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

Abstract This study evaluates examples of hydrothermal dolomitization in the Middle Cambrian Cathedral Formation Western Canadian Sedimentary Basin. Kilometer-scale dolomite bodies within carbonate platform are composed replacement (RD), with saddle dolomite-cemented (SDC) breccias occurring along faults. These overlain by Stephen (Burgess Shale equivalent) shale. RD is crosscut low-amplitude stylolites cemented SDC, indicating that occurred at very shallow depths (<1 km) during Cambrian. Clumped isotope data from and SDC indicate dolomitizing fluid temperatures were >230 °C, which demonstrates fluids. Assuming a geothermal gradient 40 °C/km, due to rift-related basin extension, fluids likely convected faults extended ?6 km depth. The negative cerium anomalies seawater was involved earliest phases dolomitization. 84Kr/36Ar 132Xe/36Ar consistent serpentinite-derived fluids, became more dominant later dolomitization/SDC precipitation. elevated 87Sr/86Sr phases, its co-occurrence authigenic quartz albite, reflects interaction K-feldspar underlying Gog Group before ascending regionally dolomitize Formation. In summary, these results demonstrate important role basal clastic aquifer regional-scale circulation Furthermore, presence shale above facilitated build-up pressure final phase dolomitization, leading formation much shallower than previously realized.