oa Quantitative appraisal of Heliborne and ground-based time domain electromagnetic surveys for uranium exploration – A case study form Rajasthan, India.

Uranium deposits are known to occur in soda-metasomatised rocks and metasediments at several places in the world constituting 18% of the world’s uranium production. Uraniferous metasomatites/albitites are identified at several locations along the 320 km long albitite zone in the environs of North and South Delhi Fold Belts of Rajasthan, India. A multi disciplinary geoscientific approach followed over the last few decades, led to the discovery of a uranium deposit along the albitite line. Fracture controlled uranium mineralisation is associated with weak to moderate albitisation and pyroxenisation of metasediments, as well as with metallic sulphides and carbonaceous phyllites. Mineralisation is mainly in the form of uraninite associated with copper, molybdenum and sulphides. The low resistivity of the fractures associated with metallic minerals produces a significant contrast with the host rock, which can be located with electromagnetic methods. Highresolution heliborne geophysical surveys were conducted to identify deposits in the albitite zone. This paper demonstrates the results of heliborne and ground follow-up geophysical surveys to prioritise targets for uranium exploration.

Analysis and integrated interpretation of the heliborne high-resolution multiparameter magnetic, transient electromagnetic (VTEM) and gamma ray spectrometric surveys conducted in Archaean–Proterozoic metallogenic province of North Delhi Fold Belt, Rajasthan has delineated several targets for uranium exploration. A ground based Time Domain Electromagnetic survey employing Geonics make EM37 system were conducted over one of the target area. Interpreted results from ground data correlate well with the spatial locations of the EM conductors delineated from heliborne surveys. Modelling of both heliborne and ground based EM data revealed the presence of subsurface conducting bodies with comparable model parameters. Plate models generated from both the data sets provided useful input to ongoing exploration programme.