Role of dyke geometry in understanding dyke-emplacement mechanisms and magma-chamber dynamics: A critical appraisal from the Chotanagpur Gneissic Complex, India

Abstract

We present a detailed account of the structural aspects of dykes from the Chotanagpur Gneissic Complex (CGC) of eastern India, in order to understand dyke-emplacement mechanisms and magma-chamber dynamics. The study area comprises two temporally distinct parts of the CGC, namely the Proterozoic CGC and the Gondwana CGC. Dykes of the Gondwana CGC are divided into two types based on their intrusion into either sandstones or basalts. The size distributions of dyke lengths and of thicknesses respectively follow a power-law and an exponential distribution. Power law explains the nonlinear functional relationship between two quantities in which one quantity varies as the power of the other. The essential properties of power-law are that it is scale-invariant and represents the universality of a problem. An exponential distribution explains that a quantity sharply decreases with respect to other quantities over a period of time. We calculate the overpressure conditions for 60 selected dykes using their aspect ratios. Calculated overpressure is utilized to estimate the depth of magma origin, which in turn is used to estimate the magnitude of maximum and minimum principal stresses. Based on this collective information, we propose a conceptual model of dyke emplacement. Consequently, the results have critical implications in understanding magma chamber dynamics.