Rhombic calcite microcrystals as a textural proxy for meteoric diagenesis

Area of Science:

• Geology
• Sedimentology
• Mineralogy

Background:

• Phanerozoic limestones contain diagenetic calcite microcrystals formed during sediment stabilization.
• Laboratory experiments link calcite crystal morphology to diagenetic conditions (e.g., impurity levels, supersaturation).
• Previous studies suggest rhombic calcite forms in meteoric settings, while non-rhombic forms occur in marine settings.

Purpose of the Study:

• To test the hypothesis that rhombic calcite microcrystals exclusively form in meteoric diagenetic environments.
• To establish calcite microcrystal morphology as a reliable indicator of diagenetic conditions.

Main Methods:

• Analysis of textural and geochemical data from Phanerozoic limestones.
• Comparison of microcrystal morphology with petrographic and geochemical evidence (δ13C, δ18O, trace elements).

Main Results:

• Phanerozoic limestones with rhombic calcite microcrystals predominantly show petrographic and geochemical signatures of meteoric diagenesis.
• Non-rhombic calcite microcrystals are consistently associated with marine burial diagenetic conditions.
• A strong correlation exists between calcite microcrystal form and inferred diagenetic environment.

Conclusions:

• Rhombic calcite microcrystals are exclusive indicators of meteoric diagenesis.
• Calcite microcrystal morphology serves as a valuable textural proxy for reconstructing past diagenetic environments.
• This research clarifies the formation conditions of diverse calcite microcrystal textures in limestones.