The rate of growth of sandstone-hosted calcite concretions

摘要: Concretion growth within sandstones can be modelled as a three-stage process, comprising solute supply, transport, and surface reaction. Solute supply is not thought to rate determining. R.A. Berner has proposed models for which adapted the complex calcite-water system. His model concretion by diagenetic redistribution, incorporates replenishment of porewaters during dissolution skeletal aragonite, reassessed new solution presented. The also expanded include effects species interconversion transport. relative importance transport surface-reaction assessed calculating times assuming each process act in absence other. In magnesium-free controlled, seawater it controlled. porefluids with intermediate magnesium-calcium ratios, both processes must if are accurately predicted, two being balanced at concretion. easily modified mobile porefluids. have been applied concretions Valtos Sandstone Formation Skye, UK. A 1 m diameter predicted tomore » grow 9.0 Ma stationary porefluids, or 5.7 flowing a{sup {minus}1}.« less