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==Summary diagram==
==Summary diagram==
[[file:predicting-reservoir-system-quality-and-performance_fig9-70.png|thumb|{{figure number|1.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-70.png|thumb|{{figure number|1}}]]
The block diagram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-70.png|Figure 1]] summarizes early diagenetic processes and products that occur in carbonate environments.
The block diagram in [[:file:predicting-reservoir-system-quality-and-performance_fig9-70.png|Figure 1]] summarizes early diagenetic processes and products that occur in carbonate environments.
==Vadose precipitation zone==
==Vadose precipitation zone==
[[file:predicting-reservoir-system-quality-and-performance_fig9-72.png|thumb|{{figure number|3}}. Copyright: Purser, 1978; courtesy Journal of Petroleum Geology.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-72.png|thumb|{{figure number|3}}. Copyright: <ref name=Purser_1978>Purser, B. H., 1978, Early diagenesis and the preservation of porosity in Jurassic limestones: Journal of Petroleum Geology, v. 1, no. 2, p. 83-94</ref>; courtesy Journal of Petroleum Geology.]]
The vadose precipitation zone begins where water in the vadose zone becomes saturated with CaCO<sub>3</sub>. Slight temperature increases or CO<sub>2</sub> degassing causes calcite to precipitate. Cementation is generally minor and reflects pore-water distribution. Meniscus cement precipitates where water clings between grains in a meniscus manner. Pendulous or microstalactitic cement precipitates where water droplets form underneath grains. Cement tends to be very fine equant calcite crystals. If magnesium is present in pore water, then calcite precipitation may be inhibited and aragonite or even dolomite may precipitate.<ref name=ch09r35 />
The vadose precipitation zone begins where water in the vadose zone becomes saturated with CaCO<sub>3</sub>. Slight temperature increases or CO<sub>2</sub> degassing causes calcite to precipitate. Cementation is generally minor and reflects pore-water distribution. Meniscus cement precipitates where water clings between grains in a meniscus manner. Pendulous or microstalactitic cement precipitates where water droplets form underneath grains. Cement tends to be very fine equant calcite crystals. If magnesium is present in pore water, then calcite precipitation may be inhibited and aragonite or even dolomite may precipitate.<ref name=ch09r35 />