An observation of distribution features of cobalt rich manganese deposits

Abstract

Evaluation of seafloor stereo photographs, video data, and large diameter gravity core samples shows a variety of surface features associated with the crusts, nodules, and sediments covering mid Pacific seamounts. A set of deep sea stereo camera and a color video camera mounted on a deep tow vehicle with CTD system was used on the research cruise, of R/V Hakureimaru No. 2 and those data were analysed for the study of the seafloor surface features. The gravity core samples were used for the analysis of the sub-bottom features with the seafloor picture taken by one shot deep sea camera used as a pilot weight of the corer. The results show that many locations have high crust coverage with highly undulating microtopography designatEd. by the quantitative analysis of the seafloor topography from the data of the stereo photographs and the vehicle depth correctEd. by the CTD data. High nodule coverage occur on relatively flat seafloor and the nodule size distribution, which was calculated from the stereo photograph data, varies from uniform to heterogeneous at different locations. Distribution of these deposits along the microtopographic sections show that the seafloor can be divided into nodule dominant zones between zero and three degree slopes, sediment patches zones with up to four degree slopes, and crust dominant zones rich occur on slpes higher than 15 degrees. At the transition zones between four and 15 degree slopes crusts and nodules cooccur in varying percentages. The observations of crust outcrops among sediments and nodules and the crust samples collected from the beneath of the sediment sample by the large diameter gravity corer indicated the presence of shallow buried crusts, which can substantially enhance the resource evaluation of this deposits