SHRIMP U-Pb zircon geochronology of the carbonatite-hosted REE deposit of Kamthai, Late Cretaceous polychronous Sarnu Dandali alkaline complex, NW India: Links to plume-related metallogeny and CO2 outgassing at the K-Pg boundary

The carbonatite plug at Kamthai in the Late Cretaceous polychronous (66-89 Ma) Sarnu- Dandali alkaline complex (SDAC), NW India, is India's only known carbonatite-hosted rare- earth-element deposit. The SDAC intrudes the Neoproterozoic (similar to 750 Ma) Malani silicic igneous suite in the Aravalli raton. The Kamthai carbonatite is a calcio-carbonatite dominated by calcite along with barite, strontianite, quartz, zircon and REE-bearing minerals. Textural features suggest an open-system exchange of the magma chamber at varying depths of crystallization. REE patterns are smooth and characterized by strong LREE enrichment, as typical of carbonatites. SHRIMP dating of 12 spots on three magmatic zircons from the carbonatite yielded a concordia age of 66.1 +/- 1.4 Ma and an indistinguishable average 206Pb/238U mean age of 68.4 +/- 1.8 Ma. The obtained U-Pb ages unambiguously link the carbonatite emplacement to the Deccan Large Igneous Province, i.e. the Reunion hotspot near the K-Pg (Cretaceous-Paleogene) boundary in the polychronous set-up of the SDAC. These ages are also indistinguishable from the 68.5 3 +/- 0.16 Ma magmatic pulse recorded from the nearby Mundwara polychronous alkaline complex and the 69.7 +/- 0.2 Ma alkaline sills from the Tethyan suture zone in Pakistan, which are regarded to be earliest manifestations of the Reunion hotspot in the Indian sub-continent. Our results in the context of REE mineralization in the Kamthai deposit have also implications with respect to CO2 outgassing, induced by at least four near-synchronous carbonatitic eruptions in NW India, and to triggering the mass extinction near the K-Pg boundary. (c) 2022 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Automated summary

The carbonatite plug at Kamthai is India's only known carbonatite-hosted rare-earth-element deposit, dating back to the Late Cretaceous period. The study reveals the association of the carbonatite intrusion with the Reunion hotspot in the Indian sub-continent, which has significant geological implications.