Imprint of metamorphic dehydration reactions subsequent to amphibolitization of mafic granulite from Eastern part of Chotanagpur Granite Gneiss Complex (CGGC), India.

Understanding the significance of the Indian Shield in the reconstruction of tectonic plate amalgamation in geological history requires an analysis of the evolution of the Chotanagpur Granite Gneiss Complex (CGGC), which is regarded as a component of the Rodinia supercontinent. The major lithology of the CGGC is felsic orthogneiss, which contains enclaves of mafic granulites, metapellites, and calc-silicates. The present study focuses on the mafic enclaves hosted within the felsic orthogneiss located in the Bero-Saltora area of the eastern part of CGGC. The rocks comprise of orthopyroxene (Opx), clinopyroxene (Cpx₁) and plagioclase (Pl₁) representing the high-grade granulite facies assemblage and variable amount of amphibole. The amphibole is found to replace the earlier minerals suggested by their occurrence as relict within this phase. The rock shows occurrence of a second generation clinopyroxene (Cpx₂) and plagioclase (Pl₂) developed as symplectite at a high angle to the amphibole's grain boundary. This feature suggests that the rock witnessed a metamorphic dehydration reaction post to the hydration event that formed amphibole in the anhydrous rock. Rarely occurring and locally developed, the symplectite texture indicates that the majority of the rock did not record the conditions under which this assemblage formed. The reaction sequences after stabilization of granulite facies assemblage (Opx+Cpx₁+Pl₁) can be drawn as Opx + Cpx₁ + Pl₁ → Amp, followed by Amp → Cpx₂ +Pl₂. Previous research from this region has modeled the granulite facies event and the ensuing hydration; however, despite the fact that similar symplectite assemblages have been documented, to our knowledge no study has studied the detailed petrological significance of the texture from the studied area. In this study, we will focus on the petrological significance and their connection to the geological evolutionary history of CGGC using detailed petrography and thermodynamic modeling.