PHOSPHORITE FROM THE UPPER CONTINENTAL-SLOPE OFF KACHCHH, NORTHWEST COAST OF INDIA

Flat slabs and irregular lumps (1 to 3 cm) of brown, grey, black phosp horites and creamy white limestone (2 to 4 cm) were recovered from 473 and 501 m depths from the upper continental slope off Kachchh. Phosph orites contain phosphatised skeletal fragments of shallow water origin , calcitic patches and phosphatised black peloids set in dark brownish microsphorite. Limestone contains fragments of foraminifera set in mi crite. Carbonate fluorapatite, carbonate hydroxylapatite, ankerite, ca lcite in phosphorites and high magnesium calcite in limestone are the major minerals. Electron microprobe studies indicate the presence of C a, P, Mg, Si, Al, K, Fe, S and Ti in phosphorites. P2O5 content of pho sphorites and limestone are 29.42% and 11.76% respectively. It is sugg ested that the phosphatization is an;early diagenetic process took pla ce in shallow wa ter condition most likely du ring the Quaternary peri od. Subsequently, tectonic changes brought them to the present site an d thus occurring as relict phosphorites.