Uranium Mineralization in Mizoram: Inferences from Geochemistry

Mizoram state is covered by green-capped hilly terrain consisting of sedimentary rocks of Oligocene to Miocene age. The lithology consists of thickly bedded sandstones, shales and mudstones of various colours. Mogak Group consisting of Gneisses, Schists, and Kalibag Granites are exposed in the northern Myanmar, which may be the source region of these uraniferous sediments. River ‘Chimtuipui (Kaldon)” draining from Arakan-Yoma Hill Ranges of Northern Myanmar to Mizoram, may have been the carrier for the Uraniferous sediments. The various primary sedimentary structures characterizing the Surma sediments are indicative of shallow marine to deltaic environment of deposition with a constant south worthy palaeoslope. Several positive indications for such uranium mineralization have been found in the study area around Aizawl, Mizoram. The higher concentration of Radon222 in the soils and vegetables of the neighboring states of northeastern India, such as 0.25 ppm in cereals, 0.44 in fruits, 0.77 ppm in leafs and 2.67 ppm in soils, strongly indicate the possibilities of uranium mineralization. Further, the geochemistry of the sedimentary rocks of the study area reveals relatively higher U content (> 4ppm). Eh/pH range of these rocks suggest a sea water condition under ‘euxinic condition’. The Eh/pH ratio as inferred by the average U/Th ratio of the representative samples of the study area, reveal that the probable mineralization may be Uraninite. Positive indications for uranium mineralization may lead to fruitful result after further detailed studies