Syn- and postkinematic cement textures in fractured carbonate rocks: Insights from advanced cathodoluminescence imaging

- SEM-CL imaging reveals hitherto invisible textures in veins in carbonate cement.
- Crack-seal textures and cement bridges abound in fracture calcite and dolomite.
- Some calcite and dolomite fracture textures resemble those in quartz in sandstones.
- Some textures identified in SEM-CL are unique to carbonates.

In calcite and dolomite deposits in fractures, transmitted light and optical cathodoluminescence methods detect crack-seal texture in some fractures, but scanning electron microscope-based cathodoluminescence (SEM-CL) combined with secondary-electron images and element maps, reveals crack-seal and cement growth textures where previous SEM-CL imaging methods found massive or featureless deposits. In a range of fractured carbonate rocks, patterns and textures of calcite and dolomite cements precipitated during and after fracture growth resemble complex accumulation patterns found in quartz in sandstone fractures, suggesting that some apparent differences between carbonate mineral and quartz deposits in fractures reflect the limits of previous imaging methods. Advances in delineating textures in widespread carbonate mineral deposits in fractures provide evidence for growth and occlusion of fracture porosity.