QUANTITATIVE EVALUATION OF COMPOSITIONAL CHARACTERISTICS OF ALKALINE COMPLEXES OF KORAPUT AND KHARIAR, ORISSA - A NUMERICAL APPROACH

摘要

The alkaline intrusive complexes of Koraput and Khariar in Orissa have been compared through numerical analyses of their major-element compositional data. The alkalinity of the two complexes are compared quantitatively. Khariar complex has feeble agpaitic stamp whereas the Koraput suite is nonagpaitic. Correlation matrices for major-element oxides of both the two plutons signify a history of fraclionation dominated by mafic silicate phases. Correlation patterns between the compositional variables in the two complexes are also presented graphically. The correlation behaviour of some oxide pairs is found to be controlled by the scale of compositional domains as observed in subsets within the total data structure. It also appears that finer domain size in the scale of mineral lattices may control the correlation behaviour of the major elements. The spread of data for individual component (major-element oxide) in general shows a curvilinear inverse relation to its mean value Weaker element correlation observed in the syenites of both the complexes reflects limited control of fractionation process in these domains being close to relevant system-minimum. Khariar complex does not bear any distinct imprint of postmagmatic chemical disorder. Present quantitative study reveals distinguishing magma chemistry and crystallisation behaviour of the two alkaline complexes manifesting independent magmatic impulses.