Thermochemical sulphate reduction in the Upper Devonian Cairn Formation of the Fairholme carbonate complex (South-West Alberta, Canadian Rockies): evidence from fluid inclusions and isotopic data

Vandeginste, V., Swennen, R., Gleeson, S.A., Ellam, R.M., Osadetz, K. and Roure, F. (2008) Thermochemical sulphate reduction in the Upper Devonian Cairn Formation of the Fairholme carbonate complex (South-West Alberta, Canadian Rockies): evidence from fluid inclusions and isotopic data. Sedimentology, 56(2), pp. 439-460. (doi: 10.1111/j.1365-3091.2008.00978.x)

Abstract

The Fairholme carbonate complex is part of the extensively dolomitized Upper Devonian carbonate reefs in west-central Alberta. The studied formations contain moulds (up to 10cm in diameter), which are filled partially with (saddle) dolomite, quartz and calcite cements. These cements precipitated from a mixture of brines that acquired high salinity by dissolution of halite and brines derived from evaporated sea water. The fluids were warm (homogenization temperature of primary fluid inclusions of 76 to 200°C) and saline (20 to 25 wt% NaCl equivalent) and testify to thermochemical sulphate reduction proceses. The latter is deduced from S in solid inclusions. CO₂ and H₂S in volatile-rich aqueous inclusions and depleted δ¹³C values down to -26‰ Vienna Pee Dee Belemnite. High ⁸⁷Sr/⁸⁶Sr values (0.7094 to 0.7110)of the cements also indicate interaction of the fluids with siliciclastic sequences. The thermochemical sulphate reduction-related cements probably formed during early Laramide burial. Another (younger) calcite phase, characterized by depleted δ¹⁸O values (-23.9‰ to -13.9‰ Vienna Pee Dee Belemnite), low Na (27 to 37 p.p.m.) and sr (39 to 150 p.p.m.) concentrations and non-saline (~0 wt% NaCl equivalent) fluid inclusions, is attributed to post-Laramide meteoric water.

• Item Type: Articles
• Keywords: dolomite, fluid inclusions, stable and radiogenic isotopes, thermochemical sulphae reduction, Western Canada Sedimentary Basin
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ellam, Professor Rob
• Authors: Vandeginste, V., Swennen, R., Gleeson, S.A., Ellam, R.M., Osadetz, K., and Roure, F.
• Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Sedimentology
• ISSN: 0037-0746