Structurally-Controlled Hydrothermal Dolomitization

Overview

My Ph.D. research (The University of Manchester, with Dr. Cathy Hollis and Dr. Ernest H. Rutter) focused on fault-controlled hydrothermal dolomite bodies hosted in Middle Cambrian strata of the southern Rocky Mountains, western Canada. These dolomite bodies form where hot, mineral-rich fluids exploit deep fault systems, dissolving and replacing the surrounding limestone and precipitating the distinctive banded “zebra texture” that makes them so recognizable in outcrop and core. Rather than studying this system with a single method, I built a four-part, complementary research program that moves from description to mechanism to timing:

Imaging — shortwave infrared hyperspectral scanning of drill core to rapidly and non-destructively map multiple generations of dolomite growth, revealing compositional zoning invisible to the naked eye.
Mapping — basin-scale structural analysis showing how the intensity and style of zebra-textured dolomite varies systematically with proximity to the controlling fault systems.
Timing — direct U–Pb geochronology of the dolomite itself, showing that this hydrothermal fluid flow was coeval with deposition of the world-famous Burgess Shale lagerstätte — raising the possibility that hydrothermal brine seeps helped support the exceptionally preserved Cambrian ecosystems nearby.
Mechanism — detailed petrographic and geochemical work resolving the coupled dissolution–replacement–deformation–cementation processes that build zebra texture band by band.

This body of work has been recognized with the Harold Reading Medal (Basin Research, most outstanding publication by a graduate student) and the Ramsey Medal (Earth and Planetary Science Letters, most outstanding publication in structural geology & tectonics).

Harold Reading Medal, 2023 Ramsey Medal, 2025 BP Prize, 2022

Methodological Foundation: Experimental Rock Mechanics

Interpreting how zebra texture builds band by band required first understanding how the host limestone itself fractures under stress. Early in my Ph.D., I ran triaxial deformation experiments with Dr. Ernest H. Rutter on Carrara marble and Solnhofen limestone, testing for a debated “hybrid” fracture mode between pure shear and pure extension. That data-rich mechanical framework — published as its own study and awarded the BP Prize for best presentation at the Tectonic Studies Group AGM — became the experimental foundation for the fracture-controlled fluid-flow model behind the 2025 EPSL paper.

Key Figures

Map and schematic cross-section of the southern Rocky Mountains study area showing Cathedral Formation dolomite bodies interfingering with the Burgess Shale Formation, alongside photographs of Burgess Shale fossils including a trilobite, sponge, and comb-jelly. — The study area in the southern Rocky Mountains, western Canada: fault-controlled dolomite bodies (pink) sit directly adjacent to the world-famous Burgess Shale Formation, whose exceptionally preserved fossils (D–F) may have been supported by the same hydrothermal fluid system. From Fig. 1, McCormick et al. (2024), *Communications Earth & Environment*, 5, 318.

Photograph of a banded, zebra-textured dolomite hand sample showing alternating pale and dark grey stripes. — Banded “zebra texture” in hydrothermal dolomite, formed by repeated cycles of replacement dolomite (RD) and later saddle dolomite (SD) cementation along fault-fed fractures. From Fig. 5D, McCormick et al. (2023), *Basin Research*, 35, 2010–2039.

Photomicrograph of Solnhofen limestone showing a blue dye-impregnated tensile fracture with a small shear offset, viewed under plane-polarized light. — Dye-impregnated thin section of experimentally fractured Solnhofen limestone, showing the transitional fracture geometry that motivated the mechanical framework used to interpret fault-fed fluid pathways in the dolomite bodies above. From Fig. 8A, McCormick & Rutter (2022), *Tectonophysics*, 844, 229623.

Selected Publications

McCormick, C.A., Rutter, E.H., Corlett, H., Steele-MacInnis, M., Block Vagle, E., Whitaker, F., Hollis, C. (2025). Zebra textures in fault-controlled, hydrothermal dolomite bodies: coupled mechanisms of replacement, deformation, and cementation. Earth and Planetary Science Letters, 658, 119274.

Ramsey Medal View Paper →

McCormick, C.A., Corlett, H., Roberts, N.M.W., Johnston, P.A., Collom, C.J., Stacey, J., Koeshidayatullah, A., Hollis, C. (2024). U–Pb geochronology reveals that hydrothermal dolomitization was coeval to the deposition of the Burgess Shale lagerstätte. Communications Earth & Environment, 5, 318.

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McCormick, C.A., Corlett, H., Clog, M., Boyce, A.J., Tartèse, R., Steele-MacInnis, M., Hollis, C. (2023). Basin scale evolution of zebra textures in fault-controlled, hydrothermal dolomite bodies: Insights from the Western Canadian Sedimentary Basin. Basin Research, 35, 2010–2039.

Harold Reading Medal View Paper →

McCormick, C.A., Rutter, E.H. (2022). An experimental study of the transition from tensile failure to shear failure in Carrara marble and Solnhofen limestone: Does “hybrid failure” exist? Tectonophysics, 844, 229623.

BP Prize View Paper →

McCormick, C.A., Corlett, H., Stacey, J., Hollis, C., Feng, J., Rivard, B., Omma, J.E. (2021). Shortwave infrared hyperspectral imaging as a novel method to elucidate multi-phase dolomitization, recrystallization, and cementation in carbonate sedimentary rocks. Scientific Reports, 11, 1–16.

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