Petrology and geochemistry of Late Proterozoic hornblende gabbros from southeast of Fariman, Khorasan Razavi province, Iran

Document Type : Research Article

Author

• Seyed Masoud Homam

Ferdowsi University of Mashhad

10.22067/econg.v7i1.33610

Abstract

Introduction
Hornblende-bearing gabbroic rocks are quite common in subduction-related magmatic suites and considered to represent magmatic differentiation process in arc magmas (Heliker, 1995; Hickey-Vargas et al., 1995; Mandal and Ray, 2012). The presence of hornblende as an important mineral phase in gabbroic rocks of subduction zone has been considered either as an early crystallizing mineral from water-bearing mafic magmas (Beard and Borgia 1989; Mandal and Ray, 2012) or as a product of reaction of early crystallized minerals (olivine, pyroxene and plagioclase) and water-rich evolved melt/aqueous fluid (Costa et al., 2002; Mandal and Ray, 2012). The careful study of petrology and geochemistry of hornblende-bearing gabbroic rocks from Chahak area, of Neoproterozoic age, can provide important information about their petrogenesis. Because of the special characteristics of Chahak hornblende gabbros according to their age and their situation in the main structural units of Iran, their study can present critical keys for the knowledge of geological history of Iran specially central Iran zone.

Material and Methods
This study carried out in two parts including field and laboratory works. Sampling and structural studies were carried out during field work. Geological map for the study area was also prepared. 65 thin and polished thin sections for petrographical purpose were studied. Major oxides, rare earth elements and trace elements were analyzed for 4 samples (92P-1, 92P-3, B1and B6) from hornblende gabbros on the basis of 4AB1 method using ICP-MS of ACME Laboratory from Canada. In addition, major oxides of three hornblende gabbro samples (89P-62, 89P-59 and 89P-46) were used from Partovifar (Partovifar, 2012).

Results and discussion
Fariman metamorphic terrains, of Proterozoic age, consist of metamorphosed sedimentary and igneous (plutonic and volcanic) rocks. Hornblende gabbros of the study area include plagioclase, hornblende, biotite pyroxene and olivine as major minerals and apatite, ilmenite and magnetite as minor minerals. In many examples, hornblende and biotite can be seen as corona textures around plagioclase, pyroxene and olivine, while plagioclase, pyroxene and olivine show obviously corrosion features. This can be considered to be formed by the reaction of early formed crystals with aqueous fluid/evolved melt. In some cases, amphiboles show rhythmic overgrowths. The rhythmic amphibole overgrowths represent deep-seated crystallization in a volatile-rich magma under conditions of high but varying gas pressure. In the study area, the most dominant texture of the hornblende gabbros is hypidiomorphic granular, but intergranular and porphyric textures are common too.
Based on geochemical data from major and minor elements, studied rocks belong to tholeiite series with meta–aluminous nature. The geochemical behavior of main elements of the studied rocks reveals the normal trend of differentiation in their magma. Chondrite-normalized REE diagram of hornblende gabbros indicates an obvious enrichment of LREE in compare with HREE. MORB-normalized spider diagrams indicate variable enrichment in LILE and depletion in high field strength elements (HFSE). Primitive mantle-normalized spider diagram show negative anomaly for Nb and Zr. Gabbros from southeast of Fariman have an island arc tholeiite nature and based on trace element diagrams, they formed as a result of 3 to 10% partial melting of a garnet lherzolite source.
The mineralogy, texture and geochemistry of the studied rocks show striking similarities with gabbroic rocks of subduction zone developed in supra subduction zone of arc-marginal basin setting.

Acknowledgments
The Research Foundation of Ferdowsi University of Mashhad, Iran, supported this study (Project 28035.2). I thank the university authorities for funding.

