| Title | Self-accelerating volumetric dolomite-for-calcite replacement: a possible mechanism for high-temperature dolomitization? |
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| Author | Morrow, D W |
| Source | Carbonates and Evaporites vol. 35, issue 2, 33, 2020 p. 1-13, https://doi.org/10.1007/s13146-020-00565-w |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20210052 |
| Publisher | Springer |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf; html |
| Subjects | geochemistry; sedimentology; Nature and Environment; Science and Technology; dolomitization; calcite; dolomites; brine; temperature; evaporation; sea water geochemistry; computer simulations; calcium
geochemistry; bedrock geology; lithology; sedimentary rocks; limestones; fabric analyses; PHREEQC©; Phanerozoic |
| Illustrations | flow diagrams; plots; tables |
| Program | GEM2: Geo-mapping for Energy and Minerals Mackenzie Corridor, Shield to Selwyn |
| Released | 2020 03 07 |
| Abstract | Quantitative calculations with the geochemical program PHREEQC© for the replacement of calcite by dolomite in brine solutions were performed under the condition that total mineral rock volume is
conserved. These simulations, using brine solutions derived from the evaporation of two 'end member' compositions for Phanerozoic seawater, indicate that calcium (Ca2+) molalities in solution do not increase exponentially, but instead exhibit
monotonically decreasing rates of increase. Simulated rates for calcite dolomitization also decrease monotonically. This indicates that replacement of dolomite by calcite under a stricture of rock volume conservation does not cause a rapidly
increasing rate of dolomitization in a self-accelerating manner, but rather is self-limiting. Preservation of sedimentary microfabrics in dolomitized limestones, although consistent with the recently proposed mechanism of dolomite-growth-driven
pressure solution mechanism for volumetric dolomitization, is not definitive, as near-surface meteoric diagenesis of Pleistocene limestones causes similar preservation of microfabrics where aragonitic paleofauna and sediments have been replaced by
calcite and dolomite in open fluid-rock systems. |
| Summary | (Plain Language Summary, not published)
Quantitative calculations with the geochemical program PHREEQC© for the replacement of calcite by dolomite in brine solutions were performed under the
condition that total mineral rock volume is conserved. These simulations, using brine solutions derived from the evaporation of two 'end member' compositions for Phanerozoic seawater, indicate that calcium (Ca2+) molalities in solution do not
increase exponentially, but instead exhibit monotonically decreasing rates of increase. Simulated rates for calcite dolomitization also decrease monotonically. This indicates that replacement of calcite by dolomite under a stricture of rock volume
conservation does not cause a rapidly increasing rate of dolomitization in a self-accelerating manner, but rather is self-limiting. Preservation of sedimentary microfabrics in dolomitized limestones, although consistent with the recently proposed
mechanism of dolomite-growth-driven pressure solution mechanism for volumetric dolomitization, is not definitive, as near-surface meteoric diagenesis of Pleistocene limestones causes similar preservation of microfabrics where aragonitic paleofauna
and sediments have been replaced by calcite and dolomite in open fluid-rock systems. |
| GEOSCAN ID | 328587 |
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