On the Space-Time Context of Magmatism in the Chhota Udaipur Alkaline-Carbonatite Sub-Province within the Deccan Large Igneous Province, India

The Deccan Large Igneous Province (DLIP) represents one of Earth’s most extensive continental flood basaltic events and is widely interpreted to have formed during a geologically short interval near the Cretaceous–Paleogene boundary. Within this framework, the Chhota Udaipur Alkaline-Carbonatite Sub-Province (CUACS), located in the lower Narmada rift zone, has yielded a wide range of radiometric ages, leading to suggestions of prolonged or episodic magmatism. This study integrates detailed field relationships, petrography, geochemistry, structural analysis, geophysical constraints, and critically evaluated geochronological data to reassess the spatial and temporal context of CUACS magmatism within the DLIP. The CUACS comprises diverse tholeiitic, transitional, and alkaline rock suites intruding Precambrian basement, Cretaceous sediments, and Deccan trap basaltic lava flows. Despite lithological diversity, geological relationships show no systematic cross-cutting or temporal separation among intrusive phases. Geochemical signatures indicate derivation from a common OIB-type enriched mantle source modified by crustal contamination. When evaluated in light of high-precision U–Pb and 40Ar/39Ar constraints on Deccan magmatism, the CUACS does not preserve evidence for distinct, long-lived magmatic pulses. Instead, the apparent age scatter largely reflects analytical and sampling errors. The results support a model in which CUACS magmatism is broadly coeval with the main Deccan eruptive phase, indicating short-duration magmatism for the DLIP.