Reference
Beard, J.S., and Borgia, A., 1989. Temporal variation of mineralogy and petrology in cognate gabbroic enclaves at Arenal volcano, Costa Rica. Contributions to Mineralogy and Petrology, 103(1): 110–122.
Costa, F., Dungan, M.A., and Singer, B.S., 2002. Hornblende- and phlogopite-bearing gabbroic xenoliths from Volc´an San Pedro (36◦S), Chilean Andes: Evidence for melt and fluid migration and reactions in subduction-related plutons. Journal of Petrology, 43(3): 219–241.
Heliker, C., 1995. Inclusions in Mount St. Helens dacite erupted from 1980 through 1983. Journal of Volcanology and Geothermal Research, 66(1-4): 115–135.
Hickey-Vargas, R., Abdollahi, M.J., Parada, M.A., Lopez-Escobar, L. and Frey, F.A., 1995. Crustal xenoliths from Calbuco volcano, Andean southern volcanic zone: Implications for crustal composition and magma-crust interaction. Contributions to Mineralogy and Petrology, 119(4): 331–344.
Mandal, A., Ray, A., Debnath, M. and Paul, S.B., 2012. Geochemistry of hornblende gabbro and associated dolerite dyke of Paharpur, Puruliya, West Bengal: Implication for petrogenetic process and tectonic setting. Journal of Earth System Science, 121(3): 793–812.
Partovifar, F., 2012. Petrology and geochemistry studies of granitic rocks from Chahak village, Kariz-Now area, southeast of Fariman, Iran. Unpublished M.Sc. thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 145 pp. (in Persian)

Keywords

• Hornblende Gabbro
• Granite
• Tholeiitic Basalt
• Subduction zone
• MORB
• Overgrowths
• Fariman

20.1001.1.20087306.1394.7.1.6.8

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References

Aghanabati, S.A., 1975. Etude geologique de la region de Kalmard (W.Tabas) Iran Central; stratgraphie et tectonique. Ph.D. Thesis, Grenoble University, Grenoble, France, 231 pp.

Alavi, M., Vaziri, H., Seyed-Emami, K. and Lasemi, Y., 1997. The Triassic and associated rocks of the Nakhlak and Aghdarband areas in central and northeastern Iran as remnants of the southern Turanian active continental margin. Geological survey of America Bulletin, 109(12): 1563-1575.

Batchelor, R.A. and Bowden, P., 1985. Petrogenetic interpretation of granitoid rock series using multicationic parameters. Chemical Geology, 48(1-4): 43-55.

Beard, J.S., and Borgia, A., 1989. Temporal variation of mineralogy and petrology in cognate gabbroic enclaves at Arenal volcano, Costa Rica. Contributions to Mineralogy and Petrology, 103(1): 110–122.

Bowes, D.R.E.D. and Kinloch, A.E., 1964. Wright Rhythmic Amphibole Overgrowths in Appinites Associated with Explosion-Breccias in Argyll. Mineralogical Magazine, 266: 963-973.

Chappell, B.W., 1999. Aluminium saturation in I– and S–type granites and the characterization of fractionated haplogranites. Lithos, 46(3): 535–551.

Costa, F., Dungan, M.A., and Singer, B.S., 2002. Hornblende- and phlogopite-bearing gabbroic xenoliths from Volc´an San Pedro (36◦S), Chilean Andes: Evidence for melt and fluid migration and reactions in subduction-related Plutons. Journal of Petrology, 43(3): 219–241.

Cox, K.G., Bell, J.D. and Pankhurst, R.J., 1979. The interpretation of igneous rocks. George Allen and Unwin, London, 450 pp.

Eftekhar-Nejad, J., 1973. Some information about the origin of the flysch basin in Eastern Iran and its relation to plate tectonics theory. Geological Survey of Iran, Tehran, Report 22, 125 pp.

Ellam, R.M., 1992. Lithospheric as a control on basalt geochemistry. Geology, 20(2): 153–156.

Fitton, J., James, D., Leeman, W., 1991. Basic magmatism associated with Late Cenozoic extension in the western United States: Compositional variations in space and time. Journal of Geophysical Research, 96(B8), 13693–13711.

Fray, F.A., Garcian, M.O., Wise, W.S., Kennedy, A., Gurriet, P.A. and Albarede, F., 1991. The evolution of Mauna Kea volcano, Hawaii: Petrogenesis of tholeiitic and alkalic basalts. Journal of Geophysical Research, 96(B9): 14347–14375.

Gramont, X.B. and Guillou, Y., 1979. Geological map of Kariznow. Geological Survey of Iran, Scale 1:100,000.

Gurney, J.J. and Harte, B., 1980. Chemical variations in upper mantle nodules from southern Africa kimberlites. Philosophical Transactions of the Royal Society of London, 297(1431): 273–293.

Heliker, C., 1995. Inclusions in Mount St. Helens dacite erupted from 1980 through 1983. Journal of Volcanology and Geothermal Research, 66(1-4): 115–135.

