CPCL Research Update: New JSR Paper on the “Induction Period” in Dolomitization

4 minutes ago
2 min read

Dolomitization is often described as a stepwise replacement of CaCO₃ via dissolution–precipitation: Ca-carbonate reactants are first replaced by a metastable very-high-magnesium calcite (VHMC), which is then replaced by ordered, stoichiometric dolomite. A persistent observation in laboratory experiments is a long apparent “induction period,” where no reaction products are detected by powder X-ray diffraction (XRD).

In a new paper in the Journal of Sedimentary Research, we re-examine the induction period using hundreds of high-temperature dolomitization experiments combining fluid-elemental geochemistry, powder XRD, SEM imaging, and in situ SEM-EDS.

What we found

Fluid chemistry changes immediately after the onset of experimental conditions: Mg/Ca decreases and Sr/Ca increases until most CaCO₃ reactants are consumed indicating replacement of calcite by VHMC (Fig. 1a).
SEM and SEM-EDS detect VHMC early, with VHMC crystals appearing on calcite reactants hours before VHMC becomes detectable by XRD (Fig. 1b-d).

Figure 1 (a) Fluid elemental chemistry and XRD defined mineralogy for experiments at 190C. (b) SEM micrograph of products after 7 hours showing early crystals nucleating on calcite reactant. (c-d) EDS elemental maps showing new crystals are Mg-rich. (Figure modified after Martin & Kaczmarek 2025)

Taken together, the data suggest that VHMC nucleation and growth are not strongly inhibited during the early reaction. Instead, apparent induction represents instrument detection limits and slow, size dependent crystal growth.

What it means

These ﬁndings challenge the conventional interpretation that low replacement rates are caused by kinetically inhibited nucleation, which is often cited to explain the absence of dolomite in modern settings. Rather, the scarcity of dolomite in modern settings can more likely be attributed to VHMC slow, size-dependent growth, or suggest that modern timing and/or conditions are not conducive to platform-scale dolomitization.

Paper link: https://doi.org/10.2110/jsr.2025.048

Citation: Martin, A. S., & Kaczmarek, S. E. (2025). Dolomitization kinetics during induction: Fluid geochemistry and mineralogical evidence for early nucleation. Journal of Sedimentary Research, 95(5), 1017–1029. https://doi.org/10.2110/jsr.2025.048