Mineralogy of a New Occurrence of Lamprophyre Dyke from the Saurashtra Peninsula of Gujarat, Northwest Deccan Trap, India
- 4 Downloads
A new occurrence of lamprophyre dyke is being reported from Saurashtra peninsula of Gujarat, north-western Deccan trap. The paper presents and discusses the detail mineralogy, field setting and whole rock major and trace element geochemistry. The newly discovered lamprophyre dyke intruded into the porphyritic olivine basalt flow. It is E-W trending dyke paralleling with Narmada rift trend, 200 m long and ∼1 m in width. Petrographic observations suggest the lamprophyre dyke is fine grained, porphyritic and shows typical panidiomoprphic texture. It contains phenocrysts of euhedral to subhedral amphibole (kaersutite), subhedral clinopyroxenes (diposide augite) and olivine pseudomorph enveloped in the groundmass composed of plagioclase, clinopyroxene and amphibole with carbonate, Ti-magnetite, zeolite and apatite occurring as accessory phases. Few clinopyroxenes show reaction and embayed margins thus indicating xenocrystic orgin. The normative chemistry of the lamprophyre dyke suggests alkaline nature with significant amount of olivine and nepheline. Whole rock geochemical data shows comparatively higher SiO2 than the other lamprophyres of the Deccan and similar to the MgO depleted lamprophyres of the Chhota Udepur alkaline province. The primitive mantle normalized multielements pattern shows absence of any high field strength element (HFSE) anomaly. Studied dyke displays more similarity with the earlier reported pre- Deccan alkaline lamprophyres and more particular with the Chhota Udepur lamprophyre. Occurrence of this new lamprophyre dyke from the Saurashtra region extends and confirms the presence of lamprophyre magmatism in the far north-western part of the Deccan.
Unable to display preview. Download preview PDF.
The authors would like to express his gratitude and sincere thanks to Director General, Geological Survey of India (GSI); ADG & HOD, GSI, Western Region (WR), Jaipur; DDG, GSI, SU-Gujarat, Gandhinagar for encouragement and permission to publish this work. Special thanks to my colleagues for the discussion and suggestions at various stages. Chemical division, GSI, Jaipur and EPMA laboratory, GSI, Faridabad are thanked for providing laboratory support. This work is an outcome of Specialized Thematic Mapping (STM) project of FSP code 2012-13/STM/WR/GUJ/2012/008; Item No-14 of GSI, WR.
- Baksi, A.K. (1994) Intracanyon flows in the Deccan province, India? Case history of the Rajahmundry Traps. Geology, v.2, pp. 605–608.Google Scholar
- Dongre, A., Viljoen, K. S. and Rathod, A. (2017) Mineralogy and geochemistry of picro-dolerite dykes from the central Deccan Traps flood basaltic province, India, and their geodynamic significance. Miner. Petrol., pp.1–11.Google Scholar
- Durgadamath, M.B. (1984) Lamprophyric dykes from Phenaimata, Baroda district. Spec. Publ. Geol. Surv. India, v.12, pp.3–6.Google Scholar
- Gwalani, L.G., Rock, N.M.S., Chang, W-J., Fernandez, S., Allegre, C.J. and Prinzhofer, A. (1993) Alkaline rocks and carbonatites of Amba Dongar and adjacent areas, Deccan Igneous Province, Gujarat, India: Geology, petrography and petrochemistry. Mineral. Petrol., v.47, pp.219–253.CrossRefGoogle Scholar
- Hari, K.R. (1998) Mineralogical and petrochemical studies of the lamprophyres around Chhaktalao area, Madhya Pradesh. Jour. Geol. Soc. India, v.51, pp.21–30.Google Scholar
- Leake, B.E., Wooley, 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 Youzhi, G. (1997) Nomenclature of amphiboles: report of the subcommitee on amphiboles of the international mineralogical association, commission on new minerals and mineral names. Amer. Mineral., v.82, 1019–1037.Google Scholar
- Pandey, A., Rao, N.V. C., Chakrabarti, R., Pandit, D., Pankaj, P., Kumar, A. and Sahoo, S. (2017) Petrogenesis of a Mesoproterozoic shoshonitic lamprophyre dyke from the Wajrakarur kimberlite field, eastern Dharwar craton, southern India:Geochemical and Sr-Nd isotopic evidence for a modified sub-continental lithospheric mantle source, Lithos, v.292–293, pp.218–233.CrossRefGoogle Scholar
- Pouchou, J.J. and Pichoir, F. (1985) PAP(ö-ñ-Z) procedure for improved quantitative microanalysis. In: Armstrong, J.T. (Ed.), Microbeam Analysis, pp.104–106.Google Scholar
- Randive, K.R., Prasad, G.J.S., Anil Kumar, A., Rama Rao, R., Bhaskar Rao, Y.J. and Dayal, A.M. (2005) Picrobasalt and lamprophyre dyke swarm of Bakhatgarh-Phulmal area, Chhota Udaipur alkaline Complex, Deccan Igneous Complex. Indian Jour. Geochem., v.20, pp.191–212.Google Scholar
- Ray, Ranjini., Shukla, Anil D., Sheth, Hetu C., Ray, Jyotiranjan S., Duraiswami, Raymond A., Vanderkluysen, Loyc., Rautela, Chandramohan S. and Mallik, Jyotirmoy. (2008) Highly heterogeneous Precambrian basement under the central Deccan Traps, India: Direct evidence from xenoliths in dykes. Gondwana Res., v.13, pp.375–385.CrossRefGoogle Scholar
- Sheth, H. C., R. A. Duncan, D. Chandrasekharam. and J. J. Mahoney. (1997) Deccan Trap dioritic gabbros from the Satpura-Tapti region, Curr. Sci., v.72, pp.755–757.Google Scholar
- Sun, S.S. and McDonough, W.F. (1989) Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes. In: Saunders, A.D., Norry, M.J. (Eds.), Magmatism in Ocean Basins. Geol. Soc. Lond. Spec. Publ., v. 42, pp.313–345.Google Scholar
- Turner, S., Arnaud, N., Liu, J., Rogers, N., Hawkesworth, C., Harris, N., Kelley, S., Calsteren, P.V. and Deng, W. (1996) Post-collision, Shoshonitic volcanism on the Tibetan Plateau: implications for convective thinning of the lithosphere and the source of ocean island basalts. Jour. Petrol., v.37 (1), pp.45–71.CrossRefGoogle Scholar
- Venkatesan, T.R., Pande, K. and Gopalan, K. (1993) Did Deccan volcanism predates the Cretaceous/Tertiary transition? Earth Planet. Sci. Lett., v. 119, pp.181–189.Google Scholar