Western Pacific

Recently, 27 back-arc deposits have been discovered in the Western Pacific (Ishibashi and Urabe, 1995) (Fig. 2.29). The summary of geologic structure, type of deposits and mineralogy of the back-arc deposits in Western Pacific are given in Table 2.12 (Ishibashi and Urabe, 1995). 

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Deep-sea manganese nodules represent a significant potential mineral resource. Whereas the principal constituent of these deposits is manganese, the primary interest has come from the associated metals that the nodules can also contain (see Ocean rawmaterials). For example, metals can range from 0.01—2.0% nickel, 0.01—2.0% copper, and 0.01—2.25% cobalt (12). Recovery is considered an economic potential in the northwestern equatorial Pacific, and to a lesser degree in the southern and western Pacific and Indian Oceans (13—18). 

In the United States, air and gas drilling techniques are used extensively in parts of the southwest in and around the San Juan Basin, in parts of the Permian Basin, in Arkansas and eastern Oklahoma, in Maryland, Virginia and parts of Tennessee. Internationally, oil and gas drilling operations are carried out with air and gas drilling techniques in parts of the Middle East, North Africa and in the Western Pacific. 

South America to about the date line (180 ). These trade winds also drive near-equatorial surface flow westward as the South Equatorial Current (SEC). This piles up warm surface water in the western Pacific to create a deep warm pool and results in depression of the depth of the thermocline from east to west. The westward flow in the surface SEC is partly compensated by a return flow to the east in the thermocline ( 150m) called the Equatorial Undercurrent (EUC). 

Western Pacific Eastern Asia, Japan, and the Philippines... 

Gamo, T. (1995) Wide variation of chemical characteristic of submarine hydrothermal fluids due to secondary modification processes after high temperature water-rock interaction, a review. In Sakai, H. and Nozaki, Y. (eds.), Biogeochemical Processes and Ocean Flux in the Western Pacific, Terra Sci. Publ., pp. 425-451. 

Ishibashi, J. and Urabe, T. (1995) Hydrotheimal activity related to arc-back arc magmatism in the Western Pacific. In Taylor, B. (ed.), Backarc Basins Tectonics and Magnetism, Plenum Publ, pp. 451—496. 

Miyashiro, A. (1986) Hot regions and the origin of marginal basins on the western Pacific. Tectonophysics, 122, 195-216. 

Tamaki, K. and Honza, E. (1991) Global tectonics and formation of marginal basins Role of the Western Pacific. Episodes, 14, 224-230. 

Hydrothermal mineral occurrences in arc-back-arc systems in the Western Pacific (Ishibashi and Urabe, 1995)... 

We saw in section 2.3.2 that present-day hot spring venting and sulfide-sulfate depositions have been discovered in back-arc basins in the Western Pacific. These intense hydrothermal activities indicate that seawater-volcanic rock interactions are taking place at these environments. 

During the last three decades, many hydrothermal deposits have been discovered at midoceanic ridges, back-arc basins and subaerial active geothermal systems. Characteristic features of back-arc deposits at the western Pacific region (e.g., Okinawa Trough, Izu Ogasawara, North Fiji and Mariana deposits) are very similar to those of Kuroko deposits. 

In 1990s, hydrothermal venting and mineralization were discovered on the sea floor of the back-arc basin, back-arc rift, and island arc surrounding the Japanese Islands as well as other western Pacific regions. 

Vertical profiles and surface concentrations of DDT dissolved in the ocean were measured by Tanabe and Tatsukawa (1983). Water samples for depths down to 5000 m were taken on three cruises of the Ocean Research Institute, University of Tokyo and on a cruise by the University of Fisheries, Tokyo. The cruises were carried out between 1976 and 1981 in the Western Pacific, Eastern Indian and Antarctic oceans. 

Fig. 6.1. pH of surface seawater from the western Pacific Ocean (Skirrow, 1965), as measured in situ during oceanographic cruises (various symbols). Line shows pH predicted by the model for seawater in equilibrium with atmospheric CO2 at a fugacity of 10-3-5. Dashed lines show pH values that result from assuming larger fugacities of 10-33 and... 

Sholkovitz ER, Elderfield H, Szymczak R, Casey K (1999) Island weathering riverine sources of rare earth elements to the western Pacific Ocean. Marine Chem 68 39-57 Skulan JL, Beard BL, Johnson CM (2002) Kinetic and equilibrium Fe isotope fractionation between aqueous Fe(III) and hematite. Geochim Cosmochim Acta 66 2995-3015 Sumner DY (1997) Carbonate precipitation and oxygen stratification in Late Archean seawater as deduced from facies and stratigraphy of the Gamohaan and Frisco Formations, Transvaal Supergroup, South Africa. Am J Sci 297 455-487... 

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