oscillatory zoning in minerals: A common phenomenon. The Canadian Mineralogist, 34(6): 1111-1126.

Simakin, A., Zakrevskaya, O. and Salova, T., 2012. Novel Amphibole geo-barometer with application to mafic xenoliths. Earth Science Research, 1(2): 82-97.

Soesoo, A., 1997. A multivariate statistical analysis of clinopyroxene compositions: empirical coordinates for the crystallization and PT estimations. Journal of Geological Society of Sweden, 119(1), 55-60.

Sun, C. and Liang, Y., 2012. Distribution of REE between clinopyroxene and basaltic melt along a mantle adiabat: Effects of major element composition, water, and temperature. Contributions to Mineralogy and Petrology, 163(5): 807-823.

Sun, C.M., Bertrand, J., 1991. Geochemistry of clinopyroxenes in plutonic and volcanic sequences from the Yanbian Proterozoic ophiolites (Sichuan Province, China): petrogenetic and geotectonic implications. Schweizer Minealogische und Petrographische Mitteilungen, 71(2): 243–259.

Sun, S.S. and McDonough, W.F., 1989. Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: A.D. Saunders and M.J. Norry (Editors), Magmatism in the ocean basins. Geological Society, London, pp. 313–345.

Torabi, G.H., 2009. Late Permian lamprophyric magmatism in North-East of Isfahan Province, Iran: A mark of rifting in the Gondwanaland. Comptes Rendus Geoscience, 341(1): 85–94.

Torabi, G.H., 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.

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

Wood, B.J. and Blundy, J.D., 1997. Predictive model for rare earth element partitioning between clinopyroxene and anhydrous silicate melt. Contributions to Mineralogy and Petrology, 129(2-3): 166-181.

Woolley, A.R., Bergman, S.C., Edgar, A.D., Le Bas, M.J., Mitchell, R.H., Rock, N.M.S. and Scott-Smith, B.H., 1996. Classification of lamprophyres, lamproites, kimberlites and the kalsilite mellitic and leucitic rocks. The Canadian Mineralogist, 34(2): 175-186.

Yakovenko, V., Chinakov, I., Kokorin, Yu. and Krivyakin, B., 1981. Report on geological prospecting in Anarak area (Kal-e Kafi- Khuni locality). Moscow, Report No. 13, 293 pp.