. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 52 Peter A. Rona and Lawrence D. Neuman I2Q*E 150* 180* IW 120* 90* 60* 30*<. * SILVER • GOLD O PLATINUM 120* E 190* ltO* 190* 120* FIG. 2-Map of precious metal deposits of Pacific region. Lithospheric plate boundaries are shown. in the area of the Canadian shield and in eastern South America in the area of the Guianian and Brazilian shields. In the western Pacific, precious metal deposits occur on island arcs (including Ja- pan, the Philippines,
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 52 Peter A. Rona and Lawrence D. Neuman I2Q*E 150* 180* IW 120* 90* 60* 30*<. * SILVER • GOLD O PLATINUM 120* E 190* ltO* 190* 120* FIG. 2-Map of precious metal deposits of Pacific region. Lithospheric plate boundaries are shown. in the area of the Canadian shield and in eastern South America in the area of the Guianian and Brazilian shields. In the western Pacific, precious metal deposits occur on island arcs (including Ja- pan, the Philippines, and Indonesia) situated along convergent plate boundaries. Deposits also occur in eastern Asia and Australia, where they are separated by a gap from active convergent plate boundaries. Precious metal deposits have not been found along those sections of conver- gent plate boundaries where oceanic lithosphere is juxtaposed and island arcs are absent (, the eastern side of the Philippine Sea and the section between New Zealand and Samoa). Base metal deposits—Deposits of base metals exhibit a spatial relation to convergent plate boundaries (Fig. 3). Their distribution is grossly similar to that of precious metal deposits (Fig. 2). In the eastern Pacific, base metal deposits are present along the western margins of North America and South America. In the Peruvian Andes, porphyry copper and vein-type minerali- zation are associated with Neogene silicic volcan- ic rocks (Mitchell, 1973). Additional base metals occur in central and eastern North America in- cluding the area of the Canadian shield. In the western Pacific, base metal deposits are found on island arcs along convergent plate boundaries. Deposits of tin, tungsten, and fluorite with minor bismuth and molybdenum occur in belts of predominantly Mesozoic granites and acidic eruptive rocks along the southern margin of Alaska and the eastern margin of Asia (Mit- chell, 1973). Base metal deposits also occur in eastern Asi
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