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Subduction water

These different sites of hydrothermal and ore-forming activity may have resulted from the mode of subduction of the Pacific Plate. Mariana-type subduction (characterized by a steep angle of subduction and back-arc basin formation Uyeda and Kanamori, 1979) during middle Miocene caused WNW-ESE extension, submarine hydrothermal activity, thick accumulation of bimodal (basaltic and dacitic) volcanic activity (Green tuff) and Kuroko-type formation (Shikazono and Shimizu, 1993). Plio-Pleistocene Chilean-type subduction (shallow-dipping subduction zone, E-W compression Uyeda and Kanamori, 1979) and oblique subduction of the Pacific Plate beneath the North American Plate led to uplift and expansion of land area, subaerial hydrothermal activity accompanied by meteoric water circulation, subaerial andesitic volcanic activity and formation of vein-type deposits. [Pg.4]

Ransom B, Spivack AJ, Kastner M (1995) Stable Cl isotopes in subduction-zone pore waters implications for fluid-rock reactions and the cycling of chlorine. Geology 23 715-718 Reddy CM, Heraty LJ, Holt BD, Sturchio NC, Eglinton XI, Drenzek NJ, Xu L, Lake JL, Maruya KA (2000) Stable chlorine isotopic compositions of aroclors and aroclor- contaminated sediments. Env Sci Tech 34(13) 2866-2870... [Pg.253]

What has happened to the bicarbonate and calcium delivered to the ocean by river runoff As described later, these two ions are removed from seawater by calcareous plankton because a significant fraction of their hard parts are buried in the sediment. In contrast, the only sedimentary way out of the ocean for chloride is as burial in pore waters or precipitation of evaporites. The story with sodium is more complicated— removal also occurs via hydrothermal uptake and cation exchange. Because the major ions are removed from seawater by different pathways, they experience different degrees of retention in seawater and uptake into the sediments. Another level of fractionation occurs when the oceanic crust and its overlying sediments move through the rock cycle as some of the subducted material is remelted in the mantle and some is uplifted onto the continents. [Pg.539]

The oceanic crust is also a sink for seawater as its porosity increases with age because cooling and chemical weathering lead to the continuing development of fractures and fissures. Most of this trapped water is degassed back into ocean when the crust and its overlying sediment undergo subduction. [Pg.546]

Quite a bit of DOC is also injected into the subsurface ocean via isopycnal mixing in which water is transported down to the top of the thermocline. This subduction is associated with the seasonal formation of mode water, which occurs mostly on the... [Pg.642]

A summary of the observed natural chlorine isotope variations is presented in Fig. 2.23. Ransom et al. (1995) gave a natural variation range in chlorine isotope composition of about 15%c with subduction zone pore waters having S Cl values as low as —8%c whereas minerals in which Cl substitutes OH have 5 Cl values as high as 7%c. [Pg.81]

Hydrate Ridge is located 80 km west of Newport, Oregon on the second accretionary ridge of the Cascadia subduction of the Juan de Fuca Plate and the North American Plate. The northern summit is in 600 m of water depth with an area of... [Pg.600]


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See also in sourсe #XX -- [ Pg.178 ]




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