Neutron activation analysis of noble and platinum group metals in the proterozoic Dalma rocks of Eastern India

The Proterozoic Dalma volcanic belt in the Singhbhum Orogen represents the main zone of axial rifting along which lavas of ultrabasic, basic and acidic compositions, pyroclastics and ashes were extruded spasmodically carrying the mineralizing elements from the subcrustal magmatic chamber. Neutron activation analysis, supported by AAS studies of the metamorphosed volcanic and sedimentary rocks in the Belpahari-Kankrajhor sector (22°37′N, 86°41′E) of the Eastern Dalma belt in the district of Midnapore, West Bengal, India, has revealed the existence of platinum, palladium, silver, gold and iridium at concentrations of 2.1, 3.3, 1.92 ppm, 2.65 and 0.12 ppb respectively. Prior to neutron activation, the noble and platinum group metals have been preconcentrated in lead buttons through fire assay and the activated samples have been studied by gamma-ray spectrometry. The anomaly in the existence of the noble and platinum group metals in the relevant rocks deserves detailed geological and exploratory study.