Occurrence of Liddicoatite-Bearing LCT Pegmatites in Sirohi Region, Northwest India and their Rare Metal Potentiality

Rare and trace element study of pegmatites around Sibagaon area of Sirohi region, Rajasthan, India revealed that the pegmatites are of rare element class and LCT (Li–Cs–Ta) type. Rare metal concentration in these pegmatites is notably high against crustal abundance, with Li ranging from 1007 to 10785 ppm, Rb from 1285 to 9147 ppm, Cs from 36 to 1142 ppm, Ta from 12 to 386 ppm, Sn from 54.22 to 2283.61 ppm and F from 2724 to 48,275 ppm. Integration of EPMA and LA-ICPMS analyses indicated that the main Li-bearing mineral in pegmatites is lepidolite with Li ranging from 21,599 to 28,178 ppm, which is economically worthwhile to process for Li, followed by elbaite and rare mineral liddicoatite, which has not been reported so far in India. Rare earth element (REE) distribution pattern shows enrichment of LREEs than HREEs, indicating that pegmatites are fractionated and thus causing enrichment of rare metals. This reporting of liddicoatite-bearing LCT pegmatites from Sirohi region with high anomalous values of rare metals can therefore be a good prospect for rare metal exploration in India in the present economic scenario. These pegmatites have indicated a syn-collisional signature and may be related to the accretion of Marwar craton with greater Indian land mass along the Phulad Shear zone.