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Isotopic exchange in mineral-fluid systems
1048
D. Submarine Geology and Geophysics
(Quebec) provide a record of sedimentation variability between 1900 and 1979. It is estimated that sedimentation rates varied 28-50% annually in response to inputs of coarse silt and sand during spring freshet events and that between 1914 and 1979 spring and summer sedimentation rates were 60% higher than during fall and winter. It is suggested that the sand percentage parameter used in conjunction with sediment size parameter provides an index of river discharge intensity and that detailed grain-size distributions offer a method for reconstruction of paleodischarges. Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada. (hbf) 87:6868 Ten Haven, H.L., M. Baas, J.W. De Leeuw and P.A. Schenck, 1987. Late Quaternary Mediterranean saprol~is. I. On the origin of organic matter in sapropel $7. Mar. Geol., 75(1-4):137-156. At least twelve sapropels occur in Late Quaternary sediments from the eastern Mediterranean. Organic matter in sapropel $7 is characterized by gas chromatography and gas chromatography-mass spectrometry. Lipids were separated into three classes: (1) free lipids extracted by Soxhlet extraction; (2) residual bound lipids extracted after saponification of the Soxhlet-extracted residue; and (3) residual bound lipids extracted after acid treatment of the saponified residue. Organic matter is of mixed marine terrigenous and bacterial origin; the former predominates. Sapropel $7 formation is probably caused by a combination of stagnation and high productivity, induced by a large input of fresh riverine water, carrying nutrients and terrigenous organic material. Dept. of Chem. and Chem. Engng, Delft Univ. of Tech., De Vries van Heystplantsoen 2, 2628 RZ Delft, Netherlands. 87:6869 Ten Haven, H.L., G.J. De Lange and R.E. McDuff, 1987. Interstitial water studies of Late Quaternary eastern Me(Ihlterram'an sediments with emphasis on early dlagenettc reactions and evaporitic salt influences. Mar. Geol., 75(I-4):119-136. Dept. of Geochem., State Univ. of Utrecht, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
D I 4 0 . S u b m a r i n e hydrology(springs, hydrothermal deposits, etc.) 87:6870 Cole, D.R., M.J. Mottl and Hiroshi Ohmoto, 1987. Isotopic exdwage in m i m ~ u i d systems. II. Oxygen and hydrogen isotopic investigation of
OLR (1987) 34 (12)
the experimental basalt-seawater system. Geochim. cosmochim. Acta, 51(6): 1523-1538. Oxygen and hydrogen isotopic exchange reactions between basalt and seawater at T = 300 ° to 500°C were investigated. In general, depletion of ~sO and enrichment of D in basalts occur at all temperatures, with the magnitudes of change being greater as temperature, time, and to a lesser degree, glass content increases. The trends in isotopic shifts are directly related to changes in the style and intensity of mineralogic alterations in the basalt. The changes in the 6~sO values of basalts and seawater in the experimental systems were observed to follow closely with those expected from a first-order rate law. Application of experimental rate data to natural systems suggests that the oxygen isotope equilibrium between basalt and seawater in the mid-oceanic ridge may take place within ~1000 years at 350°C. Geosci. Group, Chem. Div., Oak Ridge Natl. Lab., Oak Ridge, TN 37831, USA. 87:6871 Fein, J.B. and J.V. Walther, 1987. Calcite solubility in supereritieal CO2-H~O fluids. Geochim. cosmochim. Acta, 51(6):1665-1673. An extraction~luench apparatus was used to measure calcite solubilities in order to determine the solubility behavior as a function of pressure, temperature, and CO2 content. The results indicate that calcite solubilities under these conditions behave similarly to previously investigated calcite solubilities at lower pressures and temperatures. The solubility behavior can be successfully modeled by making the assumption that Ca + + is the dominant calcium species and that the carbon-bearing species are COgq~q~and HCO- 3. Values of the molal Gibbs free energy of CO2(aq ) exhibit a much greater positive departure from ideality than those calculated with modified Redlich-Kwong equations for dilute CO2 aqueous solutions. Dept. of Geol. Sci., Northwestern Univ., Evanston, IL 60201, USA. 87:6872 Hanor, J.S., 1987. Kilometre-scale thermohaline overturn of pore waters in the l.mdsinna Gulf Coast. Nature, Lond., 327(6122):501-503.
