Ni-Enrichment and Mass Balance in Sukinda Laterites, Jajpur District, Orissa

Weathering of serpentinite from Sukinda area, Orissa is studied from a series of lateritic profiles to understand the behaviour of nickel concentration at different parts of the regolith column. The area shows development of laterite profile of variable thickness. Fresh parent rock (serpentinite) is not exposed. Petro-chemical studies show that Ni is concentrated within nepouite and kerolite in partially altered serpentinite, whereas it is mainly in goethite and partly in Mn- oxides within saprolite horizon and negligible in top in situ laterite. Volumetrically, Ni-substituted goethite is more significant for exploration than Ni-substituted Mn-oxides. In the absence of fresh parent rock, methods such as normalization of chemical elements and calculation of mass balance relations between density and chemical elements are adopted, based on the mean element content of the profile. Application of these methods with studied samples clearly discriminate the residual and supergene behaviour of Ni in laterite column.