Siwana Ring Complex, Western Rajasthan: A Potential REE Hub

Rare earths (RE) with ever-increasing demand and with a global extensive resource of 120 million tonnes, play an important role in the green energy domain and advanced and latest technologies. Ever-increasing demand pushes for intense exploration activities to establish sizeable RE resources, known to be hosted in carbonatites, alkaline rocks, and placer deposits. India’s RE reserves, mostly from Indian coastal domains are 6.9 million tonnes. Geological exploration and research have been focused on suitable geological domains including carbonatites and alkaline rocks (Rare earth Investing news: 2022). Neoproterozoic bimodal, volcano-plutonic, well-preserved collapsed caldera, Siwana Ring Complex (SRC), Barmer district, Western Rajasthan, India is a part of the third largest felsic Igneous Province called Malani Igneous Suite, in Trans Aravalli Block. It is associated with bimodal volcanism with peralkaline granite ring dyke and intruded by multi-phase granitic activity. Siwana caldera is structurally controlled by NE-SW, E-W, and NW–SE faults and fractures. Caldera margins, central caldera facies, and young felsic intrusive rocks with peralkaline characteristics hosting REE-U-Nb-Ag mineralization. Caldera margins have been widely explored and sizeable REE reserves have been established associated with microgranites, felsites, and tuffs. SRC is unique for having HREE-rich mineralization along with LREE. Few mineralized centers viz, Bhatikhera (Northern margin), Phulan (North northeastern margin), Ramaniya (Southern Margin), and Nal (southwest margin) hosts sizeable resources of average REE from 0.57–0.96% respectively. This paper presents the exploration details of the Siwana Ring Complex, its uniqueness, geological disposition, geochemical considerations, mineralogical attributes, structural limitations, and their bearing on multi-metal mineralization especially on rare earth mineralization.