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      https://www.ias.ac.in/article/fulltext/jess/131/0163

    • Keywords

       

      Eastern Deccan Volcanic Province; cluster analysis; dendrogram patterns; feeder dykes; bulk level of crystallization; ambient temperature.

    • Abstract

       

      Multivariate statistical analysis involving hierarchical clusters was carried out for basaltic samples (and associated units) from Khandwa (21°49'N, 76°21'E). ‘Highly significant’ or ‘significant’ linear correlation coefficient values (r) corresponding to different minerals (namely, olivine, clinopyroxene and plagioclase), denote several oxides (as for example, MgO, FeO, SiO$_2$, Al$_2$O$_3$, Na$_2$O, CaO and TiO$_2$) which were used for construction of dendrograms. Critical analysis of hierarchical patterns revealed that at the outset of magmatic crystallization, heterogeneous (${\sim}$greater symmetry) clusters are present. For the crystallization of the lava flows, the ‘bulk level of crystallization’ (in respect of clinopyroxene and plagioclase) varies from ${\sim}$30 to ${\sim}$60%, whereas their ‘ultimate crystallization’ appears to be quite high (${\sim}$80 to ${\sim}$97%). The bulk crystallization of the lava flows shows a broad control of ambient temperature. The dyke system (feeder dyke and chilled dyke) also shows bulk crystallization pattern similar to that of lava flows. Cluster analyses for basement gabbroic rock suggest that there is a wide compositional spectrum for the accumulate portion, whereas the intercumulus portion is marked by relatively restricted compositions. In general, the present CA (cluster analysis) clearly indicates progressive amalgamation of clusters (and their concomitant fall of symmetry) with advancing differentiation.

      $\bf{Highlights}$

      $\bullet$ Multivariate statistical analysis from a portion of eastern Deccan volcanic province deciphers distinctive nature of crystallization.

      $\bullet$ Cluster patterns indicate distinct ‘bulk level of crystallization’ and ‘ultimate crystallization’ for the lavas.

      $\bullet$ Rapid quenching of dyke rocks only allows them to crystallize up to the bulk level.

      $\bullet$ Ambient temperature controls bulk level of crystallization for the lavas.

    • Author Affiliations

       

      PAYEL DEY1 JYOTISANKAR RAY1 JANISAR M SHEIKH2 SURESH C PATEL2 CHRISTIAN KOEBERL3 AVIPSHA CHAKRABORTY1

      1. Department of Geology, University of Calcutta, 35, B.C. Road, Kolkata 700 019, India.
      2. Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India.
      3. Department of Lithospheric Research, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
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