Diagenetic systems

Like the climate system described in Chapter 7, this diagenetic system consists of a chain of identical reservoirs that are coupled only to adjacent reservoirs. Elements of the sleq array are nonzero close to the diagonal only. Unnecessary work can be avoided and computational speed increased by limiting the calculation to the nonzero elements. The climate system, however, has only one dependent variable, temperature, to be calculated in each reservoir. The band of nonzero elements in the sleq array is only three elements wide, corresponding to the connection between temperatures in the reservoir being calculated and in the two adjacent reservoirs. The diagenetic system here contains two dependent variables, total dissolved carbon and calcium ions, in each reservoir. The species are coupled to one another in each reservoir by carbonate dissolution and its dependence on the saturation state. They also are coupled by diffusion to their own concentrations in adjacent reservoirs. The method of solution that I shall develop in this section can be applied to any number of interacting species in a one-dimensional chain of identical reservoirs. 

Figure 7.43. Predicted reaction path for the meteoric diagenetic system of the Floridan aquifer. These reaction path calculations agree reasonably well with observations, as shown by variousl symbols. Reaction path calculations of this nature can be applied to other modern meteoric diagenetic systems, and perhaps, with modifications to ancient systems now removed from original meteoric water. (After Plummer et al., 1983.)...

Lohmann K.C. (1988) Geochemical patterns of meteoric diagenetic systems and their application to paleokarst. In Paleokarst (eds. P.W. Choquette and N.P. James), pp. 58-80. Springer Verlag, New York. 

Crossey LJ (1985) The origin and role of water-soluble organic compounds in clastic diagenetic systems. PhD Dissertation, University of Wyoming, Laramie, WY, 134 pp Dionex Corp (1979) Ion chromatograph 10, ion chromatograph 14. Operation and maintenance manual. Sunnyvale, CA, 150 pp... 

As the sandstone/shale system exits the zone of intermediate burial and enters the zone of deep burial (>130°C), the organic acids have been decarboxylated and the alkalinity of the pore waters is again dominated by HCOi . Siebert (1985) has suggested that the thermal (or abiotic) reduction of sulfate by hydrocarbons begins at approximately 140 °C and ends at 210 °C, and that the chemical evolution of many deeply buried and relatively exotic reservoir fluids can be explained by the reduction of sulfate by hydrocarbons and the reaction of the resulting hydrogen sulfide with other minerals. This mechanism is outlined in the seven equations in Table 4. Reactions (l)-(5) in Table 4 show that the reduction of sulfate to H2S and the oxidation of hydrocarbons to CO2 in the presence of iron can be an important source of protons in deeply buried diagenetic systems. 

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