Research Highlight

Precipitation in Pores: A Geochemical Frontier

Schematic of pore-size dependence for precipitation reactions. (a) Illustrative flow path through a series of mineral grains within a rock. (b) Rock after precipitation that uniformly coats all grains. The pore throats close fi rst, reducing permeability, but the larger pores are left mostly open. (c) Preferential precipitation in large pores. (The different theories for howprecid) Preferential precipitation in smaller pores. Pore throats will close fi rst, strongly reducing permeability while having a minimal impact on porosity.

Scientific Achievement

  • The effects of porous media on precipitation reactions are shown to be important, but poorly understood.

Significance and Impact

  • Geochemical reactions within rocks and soils occur in pores.  Yet, there is not agreement on how the pores affect the reactions, which limits the ability ro predict reactions in the subsurface.

Research Details

  • The different theories for how precipitation in pores occurs and are reviewed and their significance for macroscopic properties wuch as fluid transport, porosity, and permeability, are evaluated
  • It is demonstrated how X-ray/neutron scattering, combined with computational simulation may allow us to resolve this discrepancy observing geochemical reactions directly within a rock

Schematic of pore-size dependence for precipitation reactions. (a) Illustrative flow path through a series of mineral grains within a rock. (b) Rock after precipitation that uniformly coats all grains. The pore throats close fi rst, reducing permeability, but the larger pores are left mostly open. (c) Preferential precipitation in large pores. (The different theories for howprecid) Preferential precipitation in smaller pores. Pore throats will close fi rst, strongly reducing permeability while having a minimal impact on porosity. Schematic of pore-size dependence for precipitation reactions. (a) Illustrative flow path through a series of mineral grains within a rock. (b) Rock after precipitation that uniformly coats all grains. The pore throats close fi rst, reducing permeability, but the larger pores are left mostly open. (c) Preferential precipitation in large pores. (The different theories for howprecid) Preferential precipitation in smaller pores. Pore throats will close fi rst, strongly reducing permeability while having a minimal impact on porosity. (hi-res image)

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