Correlation between occurrence of manganese nodules and rocks in a part of the Central Indian Ocean Basin

Abstract

The distribution of manganese nodules and rocks in the deep sea is controlled by topography as shown by a study of three topographic highs in the Central Indian Ocean Basin. Topographic highs are dominated by encrustations, slopes and flanks by exposed nodules and abyssal hills by nodules buried under a thick sediment cover. Fresh basalts occur at the summits of the abyssal hills and weathered basalts and pumice occur on the slopes and on the abyssal plains. Bottom photographs show rock outcrops, on the summits, thin sediment cover (<10 cm) on the flanks and thick sediment cover (>10 cm) on the plains. The availability of rock fragments as nuclei and the thin sediment cover enables accretion of more abundant nodules (up to 15.5 kg/m 2) on the slopes and flanks. Six phases of nodule distribution have been identified with respect to the different topographic domains, rock outcrops and sediment thickness.