Ocean geochemistry

Acid-base equilibria Partly Near-surface studies tend to investigate fresh or moderately saline water, which creates quite different conditions for acid-base equilibria. Studies of ocean geochemistry come closest to approximating deep-well conditions. 

The first time this author stumbled across the new model of ocean geochemistry was 2002 through a review that appeared in Science (Anbar and Knoll 2002). It had a profound impact on my thinking about early evolution many of the things that I had learned in college and always believed about... 

Cutter, G.A. and Cutter, L.S. (2006) Biogeochemistry of arsenic and antimony in the North Pacific Ocean. Geochemistry, Geophysics, Geosystems, 7(5), 12. 

By focusing on a molecular elucidation of key biochemical processes in the marine biogeochemical cycles of elements, marine bioinorganic chemistry should help us understand the subtle and complex interdependence of marine life and ocean geochemistry, and how they have evolved together over the history of the Earth. 

Physical processes associated with hydrothermal plumes may affect their impact upon ocean geochemistry because of the fundamentally different hydrographic controls in the Pacific versus Atlantic Oceans, plume dispersion varies between these two oceans. In the Pacific Ocean, where deep waters are warmer and saltier than overlying water masses, nonbuoyant hydrothermal plumes which have entrained local deep water are typically warmer and more saline at the point of emplacement than that part of the water column into which they intrude (e.g., Lupton et al, 1985). The opposite has been observed in the Atlantic Ocean where deep waters tend to be colder and less saline than the overlying water column. Consequently, for example, the TAG nonbuoyant plume is anomalously cold and fresh when compared to the background waters into which it intrudes, 300-400 m above the seafloor (Speer and Rona, 1989). 

Keir R. S. (1988) On the late Pleistocene ocean geochemistry and circulation. Paleoceanography 3, 413—445. 

Stakes, D.S. and O Neil, Jr. (1982) Mineralogy and stable i.sotopes geochemistry of hydrothermally altered ocean rocks. Earth Planet. Sci. Lett, 57, 285-304. 

Butterfield, V.A., McDuff, R.E., Franklin, J. and Wheat, C.G. (1994) Geochemistry of hydrothermal vent fluids from Middle Valley, Juan de Fuca Ridge. In Mottl, M.J., Davis, E.E., Fi.sher, A.T. and Slack, J.F. (eds.). Proceedings of the Ocean Drilling Program. Sci. Proc., 139, 395-410. 

Chapters 11 and 12 focus on the oceans. The first of these describes the use of U-series nuclides in the modern ocean, where they have been particularly useful during the last decade to study the downward flux of carbon. The second ocean chapter looks at the paleoceanographic uses of U-series nuclides, which include assessment of sedimentation rates, ocean circulation rates, and paleoproductivity. Both of these ocean chapters demonstrate that knowledge of the behavior of the U-series is now sufficiently well developed that their measurement provides useful quantitative information about much more than just the geochemistry of these elements. 

Nozaki Y, Yamada M, Nikaido H (1990) The marine geochemistry of actinium-227 evidence for its migration through sediment pore water. Geophys Res Lett 17 1933-1936 Nozaki Y (1993) Actinium-227 a steady state tracer for the deep-se basin wide circulation and mixing studes. In Deep Ocean Circulation, Physical and Chemical Aspects. Teramoto T (ed) Elsevier p 139-155... 

The geochemistry of marine sediments is a major source of information about the past environment. Of the many measurements that provide such information, those of the U-series nuclides are unusual in that they inform us about the rate and timescales of processes. Oceanic processes such as sedimentation, productivity, and circulation, typically occur on timescales too short to be assessed using parent-daughter isotope systems such as Rb-Sr or Sm-Nd. So the only radioactive clocks that we can turn to are those provided by cosmogenic nuclides (principally or the U-series nuclides. This makes the U-series nuclides powerful allies in the quest to understand the past ocean-climate system and has led to their widespread application over the last decade. 

Cochran JK (1984) The fates of U and Th decay series nuclides in the estuarine environment. In The Estuary as a Filter. Kennedy VS (ed) Academic Press, London, p 179-220 Cochran JK (1992) The oceanic chemistry of the uranium - and thorium - series nuclides. In Uranium-series Disequilibrium Applications to Earth, Marine and Environmental Sciences. Ivanovich M, Harmon RS (eds) Clarendon Press, Oxford, p 334-395 Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cochran JK, Carey AE, Sholkovitz ER, Surprenant LD (1986) The geochemistry of uranium and thorium in coastal marine-sediments and sediment pore waters. Geochim Cosmochim Acta 50 663-680 Corbett DR, Chanton J, Burnett W, Dillon K, Rutkowski C. (1999) Patterns of groundwater discharge into Florida Bay. Linrnol Oceanogr 44 1045-1055... 

Jeffrey LM, Rasby BF, Stevenson B, Hood DW (1964) Lipids of ocean water. In Colombo U, Hobson GD (eds) Advances in organic geochemistry. Pergamon Press, Oxford, pp 175-197... 

Mayer, L.M. 1988. Geochemistry of chromium in the oceans. Pages 173-187 in J.O. Nriagu and E. Nieboer (eds.). Chromium in the Natural and Human Environments. John Wiley, NY. 

Geochemistry of oceanic carbonatites compared with continental carbonatites mantle recycling of oceanic crustal carbonate. Contributions to Mineralogy and Petrology, 142, 520-542. 

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