Rare metal and rare earth rich peralkaline, agpaitic granitoid dykes of Siwana Ring Complex, District Barmer, Rajasthan

Minor radial dykes trending NE–SW, N–S and NW–SE of peralkaline, agpaitic granitoids from Siwana Ring Complex record anomalous concentrations of U, Th, Nb, Sn, Pb, Y, Be, La and Ce. The dykes essentially comprise quartz, acmite, microcline and hematite with minor amounts of aegirine, riebeckite, zircon, rutile, ilmenite and betafite. Anomalous abundances of U, Th, Y and REE are attributed to betafite, acmite and aegirine besides rutile and zircon. A niobium mineral, fersmite (CaNb2O6) is also being reported for the first time from this area. The extreme iron enrichment in some of the dyke samples and their trace elemental abundances suggest that they are extreme differentiates of parental, peralkaline granites.