Аннотация:Abstract The distribution and composition of Mn deposits in the northwest Pacific (15–50°N and 120–160°E) are characterized using a Mn deposits database compiled from our original data, published and unpublished papers, published databases, and other international sources. The results demonstrate a close association with geological settings. Hydrogenetic nodules and crusts formed in areas of erosion or nondeposition on Cretaceous seamounts and plateaus of the Pacific plate, and to a lesser extent on seamounts of remnant arcs of Palaeogene to Neogene ages. The Cretaceous seamount deposits are most enriched in Co, and the plateaus less so, while both show moderate Ni enrichment. Nodules and crusts are rare in enclosed backarc basins, which have not been affected by deep water circulation. A slight early-diagenetic influence is observed in some Pacific basin nodules. By contrast, modern hydrothermal Mn deposits are broadly distributed on active submarine volcanoes and backarc rifts. These hydrothermal Mn deposits consist typically of pure Mn oxide containing negligible levels of metals except for Mg, Ba, K and Li. Similar fossil hydrothermal Mn deposits are observed in places on old basement or within deep cores as geological records of past hydrothermal activity.
