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Geology and petrography of gabbroic rocks from Khanozai Ophiolite, Northwestern Pakistan

Author Affiliations

  • 1Centre of Excellence in Mineralogy, University of Balochistan, Quetta, Pakistan
  • 2Centre of Excellence in Mineralogy, University of Balochistan, Quetta, Pakistan
  • 3Department of Earth and Environmental Sciences, Bahria University Karachi Campus, Pakistan

Int. Res. J. Earth Sci., Volume 7, Issue (3), Pages 10-22, September,25 (2019)

Abstract

The geology of Khanozai area is comprised of Indian Platform Sediments, the Suture Zone and Flysch Zone. The Khanozai Ophiolite Complex is a fragment of Zhob Valley ophiolites is marking the Suture Zone in the area and consists of mantle peridotite overlain by crustal ultramafic to mafic cumulate which is underlain by metamorphic sole rocks and mélange. The crustal section of the ophiolite comprises of both ultramafic to mafic cumulates. Ultramafic cumulates comprise repeated successions of dunite, pyroxenite and wehrlite while mafic cumulates consist of foliated to layered gabbros. The Khanozai gabbros cover about 60% area of the crustal plutonic rocks and have a lower transitional contact with the ultramafic cumulates. The gabbros (sensu lato) are classified as olivine gabbro, gabbronorite, olivine gabbronorite, norite and gabbro. The mineralogy of the gabbros indicates that they have both primitive and evolved components. The geochemistry indicates that the Khanozai gabbros are tholeiitic in nature and comprise both cumulate and non-cumulate mineral phases with olivine, pyroxenes and plagioclase being involved in fractionation. The cyclic series of ultramafic cumulates and gabbros has a different order, thickness, and structure in the crustal part of ophiolite and this possibly results from a variable supply of different magma compositions to the chamber. The structure of Khanozai Ophiolite' crustal section, with a well-developed plutonic sequence and absence of sheeted dyke indicate that these rocks may have formed in a tectonic setting with a slow spreading rate over different periods of time as a consequence of episodic low magma supply rates. These gabbros may have formed in a similar manner to the Semail Ophiolite' gabbros and imply that a well-developed ophiolitic sequence is rarely formed in a tectonic setting where the spreading and magma supply rates are not balanced.

