2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 112-9
Presentation Time: 10:15 AM

RECRYSTALLIZATION OF DEVONIAN DOLOMITES ALONG THE RIMBEY-MEADOWBROOK REEF TREND, WESTERN CANADA SEDIMENTARY BASIN, ALBERTA, CANADA


KUFLEVSKIY, Sergey, Earth and Atmospheric Sciences, University of Alberta, 1 - 26 Earth Sciences Building, University of Alberta, Edmonton, AB T6G 2E3, Canada, MACHEL, Hans G., Univ Alberta, 1-26 Earth Sciences Bldg, Edmonton, AB T6G 2E3, Canada and HARRIS, Nicholas, Earth and Atmospheric Sciences, University of Alberta, Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G2E3, Canada, kuflevsk@ualberta.ca

The Upper Devonian Cooking Lake and Leduc Formations of the Rimbey–Meadowbrook reef trend located in Central Alberta, Canada have been extensively dolomitized. Three theoretical alternatives of what happened to this dolomite when it started recrystallizing (steady recrystallization, stepwise recrystallization or no visible signs of recrystallization) were tested on grey matrix replacement dolomite as the most abundant type of dolomite along the whole trend with the best thermodynamic drive.

Four textural types of matrix dolomite, R1, R2, R3 and R4, were distinguished based on crystal size distribution and crystal geometry.

Fine crystalline matrix dolomite R1 is 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 of this dolomite are suggested to be normal to near-normal marine waters. Early recrystallization likely occurred during Late Devonian to Early Carboniferous.

Medium crystalline matrix dolomite R2 and coarsely crystalline porous R3 are formed by further alteration of R1 matrix dolomite at deeper burial and/or by warmer fluids (up to 105 oC). Northward decreasing Mn concentrations reveal that such fluids might have entered the reef trend in the southwestern deep region. Mixing of dense brines of the Cooking Lake aquifer and meteoric waters of the Lower Mannville significantly affected area located north from township 44 causing depletion of δ18O values and enrichment in δ13C, 87Sr/86Sr, trace elements and REE compositions.

The stabilization from initial dolomite to stoichiometric dolomite in this reef trend likely resulted from a single early recrystallization and not through stepwise recrystallization, since three different textures of matrix dolomite in the Cooking Lake and Leduc Formations show a similar range of geochemical signatures.

Handouts
  • GSA 2014_K-M-H_Dolomite Recrystallization.pdf (2.5 MB)