Chemical composition of manganese nodules from the Northeast Pacific belt

The nodules examined were sampled during the R/V Valdivia cruises VA 04, 05, 09, 13/1, and 18. The majority of these samples was taken from a region extending from 135°w to 155°W and from 5° N to 15°N. In the pelagic area investigated a very fine-grained siliceous ooze to siliceous clay is dominant. Three genetic types have been determined: type A (diagenetic) mainly on slopes or in the vicinity of seamounts; type B (Hydrogenetic) in the center of the basin regions and type C (dia-hydrogenetic) characterized by a vertical dual structure with a smooth top and and a rough gritty bottom separated by a distintive knotted botryoidal equatorial band. Chemical analyses have been performed on dried samples.