Evidence exists for the large-scale convection of seawater through the upper oceanic crust, even at considerable distances from mid-ocean ridges. Interest exists in verifying convective overturn of pore fluid in large sedimentary basins. Fluid convection in sediments of the Gulf Coast has been inferred on the basis of the large volumes of fluid necessary to account for observed diagenetic alteration and thermal anomalies that cannot be explained by
D. Submarine Geology and Geophysics
(Quebec) provide a record of sedimentation variability between 1900 and 1979. It is estimated that sedimentation rates varied 28-50% annually in response to inputs of coarse silt and sand during spring freshet events and that between 1914 and 1979 spring and summer sedimentation rates were 60% higher than during fall and winter. It is suggested that the sand percentage parameter used in conjunction with sediment size parameter provides an index of river discharge intensity and that detailed grain-size distributions offer a method for reconstruction of paleodischarges. Bedford Inst. of Oceanogr., Dartmouth, NS B2Y 4A2, Canada. (hbf) 87:6868 Ten Haven, H.L., M. Baas, J.W. De Leeuw and P.A. Schenck, 1987. Late Quaternary Mediterranean saprol~is. I. On the origin of organic matter in sapropel $7. Mar. Geol., 75(1-4):137-156. At least twelve sapropels occur in Late Quaternary sediments from the eastern Mediterranean. Organic matter in sapropel $7 is characterized by gas chromatography and gas chromatography-mass spectrometry. Lipids were separated into three classes: (1) free lipids extracted by Soxhlet extraction; (2) residual bound lipids extracted after saponification of the Soxhlet-extracted residue; and (3) residual bound lipids extracted after acid treatment of the saponified residue. Organic matter is of mixed marine terrigenous and bacterial origin; the former predominates. Sapropel $7 formation is probably caused by a combination of stagnation and high productivity, induced by a large input of fresh riverine water, carrying nutrients and terrigenous organic material. Dept. of Chem. and Chem. Engng, Delft Univ. of Tech., De Vries van Heystplantsoen 2, 2628 RZ Delft, Netherlands. 87:6869 Ten Haven, H.L., G.J. De Lange and R.E. McDuff, 1987. Interstitial water studies of Late Quaternary eastern Me(Ihlterram'an sediments with emphasis on early dlagenettc reactions and evaporitic salt influences. Mar. Geol., 75(I-4):119-136. Dept. of Geochem., State Univ. of Utrecht, Budapestlaan 4, 3584 CD Utrecht, Netherlands.
D I 4 0 . S u b m a r i n e hydrology(springs, hydrothermal deposits, etc.) 87:6870 Cole, D.R., M.J. Mottl and Hiroshi Ohmoto, 1987. Isotopic exdwage in m i m ~ u i d systems. II. Oxygen and hydrogen isotopic investigation of
OLR (1987) 34 (12)
the experimental basalt-seawater system. Geochim. cosmochim. Acta, 51(6): 1523-1538. Oxygen and hydrogen isotopic exchange reactions between basalt and seawater at T = 300 ° to 500°C were investigated. In general, depletion of ~sO and enrichment of D in basalts occur at all temperatures, with the magnitudes of change being greater as temperature, time, and to a lesser degree, glass content increases. The trends in isotopic shifts are directly related to changes in the style and intensity of mineralogic alterations in the basalt. The changes in the 6~sO values of basalts and seawater in the experimental systems were observed to follow closely with those expected from a first-order rate law. Application of experimental rate data to natural systems suggests that the oxygen isotope equilibrium between basalt and seawater in the mid-oceanic ridge may take place within ~1000 years at 350°C. Geosci. Group, Chem. Div., Oak Ridge Natl. Lab., Oak Ridge, TN 37831, USA. 87:6871 Fein, J.B. and J.V. Walther, 1987. Calcite solubility in supereritieal CO2-H~O fluids. Geochim. cosmochim. Acta, 51(6):1665-1673. An extraction~luench apparatus was used to measure calcite solubilities in order to determine the solubility behavior as a function of pressure, temperature, and CO2 content. The results indicate that calcite solubilities under these conditions behave similarly to previously investigated calcite solubilities at lower pressures and temperatures. The solubility behavior can be successfully modeled by making the assumption that Ca + + is the dominant calcium species and that the carbon-bearing species are COgq~q~and HCO- 3. Values of the molal Gibbs free energy of CO2(aq ) exhibit a much greater positive departure from ideality than those calculated with modified Redlich-Kwong equations for dilute CO2 aqueous solutions. Dept. of Geol. Sci., Northwestern Univ., Evanston, IL 60201, USA. 87:6872 Hanor, J.S., 1987. Kilometre-scale thermohaline overturn of pore waters in the l.mdsinna Gulf Coast. Nature, Lond., 327(6122):501-503.
Evidence exists for the large-scale convection of seawater through the upper oceanic crust, even at considerable distances from mid-ocean ridges. Interest exists in verifying convective overturn of pore fluid in large sedimentary basins. Fluid convection in sediments of the Gulf Coast has been inferred on the basis of the large volumes of fluid necessary to account for observed diagenetic alteration and thermal anomalies that cannot be explained by