Burial dolomitization driven by modified seawater and basal aquifer‐sourced brines: Insights from the Middle and Upper Devonian of the Western Canadian Sedimentary Basin

Abstract

Dolomitization in the Western Canadian Sedimentary Basin has been extensively researched, producing vast geochemical datasets. This provides a unique opportunity to assess the regional sources and flux of dolomitizing fluids on a larger scale than previous studies. A meta‐analysis was conducted on stable isotope, strontium isotope (87Sr/86Sr), fluid inclusion and lithium‐rich formation water data published over 30 years, with new petrographic, X‐ray diffraction, stable isotope and rare‐earth element (REE+Y) data. The Middle to Upper Devonian Swan Hills Formation, Leduc Formation and Wabamun Group contain replacement dolomite (RD) cross‐cut by stylolites, suggesting replacement dolomitization occurred during shallow burial. Stable isotope, REE+Y and 87Sr/86Sr data indicate RD formed from Devonian seawater, then recrystallized during burial. Apart from the Wabamun Group of the Peace River Arch (PRA), saddle dolomite cement (SDC) is more δ18O(PDB) depleted than RD, and cross‐cuts stylolites, suggesting precipitation during deep burial. SDC 87Sr/86Sr data indicate contributions from 87Sr‐rich basinal brines in the West Shale Basin (WSB) and PRA, and authigenic quartz/albite suggests basinal brines interacted with underlying clastic aquifers before ascending faults into carbonate strata. The absence of quartz/albite within dolomites of the East Shale Basin (ESB) suggests dolomitizing fluids only interacted with carbonate strata. We conclude that replacement dolomitization resulted from connate Devonian seawater circulating through aquifers and faults during shallow burial. SDC precipitated during deep burial from basinal brines sourced from basal carbonates (ESB) and clastic aquifers (WSB, PRA). Lithium‐rich formation waters suggest basinal brines originated as residual evapo‐concentrated Middle Devonian seawater that interacted with basal aquifers and ascended faults during the Antler and Laramide Orogenies. These results corroborate those of previous studies but are verified by new integrated analysis of multiple datasets. New insights emphasize the importance of basal aquifers and residual evapo‐concentrated seawater in dolomitization, which is potentially applicable to other regionally dolomitized basins.

Volcanic events‐related hydrothermal dolomitisation and silicification controlled by intra‐cratonic strike‐slip fault systems: Insights from the northern slope of the Tazhong Uplift, Tarim Basin, China

“…Therefore, REE + Y signals preserved in chemically sedimentary rocks such as carbonates and cherts can record REE + Y patterns of the fluids in which they grew. To our knowledge, REE + Y has been used as an effective tool to decipher the nature and origin of fluids for dolomitisation and silicification (e.g., Koeshidayatullah et al., 2020; Qing & Veizer, 1994; Stacey et al., 2020). Recent progress in microbeam techniques, such as laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS), electron probe micro‐analyser (EPMA), and secondary ion mass spectrometry (SIMS), permit more precise in situ analysis of REE + Y variations within single crystals by excluding interferences of other diagenetic components.…”

Regional fault-controlled shallow dolomitization of the Middle Cambrian Cathedral Formation by hydrothermal fluids fluxed through a basal clastic aquifer

“…aquifer (e.g., Martín-Martín et al, 2015;Hollis et al, 2017;Lukoczki et al, 2019;Newport et al, 2020;Stacey et al, 2020). In totality, the results demonstrate the importance of a holistic, multi-scale evaluation of the post-depositional alteration of carbonate sedimentary rocks.…”

Depositional and structural controls on a fault‐related dolostone formation (Maestrat Basin, E Spain)

“…During recent years, numerous examples of fault-related dolostones from outcrops have been used as reservoir analogues to evaluate the spatial controls on the formation and distribution of reservoir and non-reservoir rock textures in three dimensions (e.g. Beckert et al, 2015;Hirani et al, 2018;Hollis et al, 2017;Koehrer et al, 2010;Lapponi et al, 2011;López-Horgue et al, 2010;Martín-Martín et al, 2013, 2018Rustichelli et al, 2017;Stacey et al, 2020;Sharp et al, 2010;Slater & Smith, 2012;Vandeginste et al, 2015;Yao et al, 2020). These studies typically highlight the depositional controls on dolostone distribution, the role of faults as conduits and/or barriers to fluid flow, and the relationship between fracture networks and dolostone geometry.…”

“…g . Beckert et al, 2015; Hirani et al, 2018; Hollis et al, 2017; Koehrer et al, 2010; Lapponi et al, 2011; López‐Horgue et al, 2010; Martín‐Martín et al, 2013, 2018; Rustichelli et al, 2017; Stacey et al, 2020; Sharp et al, 2010; Slater & Smith, 2012; Vandeginste et al, 2015; Yao et al, 2020). These studies typically highlight the depositional controls on dolostone distribution, the role of faults as conduits and/or barriers to fluid flow, and the relationship between fracture networks and dolostone geometry.…”