(NAS Colloquium) Geology, Mineralogy, and Human Welfare (1999) / Chapter Skim
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Oceanic Minerals: Their Origin, Nature of Their Environment, and Significance
Oceanic Minerals: Their Origin, Nature of Their Environment, and Significance
Pages 3380-3387
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From page 3380... ...
Oceanic minerals: Their origin, nature of their environment, and significance MIRIAM KASTNER* Scripps Institution of Oceanography, University of California-San Diego, La Jolla, CA 92093-0212 ABSTRACT The chemical and isotopic compositions of oceanic biogenic and authigenic minerals contain invaluable information on the evolution of seawater, hence on the history of interaction between tectonics, climate, ocean circulation, and the evolution of life.
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From page 3381... ...
The trace element chemistry and isotopic compositions of these skeletal components are the most powerful tools available to unravel the effects of the interplay between tectonic and surficial processes on the chemical history of seawater (i.e., refs. 23-32 and references therein)
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From page 3382... ...
Nevertheless, the stable carbon isotopic composition of organic matter in marine sediments helps to identify periods of high productivity or of high terrestrial organic matter input from enhanced continental weathering. This information is essential for modeling the oceanic C cycle and atmospheric CO2 and O2 fluctuations (i.e., refs.
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From page 3383... ...
Unlike anhydrite, barite is more likely to survive burial and resist diagenesis and dissolution. Examples of Recent Advances in Studies of Oceanic Minerals and Implications for Chemical Paleoceanography and Global Change Changes in ocean chemistry respond to climate-producing variations in the exogenic cycle and are recorded in oceanic minerals, but the record is far from simple and bulk chemical analyses are inadequate for paleoceanographic studies.
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From page 3384... ...
To understand the unique geochemical records stored in oceanic minerals it is necessary to develop an in-depth understanding of biogeochemical processes in the modern oceans and establish new and redundant proxies for the most significant oceanographic processes. To be a reliable monitor, a mineral must inherit the chemical and isotopic composition of seawater at the time of its formation, must retain this signal intact, and remain inert to chemical exchange after burial.
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From page 3385... ...
A comparison between the new sulfate sulfur isotope data and the carbon isotope record of marine carbonates does not reveal the clear systematic coupling between the S and C cycles assumed in the existing major global geochemical cycles models. The new data indicate that changes in pyrite sulfur and organic carbons burial rates did not balance each other over a few to tens of millions of years.
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From page 3386... ...
An important consequence of the vertical sequence of bacterial redox reactions on other authigenic carbonate mineral formation is the continuous mobilization of available reactive Mn2+ and Fez+ by iron-reducing bacteria. This can cause the formation of rhodochrosite, ankerite, and/or siderite, respectively, instead of dolomite, in pore fluids with lowered Mg/Ca (~1-2)
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From page 3387... ...
(1992) in Productivity, Accumulation and Preservation of Organic Matter in Recent and Ancient Sediments, eds.
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