Morphology, geochemical association and genesis of Fe–Mn nodules from the Central Indian Ocean Basin

Abstract Larger nodules are poor in grade and better in Fe, Co and wet contents and suggest their genesis at deeper depth by a hydrogenous method. N/n (size of nodule/nucleus) ratios and nucleus size increase with increasing nodule size, supporting view that smaller and large nodules have been formed otherwise at completely different places. Among nodules of different sizes, only medium sized of 3–6 cm are higher in grade and their exploitation looks to be economical. The smaller nodules are better in grade (Cu + Ni + Co %), Mn and Zn contents.Elemental association and their correlation indicate that Mn is negatively correlated with Fe, Co, Pb, Sr while Fe show negative correlation with Cu, Ni, Zn. Similarly, Cu show negative correlation with Co, Pb, Sr, CaO, Na2O, TiO2 while Ni show negative correlation with Co, Pb, Na2O, TiO2 while Zn show negative correlation with Co, Pb, Sr, CaO, Na2O. Similarly, Mn show Positive correlation with Cu, Ni, Zn; Fe show Positive correlation with Co, Pb, Sr, CaO, Na2O, K2O, TiO2 Which can be possibly sourced from hydrolytic release of terrigenous materials; Cu show Positive correlation with Ni, Zn; Ni show Positive correlation with Zn; Co show Positive correlation with Pb, Sr, CaO, TiO2; Pb show Positive correlation with Sr, CaO; Sr show Positive correlation with CaO, Na2O, P2O5; Al2O3 show Positive correlation with CaO; CaO show Positive correlation with P2O5; Na2O show Positive correlation with K2O, TiO2 Which might be possibly sourced from remobilization of metals in marine sediments and pore water.