In the study area of South Acrot district, bearing sills and dolerite dykes are found to have intruded the migmatitic country rocks. A detailed study of these rocks reveals that these basic rocks are related to each other and have undergone moderate differentiation. Petrochemical studies indicate less variability in composition and in their trace-element patterns. The range of Mg ratio (MgO/MgO + FeO + Fe2O3) between 0.35 and 0.46 also confirms this view. Sills are considered to have formed after oiliivine bearing dolerites followed by the two types of dolerite dykes. The parental magma of the rock types is considered to the tholeiitic. The ta value indicates that the crust might have been thinner at the time of emplacement of dykes.
Cite this article:
Nathan and Amer (1990). Geochemistry and petrogenesis of dykes and sills of south arcot district, Tamil Nadu. Journal of Ravishankar University (Part-B: Science), 3(1), pp. 14-20.