Executive Summary : | Carbonatites are rare and exotic igneous rocks and many of them are associated with silicate rocks in the alkaline complexes. The relationship between the carbonatites and silicate rocks can be explained by a number of competing hypotheses in vogue such as derivation from small-degree partial melting of carbonated peridotite, liquid immiscibility of carbonated silicate magmas, fractional crystallization of carbonated silicate magmas, and involvement of recycled crustal component in carbonatite-silicate rock generation. Two of the Indian carbonatites are associated with the polychronous alkaline complexes such as the (i) Mundwara (64-110 Myr) and Sarnu Dandali (66- 89 Myr) which are spatially associated with the Deccan Large Igneous Province in NW India. Only a limited petrological, geochemical and isotopic information of them is available and their association with silicate rocks in a polychronous tectonic setup provides a unique opportunity to understand their geodynamic implications. The main objectives of the proposed project are to (i) characterize carbonatites and associated silicate rocks from the two alkaline complexes of Mundwara, and Sarnu Dandali using petrological, geochemical and radiogenic (Sr, Nd and Pb) as well as traditional and non-traditional stable isotopic (Li, B, C, O, and Ca) perspective; (ii) constrain timing of emplacement of carbonatites and critical silicate rocks from these alkaline complexes by U-Pb dating of minerals such as baddeleyite, bastnasite, zircon, monazite, and apatite to resolve petrogenetic models and tectonic evolution; (iii) assess the relative role of rare earth elements (REE) bearing mineral phases (calcite, dolomite, ankerite, monazite, bastnasite, apatite, pyrochlore, etc.) in carbonatites to understand their relative role in REE sequestration for understanding evolutionary history of their magmas in the context of multi-stage fractional crystallization; (iv) decipher crystallization conditions, nature of metasomatism, and redox conditions of magma generation with help of P-T estimation from suitable minerals and their pairs from these complexes; (v) investigate the nature, origin and evolution of mantle source regions (lithosphere, asthenosphere or both) of the carbonatites and associated silicate rocks as to infer whether they were derived from a single or different magma sources, to assess genetic links between them and to evaluate the role of recycled sediments, if any, in their source regions; (vi) evaluate whether the magmatic plumbing system has played a key role in the geochemical evolution of these complexes, and (vii) to propose a comprehensive petrogenetic model for the genesis of carbonatites and associated silicate rocks from these two alkaline complexes and understand their genesis vis-à-vis recurrent magmatism and/or tectonothermal episodes. |