Research Projects

The proposed project envisages the delineation of the mafic-ultramafic rocks in the desertic terrain of western Rajasthan in Churu and Nagaur, their geochemical and geochronological characterization. Although, the predominantly felsic volcano-plutonic rocks of the Malani Igneous Suite are known from wester Rajsthan since late 19th Century, the mafic – ultramafic suite was discovered only in 2009. These rocks are suitable candidates for probing the upper mantle composition and crust mantle interaction, in addition to offering a unique opportunity to study ancient ocean floors and represent a distinctive tectonic setting requiring large-scale plate convergence. Mafic-ultramafic rocks in the proposed study area occur either as isolated ground-level or subsurface exposures mainly in open quarry section and dug wells in the Bidasar-Gunpaliya-Chhapar as serpentinized pyroxenite, gabbro-norite, sheeted dykes, etc.. The proposed study area (74⁰12' – 74⁰30' E: 27⁰30' – 27⁰49' N) in the Bidasar region of Churu and Gunpaliya area of Nagaur districts in western Rajasthan, forms a part of the Marwar terrane in the NW Indian Block. It is a largely sand-covered region and comprises minor schist, mafic-ultramafic rocks (referred to as ophiolite sequence) of unknown stratigraphic affinity (Mukhopadhyay and Bhattacharya, 2009). The Ediacaran–Cambrian rocks of Marwar Supergroup occur to the west and south and Mesoproterozoic Delhi Supergroup rocks in the south of the study area (Sinha Roy et al., 1998; Roy and Jakhar, 2002; Talukdar et al., 2021). Preliminary whole-rock geochemical data on a limited number of samples suggests derivation from a tholeiitic to calc-alkaline primary magma and an island arc complex tectonic setting for the mafic-utramafic suite (Khanday et al., 2014) while a harzburgite protolith and a forearc tectonic setting was inferred by Talukdar et al. (2021). These are prelimanary inferences, based on limited sample set and at times, not considering some critical trace elements. The gaps in information and outstanding issues that need attention are: • The areal extent of mafic-ultramafic rocks has not been delineated and petrographic details are not available. The geochemical inferences lack immobile elements (Nb, Ta, Zr, Hf) which are vital in inferring magma generation and tectonic setting. Detailed petrographic and comprehensive geochemical characteristics are needed to substantiate the ‘ophiolite’ setting, and to work out petrogenesis and tectonic setting. • No geochronological information is available so far for this mafic–ultramafic suite, therfore, regional correlation could not be done. • The mafic-ultramafic rocks also occur in the Gunpaliya area, around Sinwla and Sunari to the south of Bidasar. No geological details are available for these rocks so far. • Comprehensive geochemistry and geochronology of this mafic – ultramafic suite of rocks would contribute to an improved understanding the geological evolution of the NW Indian block.