Preprints
https://doi.org/10.5194/hess-2016-372
https://doi.org/10.5194/hess-2016-372
 
17 Aug 2016
17 Aug 2016
Status: this preprint was under review for the journal HESS but the revision was not accepted.

Dissolution and precipitation of fractures in soluble rock

Georg Kaufmann1, Franci Gabrovšek2, and Douchko Romanov1 Georg Kaufmann et al.
  • 1Freie Universität Berlin, Institut für Geologische Wissenschaften, Malteserstr. 74-100, Haus D, 12249 Berlin, Germany
  • 2Karst Research Institute ZRC SAZU, Postojna, Slovenia

Abstract. Soluble rocks such as limestone, anhydrite, and gypsum are characterised by their large secondary permeability, which results from the interaction of water circulating through the rock and dissolving the soluble fracture walls. This highly selective dissolution process enlarges the fractures to voids and eventually cavities, which then carry the majority of flow through an aquifer along preferential flow paths.

We employ a numerical model describing the evolution of secondary porosity in a soluble rock to study the evolution of isolated fractures in different rock types. Our main focus is three-fold: The identification of shallow versus deep flow paths and their evolution for different rock types; the effect of precipitation of the dissolved material in the fracture; and finally the complication of fracture enlargement in fractures composed of several different soluble materials.

Our results show that the evolution of fractures composed of limestone and gypsum is comparable, but the evolution time scale is drastically different. For anhydrite, owing to its difference in the kinetical rate law describing the removal of soluble rock, when compared to limestone and anhydrite, the evolution is even faster.

Precipitation of the dissolved rock due to changes in the hydrochemical conditions can clog fractures fairly fast, thus changing the pattern of preferential pathways in the soluble aquifer, especially with depth.

Finally, limestone fracture coated with gypsum, as frequently observed in caves, will result in a substantial increase in fracture enlargement with time, thus giving these fractures a hydraulic advantage over pure limestone fractures in their competition for capturing flow.

Georg Kaufmann et al.

 
Status: closed
Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Georg Kaufmann et al.

Georg Kaufmann et al.

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