References

  1. Dilek Y. and Furnes H. (2011)., Ophiolite genesis and global tectonics: geochemical and tectonic fingerprinting of ancient oceanic lithosphere., Geological Society of America Bulletin, 123(3-4), 387-411.
  2. Robinson P.T. and Zhou M.F. (2008)., The origin and tectonic setting of ophiolites in China., Journal of Asian Earth Sciences, 32(5), 301-307.
  3. Robertson A.H. (2002)., Overview of the genesis and emplacement of Mesozoic ophiolites in the Eastern Mediterranean Tethyan region., Lithos, 65(1), 1-67.
  4. Kakar M.I., Kerr A.C., Mahmood K., Collins A.S., Khan M. and McDonald I. (2014)., Supra-subduction zone tectonic setting of the Muslim Bagh Ophiolite, northwestern Pakistan: insights from geochemistry and petrology., Lithos, 202, 190-206.
  5. Mahmood K., Boudier F., Gnos E., Monié P. and Nicolas A. (1995)., 40Ar/39Ar dating of the emplacement of the Muslim Bagh ophiolite, Pakistan., Tectonophysics, 250, 169-181.
  6. Siddiqui R.H., Aziz A., Mengal J.M., Hoshino K. and Sawada Y. (1996)., Geology, Petrochemistry and tectonic evolution of Muslim Bagh ophiolite complex, Pakistan., In Proc. Of Geoscience Colloquium, Geoscience Lab., GSP, 16, 11-46.
  7. Khan M., Kerr A.C. and Mahmood K. (2007)., Formation and tectonic evolution of the Cretaceous-Jurassic Muslim Baghophiolitic complex, Pakistan: Implications for the composite tectonic setting of ophiolites., Journal of Asian Earth Sciences, 31(2), 112-127.
  8. Warraich M.Y., Ali M., Ahmed M.N. and Siddiqui M.R.H. (1995)., Geology and structure of the Calcareous zone in the Muslim Bagh in the Qilla Saifullah Area, Balochistan., Geologica, 1, 61-75.
  9. Gansser A. (1964)., Geology of the Himalayas., New York: Interscience, 289, 406.
  10. Kasi A.K., Kassi A.M., Umar M., Manan R.A. and Kakar M.I. (2012)., Revised Lithostratigraphy of the Pishin Belt, Northwestern Pakistan., Journal of Himalayan Earth Sciences, 45, 53-65.
  11. Ahmed Z. (1986)., Ophiolites and chromite deposits of Pakistan., In: Petraschek, W., Karamata,S., Karavchenko, G.G., Johan, Z., Economou, M. &, Engin, T. (Eds.), \\\"Chromites, Unesco
  12. Siddiqui R.H., Mengal J.M. and Haider N. (1999)., First Occurenec of Late Magmatic Iron Ore Association with Ophiolite Complex in Khanozai Area, Baluchistan, Pakistan., Geologica, Geoscience Laboratory, Islamabad Pakistan, 4, 123-134.
  13. Macalalad E., Bayoran R., Ebarvia B. and Rubeska I. (1988)., A concise analytical scheme for 16 trace elements in geochemical exploration samples using exclusively AAS., Journal of Geochemcial Exploration, 30, 167-177.
  14. Jeffery P.G. and Hutchison D. (1981)., Chemical methods of rock analysis., Oxford: Pergamon press, 3.
  15. White W.M. and Klein E.M. (2014)., 4.13-Composition of the Oceanic Crust., Treatise on Geochemistry (Second Edition).
  16. Gale A., Dalton C.A., Langmuir C.H., Su Y. and Schilling J.G. (2013)., The mean composition of ocean ridge basalts., Geochemistry, Geophysics, Geosystems, 14(3), 489-518.
  17. Nicolas A. (1989)., Structures of Ophiolites and Dynamics of Oceanic Lithosphere., Kluwer, Dordrecht.
  18. Coogan L.A., Thompson G. and MacLeod C.J. (2002)., A textural and geochemical investigation of high level gabbros from the Oman ophiolite: Implications for the role of the axial magma chamber at fast-spreading ridges., Lithos, 63, 67-82.
  19. Coogan L.A., Jenkin G.R. and Wilson R.N. (2002)., Constraining the cooling rate of the lower oceanic crust: a new approach applied to the Oman ophiolite., Earth and Planetary Science Letters, 199(1-2), 127-146.
  20. Thy P. (1987)., Magmas and magma chamber evolution, Troodos ophiolite., Cyprus. Geology, 15(4), 316-319.
  21. Thy P. (1987)., Petrogenetic implications of mineral crystallization trends of Troodos cumulates, Cyprus., Geological Magazine, 124(1), 1-11.
  22. Parlak O., HÖck V. and Delaloye M. (2000)., Suprasubduction zone origin of the Pozanti-Karsanti ophiolite (southern Turkey) deduced from whole-rock and mineral chemistry of the gabbroic cumulates., Geological Society, London, Special Publications, 173(1), 219-234.
  23. Dilek Y. and Eddy C.A. (1992)., The Troodos (Cyprus) and Kizildag (S. Turkey) ophiolites as structural models for slow-spreading ridge segments., The Journal of Geology, 100(3), 305-322.
  24. Saccani E. and Photiades A. (2004)., Mid-ocean ridge and supra-subduction affinities in the Pindos ophiolites (Greece): implications for magma genesis in a forearc setting., Lithos, 73(3), 229-253.
  25. Girardeau J., Mercier J.C.C. and Xibin W. (1985)., Petrology of the mafic rocks of the Xigaze ophiolite, Tibet., Contributions to Mineralogy and Petrology, 90(4), 309-321.
  26. Kakar M.I., Mahmood K., Khan M., Kasi A.K. and Manan R.A. (2013)., Petrology and geochemistry of gabbros from the Muslim Bagh Ophiolite: implications for their petrogenesis and tectonic setting., Journal of Himalayan Earth Science, 46(1).
  27. Gnos E., Khan M., Mehmood K., Khan A.S., Naseer A. and Igor M.V. (1998)., Bela Oceanic lithosphere assemblage and its relation to the Reunion hot spot., Terra Nova, 10, 90-95.
  28. Cannat M., Sauter D., Mendel V., Ruellan E., Okino K., Escartin J., Combier V. and Baala M. (2006)., Modes of seafloor generation at a melt-poor ultraslow-spreading ridge., Geology, 34, 605-608.
  29. Boudier F., Nicolas A. and Ildefonse B. (1996)., Magma chambers in the Oman ophiolite: fed from the top and the bottom., Earth and Planetary Science Letters, 144(1-2), 239-250.
  30. Pallister J.S. and Hopson C. (1981)., Samail ophiolite suite: Field relations, phase variation, cryptic variation and layering and a model of a spreading ridge magma chamber., J. Geophys. Res., 86, 2593-2644.
  31. Lippard S.J. (1986)., The ophiolite of northern Oman., Geological Society London Memoir, 11, 178.
  32. Buck W.R. (2000)., Can downward flow of dense cumulate slurry through mushy upper gabbros produce lower gabbros at a fast-spreading center?., in Ophiolites and Oceanic Crust:New Insights from Field Studies and the Ocean Drilling Program, edited by Y. Dilek et al., Spec. Pap. Geol. Soc. Am., 349, 121-127.
  33. MacLeod C.J. and Yaouancq G. (2000)., A fossil melt lens in the Oman ophiolite: Implications for magma chamber processes at fast spreading ridges., Earth Planet. Sci. Lett., 176, 357-373.
  34. Kelemen P. and Aharonov E. (1998)., Periodic formation of magma fractures and generation of layered gabbros in the lower crust beneath oceanic spreading ridges., in Faulting and Magmatismat Mid-Ocean Ridges, Geophys. Monogr. Ser., edited by R. W. Buck et al., 106, 267-289. AGU, Washington, D. C.
  35. Jones A.G. (1961)., Reconnaissance geology of part of West Pakistan. A Colombo Plan Cooperative Project., Toronto, Canada: Government of Canada.
  36. Cox K.G., Bell J.D. and Pankhurst R.J. (1979)., The interpretation of igneous rocks., George Allen and Unwin. London.
  37. Irvine T.N.J. and Baragar W.R.A. (1971)., A guide to the chemical classification of the common volcanic rocks., Canadian journal of earth sciences, 8(5), 523-548.