Abstract

Author:
Ayan Kumar Sarkara, Soumyadip Chakrabortya, Sadhana M Chatterjeeab* and Kaushik Dasbc

Doi: 10.26480/gsrj.02.2024.71.83

This is an open access article distributed under the Creative Commons Attribution License CC BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited

In NW India, the Phulad granite, characterized by large euhedral K-feldspar megacrysts, occurs along and across the terrane boundary shear zone, named Phulad Shear Zone. Phulad granite is interpreted as being syntectonically emplacement within a ductile transpression regime during the suturing of the Marwar crustal block with the India. However, the origin of these K-feldspar megacrysts in this Phulad granite has not been studied so far, although it is crucial for understanding the tectonics of NW India. This study focuses on detailed microstructural and chemical analyses of the Phulad granite to decipher the origin of the K-feldspar megacrysts.
The Phulad granite exhibits a bimodal grain size distribution with only K-feldspar as megacrysts. Microstructural evidence supports both magmatic and solid-state deformation processes. Detailed microscopic study reveals the presence of igneous precursors and the absence of metamorphic features which collectively support the magmatic origin of K-feldspar megacrysts. Solid-state deformation features are indicative of post-magmatic tectonic events. Chemical analysis shows higher barium content in K-feldspar megacrysts compared to matrix K-feldspar, indicating early crystallization and further supporting the magmatic origin of the K-feldspar megacrysts. This study contributes to understanding the tectonic history of the granite, emphasizing the importance of detailed microstructural analyses in unravelling the complex geological evolution of the region.