MINERAL SURFACE CONTROLS ON THE DIAGENETIC TRANSPORT OF OXALATE AND ALUMINUM

Abstract

The importance of adsorption is virtually unknown at temperatures of > 25°C. This study indicates that interactions between organic acids and mineral surfaces may control Al transport during clastic diagenesis. Oxalate adsorption onto alumina (γ-Al2O3) was measured as a function of pH at 25° and 60°C in 0.1 M NaCl solutions. The thermodynamic stability of the surface Al-oxalate complex remains relatively constant with increasing temperature. Decreasing grain size amplifies the degree to which mineral surfaces control Al and oxalate concentrations through oxalate adsorption in fluid-rock systems. Therefore, diagenetic phase changes should be focused at discontinuities in mineral grain diameter. Furthermore, this grain size effect can influence aluminosilicate mineral solubilities and, therefore, may play an important role in determining the distribution and transport of Al and organic acid anions in sedimentary basins.