The authors compiled a map of all available data on the distribution and metal content of ferromanganese deposits throughout the oceans which revealed only one geographic area where nodules were abundant and consistently rich in copper and nickel. It was an east-west band in the equatorial North Pacific between coordinates 8°00^primeN to 10°00^primeN and 125°00^primeW to 154°00^primeW. Nodular deposits were most abundant at the eastern and western ends of this rectangular province. Inspection of analytical data reveals that they are at least twice as rich in copper and nickel than the world average for nodules. Moreover, metal values suggest east-west axes of maximum values of both copper and nickel (2.5 to 3.0% dry weight of the nodules) at the northe n and southern limits of the province.

In order to explain this unusually rich province, the east-west trends of maximum metal values, and variations in abundance of the nodules, a comprehensive study is underway. In order to quantify the data, many sea-floor parameters were established and each inserted as a viable controlling influence on the distribution and metal content of the deposits. They include gradient of sea-floor, water depth, submarine physiography, topographic grain of seabed, distribution of seamounts, distance from major fracture zones, substrate type, porosity and moisture content of substrate, and age of surficial sediment. Characteristics of the nodules, including average and range of size, percent of sea-floor covered and their concentration, were combined with the preceding measures.

Our study has led to the following conclusions: (1) the geographic limits of nodules rich in copper and nickel reflect the distribution of exposures of Tertiary sediments on the ocean floor. (2) The east-west trend of the province is a function of exposures of Miocene, Oligocene, and Eocene strata. (3) Copper and nickel content of nodules appear to increase with increasing age of substrate, i.e., Eocene strata, and presumably "Eocene" nodules, are characterized by maximum values of these metals (3%). Miocene strata and associated nodules have lower copper and nickel values (2.5%), but contain greater amounts of these metals than other nodular deposits. (4) The regional patterns of major nodule fields are directly related to locations of seamounts and fracture zones. Presumably subsea eathering and explosive submarine volcanism release and disperse seed grains of basalt. Nodules are most abundant in the eastern and western thirds of the enriched zone where submarine volcanoes are common, and along a narrow band which follows the Clarion fracture zone. The central section has appreciably fewer nodules because of a limited number of volcanoes and the Clipperton fracture is a site of rapid sedimentation. (5) "Eocene" nodules represent potential mineable deposits. (6) Further evaluation of this resource should be directed toward definition of Eocene, Oligocene, and Miocene exposures close to sources of basaltic seed grains. (7) Porosity and moisture content of radiolarian deposits are higher than any other ocean sediment and may play a role in upward diffusion of metals w thin the substrate and into nodules. (8) Differential erosion and deposition within the area of Tertiary exposures during the past 55 m.y. may have imposed a secondary pattern of nodular concentration over crests of abyssal hills and dilution by burial in adjacent valleys.

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