Dolomite Recrystallization Along the Rimbey-Meadowbrook Reef Trend,Western Canada Sedimentary Basin, Alberta, Canada Open Access
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University of Alberta
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Machel, Hans (Earth and Atmospheric Sciences)
- Examining committee member and department
Harris, Nick (Earth and Atmospheric Sciences)
Rostron, Ben (Earth and Atmospheric Sciences)
Department of Earth and Atmospheric Sciences
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Master of Science
- Degree level
Three theoretical alternatives of what can happen to dolomite when it recrystallizes (steady recrystallization, stepwise recrystallization, or no recognizable signs of recrystallization) were tested on Leduc dolomites of the Devonian Rimbey–Meadowbrook reef trend located in Alberta, Canada.
Four textural types of matrix dolomite, R1, R2, R3 and R4, were distinguished based on crystal size distribution and crystal geometry.
Stabilization from initially formed replacive, metastable dolomite to well-ordered, nearly stoichiometric, and stable dolomite in the reef trend likely took place within a very short time after initial formation, analogous to experimental results in which initially formed metastable (proto-) dolomite recrystallizes via Ostwald's step rule very soon after the initial calcite replacement. However this process is not recognizable in these ancient dolomites. Rather, initial dolomitization with ensuing recrystallization via Ostwald's step rule appear as one process.
Fine crystalline matrix dolomite R1 is interpreted as the 'least-altered' dolomite phase that is geochemically and petrographically the closest to the initial replacive dolomite. The fluids responsible for initial dolomitization and early recrystallization appear to be normal to near-normal marine waters. Dolomitization with ensuing early recrystallization likely occurred during Late Devonian to Early Carboniferous times.
At least some medium crystalline matrix dolomite R2 and coarsely crystalline porous R3 are interpreted to have formed by further recrystallization of a microcrystalline R1 precursor at deeper burial by warmer connate formation fluids. Mixing of dense brines of the Cooking Lake aquifer and meteoric waters of the Lower Mannville aquifer significantly affected the region north from township 44, causing depletion of δ18O values and enrichment in δ13C, 87Sr/86Sr, trace elements and REE compositions.
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