Hickey-Vargas, R., Abdollahi, M.J., Parada, M.A., Lopez-Escobar, L. and Frey, F.A., 1995. Crustal xenoliths from Calbuco volcano, Andean southern volcanic zone: Implications for crustal composition and magma-crust interaction. Contributions to Mineralogy and Petrology, 119(4): 331–344.

Irvine, T.N. and Baragar, W.R.A.A., 1971. Guide to the chemical classification of the common volcanic rocks. Canadian Journal of Earth Sciences, 8(5): 523–548.

Kamber, B.S., Ewart, A., Collerson, K.D., Bruce, M.C. and McDonald, G.D., 2002. Fluid–mobile trace element constraints on the role of slab melting and implications for Archaean crustal growth models. Contributions to Mineralogy and Petrology, 144(1): 38–56.

Mandal, A., Ray, A., Debnath, M. and Paul, S.B., 2012. Geochemistry of hornblende gabbro and associated dolerite dyke of Paharpur, Puruliya, West Bengal: Implication for petrogenetic process and tectonic setting. Journal of Earth System Science, 121(3): 793–812.

Maniar, P.D. and Picooli, P.M., 1989. Tectonic discrimination of granitoids. Geological Society of America Bulletin, 101(3): 635–643.

Martin, H., 1999. Adakitic magmas: modern analogues of Archaean granitoids. Lithos, 46(3): 411–429.

Meschede, M., 1986. A method of discriminating between different types of mid-ocean ridge basalts and continental tholeiites with the Nb-Zr-Y diagram. Chemical Geology, 56(3-4): 207-218.

Middlemost, E.A.K., 1985. Magmas and magmatic rocks: An introduction to igneous petrology. Longman Group, United Kingdom, 390 pp.

Mullen, E.D., 1983. MnO/TiO2/P2O5: a minor element discriminate for basaltic rocks of oceanic environments and its implications for petrogenesis. Earth and Planetary Science Letters, 62(3): 53-62.

Nabavi, M.H., 1976. An Introduction to Geology of Iran. Geologic Survey of Iran, Tehran, 109 pp. (in Persian)

Ozdemir, Y., KaraogLu, O., Tolluoglu, A.U. and Gulec N., 2006. Volcano stratigraphy and petrogenesis of the Nemrat stratovolcano (East Anatollian High Plateau): The most recent post collisional volcanism in Turkey. Chemical Geology, 226(3-4): 189–211.

Partovifar, F., 2012. Petrology and geochemistry studies of granitic rocks from Chahak village, Kariz-Now area, southeast of Fariman, Iran. Unpublished M.Sc. thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 145 pp. (in Persian)

Pearce, J.A., 1982. Trace element characteristics of lavas from destructive plate boundaries. In: R.S. Thorp (Editor), Andesites: Orogenic Andesites and Related Rocks. John Wiley and Sons, New York, pp. 525-548.

Pearce, J.A. and Cann, J.R., 1973. Tectonic setting of basic volcanic rocks determined using trace element analyses. Earth and Planetary Science Letters, 19(2): 290-300.

Pearce, J.A., Harris, N.B.W. and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25(4): 956–983.

Peccerillo, A. and Taylor, S.R., 1976. Geochemistry of Eocene calc–alkaline volcanic rocks from the Kastamonu area, northern Turkey. Contributions to Mineralogy and Petrology, 58(1): 63–81.

Ranjbar-Moghadam, F., 2011. The petrology and petrogenesis of metamorphic rocks in east and southeast of Fariman. Unpublished M.Sc. thesis, Ferdowsi University of Mashhad, Mashhad, Iran, 156 pp. (in Persian)

Rollinson, H.R., 1993. Using geochemical data: evaluation, presentation, interpretation. Longman Group, UK, 315 pp.

Safouraee, S., 2008. Petrology and geochemistry of metamorphic rocks from southeast of Fariman. Unpublished M.Sc. thesis, University of Shahrood, Shahrood, Iran, 120 pp. (in Persian)

Vaezi-Pour, M, Kholghi, M.H. and Alavi-Naeini, M., 1983. The geology of Farima-Zharf area and study of metamorphic rocks in northeast of Iran. Geological Survey of Iran Report.

Whalen, J.B., Currie, K.L. and Chappell, B.W., 1987. A-type granites: Geochemical characteristics, discrimination and petrogenesis. Contributions to Mineralogy and Petrology, 95(4): 407-419.

Wilson, M., 1989. Igneous Petrogenesis. Chapman and Hall, London, 466 pp.