Intergrated airborne gammaray spectral and satellite data analysis for U and REE mineralisation - A case sudy from North Sagobandh Area, district Sonbhadra, Uttar Pradesh, India

Airborne gamma ray spectrometric (AGRS) and magnetic (AM) surveys were undertaken between 1986-1987 by Atomic Minerals Division, to locate uranium mineralisation along Son-Narmada rift zone. The imaging and interpretation of gridded AGRS data revealed many areas of anomalous radio elemental concentrations. These areas have been defined by taking thresholds as U ≥ 6 ppm, Th ≥ 24 ppm, K ≥ 2.3% and Total counts ≥ 5000 cps. The AGRS data integration with the satellite data viz., Landsat Multi spectral Scanner (MSS), Thematic Mapper (TM), and IRS LISS II data on different scales indicated the lithostructural controls of uranium mineralisation and also the predominance of the potash metasomatism in the vicinity of the southern Son rift and soda metasomatism further away in the south. Systematic follow up ground checking of the target area located in the North Sagobandh area resulted in delineating the areas of K metasomatism, anatexis and grissenisation as the areas showing ≥ 2.3%K values. The depicted K, Th, and high U/Th values show zones of albitisation and oligoelasisation. The trends of radiometric breaks depicted by total counts distribution patterns defined the tectonostratigraphic boundaries. Besides these 26 radioactive anomalies with grades ranging from eU30/0./012-0.18%, U30x B/r <0.01-0.3% and ThO2 0.005-0.1% having strike length 50-500 meters and outcrop thickness .5-2.5 meters. Ten locations of inland riverine sand places of heavy minerals containing REE bearing minerals i.e. xenotime, monazite, rutile, ilmenite. zircon and traces of columbite-tantalite have been identified by using thorium and mixed source (U+Th) anomaly map. These sand placers have channel lengths of 100 - >500 meters and width of 1-2.5 meters, containing 1.5%-9.04% heavy minerals.