Fluid compartmentalization of Devonian and Mississippian dolostones, Western Canada Sedimentary Basin: petrologic and geochemical evidence from fracture mineralization

Integrated petrographic, geochemical and fluid inclusion study of fracture mineralization and associated host rock in selected Mississippian and Devonian carbonates extending from southeast Alberta to northwest British Columbia, Canada, aims at quantifying the type and nature of fluids precipitated saddle dolomite and late calcite cement and their origin. Petrographic and isotopic evidence from both the Devonian and Mississippian fracture-filling carbonates indicate the presence of a hydrothermal fluid source. The δ18O isotopic values for the Devonian saddle dolomite (-14.62 to -3.75‰ VPDB; average -11.12 ‰) combined with enriched 87Sr/86Sr isotopic ratios (0.70827 to 0.71599; average 0.71006) and higher homogenization temperatures (Th=74-194.6oC; average 126.8oC) and salinity values (7.7 to 26.6, average 16.2wt% NaCl eq.) show significant differences from the Mississippian saddle dolomite, which is characterized by less negative δ18O isotopic values (-12.53 to -7.82‰ VPDB; average -9.14‰), less radiogenic 87Sr/86Sr isotopic ratios (0.70859 to 0.70943; average 0.70887) and lower homogenization temperatures (Th) and salinity values of fluid inclusions (87.6-214.2oC; average 136.3oC;2.0 to 13.2, average 9.6wt% NaCl eq.). Later fracture- and vug-rimming blocky calcite cement records comparable or slightly lower values of oxygen (-16.31 to -4.08 ‰ VPDB; average -9.76 ‰) and Sr isotopes (0.70784 to 0.709743; average 0.70868) and much lower salinity values (0 to 22.5 wt. % NaCl; average: 2.86 wt. % NaCl) for samples mostly from the Mississippian age group. These results suggest possibly two different hydrothermal episodes related to early (Antler) and late (Laramide) tectonic events that affected the Western Canada Sedimentary Basin with possible compartmentalization of hydrothermal systems and their associated brines in the basin.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author