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Anthony J. Park1, Gonca Ozkan1, Peter J. Ortoleva1
(1) Lab. for Computational Geodynamics, Indiana University, Bloomington, IN

Abstract: Computer Simulations of Grain Coating and Particle Nucleation under Closed- and Open-system Conditions

The importance of clay-coating and grain overgrowth are examined for arkosic sandstone-siltsone assemblages using the program WRIS.TEQ. The program is a diagenetisis simulator that can quantify sediment compositional and textural evolution over geological time in response to changing thermal, fluid compositional, pressure and stress conditions. The simulator accounts for the textural and compositional evolution of multimineralic, heterogeneous sediments according to kinetic and thermodynamic reactions between water and minerals, and diffusive and advective mass-transfer of solute. In addition, the model accounts for chemical compaction (pressure solution).

The model demonstrates the importance of competition between diffusive and advective transport for enhancing mm- to cm-scale sediment heterogeneity. Thus, while it shows that fluid flow at the rate of milimeters per year can overcome the significance of diffusive mass-transport, the role of grain coating that can control the local authigenesis has not been tested.

Sequences of clay coating, from chlorite to kaolinite and illite, affects local diagenesis by affecting surface areas available for overgrowth, thus the consumption of ions in the water. Some of the complexities that can arise when all these processes are combined are tested and presented in this study. These results are augmented by tests that examine the nucleating clay morphology in varying chemical and temperature conditions.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana