Deccan Trap Intrusion: Magma Mixing in the Chakhla-Delakhari Sill, Chhindwara District, Madhya Pradesh

Strong variations exist in compositions of olivine, plagioclase and pyroxenes within individual hand specimens of this differentiated sill. Such intergrain variations and zoning features were studied with the electron microprobe. These compositional variations can be explained by mixing between liquids that have undergone different degrees of differentiation at different parts of the sill. The mixing effect is illustrated with respect to phase equilibria in the anorthite-saturated surface forsterite-fayalitesilica in the system CaAl₂Si₂O₈-Mg₂SiO₄-Pe₂SiO₄-SiO₂. It appears that the mixing of these differentiated liquids has occurred along the surface pl + o1 + Ca-poor px + 1 in the natural multicomponent equivalent of the simple system.