9. Large Ion Lithophile Elements and Sr and Pb Isotopic Variation in Volcanic Rocks from the Indian Ocean

  1. J.R. Heirtzler,
  2. H.M. Bolli,
  3. T.A. Davies,
  4. J.B. Saunders and
  5. J.G. Sclater
  1. K.V. Subbarao1,
  2. R. Hekinian2 and
  3. D. Chandrasekharam3

Published Online: 23 MAR 2013

DOI: 10.1029/SP009p0259

Indian Ocean Geology and Biostratigraphy

Indian Ocean Geology and Biostratigraphy

How to Cite

Subbarao, K.V., Hekinian, R. and Chandrasekharam, D. (1977) Large Ion Lithophile Elements and Sr and Pb Isotopic Variation in Volcanic Rocks from the Indian Ocean, in Indian Ocean Geology and Biostratigraphy (eds J.R. Heirtzler, H.M. Bolli, T.A. Davies, J.B. Saunders and J.G. Sclater), American Geophysical Union, Washington, D. C.. doi: 10.1029/SP009p0259

Author Information

  1. 1

    Indian Institute of Technology Powai, Bombay, India

  2. 2

    Centre Oceanologique de Bretagne Brest, France

  3. 3

    Indian Institute of Technology Powai, Bombay, India

Publication History

  1. Published Online: 23 MAR 2013
  2. Published Print: 1 JAN 1977

ISBN Information

Print ISBN: 9780875902081

Online ISBN: 9781118664919

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Summary

The normative mineralogy of relatively unaltered major element analyses of Mid-Indian Oceanic Ridge (MIOR) - including Carlsberg Ridge (CR) display limited variation, and concentrated towards the diop-side apex of the Di-Hy-Ol-Az-Ne tetrahedron, while the Mid-Atlantic Ridge (MAR) and East Pacific Rises (EPR) rocks display greater variation from nepheline normative tholeiites to quartz normative alkali basalts. The MIOR basalts are enriched in Large Ion Lithophile (LIL) elements (K, Rb, Sr, Cs and U) and Sr and Pb isotopes suggesting that the source of MIOR was depleted at a much later time and also to a lesser degree than the sources of MAR and EPR. Chemical and Sr isotopic differences exist between MIOR and CR. The volcanic rocks from aseismic 9O°E Ridge include pyroxene basalts, picritic basalts and oceanic andesites (variation from olivine normative to quartz normative) suggesting wide range of differentiation which appears to be not duplicated in other oceanic ridges. The major element analyses, higher concentrations of LIL elements, and Sr87/Sr86 ratios fairly match with the geochemistry of alkali island basalts. Geochemical differences between various tectonically different regimes including seismic and aseismic ridges and islands in the Indian Ocean may probably suggest the presence of systematic heterogeneities with alkali-poor and alkali-rich zones in the mantle giving rise to a chemically zoned structure.