Porosity Evolution through Hypersaline Reflux Dolomitization

  1. Bruce Purser,
  2. Maurice Tucker and
  3. Donald Zenger
  1. F. J. Lucia and
  2. R. P. Major

Published Online: 14 APR 2009

DOI: 10.1002/9781444304077.ch18

Dolomites: A Volume in Honour of Dolomieu

Dolomites: A Volume in Honour of Dolomieu

How to Cite

Lucia, F. J. and Major, R. P. (1994) Porosity Evolution through Hypersaline Reflux Dolomitization, in Dolomites: A Volume in Honour of Dolomieu (eds B. Purser, M. Tucker and D. Zenger), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304077.ch18

Author Information

  1. Bureau of Economic Geology, The University of Texas at Austin, Austin, Texas 78713-7508, USA

Publication History

  1. Published Online: 14 APR 2009
  2. Published Print: 25 MAY 1994

ISBN Information

Print ISBN: 9780632037872

Online ISBN: 9781444304077

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Keywords:

  • porosity evolution through hypersaline reflux dolomitization;
  • dolomitized Plio-Pleistocene limestones - uppermost exposures of inclined beds;
  • dolomite and porosity distribution;
  • cathodoluminescence of carbonates at Goto Meer - systematic changes in downdip direction;
  • porosity evolution during dolomitization;
  • porosity and reflux dolomitization, Bonaire;
  • hydrology and geochemistry of dolomitizing fluids;
  • hypersaline-reflux systems and stacked tidal-flat-capped cycles

Summary

Dolomite of the Plio-Pleistocene foreslope carbonate deposits on the island of Bonaire, Netherlands Antilles, has a mean dolomite porosity of 11%, whereas limestone has a mean porosity of 25%, suggesting that dolomitization does not create but reduces porosity. The shallow burial of these young carbonates precludes burial compaction and cementation as a cause for the low-porosity dolomites. The reduced porosity of dolomite relative to limestone indicates that more dolomite was formed than the original amount of carbonate in the limestone would allow. Therefore, carbonate as well as magnesium must have been imported into the system.

Little difference in porosity is observed between dolomitic limestones and adjacent dolomite bodies, suggesting that sufficient carbonate was imported into the system during the replacement phase to offset the increase in porosity due to changes in molar volumes between calcite and dolomite. Dolomite porosity ranges from 25% to 5%, suggesting a pore-filling phase. The dolomite beds are concentrated at the top of the outcrops, with the lowest porosity values at the top and the highest porosity downdip near the change to limestone. Cathodoluminescent zones, Mg/Ca ratios, dolomite unit cell dimensions and strontium content also show systematic changes from updip to downdip. The presence of sulphate crystals included in the dolomite, the geometry of the dolomite bodies and the stable isotopic data are all consistent with the hypothesis that the dolomite bodies and the observed systematic geochemical and porosity changes are in response to downward-flowing hypersaline fluids.