Geochemistry and tectonic framework of proterozoic mafic metavoicanics of Aravalli-Delhi orogen, NW India

The Aravalli-Delhi orogen of NW India hosts extensive bodies of mafic metavolcanics within the Archaean Banded Gneissic Complex (BGC) basement and in the Proterozoic supracrustal belts of Bhilwara, Aravalli, Jharol and Delhi. All metavolcanics within the supracrustal belts are tholeiites, except for the samples from Basantgarh area of Delhi belt which are calc-alcaline. Certain incompatible trace elements ratios (e.g. Nb/Zr, Y/Zr, Ce/Nd, etc.) show clear distinctions between the various belts as well as within the Delhi metavolcanics. The Bhilwara and Aravalli samples show LREE-enriched patterns, whereas the Delhi samples show a wide variation from slightly depleted through flat to highly fractionated patterns. Comparison of multi-element spidergrams with those of various tectonic setting provides support for the plate tectonic model proposed by Sugden et al. (1990) based on geological and structural data. The tholeiitic metavolcanics of the Bhilwara belt erupted along the incipient divergent margin within the Archaean BGC, continent and the basal Aravalli metavolcanics along its rifted western. boundary. The Delhi belt metavolcanics support the evaluation of the Delhi island arc through eastward subduction and emplacement of the Basantgarh-Ajari metavolcanics close to the suture on the western fringe of the arc, and those of the Ambaji-Deri region along back arc spreading zones where protracted rifting led to the development of the Ajabgarh basin and eventual emplacement of gabbro-syenite plutons.