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Weathering seafloor

Ludden, J. and Thompson, G. (1979) An evaluation of the behavior of rare earth elements during the weathering of seafloor basalts. Earth Planet. Sci. Lett., 43, 85-92. [Pg.279]

The As (arsenic) concentration of seawater is controlled by input of rivers, sedimentation on the seafloor, weathering of the seafloor, exchange between atmosphere and seawater, volcanic gas input, and hydrothermal input. Previous studies on the geochemical cycle of As have not taken into account the hydrothermal flux of As. Therefore, hydrothermal flux of As from back-arc, island arc and midoceanic ridges to ocean is considered below. [Pg.421]

Weathered fragments of continental crust comprise the bulk of marine sediments. These particles are primarily detrital silicates, with clay minerals being the most abmidant mineral type. Clay minerals are transported into the ocean by river runoff, winds, and ice rafting. Some are authigenic, being produced on and in the seafloor as a consequence of volcanic activity, diagenesis and metagenesis. [Pg.351]

Because of the relative scarcity of lithogenous particles and fast seafloor spreading rates, metalliferous sediments are common around the East Pacific Rise and very high densities of manganese nodules are present on the abyssal plains, especially in the Southern Hemisphere. In these locations, the weathering products of volcanic detritus, such as montmorillonite, phillipsite, nontronite, and celadonite, are also found in great abimdance. [Pg.523]

Most of the Mn(IV) oxide minerals listed in table 8.3 occur in weathered continental rocks, and often constitute important manganese ore deposits. However, several of the minerals, notably todorokite, bimessite, vemadite and, perhaps, buserite and asbolane, are major constituents of seafloor hydrothermal crusts near spreading centres and in manganese nodule deposits. [Pg.346]

There are two major carbon cycles on Earth. The two cycles operate in parallel. One cycle is slow and abiotic. Its effects are observed on multimillion-year timescales and are dictated by tectonics and weathering (Berner, 1990). In this cycle, CO2 is released from the mantle to the atmosphere and oceans via vulcanism and seafloor spreading, and removed from the atmosphere and ocean primarily by reaction with silicates to form carbonates in the latter reservoir. Most of the carbonates are subsequently subducted into the mantle, where they are heated, and their carbon is released as CO2 to the atmosphere and ocean, to carry out the cycle again. The chemistry of this cycle is dependent on acid-base reactions, and would operate whether or not there was life on the planet (Kasting et al., 1988). This slow carbon cycle is a critical determinate of the concentration of CO2 in Earth s atmosphere and oceans on timescales of tens and hundreds of milhons of years (Kasting, 1993). [Pg.4052]

Caldeira K. (1995) Long-term control of atmospheric carbon dioxide low-temperature seafloor alteration or terrestrial silicate-rock weathering Am. J. Sci. 295, 1077-1114. [Pg.4327]

Brady, P. V. GIslason, S. R. 1997. Seafloor weathering controls on atmospheric CO2 and global climate. Geochimica et Cosmochimica Acta, 61, 965-973. [Pg.255]

Although less energetically efficient than the oxidation of hydrogen sulphide (Fig. 8.4), the oxidation of metal sulphides could potentially support chemo-synthesis at seafloor massive sulphide deposits long after hydrothermal activity had ceased, even in well-buffered seawater (Eberhard etal., 1995 Juniper Tebo, 1995). Newly formed sulphide deposits are rapidly subjected to oxidation upon contact with ambient seawater, and some show micro-scale weathering features (e.g. etch pits on mineral surfaces Verati etal., 1999),... [Pg.260]


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