Theory for quartz cementation in structurally deformed sandstones (abs

A comprehensive theory for quartz cementation must account for variations in the abundance and morphologies of cement in undeformed sandstones as well as in fractures of all scales. Our approach toward developing such a theory is to extend existing kinetic models by rigorously simulating the crystal growth anisotropy and nucleation surface area. For our analysis we assume that the rate limiting control on quartz cementation is the crystal precipitation rate (Walderhaug 1994, 1996, 2000). In a strict sense this assumption does not address whether the silica is derived from local diffusion or larger scale fluid advection but instead simply considers that dissolved silica is supplied at a rate that equals or exceeds the rate at which the crystals can precipitate. This assumption is reasonable for quartz cementation in near neutral pH fluids at temperatures in excess of ~80 °C but is not applicable to quartz precipitation in highly supersaturated fluids (e.g., in silcretes, saline-alkaline lakes, or in the presence of biogenic opal). We assessed the predictive accuracy of a kinetic model for quartz cement abundance in undeformed sandstones. The model (Touchstone ™ version 5.0) considers th