Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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Sheeted Dykes in Kandra Ophiolite Complex, Nellore Schist Belt, Andhra Pradesh-Vestiges of Precambrian Oceanic Crust


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1 Petrology Division, Geological Survey of India, Southern Region, Hyderabad - 500068, India
     

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Extensive field and petrological studies carried out in Kandra ophiolite complex (KOC) in the southern part of Nellore schist belt (NSB) revealed the existence of sheeted dykes in Kandra- Kondakuru-Gollapalli section. The sheeted dykes occur in the northern part of the complex and compositionally vary from medium-grained dolerites showing typical sub-ophitic texture to diabase dykes that are extremely fine grained aphanitic to fine-grained cryptocrystalline parallel basic dykes (varying in width from 4 cm to 1.25 m). These dykes show chilled margins on either side with the host dykes into which these are intruded. Veins of oceanic plagiogranite (0.5 × 5 m) are noticed in a major sheeted dyke. Occurrence of oceanic plagiogranite as ovoid / semicircular patches of 6 cm diameter resembling "immiscible droplets" within basic dykes is also noticed. The southern part of the complex is made of a major NW-SE trending cumulus gabbro that grades into olivine gabbronorite in its eastern part. The southern gabbros represent the plutonic component and form the deeper part of the complex. In this paper an attempt has been made to present the field, petrographic and mineral chemistry account of various lithounits that constitute the Kandra ophiolite complex in a succinct manner.

Keywords

Sheeted Dykes, Kandra Ophiolite, Precambrian Oceanic Crust, Nellore Schist Belt, Andhra Pradesh.
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  • AUMENTO, F. (1973) The oceanic crust. International Symposium: Ophiolites in the Earths crust. Moscow Academy of Sciences. U.S.S.R. Abstract vol., pp.65.

  • CRADDOCK, JOHN, P., KENNEDY, BRYAN, C., COOK, AVERY, L., PAWLISCH, MELISSA, S., JOHNSON, STEPHEN, T. and MIKE JACKSON (2008) Anisotropy of magnetic susceptibility studies in Teritary ridge-parallel dykes (Iceland), Teritary margin-normal Aishihih dykes (Yahon) and Proterozoic Kenora-Kabetogama composite dykes (Minnesota and Ontario). Tectonophysics, v.448(1-4), pp.115-124

  • DICKINSON, W.R. (1972) Evidences of plate-tectonic regimes in the rocks record. Amer. Jour. Sci., v.272, pp.551-576. HARPER, GREGORY, D. (1988) Episodic magma chambers and amagmatic extension in the Josephine Ophiolite. Geology, v.16, pp.831-834.

  • WAHABAYASHI, JOHN and DILEK, YILDIRIM (2003) What Constitutes "emplacement" of ophiolite? Mechanisms and relationship to subduction initiation and formation of metamorphic soles. Geol. Soc. Spec. Publ., No.218, pp.427-447

  • KING, W. (1881) The gneisses and transition rocks, and other formations of Nellore portion of the Carnatic. Mem. Geol. Surv. India, No.XVI.

  • LEELANANDAM, C. (1990) The Kandra Volcanics in Andhra Pradesh - Possible Ophiolite? Curr. Sci., v.59, pp.785-788.

  • NAGARAJA RAO, B.K., KATTI, P.M. and ROOP KUMAR, D. (1990) Geology of Kandra Igneous Complex, Nellore district, A.P. Unpub. Prog. Rep. Geol. Surv. India, FS 1989-90.

  • RAO, A.T. (1992) The Kandra Igneous Complex from the Precambrian Nellore schist belt, Andhra Pradesh. Jour. Appl. Geochem., v.6, No.1, pp.1-14.

  • RAO, A.T., CHALAMIAH, K., SRINIVASA RAO, D., DEVAVARMA, D. and DHANANJAYA RAO, E.N. (2004) Dolerites from Kandra Volcanic Region, Nellore schist belt, A.P. Indian Jour. Geol., v.64 No.2, pp.187-195.

  • ROTHERY, D.A. (1983) The base of a sheeted dyke Complex, Oman Ophiolite: Implications for magma chamber at ocean spread axes. Jour. Geol. Soc. London, v.140, No.2 pp.287-296

  • ROY, B.C. (1944) The Nellore mica belt, Geol. Surv. India. Bull. Econ. Geologist, No.11.

  • SESHA SAI, V.V. (2005) Petrographic, petrochemical and mineral chemistry studies of Kandra Igneous Complex, Nellore schist belt, Andhra Pradesh. Rec. Geol. Surv. India v.138, Part-5, pp.229-233

  • SESHA SAI, V.V. (2006) Kandra Ophiolite Complex in Nellore schist belt, Andhra Pradesh-Vestiges of Precambrian oceanic crust Abstract in National Seminar on active and fossil suture zones, Wadia Institute of Himalayan Geology. Abstract vol., pp.113- 117

  • SUBRAMANYAM, P. (1966) Studies on Kandra volcanics of Nellore district, A.P. Seminar on mafic and ultramafic rocks of India, Osmania University, Hyderabad. Abstract vol. pp.45-46.

  • WILSON, R.A.M. (1959) The Geology of Xelos-Trodoos area. Cyprus. Geol. Surv. Dep. Mem. 1.

  • YILDIRIM, DILEK and ROBINSON, P.T. (Eds.) (2003) Ophiolites in Earths history. Geol. Soc. Spec. Publ., No.218

  • YILDIRIM, DILEK and ZULFIQUR, AHMED (2003) Proterozoic ophiolites of Arabian shield and their significance in Precambrian tectonics. Geol. Soc. Spec. Publ., No.218, pp.685-700.


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  • Sheeted Dykes in Kandra Ophiolite Complex, Nellore Schist Belt, Andhra Pradesh-Vestiges of Precambrian Oceanic Crust

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Authors

V. V. Sesha Sai
Petrology Division, Geological Survey of India, Southern Region, Hyderabad - 500068, India

Abstract


Extensive field and petrological studies carried out in Kandra ophiolite complex (KOC) in the southern part of Nellore schist belt (NSB) revealed the existence of sheeted dykes in Kandra- Kondakuru-Gollapalli section. The sheeted dykes occur in the northern part of the complex and compositionally vary from medium-grained dolerites showing typical sub-ophitic texture to diabase dykes that are extremely fine grained aphanitic to fine-grained cryptocrystalline parallel basic dykes (varying in width from 4 cm to 1.25 m). These dykes show chilled margins on either side with the host dykes into which these are intruded. Veins of oceanic plagiogranite (0.5 × 5 m) are noticed in a major sheeted dyke. Occurrence of oceanic plagiogranite as ovoid / semicircular patches of 6 cm diameter resembling "immiscible droplets" within basic dykes is also noticed. The southern part of the complex is made of a major NW-SE trending cumulus gabbro that grades into olivine gabbronorite in its eastern part. The southern gabbros represent the plutonic component and form the deeper part of the complex. In this paper an attempt has been made to present the field, petrographic and mineral chemistry account of various lithounits that constitute the Kandra ophiolite complex in a succinct manner.

Keywords


Sheeted Dykes, Kandra Ophiolite, Precambrian Oceanic Crust, Nellore Schist Belt, Andhra Pradesh.

References