Abstract

The Hirapur-Mardeora phosphorite deposits are found to occur in Bijawar group of Gangau iron formations over the basement of Bundelkhand granite complex in the Archean period. There are four distinct units of phosphorites which include shale-phosphorite, secondary-phosphorite, ironstone-phosphorite and quartz-breccia phosphorite. Chemical analysis of 24 representative samples of these different units was carried out for qualitative and quantitative determination of their major and trace element concentration, geochemical behaviour and inter-element relationship. The study reveals that these elements were precipitated by direct, inorganic, syngenetic, and authigenic processes in the primary phosphorites and by epigenetic, leaching, remobilization and reprecipitation in the cavities, voids, fractures and fissure fillings in the secondary phosphorites during diagenesis. The phosphogenic processes might have taken place during the slight reduction of fairly oxidising conditions under tropical to arid climate in shallow water marine environment of the basin.

 Key words: Hirapur-Mardeora, phosphorite, geochemistry, Chhatarpur and Sagar districts, diagenesis.